COPYRIGHT The copyright in this manual and its accompanying software are the property of Softbits Consultants Ltd with all rights reserved. Both this manual and the software have been provided pursuant to a License Agreement containing restrictions on use. Softbits Consultants Ltd reserves the right to make changes to this manual or its accompanying software without obligation to notify any person or organisation. No part of this manual may be reproduced, transmitted, transcribed, stored in a retrieval system or translated into any other language in any form or by any means, or disclosed to third parties without the prior written consent of Softbits Consultants Ltd.
WARRANTY Softbits Consultants Ltd or its agents will replace any defective manual, program disks within 90 days of purchase of the product providing that proof of purchase is evident. Neither Softbits Consultants Ltd nor its agents or dealers make any warranty, implied or otherwise, with respect to the software or results generated by the software. This program is intended for use by a qualified engineer to aid the design and analysis of flare systems. The results calculated by this program may not be reliable if the input data has not been appropriately specified or if the program is used without regard to its documented limitations. It is the responsibility of the user to interpret the results generated by this program. Softbits Consultants Ltd shall bear no liability for special, indirect, incidental, consequential, exemplary or punitive damages arising from use of this software. The governing law of this warranty shall be that of England.
ACKNOWLEDGEMENTS Softbits Consultants Ltd would like to thank Mr. John F. Straitz III and the National Airoil Company and GBA Ltd of Slough for assistance with some algorithms within the software. Windows XP, Vista and Windows 7 are registered trademarks of Microsoft Corporation. Copyright Softbits Consultants Ltd, 1989, 1990, 2002, 2006, 2008, 2010, 2013
Table of Contents 1 Introduction.................................................. 1-1 1.1 1.2 1.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4 Program Overview. . . . . . . . . . . . . . . . . . . . . . 1-8 Documentation Overview . . . . . . . . . . . . . . . 1-14
2 Getting Started............................................. 2-1 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8
Offshore Flare Stack Design . . . . . . . . . . . . . . 2-4 Onshore Flare Stack Design . . . . . . . . . . . . . 2-24 Using Shields . . . . . . . . . . . . . . . . . . . . . . . . 2-35 Using Overlays . . . . . . . . . . . . . . . . . . . . . . . 2-45 Case Study . . . . . . . . . . . . . . . . . . . . . . . . . . 2-51 Dynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-59 Gas Dispersion . . . . . . . . . . . . . . . . . . . . . . . 2-64 KO Drum . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-73
3 Interface........................................................ 3-1 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9
Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3 Menu Bar. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-8 Multiple Case Views . . . . . . . . . . . . . . . . . . . 3-11 Tool Bars . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-12 Log Panels . . . . . . . . . . . . . . . . . . . . . . . . . . 3-15 File Dialogs . . . . . . . . . . . . . . . . . . . . . . . . . . 3-16 About View . . . . . . . . . . . . . . . . . . . . . . . . . . 3-21 Radiation Limits View . . . . . . . . . . . . . . . . . . 3-22 Flaresim Update View . . . . . . . . . . . . . . . . . . 3-23
4 General Setup .............................................. 4-1 4.1 4.2
Case Navigator View. . . . . . . . . . . . . . . . . . . . 4-4 Case Summary View. . . . . . . . . . . . . . . . . . . . 4-9 1
4.3 4.4 4.5
Setup Wizard. . . . . . . . . . . . . . . . . . . . . . . . . 4-13 Preferences . . . . . . . . . . . . . . . . . . . . . . . . . . 4-29 Component Management View . . . . . . . . . . . 4-46
5 Fluids ............................................................ 5-1 5.1 5.2
Fluid View . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4 Assist Fluid View . . . . . . . . . . . . . . . . . . . . . . 5-15
6 Environment................................................. 6-1 6.1 6.2
Environment View . . . . . . . . . . . . . . . . . . . . . . 6-4 Environment Summary View . . . . . . . . . . . . . 6-15
7 Stacks ........................................................... 7-1 7.1 7.2
Stack View. . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-4 Stack Summary View . . . . . . . . . . . . . . . . . . 7-10
8 Tips ............................................................... 8-1 8.1 8.2 8.3 8.4
Tip View. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-4 Tip Dynamic View . . . . . . . . . . . . . . . . . . . . . 8-35 Size Tip View. . . . . . . . . . . . . . . . . . . . . . . . . 8-40 Tip Summary View . . . . . . . . . . . . . . . . . . . . 8-42
9 Receptors ..................................................... 9-1 9.1 9.2 9.3 9.4
Receptor Point View . . . . . . . . . . . . . . . . . . . . 9-5 Receptor Point Dynamics View . . . . . . . . . . . 9-20 Receptor Point Summary View . . . . . . . . . . . 9-22 Receptor Grid View . . . . . . . . . . . . . . . . . . . . 9-25
10 Shields........................................................ 10-1 10.1 10.2 10.3 10.4 10.5 2
Shield View . . . . . . . . . . . . . . . . . . . . . . . . . . 10-4 Rectangle Builder . . . . . . . . . . . . . . . . . . . . 10-11 Polygon Builder . . . . . . . . . . . . . . . . . . . . . . 10-13 Pit / Hut Builder . . . . . . . . . . . . . . . . . . . . . . 10-15 Transform View . . . . . . . . . . . . . . . . . . . . . . 10-17
11 Dispersion .................................................. 11-1 11.1 11.2
Dispersion View. . . . . . . . . . . . . . . . . . . . . . . 11-4 Implementation Details . . . . . . . . . . . . . . . . 11-12
12 Overlays And Isopleths............................. 12-1 12.1 12.2 12.3
Overlay View . . . . . . . . . . . . . . . . . . . . . . . . . 12-4 Zoom View . . . . . . . . . . . . . . . . . . . . . . . . . 12-15 Isopleth Customise View . . . . . . . . . . . . . . . 12-17
13 KO Drums................................................... 13-1 13.1 13.2
KO Drum View. . . . . . . . . . . . . . . . . . . . . . . . 13-4 KO Drum Summary View . . . . . . . . . . . . . . 13-23
14 Case Studies .............................................. 14-1 14.1 14.2
Case Study View . . . . . . . . . . . . . . . . . . . . . . 14-4 Select Variable View . . . . . . . . . . . . . . . . . . 14-18
15 Calculations ............................................... 15-1 15.1 15.2
Calculation Sequence . . . . . . . . . . . . . . . . . . 15-3 Calculation Options View . . . . . . . . . . . . . . . 15-4
16 Printing ....................................................... 16-1 16.1 16.2 16.3 16.4
Report View. . . . . . . . . . . . . . . . . . . . . . . . . . 16-4 Output Graphic Report View . . . . . . . . . . . . . 16-9 Select Graphic Report Printer . . . . . . . . . . . 16-13 Graphic Report Page Settings. . . . . . . . . . . 16-14
17 Calculation Methods ................................. 17-1 17.1 17.2 17.3 17.4 17.5 17.6
Thermal Radiation . . . . . . . . . . . . . . . . . . . . . 17-4 Surface Temperature. . . . . . . . . . . . . . . . . . 17-20 Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-21 Purge Gas . . . . . . . . . . . . . . . . . . . . . . . . . . 17-28 Water Sprays. . . . . . . . . . . . . . . . . . . . . . . . 17-31 Gas Dispersion . . . . . . . . . . . . . . . . . . . . . . 17-33 3
17.7 17.8
Nomenclature . . . . . . . . . . . . . . . . . . . . . . . 17-36 References . . . . . . . . . . . . . . . . . . . . . . . . . 17-38
A Graphic Report Layout............................... A-1 A.1 A.2
Introduction to XML . . . . . . . . . . . . . . . . . . . . . A-4 Layout File Structure . . . . . . . . . . . . . . . . . . . . A-6
4
Introduction
1-1
1 Introduction Page 1.1
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2
Program Overview . . . . . . . . . . . . . . . . . . . . 8
1.2.1 1.2.2 1.2.3
1.3
Flaresim Objects . . . . . . . . . . . . . . . . . . . . . 9 Object Definition . . . . . . . . . . . . . . . . . . . . .11 Running a Model . . . . . . . . . . . . . . . . . . . . 13
Documentation Overview . . . . . . . . . . . . . 14
1-1
1-2
1-2
Introduction
1-3
Flaresim is a computer program designed to assist professional engineers in the design and evaluation of flare systems. The program calculates the thermal radiation and noise generated by flares and estimates the temperatures of exposed surfaces. It also performs dispersion analysis of the combustion gases or relieved fluid in flame out conditions. Flaresim provides a user friendly interface with program actions accessed by menu and toolbar options. Data entry is through a series of data views controlled from an overall Case Navigator view. Context sensitive help is available at all points to assist the user in the use of the program and selection of appropriate design parameters. Output from the Flaresim is highly customisable with the user having the freedom to select summary or detailed output. The reports also include graphical output where appropriate. Experienced flare system engineers should read the remainder of this chapter for an overview of the way that Flaresim performs calculations. They may then find that they will be able to use the program with assistance from the help system without further reference to the manual. However we would advise study of the manual to become familiar with the full range of options and recommendations for using the program. Engineers new to flare system design should work through the examples in the Getting Started section of the manual after first reading this chapter. The examples provide a step by step guide to using Flaresim for flare system design and highlight some of the critical parameters that must be determined.
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1-4
Features
1.1 Features The following features highlight the main capabilities of Flaresim. • Equally applicable to the design of flare systems for offshore platforms, gas plants, refineries and chemical plants. • Data may be entered and reported in the users choice of units and may be converted at any time. • Correlations are available for modelling a range of flare tips including sonic tips, pipeflare tips and steam or air assisted tips. For assisted flares the quantity of steam or air required for smokeless operation can be calculated. • A number of correlations are provided to predict the fraction of heat radiated from flames of a range of hydrocarbon fluids with different types of flare tip. • Liquid flaring systems can be handled. • A wide range of algorithms for calculation of thermal radiation. These include integrated multipoint methods and the Chamberlain (Shell) method in addition to the Hajek/Ludwig and Brzustowski/Sommer methods which are described in the API guidelines for flare system design. • Full three dimensional flame shape analysis with complete flexibility in specification of the location and orientation of multiple stacks. • Thermodynamic flash routines from NIST to calculate change in fluid properties with pressure. • Dynamic calculation option to evaluate results as flare flows vary with time.
1-4
Introduction
1-5
• Case study manager to allow multiple comparitive results to be generated within a single Flaresim model. • Calculation of combustion gas composition. • Calculation of purge gas flows required for tips. • Jet dispersion model to analyse flammable gas concentrations close to flare in flame out conditions. • Gaussian dispersion model to analyse longer distance dispersion of the relieving fluid or combustion gases. • A range of options for defining and analysing the noise spectrum generated by flare systems including user defined spectra. • Ability to define multiple environmental scenarios to allow rapid evaluation of flare system performance under different wind speeds and directions. • Multiple stacks/booms each accomodating multiple flare tips. • Calculation of radiation, noise spectrum and surface temperatures at multiple receptor points. • Calculation of radiation variation with wind direction and speed at a point and display of results on a wind rose chart. • Ability to define multiple receptor grids in multiple planes for calculation of radiation, noise or surface temperatures. • Plotting of grid results as isopleth contours for sterile area definition. • Receptor point characteristics for calculating surface temperatures include mass, absorbtivity, emissivity, area, specific heat, orientation and initial temperature.
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1-6
Features
• Option to define local environmental conditions at receptor points for calculating temperatures. • Sizing and rating of knock out drums. • Modelling of water curtains or solid shields to reduce radiation and noise transmission. • Sizing of stack or boom length to meet radiation, noise or surface temperature limits at defined receptor points. • Sterile area calculations to allow the safe distance from flare stack at different radiation limits. • A setup wizard to allow new users to set up an initial model rapidly with appropriate defaults. • Expert mode to control access to less commonly used options. • Import of files from Flaresim 2.0 and later. • Multiple reports can be created and compared as updates are made to a model and the data corresponding to any report can be saved. • Quality Assurance options are included in the reports. • Customisable HTML reports • Customisable graphic reports • Multiple Flaresim cases can be open at the same time. The wide range of calculation options available within Flaresim may lead to the possibility of selecting inappropriate correlations for a particular combination of fluid type and flare system configuration. While we have tried to prevent the use of the more obvious problems we have also tried to allow flexibility for “one off” situations. As
1-6
Introduction
1-7
with all engineering computer software, Flaresim is a tool which cannot replace sound engineering judgement. Softbits Consultants Ltd are always interested in continuing product development to ensure that Flaresim meets the needs of our clients. Should you wish to see any feature incorporated in Flaresim, please feel free to contact us at
[email protected]. If the request is reasonable we will endeavour to include it in future releases of the program.
1-7
1-8
Program Overview
1.2 Program Overview The Flaresim program has been developed to provide great flexibility in modelling by breaking down the flare system into a number of objects such as fluids, stacks, tips etc. These individual objects are then linked together to define the complete system. Flaresim provides a Case Navigator view, see Figure 1-1, that shows a tree structure of all the objects that have been defined in a given model and provides a rapid overview of which ones are currently complete and in use. Figure 1-1, Case Summary view
Case Navigator Icons Required object present and ready Required object missing or not ready Optional object Permanent object Object ready Object not ready Object ignored
1-8
Introduction
1-9
1.2.1 Flaresim Objects The objects that can be defined are:Case Summary Each model contains a single Case Summary object which defines descriptive information. Fluids A model can contain multiple fluid objects. Each object describes the physical properties of a fluid to be flared such as density, lower heating value, lower explosive limit etc. Fluids may be defined either by entering bulk properties or by defining the composition of the fluid to allow calculation of its properties from pure component data. A single fluid can be flared through multiple tips. Environments A model can contain multiple environment objects each of which describes a combination of wind speed, direction, humidity etc. The variation of wind speed with direction can also be defined to support wind rose calculations. Environment characteristics can also be defined for use in dispersion calculations. Only one environment object can be active for a set of calculations. Stacks Multiple stack objects can be defined which may be active or ignored in any set of calculations. Stack data includes length, location and orientation. Each stack may support multiple flare tips. The distance from each stack to defined radiation and noise limits can be calculated to evaluate the sterile area required around each stack. Tips Multiple tip objects can be defined and set active or ignored in a set of calculations. Tip data includes tip type and associated calculation methods, dimensions and stack location data and the flow and selection of the fluid being flared. Tip objects provide access to flame shape and other tip specific results such as combustion gas composition and purge gas requirements. Tip objects also have a
1-9
1-10
Program Overview
dynamic view that allows the variation in flare flow with time to be defined and modeled. Receptor Points Multiple receptor point objects can be defined and then set active or ignored in a set of calculations. Receptor point data includes location, characteristics for surface temperature calculation and constraints for sizing calculations. Receptor point objects provide access to results calculated for the point. The effect of wind speed and direction on the radiation can also be calculated and displayed as a wind rose plot. Receptor point objects also provide a dynamics view that displays the variation of results as the flare flow varies with time. Receptor Grids Multiple receptor grid objects can be defined and then activated or ignored in a set of calculations. Receptor grid data includes orientation, location and coarseness data as well as characteristics for surface temperature calculations. Receptor grid objects provide access to their calculated results including contour plots of radiation, noise, surface temperature and gas dispersion. Assist Fluids Multiple assist fluid objects may be defined and selected for one or more flare tips. Data includes assist fluid type and calculation method to be used. Shields Multiple shield objects may be defined to model the reduction in radiation and noise through the installation of water sprays and solid shields. The transmissivity of water sprays can be specified by the user or calculated using an internal correlation. Shields can also be defined to model burn pits or protective locations. Dispersions Multiple dispersion objects may be defined to model the dispersion of combustion gases and flare fluids over long distances using a Gaussian dispersion model. Either concentration contour plots for a single pollutant or a downwind plot for multiple pollutants can be calculated. 1-10
Introduction
1-11
Overlays Overlay objects allow simple drawings to be created to act as background pictures for contour plots produced by the Receptor Grid and Dispersion objects. KO Drums KO Drum objects may be defined to perform Sizing and Rating calculations for knock out drums. Vapour and liquid properties can be entered directly or a composition specified to allow them to be calculated by the NIST flash package. Calculations may be run for either horizontal or vertical drums with a variety of end types. Either API or GPSA settling velocity correlations can be selected. Case Studies Case study objects can be created to run comparitive calculations to be run alongside the main calculation case. Two types of Case Study are available. A discrete input Case Study allows a set of input variables to be selected and case by case values defined.. An incremental input Case Study allows values for one or two input variables to be varied in steps over a range of values. Any result variable can be selected for output in either type of Case Study. Calculation Options A single calculation options object defines the correlations to be used in the calculations. It also provides for control of stack sizing options, heat transfer options to be used for temperature calculations and default emissions data. A data fitting option is also available. Component Management A component library manager object allows maintenance of the pure component database.
1.2.2 Object Definition Flaresim objects are created by selecting the branch in the Case Navigator view and then clicking the Add button. Alternatively the Add dropdown menu in the Case Navigator can be used.
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Program Overview
Creation of an object automatically opens its view to allow its data to be entered. When all the required data has been entered the status text at the bottom of the view will indicate Ready as shown in Figure 1-2. Some objects have more data items than will fit on a single form so their views have been divided into multiple tabs. For example the Stack view as shown in Figure 1-2 has tabs for Details and Sterile Area. Individual tabs are selected by clicking on their name. Existing objects can be updated by double clicking them in the Case Navigator view or selecting them in the Case Navigator view and clicking the View button. When the Case Navigator is closed existing objects can be displayed by selecting them in the View dropdown menu. Figure 1-2, Stack View
1-12
Introduction
1-13
1.2.3 Entering Values When new values are entered in Flaresim they are checked to ensure that they lie between a minimum and maximum value designed to protect the Flaresim calculations from unreasonable values. The fact that a value falls within the range allowed by Flaresim does not mean that it is thereby valid - the validity of all values entered are the responsibility of the user.
1.2.4 Running a Model In order to run calculations a Flaresim model must contain at least one of each of the following objects in an active and ready state. • Fluid object • Environment object • Stack object • Tip object While this is sufficient to perform calculations this will not calculate any radiation, noise or surface temperature results without addition of at least one active Receptor Point or Receptor Grid. Calculations are started by clicking the button at the top of the Case Navigator. This button is also used to display the progress of calculations and the status of the model. When the Case Navigator is closed the icon can be clicked to run the model. Progress of calculations and any problems encountered are reported in the right hand Message window at the bottom of the Flaresim screen. Results from the calculations may be viewed through the appropriate tabs in the Tip view, Receptor Point view or Receptor Grid view. Results may be viewed in tabular or graphical format where appropriate. Alternatively results can be viewed and printed through the Print or Print Graphic Report buttons in the Case Navigator tool bar. Once complete a case can be saved using the Save buttons in the Case Navigator tool bar.
and Save As
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1-14
Documentation Overview
1.3 Documentation Overview The printed Flaresim manual contains the following chapters:Chapter 2 - Tutorial with detailed worked examples. The electronic documentation in the file Flaresim.pdf contains this material and the following additional chapters which provide a full detailed description of the program features. Chapter 3 - Concepts, Flaresim Interface, Menu structure, Log Panels and File Dialogs. Chapter 4 - General Setup including Case Navigator, Case Summary, Preferences and Component Management. Chapter 5 - Fluid and Assist Fluid views. Chapter 6 - Environment view. Chapter 7 - Stack view. Chapter 8 - Tip view. Chapter 9 - Receptor Point and Receptor Grid views. Chapter 10 - Shield view. Chapter 11 - Dispersion view. Chapter 12 - Overlay editor view. Chapter 13 - KO Drum view. Chapter 14 - Case Study view. Chapter 15 - Calculation Options view. Chapter 16 - Report options inc. Print Reports and Graphic Reports. Chapter 17 - Calculation methods. Appendix A - Graphic Report Layout File Definition 1-14
Getting Started
2-1
2 Getting Started Page 2.1
Offshore Flare Stack Design . . . . . . . . . . . .4
2.1.1 2.1.2 2.1.3 2.1.4 2.1.5 2.1.6 2.1.7 2.1.8 2.1.9
2.2
Onshore Flare Stack Design . . . . . . . . . . .24
2.2.1 2.2.2 2.2.3 2.2.4 2.2.5
2.3
Objective . . . . . . . . . . . . . . . . . . . . . . . . . . . Model Setup . . . . . . . . . . . . . . . . . . . . . . . . Initial Calculations . . . . . . . . . . . . . . . . . . . Sizing Setup . . . . . . . . . . . . . . . . . . . . . . . . Run Sizing Calculations . . . . . . . . . . . . . .
24 24 30 32 33
Using Shields . . . . . . . . . . . . . . . . . . . . . . . 35
2.3.1 2.3.2 2.3.3 2.3.4 2.3.5 2.3.6
2.4
Objective and Data . . . . . . . . . . . . . . . . . . . . 4 Initial Setup. . . . . . . . . . . . . . . . . . . . . . . . . . 4 Initial Calculations . . . . . . . . . . . . . . . . . . . 13 Print Results . . . . . . . . . . . . . . . . . . . . . . . . 15 Sonic Tip Design . . . . . . . . . . . . . . . . . . . . 17 Run Sonic Tip & Review Calculations . . . 18 Compare Results . . . . . . . . . . . . . . . . . . . . 19 Two Tip Design . . . . . . . . . . . . . . . . . . . . . . 21 Update Pipe Tip . . . . . . . . . . . . . . . . . . . . . 23
Offshore Case - Add Welltest Burner . . . . Offshore Case - Run Welltest Calc’s . . . . Offshore Case - Add Water Screen. . . . . . Onshore Case - Workshop Surroundings Onshore Case - Add Workshop . . . . . . . . Onshore Case - Add Local Environment .
35 37 37 39 41 43
Using Overlays . . . . . . . . . . . . . . . . . . . . . . 45 2-1
2-2
2.4.1 2.4.2
2.5
Case Study . . . . . . . . . . . . . . . . . . . . . . . . . 51
2.5.1 2.5.2
2.6
Objective and Data. . . . . . . . . . . . . . . . . . . .64 Load or Create Base Case . . . . . . . . . . . . .65 Jet Dispersion Calculation . . . . . . . . . . . . .65 Gaussian Dispersion, Contour Plot . . . . . .67 Gaussian Dispersion, Line Plot . . . . . . . . .69 Dispersion Analysis Comments . . . . . . . . .71
KO Drum . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
2.8.1 2.8.2
2-2
Offshore Case . . . . . . . . . . . . . . . . . . . . . . .59
Gas Dispersion. . . . . . . . . . . . . . . . . . . . . . 64
2.7.1 2.7.2 2.7.3 2.7.4 2.7.5 2.7.6
2.8
Offshore Case Study - Discrete Variable . .51 Onshore Case Study - Increm. Variable. . .55
Dynamics . . . . . . . . . . . . . . . . . . . . . . . . . . 59
2.6.1
2.7
Offshore Case - Flaresim Overlay . . . . . . .45 Onshore Case - External Overlay File . . . .48
Initial Sizing . . . . . . . . . . . . . . . . . . . . . . . . .73 KO Drum Rating . . . . . . . . . . . . . . . . . . . . . .75
Getting Started
2-3
The purpose of this chapter is to provide an introduction to the use of Flaresim. The examples show how Flaresim may be used to calculate thermal radiation, noise and exposed surface temperatures arising from flaring at one or more flare stacks. Examples of case studies, dynamic and dispersion calculations are also given. The examples begin with simple flare stack designs for offshore and onshore situations which are then refined and expanded. The examples attempt to highlight some of the critical parameters to be considered when designing a safe flare system. The examples build up in stages. If you wish to skip a particular stage, the folder [Public Documents]\Softbits\Flaresim 4.0\Samples has model files saved at each stage.
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Offshore Flare Stack Design
2.1 Offshore Flare Stack Design 2.1.1 Objective and Data The objective is to design a flare stack for an offshore platform. It is assumed that an inclined flare boom will be used, mounted on the side of the platform which faces the prevailing wind. The design is to be based on thermal radiation limits as follows:• 1,500 btu/hr/ft2 at the base of the flare stack. • 600 btu/hr/ft2 at the helideck located 150 ft from the side of the platform and 30 ft above the base of the flare stack. The following design data is available Fluid Material Hydrocarbon Vapour Flow 100,000 lb/hr Mol Wt. 46.1 Vapour Temp. 300 ° F Heat of combustion 21,500 btu/lb Heat Capacity ratio 1.1 Tip Diameter
18 in
Wind Velocity
20 mph
2.1.2 Initial Setup
New File Icon
2-4
1.
Start the Flaresim program through the Windows Start button in the usual way.
2.
We are going to build our first model through the Setup Wizard. For a new installation of Flaresim this will open automatically, ready to build a new model. If this does not appear then you should select the File - Preferences menu option and select the “Use Setup Wizard for New Cases” check box on the Files & Options tab. Then select File -
Getting Started
2-5
New or the New File icon on the tool bar to create a new case with the Setup Wizard. 3.
In the opening view of the Setup Wizard, set the unit set to Default Field as shown. Then click the Next button to move to the Fluid definition tab.
Figure 2-1, Setup Wizard Opening View
4.
In the Fluid tab of the Setup Wizard, enter the following data items, using the tab key or the mouse to move from field to field. Temperature = 300 ° F Mole Weight = 46.1 LHV = 21500 btu/lb Cp/Cv = 1.1
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Offshore Flare Stack Design
LEL is used only by the Brzustowski flare radiation method.
Note that some of these values (e.g Temperature or Cp/Cv) are originally displayed in purple colour denoting a default value. When you enter a value the colour changes to blue denoting a user specified value. The full list of colours used by Flaresim to display values is:Purple for a fixed default value Red for calculated default values Blue for a user specified value Grey for a fixed, unchangeable input value Black for a calculated result The remaining values for Ref Pressure, LEL and Saturation can be left at their default values. The finished view is shown below Figure 2-2, Setup Wizard Fluid Tab
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Getting Started
2-7
Note that Flaresim requires the lower heating value for a fluid within its calculations. We are assuming that the value we have been given is the lower, net heating value rather than the higher, gross heating value. Advice on the usage of each input value and the allowable input range is displayed in the advice panel as you move through the input fields. When the entries are complete click the Next button. 5.
In the Tip tab, select the radio button to set the tip type to a Pipe Tip. In the table including the selection of F Factor method, select the check box to select the Generic Pipe method. The F Factor, i.e. the fraction of heat radiated by the flame, is a critical design parameter for flare system design. The Generic Pipe correlation has been developed to predict F Factors across a range of exit velocities and fluid molecular weights and is generally recommended for initial calculations. For final designs, we would always recommend consulting a flare system vendor for advice on the appropriate F Factor for a specific fluid and specific flare tip.
6.
Still in the Tip tab, enter the Fluid Mass Flow Rate as 100,000 lb/hr. After this entry has been completed, the Tip Diameter field is updated to show the tip diameter required for the default Mach number of 0.45. In our case we know the tip diameter is 18 in so we update the calculated value to 18 in. The Mach number will be updated to 0.199 to indicate the velocity for the new diameter. When complete the view should be as shown in Figure 2-3. Click the Next button to move to the next tab.
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Offshore Flare Stack Design
Figure 2-3, Setup Wizard Tip Tab
7.
The humidity value is only used when calculating the transmissivity.
In the next tab, the Environment tab, enter the wind speed. Since the value we have been given is 20 mph, we first click the entry displaying ft/s and select mph in the drop down menu before entering the value. If we wish to see the value in ft/s, click again in the units entry and select ft/s to display the converted value of 29.33 ft/s. The remaining items can be left at their default values namely Wind Direction as 0 (i.e. North), Temperature 59 ° F, Humidity 10% and the User Transmissivity 1.0, with the Transmissivity Method set to “User specified”. Note this default transmissivity method with a specified transmissivity value of 1.0 is the most conservative option. The final input is to remove the tick from the check box labelled “Include Solar Radiation” which means that the
2-8
Getting Started
2-9
specified solar radiation value will NOT be added to the calculated value of flare radiation. Including solar radiation leads to a more conservative design. API 521 states that its inclusion should be considered on a case by case basis. Solar radiation can have a significant impact on the flare design when low radiation values are considered. Since we are considering a low design radiation for the Helideck, in this case we will exclude solar radiation for this example. The completed view is shown as Figure 2-4. Click the Next button to continue. Figure 2-4, Setup Wizard Environment Tab
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Offshore Flare Stack Design
8.
In the Stack tab, select the radio button to set the Vertical Orientation to 60 degrees from horizontal. Then set the Stack Horizontal Orientation angle to 0 (i.e. North). The Stack Length will be left unspecified to let Flaresim calculate it. Click the Next button to continue
9.
In the Receptors tab, click on the default receptor point “RP_1” and rename it to “Stack Base”. Set its Distance Downwind from Stack to 0 ft and confirm that the Allowable Radiation for the point is 1500 btu/hr/ft2.
Figure 2-5, Setup Wizard Receptors Tab
Click the Add button to create an additional receptor point for the radiation at the Helideck. Change the default name “RP_2” to “Helideck” and enter the location as Northing -150ft, Easting 0ft, Elevation 30ft. and the radiation limit as 2-10
Getting Started
2-11
600 btu/hr/ft2. The completed form is shown as Figure 2-5 above. Click the Next button to continue. 10.
In the Calculations tab, set Calculation Method check box to Mixed and the Flame Elements to 25. As discussed in the Methods chapter, the Mixed method is a compromise designed to give the best accuracy for calculating radiation both close to and further away from the flame. As such it is a good default method. 25 flame elements is usually sufficient to calculate the flame shape with a reasonable degree of accuracy. The completed view is shown as Figure 2-6. We have completed the Setup Wizard so click the Finish button.
Figure 2-6, Setup Wizard Calculations Tab
11.
When the Finish button is clicked, the Setup Wizard takes the data we have supplied and uses it to create the Flaresim 2-11
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Offshore Flare Stack Design
objects that we need for our initial model. The Case Navigator view will be displayed to list all of these objects as shown in Figure 2-7. Note that the icon is shown against each object indicating it is ready to calculate and that the icon is shown against the key object branches to indicate that the model has the minimum information needed to run calculations. At this point you can open each object’s view by double clicking on them in the Case Navigator to see how the Setup Wizard has initialised the values. Figure 2-7, Case Summary
12.
This is a suitable point to save the data we have entered so far. Click the button in the tool bar at the top of the Case Navigator or main tool bar. Since we have not yet saved the file, a File Save Dialog window will appear to allow us to specify the location and name of the file. Use the name “Ex1 - Offshore - Ready To Run”.
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Getting Started
2-13
2.1.3 Initial Calculations 13.
We are now ready to run the calculations by clicking the large button labelled “Click to Calculate” at the top of the Case Navigator. The button will change to show a progress bar as the calculation runs. Messages will be output to the Error/Warnings/Info log as the calculations progress. When calculations are complete the colour of the log panel will change to summarise the status of the calculations. A green colour represents success, yellow represents some warnings were generated and red represents errors were encountered.
Figure 2-8, Error/Warnings/Info log
The scroll bars can be used to review earlier messages. The log window can be resized by dragging the separator bar above it. We can now review the results. Click Stack 1 in the Case Navigator view and click the View button. The view will show that the stack length has been calculated as 247ft. Double click the Grid 1 item in the Case Summary view and then click the Radiation tab. Then select Plot in the Display drop down. The radiation isopleths are displayed as shown below.
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Offshore Flare Stack Design
Figure 2-9, Receptor Grid Isopleth Plot
Finally open the Receptor summary view by double clicking the “Receptor Point” branch label in the Case Navigator. As shown below, the Radiation Results line shows that our design radiation limit of 600 btu/h/ft2 has been met for the Helideck receptor, while the radiation value at the Stack Base receptor is lower than its allowed value limit at 767 btu/hr/ft2.
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Getting Started
2-15
Figure 2-10, Receptor Point Summary
14.
This completes our initial design. Save the case as “Ex1 Offshore - Initial Results”.
2.1.4 Print Results 15.
Select the Print button in the Case Navigator tool bar. The Report Preview view shown below in Figure 2-11 opens. Note that this will open in a new window, independent of the main Flaresim view.
16.
Select the report elements you wish to see printed. To see what the report will look like with the current set of elements, you will need to click the Refresh button to update it.
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Offshore Flare Stack Design
Figure 2-11, Report Preview
In order to allow us to compare these results with future results you will need to ensure that the Stack Configuration, Tip Results (General and Flame Shape elements) and the Receptor Point results are included. Once you have set your preferred report options you can click the Save Options button to save your report options to a configuration file. Your chosen options will also be saved with the case. 17.
When you are happy with the options you have chosen click the Print button to send the report to your default printer. The standard Printer Dialog view will appear to allow the printer and other options to be selected.
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Getting Started
2-17
2.1.5 Sonic Tip Design The design that we have produced meets our design radiation limits but requires a long 247ft stack. Since we are designing a flare stack for an offshore platform, we wish to minimise the length and hence the weight of the flare stack as much as possible. Therefore we will attempt to reduce the required flare stack length by redesigning the system with a sonic flare tip. The fluid data, environmental data and radiation limits are the same as for Example 1. 1. If you are continuing from the previous section, you should save your case before continuing using the button from the tool bar at the top of the Case Navigator. Skip to step 3. 2.
Otherwise use the File - Open menu option or the icon. In the File Open dialog that appears, browse to the Samples folder created by your Flaresim installation. This will usually be in the Softbits\Flaresim 4.0 folder in your configured “Documents” folder. Select the file “Ex1 - Initial Result.fsw” and click the Open button.
3.
Create a new tip by selecting the Tip branch in the Case Navigator view and then clicking the Add button or by selecting the Add - Tip drop down menu option.
4.
After the Tip View opens, enter the following data on the Details tab: Name = “Sonic Tip” Tip Type = Sonic Number of Burners = 1 Seal Type = None Fraction Heat Radiated Method = High Efficiency
5.
On the Noise Input tab of the Tip view enter the following data: Combustion Noise Method = Standard Reference.
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Offshore Flare Stack Design
6.
Move to the Location & Dimensions tab and enter the following data: On Stack = Stack_1 Length = 3.0ft Angle to Horizontal = 90 Angle to North = 0 Exit Diameter = 18in Riser Diameter = 18in Contraction Coefficient = 1.0 (default) Exit Loss Coefficient = 1.0 (default) Roughness = 9.843e-4in (default) Calc Burner Opening = Selected
7.
Click on the Fluids tab and enter the following: Fluid Name = Fluid 1 Fluid Mass Flow = 100,000lb/hr
8.
At this point, the Status Text at the bottom of the Tip view should indicate that the tip data is complete. Close the view.
9.
In the Case Navigator, select the branch labelled Tip 1 and then click the Ignore button. The icon beside the label should turn to a icon to confirm that the tip will not be included in the calculations.
2.1.6 Run Sonic Tip & Review Calculations 10.
We are now ready to run the calculations. Click the large button at the top of the Case Navigator. Once Flaresim has finished calculating, check the Errors/ Warnings/Info log panel to confirm that the expected calculations for the two Receptor Points have been completed. Note that if any earlier messages in the log panel are causing confusion, you can click the right mouse button over the log panel to access a pop-up menu. This provides a Clear option to remove the current log messages.
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Getting Started
11.
We are now ready to review the results. Open the Stack view for the Main Stack. The new length calculated for the stack is 68ft.
12.
Open the Receptor Summary view. This indicates that the Stack Base receptor point is now the controlling limit since the thermal radiation at this point is calculated as 1500 btu/ hr/ft2. The radiation at the Helideck receptor point is 543 btu/hr/ft2.
13.
Save the new design to a new case name, “Ex1 - Offshore Sonic Tip Results”.
14.
Generate a report for this new case using the Print tool bar button.
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2.1.7 Compare Results Our new design with the sonic flare tip is clearly better since it leads to a much shorter stack. This will save a great amount of weight and hence cost over our initial design using the pipe flare tip. It is worth doing a detailed comparison to understand the difference between the designs: 15.
Reopen the original case “Ex1 - Offshore Initial Results.fsw” and click the Print tool bar button. Since reports are generated in separate windows then you will now have two report windows that you can compare side by side. Note that both cases are open simultaneously in Flaresim and you can switch between them using the Windows menu option. Alternatively you can use your Internet browser to view the saved report files “Ex1 - Offshore Initial Results.html” in the “Samples\Ex1 - Offshore Initial Results” sub-folder and “Ex1 - Sonic Tip Results.html” in the “Samples\Ex1 - Offshore Sonic Tip Results” sub-folder (usually in [Documents]\Softbits\Flaresim 4.0).
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Offshore Flare Stack Design
16.
Find the Tip Data - Results section in the reports. The fraction of heat radiated value for the Pipe flare design is 0.35 while that for the Sonic design is 0.1. The fraction of heat radiated by a flare is a critical parameter in the design. Pipe flares exhibit relatively poor mixing of air with the flared fluid and as a result the flame contains many partially combusted luminescent carbon particles that give it an orange colour and a relatively high fraction of heat radiated. Sonic flare tips are designed to maximise the mixing of air and the flared fluid and so burn with a clearer flame with lower heat radiation. By selecting the appropriate F Factor method to calculate the fraction of heat radiated in both our designs, we have allowed the program to calculate an appropriate value for the different tips. However since this is such an important factor in the design, the heat radiation factor to be used should be confirmed with your flare system vendor prior to the final design. Should you wish to use a heat radiation factor supplied by a vendor you should set the method to User Specified and enter the value.
17.
Still in the Tip Data - Results section of the reports find the flame length. For the Pipe flare design this is 173 ft, while for the Sonic flare design the flame length is 88ft. Note that the flame length calculated by the API method is the same in both cases. Sonic flare tips by their design and by their greater gas exit velocities lead to a flame shape that is shorter and stiffer compared to that of a pipe flare. As a result the flame is less affected by wind and stays closer to the tip and thus further from the platform. This can be seen most clearly by comparing the 3D plot of the Flame Shape in the reports. Finally in the Tip Results section of the reports, find the tip back pressure i.e. tip inlet pressure. For the Pipe flare this is 14.7 psi while for the Sonic flare it is 26.0 psi.
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Getting Started
2-21
The fact that the sonic tip is operating at choked conditions means that the pressure drop over this type of tip is much higher than for the pipe tip. Thus a sonic tip can only be used if the resulting back pressure on the flare system is not so high as to prevent safe relief of the gas. Comparison of our two designs using the pipe tip and the sonic tip shows that the sonic tip is much better since it produces a shorter, stiffer flame with a lower F Factor than the pipe flare. This means that the flare stack can be much shorter while still meeting radiation limits. Given the advantages of the sonic tip, it might appear that we should always specify this type of tip. However we have also seen that the sonic flare tip results in higher back pressures on the flare system. In many cases, this additional back pressure will be too high to allow safe relief from all the possible relief sources in the process. Therefore it is common to see designs with both high and low pressure flare systems relieving through different tips.
2.1.8 Two Tip Design The relieving sources in our process have been reviewed to check the new back pressure resulting from the sonic tip is acceptable. The review has shown that 10,000 lb/h of the material being flared cannot be relieved safely at the new higher back pressure. As a result we have decided to split our design so this 10,000 lb/h is relieved through a low pressure flare system, leading to a pipe tip with the remaining material flowing through a high pressure flare system to a sonic tip. 1. If you are continuing from the previous section you should save your case before continuing using the Save tool bar button 2.
in the Case Navigator. Skip to step 3.
Otherwise use the File - Open menu option or the icon. In the File Open dialog that appears, browse to the Samples sub-folder of your Flaresim installation (usually [Public
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Offshore Flare Stack Design
Documents]\Softbits\Flaresim 4.0), select the file “Ex1 Offshore - Sonic Tip Results.fsw”and click the Open button. 3.
In the Case Navigator view, double-click the Sonic Tip branch to open the view for this Tip. On the Fluids tab, change the flow rate to 90,000 lb/h. Close the view.
4.
Open the view for the Tip 1 by double-clicking this in the Case Navigator view or by selecting it and then clicking the View button. Rename the tip to “Pipe Tip”. On the Fluids tab, change the flow rate to 10,000 lb/h. Then clear the tick from the Ignore check box to activate this tip again. Close the view.
5.
We are now ready to run the calculations. Click the large button at the top of the Case Navigator. Check the Errors/Warnings/Info log panel to confirm that the expected calculations for the two Receptor Points have been completed.
6.
Open the Stack view for the Main Stack. The new length calculated for the stack is 96ft.
Figure 2-12, Stack View
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Getting Started
7.
2-23
Open the Receptor Summary view. This indicates that the Main Stack receptor point is still the controlling limit since the thermal radiation at this point is still calculated as 1500 btu/hr/ft2.
2.1.9 Update Pipe Tip In reducing the flow through the Pipe tip we have changed its performance: 8.
Open the Tip view for the Pipe tip. You will see on the Details tab that the fraction of heat radiated from this tip has been calculated as 0.38 whereas before it was 0.35. The reason for this is the greatly reduced velocity, 0.02 mach, through the tip which reduces the tips efficiency. For efficient operation the velocity should be 0.2 mach or higher.
9.
On the Location & Dimensions tab, click the Size Me button. Set the Mach number to 0.3 and set “Use Nominal Diam” to “No” and the tip size will be calculated as 4.6 in. Set “Use Nominal Diam” back to “Yes” and a nominal diameter of 5 inch will be selected. The calculated Mach Number which be automatically updated and shows 0.25 Mach. This is acceptable, so click the Ok button. The tip size and riser diameter will automatically be updated to the new selected diameter.
10.
Now recalculate the case. The new exit velocity is 0.25 Mach and the fraction of heat radiated is now 0.34. The improvement in efficiency of this flare reduces the calculated size of the stack to 90ft.
11.
Our two tip design is complete so save the case as “Ex1 Offshore - Final Results”.
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Onshore Flare Stack Design
2.2 Onshore Flare Stack Design 2.2.1 Objective The objective of this tutorial is to calculate the sterile area around an existing vertical flare located in an onshore facility and evaluate whether the current design is acceptable during a General Power Failure (GPF) scenario. The sterile area will be calculated at an elevation of 2m, which represents the typical head height for personnel.
2.2.2 Model Setup 1.
Start the Flaresim program through the Windows Start button in the usual way.
2.
We will build our first model through the Case Navigator. Close the Setup Wizard that opens automatically when Flaresim starts up.
3.
Use the File/Preferences option on the main Menu. In the Units tab, select the European units set and close the view.
4.
Create a new Fluid by selecting the Fluids branch in the Case Navigator view and then clicking the Add button or by selecting the Add - Fluid drop down menu option.
5.
On the Properties tab of the Fluid view that opens enter the following data: Name = Flare Gas GPF Calculation Method = REFPROP Temperature = 160 ° C Pressure = 1.5 bar a
6.
2-24
Move to Options tab and enter the information below:
Getting Started
2-25
Correct Temperatures = Yes Isentropic Efficiency = 0% Flash Method = PR (default) When the Isentropic Efficiency is set to 0%, Flaresim will follow an isenthalpic thermodynamic path to bring the fluid from the reference T&P down to the pressure at the tip exit. 7.
In the Composition tab add the following components and the fraction in Mole basis: Methane Ethane Propane i-Butane n-Butane i-Pentane n-Pentane n-Hexane
0.20 0.20 0.30 0.10 0.15 0.02 0.02 0.01
Flaresim calculates the fluid properties as shown below. Cp/ Cv and the critical properties will be displayed after running the model if REFPROP thermo package is selected. Figure 2-13, Fluid View
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Onshore Flare Stack Design
8.
Create a new Environment by selecting the Environments branch in the Case Navigator view and then clicking the Add button or by selecting the Add - Environment drop down menu option.
9.
On the Overall tab of the Environment view that opens enter the following data: Name = 9D - No Solar - No Aten. Wind Speed = 9 m/s Wind Direction = 0 (wind blowing from the North) Include Solar Radiation = No (box unchecked) API 521 states that solar radiation should be considered on a case by case basis. Consideration should be given to: the frequency of the flaring event, the probability of personnel being present in the exposed location, the ease or difficulty of escape from the exposed location, etc. Accounting for these criteria and the fact that the scenario represents an emergency scenario, the solar radiation will be excluded in our case. Transmissivity Method = User Specified Transmissivity Value = 1 A value of 1 is the most conservative option as it does not take credit for atmospheric attenuation. Other Parameters = leave as default
10.
Move to Dispersion Data tab and enter the following data: Correct W. Speed For Height = Yes This option will use a wind speed vs height curve to correct the speed defined in the Overall tab and will have an effect on both radiation and temperature calculations. Other Parameters = leave as default
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Getting Started
11.
2-27
Create a new Stack by selecting the Stacks branch in the Case Navigator view and clicking the Add button or by selecting the Add - Stack drop down menu option. On the Details tab of the Stack view that opens enter the following data: Name = LP Flare Stack located at the origin: Northing = 0m Easting = 0m Elevation = 0m Length = 85m Angle to Horizontal = 90 deg Angle From North = 0 deg Size This Stack = No (box unchecked)
12.
Move to Sterile Area tab and enter the following data: Sterile Area Elevation = 2m (head height) Calculate Sterile Area = Yes Update the radiation table with the following limit values: 1.6 kW/m2 (For continuous exposure from API 521) 3.2 kW/m2 (Allowed during emergency escape) 4.7 kW/m2 (For 2min emergency actions from API 521)
13.
Create a new Tip by selecting the Tips branch in the Case Navigator view and then clicking the Add button or by selecting the Add - Tip drop down menu option. On the Details tab of the Tip view that opens enter the following data: Name = Pipe Flare - GPF 300t-h Tip Type = Pipe Number of Burners = 1 Seal Type = None Fraction Heat Radiated Method = Generic Pipe
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Onshore Flare Stack Design
Generic pipe F factor is a proprietary correlation based on refitting other methods across a range of exit velocities and molecular weights and represents a good approach when modelling gas pipe tips. 14.
On the Noise Input tab of the Tip view, enter the following data: Combustion Noise Method = Standard Reference.
15.
Move to the Location & Dimensions tab and enter the following data: On Stack = LP Flare Length = 0m Angle to Horizontal = 90 deg Angle to North = 0 deg Exit Diameter = 36 in Since the value we have been given is 36in, we first click the entry displaying "mm" and select "in" in the drop down menu before entering the value. If we wish to see the value in "mm" then click again in the units entry and select "mm" to display the converted value of 914.4 mm Burner Opening = 100% Riser Diameter = 36 in Roughness = 0.025 mm (default) Calc Burner Opening = No (box unchecked)
16.
Click on the Fluids tab and enter the following: Fluid Name = "Flare Gas GPF" Mass Flow = 300,000 kg/h At this point the Status Text at the bottom of the Tip view should indicate that the tip data is complete. Close the view.
17.
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Since we are interested in studying the radiation at head height, we will create a receptor grid to plot the radiation contours at this height. In the Case Navigator view, select
Getting Started
2-29
the Receptor Grids branch and click the Add button (alternatively select the Add - Receptor Grid drop down menu option) to create and open the view for a new Receptor Grid object. On the Extent tab enter the following data: Name = Grid @ Head Height Grid Plane = Northing-Easting Elevation Offset = 2m (head height) Northing Min = -250m Northing Max = 50m Northing Points = 41 Easting Min = -150m Easting Max = 150m Easting Points = 41 18.
We can customise the isopleth lines displayed on the plot. On the Radiation tab change the display to Plot and click on the Customise button to open the plot properties view. Go to Contour Details tab and select the check boxes to show only the isopleth values for 1.6, 3.2 and 4.7 kW/m2 as shown below. Note the colours of each isopleth can be customised by clicking on the line colour panel and selecting the colour from the pop-up colour picker dialog. Assign a navy blue colour to the 1.6 kW/m2 isopleth.
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Onshore Flare Stack Design
Figure 2-14, Customise Isopleths
19.
Finally we need to select a radiation method to perform the calculations. Open the Calculation Options view in the Case Navigator, select "Mixed" radiation method and set the No. Flame Elements to 25. As discussed in the Methods chapter of the documentation, the Mixed method is a compromise designed to give the best accuracy for calculating radiation both close to and further away from the flame. As such it is a good default method. 25 flame elements are usually sufficient to calculate the flame shape with a reasonable degree of accuracy.
2.2.3 Initial Calculations 20.
We are now ready to run the calculations. Click the large Calculate button at the top of the Case Navigator. Once Flaresim has finished calculating, check the Errors/ Warnings/Info log panel to confirm that the expected calculations have been completed. Note that this window is colour coded:
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Getting Started
2-31
Green when calculations are completed without warnings Yellow when calculations are completed with warnings Red when errors are detected and results not generated 21.
We are now ready to review the results. Open the "LP Flare" view and go to the Sterile Area tab. The distances to meet each of the specified radiation limits are displayed on the table as shown below in Figure 2-15.
Figure 2-15, Sterile Area Results
22.
Open the Receptor Grid view to inspect the isopleths plot by clicking on the Radiation tab and then selecting Plot as the Display option, see Figure 2-16. It presents the contours for the radiation limits of interest at head height, the same as the sterile area calculation.
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Onshore Flare Stack Design
Figure 2-16, Receptor Grid Results
23.
This completes our initial evaluation. Save the case as “Ex2 - Onshore - Rating Results.fsw
2.2.4 Sizing Setup The model that we produced for the existing flare calculated a distance of 120m from the flare base to the 4.7 kW/m2 radiation limit. Due to the proximity of process equipment and activities taking place in the vicinity of the flare, the extent of the calculated sterile area is not acceptable. The flare height needs increasing to meet a maximum permitted radiation level 4.7 kW/m2 on a horizontal plane elevated 2m from ground (head height). 1. If you are continuing from the previous example you should save your case before continuing using the Save button in the Case Navigator. Skip to step 3.
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Getting Started
2.
Otherwise use the File - Open menu option or the icon. In the File Open dialog that appears, browse to the Samples folder created by your Flaresim installation. This will usually be in the Softbits\Flaresim 4.0 folder in your configured "Documents" folder. Select the file "Ex2 Onshore - Rating Results.fsw" and click the Open button.
3.
Open the "LP Flare" view and enable the Size This Stack check box under the Details tab.
4.
Open the "Grid @ Head Height" view, select the Max Radiation tab and enter a Sizing Constraint of 4.7 kW/m2. Close the view.
5.
We will also create a grid for the vertical cross-section through the axis of the flare to visualise radiation levels at different elevations.
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In the Case Navigator view add a new Receptor Grid. On the Extent tab enter the following data: Name = Elevation Grid Grid Plane = Elevation-Northing Easting Offset = 0m (section through the axis of the flare) Elevation Min = 0m Elevation Max = 300m Elevation Points = 41 Northing Min = -250m Northing Max = 50m Northing Points = 41 Customise the isopleth lines to show only the isopleth values for 1.6, 3.2 and 4.7 kW/m2 as before.
2.2.5 Run Sizing Calculations 6.
Hit the Calculate button. The log panel is red indicating that there is an error in the calculations. The flare height needs to be higher than the maximum height set by default. 2-33
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Onshore Flare Stack Design
7.
Open the Calculation Options view from the Case Navigator, go to the Sizing & Pressure Profile tab and change the Stack Maximum Length to 150m. Rerun the case. The sizing calculations are now successful.
8.
Check the results. Open the "LP Flare" view, the stack height has been increased to 106m to meet the 4.7 kW/m2 at head height. The location of the maximum radiation point (at 2m of elevation) is displayed in the Max Radiation tab of "Grid @ Head Height". The location of this point is at 51m downwind as shown below.
Figure 2-17, Max Radiation Location
2-34
9.
Open the Radiation tab of "Elevation Grid" and select the plot option. The 4.7 kW/m2 isopleth is above head height (2m from ground).
10.
Finally open the Sterile Area tab under the "LP Flare" view. The 4.7 kW/m2 limit shows a distance indicating that this value is reached. This is due to the sterile area calculation using a different solver routine to the sizing calculation. Increase the radiation limit to 4.701 kW/m2 and recalculate to remove this discrepancy.
11.
This completes the stack sizing tutorial. Save the case as “Ex2 - Onshore - Sizing Results.fsw.
Getting Started
2-35
2.3 Using Shields Flaresim includes the ability to model shield sections that will protect specific locations from the flare radiation. The shield sections may model solid obstructions blocking all of the radiation or water curtains that provide a partial block. Two examples are presented here extending the base examples. For the offshore example, a welltest burner is added which requires the use of a water curtain shield to protect the platform. For the onshore example, a structure and its surroundings are modelled.
2.3.1 Offshore Case - Add Welltest Burner A welltest burner capable of burning 30,000 lb/hr of liquid is to be added to our design. 1.
Use the File - Open menu option or the icon. In the File Open dialog that appears, browse to the Samples sub-folder in the Flaresim installation folder (usually [Public Documents]\Softbits\Flaresim 4.0) select the file “Ex1 - Offshore Final Results.fsw” and click the Open button.
2.
Change the units preferences to “Field” in the Preferences view if required.
3.
In the Case Navigator view, select the Fluids branch and click the Add button to create a new Fluid and open its view. Complete the view with the following entries; Name = Welltest Liquid, Calculation Method = Flaresim Temperature = 100 ° F, Ref Pressure = 14.7psi Mole Weight = 52.9 , LHV = 19,550 btu/lb, Cp/Cv = 1.2, LEL = 1.7%, Saturation = 100%. 2-35
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Using Shields
The Tc and Pc fields can be left blank. 4.
In the Case Navigator view select the Stacks branch and then click the Add button to create a new Stack and open its view. Enter data for the new stack as follows, leaving other entries at their default values; Name - Welltest Boom, Location Northing = -200ft, Easting = 0ft, Elevation = 0ft, Dimensions section Length = 55ft, Angle to Horizontal = 0 deg, Angle to North = 180 deg. These entries define the new stack as a horizontal boom on the opposite side of the platform to the main flare stack.
5.
In the Case Navigator, select the Tips branch and click the Add button to create and view a new Tip object. Name it “Welltest Tip” and enter the following data; Details tab Tip Type = Welltest, Number of Burners = 3, Fraction Heat Radiated Method = User Specified Specified Fraction Heat Radiated = 0.3 All other values should be left at their defaults. Location & Dimensions tab On Stack = Welltest Boom, Length = 0ft, Angle to Horizontal = 0 deg, Angle from North = 180 deg. Exit Diameter = 4 in Note the burner length and orientation fields serve to locate the precise location of the flame and the initial flame
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Getting Started
2-37
direction. Even when the burner length is 0ft as here, the orientation fields must still be entered. Fluids tab Fluid = Welltest Liquid Mass flow = 30,000 lb/hr. 6.
Add a new Receptor Point in the usual way. Define the following data to locate the receptor point at the base of the welltest burner boom; Name - Base Welltest Boom, Northing = -200ft, Easting = 0ft, Elevation = 0ft. All other fields may be left at their default values. Close the view.
2.3.2 Offshore Case - Run Welltest Calculations 7.
In the Case Navigator view, select the Stack 1 object. Clear the Size This Stack check box. Now click the Ignore button. This will exclude the two tips on the main flare stack from the calculations.
8.
Run the calculations by clicking the large button labelled “Click to Calculate”. Check in the Errors/Warnings/Info log panel that the case has run and calculated correctly.
9.
Open the Receptor Summary view. The results show that the radiation limits for our original two critical locations that we have defined are met. The radiation at the base of the well test burner stack is 1405 btu/hr/ft2.
2.3.3 Offshore Case - Add Water Screen The radiation calculated at the base of the welltest burner stack is acceptable for brief exposure only. Since more extended exposure might be required, it is necessary to reduce the radiation. While this 2-37
2-38
Using Shields
could be achieved by extending the length of the stack this would be an expensive option due to the added weight. It is normal to reduce radiation from welltest burners using water screens. 10.
Add a Shield object, either by clicking the Shield branch in the Case Navigator view and then the Add button, or by using the Add - Shield menu option according to your preference.
11.
Enter data in the Details tab of the new Shield view as follows; Name = Water Curtain, Radiation - Type = Water Screen Radiation - Layer Thickness Calculation = User Radiation - Layer Thickness = 0.5 in Noise - Transmissivity = 1.0 [default]
12.
Select the Sections tab. The first section is already created for you. In the lower half of this view, click the Add Vertex button 4 times to create a rectangular shield section with 4 corners or vertices.
13.
Enter the following data; Name - Water Curtain Vertex 1 = Northing -205 ft, Easting, 50 ft, Elevation 40 ft Vertex 2 = Northing -205 ft, Easting, 50 ft, Elevation -10 ft Vertex 3 = Northing -205 ft, Easting, -50 ft, Elevation -10 ft Vertex 4 = Northing -205 ft, Easting, -50 ft, Elevation 40 ft Note it is a requirement when entering the locations of the vertices that each point is directly connected to the next point in the list as shown below. Flaresim will attempt to sort the points to meet this criteria if necessary.
2-38
Getting Started
2-39
Figure 2-18, Shield Section Input
14.
The Shield view should now show that the shield data setup is complete. Run the updated case and inspect the results. The radiation value at the base of the welltest burner stack has been reduced to an acceptable value of 264 btu/hr/ft2. The radiation isopleth for the Receptor Grid, Grid 1 clearly shows the effect of the shield, see Figure 2-19..
Figure 2-19, Isopleth plot for Helideck Plan View
15.
Save the case as “Ex3 - Shields - Water Curtain.fsw
2.3.4 Onshore Case - Workshop Surroundings After sizing the onshore flare to meet a radiation constraint at head height, we are now concerned about the surroundings of a workshop located in the vicinity of the stack. We will calculate the radiation 2-39
2-40
Using Shields
and temperature at a receptor located at the entrance of the workshop on the downwind side of the structure and study the shielding effects. 1.
Use the File - Open menu option or the icon. to open the file "Ex2 - Onshore Sizing Results.fsw" and click the Open button.
2.
If required, use the Preferences view to set the units to “European”.
3.
Add a new Receptor Point in the usual way. Define the following data to locate the receptor in the South-west direction from the flare base: Name = Workshop Entrance Northing = -111m Easting = -30m Elevation = 2m All other fields may be left at their defaults. Close the view.
4.
The resized flare with a new height of 106m will be used from this point onwards. Swap to rating mode as follows. Open the "LP Flare" view and disable the Size This Stack check box under the Details tab. Set the stack length to 106m. Click the Calculate button to run the model.
5.
Open the Workshop Entrance point to inspect the results. The radiation at the workshop entrance is 3.8 kW/m2. Note the surface temperature calculated which is 46 ° C. This equilibrium temperature value is based on the default material properties of the receptor which are appropriate for a steel plate 3mm thick exposed to radiation on one face. We will use these properties as representative of exposed equipment at the workshop entrance.
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Getting Started
2-41
2.3.5 Onshore Case - Add Workshop While the radiation received at the workshop remains below our sizing constraint of 4.7 kW/m2 it still exceeds the allowed limit for continuous exposure of 1.6 kW/m2 and the 3.2 kW/m2 allowed during emergency escapes. In order to predict the radiation at the point of interest with more accuracy we should account for the fact that the workshop will act as a shield protecting the receptor from radiation. 6.
Add a Shield object, either by clicking the Shields branch in the Case Navigator view and then the Add button, or by using the Add - Shield menu option according to your preference.
7.
Enter data in the Details tab of the new Shield view as follows: Name = Workshop Screen Type = Solid Note the Radiation Specified Transmissivity is automatically set to 0. This is the value expected for opaque materials such as concrete or metal. Noise Transmissivity = 1.0 [default]
8.
Move to the Sections tab. Click on the Make Pit/Hut button and enter the following data in the popup window: Select Hut radio button Length = 10m Width = 4m Height = 4m Northing = -105m Easting = -30m Elevation = 0m Click OK.
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Using Shields
This option automatically adds five sections to the shield: four walls and the roof. The Shield View status should now indicate that the shield is ready to calculate. 9.
Click the Calculate button and review the results. The radiation at the Workshop Entrance is now 2.0 kW/m2 which allows safe escape during an emergency.
10.
Open the “Grid @ Head Height” receptor grid and view the radiation isopleth plot. The shield sections representing the workshop will be shown on the plot but are rather small. Click the Zoom button and when the zoom cursor icon appears, click and drag around the workshop region. The expanded plot is shown below.
Figure 2-20, Grid Radiation Isopleth
This shows a symmetrical isopleth around the workshop which is unexpected given that the flare is to the North and East of the workshop. This result is due to the fact that the isopleth curves are calculated by interpolation from the points in the grid. These points are too far apart to allow an accurate calculation of the isopleths around the small workshop. 2-42
Getting Started
11.
2-43
To plot the isopleths around the workshop in more detail an additional receptor grid is needed. Copy this receptor grid and specify the following data in the new grid: Name = Workshop Surroundings Orientation = Northing - Easting Offset = 2m Northing Min = -115m Northing Max = -95m Northing Number of points = 41 Easting Min = -40m Easting Max = -20m Easting Number of points = 41 Click Calculate and inspect the radiation isopleths for the Workshop Surroundings grid. As shown below, this now reveals the expected lower radiation region to the South and West of the workshop.
Figure 2-21, Workshop Surroundings Isopleth
2.3.6 Onshore Case - Add Local Environment The workshop does not only protect the entrance area from radiation, it also protects it from the Northerly wind. This will reduce the convective cooling of exposed equipment and will result in higher equilibrium temperatures. We will extend our model to 2-43
2-44
Using Shields
include this effect by adding a local environment with 0 m/s wind speed for the workshop entrance receptor. 12.
Select the existing Environment in the Case Navigator and click the Copy button. Rename the new Environment "No Wind-No Solar - No Aten." Change the wind speed to 0m/s.
13.
The "9D" Environment was automatically ignored since only one can be active in the model. However we still want to use a 9m/s wind for the radiation calculations. Click on the Environment "9D - No Solar - No Aten." item in the Case Navigator and then click the Activate button.
14.
Copy the Receptor Point "Workshop Entrance" and rename the new one "Workshop Entrance - No Wind". Move to the Properties tab and change the Local Environment to "No Wind - No Solar - No Aten." Creating a copy of this point will allow us to compare the temperatures with and without the cooling effect of the wind.
15.
Run the case. Open the Receptor Summary view by double clicking on the Receptor Points branch in the Case Navigator and compare the temperatures of the two points. With the “No Wind” local environment the equilibrium temperature is 86 ° C as against 31 ° C with the base case wind speed of 9 m/s. While higher windspeeds often lead to higher radiation values due to greater flame deflection, this shows that studies of temperature should consider lower wind speeds if a receptor point is shielded from the wind. This result, at 0m/s wind speed, considers the worst possible case - it is likely that some wind will eddy around the workshop.
16.
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Save the case as “Ex3 - Shields - Structure”.
Getting Started
2-45
2.4 Using Overlays Flaresim provides Receptor Grid objects to visualise the thermal radiation around the flare. These calculate the radiation for a grid of points which are then used to generate isopleth charts showing lines of constant thermal radiation. Similar isopleth charts can be displayed for noise and surface temperature results. The usage of these has already been explained in earlier examples. The utility of these isopleth plots is greatly enhanced by plotting them on a plant drawing so that the radiation levels can clearly be identified at different locations.These examples show how two types of plant drawings, known in Flaresim as Overlays, can be integrated with isopleth plots.
2.4.1 Offshore Case - Flaresim Overlay The first type of overlay available for adding to isopleth plots are known as Flaresim overlays. These are generated using the internal overlay editor. In this example, we will create a simple plan view within Flaresim for integration with the receptor grid isopleth plot in our offshore example. 1.
Select the File - Open menu item or click the icon. Open the case “Ex3 - Shield - Water Curtain.fsw” which you should find in the folder [Public Documents]/Softbits/ Flaresim 4.0.
2.
In the Case Navigator, select the Overlay branch and click the Add button. A new overlay object called Overlay 1 will be created and displayed. Change the name to “Helideck Plan”.
3.
In the “Update Details From Grid” section of the Details tab, select the “Grid 1” grid and click Update. The Overlay dimensions are updated with those from the chosen grid.
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Using Overlays
4.
Select the Editor tab and click the zoom in
and zoom
out buttons to resize the view until you can see the full drawing. Check the Show Stacks check box to display the location of the stack in the drawing to act as a guideline. Note this will not form part of the drawing. 5.
Now click the Add Rectangle button and draw a rectangle to represent the platform outline from the top left corner [-200,0] to the bottom right corner [50,-200]. This is done by moving to the first point using the displayed X,Y coordinates at the left of the view as a guide, clicking and holding the left mouse button then dragging to the second point.
6.
Add a second rectangle to represent the helideck from the points [-50,-100] to [30, -180].
7.
Click the ellipse button and draw a circle within the helideck rectangle by moving to the point [-50, -100], clicking and holding the left mouse button and dragging to the point [30, -180].
8.
Click the text button and then click the drawing in the middle of the helideck circle. A vertical flashing bar will appear to indicate the text insertion point. Type the letter H and then hit the enter key to complete the text entry. If the text is too small, click the select button and then select the text you have just entered. A set of selection points will appear around it to indicate that it has been selected. Now click the properties drop down menu and select the Text Font option to open a standard font dialog to allow the text size and style to be defined. A size of around 24 pt is probably suitable. If required the selected text can also be moved by clicking the yellow dot and dragging with it the left mouse button - .
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Getting Started
2-47
The overlay picture is now complete and should look something like the view below. Figure 2-22, Completed Overlay
9.
Next open the “Grid 1” Receptor Grid and go to the Plot Overlay tab. Select the Use Flaresim Overlay radio button and then, in the drop down menu that appears, select the overlay we have just created, “Helideck Plan”. Finally tick the Show Overlay check box. Now go to the radiation tab. The overlay is now displayed as the background picture to the isopleth as shown below.
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Using Overlays
Figure 2-23, Isopleth with Overlay
10.
Save the case as “Ex4 - Offshore - Flaresim Overlay”. The overlay file we have created will be automatically saved in the Flaresim case folder (i.e. Ex4 - Offshore - Flaresim Overlay) with the file extension “.fso”.
2.4.2 Onshore Case - External Overlay File The other method of displaying an overlay with your isopleth plots is to link to an external graphics file. The best type of background drawing to import is a scaled vector drawing i.e. a Windows metafile (.wmf) or enhanced metafile (.emf). Bitmap files (.bmp, .png and .jpg files) can also be used. Given that the locations of the stacks etc. in your Flaresim model are matched to the drawing on import, the isopleths will be correctly positioned in relation to the drawing. The following example is based on the onshore example and shows how to import the plot plan of our facility as a .bmp file and integrate it with the radiation isopleths. 1.
2-48
Use the File - Open menu option or the icon. In the File Open dialog that appears, browse to the [Public Documents]/Softbits\Flaresim 4.0 folder. Select the file "Ex3 Shields - Structure.fsw" and click the Open button.
Getting Started
2.
We know that the drawing represents an area 400m long and 300m wide of our facility. The base of the "LP Flare" is located at the origin in the Flaresim model (0m, 0m). In the drawing this is 247.8m North and 179.2m East from the left bottom corner that we will assume is at 0m North and 0m East.
3.
Open the Plot Overlay tab of "Grid @ Head Height", ensure the Details radio button is selected in the External File Details section and enter the following values:
2-49
File Dimensions Northing Minimum = 0m Northing Maximum = 300m Easting Minimum = 0m Easting Maximum = 400m Location of Flaresim Origin in File Northing = 247.8m Easting = 179.2m 4.
Click the Browse button to import the background graphics file. The file to import is called Plot Plan.bmp and is located in the Samples\Ex4 - Onshore - External Overlay folder. You will need to select "Windows Bitmap (*.bmp)" in the "Files of Type" drop down in the File Open view to select this. Click Ok. You can now click the Preview File radio button to see the imported graphic file together, with a blue outline rectangle which shows the extents of the current grid on the drawing.
5.
Reselect the Details radio button and make sure the Show Overlay check box is enabled. Hit the Calculate button and move to the Radiation tab. You should see your overlay displayed together with the isopleths as shown below.
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Using Overlays
Figure 2-24, Onshore Case - External Overlay File
6.
Save the case as “Ex4 - Onshore - External Overlay”.
The key aspects to the success of this process is the accurate understanding of the dimensions of the overlay file and the location of the flare stack within it. So for example if it was known that the Plot Plan bitmap covers the dimensions 150m to 450m N and 100m to 500m E, then the flare stack would be at 397.8m N and 279.2m E and this is the information that must be entered. Be aware that if there is white space surrounding the drawing, this forms part of the drawing and its extent must be included in the drawing dimensions and the determination of the flare stack location.
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Getting Started
2-51
2.5 Case Study A new feature of Flaresim 4.0 is the ability to define one or more case study objects. These allow the selection of input variables and definition of alternate input values. A list of key result variables is also selected. When the case is calculated, each case study will be run, automatically updating the model with the different input data values and recording the key result variables selected. The results showing their variation with changes in input values are then available as a table or as a plot. Two types of Case study can be defined: discrete variable studies based on single input values and incremental variables studies based on the variation in input values over a range. Examples of both types are given here.
2.5.1 Offshore Case - Discrete Variable Case Study In this example a discrete variable case study will be added to the offshore example to compare the performance of the base case design under different design assumptions and wind direction. 1. Open the case “Ex4 - Offshore - Flaresim Overlay.fsw” which can be found in [Public Documents]/Softbits/ Flaresim 4.0/Samples. This case is configured for running the welltest burner calculations and needs reconfiguring for rating calculations on the main stack 2.
Select the Stack called “Welltest Boom” in the Case Navigator and click the Ignore button.
3.
Open the view for “Stack 1”. Clear the check box labelled Size this Stack” and set the stack length to 90 ft, the final size calculated in the Ex1 sizing example. Finally, clear the Ignored check box to activate calculations for the stack.
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Case Study
4.
Select the Shield called “Water Curtain” in the Case Navigator and click the Ignore button.
5.
Run the case and open the Receptor Points summary view to confirm that the radiation values for the Stack Base and Helideck are 1494 and 574 btu/h/ft2 respectively.
6.
Click the Case Studies branch in the Case Navigator and click the Add button. In the Case Study view that opens, ensure that the Study Type radio button “Study Discrete Variables” is selected. Enter a name for the case study as “Radiation Case Study”.
7.
Click the Add Variable button. In the variable browser window that appears, select the following options in the Select Variable view as shown below. Object = Environment Name = Environment 1 Variable = Wind Direction Then click the Add button
Figure 2-25, Case Study Variable Selection
8.
2-52
The variable browser will stay open. Select two more variables as follows, clicking the Add button after each one.
Getting Started
2-53
Object = Environment Name = Environment 1 Variable = Use Solar Radiation Object = Environment Name = Environment 1 Variable = Transmissivity Method After selecting the final variable click the Cancel button to close the Variable select view 9.
Click the Add Case button 4 times. The discrete variable input grid will now have 5 rows, all set to the current model values for the variables selected. Edit the input values for each case to read Wind Direction
Case
Use Solar Radiation
Transmissivity Method
Case 0
0
No
User Specified
Case 1
0
Yes
User Specified
Case 2
0
No
CalcNoLimits
Case 3
0
Yes
CalcNoLimits
Case 4
90.0
No
User Specified
10.
Select the Case description entries one by one and edit the default name (Case 0 etc) to more descriptive names: Base Case inc Solar inc Transmissivity inc Solar + Trans Cross Wind
11.
Select the Result Variables tab and click the Add Variable button. Using the Select Variable view that appears, select the following two variables
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Case Study
Object = Receptor Point Name = Stack Base Variable = Radiation Object = Receptor Point Name = Helideck Variable = Radiation Finally close the Select Variable view. 12.
At this point the status display for the Case Study should indicate that it is ready to calculate. Click the Calculate button. Check in the status panel that the Case Study calculations have run. If not, check that they are enabled in the Calculation Options view.
13.
Open the Results tab of the Case Study view to see the summary of the input values used and the corresponding radiation values calculated. This table can be exported to Excel or a .CSV file by clicking the Export button for easy inclusion in a report.
14.
Click the Plots tab. In the Variables grid, select the two radiation results variables by clicking the check boxes adjacent to them. Select the variable name cells and edit them to shorter names: Stack Base Helideck
2-54
15.
In the Cases grid select all the cases. A bar chart allowing comparison of the results will be generated. Expand this as required to allow the full name of the cases to be displayed. The generated plot is shown in Figure 2-26 below
16.
Note it is possible to display the bar chart horizontally by clicking the Horizontal Chart check box. This can provide a more readable plot when multiple cases with longer names must be displayed.
Getting Started
17.
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Save the case as “Ex5 - Offshore Casestudy - Discrete Variables”.
Figure 2-26, Radiation Case Study Plot
2.5.2 Onshore Case - Incremental Variable Case Study In this example we will extend the onshore model to use a Case Study with an incremental variable. This generates a downwind line plot of radiation vs distance at personnel head height. 1. Open the case “Ex4 - Onshore - External Overlay.fsw” which can be found in [Public Documents]/Softbits/ Flaresim 4.0/Samples. 2.
The first step is to add a new receptor point at 0m Northing and 2m of elevation (head height). This is the starting point of the radiation downwind line plot. Enter the following data:
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Case Study
Name = Receptor Downwind Northing = 0m Easting = 0m Elevation = 2m All other fields may be left at their default values. Close the view. 3.
Add a Case Study object, either by clicking the Case Studies branch in the Case Navigator view and then the Add button, or by using the Add - Case Study menu option according to your preference.
4.
Enter data in the Input Variables tab of the new Case Study view as follows: Name = Rad. vs Dist. DW @ Head Height Study Type = Study Incremental Values
5.
To add a new variable click on or alternatively hit the Add Variable button. In the Select Variable view choose: Object = Receptor Point Name = Receptor Downwind Variable = Location Northing Click the OK button.
6.
Enter these values below to customise the plot range and number of points for the x axis - distance: Active = Yes Minimum Value = -200m Maximum Value = 0m Number of Points = 21 Note that the Step size will be automatically updated to 10m. Alternatively a Step Size can be specified and the Number of Points will be calculated.
2-56
Getting Started
7.
2-57
Move to Result Variables tab and add a new variable by either clicking on or hitting the Add Variable button. In the Select Variable view choose: Object = Receptor Point Name = Receptor Downwind Variable = Radiation Click the OK button. The Status bar change to green indicating that the object is ready to run.
8.
Before running the case we will ignore the Workshop shield since it is not relevant now. This will speed up the calculations. Run the case from the main Calculate button.
9.
The calculated profile of radiation vs distance downwind the flare stack centre line is displayed on the Results tab table.
10.
Finally move to the Plots tab and select the “Receptor Downwind: Location Northing” as the X variable and “Receptor Downwind: Radiation” as the Result variable. to generate the plot.
11.
Double click on the variable descriptions and edit the text to shorter values such as “Downwind Distance” for the Xvariable and “Radiation” for the result variable. The final plot is shown as Figure 2-27 below.
12.
Save the case as “Ex5 - Onshore Case study - Incremental Variables”.
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Case Study
Figure 2-27, Downwind Radiation Plot
2-58
Getting Started
2.6
2-59
Dynamics
Flaresim 4.0 includes a new feature that allows dynamic calculations of flare system results. A curve of flow against time for each tip may be defined and results generated for the defined receptor points which show how radiation, temperature and noise vary with time. Dynamic analysis is particularly useful when considering systems that have more than one tip flaring and when the peak flows to each tip are not occurring at the same time.
2.6.1 Offshore Case Analysis of the Case Study results for the offshore case in section 3.5.1 showed that inclusion of solar radiation caused the radiation limits at the stack base to be exceeded. Inclusion of the calculated transmissivity option reduced the extent to which the limit was exceeded but the results still show a value of 1605 btu/h/ft2 as against the original design limit of 1500 btu/h/ft2. In our original design we neglected solar radiation on the assumption that the flaring duration is short. We will now use dynamic analysis to test this assumption and see for how long the radiation limit is exceeded with these new environmental assumptions. 1. Open the case “Ex5 - Offshore Casestudy - Discrete Variables.fsw” from the folder [Public Documents]/Softbits/ Flaresim 4.0/Samples. 2.
Open the Case Study object “Radiation Case Study” and move to the Results tab. Double click on the row in the table labelled “inc Solar + Trans”. A pop-up window will appear asking you to confirm that you wish to copy the values for this case to the main model. Click Ok.
3.
Open the view for “Environment 1”. Confirm that the Wind Direction is 0, the Include Solar Radiation check box is ticked and the Transmissivity method is set to “CalcNoLimits”. 2-59
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Dynamics
4.
Click the Calculate button. Open the Stack Base receptor point and confirm that the radiation is 1605 but/h/ft2.
5.
Open the tip view “Sonic Tip” and click the open its Tip Dynamics view.
6.
Enter the following flow against time for this tip on the Input Data tab.
button to
Flow Basis = Mass Interpolation Basis = Linear. Time s
Flow lb/hr 0
0.0
5.0
90,000.0
10.0
90,000.0
60.0
66,000.0
100.0
44,000.0
300.0
11,000.0
900.0
0.0
Note the table will have a single blank row at the start. Additional rows will be added automatically as you enter the data. If you miss a row, it can be added at the end of the table; the data supplied will be sorted into time order when the case is calculated. 7.
Open the tip view for “Pipe Tip”, click the button to open its dynamics view and define the following data. Flow Basis = Mass Interpolation Basis = Linear.
2-60
Getting Started
Time s
8.
2-61
Flow lb/hr 0
0.0
20.0
0.0
30.0
10,000.0
50.0
10,000.0
300.0
2,200.0
900.0
2,200.0
You are now ready to run the case with the dynamics calculation options. Open the Calculation Options view and ensure the “Run Dynamics” check box is selected. Click the Calculate button
9.
When the calculations are complete, check the Errors / Warnings log. You should see entries indicating the start and completion of dynamics calculations.
10.
Open the “Stack Base” receptor point and click the button to open the receptor point dynamic view. On the Results tab, check the radiation levels. The peak value is 1536 btu/h/ft2 at 30 s.
11.
Open the Tips Summary view by double-clicking the Tip branch header in the Case Navigator. Select the Dynamics results tab and to see the flow vs. time profile for both tips. Select the Mach number option to confirm that the flow through the Sonic tip. This is due to the “Calculate burner opening” option being active for the Sonic tip. This is appropriate for a “variable slot” sonic tip design but will not apply to all tips.
12.
The default time resolution for our dynamics results is a little coarse at 10 s intervals. Open the Calculation Options view and select the Heat Transfer tab. 2-61
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Dynamics
Change the Dynamics Exposure Time to 200s and the number of points to 200. This will allow analysis of the initial period of flaring at 1 s intervals. Click the Calculate button. 13.
The “Stack Base” dynamic results now show that the radiation limit of 1500 btu/h/ft2 is exceeded for the period 29s to 40s.
14.
Select the Receptor Points summary view by double clicking on the Receptor Points branch header in the Case Navigator. Select the Dynamic Results tab to see a summary of all the receptor point results as they vary with time as tables or plots. The radiation plot is shown below.
Figure 2-28, Dynamic Radiation Results
These results show how the radiation rises and then begins dropping as the flow to the sonic tip passes its peak at around 20 s. The radiation then rises again as the flow from the pipe tip rises.
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Getting Started
2-63
The dynamic analysis has shown that the peak radiation values are of short duration. However any decision as to whether the total radiation experienced would be acceptable should consider the full duration of the flaring event. For example, the plot above shows radiation values at the Stack Base remaining above 1000 btu/h/ft2 for approx 170 s. 15.
Still in the Receptor Points Summary view, select the Temperature result. The curves show that the temperature is continuing to rise at the end of the exposure time (200s).
16.
To see the peak temperatures, open the Calculation Options view and select the Heat Transfer tab. Change the Dynamics Exposure Time to 800s. Then recalculate.
17.
Inspecting the temperature results in the Receptor Points Summary view now shows that a peak in temperatures is reached around the 190s to 240s period.
Figure 2-29, Receptor Point Summary, Peak Temperature Results
18.
Save the case as “Ex6 - Offshore Dynamics”.
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2-64
Gas Dispersion
2.7 Gas Dispersion Flaresim includes two types of gas dispersion model intended for two different types of analysis A jet dispersion calculation models dispersion of flared fluid close to the tip, to identify the potential for dangerous gas concentrations in flame out conditions. A Gaussian dispersion calculation models dispersion of flared fluid or combustion products over longer distances. The aim of this section is to illustrate how to use each of these models.
2.7.1 Objective and Data A new case with the following data will be used. Flared Fluid Methane Ethane H2S Temperature Ref Pressure Flow
0.9 mole frac 0.08 mole frac 0.02 mole frac 75 ° C 1.013 bar a 50000 kg/hr
Mechanical Data Tip Type Tip diameter Tip length Stack location Stack length Stack orientation
Pipe 387.4mm (15.25in) 1m At origin, 0, 0, 0 20m Vertical
Environment Data Temperature Wind
2-64
15 ° C 10 m/s from North
Getting Started
2-65
Our objective will be to analyse the gas dispersion around the flare in normal operation and flame out conditions.
2.7.2 Load or Create Base Case 1.
If you wish to build the case from scratch then, either select the File - New menu option, or click the icon in the tool bar. The Setup Wizard will appear. Select the European units set on the opening page for easy of entering the remaining data. Work through the Fluid, Tip, Environment and Stack tabs entering the data defined above. Once you have entered the Stack data, you can click the Finish button to accept the default data for Receptors and Calculation options. Skip to step 3.
2.
Otherwise use the File - Open menu option or the icon. In the File Open dialog that appears, browse to the Samples sub-folder in the Flaresim installation folder (usually [Public Documents]\Softbits\Flaresim 4.0) select the file “Ex7- Starter.fsw” and click the Open button.
2.7.3 Jet Dispersion Calculation In this exercise we run a jet dispersion study to study the flammable gas concentrations around the flare in the event of a flame out. 3.
Before enabling the jet dispersion calculations, we will create a new Receptor Grid to see the results more clearly. Select the Receptor Grid branch in the Case Navigator and click the Add button. In the new view enter the following data. Name = Elevation Grid Plane = Elevation-Northing Grid Offset = 0m Elevation Minimum = -100m Elevation Maximum = 300m
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Gas Dispersion
Northing Minimum = -300m Northing Maximum = 100m Leave remaining values at defaults. 4.
Open the Calculation Options view by selecting it in the Case Navigator and clicking the view button. Select the check box labelled Jet Dispersion in the Include Options section of the General Tab. Click the Calculate button. The background of the Errors/ Warnings log will be yellow indicating a warning message. Checking this it warns of the jet interacting with the ground at a distance of 2152m. This is not a problem.
5.
Return to the view for your Elevation receptor grid and select the Concentrations tab. You should see a result that looks something like that shown below.
Figure 2-30, Jet Dispersion Initial Result
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The jet dispersion calculation shows the concentrations of the flare fluid in the event of a flame out and is useful for establishing the regions in which a flammable gas concentration may be obtained. At first sight, the result above looks unrealistic since the concentration isopleths do not appear connected to the flare tip. This is a function of the limited number of points calculated in the default grid. 6.
In your Elevation grid view, go to the Extent tab and set the number of calculated points to 51 for both Elevation and Northing dimensions. Click the Calculate button again. Return to the Concentrations tab and you should see a more accurate result. Save the case as Ex7 - Jet Dispersion.fsw.
2.7.4 Gaussian Dispersion, Contour Plot In this exercise we will study the dispersion of H2S from the flare tip in the event of a flame out. 7.
Create a Dispersion Object by selecting the Dispersion branch in the Case Navigator and clicking the Add button. In the Dispersion view enter the following data on the Input Data tab as shown below. Name = H2S Contour Pollutant Source = Unburnt Flared Fluid Calculation Type = Contour Plot Contours Height = 0m Northing Minimum = -1000m Northing Maximum = 0m Easting Minimum = -500m Easting Maximum = 500m Number of points, Northing and Easting = 41
8.
On the Pollutant Data tab, select the H2S component only. For a contour plot, only one component can be selected.
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Gas Dispersion
9.
Open the Calculation Options view and select the Gaussian Dispersion check box to enable these calculations. Click the Calculate button
10.
Select the Results tab and then the Plot option for the display. The plot shows the ground level concentration contours for H2S downwind of the stack as shown below
Figure 2-31, H2S Contour Plot
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The results shown have been calculated at the default environmental conditions. Atmospheric stability is characterised as Class D with dispersion coefficients applicable to Rural terrain around the flare. Open the Environment view at the Dispersion Data tab and test the effect on the dispersion results as you change the Atm. Stability class from A (most turbulent) to F (most stable) and the effect of changing the terrain from Rural to Urban.
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You will see that the H2S concentrations are higher closer to the flare when atmosphere is more turbulent and when urban terrain classification is used. The sensitivity of the results to these parameters shows the necessity of selecting the appropriate environment settings for your particular flare location. Save the case as Ex7 - Gaussian Dispersion - Contour.fsw
2.7.5 Gaussian Dispersion, Line Plot In this exercise we will consider the downwind concentrations of pollutants in the combustion gases of the flare when it is operating. 12.
In the Case Navigator select the Dispersion branch and click Add to create a new dispersion object. In the Input Data tab of its view enter the following data. Name = Combustion Emissions Pollutant Source = Combustion Gas Calculation Type = Downwind Line Plot Line through Point = Origin Height for Calculation = 0m Downwind Distance Minimum = 0m Downwind Distance Maximum = 10000m Number of points = 41
13.
Select the Pollutant tab. Select the SO2, NO, CO and Methane pollutants for calculation by checking the box alongside these components. Some of the components in this list, the CO2, H2O, SO2 are calculated directly from combustion of the components in the flared gas. The Fluid view, Combustion Results tab shows the stoichiometric fraction of each of these components generated by combustion of the flared gas. The remaining components, NOx (assumed as NO), CO and unburnt hydrocarbon (assumed as CH4) are calculated as typical emissions resulting from hydrocarbon combustion. 2-69
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Gas Dispersion
The quantities of each component generated is calculated by default, using the global basis defined on the Calculation Option view Emissions tab. Alternatively in Expert Mode, the emissions basis for each Tip can be specified on the Emissions tab of the Tip view. The quantities of each component in the combustion gases for each Tip are displayed on the Combustion Results tab of the Tip view. 14.
Since the dispersion of the combustion gases will be dependent on the flame temperature, we will now set this. Open the Tip View and select the Fluids tab. At the bottom of this view you may input a value for the flame temperature or clear the specified value to allow it to be calculated from the specified combustion air ratio. Set the Combustion Air ratio to 3.0 and clear the specified flame temperature.
15.
Open the Environment view and set the Atm. Stability Class to PasquillB. Click the Calculate button.
16.
Return to the Combustion Gas Results tab of the Tip view to see the calculated flame temperature of 721 ° C and the combustion gas compositions. In the Combustion Gas dispersion view, go to the results page and select the plot result to view the results as shown below. The peak concentration of SO2 is calculated at 67 µg/m3 at a distance of approximately 1500m downwind of the flare tip.
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Figure 2-32, Combustion Gas Dispersion Downwind Plot Results
17.
As in the previous example, open the Environment view to the Dispersion Data tab and test the effect of changing the Atm. Stability Class and Terrain class settings. You will find that for stable atmospheric conditions, stability classes E and F, the emission concentrations are still rising at the maximum downwind distance we have defined (10,000m). If you wish you can increase the maximum downwind distance on the Input Data tab to calculate the results further downwind. Save the case as Ex7 - Gaussian Dispersion - Downwind.fsw
2.7.6 Dispersion Analysis Comments It is worth making the following general comments on the dispersion analysis capabilities of Flaresim.
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Gas Dispersion
The jet dispersion analysis for flammable gas concentrations is based on the Cleaver & Edwards jet dispersion model. This is regarded as a reasonable model for concentrations close to the source. However it does assume dispersion in “free air” and does not consider the effect of structures that might modify dispersion patterns and lead to higher concentrations of flammable gas than predicted by Flaresim. A more detailed analysis with specialised software would be required in these situations. The Gaussian dispersion calculation for combustion gases and flared fluid over longer distances, is a simpler theoretical model that does not include detailed terrain effects. As such it should be considered as suitable for screening calculations to indicate a possible need for more detailed analysis. Chapter 11 has additional comments on the implementation of the Gaussian dispersion model in Flaresim.
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2.8 KO Drum This tutorial shows how to design a new KO Drum using the sizing mode. We will then adjust this preliminary design to fit the manufacturer available sizes and run a rating calculation to confirm this new design meets the sizing criteria.
2.8.1 Initial Sizing In this section we will calculate the required vessel dimensions (length and diameter) to separate liquid droplets larger than 300µm from the gas stream. The drum will also have to provide sufficient volume to accommodate a 30 min emergency release. The vessel will be horizontal with Ellipsoidal (2:1 elliptical) heads. 1.
Use the File - New menu option or the new case. Close the Wizard view.
icon to create a
2.
Add a KO Drum object, either by clicking the KO Drums branch in the Case Navigator view and then the Add button, or by using the Add - KO Drum menu option according to your preference.
3.
Enter this information in the Fluid Data tab: Name = KO Drum - Prelim. Gas Mass Flow = 75000 kg/h Liquid Mass Flow = 15000 kg/h Pump Out Mass Flow = 0 kg/h Fluid Property Source = User Specified Gas Density = 3 kg/m3 Gas Viscosity = 0.01 cP Liquid Density = 500 kg/m3 Note that the fluid properties can also be calculated from a specified fluid composition using the REFPROP thermo package.
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KO Drum
4.
Move to the Vessel Data tab and change the Initial Liquid level to 15% (this accounts for the slop and drain volume). Leave the other fields at their default values. Note that either L/D or diameter can be specified. The former is more common in new designs.
5.
Now open the Nozzle Data view to input: Inlet Nozzle Use Nominal Diameter = No Design Velocity = 10 m/s Schedule = STD Outlet Nozzle Use Nominal Diameter = No Design Velocity = 20 m/s Schedule = STD Note Nominal Diameter automatically changes to when the Use Nominal Diameter option is set to No. Normally the KO Drum nozzles are sized to meet velocity constraints. The values used here are based on common engineering practises. Alternatively the nozzle diameter can also be specified.
6.
Go back to the Vessel Data tab and click on the Calculate button at the bottom of the KO Drum view. This option allows generating results for the KO Drum object without the need of calling the main calculations. Another local Calculate button can be found under the Fluid Data tab. Although we are creating a case containing only KO Drum objects, it is possible to add KO Drum objects to any Flaresim model. KO Drum calculations are also performed when running the case from the general Calculate button.
7.
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The drum dimensions are displayed in the Vessel Data view. Now move to the Results tab to inspect the Operating and Separation output data. Flaresim has sized a vessel of 2.45m
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in diameter and 7.35m in length in order to meet the constraints: 300µm droplet size and sufficient holdup to accommodate the volume during a 30 min emergency relief. The resulting liquid level of 48.5% is below the 75% limit which indicates that the particle size is the controlling constraint in this initial design.
2.8.2 KO Drum Rating Based on the manufacturer available sizes, we will now adjust the initial design dimensions presented in the previous chapter and recalculate in rating mode to recheck if the new design still meets the sizing criteria. 8.
Copy the existing KO Drum object and rename the new one "KO Drum - Final".
9.
Move to the Vessel Data tab and select Rating in the Calculation Type drop down. Note that the Vessel Input Data section has changed to display the Rating parameters. Input the following values: Tan Tan Length = 7m Diameter = 2.5m Liquid Level = leave blank Rest of fields as default
10.
Update the Nozzle Data as below: Inlet Nozzle Use Nominal Diameter = Yes Outlet Nozzle Use Nominal Diameter = Yes When the Use Nominal Diameter option is set to Yes, any existing Internal Diameter is used to set the Nominal diameter to the nearest available nominal size in the selected schedule. The exit velocity is then updated.
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KO Drum
In our case the inlet nozzle nominal diameter is selected as 38in and updated nozzle velocity is 9.9 m/s. For the outlet nozzle the nominal diameter is 28in and the calculated velocity is 18.5 m/s. 11.
Rerun the calculation from the local button in the Vessel Data view. The minimum droplet size has increased slightly to 319µm whereas the liquid level remains at 48.5% allowing an extra 25 min holdup. This new design presented in Figure 2-33 is regarded as acceptable.
12.
Save the case as “Ex8 - KO Drum”
Figure 2-33, KO Drum Results
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3 Interface Page 3.1
Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.2
Menu Bar. . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.3
Multiple Case Views. . . . . . . . . . . . . . . . . . 11
3.4
Tool Bars. . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.4.1 3.4.2
Main Window Tool Bar . . . . . . . . . . . . . . . . 12 Case View Tool Bar . . . . . . . . . . . . . . . . . . 13
3.5
Log Panels . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.6
File Dialogs . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.6.1 3.6.2 3.6.3 3.6.4
File Save Dialog . . . . . . . . . . . . . . . . . . . . . File Open Dialog. . . . . . . . . . . . . . . . . . . . . Recent Files Menu . . . . . . . . . . . . . . . . . . . Update Messages During File Open . . . . .
16 18 19 20
3.7
About View . . . . . . . . . . . . . . . . . . . . . . . . . 21
3.8
Radiation Limits View . . . . . . . . . . . . . . . . 22
3.9
Flaresim Update View . . . . . . . . . . . . . . . . 23
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The Flaresim interface has been designed to give you a great deal of flexibility in the way in which you enter, modify and view the data and results which comprise your flare models. This chapter describes the various components of the Flaresim interface. If you need help with any particular task, the on-line help can give you step-by-step instructions.
3.1 Terminology The following view of the Flaresim screen shows most of the interface components that you will encounter. Figure 3-1, Flaresim Screen
Popup menu
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Terminology
Menu Bar The menu bar provides access to various program functions that are not specific to a particular Case. The options are described in more detail in section 3.2. Tool Bars The tool bar is a row of icons that provide quick access to the more commonly used program functions. Flaresim has one tool bar for the main program and each Case has a tool bar with options specific to it in the Case Navigator. The options are described in more detail in section 3.4.
Throughout the manual, Clicking a button or other item means using the Left mouse button unless stated otherwise.
Multiple Case Views Flaresim 4.0 allows multiple individual cases to be open at once for easier comparison and switching between different models. The multiple case views are managed using standard Windows conventions. Case Views may be expanded to full screen if required. Case Navigator The Case Navigator provides a summary view of all of the objects in a Flaresim Case displayed in a tree structure. It also provides a local tool bar of program options that are specific to the case as well as buttons to access various program functions such as adding, deleting, copying, viewing, activating and ignoring objects as well as starting calculations. Active Button Buttons appear on most forms and may be clicked with the left mouse button to perform the action indicated. Active buttons are those where the label type is black. Greyed Button Buttons which have an action that cannot be performed at a particular time are displayed with the label type in grey. File Message Log This area of the Case View displays a record of file saving and retrieval activity. See section 3.5 for more information.
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Errors / Warnings Log This area of the screen displays a record of error messages, warning messages and other information generated by Flaresim calculations. See section 3.5 for more information. PopUp Menu PopUp menus are used to display additional choices in response to clicking buttons or clicking the right mouse button. View This is the term used to describe a window containing a group of data entry fields for a specific element of the program. Views in Flaresim are generally non-modal which means that multiple views can be open and used at the same time. Views may be resized, minimised, maximised and moved within the Flaresim Case View in the same way as standard windows. Status Text Many views have a status field at the bottom to indicate whether all the necessary entries have been made. The background to this text indicates the status, green indicates ready to calculate, red indicates missing data, yellow indicates that the object is ignored. Tabs Some views have more data entry items than will fit on a typical size window. Tabs are a way of subdividing the entries into groups within the view. Clicking a tab heading displays the group. Input Tables The majority of data for Flaresim cases is entered through Input Tables. These group together related items which may either be values with associated units, drop down selection menus, check boxes or simple text. Generally the values entered will be checked for validity on leaving each cell in the Table. Value With Units Input items with associated engineering units are entered through a pair of Input Table cells, the first defining the unit, the second the value. 3-5
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Terminology
The units initially displayed by an Input Table are the default units defined through the Preferences View, see section 4.4. The current units for an individual value can be reselected at any time to display the value converted to that unit. The current displayed unit will be used to convert any number input to the internal units used by Flaresim. When an Input Table is completely refreshed e.g. following a calculation, the default units will be displayed again. This allows values to be entered in a mixture of units. For example in a field expecting a wind speed value when the default unit display is ft/s you can enter a value of “20 mph” by first changing the displayed unit to “mph” and then entering the value of 20. The displayed unit will be reset to “ft/s” and the converted value of 29.33 ft/s will be displayed when the Input Table is next refreshed. All new values are checked as they are entered to ensure that they lie between minimum and maximum values. The range limits used are intended to prevent entry of unreasonable values that would cause calculations failures but are relatively broad to allow maximum flexibility in the use of Flaresim. The fact that any given value falls within the range allowed by Flaresim does not mean that the value is appropriate for any given calculation - the validity of the values entered is the responsibility of the user. Drop Down List Box This type of edit box provides a downward pointing arrow to the right which may be clicked to allow a choice to be made from a set of options. Check Box A check box is used to select options that can be either on or off. Clicking a check box once will display a tick in the box indicating that the option is on, also known as setting the check box. Clicking the box again will clear the tick indicating that the option is off. Radio Buttons Radio buttons are used to select one option from a group of mutually exclusive options. Clicking one radio button in a group will select that option and automatically deselect all the other options. 3-6
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Scroll Bars Where a list or a view is not large enough to display all the items required scroll bars will appear. The up and down arrows may be clicked to move through the view to display all the items.
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Menu Bar
3.2 Menu Bar Figure 3-2, Menu Bar
The Menu Bar provides access to the Flaresim program actions. The row of main menu items at the top of the main Flaresim window provides access to drop down menus as shown in Figure 3-2. Main menu items are selected by clicking on them or by holding down the Alt key and first letter of the menu name. Once the submenu has opened the sub-menu items can be selected by clicking them or by using the up and down arrow keys and then hitting enter. Menu items may also have a shortcut key combination displayed against them which can be used to select the action without using the menu. Flaresim provides the following menu items.
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Interface
Main Menu File
Windows
Sub Menu
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Description
New
Creates a new Flaresim case
Open
Loads a Flaresim case from disk
Save Case
Save current selected case
Save As
Open save file dialog to save current selected case with a new name.
Save All
Saves all open cases to disk
Print Report
Create report for current selected case
Select Graphic Report Printer
Display printer dialog to select the printer that will be used to output graphic reports. Selection will be remembered if appropriate option is set in Preferences.
Graphic Report Page Settings
Displays dialog to select page size and margins for graphic report output.
Print Graphic Report
Open graphic report view for current selected case.
Preferences
Opens the Preferences view
Exit
Quits the Flaresim program
Recent files
List of recently opened files that can be reopened directly by selecting the name.
New Window
Creates a new Flaresim case
Cascade
Organises the open case views into a cascade of overlapped windows
Tile Vertical
Organises the open case views into a set of side by side windows
Tile Horizontal
Organises the open case views into a set of stacked windows
Close All
Close all case views
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Menu Bar
Main Menu
Help
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Sub Menu
Description
Arrange Icons
Organises icons for minimised case icons
Open Windows
List of currently open case views
Contents
Opens Flaresim help file at contents page
Index
Opens Flaresim help file at index
Search
Opens Flaresim help file in search mode
Radiation Limits Info
Displays an information window showing common radiation design limits
Technical Support
Displays information on sources of technical support
Check For Updates
Checks whether an update to the current version is available
About
Version information about Flaresim
Interface
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3.3 Multiple Case Views Flaresim 4.0 allows multiple cases to be open at once. Each case will have its own view window that will be contained within the main Flaresim window. A new case can be created at any time using the File - New menu item or by clicking the tool bar button. A an existing case opened by using the File - Open menu item or clicking the tool bar button. Once open an individual Case View can be minimised, maximised or closed using the standard set of window control buttons display in the top right of the window. Clicking the button of this set minimises the case view to just an icon at the bottom of the Flaresim view. In the icon view the left button changes to and clicking this restores the case view to its previous size. Clicking the button maximises the case view to the full size of the Flaresim window, covering any other case views that might be open. Again the button will be replaced by a button and clicking this will restore the standard window size. Finally the button will close the case. The Preferences view, Files and Options tab includes an option which controls whether new cases and freshly opened cases are automatically display at the maximised size. The Windows menu (see above) provides a list of the currently open cases and allows rapid switching between them. It also provides options for arranging the case view windows on the screen.
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Tool Bars
3.4 Tool Bars A Tool Bar provides a row of icons that may be clicked to provide rapid access to some commonly used actions. Flaresim has tool bars in both the main Flaresim window and the Case Views.
3.4.1 Main Window Tool Bar Flaresim provides these options on the main window Tool Bar. This icon creates a new Flaresim case. This icon retrieves a Flaresim case from disk. This icon saves the current selected case. If the case has an name and has already been saved it will be overwritten. If it is a new case a File - Save As dialog will open. A message indicating success or failure will be written to the File Management Log. This icon saves the current selected case with a new name. A File - Save As dialog will open to allow the file name to be specified. A message indicating success or failure will be written to the File Management Log. This icon saves all open Flaresim cases to the disk. This icon opens the Report View for the current selected case and to allow printing of the case. This icon opens the Print Graphic Report View to allows selection, saving or printing of the graphic reports for the current selected case. This icon opens the Preferences view.
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3.4.2 Case View Tool Bar Flaresim provides the following options on the Case View tool bar at the top of the Case Navigator.
This large button starts the calculations for the case. Once started, the button displays a progress bar for the calculations. On completion the background colour shows the status of the calculation results, green for success, red for failure. A pale orange background indicates that data has changed since the last calculation. This icon opens a drop down menu offering a list of objects that can be added to the case. It is equivalent to selecting the object type branch in the Navigator tree view and clicking the Add button. This icon saves the case. If the case has an name and has already been saved it will be overwritten. If it is a new case a File - Save As dialog will open. A message indicating success or failure will be written to the File Management Log. This icon saves the case with a new name. A File - Save As dialog will open to allow the file name to be specified. A message indicating success or failure will be written to the File Management Log. This icon opens the Report View to allow selection of the print options for the case and to allow printing of the case. This icon opens the Print Graphic Report View to allows selection, saving or printing of the graphic reports for the case.
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Tool Bars
This icon collapses the Case Navigator into a summary view that consists of a vertical tool bar. This icon stops the calculations. It is only visible while calculations are running. Vertical tool bar buttons in the Case Navigator summary are the same as in the standard Case Navigator with the following additions. This icon expands the Case Navigator to its normal size. This icon starts the calculations for the case. The colour of the tool bar background indicates the case status, green for calculated with results available and pale orange for not calculated. This icon displays a pop up menu of the objects in the current case. Selecting an object will display its view.
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3.5 Log Panels Figure 3-3, Log Panels
The log panels at the bottom of the Flaresim main window are used to output messages from the program. There are two panels. The left panel is known as the File Message Log and records details of file creation, file retrieval and file saving actions. The right panel is known as the Errors/Warnings Log and records messages generated by Flaresim as it calculates. Once calculations are complete the background colour of the panel shows the calculation status:• Green - Calculations completed without problems • Yellow - Calculations completed with warnings • Red - Calculations failed. The size of the log panels can be set by moving the cursor to the top boundary of the panels or the boundary between the panels. At the point where the cursor changes to a pair of resizing arrows, the left mouse button may be clicked and dragged to resize the panel. Both panels provide a popup menu with local options that can be opened by clicking the right mouse button. The popup menu provides the following options: Clear - clears all messages from the log. Save Messages - displays a standard file dialog to allow the current message list to be saved to an external log file.
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File Dialogs
3.6 File Dialogs Flaresim uses standard Windows file dialogs to save and retrieve files.
3.6.1 File Save Dialog The File Save Dialog appears when you select the File - Save As menu item or the File - Save menu item or Save tool bar icon for an unnamed case. The dialog also appears when you click the Export button or Save button on other Flaresim views e.g. to export results data from Receptor Grid views. Figure 3-4, File Save Dialog
The main elements on this Dialog are: Filename Combo box Allows you to enter the name of the file to save the Flaresim model to. As you type the name, the drop down list element of the combo
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box allows you to select an existing file that matches the name to overwrite if you wish. The file name entered will be given the extension type specified in the Save As Type field unless you enter a different file extension. Save As Type Drop down List of allowed file types Allows you to select the required file type. File Description Model Files
Allowed Types Flaresim for Windows files .FSW XML data files .XML
Table Export
Comma separated value files .CSV Excel files .XLS
Graphics Export
JPEG files .JPG Portable network graphic files .PNG Windows bitmap files .BMP Windows meta files .WMF Enhance windows meta files .EMF
Save In Drop down List of available storage locations Allows you to select from the list of available storage locations configured for your computer system. File List List Box Shows the files and folders in the current folder. The list may be used to navigate the folder tree or to select files. Folders can be opened and made the new current folder by double clicking on them. You can move up the folder tree by clicking the Previous Folder icon. New folders can be created by clicking the New Folder icon and entering the new folder name in the File List.
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File Dialogs
Files can be selected for overwriting by clicking on them. Save Button Saves the file once you have entered the name or selected a file to overwrite. If the file selected already exists you will be asked to confirm that it should be overwritten. Cancel Button Cancels the file save. New Folder Text Link Creates a new sub-folder in the current folder. The folder will be created with the default name “New Folder” and you will then be able to rename as required.
3.6.2 File Open Dialog The File Open Dialog appears when you select the File - Open menu item or click the Open icon on the tool bar.
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Figure 3-5, File Open Dialog
The elements of this dialog are essentially the same as the File Save Dialog with the exception that the Save button is replaced by an Open button.
3.6.3 Recent Files Menu The File Menu displays a list of recently used files which can be used to re-open one of these files directly by selecting it from the menu.
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File Dialogs
Figure 3-6, Recent Files Menu
3.6.4 Update Messages During File Open When opening a file from earlier versions of Flaresim it is possible that the program will detect parameters that have changed in the current version or detect results that will be changed as a result of changes in the program. When this happens a dialog will be displayed and the user will be asked to acknowledge the information or possibly make a decision between a number of choices. Further information on these dialogs can usually be found in the help system by pressing F1.
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3.7 About View The About View is opened using the Help - About menu option. Figure 3-7, About View
The purpose of this view is to provide information on the version of the program that may be required when seeking Technical support. Ok Button Closes the About view.
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Radiation Limits View
3.8 Radiation Limits View The Radiation Limits view is displayed using the Help - Radiation Limits menu option. Its purpose is to provide a quick guide to the most commonly considered radiation limits in flare design. Figure 3-8, Radiation Limits View
Close Button Closes the Radiation Limits view.
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3.9 Flaresim Update View The Flaresim Update view indicates whether an update to your working version of Flaresim is available. It is opened using the Help - Check For Update menu option. Figure 3-9, Flaresim Update View
If your Flaresim version is up to date you will see the view shown above. Otherwise if an update is available you will see release information and links to allow you to download the latest version. Ok Button Closes the Flaresim Update view.
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Flaresim Update View
General Setup
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4 General Setup Page 4.1
Case Navigator View . . . . . . . . . . . . . . . . . . 3
4.1.1 4.1.2 4.1.3
4.2
Case Summary View . . . . . . . . . . . . . . . . . . 8
4.2.1 4.2.2
4.3
Setup Wizard - Common Items . . . . . . . . . Setup Wizard - Opening View . . . . . . . . . . Setup Wizard - Fluid Page . . . . . . . . . . . . . Setup Wizard - Tip Page . . . . . . . . . . . . . . Setup Wizard - Environment Page . . . . . . Setup Wizard - Stack Page . . . . . . . . . . . . Setup Wizard - Receptors Page . . . . . . . . Setup Wizard - Calculations Page . . . . . .
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Preferences. . . . . . . . . . . . . . . . . . . . . . . . . 28
4.4.1 4.4.2 4.4.3 4.4.4
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Case Description Tab. . . . . . . . . . . . . . . . . . 8 Active Case Study Tab. . . . . . . . . . . . . . . . 10
Setup Wizard . . . . . . . . . . . . . . . . . . . . . . . 12
4.3.1 4.3.2 4.3.3 4.3.4 4.3.5 4.3.6 4.3.7 4.3.8
4.4
Command Buttons . . . . . . . . . . . . . . . . . . . . 4 Tool Bar Buttons . . . . . . . . . . . . . . . . . . . . . 5 Tree Icons . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Units Tab . . . . . . . . . . . . . . . . . . . . . . . . . . . Files & Options Tab . . . . . . . . . . . . . . . . . . Plots Tab . . . . . . . . . . . . . . . . . . . . . . . . . . . Sterile Area Tab . . . . . . . . . . . . . . . . . . . . .
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Component Management View . . . . . . . . . 45 4-1
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Case Navigator View
4.1 Case Navigator View The Case Navigator view, shown in Figure 4-1, provides a summary view of the Flaresim model, showing the objects that have been added to the model and their status. It also provides quick access to any of the object views and enables objects to be added to and deleted from the model. Figure 4-1, Case Navigator View
The Case Navigator view shows the Flaresim model as a tree with the branches showing the different types of object that make up the model. The Case Navigator is used by clicking a branch of the tree to select it and then clicking one of the command buttons to perform that action on the selected object. For example to open the Pipe Tip in 4-4
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navigator view displayed above, click Pipe Tip then click the View button. A branch can also be double-clicked which will act the same way as the View action. If a branch with sub branches is double-clicked or Viewed it will open a summary view for that object type if it is available. Summary views are available for Environments, Stacks, Tips and Receptor Points.
4.1.1 Command Buttons The Case Navigator command buttons have the following functions:Calculate This button at the top of the Case Navigator view may be labelled “Click to Calculate”, “Rating Complete” or “Sizing Complete” depending on the current state of the case. It may be clicked at any time to start calculations. While the case is calculating the surface of the button changes to show a progress bar indicating progress of the calculations. Messages will also be output to the Error/Warnings Log as calculations proceed. View Opens the view for the selected object to allow its data to be viewed or updated. Add Creates a new object of the selected type and opens its view ready for data input. If an existing object is selected in the tree rather than the parent branch, a new object of the same type is created. Activate Clears the ignored status for the selected object which restores it to the calculations. Not all objects can be ignored and restored and this button will be greyed out if the action cannot be applied to the selected object.
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Ignore Sets the ignored status for the selected object which means that it will not be included in the calculations. Not all objects can be ignored and restored and this button will be greyed out if the action cannot be applied to the selected object. Copy A new object of the same type as the selected object will be created and its contents set to the same values as the selected object. Not all objects can be copied and this button will be greyed out if the action cannot be applied to the selected object. Delete Deletes the selected object. No confirmation is required. Not all objects can be deleted and this button will be greyed out if the selected object is a permanent part of the case e.g. the Case Description.
4.1.2 Tool Bar Buttons The following buttons appear on the Case Navigator tool bar. This icon opens a drop down menu offering a list of objects that can be added to the case. It is equivalent to selecting the object type branch in the Navigator tree view and clicking the Add button. This icon saves the case. If the case has an name and has already been saved it will be overwritten. If it is a new case a File - Save As dialog will open. A message indicating success or failure will be written to the File Management Log. This icon saves the case with a new name. A File - Save As dialog will open to allow the file name to be specified. A message indicating success or failure will be written to the File Management Log.
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This icon opens the Report View to allow selection of the print options for the case and to allow printing of the case. This icon opens the Print Graphic Report View to allows selection, saving or printing of the graphic reports for the case. This icon collapses the Case Navigator into a summary view that consists of a vertical tool bar. Vertical tool bar buttons in the Case Navigator summary are the same as in the standard Case Navigator with the following additions. This icon expands the Case Navigator to its normal size. This icon starts the calculations for the case. The colour of the tool bar background is This icon displays a pop up menu of the objects in the current case. Selecting an object will display its view.
4.1.3 Tree Icons The icons displayed against each branch and object in the Case Navigator view have the following meanings. This icon identifies a branch of the model tree that contains a single object that is a permanent part of the model and cannot be added or deleted. Examples of this type of object are the Case Description and Calculation Options object. When a branch of this type is selected the Add, Delete, Copy Activate and Ignore buttons are greyed out since they are not applicable. This icon identifies branches of the model that contain objects that are not essential to the running of the model. Examples of this type of object are the Receptor Point and Assist Fluid objects.
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Case Navigator View
This icon indicates a branch of the model that contains objects that are essential to the calculation of the model where the required objects are either missing or have incomplete data. Examples of this type of object are the Tip and Stack objects. This icon indicates a branch of the model that contains objects that are essential to the calculation of the model where the required objects are complete and ready for calculation. Examples of this type of object are the Tip and Stack objects. This icon indicates an object that has been set to an ignored status. Ignored objects are not included in the calculations. Normally where multiple objects may be defined e.g. Tips and Stacks, multiple objects may be ignored as long as there is at least one left active for calculations. The exception is the Environment object where only one can be active; all the others being set to ignored. This icon indicates an object whose data is incomplete or in error in some way. This icon indicates an object whose data is complete and ready to calculate. This icon indicates a branch that has sub-branch objects defined that are not currently displayed. Clicking this icon will expand the tree to show the sub-branch objects. This icon appears against a branch with displayed subbranch objects. Clicking it will collapse the branch and hide the sub-branch objects.
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4.2 Case Summary View The Case Summary view (see Figure 4-2) allows the user to enter information to describe the Flaresim model. It also displays information about any Case Study used to update the main model. The Case Summary view is opened by selecting it in the Case Navigator view and clicking the View button or by double clicking on it in the Case Navigator.
4.2.1 Case Description Tab Figure 4-2, Case Summary View, Case Description Tab
Case Data - Title Text Text entered in this field will be printed as the model title on reports.
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Case Data - Author Text Identifies the author of this Flaresim file. Case Data - Revision Text Identifies the revision of the Flaresim file. Case Data - Checked By Text Identifies the person responsible for checking the model. Description Text Descriptive information relevant to the model. For example it is good practice to note sources of environmental data and the contingencies represented by the fluid data. File Details - Last Calculated Calculated Value Tracks the date and time that the model was last calculated. It is automatically updated each time the model is calculated and cannot be manually updated. File Details - Last Saved Calculated Value Tracks the date that the model was last saved. It is automatically updated each time the model is saved and cannot be manually updated. File Details - File Version Calculated Value Tracks version of Flaresim that was used when the file was last saved. File Details - Last Saved As Calculated Value Tracks the name that was used when the file was last saved.
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4.2.2 Active Case Study Tab The Active Case Study tab records the update of the base model when a set of input data is “double-clicked” in a Case Study. Figure 4-3, Case Summary, Active Case Study Tab
Case Study Name Calculated Value This is the name of the Case Study used to update the base case. Case Tag Calculated Value This is the short tag name of the individual case within the Case Study that was used to update the base case. Last Copied Calculated Value This is the date and time at which the base case was updated from the Case Study. 4-11
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Description Calculated Value This is the descriptive information defined in the Case Study for the case that was used to update the base case. Clear Active Case Study Information Button Clicking this removes all the Case Study information from the Active Case tab.
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4.3 Setup Wizard The Setup Wizard view provides a step by step guide to setting up a basic Flaresim model. It is intended for use by new users to provide the simplest possible interface for defining a new model. The Setup Wizard provides pages or tabs that allow the user to define in turn the fluid to be flared, details of the flare tip, environment details, details of the flare stack, location of critical receptor points and the calculation options to be used. Each page must be completed before the user can move to the next page. Where possible default data values and options are provided to allow the setup of a new case to be made as simple as possible. When the final page is completed and the Finish button is selected the wizard will automatically create the Flaresim objects required to define the case. By default, the Setup Wizard will be automatically displayed when starting Flaresim or when creating a new case. If the user does not want to use the Setup Wizard then its view can be simply closed. Experienced users who do not wish to use the Setup Wizard at all can select this option on the Files&Options tab of the Preferences view, see section 4.4.2
4.3.1 Setup Wizard - Common Items Figure 4-4 below shows the Fluid page of the Setup Wizard and indicates the main areas of the view as follows. Summary Panel This provides a summary of the data input provided so far. Data Entry Panel This region will change to provide the data entry fields required for the current item. Help Panel This region provides additional information about the selected data entry field and will change as different fields are selected. The
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information provided may explain why the data item is required and indicate the range of values allowed as well as typical values. Command buttons These allow the user to move from page to page of the Setup Wizard. The Finish button is only available when all of the required information has been entered Figure 4-4, Setup Wizard View
Page Tabs These display the status of each section of the Setup Wizard. The icons used, and have the same meanings as in the Case Navigator view, section 4.1. The Page Tabs also allow the user to move between completed pages of the Setup Wizard.
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4.3.2 Setup Wizard - Opening View The opening view of the Setup Wizard is shown below. Figure 4-5, Setup Wizard - Opening View
Unit set to use Drop down list: Available Unit Sets This field selects the units that will be used by Flaresim. The drop down list only allows selection from existing unit sets. To create and customise the contents of units sets the File - Preferences menu option can be used, see section 4.4
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4.3.3 Setup Wizard - Fluid Page The second page of the Setup Wizard is the Fluid page shown below. Figure 4-6, Setup Wizard - Fluid Page
Fluid Conditions - Temperature Range: 0 to 1000 K This field defines the temperature of the fluid going to the flare. Fluid Conditions - Ref. Pressure Range: 0.001 to 100 bar a This field defines the reference pressure at which the temperature of the fluid is specified. Where the operating pressure of the flare differs from the reference pressure, the fluid temperature may be corrected for the pressure change. By default this correction is disabled in Flaresim 4.0. The user can choose to apply this correction through the Options tab of the Fluid view, see chapter 6.
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Property Calculation Radio buttons: Specified Properties/From Composition These buttons control how the fluid properties are to be obtained. If the Specified Properties option is selected then the bulk properties of the fluid must be input using the Fluid Properties table as shown in Figure 4-6. Otherwise if the From Composition option is selected the view will change to allow the fluid composition to be specified from which the fluid properties will be calculated. Fluid Properties - Molecular Weight Range: 2 to 1000 The molecular weight of the fluid. It is a required entry. Fluid Properties - LHV Range: 0 to 100 MJ/kg This defines the Lower Heating Value of the fluid, also known as the net heating value. It is a required entry. Fluid Properties - Cp/Cv Range: 1 to 5 This defines the ratio of the specific heat capacities of the fluid. A default value of 1.2 is provided which may be used where this value is unknown. Fluid Properties - LEL Range: 0 to 100% This defines the Lower Explosive Limit of the fluid. A default value of 2% is provided which may be used where this value is unknown. The LEL is only used by the Brzustowski radiation method so the value can safely be left at the default value when other calculation methods are used. Fluid Properties - Saturation Range: 0 to 100% This defines the degree of saturation of the hydrocarbons in the fluid. The default value of 100% assumes that all the fluid is paraffinic hydrocarbon. The saturation is only used by the High Efficiency F Factor method and may safely be left at the default value when other F Factor methods are used.
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Fluid Properties - Pc Range: 0.001 to 1000 bar a This defines the critical pressure of the fluid. It is used in the calculation of fluid temperatures and densities. Entry of this value is optional as an internal correlation will be used to estimate the fluids Pc if this value is not provided. Fluid Properties - Tc Range: 2 to 1000 K This defines the critical temperature of the fluid. It is used in the calculation of fluid temperatures and densities. Entry of this value is optional as an internal correlation will be used to estimate the fluids Tc if this value is not provided. When the Compositional radio button is selected the fluid page is updated to so the Fluid composition table as shown below. Figure 4-7, Setup Wizard - Fluid Page Compositions
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Composition Basis Radio buttons: Mole/Mass These buttons select the composition input basis either Mole fraction or Mass fraction Normalise Composition Button Clicking this button will normalise the current composition. Unspecified component fractions will be set to 0.0 and the remainder normalised so to give a total fraction of 1.0. Fluid Composition - Fraction Range: 0 to 1.0 The component composition.
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4.3.4 Setup Wizard - Tip Page The Tip page of the Setup Wizard is shown below. Figure 4-8, Setup Wizard - Tip Page
Tip Type Radio buttons: Pipe Tip / Sonic Tip This allows selection of the tip type to be used either a Pipe Tip or Sonic Tip. If unknown the default Pipe Tip will provide the most conservative option. Tip Sizing - Fluid Mass Flow Rate Range: 0 to 10000 kg/s Defines the mass flow rate of the fluid to be flared.
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Tip Sizing - Tip Diameter Range: 0.0 to 10 m Defines the diameter of the tip. When the mass flow rate is defined the tip diameter will be automatically updated to show the tip diameter required for the current Mach number. Updating the tip diameter with a specified value will automatically update the Mach number value. Tip Sizing - Mach Number Range: 0 to 1 Defines the tip exit Mach number i.e. the tip exit velocity as a fraction of the sonic velocity. This is defaulted to 0.45 Mach which is a reasonable default for an efficient pipe flare. Updating the Mach number will recalculate the required tip diameter as long as the fluid mass flow rate is known. Alternatively, updating the tip diameter with a specified value will automatically update the Mach number value. F Factor Method Check box Selects the method that will be used to calculate the fraction of combustion heat that will be radiated from the flame. The F Factor is sometimes known as the emissivity of the flame. The default Generic Pipe method is a conservative general purpose method. The High Efficiency method should only be used for high efficiency tips in good condition burning low molecular weight fluids.
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4.3.5 Setup Wizard - Environment Page The Environment page which is the fourth page of the Setup Wizard is shown below. Figure 4-9, Setup Wizard - Environment Page
Environment - Wind Speed Range: 0 to 100 m/s The wind speed to be used for the calculations. A default wind speed of 20 m/s is defined. Environment - Wind Direction Range: 0 to 360 The angle from which the wind is blowing. 0 degrees is North, 90 East, 180 South and 270 West. It is common to do calculations relative to a wind from the North so 0 degrees is the default.
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Environment - Temperature Range: 10 to 500 K The environmental temperature. The value is used in surface temperature calculations and gas dispersion calculations. Environment - Humidity Range: 4 to 100% The environmental humidity. The humidity value is used in calculations of the attenuation in radiation due to the atmosphere i.e. the transmissivity calculation. It is used when the Transmissivity is to be calculated i.e. when the Transmissivity is not set to User Specified. The default value of 10% is reasonably conservative. Environment - Transmissivity Spec Range: 0 to 1 The value for atmospheric transmissivity to be used if the Transmissivity method is set to User Defined. The default value of 1.0 is conservative and does not allow for any attenuation of radiation when passing through the atmosphere. Environment - Transmissivity Method Drop down: UserSpecified / Calculated / CalcNoLimits / Wayne The method to be used for the calculation of the factor for correcting the transmissivity of radiation through the atmosphere. The Default is UserSpecified method which with a specified transmissivity value of 1 is the most conservative. The Calculated and CalcNoLimits methods calculate the transmissivity as a function of the distance travelled by the radiation through the atmosphere and the atmospheric humidity, the difference between them being whether the distance limits applicable to the Hottel derived equation are used (see Methods chapter). The Wayne method calculates transmissivity as a function of both atmospheric temperature and humidity.
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4.3.6 Setup Wizard - Stack Page The Stack page of the Setup Wizard is shown below Figure 4-10, Setup Wizard - Environment Page
Stack Angle To Vertical Check box This set of check boxes allows rapid selection of some standard angles for the stack which will be updated in the Vertical Angle entry. In general onshore flare stacks are vertical while flare stacks on offshore platforms are often angled at 45 or 60 degrees to Horizontal. If your stack is not a standard angle then select the User check box to input the angle in the table below. Angle To Vertical Range: 0 to 90 degrees The angle of the stack to the horizontal. Use this field if your stack is not at one of the standard angles. 4-24
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Angle from North Range: 0 to 360 degrees The direction in which the stack points. This field is important for non-vertical stacks and should be set with regard to the specified wind direction. It is normal for stacks to be oriented to point into the prevailing wind so if the wind is from the East (90degrees) then it would be normal to set the stack horizontal orientation to 90 degrees as well. Stack Length Range: 0 to 1000m The length of the stack. Leaving the value empty will cause the Setup Wizard to create a Sizing case where the stack length will be calculated to meet a defined limiting value for the radiation.
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4.3.7 Setup Wizard - Receptors Page The Receptors page of the Setup Wizard is shown below Figure 4-11, Setup Wizard - Receptors Page
Receptor ID Text The default name provided e.g. RP_1 can be updated with a more descriptive name e.g. Stack Base. Northing Range: -1000 to 1000m The location of the receptor point in the Northing direction. In general the points of maximum radiation are found directly downwind of the stack. So if the wind is from the North you will generally be entering Northing locations with a negative value. For example a Northing value of -10m will be a point 10m down wind. 4-26
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Easting Range: -1000 to 1000m The location of the receptor point Easting direction. Elevation Range: -500 to 500m The height of the receptor point. Cases defined through the Setup Wizard define the 0 elevation point as the base of the stack so this is the height of the receptor point above or below the stack base. Allowable Radiation Range: 0 to 31560 W/m2 The radiation that is allowed at the receptor point. The table of typical design values shown on this page provides a general guide to the selection of appropriate values. Add Button Button Clicking this button adds a new receptor point to the model. Delete Button Button Clicking this button deletes the current selected receptor point.
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4.3.8 Setup Wizard - Calculations Page The Calculations page of the Setup Wizard is shown below. Figure 4-12, Setup Wizard - Calculations Page
Calculation Method Check box This allows selection of the calculation method to be used. The default Flaresim API method should generally give a conservative result using industry standard methods. The Mixed method with 25 Flame elements is recommended as a good general alternative.
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4.4 Preferences The File - Preferences menu item provides access to the Preferences View to allow setup of the preferred units, file locations and graphical plot elements. Figure 4-13, Units Tab
Read Preference File Button Reads a preference file. A File Open dialog will be opened to allow the location of the preference file to be specified. Save Preference File Button Saves the current preferences. A File Save dialog will be opened to allow the location of the preferences file to be specified. Preference files are saved as files of type XML.
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Preferences
On startup, Flaresim first searches for a file called Preferences.xml in the folder User Documents\Softbits\Flaresim 4.0 . If not found the default Preferences.xml file is read from the SharedProgramData folder. The SharedProgramData folder referred to above is typically the folder C:\Documents and Settings\All User\Application Data\ Softbits\Flaresim 4.0 on a Windows XP system or the folder C:\ProgramData\Softbits\Flaresim 4.0 on a Vista, Windows 7 or Windows 8 system.
4.4.1 Units Tab The Units tab of the Preferences view (see Figure 4-13) is used to define the units of measure used to display and interpret values on the data entry views. Flaresim uses the concept of a Unit Set which defines all of the units to be used for a single case. Two Unit Sets, the Default SI and Default Field sets are provided as basic sets that cannot be changed. A third European unit set is provided which can be modified. New Unit Sets can be created by copying an existing Unit Set and then customising it. A default range of units is provided for each type of unit used by Flaresim. The Units tab also allows new units to be defined by defining their name and conversion to the internal unit used by Flaresim. Unit Sets - List List box Shows the Unit Sets that have already been defined in the Preferences file. A Unit Set may be activated by selecting it in this list. On activation all open data views are immediately updated to display values in the new units.
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Unit Sets - Rename Unit Set Text Allows the name of a user defined Unit Set to be updated. The names of the default Unit Sets cannot be changed. Unit Sets - Copy Unit Set Button Copies the selected Unit Set to create a new one. The new Unit set will be given a default name that can then be updated to describe it. Unit Sets - Delete Unit Set Button Deletes the selected Unit Set. The default internal Unit Sets cannot be deleted and this button will be inactive when these are selected. Unit Select - Table Table Shows a list of the unit types used in Flaresim with the current unit defined for the selected Unit Set and the current format specifier. To update the unit or format used for a particular unit type e.g. Temperature, move to the appropriate row and then select the required unit in the Selected Unit column and update the format specifier in the Format column. Unit Select Table - Selected Unit Column Drop down list: Available Units Allows selection of the unit to be used for the currently selected unit type. As the selection is changed the conversion factors for the unit are displayed in the Unit Definition fields at the bottom of the view. Unit Select Table - Format Text Allows the output format of the selected unit type to be specified. Format specifiers should be of the form:###0.000 where the # symbol denotes the space allowed for leading digits and the 0.000 section denotes the number of decimal places that will be used for output.
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Preferences
Unit Select - Add Button Allows new units to be defined for a particular unit type. Clicking the button displays a pop up window to allow the new unit name to be defined as shown below. Figure 4-14, New Unit Name Window
Clicking the OK button on this window activates the Unit Definition fields and the Accept button. Unit Select - Delete Button Allows units to be deleted. Clicking the button will delete the currently selected unit. A confirmation dialog will be displayed to confirm the action. Only user added units can be deleted and the button will be greyed out if the selected unit is not a user added unit. Unit Select - Accept Button Accepts the updated unit information. Unit Definition - Multiplier Number Defines the multiplication constant required to convert the new unit to the internal default unit which is displayed. Unit Definition - Offset Number Defines the offset to be added to convert the new unit to the internal default unit which is displayed. Note the offset is added after multiplication.
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4.4.2 Files & Options Tab The Files&Options tab of the Preferences view allows the location of the units and components files to be specified along with other options. Figure 4-15, Files Tab
Default Files - Units File name Defines the name of the unit conversion factors file, normally Units.xml. If no folder path is specified Flaresim will expect to find this in the SharedProgramData folder. The Browse button allows the file to be located using a standard File Dialog. Default Files - Component Library File name Defines the name of the component library file, normally Librarycomponents.xml. If no folder path is specified Flaresim will
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expect to find this in the SharedProgramData folder. The Browse button allows the file to be located using a standard File Dialog. This allows the user to create dedicated component files to be created and used for specialised applications. Default Files - Report Layout File File name Defines the name of the style sheet file (XSL file) that will be used to layout printed reports. By default this will be Flaresim.xsl. If no folder path is specified Flaresim will expect to find this in the SharedProgramData folder. Clients are able to create customised report style sheets using standard XSL language to change the layout of Flaresim reports. Default Files - Graphic Report Layout File name Defines the name of the graphic report layout file to be used by default. Standard graphic report layout files have a .lay extension and are defined for A4 and US Letter paper sizes and for systems with one or more stacks and one or more tips. If no folder path is specified Flaresim will expect to find the file in the SharedProgramData folder. The default layout file selected here can be reset for individual receptor grids or dispersion objects on the Graphic Report tab of the relevant view. The contents of the.lay files describe the location and formatting of isopleth charts and accompanying data items and descriptive text using XML syntax. The XML elements recognised in these files are described in Appendix A of this manual. Default Files - Wizard Help File File name Defines the name of the file containing the help information displayed on the Setup Wizard. By default this file is called WizardHelp.xml. Flaresim will expect to find this file in the SharedProgramData folder.
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Default Files - Error Log File File name Defines the name of the file which will be used to record any errors generated as you run Flaresim. By default the file will be saved in the SharedProgramData folder. Error messages will only be recorded if the Use Error Log option is selected. Default Files - Pipe Schedules File name Defines the name of the file containing Pipe Schedule data, normally PipeSizes.xml. If no folder path is specified Flaresim will expect to find this in the SharedProgramData folder. The Browse button allows the file to be located using a standard File Dialog. Option Settings - Use Setup Wizard Check box When selected, Flaresim will display the Setup Wizard whenever Flaresim is opened without specifying a file to load or when a new Flaresim case is created. The Setup Wizard provides a step by step guide to creating a basic Flaresim model. Use of the Setup Wizard is described in section 4.3. Option Settings - Use Specified Formats Check box When selected, Flaresim will use the defined Format values for each unit when displaying values in the Input Tables on the various views. Otherwise values will be displayed to 3 significant figures. Option Settings - Use US Number Formats Check box When selected, Flaresim will display and accept values using US number formats i.e. 123.1234. When cleared, numbers will be displayed and accepted using the number format defined by the current Windows language settings. Option Settings - Log Errors to File Check box When selected, Flaresim will record all the exception errors displayed to the log file defined in the Files section.
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Option Settings - Maximise View Check box When selected, Flaresim will display all newly opened or created cases in a maximise Case View, overlaying the previously visible view. Option Settings - Remember Graphic Printer Selection Check box When selected, Flaresim will store the name of the printer selected for output of graphic reports and will automatically reselect it next time Flaresim is run. Page settings are always remembered. Option Settings - Save Isopleth Points Check box When selected, Flaresim will store the coordinates for the isopleth results within the .fsw file when the case is saved. Selecting this option may increase the size of the .fsw significantly. Option Settings - Check For Updates Check box When selected Flaresim will automatically check for program updates every 7 days as it starts up. A manual check for updates using the Help - Check For Updates menu option can be done at any time and is not affected by this setting.
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4.4.3 Plots Tab The Plots tab of the Preferences view is used to customise the appearance of the isopleth plots in the Receptor Grid view and the plots in the Graphical Reports. Figure 4-16, Plots Tab
Plot Type Drop down list: Radiation Isopleth / Noise Isopleth / Temperature Isopleth / Concentration Isopleth / Dispersion Plot / Wind Rose Plot This drop down list selects the type of plot that the customisation options displayed will be applied to. Update Existing Grids, Points and Dispersion Objects Button Clicking this button applies the current plot preference settings to all existing receptor grid isopleth plots, Gaussian dispersion isopleth plots and receptor point windrose plots. The update applies in all open cases.
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A typical use for this button would be to apply settings from a preference file to an open case i.e. read the preference file and then click this button. The customisation options are viewed and updated through three sub tabs, for Plot Details, Contour Details and Text Details. On the Plot Details tab, see Figure 4-16, it is possible to set the following options. Plot Options - Display Grid Check box When selected plots will show a background grid. Plot Options - Display Flame Check box When selected isopleth plots will show a line representing the shape of the flames from any active flare tips. Plot Options - Display Stack Check box When selected isopleth plots will show lines representing the size and orientation of active flare stacks. Plot Options - Display Tip Check box When selected isopleth plots will show lines representing the size and orientation of active flare tips. Plot Options - Display Shield Check box When selected isopleth plots will show lines representing the intersection of active shield sections with the plane of the isopleth. Note that it is the intersection that is displayed not the projection of the shield on the isopleth. If plan view isopleth is at ground level i.e. 0m then the shields will require at least one point with an elevation dimension < 0m in order to intersect with the isopleth plane.
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Plot Parameter - Number of lines Integer range: 1 to 9 This value determines the number of grid lines that will be displayed for each axis of the isopleth plots. Plot Parameter - Flame Thickness Integer range: 1 to 50 This values defines the width in pixels of the line that will be drawn to represent the flame shape. Plot Parameter - Stack Thickness Integer range: 1 to 50 This values defines the width in pixels of the line that will be drawn to represent each active stack on the isopleth plots. Plot Parameter - Tip Thickness Integer range: 1 to 50 This values defines the width in pixels of the line that will be drawn to represent the each active tip on the isopleth plots. Plot Parameter - Shield Thickness Integer range: 1 to 50 This values defines the width in pixels of the line that will be drawn to represent the shield sections on the isopleth plots. Plot Colour - Grid Colour Colour dialog This shows the colour that will be used for the background of the isopleth plots. The colour may be selected by double-clicking the sample panel to display the Flaresim colour dialog.
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Preferences
Figure 4-17, Colour Dialog
Colours are selected in the dialog by clicking on the colour required and then clicking the Ok button. To close the dialog without changing the colour click the Cancel button. Plot Options - Flame Colour Colour dialog This shows the colour that will be used to draw the line representing the flame shape on the isopleth plots. The colour may be selected by double-clicking the sample panel to display the Flaresim colour dialog. Plot Options - Stack Colour Colour dialog This shows the colour that will be used to draw the line representing the flare stacks on the isopleth plots. The colour may be selected by double-clicking the sample panel to display the Flaresim colour dialog. Plot Options - Tip Colour Colour dialog This shows the colour that will be used to draw the line representing the flame shape on the isopleth plots. The colour may be selected by double-clicking the sample panel to display the Flaresim colour dialog.
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General Setup
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Plot Options - Colour Colour dialog This shows the colour that will be used to draw the line representing the shield sections on the isopleth plots. The colour may be selected by double-clicking the sample panel to display the Flaresim colour dialog. On the Contour Details tab, see Figure 4-18, it is possible to select the following options for the 10 contour lines that are available for each type of plot. Figure 4-18, Contour Details
Contour Details - Value Number This column defines the value for the selected isopleth contour in the units defined at the head of the column.
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Preferences
Contour Details - Display Check box This column specifies whether the selected isopleth contour will be displayed. Set the check box to display the contour, clear it to hide the contour. Contours Contour Details - Colour Colour dialog This column defines the colour to be used for the selected isopleth contour. Double click the sample panel to open the Flaresim colour dialog to change the colour. Contour Details - Width Number This column defines the line width used to draw the selected isopleth contour. Contour Details - Value Drop down list: Solid / Dash / Dot / DashDot / DashDotDot This column selects the line style used to draw the selected isopleth contour. The Text Details tab, see Figure 4-19, allows the following settings to be defined. Figure 4-19, Isopleth Text Details
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General Setup
4-43
Text Options - Select Text Item Select Row The rows of this table describe the different text elements that can appear on an isopleth plot. The display properties of each different text element can be set by selecting the row and then using the fields below to modify the properties. Not all of the defined properties may be supported for all of the text elements. Where a property cannot be set it will be greyed out while that text element is selected. Text Options - Display Item Check box This controls whether the selected text element will be displayed. Set the check box to display the item, clear it to hide it. Text Options - Sample Font dialog The Sample column displays a sample of the font style that is currently defined for the selected text item. Double clicking the sample text opens a standard windows font dialog to allow the family, size and style of the font to be set for the selected text item. Figure 4-20, Font Dialog
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Preferences
Text Options - Spacing Integer Range: 1 to 20 This determines the spacing between the selected text element and the item it describes e.g the spacing between the X-Axis of the isopleth plot and the X-Axis of the graph. The value is expressed as a percentage of the dimensions of the isopleth plot.
4.4.4 Sterile Area Tab The Sterile Area tab of the Preferences view, see below, is used to define the default radiation and noise limits to be specified for the sterile area calculation as a new Stack object is created. Figure 4-21, Preferences View - Sterile Area Tab
The view provides the following options.
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General Setup
4-45
Sterile Area Limits - Radiation Limits Range: 0 to 1.0e9 W/m2 Up to 10 radiation values can be defined. The sterile area calculation for each stack will calculate the distance downwind of the stack required for the radiation to drop below each defined limit. Noise Limits Range: 0 to 150 Db Up to 10 noise values can be defined. The sterile area calculation for each stack will calculate the distance downwind of the stack required for the noise to drop below each defined limit. Update Existing Stack Objects Button Clicking this button copies the current preference settings for the sterile area radiation limits and noise limits to existing stack objects.
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Component Management View
4.5 Component Management View The Component Management view (see Figure 4-22) is used to maintain and update the library of component data that may be used to allow fluid properties to be calculated from their component composition. The Component Management view is opened by selecting it in the Case Navigator view and clicking the View button. Figure 4-22, Component Management View
The list of components defined for the model is shown in the Available Components list. Selecting a component in this list will display its properties in the three tabbed pages at the bottom of the view. If the component selected is a user added component the Remove Selected Component and Edit Selected component command buttons will be activated. New components can be added to the component library by clicking the Add New Component button. This displays a pop-up window 4-46
General Setup
4-47
(see Figure 4-23) to allow the entry of the new component’s name. When this has been entered click the OK button and the component will be added to the list in the Component Manager view. and its properties will be displayed ready for entry. Figure 4-23, Component Name Popup
Data for a new component or existing data for a user added component is updated through the three tabbed views, Properties, Structure and Enthalpy coefficients as described below. While data is being updated an “Edit Component” information panel will be displayed below the command buttons. The options on the Properties tab are shown in Figure 4-22 above. Mole Weight Range: 2 to 1000 The molecular weight of the component. LHV Range: 0 to 200MJ/kg The net, or lower heating value of the component. It is a common error in the design of flare systems to use the gross heating value. For most hydrocarbon components this value will be of the order of 46 MJ/kg Cp / Cv Range: 1.01 to 5.0 The ratio of the specific heat capacities of the component. If the value is unknown we would recommend using a value of 1.2.
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Component Management View
Saturation Range: 0 to 100% The percentage saturation of the component. LEL Range: 0.0 to 100.0% The lower flammability limit of the component as a volume percentage. Critical Temperature Range: 10 to 10,000 K The critical temperature of the component. Critical Pressure Range: 0.01 to 1,000 bar a The critical pressure of the component. Data File Text: File Name The name of the REFPROP data file containing data for this component. On the Structure tab of the component data entry view the number of atoms of each listed atom in the component should be entered, an example for Methane is shown below. Figure 4-24, Component Structure Input
This number is used in the calculation of combustion products. The list of atoms cannot be updated. If other atoms are needed they must
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General Setup
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be defined in the LibraryComponents.xml file along with details of their combustion products. The final tab of the Component data entry is the enthalpy coefficients tab as shown below. Figure 4-25, Enthalpy Coefficients Data Entry
Flaresim calculates the enthalpy of fluids and combustion gases by summing the contributions made by each component. The individual component enthalpy contributions are calculated using the following polynomial equation. 2 3 4 5
E = A+B⋅T+C⋅T +D⋅T +E⋅T +F⋅T
where E is the enthalpy in J/kg T is the temperature in K A, B, C, D, E, F are constants The data entry table for the enthalpy coefficients allows the enthalpy unit for each constant to be selected but the values entered will always be based on a temperature in K. Once the component property data has been defined click the Accept Edit button to complete definition of the new component. If for any reason you wish to abandon creation of a new component at the property data entry stage then click the Cancel Edit button.
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Component Management View
Components that have been added by the user may be updated by selecting it in the list and clicking the Edit Component Data button. This option is not available for components from the Flaresim database. To remove a component from the library, select it in the list and click the Remove Selected Component button.
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Fluids
5-1
5 Fluids Page 5.1
Fluid View . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5.1.1 5.1.2 5.1.3 5.1.4 5.1.5
5.2
Common Fields . . . . . . . . . . . . . . . . . . . . . . 4 Properties Tab . . . . . . . . . . . . . . . . . . . . . . . 4 Options Tab . . . . . . . . . . . . . . . . . . . . . . . . . 7 Composition Tab . . . . . . . . . . . . . . . . . . . . .11 Combustion Results Tab . . . . . . . . . . . . . . 13
Assist Fluid View . . . . . . . . . . . . . . . . . . . . 15
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Fluids
5-3
The Fluid object defines the properties of the fluids to be flared through a flare tip. The fluid properties may either be entered directly or calculated from a defined composition. A single set of fluid properties can be assigned to one or more flare tips. Fluid objects may be created using the Fluid option from the Add drop down menu or by selecting the Fluid branch in the Case Navigator view and clicking the Add button. An existing Fluid object may be viewed by double clicking it in the Case Navigator view or by selecting it in the Case Navigator view and clicking the View button. Fluid objects will be included in the calculations when they are assigned to a flare tip through the Tip view. A Fluid may be assigned to more than one flare tip. Unassigned fluids take no part in the calculations. A Fluid object can be deleted either by clicking the Delete button on its view or by selecting it in the Case Navigator view and clicking the Delete button on this view. The Assist Fluid object both identifies the additional fluids that may be fed to a flare tip to improve combustion and also defines the information needed to calculate the flow of the assist fluid required. Like Fluid objects, Assist Fluids are included in the calculations only when assigned to a flare tip. Assist Fluid objects may be created using the Assist Fluid menu option from the Add drop down menu or by selecting the Assist Fluid branch in the Case Navigator view and clicking the Add button. An existing Assist Fluid object may be viewed by double clicking it in the Case Navigator view or by selecting it in the Case Navigator view and clicking the View button. Assist Fluid objects may be deleted either through the Case Navigator view or by using the Delete button on the Assist Fluid view.
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Fluid View
5.1 Fluid View The following figure shows the Fluid view for entering and updating fluid data. Figure 5-1, Fluid View
5.1.1 Common Fields Name Text Enter text to identify this Fluid object. Status Text Status message The message displayed in this field and its colour indicates whether the data for this fluid object is complete and ready for calculation.
5.1.2 Properties Tab The Properties tab of the Fluid view, see Figure 5-1, has the following data entry fields. Note that all of these fields except the 5-4
Fluids
5-5
temperature and reference pressure will be calculated from the fluid composition if this is entered. Method - Calculation Method Drop down list: Flaresim/REFPROP Selects the method that will be used to calculate the fluid properties used during the calculations. The Flaresim method selects the correlations used by Flaresim 3.0 and earlier. It does not require the composition of the fluid to be defined; the properties of the fluid can be defined directly. If a composition is supplied then the properties are calculated from the composition by summing the contributions of each component as appropriate. The REFPROP method is based on the REFPROP physical properties package from NIST. A fluid composition is required and will be used to calculate properties such as CpCv, Tc and Pc. Other properties such as MolWt, LHV, LEL and saturation will be calculated from the composition by summing the contributions of each component. Conditions - Temperature Range: 10 to 1000K The temperature of the fluid at the tip exit. Note that this is the temperature of the fluid at the defined reference pressure. If either a Steam or Air assisted flare tip is being used this temperature is the fluid temperature before mixing with the steam or air flow. Conditions - Ref. Pressure Range: 100 to 2000000 Pa The reference pressure at which the fluid temperature is defined. The fluid temperature can be corrected from this pressure to other pressures assuming adiabatic isentropic compression/expansion if the temperature correction calculation option is set.
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Fluid View
Properties - Mole Weight Range: 2 to 1000 The molecular weight of the fluid being flared. Properties - Lower Heating Value Range: 0 to 200MJ/kg The net or lower heating value of the fluid. It is a common error in the design of flare systems to use the gross heating value of the fluid. We are interested in the net heat released by the flame. For most hydrocarbon fluids without inerts this value will be of the order of 46 MJ/kg. Properties - Cp / Cv Range: 1.0 to 5.0 This field defines the ratio of the specific heat capacities of the fluid. It is only required and used when the fluid is a vapour. If the value is unknown we would recommend using a value of 1.2. Properties - LEL Range: 0.0 to 100.0% The lower flammability limit of the fluid as a volume percentage. This property is used by the Brzustowski method for calculation of flame shape. It is not used by any of the other methods, in which case any value may be entered. Properties - Saturation Range: 0 to 100% The percentage of saturated hydrocarbon molecules in the fluid on a mole basis. This is used by the Flaresim method for estimation of the fraction of heat radiated by a flame (emissivity). It is not used by any of the other methods in which case any value may be entered. For inert or non-hydrocarbon fluids and components assume 100% saturation since this leads to combustion with a flame of lower luminosity.
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Fluids
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Critical Properties - Critical Temperature Range: 10 to 1000K The critical temperature of the fluid. It is used in the calculation of the compressibility factor which in turn is used in the calculation of the fluid density. If a value is not supplied, the fluid’s critical temperature will be estimated using an internal correlation based on mole weight. Critical Properties - Critical Pressure Range: 0.01 to 1000 bar a The critical pressure of the fluid. It is used in the calculation of the compressibility factor which in turn is used in the calculation of the fluid density. If a value is not supplied, the fluid’s critical pressure will be estimated using an internal correlation based on mole weight.
5.1.3 Options Tab The Options tab is used to input data that is specific to each fluid property method. For the Flaresim method the view is as shown below. Figure 5-2, Options Tab, Flaresim Method
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Fluid View
Options - Correct Temperatures Drop down list: Yes/No When set to Yes the temperature of the fluid in the tip or stack riser will be corrected for the calculated pressure at each point. The correction will assume isentropic adiabatic compression or expansion from the defined fluid reference pressure to the calculation pressure. When set to No all calculations will be isothermal at the specified fluid temperature. The true nature of the expansion of gas across a PSV is between isentropic and isenthalpic. The use of an isentropic expansion correction in will give a worst case temperature correction. The default value is off. In versions of Flaresim prior to 4.0 this option was located on the Calculation Options view and applied to all fluids. Options - R-K Z Factor Drop down list: Yes/No When set to Yes the fluid compressibility factor or Z factor is calculated using the Redlich Kwong method. If set to No the method used is the Berthelot equation. The results of the two methods will be similar at low pressures (< 5 bar). At higher pressures the Redlich-Kwong method is more accurate so it is set to be the default method for all new cases from Version 1.1 onwards. Prior to Flaresim version 4.0 this option was located on the Calculation Options view and applied to all fluids. When the REFPROP fluid properties method is selected the Options tab will display the following view.
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Fluids
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Figure 5-3, Options Tab, REFPROP Method
Options - Correct Temperatures Drop down list: Yes/No When set to Yes the temperature of the fluid in the tip or stack riser will be corrected for the calculated pressure at each point. The correction will assume an adiabatic compression or expansion from the defined fluid reference pressure to the calculation pressure. When set to No all calculations will be isothermal at the specified fluid temperature. The calculation will use the specified isentropic efficiency when correcting for the pressure change between the reference pressure and the tip exit pressure. For pressures changes from the tip exit to the stack base, an isenthalpic calculation will be used i.e. an isentropic efficiency of 0%. Options - Isentropic Efficiency Range: 0 to 100% The isentropic efficiency used in when correcting the fluid temperature from the reference pressure defined to the tip exit pressure.
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Fluid View
The appropriate value to use will depend on location at which the reference temperature and pressure are defined. Depressuring of a vessel is often modelled as isentropic ie. an efficiency of 100%. Expansion due to pressure drop down a pipe is generally considered to be isenthalpic i.e. an efficiency of 0%. Expansion across a PSV is between isentropic and isenthalpic. The greatest change in temperatures will be seen with an isentropic efficiency of 100%. Options - Flash Method Drop down list: PR/NIST This sets the flash method that will be used by the REFPROP package. The default PR or Peng Robinson method is widely used in the hydrocarbon industry. The NIST method is the default method provided by the REFPROP package. The PR method is significantly faster than the NIST method. Results - Fluid State Calculated Value This displays the fluid state calculated after flashing the fluid at the reference temperature and pressure. If the fluid state is two phase or liquid then If the fluid state is two phase or liquid then the current version of Flaresim will not be able to use this fluid in its calculations. It is planned to remove this restriction to allow use of two phase fluids and liquids in Welltest burners in future versions. Results - Vapour Fraction Calculated Value This displays the calculated vapour fraction after flashing the fluid at the reference temperature and pressure.
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Fluids
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5.1.4 Composition Tab Figure 5-4, Composition Tab
Table - Component Name Selected components Shows the list of components selected for use in the model. Components are added to the list by clicking the Add Component button to open the Component List view; see Figure 5-5. Highlight one or more components in the list that you wish to add and click the OK button. The required components will be added to the component list and the Component List view will close. Components are removed from the list by clicking the Remove Component button to open the Component List view; see Figure 55. Then select one or more components that you wish to remove and click the OK button. The selected components will be removed from the current component list and the Component List view will close.
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Fluid View
Figure 5-5, Component List view
Table - Composition Values Range: 0 to 1.0 Specifies the fraction of each component in fluid on either a mole or a mass basis as determined by the radio button selection to the right of the table. Composition Basis Radio button: Mass/Mole This radio button selects the basis for the composition data. Note that changing it does not convert any existing component fraction data to the new basis. As component fractions are updated, the running total of the fractions is updated. A composition can be completed by clicking either the Normalise button to set remaining fractions to 0.0 and normalise current totals to add to 1.0 or by clicking the Calculate Last Fraction button to set a single unspecified component fraction to the value required to make the overall fraction equal to 1.0.
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Fluids
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5.1.5 Combustion Results Tab The following figure shows the Combustion Results tab. This view displays the combustion results calculated for the fluid. Figure 5-6, Fluid View, Combustion Results
These results are calculated directly from the specified composition when this is available. When the composition has not been specified, a composition is calculated for the Fluid using the defined mole weight as the basis. Essentially the composition is assumed by selecting the two straight chain hydrocarbon components, C1 through C10 from the data base that have mole weights immediately lower than and higher than the specified mole weight. The proportion of these two components is then calculated to provide the same mole weight. Fluid Ideal Enthalpies - At Fluid Temp Calculated Value: J/kg The ideal enthalpy of the fluid at the specified temperature.
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Fluid View
Fluid Ideal Enthalpies - At 25C Calculated Value: J/kg The ideal enthalpy of the fluid at 25C. Flue Gas Results - Flue Gas Flow Calculated Value: mole/mole The flow of flue gas generated by complete combustion of 1 mole of the fluid with the stoichiometric quantity of oxygen. Flue Gas Results - O2 Required Calculated Value: mole/mole The stoichiometric quantity of oxygen required for combustion of 1 mole of the fluid. Stoichiometric Flue Gas Composition Calculated Value: mole fraction The composition of the flue gas resulting from stoichiometric combustion of the fluid.
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Fluids
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5.2 Assist Fluid View The following figure shows the Assist Fluid view for entering and updating assist fluid data. Figure 5-7, Assist Fluid View
Name Text Enter a name to identify this assist fluid. Status Text Status message The message displayed in this field and its colour indicates whether the data for this Assist Fluid object is complete and ready for calculation. Type Drop down list: Air / Steam/Water Selects the type of assist fluid to be used. Steam/Water indicates that Steam will be used with vapour flares and Water with liquid flares. Flow Calculations Drop down list: User / Smokeless If this is set to User then a specific flow rate for the Assist Fluid will need to be specified when the Assist Fluid is assigned to a Tip. If set to Smokeless then the flow rate of the Assist Fluid will be calculated according to the following settings as shown in Figure 5-8. 5-15
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Assist Fluid View
Figure 5-8, Assist Fluid View for Smokeless Operation
Smokeless Method Drop down list: Flaresim/API/UserRatio Selects the method to be used by Flaresim to calculate the flow of assist fluid required for smokeless operation. The Flaresim method is a proprietary correlation supplied by National Air Oil. The API method is the method described in API RP521. The UserRatio allows the user to specify the flow ratio of assist fluid required for smokeless operation. The validity of these options varies with the type of assist fluid selected. Air The allowed methods are Flaresim and UserRatio. If the API method is selected an error message will displayed when the model is calculated. Steam/Water Any of the allowed methods may be used. Smokeless Flow Ratio Range: 0.001 to 100.0 but see description Specifies the ratio of the mass flow of the assist fluid to the mass flow of the fluid being flared. This field is displayed when the UserRatio smokeless method is selected. When Air is the assist fluid, high ratios of 5.0 or more may be used. When Steam/Water is the assist fluid the mass ratio should not exceed 0.5 since this would lead to flame instability and a potential flameout. 5-16
Fluids
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Apply Correction to Fraction Heat Radiated Check box If selected, Flaresim will calculate a correction to the flame length resulting from the assist fluid. Apply Correction to Flame Length Check box If selected, Flaresim will calculate a correction to the flame length resulting from the assist fluid.
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Assist Fluid View
Environment
6-1
6 Environment Page 6.1
Environment View . . . . . . . . . . . . . . . . . . . . 4
6.1.1 6.1.2 6.1.3 6.1.4
6.2
Common Fields . . . . . . . . . . . . . . . . . . . . . . 4 Overall Tab . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Wind Rose Tab . . . . . . . . . . . . . . . . . . . . . . 10 Dispersion Data Tab. . . . . . . . . . . . . . . . . . 13
Environment Summary View. . . . . . . . . . .15
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Environment
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The Environment object allows the definition of the data needed to model flares in different environmental conditions. The data allows characterisation of different geographical locations ranging from desert conditions to Arctic conditions or characterisation of different weather conditions at a single location. An individual Flaresim run is always carried out for a single set of environmental data. A Flaresim model file can contain multiple Environment objects to allow rapid recalculation of the model with a different set of environmental data. Environment objects may be created using the Environment option in the Add Item drop down menu or by selecting the Environment branch in the Case Navigator and clicking the Add button. An existing Environment object may be viewed by selecting it in the View drop down menu option, by double clicking it in the Case Navigator or by selecting it in the Case Navigator and clicking the View button. The Environment object to be used for calculations is set by selecting it in the Case Navigator and clicking the Activate button. Since only one set of environmental data can be active at a time, all other Environment objects will be set to Ignored. An Environment object can also be Ignored by selecting the check box on its view. One Environment object must be active and complete to allow calculations to proceed. An Environment object can be deleted either by clicking the Delete button on its view or by selecting it in the Case Navigator and clicking the Delete button on this view. A summary view showing the main details of all of the Environment objects in a case can be displayed by double-clicking the Environment branch header in the Case Navigator or by selecting the Environment branch and clicking the View button.
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Environment View
6.1 Environment View The figure below shows the Environment view for defining and updating environmental data. Figure 6-1, Environment view
6.1.1 Common Fields Name Text A descriptive name to identify this Environment object. The name supplied will be processed to remove illegal characters. Ignored Check box Clear to select this Environment object for calculations or set it to ignore this Environment object. Only one Environment can be active for calculations so activating an Environment object by clearing the 6-4
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ignored check box will automatically set all the other Environments in the model to ignored. Status Text Status message The message displayed in this field and its colour indicates whether the data for this Environment object is complete and ready for calculation.
6.1.2 Overall Tab The data items in the Overall tab of the Environment view are shown in Figure 6-1 above. Wind - Speed Range: 0 to 100 m/s A constant wind speed is assumed. In theory the windspeed varies with elevation. This variation is ignored in the calculation of the flame profile since it is not generally included in published flame shape calculation methods. The variation in wind speed with elevation is included in gas dispersion calculations - see Dispersion Data tab. The following table gives standard wind speed conversions. Note the Beaufort scale wind speed cannot be entered directly since there is no continuous or linear conversion to other windspeed measurements. knots
mph
ft/s
m/s
Beaufort Scale
0
0.0
0.0
0.0
0
2
2.3
3.3
1.0
1
4
4.6
6.6
2.0
2
8
9.2
13.5
4.1
3
12
13.8
20.3
6.2
4
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Environment View
knots
mph
ft/s
m/s
Beaufort Scale
18
20.7
30.5
9.3
5
24
27.6
40.7
12.4
6
28
32.2
47.2
14.4
7
34
39.1
57.4
17.5
8
40
46.0
67.6
20.6
9
Wind - Direction Range: 0 to 360 ° from North The direction from which the wind blows. Generally the worst or most prevalent wind direction can be determined by examination of the wind rose for the site in question. Atmosphere - Temperature Range: 10 to 500K The ambient temperature of the atmosphere is used in the calculation of the equilibrium surface temperatures of metallic surfaces exposed to the flare’s thermal radiation. It is also used in gas dispersion calculations. Atmosphere - Humidity Range: 4 to 100% The relative humidity defines the water content of the atmosphere in terms of the partial pressure of water vapour in the air relative to the vapour pressure of water at the same temperature. Standard charts are available relating the wet and dry bulb temperature measurements to the relative humidity, an example of which can be found in “The Chemical Engineers Handbook”. The humidity value is used in calculation of Transmissivity as described below. Atmosphere - Pressure Range: 0.01 to 10.0 bar a The atmospheric pressure is used to calculate the exit density of the flared gas and hence its exit velocity.
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Background - Solar Radiation Range: 0 to 100,000 W/m2 The incident solar radiation for the site. Typical values for different geographical locations are given in the following table. Location
Solar Radiation (W/m2)
North Sea
475-630
Middle East
945-1050
UK Land
630-800
Background - Noise Range: 0 to 150 dB The background noise is used as a reference noise level to which the noise from the flare system is added. The following table gives typical noise levels for everyday situations. Intensity (dB)
Situation
0
Threshold of hearing
10
Virtual silence
20
Quiet room
30
Watch ticking at 1m
40
Quiet street
50
Quiet conversation
60
Quiet motor at 1m
70
Loud conversation
80
Door slamming
90
Busy typing room
100
Near loud motor horn
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Environment View
Intensity (dB)
Situation
110
Pneumatic drill
120
Near aeroplane engine
130
Threshold of pain
Include Solar Radiation Check box Select this check box to include solar radiation in the calculation of radiation received at a point. The decision on whether to include solar radiation when designing flare systems is one for the user. API 521 recommends that this be considered on a case by case basis. Some consider it more realistic to exclude solar radiation in calculations. In deciding whether to include solar radiation consideration should be given to the frequency and duration of the flaring event, the probability of personnel being present in the exposed location, the possibility of sun and flare radiation impinging from the same general direction, the likelihood of protective clothing being worn and the ease or difficulty of escape from the exposed location. Including solar radiation leads to more conservative designs and its impact can be significant if the flare system design is controlled by low total radiation limits at longer distances from the flare. Determining whether solar radiation has been included or excluded is important when comparing flare system designs. Include Background Noise Check box Select this check box to include background noise in the calculation of total noise received at a point. Transmissivity - Method Drop down list: User/Calculated/CalcNoLimits/Wayne The value for the atmospheric transmissivity may be either specified by the user or calculated. The calculation method used is described in section 14.1.5 and estimates transmissivity as a function of the 6-8
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relative humidity at the site and the distance of the receptor from the flame. The correlation is strictly valid for distances between 30-164 m (100-500 ft) and for relative humidities greater than 10%. Outside of these ranges the correlation may still give acceptable results. If User is selected the value for the atmospheric transmissivity must be entered. If Calculated is selected the value for the relative humidity at the site must be entered. The transmissivity will be calculated, enforcing the distance limits of the correlation i.e. distances less than 30m will be set to 30m (100ft) and distances greater than 164m (500 ft) set to 164m. The minimum and maximum values of transmissivity used during the calculations will be displayed. If CalcNoLimits is selected the value for the relative humidity at the site must be entered. The calculation will be done without enforcing the distance limits of the correlation. The mi nu mum and maximum values of transmissivity used during the calculations will be displayed after calculations are complete. If Wayne is selected the transmissivity is calculated using a method that includes the effect of both relative humidity and ambient temperature - see section 14. Note a single value of calculated transmissivity cannot be displayed since in a typical Flaresim run multiple distances between individual flame elements and multiple receptor points will be considered. Tracking of each transmissivity value used would be of limited use so the compromise is to show the minimum and maximum value calculated. Calculated atmospheric transmissivities should not be selected if you are modelling hydrogen or hydrogen sulphide flares which burn with little or no luminous radiation. Transmissivity - Value Range: 0 to 1.0 Atmospheric transmissivity defines the degree of attenuation of the thermal radiation due to atmospheric conditions. It is expressed as 6-9
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Environment View
the fraction of the radiation which is received at the receptor point. It must be specified if the Transmissivity Method is set to User. A value of 1.0 should normally be taken unless exceptional circumstances are deemed applicable. A specified value of 1.0 for the transmissivity will mean no attenuation of radiation in the atmosphere and lead to a more conservative design. Transmissivity - Min Value Calculated Value The minimum value of transmissivity calculated when the Transmissivity Method is not set to User. Transmissivity - Max Value Calculated Value The maximum value of transmissivity calculated when the Transmissivity method is not set to User.
6.1.3 Wind Rose Tab The Wind Rose tab of the environment view allows a range of wind speeds from different directions to be modelled and the results plotted on a single graph for a each receptor point. There are two methods of setting up the matrix of wind speeds against direction, either for all directions at a range of wind speeds or for a specific wind speed for each direction. It is also possible to enable sizing calculations based on the Wind Rose data to calculate the sizing for each defined wind speed and direction to find the worst case. No wind rose calculations Radio button Selecting this button disables wind rose calculations. Run calculations on all wind directions for specified speeds Radio button Selecting this option activates Wind Rose calculations for all wind directions for the specified range of wind speeds. The view will
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change to display a table to enter the wind speeds to be used as shown below. Figure 6-2, Wind Rose Tab, Range of speeds for all directions
When this option is selected, multiple lines, one for each wind speed will appear on the Wind Rose plots for each Receptor point. Wind Speed Table Range: 0 to 100 m/s Define the wind speeds for which wind rose calculations are required. At least one value must be defined. Run each wind direction with a specific speed Radio button When this option is selected Wind Rose calculations will be activated for a specific wind speed for each wind direction. The view will change to allow the matrix of wind speeds to be defined as shown below.
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Environment View
When this option is selected, a single line will appear on the Wind Rose plots for each Receptor point. Figure 6-3, Wind Rose Tab, Specified speed for each direction
Wind Speed Table Range: 0 to 100 m/s Define the wind speed for each wind rose direction. A value must be defined for each direction to complete the data input. Use wind rose data for stack sizing Check box This option is available when wind rose calculations are enabled. Selecting this option will use the selected wind rose data and method during sizing calculations. Instead of the stack being sized solely to meet the wind speed and direction defined on the Overall tab of the Environment view, multiple sizing calculations will be done for each of the wind rose data points defined. The wind direction and speed used for the final sizing can be viewed on the Sizing tab of the Calculation Options view. 6-12
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Note this option will slow the calculations significantly.
6.1.4 Dispersion Data Tab The entries on the Dispersion Data tab are shown below. Figure 6-4, Dispersion Data Tab
Dispersion Data - Atm. Stability Class Drop down list: PasquillA through PasquillF This defines the atmospheric stability class to be used to characterise the atmospheric turbulence for both gaussian and jet dispersion calculations. Flaresim uses the widely used Pasquill stability class designation from A to F where A is the most turbulent or most unstable atmosphere and F the least turbulent or most stable.
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Environment View
Dispersion Data - Terrain Class Drop down list: Rural / Urban This parameter characterises the terrain roughness to be used in the gaussian dispersion calculations. Dispersion Data - Surface Roughness Range: 0.0001 to 0.3 m/s This defines the surface roughness used in jet dispersion calculations. Wind Data - Wind Reference Height Range: 0.1 to 200 m The reference height at which the wind speed is specified. This will be used together with the atmosphere and terrain characterisation information to calculate the wind speed at a given height when required. Wind Data - Correct Wind Speed For Height Drop down list: Yes/No When set to Yes the wind speed is corrected for the elevation in all calculations including radiation and temperature calculations. When set to No this correction is not applied. For dispersion calculations the correction is always applied regardless of this setting. This option is new in Flaresim version 4.0. Previous versions did not correct the wind speed for elevation in radiation and temperature calculations. The default setting for this option is No to provide consistency with earlier versions of Flaresim.
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6.2 Environment Summary View The Environment Summary view is shown below. It may be opened by selecting Environment collection branch in the Case Navigator and clicking the View button or by double-clicking the Environment collection branch. Figure 6-5, Environment Summary View
The view provides a summary of the basic information for all the Environment Objects in the case and can be used to update input data items as well as review results. Export Table Button Clicking this button opens a File Save dialog to allow the Environments summary table to be saved as a comma separated value (CSV) file, an Excel format file (XLS) or tab separated text file (TXT).
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Environment Summary View
Stacks
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7 Stacks Page 7.1
Stack View. . . . . . . . . . . . . . . . . . . . . . . . . . . 4
7.1.1 7.1.2 7.1.3
7.2
Common Fields . . . . . . . . . . . . . . . . . . . . . . 4 Stack View - Details Tab. . . . . . . . . . . . . . . . 5 Stack View - Sterile Area Tab . . . . . . . . . . . 7
Stack Summary View . . . . . . . . . . . . . . . . .10
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Stacks
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The Stack object allows definition of data to describe each flare Stack. A flare Stack or boom acts as the support for one or more flare tips and its length and orientation is a critical part of the design of a safe flare system. Flaresim offers a sizing calculation option where the length of a single flare stack can be calculated to meet a defined thermal radiation limit at a point in the site. Stack objects also provide an option for calculating the sterile area around them. This is the distance from the stack base to defined radiation and noise limits downwind of the stack. A Flaresim model may contain multiple Stack objects allowing the modelling of sites containing multiple flares. Stack objects may be created selecting the Stack menu option in the Add Items drop down menu or by selecting the Stack branch in the Case Navigator and clicking the Add button. An existing Stack object may be viewed by selecting it in the View drop down menu option; by double clicking it in the Case Navigator or by selecting it in the Case Navigator and clicking the View button. All defined Stack objects will be included in the calculations unless they have been set to Ignored. A Stack may be set to ignored by selecting it in the Case Navigator and clicking the Ignore button. An Ignored Stack object can be restored to the calculations by selecting it in the Case Navigator and clicking the Activate button. Alternatively a Stack object can be ignored and restored by setting or clearing the Ignored check box on its view. Ignoring a stack will exclude all the tips located on it from Flaresim’s calculations. A Stack object can be deleted either by clicking the Delete button on its view or by selecting it in the Case Navigator and clicking the Case Navigator Delete button. A Stack Summary view showing the main details of all of the Stack objects in a case can be displayed by double-clicking the Stack collection branch in the Case Navigator or by selecting the Stack collection branch and clicking the Case Navigator View button.
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Stack View
7.1 Stack View The following figure shows the Stack view for entering and updating stack data. Figure 7-1, Stack View
7.1.1 Common Fields Name Text Enter a name to identify this stack object. The entry will be automatically processed to remove any characters that are not allowed in file names. Ignored Check box Clear to include this stack in the calculations or set to ignore this stack when calculating. The effect of setting this check box will be
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to exclude the stack and all of the tips that are located on it from the calculations. Status Text Status message The message displayed in this field and its colour indicates whether the data for this stack object is complete and ready for calculation.
7.1.2 Stack View - Details Tab The Details tab of the Stack View is shown in Figure 8-1 above. The options on this view are. Location - Relative To Drop down list of existing locations Allows the location of the stack base to be defined relative to another object in the model, for example another stack. If left blank the location is relative to the base point of the model at 0,0,0. The following fields then define the location of the stack base relative to this location in either Cartesian or polar coordinates. Location - Northing Range: -100,000 to 100,000m The distance of the base of the stack North of the selected reference location. Updates made to this value will automatically update the polar coordinate values. Location - Easting Range: -100,000 to 100,000m The distance of the base of the stack East of the selected reference location. Updates made to this value will automatically update the polar coordinate values. Location - Elevation Range: -100,000 to 100,000m The height of the base of the stack above or below the selected reference location. Updates made to this value will automatically update the polar coordinate values.
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Stack View
Location - Radius Range: 0 to 100,000m The distance to the base of the stack from the selected reference location. Updates made to this value will automatically update the Cartesian coordinate values. Location - Angle to Horizontal Range: 0 to 90 ° The angle to the horizontal of a line from the base of the stack to the selected reference location. Updates made to this value will automatically update the Cartesian coordinate values. Location - Angle from North Range: -0 ° to 360 ° The angle from North of a line from the base of the stack to the selected reference location. Updates made to this value will automatically update the Cartesian coordinate values. Dimensions - Length Range: 0 to 500m The centre line length of the stack from the base to the tip support platform. If the stack is selected for sizing this value will be ignored and replaced by the calculated size after a successful sizing calculation. Dimensions - Angle to Horizontal Range: 0 to 90 ° The orientation of the stack relative to the horizontal. Horizontal stacks (0 ° ) are usually used for liquid flares on offshore platforms. Angled booms (30 ° , 45 ° , 60 ° ) stacks are commonly used for gas flares on offshore platforms. Vertical stacks (90 ° ) will be used for most onshore installations. Dimensions - Angle from North Range: 0 to 360 ° The orientation of the stack relative to North. Flaresim works on a 360 ° compass base thus 90 ° corresponds to a stack or boom pointing due East, 180 ° to due South etc.
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Stacks
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It is important to set the direction of the stack correctly relative to the wind direction since this will have a significant impact on the results. For most design purposes, specifying both the stack angle from North as 0 ° and wind direction as 0 ° will give a flame blowing back along the stack axis which will generally give the worst case radiation values for design of the installation. Size Me Check box Setting this check box automatically selects this stack for a sizing calculation. Note that only one stack can be selected for sizing at a time so this check box will be cleared on all other stacks when it is set. The stack that is currently being sized can be viewed on the Sizing tab of the Calculation Options view.
7.1.3 Stack View - Sterile Area Tab The Sterile Area tab of the Stack View is shown below. Figure 7-2, Stack View - Sterile Area Tab
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Stack View
This view allows the calculation of the sterile area around the stack. The sterile area is the distance downwind of the stack to a defined radiation or noise limit. The calculations are made at a defined elevation and in the case of the noise limits for a defined noise basis. The calculations are carried out for each stack individually. In a model with 2 or more stacks the sterile area for each stack will be calculated after setting all the other stacks to “Ignored”. If you need to see the sterile area for multiple stacks then this can be calculated using the Receptor Grid object (see chapter 10). The options on the Sterile Area tab as follows. Options - Sterile Area Elevation Range: -1000 to 1000 m This defines the elevation to be used for the calculation of the sterile area distances. Note that the stack base location will be used as defined. Options - Noise Basis Drop down list: Noise/NoiseA/Average Noise This selects whether the sterile area for the noise limits is to be calculated on a Noise, A-weighted Noise or Average Noise basis. Options - Calculate Sterile Area Drop down list: Yes/No When set to Yes the sterile area calculations will be performed. When set to No the sterile area calculations will be omitted. Sterile Area - Radiation / Noise Radio buttons: Radiation / Noise This selects whether the sterile area table displays the Radiation limits and distances or Noise limits and distances Sterile Area - Radiation Limit Range: 0 to 1.0e9 W/m2 This defines each radiation limit at which the sterile area will be calculated. Up to 10 values can be entered and the list will be sorted automatically from lowest to highest.
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The default values for the radiation limits in a new Stack object will be taken from the values defined in the Sterile Area tab of the Preferences view. Sterile Area - Noise Limit Range: 0 to 150.0 Db This defines each noise limit at which the sterile area will be calculated. Up to 10 values can be entered and the list will be sorted automatically from lowest to highest. The default values for the noise limits in a new Stack object will be taken from the values defined in the Sterile Area tab of the Preferences view. Sterile Area - Distance To Limit Calculated Value: m This displays the calculated downwind distance from the stack base to the defined radiation or noise limit. If the limit was not exceeded at any point downwind of the stack the words “Limit not reached” are displayed. Export Button Clicking this button displays a File Save dialog allowing the current sterile area table to exported to comma separated value (CSV) file, an Excel format file (XLS) or tab separated text file(TXT).
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Stack Summary View
7.2 Stack Summary View The Stack Summary view is shown below. It may be opened by selecting Stack collection branch in the Case Navigator view and clicking the View button or by double-clicking the Stack collection branch. Figure 7-3, Stack Summary View
The Stack Summary view shows the input data and results for all of the stacks in the case. Data input values can be updated through the summary view if required. Export Table Button Clicking this button opens a File Save dialog to allow the Stacks summary table to be saved as a comma separated value (CSV) file, an Excel format file (XLS) or tab separated text file(TXT).
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8 Tips Page 8.1
Tip View. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
8.1.1 8.1.2 8.1.3 8.1.4 8.1.5 8.1.6 8.1.7 8.1.8 8.1.9 8.1.10 8.1.11
8.2
Common Fields . . . . . . . . . . . . . . . . . . . . . . 4 Details Tab . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Noise Input Tab . . . . . . . . . . . . . . . . . . . . . 14 Location & Dimensions Tab . . . . . . . . . . . 17 Fluids Tab . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Emissions Tab . . . . . . . . . . . . . . . . . . . . . . 22 Results Tab . . . . . . . . . . . . . . . . . . . . . . . . . 25 Noise Results Tab . . . . . . . . . . . . . . . . . . . 27 Flame Shape Tab . . . . . . . . . . . . . . . . . . . . 29 Combustion Results Tab . . . . . . . . . . . . . . 31 Purge Gas Tab . . . . . . . . . . . . . . . . . . . . . . 33
Tip Dynamic View. . . . . . . . . . . . . . . . . . . . 35
8.2.1 8.2.2 8.2.3
Tip Dynamic View, Input Data Tab . . . . . . 35 Tip Dynamic View - Results Tab . . . . . . . . 37 Tip Dynamic View - Plots Tab . . . . . . . . . . 38
8.3
Size Tip View. . . . . . . . . . . . . . . . . . . . . . . . 40
8.4
Tip Summary View . . . . . . . . . . . . . . . . . . . 42
8.4.1 8.4.2
Tip Summary View - Summary Tab. . . . . . 42 Tip Summary View - Dynamic Results Tab 43
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Tips
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The Tip object allows definition of data to describe each flare tip. A flare tip acts as the disposal point for a single fluid. Multiple flare tips on one or more stacks may be present in a flare system to dispose separately of fluids due to incompatible properties e.g. warm and cold fluids, high and low pressure fluids, dry and wet fluids. Tip objects may be created using the Add-Tip drop down menu option or by selecting the Tip branch in the Case Navigator view and clicking the Add button. An existing Tip object may be viewed by double clicking it in the Case Navigator view or by selecting it in the Case Navigator view and clicking the View button. All defined Tip objects will be included in the calculations unless they have been set to Ignored. A Tip may be set to ignored by selecting it in the Case Navigator view and clicking the Ignore button. An Ignored Tip object can be restored to the calculations by selecting it in the Case Navigator view and clicking the Activate button. Alternatively a Tip object can be ignored and restored by setting or clearing the check box on its view. A Tip object can be deleted either by clicking the Delete button on its view or by selecting it in the Case Navigator view and clicking the Delete button on this view. Tip objects also have dynamic input data showing how flare flow varies with time and dynamic results for changing velocities, F Factor etc calculated from this. This data is accessed through a Tip Dynamics view which can be opened from the dynamics button in the tip view. A Tip Summary view showing the main details of all of the Tip objects in a case can be displayed by double-clicking the Tip collection branch in the Case Navigator or by selecting the Tip collection branch and clicking the Case Navigator View button. The Tip Summary view has a dynamics tab which shows the dynamic flow input data and dynamic results across all the tips.
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Tip View
8.1 Tip View The following figure shows the Tip view for entering and updating tip data. Figure 8-1, Tip Details View
8.1.1 Common Fields Name Text Enter text to identify this Tip object. Dynamics View Button Clicking the button that is visible on all the pages of the tip view will open the Tip Dynamics view, see section 8.2
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Status Text Status message The message displayed in this field and its colour indicates whether the data for this tip object is complete and ready for calculation. Ignored Check box Clear to include this tip in the calculations or set to ignore this tip when calculating.
8.1.2 Details Tab The Details tab of the Tip view, Figure 8-1, has the following data entry fields. Details - Tip Type Drop down list: Pipe / Sonic / Welltest / Combined HP/LP Selects the type of flare tip required. The nature of the fluid being flared through the tip will generally determine the type of tip selected. For gases, either the pipe or sonic tip types may be selected. Pipe flares are the simplest type of tip and may be specified for both high and low pressure gases. If the pressure available is greater than 2 bar (30 psi) at the tip then a sonic tip can be utilised. Sonic flare tips have the advantage of low flame emissivities due to more efficient combustion of the flare gas. For lower pressures a pipe flare is generally used possibly with steam or air assistance (see 5.2). Where a combined HP/LP tips is selected the HP tip is assumed to be a sonic tip and the LP a sub-sonic one. The flow ratio of HP to LP fluids should be 3 or greater. For liquids a Welltest tip type should be selected. Details - Number of Burners Range: 1 to 1000 for certain sonic flares otherwise 1 The number of individual burners which make up the tip assembly. This should be set to 1 for all tips unless the tip being used produces
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Tip View
distinct, separate flames for each burner e.g. the Mardair sonic flare tip or some types of welltest burners. Details - Seal Type Drop down list: None / Fluidic1 / Fluidic2 / Fluidic3 / Molec.1 / Molec.2 Defines the type of seal. The riser diameter (see Location and Dimensions tab) and seal type are used solely for calculation of the pressure at the base of the stack. The values calculated are to be used for preliminary review purposes only. The seal pressure drop calculations are based on proprietary data obtained from a flare vendor. There are two basic types of seal, Fluidic or Molecular:Figure 8-2 shows the general design concept for the fluidic seal. The type selection is a function of the opening as defined below Fluidic1: 50% of total area Fluidic2: 40% of total area Fluidic3: 35% of total area. Figure 8-2, Fluidic Seal
Opening
Diameter
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Figure 8-3 shows the general design concept for the molecular seal. The type selection is a function of the diameter as defined below:Molec.1: Traditional design. Maximum diameter is 1.7 times the tip diameter. The pressure drop correlation is based on a design which gives a body length of 5.5m (18ft) regardless of the tip diameter. Molec.2: Low pressure drop design. Maximum diameter is 2 times the tip diameter. The pressure drop correlation is based on a design which gives a body length which is a function of the tip diameter. Figure 8-3, Molecular Seal
Diameter
The fluidic seal has a number of advantages over the traditional molecular seal:• Lower purge gas requirements and consequent operating costs. • The seal still operates with a high efficiency even if rain water or chunks of refractory material drop into the baffles. In fact the water is quickly dissipated because the fluidic seal is located at a high temperature section of the flare stack. • Lower cost due to the simple construction and light weight. A 48" fluidic seal will typically weigh less than half the weight of a 6" molecular seal. 8-7
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Tip View
Seals are only appropriate for pipe and sonic flare tips. If the tip type is set to Welltest the seal type will be set to None automatically. Radiation Method - Method Drop down list: Global / Flaresim API / Point / Diffuse / Mixed / Brzustowski / M.Point Brzustowski / Strict API / Chamberlain Defines the methods to be used to calculate the radiation flux at a point for this flare tip. This option is only available for use if the Expert Mode option has been enabled in the Calculation Options view. It is normal to use the same radiation calculation method for all of the flares in a single model. However there may be occasions when it is desirable to use a particular radiation calculation method for a specific tip. Since the radiation flux from flare tip to a receptor point is always calculated tip by tip and then summed there is no theoretical barrier to using a different radiation method for each tip. Radiation Method - No. Flame Elements Range: 1 to 100 Defines the number of flame elements to be used to calculate the flame shape for this flare tip. This option is only available for use if the Expert Mode option has been enabled in the Calculation Options view. Some radiation methods have a requirement for a fixed number of flame elements so this input is not available for all methods. Radiation Method - Element Position Range: 0 to 100% Defines the position within a flame element to be used as the source of the radiation flux. This option is only available for use if the Expert Mode option has been enabled in the Calculation Options view. This input is not available for all radiation methods. Even where it is possible to update it, this entry should normally be left at its default value of 50%.
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F Factor Details - Method Drop down list: User specified / Natural Gas / Kent / Tan / High Efficiency / Cook / Generic Pipe / Modified Chamberlain Defines the method used to calculate the fraction of the total net heat release from the flame which is radiated. This was labelled emissivity in Flaresim prior to version 1.1. It is also known as the F Factor. The User specified option allows specification of the value by the user. Otherwise it is calculated by the selected correlation as follows:Natural gas: Correlation based on tip exit velocity assuming a natural gas fluid of molecular weight 19. Tan:
Correlation based on mole weight
Kent:
Correlation based on mole weight
High Efficiency:Proprietary correlation between tip type, exit velocity, fluid molecular weight and degree of hydrocarbon saturation. Formally known as the Flaresim method in versions prior to 1.2. Cook:
Correlation based on exit velocity.
Generic Pipe: Correlation based on refitting Kent, Tan, Natural gas and Cook methods across a range of exit velocities and molecular weights. Modified. Chamberlain: Correlation based on mole weight and exit velocity. Where flare vendor data is available it should be used in preference to a correlation. In the absence of vendor data, the Generic Pipe method is recommended for a conservative design. For clean burning, smokeless flares from well designed flare tips in good condition the High Efficiency method can be used. In practice this means flares burning paraffinic hydrocarbons of low molecular 8-9
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Tip View
weight fluid ( 0.2 mach). For fluids other than paraffinic hydrocarbons vendor advice should be sought. In the absence of advice, user specified F Factors of 0.3 to 0.4 are generally reasonable. Fraction Heat Radiated - Specified/Calculated Value Range: 0.01 to 1.0 If the Fraction Heat Radiated Method is set to User Specified then the required value for the fraction of heat radiated must be entered here. Otherwise the calculated result for the selected calculation method will be displayed after the model has been run. Typical values for different types of flare tip are given in the following table. Tip Type Pipe flare Single Burner Sonic Multiple Burner Sonic
Fraction Heat Radiated 0.25 to 0.4 0.10 0.05 to 0.1
Unsaturated hydrocarbons burn with higher quantities of luminescent carbon particles leading to values typically 10-20% greater than for saturated hydrocarbons. Correct User F Factor Drop down list: Yes / No This entry determines whether a User Specified F Factor should be corrected by the internal correlations for HP/LP tips or when an Assist Fluid is defined with the F Factor correction option enabled. This entry is only visible when a User Specfied F Factor is selected and is only active when the Expert Mode option is selected in the Calculation Options view. The application of corrections to User Specified F Factors was always enabled in Flaresim version 2.1 and earlier but this changed to always disabled in Flaresim 3.0 and 3.0.1. This option is new in Flaresim 3.0.2 to provide user control of the correction. The option
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is always automatically set to Yes and the user informed as required when a version 2.1 case is loaded. Fraction Heat Radiated - Max Value Range: 0.01 to 1.0 Defines the maximum value of the heat radiation fraction to be used for a combined flame and overrides any higher value calculated by a correlation. This field is only visible when the flare tip is a Combined HP/LP type. Flame Length Method Drop down list: API / Flaresim / Brzustowski / User Specified A/ User Specified B/Integrated This field selects the method to be used for calculating the length of the flame. This field is only activated when the Expert Mode option is enabled in the Calculation Options view. Otherwise the flame length method will be automatically selected when the Calculation Method is selected in the Calculation Options view. The allowed options are:API Flame length is calculated from heat released according to equation presented in API 521. Flaresim
Flame length is calculated from heat released using following equation. I2
Q L = I 1 ---N
where L is flame length in m Q is heat release in J/s N is number of tips The constants I1 and I2 take the following values for different tip types.
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Tip View
Tip Type
I1
I2
Pipe flare
0.00331
0.4776
Single Burner Sonic
0.00241
0.4600
Multiple Burner Sonic
0.00129
0.5000
Brzustowski
Flame length is calculated from flammability limits using Brzustowski & Sommer method.
User Specified A User Specified B User defined constants can be supplied for use with Flaresim equation given above. The difference between the A and the B method lies in the internal method used to calculate the flame shape. Both methods use the Flaresim vector method where the flame’s axial velocity reduces along the length of the flame based on a reference flame length. In the User Specified A method the API flame length is used as the reference when the flame length calculated from the user defined constants is shorter than the API flame length. In effect the axial velocity at the end of the flame will be greater than 0. The calculated flame is used as the reference when it is longer than the API length. In the User Specified B method the flame length calculated by the user defined constants is always used as the reference in the calculation. In effect the axial velocity at the end of the flame is always assumed to be 0. Flame shapes calculated using User Specified A method will be less deflected than those calculated using the User Specified B method when the calculated flame length is less than the API flame
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length. When the calculated flame length is longer than the API flame length both methods will give the same flame shape. Integrated
Where the flame length calculation is integrated with the radiation method and it is not appropriate to select an alternative e.g. Chamberlain method.
User Multiplier Range: 0 to 2 User defined value of constant I1 for flame length equation given above. This entry is only accessible when a User Specified flame length method is selected. User Power Range: 0 to 2 User defined value of constant I2 for flame length equation given above. This entry is only accessible when a User Specified flame length method is selected.
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Tip View
8.1.3 Noise Input Tab The Noise Input tab of the Tip view is shown below. Figure 8-4, Noise Input Tab
Combustion Noise - Method Drop down list: Acoustic Efficiency / Low Noise Reference / Standard Reference / User Reference Selects the noise calculation method to be used. The Acoustic efficiency method is described in section 11.3. The other methods are based on a reference spectrum of noise at a known heat release.
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When the Acoustic Efficiency method is selected the following additional fields are displayed. Figure 8-5, Acoustic Efficiency Data
Peak Frequency Drop down list: 62.5/125/250/500/1000/2000 Hz This defines the sound frequency band at which the peak noise is generated. The total sound power calculated at this frequency will be distributed across the other sound frequency bands. Efficiency Range 1.0e-10 to 1.0% The efficiency at which combustion energy is converted to sound power. Jet Noise Method Drop down list: None / Flaresim The method used to calculate the jet noise contribution. When the jet noise method is set to Flaresim the noise contribution from the flare jet is calculated from a correlation based on the exit velocity. When set to None there is no separate jet noise contribution. If the Combustion Noise method is set to Standard Reference or Low Noise Reference or User Reference the combustion sound power generated in each frequency band is calculated from a reference value at a reference combustion duty. The Standard Reference and Low Noise Reference data used in the calculation are proprietary data supplied by a flare system vendor.
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Tip View
Selecting a User Reference method displays the Reference Duty and Sound Power Table fields shown in Figure 8-4 above and described below to allow this data to be entered Reference. Duty Range: 1 to 1,000 MW Defines the reference heat release corresponding to the sound power data defined in the Sound Power Table. User Reference Spectrum Range: 1 to 200 dB Allows the user to define the sound power level at each frequency band corresponding to the heat release specified in the Reference Duty field. When a vendor supplied noise curve is available the information available can be entered by selecting User Reference for the Combustion Noise method and None for the Jet Noise method.
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8.1.4 Location & Dimensions Tab Figure 8-6, Location & Dimensions Tab
Tip Location - On Stack Drop down list: Defined stack names Defines which stack the tip is located on. The drop down list shows the currently defined stacks. Tip Dimensions - Length Range: 0 to 100m The physical length of the burner tip. The value is used in calculating the true gas exit point for flame length calculations and gas dispersion calculations. Note if the length is set to 0m the defined tip angles to horizontal and vertical will still be used to calculate the vector for the fluid jet leaving the tip, not the stack angles.
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Tip View
Tip Dimensions - Angle to Horizontal Range: -90° to 90° The orientation of the tip relative to the horizontal. Vertical installation of flare tips prevents burn back on the tip and consequent reduction in tip life. The use of inclined tips on inclined booms does have the advantage of directing both the flame and any liquid carryover away from the main platform structure. Tip Dimensions - Angle from North Range: 0 to 360° The orientation of the tip relative to the North. It is not unusual in offshore flares for the tip to be oriented along a different axis to the boom. Tip Dimensions - Diameter Range: 0.001 to 10m The internal diameter of the burner assembly. For sonic flares the equivalent diameter is calculated for resolution of the fluid jet vectors when calculating the flame shape. Tip Dimensions - Effective Area Range: 0.0001 to 100% The actual percentage of the area calculated from the tip diameter which is available for flow of the gas or liquid. A value of 100% is generally used for pipe flares. For sonic flares the value should be adjusted to ensure that the exit velocity is just sonic at the design flare rate. For liquid burners the value should be adjusted to calculate the correct exit velocity. Tip Dimensions - Riser Diameter Range: 0.001 to 10m The internal diameter of the pipe from the base of the stack to the tip. Tip Dimensions - Roughness Range: 0 to 0.001m The roughness of the riser to this tip to be used in calculating the riser pressure drop. 8-18
Tips
8-19
Tip Exit Settings - Contraction Coefficient Range: 0.01 to 1.0 The ratio of the diameter of the vena contractor to the diameter of the discharge orifice (tip). If not specified this will be calculated and the result displayed on the Results tab. Tip Exit Settings - Exit Loss Coefficient Range: 1 to 1000 The number of velocity heads which defines the exit loss for the tip. For a sonic tip the value should always be 1.0. Note that if the exit loss coefficient is specified the outlet pressure field cannot also be specified. Tip Exit Settings - Outlet Pressure Range: 10 to 10,000kPa The static pressure at the outlet of the tip, i.e at the point where the fluid emerges from the tip. Normally this will be calculated and displayed on the results tab. If specified the exit loss coefficient must be left unspecified and will be calculated. The tip exit pressure is used to calculate the properties of the gas at the exit and hence the velocity of the fluid. Calculate Burner Opening Check box Selection of the Calculate Burner Opening check box causes will result in the burner opening of a sonic tip being adjusted until the tip exit velocity is just sonic. Size Me Button The Size Me button opens a pop up window to allow the diameter of the tip to be sized for a specific exit velocity, optionally using standard pipe sizes. See section 8.3 for details.
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Tip View
8.1.5 Fluids Tab Figure 8-7, Fluids Tab
Primary Fluid - Name Drop down list: Defined Fluids Allows one of the defined fluids in your model to be assigned to the flare tip Primary Fluid - Mass Flow Range: 0 to 10,000 kg/s The mass flow rate of the fluid fed to this tip. The molar flow entry will be updated automatically. Primary Fluid - Mole Flow Range: 0 to 10,000 kgmole/s The molar flow rate of the fluid fed to this tip. The mass flow entry will be updated automatically.
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Tips
8-21
The following Secondary Fluid entries will be visible if the selected Tip type is set to Combined HP/LP. Secondary Fluid - Name Drop down list: Defined Fluids Allows one of the defined fluids in your model to be assigned to LP flare tip of a Combined HP/LP tip. Secondary Fluid - Mass Flow Range: 0 to 10,000 kg/s The mass flow rate of the fluid fed to the LP tip of a Combined HP/ LP tip. The molar flow entry will be updated automatically. Secondary Fluid - Mole Flow Range: 0 to 10,000 kgmole/s The molar flow rate of the fluid fed to the LP tip of a Combined HP/ LP tip. The mass flow entry will be updated automatically. Assist Fluid - Name Drop down list: Defined Assist Fluids Allows one of the defined assist fluids in your model to be assigned to this flare tip. Assist Fluid - Mass Flow Range: 0 to 10,000 kg/s or Calculated Defines the flow of assist fluid to the tip. When the assist fluid has been set to Smokeless Operation then this value will be calculated. Otherwise either this value or the ratio must be specified. Assist Fluid - Flow Ratio Range: 0 to 100 or Calculated The ratio of assist fluid to fluid being flared. When the assist fluid has been set to Smokeless Operation then this value will be calculated. Otherwise either this value or the flow must be specified. Flow vs Time Button Clicking this button opens the Tip Dynamic View which allows the change in flare flow with time to be defined for dynamic calculations. See section 8.2 below. 8-21
8-22
Tip View
Combustion Input - Air Ratio Range: 1 to 10 This is the ratio of combustion air drawn into the flame to the stoichiometric quantity of air required for complete combustion. It should not include any air added as an assist fluid. Typical values might be 2.0 to 3.0. The value is used in the calculation of the flame temperature. Combustion Gases - Flame Temperature Range 0 to 5000 K or Calculated This is the temperature of the flame that will be used to calculate the transmission of radiation through water shields and in gas dispersion calculations for the combustion gases. If the value is left blank it will be calculated from the heat of combustion and the specified combustion air ratio.
8.1.6 Emissions Tab Figure 8-8, Emissions Tab Default
The view above shows the default view of the Emissions tab of the Tip Object. By default the emissions data for a case is defined for all tips on the Emissions page of the Calculation Options view.
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Tips
8-23
If the Expert Mode option is set on the General tab of the Calculation Options view then the emissions input data can be updated on a tip by tip basis and the view will change to the one shown below. Figure 8-9, Emissions Tab Data Input
NOx Emission - Basis Drop down list: Mass/Heat Release / Mass/Mass Flared Fluid / Mass/Moles Flared Fluid / Sintef Method This field defines the basis used to calculate the NOx emission rate. This is either as a ratio to the heat released by the flare, the mass of flared fluid or the moles (volume) of flared fluid. Alternatively it can be calculated by the Sintef method as a function of exit velocity and tip diameter as described in the Methods chapter. NOx Emission - Rate Range depends on basis The generation rate for NOx emissions for the defined basis.
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Tip View
CO Emission - Basis Drop down list: Mass/Heat Release / Mass/Mass Flared Fluid / Mass/Moles Flared Fluid This field defines the basis used to calculate the CO emission rate. This is either as a ratio to the heat released by the flare, the mass of flared fluid or the moles (volume) of flared fluid. CO Emission - Rate Range depends on basis The generation rate for CO emissions for the defined basis. Unburnt HC Emission - Basis Drop down list: Mass/Heat Release / Mass/Mass Flared Fluid / Mass/Moles Flared Fluid This field defines the basis used to calculate the unburnt hydrocarbon emission rate. This is either as a ratio to the heat released by the flare, the mass of flared fluid or the moles (volume) of flared fluid. Unburnt HC Emission - Rate Range depends on basis The generation rate for unburnt hydrocarbon emissions for the defined basis.
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Tips
8-25
8.1.7 Results Tab Figure 8-10, Results Tab
Exit Properties - Velocity Calculated value The calculated exit velocity from this flare tip. Exit Properties - Mach Number Calculated value The calculated exit velocity from this flare tip expressed as a Mach number. Exit Properties - Volume Flow Calculated value The volume flow rate of the fluid leaving the tip at the tip conditions. Exit Properties - Calculated F Factor Calculated value The final corrected F Factor used in calculations. 8-25
8-26
Tip View
Exit Properties - Contraction Coefficient Calculated value The calculated contraction coefficient. Exit Properties - Exit Temperature Calculated value The calculated fluid exit temperature. Flame Results - Heat Release Calculated value The total heat released by the flame from this flare tip. Flame Results - Flame Length Calculated value The flame length calculated for the tip and used to determine the flame’s position for the radiation calculations. For a Pipe flare this will be the same as the API Flame Length. For Sonic flares the flame length will normally be significantly less than the API value. Flame Results - API Length Calculated value The length of the flame calculated using the method outlined in API RP521. The method assumes a pipe flare. Pressure Profile - Table Calculated values The pressure profile results table shows the calculated static and total pressures from the tip exit through to the base of the stack. The table also includes the pressure drop across the tip, seal and stack. The Total pressure reported is the static pressure plus the pressure resulting from the fluids momentum. The seal pressure drop includes any pressure drop or recovery resulting from the change in diameter between stack and tip. Pressure profiles are not calculated for Welltest or Combined HP/LP tips.
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Tips
8-27
8.1.8 Noise Results Tab Figure 8-11, Noise Results Tab
Total Noise - SPL Calculated value The sound pressure level calculated summing the individual contributions at the different frequencies. Total Noise - Ref Distance Calculated value Displays the reference distance at which the sound pressure level is calculated. It is a fixed value and cannot be changed. Display Drop down list: Table / Plot Selects whether the noise spectrum results are displayed as a table or as a graph.
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Tip View
Noise Spectrum Calculated values This table or graph shows the noise generated as a function of the sound frequency. The results show the contribution from combustion noise and jet noise as well as the total noise at each defined frequency. Export Button Allows the noise spectrum data to be saved. If the noise spectrum is currently displayed as a table, a standard file dialog box will be displayed to allow the data to be saved as an Excel XLS file or a comma separated CSV file. If the data is displayed as a plot it may be saved as a graphics file. A standard file dialog box will appear to allow the name and file type to be entered. The allowed file types are JPG, PNG, BMP, WMF or EMF.
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Tips
8-29
8.1.9 Flame Shape Tab Figure 8-12, Flame Shape Tab
End of Tip - Northing Calculated value The distance north of the end of this tip from the origin. End of Tip - Easting Calculated value The distance east of the end of this tip from the origin. End of Tip - Elevation Calculated value The height of the end of this tip relative to the origin.
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Tip View
End of Tip - Windspeed At Tip Calculated value The calculated wind speed at the tip exit. This may be different from the Active Environment when wind speed correction is enabled. Display Drop down list: Table / 3D Plot / 2D Plot - North vs. East / 2D Plot - North vs. Elevation / 2D Plot - East vs. Elevation Allows selection of the display method for the flame shape results. The flame shape is calculated using the calculation method and number of elements specified by the user in the Calculation Options view. Export Button Allows the flame shape data to be saved to an external file. If the data is displayed as a table it may be saved to an Excel XLS file or a comma separated CSV file. If it is displayed as a plot, the data may be saved to a JPG, PNG, BMP, WMF or EMF graphics file. In either case a standard file dialog box will appear to allow the name and file type to be entered.
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Tips
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8.1.10 Combustion Results Tab Figure 8-13, Combustion Results Tab
Flame Temperatures - Adiabatic Flame Temp Calculated value The flame temperature calculated by combustion of the fluid at the combustion air ratio defined on the fluids tab. Any air assist fluid flow is in addition to the combustion air. The adiabatic temperature calculation assumes no radiant heat losses from the flame. Flame Temperatures - Calculated Flame Temp Calculated value The flame temperature calculated by combustion of the fluid after allowing for heat loss from the flame due to radiation. The F Factor calculated or defined on the Details tab is used to calculate the heat loss due to radiation. The calculation is based on the combustion air ratio defined on the fluids tab with any air assist fluid flow being an addition to the combustion air. 8-31
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Tip View
Combustion Gases - Mass Flow Calculated values This table presents the calculated combustion gas mass flows. There are three types of combustion gas result presented. The basic combustion gases, CO2, H2O and others such as SO2 are calculated directly from the defined fluid composition. The number of each type of atom in each component is defined in their structure in the component database. The combustion products for each atom type are in the component library and this is used to determine the quantity of combustion gases generated. Any additional steam assist fluid is added to the quantity of H2O present. In the event that a flared fluid is defined by bulk properties data, a composition is derived from the defined mole weight. Essentially the composition is assumed by selecting the two straight chain hydrocarbon components, C1 through C10 from the data base that have mole weights immediately lower than and higher than the specified mole weight. The proportion of these two components is then calculated to provide a fluid with the same mole weight. The air components O2 and N2 are calculated based on the combustion air ratio and assist air if any. Finally the emissions components NO, CO and unburnt hydrocarbon which is expressed as CH4 are calculated according to the emissions data provided on the Emissions tab of the Tip object or the global emissions data provided on the Emissions tab of the Calculation Options object. Combustion Gases - Mole Flow Calculated values This table presents the calculated combustion gas molar flows. These are derived from the mass flows using a simple mole weight conversion.
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Tips
8-33
8.1.11 Purge Gas Tab Figure 8-14, Purge Gas Tab
Purge Input Data - Purge Fluid Drop down list of allowed purge fluids This selects the purge fluid that is to be used. The list displays all of the fluids defined in the case together with Nitrogen and Methane. Purge Input Data - Fixed Velocity Range: 0 to 10 m/s This defines a fixed purge velocity that is to be maintained. The flow of purge gas required to give this velocity will be calculated. Purge Input Data - Fixed Flow Range: 0 to 10 m3/s This defines a fixed volumetric purge flow rate that is to be maintained. The purge gas velocity and mass flow rate required to meet this target will be calculated. Purge Input Data - HUSA O2 Range: 0 to 100% This defines the percentage of oxygen that is to be used in the full HUSA method calculation for purge gas flow see methods chapter. 8-33
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Tip View
The default value of 6% is suggested in HUSA’s papers as being generally appropriate for hydrocarbon flare gas fluids with molecular weights of methane and above. Purge Input Data - HUSA Height Range: 0 to 500 m This defines the distance from the top of the stack in the full HUSA method calculation for purge gas flow. The default value of 25 ft is suggested in HUSA’s papers (see methods chapter for references) as an acceptable value that will reduce the quantity of purge gas required without leading to an unsafe condition. Note that this default does assume that it is acceptable to have a potentially explosive mixture in the top 25ft of the flare stack. Purge Results - Table Calculated Values This table shows the purge gas velocities and mass flows calculated by the different purge gas methods. Note that all calculations are based on the stack diameter not the tip diameter using purge gas properties calculated at the temperature and pressure defined for the currently selected environment. Update Purge Calcs Button Clicking this button causes the purge gas calculations to be updated for the current tip without recalculating the entire Flaresim case.
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Tips
8-35
8.2 Tip Dynamic View The Tip Dynamic view provides for the input of flow verses time data to support dynamic calculations. It also provides for display and plotting of dynamic results for the tip. Figure 8-15, Tip Dynamic View
The Tip Dynamic view is opened by clicking the button on the parent tip view or the Flow vs Time button on the fluids tab.
8.2.1 Tip Dynamic View, Input Data Tab When the Tip Dynamic view is opened for the first time the Time vs Flow table will be contain a single blank row as shown in Figure 816 below. New rows in the table are created by adding new time vs flow data values to the table.
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Tip Dynamic View
Figure 8-16, Tip Dynamic View, Starting View
Flow Basis Radio buttons: Mass / Mole Selects the flow basis for the input data Interpolation Basis Radio buttons: Linear / Spline Selects the interpolation method used to calculate the flows at times between the points defined in the time vs. flow table. Care should be taken when using the Spline method if step changes in flow are defined since extreme values of flow can be calculated as the method tries to calculate a smooth curve between data points. Clear Selected Row Button Removes the currently selected row from the input data table. Clear All Data Button Removes all the data from the input data table, returning it to the starting state.
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Tips
8-37
Input Data Table - Time Range: 0 to 10,000s The time at which the flow is defined. Input Data Table - Flow Range: 0 to 10,000 kg/s or 0 to 10,000 kgmole/s The flow in the selected basis. Note if the tip type is set to Combined HP/LP then there will be two flow data columns, one for the primary HP flow and one for the secondary LP flow. It is possible to add data by pasting in data copied from a spreadsheet using the standard CTRL-V key. If the data being pasted has more rows than are in the table then press the CTRL-V key repeatedly to add the data line by line. The data values in the table will be sorted in order of time during dynamic calculations so new time verses flow values can be added to the table in any order. The overall time for the dynamic calculations is defined as the Exposure time on the Heat Transfer tab of the Calculation Options view, see section 15.2.3. If the data supplied in the time verses flow table does not cover the exposure time then the last flow value provided will be taken as the flow for the unspecified period of the run. For example if the exposure time is 900 s (the default) and the last flow value specified is 10,000 kg/h at 300 s then the flow for the period from 300 s to 900 s will be taken as 10,000 kg/h. If dynamic calculations are run including a tip that has no time verses flow data then the base case flow defined on the Fluids tab of the Tip view will be used as a constant value for the full exposure time.
8.2.2 Tip Dynamic View - Results Tab The Results tab of the Tip Dynamic view is shown below. This provides the interpolated flows for each time step considered in the
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Tip Dynamic View
dynamic calculation along with key calculated tip results including exit velocity, Mach number, F factor, volume flow and heat release Figure 8-17, Tip Dynamic View, Results Tab
Export Results Button Clicking this button opens a File Save dialog to allow the tip dynamic results table to be saved as a comma separated value (CSV) file, an Excel file (XLS) or tab separated text file (TXT).
8.2.3 Tip Dynamic View - Plots Tab This tab allows a plot to be generated showing the variation of a selected variable with time as shown below.
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Tips
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Figure 8-18, Tip Dynamic View, Plots Tab
Plot Selection Check box Selects the result variable to be plotted. Export Plot Button Clicking this button opens a File Save dialog to allow the current plot to be saved as a graphics file. The graphic file types that can be generated are JPG, PNG, BMP, WMF or EMF.
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Size Tip View
8.3 Size Tip View The Size Tip view appears when the Size Me button on the Location & Dimensions tab of the Tip view is selected. The Size Tip view is modal and must be closed before you can interact with other Flaresim views. Figure 8-19, Size Tip View
Fluid Data - Mass Flow Range: 0 to 10,000 kg/s This field defines the mass flow that the tip is to be sized for. The value specified here will default to the value entered on the Fluids tab of the Tip view. If changed and the Ok button is used to exit the Size Tip view the mass flow on the Fluids tab will be updated. Fluid Data - Mole Flow Range: 0 to 10,000 kgmole/s This field defines the molar flow that the tip is to be sized for. The value specified here will default to the value entered on the Fluids tab of the Tip view. If changed and the Ok button is used to exit the Size Tip view the molar flow on the Fluids tab will be updated. Fluid Data - Design Mach Number Range: 0 to 1 This field defines the Mach number that the tip is to be sized for. The value is stored with the case. The tip diameter will be recalculated each time this value is updated. 8-40
Tips
8-41
Diameter Data - Use Nominal Diameters Drop down list: Yes / No Set this to Yes to constrain the tip diameters selected to those appropriate for nominal pipe diameters. Diameter Data - Schedule Drop down list: Available schedules in pipe database Set this to the required pipe schedule. When the pipe schedule is changed the new pipe schedule is searched for a nominal diameter that provides the same or greater internal diameter to that defined for the previously selected pipe. This can cause the nominal diameter to change. The calculated Mach number. is then updated. Diameter Data - Nominal Diameter Drop down list: Nominal pipe diameters for selected schedule This list box can be used to select the nominal diameter for the Tip from the selected pipe. The actual diameter will then be set by look up from the nominal diameter and the calculated Mach number will be updated. This entry will only be active when the Use Nominal Diameter setting is set to Yes. Diameter Data - Tip Internal Diameter Range: 0.001 to 10m The internal diameter of the tip. If the Mach number is specified then the calculated tip diameter is displayed here. Otherwise the tip diameter can be specified to calculate the Mach number. This field will be only be active when the Use Nominal Diameter entry is set to No. Diameter Data - Calc. Mach No Calculated value The tip Mach number calculated at the current tip diameter. Note that when a nominal diameter is selected the calculated Mach number will differ from the design Mach number.
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Tip Summary View
8.4 Tip Summary View The Tip Summary view is shown below. It may be opened by selecting Tip collection branch in the Case Navigator and clicking the View button or by double-clicking the Tip collection branch. Figure 8-20, Tip Summary View
The Tip Summary view provides two tabs. The Summary tab provides a view of the main input data items and results for all of the Tips in a case. Input data items can be updated through this tab. The Dynamic Results tab provides access to the results of the dynamic calculations for all of the tips in the case.
8.4.1 Tip Summary View - Summary Tab The Summary tab is shown above as Figure 8-20 above. The table provides for update of the main tip input data variables and display of the main results. See section 8.1 for descriptions of each variable.
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Tips
8-43
Export Table Button Clicking this button opens a File Save dialog to allow the tips summary table to be saved as a comma separated value (CSV) file, an Excel file (XLS) or tab separated text file (TXT).
8.4.2 Tip Summary View - Dynamic Results Tab The Dynamics Results tab of the Tip Summary view is shown below. It displays the dynamic calculation results for a selected variable for all the tips in a case as either a table or a plot. Figure 8-21, Summary View, Dynamic Results Tab
Result Selection Check box Selects the result variable to be displayed. Result Selection Radio buttons: Table / Plot Selects whether the selected the results are to be displayed as a table or a plot. 8-43
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Tip Summary View
Export Dynamic Results Button Clicking this button opens a File Save dialog to allow the current plot to be saved. If the results are currently displayed as a table the file can be saved s a comma separated value (CSV) file, an Excel file (XLS) or tab separated text file (TXT). If the results are displayed as a plot he graphic file types that can be generated are JPG, PNG, BMP, WMF or EMF.
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Receptors
9-1
9 Receptors Page 9.1
Receptor Point View . . . . . . . . . . . . . . . . . . 5
9.1.1 9.1.2 9.1.3 9.1.4 9.1.5 9.1.6
9.2
Receptor Point Dynamics View . . . . . . . . 20
9.2.1 9.2.2
9.3
Receptor Point Dynamics - Results Tab . 20 Receptor Point Dynamics - Plots Tab. . . . 21
Receptor Point Summary View . . . . . . . . . 22
9.3.1 9.3.2
9.4
Common Fields . . . . . . . . . . . . . . . . . . . . . . 5 Point Definition Tab . . . . . . . . . . . . . . . . . . . 6 Point Properties Tab . . . . . . . . . . . . . . . . . . 9 Point Results Tab. . . . . . . . . . . . . . . . . . . . 13 Noise Results . . . . . . . . . . . . . . . . . . . . . . . 15 Wind Rose Results. . . . . . . . . . . . . . . . . . . 16
Point Summary - Summary Tab . . . . . . . . 22 Point Summary - Dynamic Results Tab . . 23
Receptor Grid View . . . . . . . . . . . . . . . . . . 25
9.4.1 9.4.2 9.4.3 9.4.4 9.4.5 9.4.6 9.4.7 9.4.8 9.4.9
Common Fields . . . . . . . . . . . . . . . . . . . . . Grid Extent Tab. . . . . . . . . . . . . . . . . . . . . . Grid Radiation Tab . . . . . . . . . . . . . . . . . . . Grid Noise Tab . . . . . . . . . . . . . . . . . . . . . . Grid Temperature Tab . . . . . . . . . . . . . . . . Grid Concentration Tab . . . . . . . . . . . . . . . Grid Maximum Radiation Tab . . . . . . . . . . Grid Plot Overlay Tab. . . . . . . . . . . . . . . . . Grid Graphic Report Tab . . . . . . . . . . . . . .
25 26 28 29 31 32 33 35 39 9-1
Receptors
9-2
Page
9-2
Receptors
9-3
Receptors are the points at which Flaresim will calculate the thermal radiation, noise, surface temperatures and flammable gas concentrations resulting from the operation of one or more flare tips. Flaresim provides the ability to define Receptor Point objects which define a single point for the calculations and Receptor Grid objects which define a rectangular set of points in a plane. Receptor Point objects may be created using the Add-Receptor Point drop down menu option or by selecting the Receptor Points branch in the Case Navigator view and clicking the Add button. An existing Receptor Point object may be viewed by double clicking it in the Case Navigator view or by selecting it in the Case Navigator view and clicking the View button. Receptor Point objects will be calculated unless they have been set to Ignored. A Receptor Point may be set to ignored by selecting it in the Case Navigator view and clicking the Ignore button.or restored to the calculations clicking the Activate button. Alternatively a Receptor Point object can be ignored and restored by setting or clearing the check box on its view. A Receptor Point object can be deleted either by clicking the Delete button on its view or by selecting it in the Case Navigator view and clicking the Delete button on this view. Receptor Point views provide access to a Receptor Point Dynamic view which displays dynamic calculations results for the receptor point as tables or plots. A Receptor Point Summary view provides a summary of all the Receptor Points in a model, showing both base case and dynamic results. It can be opened by double clicking the Receptor Points branch in the Case Navigator. Receptor Grid objects may be created using the Add-Receptor Grid drop down menu option. A Receptor Grid can be deleted using the Delete button on its view. Alternatively a Receptor Grid can be created, viewed or deleted using the Case Navigator view in the usual way. 9-3
9-4
In addition to calculating radiation, noise, temperature and gas concentration results for each point in the grid of receptor points, the Receptor Grid object also calculates the value and location of the point of maximum radiation within its plane. Like receptor points, Receptor Grid objects will be calculated unless they have been set to Ignored. Receptor Grid objects can be ignored and restored though the check box on the Receptor Grid view or through the Case Navigator view. Receptor Grid objects provide a graphical report option to allow isopleth reports of radiation, noise hectic to be output alongside a summary of key model parameters.
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Receptors
9-5
9.1 Receptor Point View The following figure show the Receptor Point view for entering and updating stack data. Figure 9-1, Receptor Point View
9.1.1 Common Fields Name Text Enter text to identify this Receptor Point object. Dynamics View Button Clicking the button that is visible on all the pages of the receptor point view will open the Receptor Point Dynamics view, see section 9-5
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Receptor Point View
Status Text Status message The message displayed in this field and its colour indicates whether the data for this Receptor Point object is complete and ready for calculation. Ignored Check box Clear to calculate the results for this Receptor Point or set to ignore this point when calculating.
9.1.2 Point Definition Tab The Definition tab of the Receptor Point view, see Figure 9-1, has the following data entry fields. Location - Relative To Drop down list of existing locations Allows the location of the receptor point to be defined relative to another object in the model, for example the base of a stack. If left blank the location is relative to the origin point of the model at 0,0,0. The following fields then define the location of the stack base relative to this location in either cartesian or polar coordinates. Cartesian Coordinates - Northing Range: -100,000 to 100,000m The distance of the receptor point North of the selected reference location. Updates made to this value will automatically update the polar coordinate values. Cartesian Coordinates - Easting Range: -100,000 to 100,000m The distance of the receptor point East of the selected reference location. Updates made to this value will automatically update the polar coordinate values.
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Receptors
9-7
Cartesian Coordinates - Elevation Range: -100,000 to 100,000m The distance of the receptor point above or below the selected reference location. Updates made to this value will automatically update the polar coordinate values. Polar Coordinates - Radius Range: 0 to 100,000m The distance to the receptor point from the selected reference location. Updates made to this value will automatically update the cartesian coordinate values. Polar Coordinates - Angle to Horizontal Range: 0 to 90 ° The angle to the horizontal of a line from the receptor point to the selected reference location. Updates made to this value will automatically update the polar coordinate values. Polar Coordinates - Angle from North Range: 0 ° to 360 ° The angle from North of a line from the receptor point to the selected reference location. Updates made to this value will automatically update the polar coordinate values. Sizing Constraints - Radiation Range: 0 to 100,000 W/m2 The maximum thermal radiation to be allowed at this point when performing sizing calculations. The following table provides typical values for design levels of radiation at different locations. Design Radiation W/m2 15,780
Conditions
On structures and in areas where operators are not likely to be performing duties and where shelter from radiant heat is available e.g. behind equipment.
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9-8
Receptor Point View
Design Radiation W/m2
Conditions
9,470
At design flare release at any location to which personnel have access e.g. at grade below the flare or on a service platform of a nearby tower. Exposure must be limited to a few seconds, sufficient for escape only.
6,310
In areas where emergency actions lasting up to 1 minute may be required by personnel without shielding but with appropriate clothing.
4,730
In areas where emergency actions lasting several minutes may be require by personnel without shielding but with appropriate clothing.
1,890
At design flare release on the helideck of an offshore platform. This value is suggested by the Civil Aviation Authority where the helicopter rotors are stationary. If the rotors remain turning then a limit of 4,730 W/m2 can apply.
1,580
At design flare release at any location where personnel with appropriate clothing are continuously exposed.
Sizing Constraints - SPL Range: 60 to 200 dB The maximum sound pressure level to be allowed at this point when performing sizing calculations. Sizing Constraints - SPLA Range: 60 to 200 dBA The maximum A-weighted sound pressure level to be allowed at this point when performing sizing calculations. Sizing Constraints - Average SPL Range: 60 to 200 dB The maximum average sound pressure level to be allowed at this point when performing sizing calculations.
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Receptors
9-9
Sizing Constraints - Max Temperature Range: 100 to 600 K The maximum temperature to be allowed at this point when performing sizing calculations. Observed Values - Radiation Range: 0 to 100,000 W/m2 This field allows observed values of radiation at this receptor point to be defined so that they can be used by the F Factor fitting process. See Calculations chapter.
9.1.3 Point Properties Tab Figure 9-2, Receptor Point Properties Tab
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Receptor Point View
Point Properties - Emissivity Range: 0.0001 to 1.0 The emissivity of the point which will be used in the heat balance calculations to determine surface temperature. The emissivity is used to calculate the radiative heat loss from the receptor point. A typical value for steel is 0.7. Point Properties - Absorbtivity Range: 0.0001 to 1.0 The absorbtivity of the point which will be used in the heat balance calculations to determine surface temperature. It is the fraction of the radiation incident on the point that will be absorbed. A typical value for steel is 0.7. Point Properties - Area Ratio Range: 0.0001 to 10,000 The ratio of the area available to allow the receptor to lose heat to the area of the receptor exposed to the thermal radiation. A plate with one face exposed to a flare would have an Area Ratio of 2.0. Point Properties - Mass Range: 0 to 1,000,000 kg/m2 The mass per unit area at the point to be used in the calculation of the rate of surface temperature rise. Properties - Mass Cp Range: 0.1 to 10,000 J/kg/K The mass specific heat capacity of the material at the point to be used in the calculation of the rate of surface temperature rise. Properties - Initial Temperature Range: 10 to 1000 K The initial temperature of the receptor point.
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Local Environment Drop down list: Global / Available environments When set to Global the environment data used for the receptor point temperature calculations will be the same as that used for the main model. Otherwise an alternative environment object can be selected to specify environment data that is specific to this receptor point. For example if a particular receptor point is shaded from solar radiation it might be appropriate to link the point to an environment object that specifies a lower solar radiation. Other examples where a specific environment object might be useful would be to specify an environment with low or zero wind speed to account for protected points where convective cooling might be restricted. On Plane Drop down list: None / Northing-Easting / Northing-Elevation / Easting-Elevation / Maximum / User Defined This entry sets the orientation of the receptor point and it is used to calculate the angle of incidence of the thermal radiation on the receptor. The default setting is None which means that no correction for angle of incidence will be applied and the full radiation falling on the point at any angle will be calculated. This is the most conservative option. The other options are only active when the Expert Mode option is set in the Calculation Options view. Setting On Plane to Northing-Easting, Northing-Elevation or Easting-Elevation sets the point to lie in that plane. Setting the On Plane entry to Maximum will cause Flaresim to iterate on the receptor plane angle to find the angle of maximum radiation. This is not the same as None since with a multiple element flame or multiple tips radiation will strike the receptor at varying angles leading to a reduced total radiation. This option can require significant calculation time.
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Selecting the final option, User Defined, will display the following table to allow the angle of the receptor point plane to be defined. Figure 9-3, Receptor Point Plane Angle
Receptor Plane - Rotation about North - South Axis Range: -90 ° to 90 ° The angle of the receptor point plane to the North - South axis. Receptor Plane - Rotation about East - West Range: -90 ° to 90 ° The angle of the receptor point plane to the East - West axis. Changing the setting of the receptor point plane angle can significantly reduce the radiation result for a point when compared to the default setting of None. Whether it is appropriate to change this setting will depend on the nature of the point and the radiation constraint being considered. For example if the radiation constraint is for personnel exposure it would be less appropriate to change the setting since people are mobile and “rounded” and so effectively receive radiation from multiple directions. If the constraint is for a fixed structure in a known orientation however it would be more appropriate to set the receptor plane orientation. As always it is the engineer’s judgement to make the appropriate selection.
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9.1.4 Point Results Tab. Figure 9-4, Point Results Tab
Thermal Results - Radiation Calculated value The calculated thermal radiation received at the point from all of the flares in operation. Thermal Results - Temperature Calculated value The equilibrium surface temperature reached during prolonged flaring. Thermal Results - Concentration Calculated value The concentration of gas at this point due to jet dispersion of relieving fluid in flame out conditions. Note that the jet dispersion calculations have a lower concentration cut off defined on the
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Receptor Point View
Emissions tab of the Calculation Option view and that concentrations below this cut off will be reported as 0. Thermal Results - Wind Speed Calculated value The wind speed for the point that is used in the calculation of the convective cooling contribution in the temperature calculation. This can differ from the wind speed used for the main model if either the wind speed correction for elevation option is enabled or if a local environment object is selected for the receptor point. Temperature Profile - Display Radio buttons: Table / Plot Selects whether the calculated change in temperature of the receptor point with time is displayed as a table or as a graph. Export Button Allows the calculated curve of time vs. point temperature to be exported to a file. If the data is displayed as a table it may be exported to an Excel XLS file or a comma separated CSV file. If displayed as a graph it may be exported to a JPG, PNG, BMP, WMF or EMF graphics file. In either case a standard file dialog box will appear to allow the name and file type to be entered.
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9.1.5 Noise Results Figure 9-5, Noise Results
SPL Calculated value The total sound pressure level at the receptor point. It is calculated by summing the sound pressure contributions at each frequency. SPLA Calculated value The A-weighted sound pressure level calculated at the receptor point. It is calculated by summing the A-weighted sound pressure levels at each frequency. Average SPL Calculated value The sound pressure level averaged across all the frequencies.
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Receptor Point View
Display Radio buttons: Table / Plot Selects whether the sound pressure levels vs. frequency results are displayed as a table or as a graph. Export Button Allows the calculated sound pressure vs. frequency results to be exported to a file. If the data is displayed as a table it may be exported to an Excel XLS file or a comma separated CSV file. If displayed as a graph it may be exported to a JPG, PNG, BMP, WMF or EMF graphics file. In either case a standard file dialog box will appear to allow the name and file type to be entered.
9.1.6 Wind Rose Results The Wind Rose Results tab shown below displays the results of wind rose calculations. Wind Rose calculations show the radiation received at a receptor point for a range of wind directions and speeds as defined on the Wind Rose tab of the active Environment. If no wind rose results are available a message stating this will be displayed.
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Figure 9-6, Wind Rose Results
Display Drop down list: Table / Plot This controls whether the results from the wind rose calculations are displayed as a plot or as a table of results. The view will update to show the results in the format requested. Export Button Allows the calculated wind rose results to be exported to a file. If the data is displayed as a table it may be exported to an Excel XLS file or a comma separated CSV file. If displayed as a graph it may be exported to a JPG, PNG, BMP, WMF or EMF graphics file. In either case a standard file dialog box will appear to allow the name and file type to be entered.
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Receptor Point View
Button This opens a standard file open dialog to allow selection of the layout file for the graphical report of the wind rose plot. Layout file for graphical report Filename This defines the name of the graphic report layout file that will be used to generate the graphic report for this receptor point wind rose. The default value set when the Receptor Point is created is defined in the Files tab of the Preferences view. Layout files describe the background text, data items and graphics formatting instructions required to define a graphics report in an XML formatted file with the extension .LAY. Standard layout files are shipped with Flaresim to provide graphic report definitions for 1 and 2 stack systems with 1 or 2 tips on A4 and Letter paper sizes. Appendix A describes the structure and the elements that make up a layout file. Generate Graphic Report Button This creates a new graphical report window to display the wind rose results in a graphical report alongside selected data items for the model. The layout of this report is controlled by the layout file selected. The graphic report is displayed in its own window and by default is displayed as a maximised view. The graphic report window can be minimised, resized and closed using standard windows methods. A sample is shown below.
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Figure 9-7, Wind Rose Graphic report
Wind rose graphic reports can be printed using the File - Print Graphic Report menu item.
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Receptor Point Dynamics View
9.2 Receptor Point Dynamics View The Receptor Point Dynamics view shown below displays the results of the dynamic radiation, noise and temperature calculations for the receptor point. The view is opened by clicking the button on the Receptor Point view. The view contains two tabs providing a tabular view of the results and a plots view. Figure 9-8, Receptor Point Dynamics View
9.2.1 Receptor Point Dynamics - Results Tab This view shown above as Figure 9-8, displays a table of the calculated radiation, temperature, noise and concentration results for the receptor point as they vary with time in response to changes in flare flow with time.
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Export Results Button Clicking this button opens a File Save dialog to allow the Receptor Points summary table to be saved as an Excel (XLS), comma separated value (CSV) or text (TXT) file.
9.2.2 Receptor Point Dynamics - Plots Tab This view shown below, allow display of a plot of the calculated radiation, temperature, noise or concentration results for the receptor point as they vary with time. Figure 9-9, Receptor Point Dynamics View - Plots Tab
Plot Variable Check box Selects the result variable to be plotted. Export Plot Button Exports the current plot. A standard File Save dialog will allow the plot to be saved as a JPG, PNG, BMP, WMF or EMF graphics file
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Receptor Point Summary View
9.3 Receptor Point Summary View The Receptor Point Summary view is shown below. It may be opened by clicking the Receptor Point branch of the Case Navigator view and then clicking the View button. Figure 9-10, Receptor Point Summary View
This summary view for the defined Receptor Points provides two tabs. The summary tab allows easy comparison and update of the data input values and review of the results across all the points. The Dynamics tab displays the results of dynamic calculations across all of the receptor points.
9.3.1 Receptor Point Summary - Summary Tab The Summary tab of the Receptor Point Summary view is shown in Figure 9-10 above. It provides access to the main data input variables and results for each Receptor Point in the model. See section 9.1 for descriptions of each variable.
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Export Table Button Clicking this button opens a File Save dialog to allow the Receptor Points summary table to be saved as an Excel (XLS), comma separated value (CSV) or text (TXT) file.
9.3.2 Receptor Point Summary - Dynamic Results Tab The Dynamic Results tab of the Receptor Point Summary view is shown below. It displays the dynamic calculation results for a selected variable for all the receptor points in a case as either a table or a plot Figure 9-11, Receptor Point Summary - Dynamics Tab
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Receptor Point Summary View
Result Selection Check box Selects the result variable to be displayed. Result Selection Radio buttons: Table / Plot Selects whether the selected the results are to be displayed as a table or a plot. Export Dynamic Results Button Clicking this button opens a File Save dialog to allow the current plot to be saved. If the results are currently displayed as a table the file can be saved s a comma separated value (CSV) file, an Excel file (XLS) or tab separated text file (TXT). If the results are displayed as a plot he graphic file types that can be generated are JPG, PNG, BMP, WMF or EMF.
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9.4 Receptor Grid View The Receptor Grid view is shown below. Figure 9-12, Receptor Grid View
9.4.1 Common Fields Name Text Enter text to identify this Receptor Grid object. Status Text Status message The message displayed in this field and its colour indicates whether the data for this Receptor Grid object is complete and ready for calculation. 9-25
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Receptor Grid View
Ignored Check box Clear to calculate the results for this Receptor Grid or set to ignore this grid when calculating.
9.4.2 Grid Extent Tab The Grid Details tab of the Receptor Grid view, see Figure 9-12. has the following data entry fields. Grid Extent - Grid Plane Drop down list: Northing-Easting / Northing - Elevation / Easting - Elevation / Elevation - Downwind This set of radio buttons selects the orientation plane of the receptor grid. Receptor grids are set up either for one of the three orthogonal planes or the downwind plane. In Flaresim terminology, the X-Y plane is Northing-Easting, the X-Z plane is Northing-Elevation and the Y-Z plane is Easting-Elevation. Once selected the other fields are used to define the receptor grids location and extent and the fineness or coarseness of the grid. The names of these fields will be updated appropriately. For example when the orientation is set to Northing-Elevation, the offset field will be titled Easting Offset, the next group of fields will be titled Northing and the next block Elevation. For the Elevation - Downwind plane locations downwind of the origin will have a positive coordinate and locations up wind will have a negative coordinate. Crosswind offsets follow a “right hand” rule i.e. index finger indicates downwind direction, thumb indicates elevation and second finger indicates positive crosswind coordinates. Grid Extent - Offset Range: -10,000 to 10,000 m The offset of the receptor grid plane from the model origin. Minimum Range: -10,000 to 10,000 m The minimum extent of the grid in the labelled direction. 9-26
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Maximum Range: -10,000 to 10,000 m The maximum extent of the grid in the labelled direction. Number of Points Range: 1 to 1001 The number of increments that the distance between the minimum and maximum extents will be divided into. Properties - On Plane Drop down list: None / Northing-Easting / Northing-Elevation / Easting-Elevation / Maximum The orientation of the receptor and is used to determine the correction to be applied due to the angle of incidence of the receptor to the flare. This option is only active when the Expert Options check box is set in the Calculation Options view. With the default setting of receptor point orientation to None no correction for angle of incidence will be applied. This is the most conservative option. Setting the receptor point orientation to Maximum will reduce the speed of calculations significantly. Receptor Properties - Emissivity Range: 0.0001 to 1 The emissivity of each point in the grid which will be used in the heat balance calculations to determine surface temperature. Typical value for steel is 0.7 Receptor Properties - Absorbtivity Range: 0.0001 to 1.0 The absorbtivity of each point in the grid which will be used in the heat balance calculations to determine surface temperature. This is defined as the fraction of thermal radiation striking a surface that will be absorbed. Typical value for steel is 0.7.
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Receptor Properties - Area Ratio Range: 0.0001 to 10,000 The ratio of the area of the receptor available for losing heat to the area of the receptor exposed to the flare. For a flat plate with one face exposed to the flare the Area Ratio would be 2.0. Options - Noise Basis Drop down list: Noise / NoiseA / AverageNoise This entry defines whether the noise results calculated for the Receptor Grid are the Noise sound power level, the A-weighted sound power level or the Average sound power level. Receptor Grids in versions of Flaresim prior to 3.0 automatically calculated Noise sound power.
9.4.3 Grid Radiation Tab The Radiation tab of the Receptor Grid view displays a table or a plot of the calculated thermal radiation at each point in the grid as shown in Figure 9-13 below. Display Drop down list: Table / Plot Selects whether the thermal radiation results are displayed as a table or as a graph. When a new Receptor Grid is created the graph display settings are set to the defaults defined in the Preferences View, see section 4.4.3. They may then be modified by using the Zoom and Customise buttons as described in chapter 12. Export Button Allows the calculated thermal radiation results to be exported to a file. If the data is displayed as a table it may be exported to an Excel XLS file or a comma separated CSV file. If displayed as a graph it may be exported to a JPG, PNG, BMP, WMF or EMF graphics file.
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In either case a standard file dialog box will appear to allow the name and file type to be entered. Figure 9-13, Grid Radiation Tab
9.4.4 Grid Noise Tab The Noise tab of the Receptor Grid view displays a table or a graph of the sound pressure at each point in the grid. The value displayed will be the Noise, A-weighted Noise or Average Noise as specified on the Extent tab.
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Receptor Grid View
Figure 9-14, Grid Noise Tab
Display Drop down list: Table / Plot Selects whether the sound pressure results are displayed as a table or as a graph. When a new Receptor Grid is created the graph display settings are set to the defaults defined in the Preferences View, see section 4.4.3 They may then be modified by using the Zoom and Customise buttons as described in Chapter 12. Export Button Allows the calculated sound pressure results to be exported to a file. If the data is displayed as a table it may be exported to an Excel XLS or comma separated CSV file. If displayed as a graph it may be exported to a JPG, PNG, BMP, WMF or EMF graphics file. In either
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case a standard file dialog box will appear to allow the name and file type to be entered.
9.4.5 Grid Temperature Tab The Temperature tab of the Receptor Grid view displays a table or a graph of the calculated final surface temperatures at each point in the grid. Figure 9-15, Grid Temperature Tab
Display Drop down list: Table / Plot Selects whether the temperature results are displayed as a table or as a graph. When a new Receptor Grid is created the graph display settings are set to the defaults defined in the Preferences View, see section 4.4.3.
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They may then be modified by using the Zoom and Customise buttons as described in chapter 12. Export Button Allows the calculated temperature results to be exported to a file. If the data is displayed as a table it may be exported to an Excel XLS file or a comma separated CSV file. If displayed as a graph it may be exported to a JPG, PNG, BMP, WMF or EMF graphics file. In either case a standard file dialog box will appear to allow the name and file type to be entered.
9.4.6 Grid Concentration Tab The Receptor Grid, Concentration tab shows the results of the jet dispersion calculations as shown below. Figure 9-16, Grid Concentration Tab
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The jet dispersion results are only available when the jet dispersion calculations are enabled in the Calculation Options view. Display Drop down list: Table / Plot Selects whether the concentration results are displayed as a table or as a graph. When a new Receptor Grid is created the graph display settings are set to the defaults defined in the Preferences View, see section 4.4.3. They may then be modified by using the Zoom and Customise buttons as described in chapter 12. Export Button Allows the calculated concentration results to be exported to a file. If the data is displayed as a table it may be exported to an Excel XLS file or a comma separated CSV file. If displayed as a graph it may be exported to a JPG, PNG, BMP, WMF or EMF graphics file. In either case a standard file dialog box will appear to allow the name and file type to be entered.
9.4.7 Grid Maximum Radiation Tab The Maximum Radiation tab shows the results of the search for the point of maximum radiation within the grid. Figure 9-17, Grid Maximum Radiation Tab
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Maximum Radiation Input - Initial Grid Points Range: 5 to 1001 The number of divisions used on each axis when calculating the initial search grid for maximum radiation. The search for maximum radiation is initialised by searching for the maximum value in a grid of points before starting a Nelder & Mead optimisation algorithm. The default value of 11 is usually adequate but if the grid has multiple regions of high radiation a higher number might be required to avoid locating a local maximum. Maximum Radiation Input - Sizing Constraint Range: 0 to 100,000 W/m2 The maximum allowed radiation within the Receptor Grid during sizing calculations. Note using the maximum radiation within a grid as a sizing constraint is useful only for receptor grids that do not have part of a flame within the plane of the grid. Maximum Radiation Input - Calculate Max Radiation Drop down list: Yes / No Specifies whether the maximum radiation in this grid is to be calculated. Note that calculation of Maximum Radiation is not useful in grids which contain a part of the flame within the plane of the grid since the point found will be within the flame. Maximum Radiation Results - Radiation Calculated value The maximum value of radiation found within the Receptor Grid. Maximum Radiation Results - Location 1 Calculated value The location of the point of maximum radiation within the Receptor Grid, Axis 1.
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Maximum Radiation Results - Location 2 Calculated value The location of the point of maximum radiation within the Receptor Grid, Axis 2.
9.4.8 Grid Plot Overlay Tab The Plot Overlay tab of the Receptor Grid view allows the user to select and define an overlay drawing that will appear as the background picture in the various isopleth plots. File Type Radio buttons: Use External Overlay File / Use Flaresim Overlay Two types of overlay file may be used. An external file can be selected. In this case the extents or dimensions of the drawing must be specified together with the location of the Flaresim coordinate origin within the drawing. Alternatively a background overlay picture can be created as an Overlay object within Flaresim. In both cases there is a limit to the complexity of drawings that can be managed by the graphics component that Flaresim uses to generate isopleth plots. If isopleth results must be integrated with detailed plot drawings it is suggested that the isopleth results are exported as a DXF script through the File - Print Graphic Reports view, see chapter 15. This script will allow accurate integration of the isopleth results with a plot plan using external software. External File Type When the File Type is set to Use External Overlay file the options are as shown below.
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Receptor Grid View
Figure 9-18, Plot Overlay, Use External File
File Type - Name File name string This entry defines the external graphics file that will be used as a background picture for this Receptor Grids isopleth plots. Only a reference to the file is stored within the Flaresim case so the specified file must be copied separately when moving or transmitting Flaresim case files. Browse Button Clicking this button opens a File Open dialog to allow the external graphics file to be selected. External File - Details / Preview Radio Buttons Setting the radio button to Details allows the information about the drawing dimensions and Flaresim origin to be defined. Setting it to 9-36
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Preview displays the contents of the external file with an overlay showing the Receptor Grid dimensions overlaid on the drawing. The first two sets of values define the plot dimensions covered by the external file. The names of the axes displayed are updated as appropriate to the setting of the Receptor Grid orientation on the Extent tab. File Dimension - Minimum Range: -10,000m to 10,000m The minimum value for the plot dimension in the external file. File Dimension - Maximum Range: -10,000m to 10,000m The maximum value for the plot dimension in the external file. The two Flaresim Location of Origin fields define where the Flaresim 0, 0 point is located within the drawing file using the drawing files dimensions. Again the names of the coordinates are updated to match the grid orientation setting. Location of Flaresim Origin Range: -10,000m to 10,000m The coordinates of the Flaresim origin point within the drawing. Show Overlay Check box Set this to include the overlay drawing on the isopleth plots for this Receptor Grid. Reset Extent Button Clicking this button resets the external plot file dimensions to match those of the Receptor Grid.
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Receptor Grid View
External Plot File Example As an example of how these values should be set, consider the following. An external plot plan drawing is available which covers master plot plan coordinates from 1000m to 3000m in the X dimension and from 0m to 2000m in the Y dimension. In the master coordinates the flare stack is located at 2600, 1200. Assuming our Flaresim model has been run with the stack located at 0, 0 within the model and we have a Receptor Grid defined for the Northing - Easting plane. The settings required to use the plot overlay would be Northing Min = 0m Northing Max = 2000m Easting Min = 1000m Easting Max = 3000m Flaresim Origin Northing = 1200m Flaresim Origin Easting = 2600m Generally the dimensions of the plot plan should exceed those covered by the receptor grid or results can be unpredictable. In our example this would imply following dimensions for the receptor grid. Northing Minimum = -1200m Northing Maximum = 800m Easting Minimum = -1600m Easting Maximum = 400m
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Flaresim Overlay File Type When the File Type is set to Use Flaresim Overlay the options are as shown below. Figure 9-19, Plot Overlay Tab, Flaresim Overlay
Overlay Name Drop down list: Available Overlay objects This selects which of the Overlay objects defined in this case is to be used as the background drawings for the isopleth plots in this Receptor Grid. No check is made that the Overlay has the correct orientation. Show Overlay Check box Set this to include the overlay drawing on the isopleth plots for this Receptor Grid. Chapter 13 describes how to create and edit Flaresim Overlay objects.
9.4.9 Grid Graphic Report Tab The Graphic Report tab of the Receptor Grid view allows the user to display a graphical report of isopleth results or export the data points for an isopleth curve. Printing or saving of graphic reports is handled by the File - Print Graphic Reports menu option.
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Receptor Grid View
Figure 9-20, Graphic Report Tab
Button This opens a standard file open dialog to allow selection of the layout file for the graphical report. Layout File Filename This defines the name of the graphic report layout file that will be used to generate graphic reports for this receptor grid. The default value set when the Receptor Point is created is defined in the Files tab of the Preferences view. Layout files describe the background text, data items and graphics formatting instructions required to define a graphics report in an XML formatted file with the extension .LAY. Standard layout files are shipped with Flaresim to provide graphic report definitions for 1 and 2 stack systems with 1 or 2 tips on A4 and Letter paper sizes. Appendix A describes the structure and the elements that make up a layout file.
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Graphic Report Data - Variable Drop down list: Radiation / Noise / Temperature / Concentration Selects the type of isopleth to be viewed on the graphic report Radiation, Noise, Temperature or Concentration. For rapid output of all types of Graphic Report use the Print Graphic Reports menu option. Graphic Report Data - Contour Interpolation Drop down list: Linear / Cubic / BSpline Selects the method used to generate the isopleth curves from the receptor grid data points. The Linear option uses the least interpolation and as a result the points generated will be in closest agreement to the data values in the grid. However this may result in more jagged looking isopleth curves if a coarse receptor grid is used i.e. fewer points are calculated. The BSpline method offers the smoothest curves if a coarse grid is used but individual points on the curves may not show such good agreement with the original grid results. The Cubic method offers an alternative smoothing method. Graphic Report Options - Label Isopleth Curves Check box Set this to generate single letter labels for each of the isopleth curves. This allows individual curves to be more easily distinguished on black and white printed output. It is not normally required for colour output. Graphic Report Options - Use Layout File Isopleth Options Check box Set this to force the isopleth values, colour, line style and thickness to use the settings from the layout file rather than those specified within the case for this grid. Export Isopleth Points Button Clicking this button opens a File Save dialog that allows the calculated isopleth coordinates for the selected isopleth type to be
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exported. The options for saving are as a XML file, a comma separated CSV file or as an Autocad compatible script file SCR. For rapid output of all types of Graphic Report use the Print Graphic Reports menu option. View Graphic Report Button Clicking this button generates and displays on the screen a graphic report from the selected layout file for the selected variable. The graphic report is displayed in its own window and by default is displayed as a maximised view as shown below. The graphic report window can be minimised, resized and closed using standard windows methods. Figure 9-21, Sample Graphic Report
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10 Shields Page 10.1 Shield View . . . . . . . . . . . . . . . . . . . . . . . . . . 4 10.1.1 10.1.2 10.1.3 10.1.4 10.1.5
Common Fields . . . . . . . . . . . . . . . . . . . . . . 4 Definition Tab . . . . . . . . . . . . . . . . . . . . . . . . 5 Definition Tab - User Water Screen Method 5 Definition Tab - Long Water Screen Method6 Sections Tab . . . . . . . . . . . . . . . . . . . . . . . . . 8
10.2 Rectangle Builder. . . . . . . . . . . . . . . . . . . . 11 10.3 Polygon Builder . . . . . . . . . . . . . . . . . . . . . 13 10.4 Pit / Hut Builder . . . . . . . . . . . . . . . . . . . . . 15 10.5 Transform View . . . . . . . . . . . . . . . . . . . . . 17
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The Shield object models the use of water sprays or solid shields to reduce the transmission of radiation and noise. Each shield object is composed of one or more polygonal shapes or sections. Multiple sections may be defined to describe complex shield structures such as a burn pit. The transmission of radiation through a shield can be modelled either by user specified transmissivity factors or for water screens by transmissivity factors calculated from details of the screen thickness and the flame temperature. A method is also provided to calculate the effective thickness of a water screen given details of the water flow rate and other details of the water spray. The transmission of noise through a shield is defined by a user specified transmission factor. Shield objects may be created using the Add-Shield drop down menu option or by selecting the Shield branch in the Case Navigator view and clicking the Add button. An existing Shield object may be viewed by double clicking it in the Case Navigator view or by selecting it in the Case Navigator view and clicking the View button. All defined Shield objects will be included in the calculations unless they have been set to Ignored. A Shield may be set to ignored by selecting it in the Case Navigator view and clicking the Ignore button. An Ignored Shield object can be restored to the calculations by selecting it in the Case Navigator view and clicking the Activate button. Alternatively a Shield object can be ignored and restored by setting or clearing the check box on its view. A Shield object can be deleted either by clicking the Delete button on its view or by selecting it in the Case Navigator view and clicking the Delete button on this view.
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Shield View
10.1 Shield View The following figure shows the Shield view as it would appear for a newly created Shield object. Figure 10-1, Shield Details View
10.1.1 Common Fields Name Text Enter text to identify this Shield object. Status Text Status message The message displayed in this field and its colour indicates whether the data for this shield object is complete and ready for calculation.
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Ignored Check box Clear to include this shield in the calculations or set to ignore this shield when calculating.
10.1.2 Definition Tab The Definition tab of the Shield view, Figure 10-1, has the following fields. Details Radiation - Screen Type Drop down list: User / Water Screen This drop down list selects the type of shield. The User option is used for solid shields or water screens when it is desired to specify the transmissivity of the screen directly. The Water Screen option is used when it is desired the calculate the transmissivity for a known thickness of a water screen. When this field is set to User the view changes to display the Transmissivity field to allow the transmissivity to be defined. When the field is set to Water Screen the view changes to that shown in Figure 10-2 below. Details Radiation - Transmissivity Range: 0 to 1 This defines the fraction of radiation transmitted by the shield. This field is only displayed when the Type field is set to User. Details Noise - Transmissivity Range: 0 to 1 This defines the fraction of noise transmitted by the shield. The factor is applied to the noise power.
10.1.3 Definition Tab - User Water Screen Method When the Type field on the Details tab is set to Water Screen the view changes to that shown below in Figure 10-2.
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Shield View
Figure 10-2, Details Tab, User Water Screen Method
Layer Thickness Method Drop down list: User / Long This drop down list specifies the method that will be used to determine the thickness of the water screen. If the User method is selected the Layer Thickness field is displayed to allow the thickness to be specified. If the Long method is selected the fields described in section 10.1.4 will be displayed to allow details of the water screen to be provided to allow the water screen thickness to be calculated. Layer Thickness Range: 0.001 to 1000 mm This field defines the thickness of the water screen. The thickness will be used to calculate the transmissivity of the water screen as a function of the thickness and the flame temperature of the flare. This field is only displayed when the Layer Thickness Calculation option is set to User.
10.1.4 Definition Tab - Long Water Screen Method When the Shield type is set to Water Screen and the Layer Thickness Calculation is set to Long then the following fields will be displayed.
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Shields
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Figure 10-3, Details Tab, Long Water Screen Method
Water Flow Range: 0 to 1000 m3/s This field defines the water flow rate for the calculation of the water screen layer thickness using the Long method. Nozzle Diameter Range: 0 to 1000 mm This field defines the nozzle diameter for the calculation of the water screen layer thickness using the Long method. Number of Nozzles Range: 1 to 100 The number of water spray nozzles used. Droplet Velocity Range: 1 to 20 m/s This field defines the droplet velocity to be used in the calculation of the water screen layer thickness using the Long method. Calc. Layer Thickness Calculated value This field displays the thickness of the water screen layer calculated using the Long method.
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Shield View
10.1.5 Sections Tab The sections tab of the Shield view is shown below. This view lists the individual sections or panels that make up the complete shield. Each section is defined as a polygon with 3 or more points or vertices to define its extremities. The shield sections may be updated by selecting the line describing the section and then updating values in the Section Details region below and / or clicking one of the action buttons. Figure 10-4, Sections Tab
Section List List box: All defined shield sections The Section List displays all of the shield sections defined for this shield. Selecting a section in the list updates the Section Details region with the corresponding information.
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Shields
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Section List - Add Section Button Creates a new shield section. The new section will be selected automatically in the Section List box. Section List - Delete Section Button Deletes the selected shield section. Section List - Make Pit / Hut Button Opens the Pit / Hut Builder view ready to define a new shield. See 11.2. Section List - Transform Shield Button Opens the Transform view to rotate or move the shield. See 11.3. Section Details - Section Name Text This field allows the shield section to be given a descriptive name. Section Details - Add Vertex Button This button adds a new vertex to the bottom of the list of vertices for the current shield section. Section Details - Delete Vertex Button This button deletes the selected vertex from the list. Section Details - Sort Vertices Button This button sorts the list of vertices for the shield section. When using the shield section editor it is important that the list of vertices that define the section are entered in a way that each vertex is directly connected to the preceding vertex in the list in a continuous clockwise or anti-clockwise direction.
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Shield View
For example if entering the vertices to define a rectangular shield section, the four vertices, A, B, C and D must be entered as shown below.
Correct
Correct
Incorrect
If vertices are not entered in the correct order their correct extent cannot be calculated and the radiation and noise reduction results will be misleading and inaccurate. This can usually be seen as very irregular isopleths in the Receptor Grid view. The Sort Vertices button will sort a list of vertices into the correct order in most cases. Section Details - Make Rectangle Button Clicking this button opens the Rectangle Builder view, see section 11.2. This allows rapid definition of a rectangular shield section. Section Details - Make Polygon Button Clicking this button opens the Polygon Builder view, see section 11.3. This allows rapid definition of a polygonal shield section. Vertex List - Northing Range: -10,000 to 10,000 m The northing coordinate of the vertex. Vertex List - Easting Range: -10,000 to 10,000 m The easting coordinate of the vertex. Vertex List - Elevation Range: -10,000 to 10,000 m The elevation coordinate of the vertex. 10-10
Shields
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10.2 Rectangle Builder The Rectangle Builder view is shown below. Its purpose is to allow rapid creation of rectangular shield sections.This view is modal and must be completed and closed before other Flaresim views can be used. Figure 10-5, Rectangle Builder
Rectangle - Height Range: 0 to 1000m The height of the shield section. Rectangle - Width Range: 0 to 1000m The width of the shield section. Centre Point Location - Northing Range: -10,000 to 10,000m The northing coordinate of the centre of the rectangle. Centre Point Location - Easting Range: -10,000 to 10,000m The easting coordinate of the centre of the rectangle.
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Rectangle Builder
Centre Point Location - Elevation Range: -10,000 to 10,000m The elevation coordinate of the centre of the rectangle. Orientation - Angle to North Range: 0 to 360 degrees The angle from North of the rectangle. Orientation - Angle to Horizontal Range: -90 to 90 degrees The angle from horizontal of the rectangle. The default value of 90 degrees implies a vertical rectangle. OK Button Closes the Rectangle Builder view, accepting the input data. Note any existing section vertices will be replaced by the new rectangular section. Cancel Button Closes the Rectangle Builder view, discarding the input data.
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Shields
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10.3 Polygon Builder The Polygon Builder view is shown below. Its purpose is to allow rapid creation of polygonal shield sections. The most common use of this view will be to create polygonal sections of 12 or more vertices to approximate circular water sprays. This view is modal and must be completed and closed before other Flaresim views can be used. Figure 10-6, Polygon Builder
Number of Vertices Range; 3 to 100 The number of vertices that will define the extents of the shield section. The default number of 12 will approximate a circular spray shield to a reasonable accuracy though a greater number can be used if required. Radius Range: 0.1 to 1,000m The radius of the polygonal shield section i.e. the distance from the centre of the polygon to each vertex.
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Polygon Builder
Rectangle Centre - Northing Range: -10,000 to 10,000m The northing coordinate of the centre of the polygon. Rectangle Centre - Easting Range: -10,000 to 10,000m The easting coordinate of the centre of the polygon. Rectangle Centre - Elevation Range: -10,000 to 10,000m The elevation coordinate of the centre of the polygon. Orientation - Angle to North Range: 0 to 360 degrees The angle from North of the polygon. Orientation - Angle to Horizontal Range: -90 to 90 degrees The angle from horizontal of the polygon. The default value of 90 degrees implies a vertical polygon. OK Button Closes the Polygon Builder view, accepting the input data. Note any existing section vertices will be replaced by the new polygon data. Cancel Button Closes the Polygon Builder view, discarding the input data.
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10.4 Pit / Hut Builder The Pit / Hut Builder view is shown below. The function of this view is to create the multiple shield sections that make up a burn pit or alternatively a protective hut. It will automatically create 4 rectangular wall sections and a rectangular base or roof section. This view is modal and must be closed before other Flaresim views can be used. Figure 10-7, Pit / Hut Builder
Details Radio button: Pit / Hut Selects whether the view will define data for a pit or a hut. In both cases 4 vertical rectangular walls and a horizontal rectangular section will be created from the data supplied. In the case of a Pit the horizontal section will form the base of the burn pit while for a Hut the horizontal section will form the roof. Length (Northing Dimension) Range: 0.1 to 1,000m The length of the burn pit/hut. The length is assumed to be the dimension in the north-south direction.
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Pit / Hut Builder
Width (Easting Dimension) Range: 0.1 to 1,000m The width of the burn pit/hut.The width is assumed to be the dimension in the east-west direction. Depth / Height Range: 0.1 to 1,000m The depth of the burn pit or the height of the hut. Rectangle Centre - Northing Range: -10,000 to 10,000m The northing coordinate of the centre of the burn pit or hut base. Rectangle Centre - Easting Range: -10,000 to 10,000m The easting coordinate of the centre of the burn pit or hut base. Rectangle Centre - Elevation Range: -10,000 to 10,000m The elevation coordinate of the centre of the burn pit or hut base. OK Button Closes the Pit/Hut Builder view, accepting the input data. Note any existing shield section data will be replaced by the new pit/hut data. Cancel Button Closes the Pit Builder view, discarding the input data.
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Shields
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10.5 Transform View The Transform view is shown below. The purpose of this view is to relocate or rotate an existing shield section. It is used by entering the data required to define the move or rotation and then clicking the Apply button Figure 10-8, Transform View
Move Section - North Range: -10,000 to 10,000 m This defines the distance the shield sections are to be moved in the north-south direction. Move Section - East Range: -10,000 to 10,000 m This defines the distance the shield sections are to be moved in the east-west direction. Move Section - Elevation Range: -10,000 to 10,000 m This defines the distance the shield sections are to be moved up or down.
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Transform View
Rotate Section - Angle to North Range: -360 to 360 degrees This defines the amount the shield sections are to be rotated from North i.e. around a vertical axis. Rotate Section - Angle to Horizontal Range: -360 to 360 degrees This defines the amount the shield sections are to be rotated from the vertical i.e. around a horizontal axis. Rotation Centre Point - Northing Range: -10,000 to 10,000 m This defines the north coordinate for the centre of rotation to be used when rotating the shield sections. Rotation Centre East Range: -10,000 to 10,000 m This defines the east coordinate for the centre of rotation to be used when rotating the shield sections. Rotation - Centre Elevation Range: -10,000 to 10,000 m This defines the elevation coordinate for the centre of rotation to be used when rotating the shield sections. Apply Transform To All Sections Check box If this check box is set then the transform will be applied to all of the sections of the shield. If not it will only be applied to the section that was selected when the Transform button was clicked. OK Button This closes the Transform view and applies the specified movement or rotation to the shield section. Cancel Button Close the Transform view, discarding any defined transformation data. 10-18
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In applying a transform for simultaneous movement and rotation the order in which these are applied is firstly movement, secondly rotation from North around the vertical axis and finally rotation from horizontal around the horizontal axis. The effect of a given transform is not always obvious and it is suggested that more complex movements be done in single steps to avoid possible confusion.
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Transform View
Dispersion
11-1
11 Dispersion Page 11.1 Dispersion View . . . . . . . . . . . . . . . . . . . . . . 4 11.1.1 11.1.2 11.1.3 11.1.4 11.1.5 11.1.6
Common Fields . . . . . . . . . . . . . . . . . . . . . . 4 Input Data Tab. . . . . . . . . . . . . . . . . . . . . . . . 5 Pollutants Tab. . . . . . . . . . . . . . . . . . . . . . . . 8 Results Tab . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Plot Overlay Tab . . . . . . . . . . . . . . . . . . . . . .11 Graphic Report Tab . . . . . . . . . . . . . . . . . . .11
11.2 Implementation Details . . . . . . . . . . . . . . . 12
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Dispersion
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The Dispersion object provides a Gaussian dispersion calculation to model the dispersion of combustion gases from burning flares and dispersion of relieved fluid in the event of a flame out condition. Gaussian dispersion is a simple model of gas dispersion appropriate for a first pass screening of emissions from a flare system. In its current implementation in Flaresim it is suitable for buoyant fluids only and does not include modelling of terrain or structure effects, both of which can have a significant impact on dispersion results. The Dispersion object allows generation of contour isopleth results for a single pollutant or a simple downwind plot for multiple pollutants. The source of pollutants is either the calculated combustion gas or the components in the relieved fluid. Multiple Dispersion objects can be defined to carry out different calculations. Dispersion objects may be created selecting the Add-Dispersion drop down menu option or by selecting the Dispersion branch in the Case Navigator and clicking the Add button. An existing Dispersion object may be viewed by double clicking it in the Case Navigator or by selecting it in the Case Navigator and clicking the View button. Dispersion objects will be included in the calculations providing that the appropriate option has been selected in the Calculation Options view unless they have been set to Ignored. A Dispersion may be set to ignored by selecting it in the Case Navigator and clicking the Ignore button. An Ignored Dispersion object can be restored to the calculations by selecting it in the Case Navigator and clicking the Activate button. Alternatively a Dispersion object can be ignored and restored by setting or clearing the Ignored check box on its view. A Dispersion object can be deleted either by clicking the Delete button on its view or by selecting it in the Case Navigator and clicking the Case Navigator Delete button.
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Dispersion View
11.1 Dispersion View The following figure shows the Dispersion view for entering and updating Dispersion data. Figure 11-1, Dispersion View
11.1.1 Common Fields Name Text Enter a name to identify this Dispersion object. The entry will be automatically processed to remove any characters that are not allowed in file names. Status Text Status message The message displayed in this field and its colour indicates whether the data for this Dispersion object is complete and ready for calculation. 11-4
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Ignored Check box Clear to include this Dispersion in the calculations or set to ignore this Dispersion when calculating. The effect of setting this check box will be to exclude the Dispersion object from the calculations. Dispersion objects will only be considered for calculation if the appropriate option is set in the General tab of the Calculations Options view.
11.1.2 Input Data Tab The Input Data tab of a newly created Dispersion object is as shown in Figure 11-1 above. The following fields determine the type of Dispersion calculation that will be performed. Pollutant Source Radio buttons: Combustion Product / Unburnt Flared Fluid If the combustion product option is selected the list of pollutant components will be loaded from the combustion gas compositions calculated for the flare tips in the model. If the Unburnt Flared Fluid option is selected the list of pollutant components will be loaded from the component lists of the fluids in the model. If the flared fluids are defined by bulk properties then no dispersion modelling can be performed for the flared fluid. Combustion gas modelling can still be done in this case since the combustion gas composition can be calculated using an assumed composition. Calculation Type Radio buttons: Contour Plot / Downwind Line Plot The dispersion calculations can be performed to generate either a composition isopleth contour plot for a single pollutant or a plot of mu lip le pollutant compositions along a single line downwind of a selected origin.
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Dispersion View
Contour Plot Data Entry The data entry items for a contour plot dispersion calculation are shown below. Figure 11-2, Contour Plot Data Entry
Contour Plot Extent - Contours Height Range: 0m to 1,000 m The height of the contours plane. All contours are generated for a horizontal plane i.e. a Northing-Easting orientation. Northing - Minimum Range: -50,000 to 50,000 m The minimum extent of the contour plot in the northing direction. Northing - Maximum Range: -50,000 to 50,000 m The maximum extent of the contour plot in the northing direction. Northing - Number of Points Range: 1 to 1001 The number of increments that the distance between the minimum and maximum extents will be divided into.
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Easting - Minimum Range: -50,000 to 50,000 m The minimum extent of the contour plot in the easting direction. Easting - Maximum Range: -50,000 to 50,000 m The maximum extent of the contour plot in the easting direction. Easting - Number of Points Range: 1 to 1001 The number of increments that the distance between the minimum and maximum extents will be divided into.
Downwind Line Plot Data Entry The data entry items for a contour plot dispersion calculation are shown below. Figure 11-3, Downwind Line Plot Data Entry
Line Plot Details - Line Through Point Drop down list: Origin and defined tip exit locations This entry defines the point on which the downwind line calculation is based. The downwind distances specified are calculated from this selected point. 11-7
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Dispersion View
Line Plot Details - Height For Calculation Range: 0m to 1,000 m The height at which the pollutant concentrations are to be calculated. Downwind Distance - Minimum Range: 0 to 50,000 m The minimum downwind distance for the line plot. Downwind Distance - Maximum Range: 0 to 50,000 m The maximum downwind distance for the line plot. Downwind Distance - Number of Points Range: 1 to 1001 The number of increments that the distance between the minimum and maximum extents will be divided into.
11.1.3 Pollutants Tab Figure 11-4, Pollutants Tab
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Dispersion
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The Pollutants tab view shows a list of the pollutant components found in the selected Pollutant source. If this is set to combustion gases all of the combustion results for each active tip are scanned to complete the list of pollutants though the O2 and N2 components are not added to the list. If the source is set to Flared Fluid all of the active fluid compositions in the case are scanned. If all of the active fluids are defined by bulk properties then the pollutant list will be empty. Plot Check box Set the check box for the pollutants that should be included in the dispersion calculations. For a contour calculation only one component may be selected. Multiple components can be selected for a downwind line plot.
11.1.4 Results Tab Figure 11-5, Results Tab, Downwind Line Results
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Dispersion View
The view above shows the results obtained for a downwind line plot dispersion calculations. The view below shows the results for a contour calculation. In both cases the Display and Export options available are the same. Figure 11-6, Results Tab, Contour Results
Display Drop down list: Table / Plot Selects whether the dispersion results are displayed as a table or as a graph. When a new Dispersion object is created the graph display settings are set to the defaults defined in the Preferences View, see section 5.4. Export Button Allows the calculated thermal radiation results to be exported to a file. If the data is displayed as a table it may be exported to an Excel XLS file or a comma separated CSV file. If displayed as a graph it 11-10
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may be exported to a JPG, PNG, BMP, WMF or EMF graphics file. In either case a standard file dialog box will appear to allow the name and file type to be entered. The contour plot view may be customised using the Zoom and Customise options as described in Chapter 13.
11.1.5 Plot Overlay Tab The options in the Plot Overlay tab of the Dispersion object apply to the contour plot calculation type only. Their operation is identical to that described for the Plot Overlay tab of the Receptor Grid object, see section 10.3.8.
11.1.6 Graphic Report Tab The options in the Graphic Report tab of the Dispersion object apply to the contour plot calculation type only. Their operation is identical to that described for the Graphic Report tab of the Receptor Grid object, see section 10.3.9. Graphic Reports are not available for the downwind line plot dispersion option.
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Implementation Details
11.2 Implementation Details The Flaresim Gaussian dispersion calculations make the following key assumptions in their implementation. A. The gas is assumed to be buoyant. In the case of the combustion gases this is a reasonable assumption at normal flame temperatures. In the case of the uncombusted flared fluid, a check is made to confirm that the temperature/mole weight of the fluid leads to a gas density that is lighter than air at 120C as a precondition for running the calculations. B. The combustion gas source is assumed to be the end of the flame. The Flame Shape tab of the Tip view can be used to see the location of the end of the flame. C. Multiple sources are summed to provide a final result If multiple sources are specified in a model i.e. there are multiple tips then the dispersion results are calculated for each individual tip and then summed to give the final result. D. Minimum Distance is 100m The dispersions coefficients used are calculated from correlations that were validated for a minimum distance of 100m downwind of the source. While Flaresim may calculate Gaussian dispersion results at closer distances they should be regarded as extrapolations and of low reliability.
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Overlays And Isopleths
12-1
12 Overlays And Isopleths Page 12.1 Overlay View. . . . . . . . . . . . . . . . . . . . . . . . . 4 12.1.1 12.1.2 12.1.3 12.1.4 12.1.5 12.1.6
Common Fields . . . . . . . . . . . . . . . . . . . . . . 4 Details Tab . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Editor Tab . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Overlay Editor Tool bar . . . . . . . . . . . . . . . . 7 Overlay Editor - Object Properties . . . . . . 10 Overlay Editor - Edit Mode . . . . . . . . . . . . 13
12.2 Zoom View . . . . . . . . . . . . . . . . . . . . . . . . . 15 12.3 Isopleth Customise View . . . . . . . . . . . . . .17 12.3.1 12.3.2 12.3.3
Plot Details Tab. . . . . . . . . . . . . . . . . . . . . . 18 Contour Details Tab . . . . . . . . . . . . . . . . . . 21 Text Details Tab . . . . . . . . . . . . . . . . . . . . . 22
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Overlays And Isopleths
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Page
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Overlays And Isopleths
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Overlays are drawings such as plot plans created in Flaresim to add as background pictures to isopleth plots to show graphically the extent of the isopleths. The overlay editor provided allows creation of simple drawings but is not a a substitute for a full graphics program. Externally created files can also be used as background pictures - see the Plot Overlay tab of Receptor Grid and Dispersion views. Overlay objects may be created using the Add-Overlay drop down menu option or by selecting the Overlay branch in the Case Navigator view and clicking the Add button. An existing Overlay object may be viewed by double clicking it in the Case Navigator view or by selecting it in the Case Navigator view and clicking the View button. Overlay objects can be used by one or more Receptor Grid or Dispersion objects (client objects). Overlays are selected and their display is controlled through the Plot Overlay tab of the client object view. Overlay objects can be deleted by selecting them in the Case Navigator and clicking the Delete button or by using the Delete button on their view. Isopleth Zoom and Isopleth Customisation views are accessible from all isopleth display tabs. These include the Radiation, Noise, Temperature and Concentration tabs of the Receptor Grid views and the Results tab of the Dispersion object view when used for dispersion contour calculations. The Zoom and Customisation views allow the appearance of individual isopleths to be manipulated. Isopleth Zoom and Isopleth Customisation views pop up alongside a particular isopleth display and will close automatically when that display is closed.
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Overlay View
12.1 Overlay View The following figure show the Overlay view for creating and modifying overlay pictures. Figure 12-1, Overlay View
12.1.1 Common Fields Name Text Enter text to identify this Receptor Point object.
12.1.2 Details Tab The Details tab of the Overlay view, see Figure 12-1, has the following data entry fields.
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Overlay Type -Overlay Plane Drop down list: Northing-Easting / Elevation-Northing / Elevation-Easting Defines the plane of the Overlay drawing. Selection of the plane automatically updates the labels for the remaining entries in the this tab. File Dimension - Minimum Range: -50,000 to 50,000 m The minimum extent of the overlay drawing in the labelled direction. File Dimension - Maximum Range: -50,000 to 50,000 m The maximum extent of the overlay drawing in the labelled direction. Update Details From Grid / Dispersion - Select Drop down list: All Grids and Dispersions in Case This drop down provides a list of all of the Receptor Grid and Dispersion objects in the case so that it can be used as the basis for setting the Overlay dimensions. Update Details From Grid / Dispersion - Update Button Clicking this copies the orientation and each axis minimum and maximum dimensions from the selected Receptor Grid or Dispersion object. This is a one-off copy and no link is made between the Overlay and the selected source object.
12.1.3 Editor Tab The Overlay Editor tab allows the creation and modification of background graphics from scratch. The view shown below has three main sections, the tool bar, the information and setting region and the drawing display.
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Overlay View
Figure 12-2, Editor Tab
Current Location - X Loc Cursor location in selected units This updates as the mouse is moved around the drawing to show the X location of the cursor. Current Location - Y Loc Cursor location in selected units This updates as the mouse is moved around the drawing to show the Y location of the cursor. Show Stacks Check box If this check box is set the stacks will be added to the displayed overlay drawing to act as guides for other drawing actions. Clearing the check box clears the stack and tip elements. The stack drawing elements will not form part of the saved Overlay. The setting is not saved.
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The stack elements shown are the projection of the stack onto the Overlay plane i.e. vertical stacks will appear as a point on an Overlay with a Northing-Easting orientation. Refresh Button Clicking this button updates any open Receptor Grid or Dispersion isopleth plot views that are using the current Overlay so that they display the latest version of the Overlay. Newly opened isopleth views and report graphics always display the latest Overlay version.
12.1.4 Overlay Editor Tool bar Figure 12-3, Overlay Editor Tool bar
The icons on this tool bar may be clicked to perform the following actions or select a drawing mode. A blue box is shown around the current active icon. Opens a file to import into the current Overlay. A standard windows File Open Dialog will be displayed to allow the file to be selected. Allowed types of input file are JPG, PNG, BMP, WMF or EMF standard Windows file types, Flaresim version 2 overlays FSG and Flaresim version 3 overlays FSO. The imported file will replace the current drawing. If you want to add an external file to an existing Overlay use the Add Picture option . Exports the current Overlay picture. A standard windows File Save Dialog will be displayed to allow the export file to be selected. The file may be saved as a JPG, PNG, BMP, WMF or EMF file.
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Overlay View
Puts the drawing in selection and edit mode. When this icon is selected, clicking objects in the drawing selects them for editing, as described in section below.
Puts the drawing in Add Line mode.selection When this icon is selected, clicking and dragging in the drawing will create a new line. Puts the drawing in Add Rectangle mode. When this icon is selected, clicking and dragging in the drawing will create a new rectangle. Puts the drawing in Add Rounded Rectangle mode. When this icon is selected, clicking and dragging in the drawing will create a new rounded rectangle. Puts the drawing in Add Ellipse mode. When this icon is selected, clicking and dragging in the drawing will create a new ellipse or circle. Puts the drawing in Add Polyline mode. When this icon is selected, the first click will start a multiple segment line and each subsequent click adds a new segment. Double clicking or the Esc key indicate completion of the Polyline. Puts the drawing in Add Polygon mode. When this icon is selected, the first click will start a drawing a polygon and each subsequent click adds a new side to the polygon. Double clicking or the Esc key indicate completion and closure of the Polygon. Puts the drawing in Add Text mode. Click the left mouse button at the point where the text is to start - a vertical blinking line will be displayed. Type the text and finish by hitting the enter key.
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Puts the drawing in Add Picture mode. Using the Add Picture mode is a two step process. First as soon as the icon is clicked a File Open dialog will appear to allow selection of the picture to be added. A JPG, PNG, BMP, WMF or EMF file can be selected. After file selection, clicking and dragging in the drawing will define a box within which the picture from the file will be drawn. A single picture can be added to the drawing multiple times. To change the picture being added, click the icon again. Displays a drop down list to allow selection of the properties for new objects or to change the style of an existing object. The options in the list are shown below and their usage is covered below. Figure 12-4, Object Properties Drop Down
Displays a drop down list to allow the rearrangement of the relative positioning, orientation or grouping of the selected object in Edit Mode. The options in the list are shown below and their usage is covered below.
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Overlay View
Figure 12-5, Object Arrange Drop Down
Zooms in on the overlay drawing i.e. displays the drawing at a larger scale. Scroll bars will appear if required and can be used to scroll around the drawing. Zooms out on the overlay drawing i.e. displays the drawing at a smaller scale. Displays the currently selected zoom size of the drawing as a percentage of the full size. Drop down button can be used to select pre-defined zoom percentages.
12.1.5 Overlay Editor - Object Properties The Overlay Editor is object based and the colour and drawing style of each object are set using the drop down list. This drop down sets the object properties for new objects added in Draw Mode or changes the properties of objects selected in Edit Mode. The properties in the drop down list that can be set are. Line Colour This displays a standard windows Colour Selection Dialog as shown below. Click the colour required and then the Ok button. The selected colour applies to individual line objects, polyline objects and the outside lines for rectangle, rounded rectangle, ellipse and polygon objects. 12-10
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Figure 12-6, Colour Selection Dialog
Line Style This displays the following dialog to allow the line width and line style to be selected. Enter the line width required and select the line style from the drop down list then click Ok. The selected style applies to individual line objects, polyline objects and the outside lines for rectangle, rounded rectangle, ellipse and polygon objects. Figure 12-7, Line Style Selection
Fill Colour This displays the standard windows Colour Selection Dialog as shown above. The selected colour applies to the interior of rectangle, rounded rectangle, ellipse and polygon objects.
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Overlay View
Fill Style This displays the following dialog. Select the Fill style from the drop down list and click Ok. The selected fill style applies to the interior of rectangle, rounded rectangle, ellipse and polygon objects. Figure 12-8, Fill Style Selection
Background Colour This displays the standard windows Colour Selection Dialog as shown above. The selected colour applies background colour of the plot. Text Colour This displays the standard windows Colour Selection Dialog as shown above. The selected colour applies to the text objects. Text Font This displays a standard windows Font Properties Dialog as shown below. Select the font name, size and style and click Ok. Note that the font size selected has to be scaled for use on the overlay and so a given point size may not display with the exact height requested.
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Figure 12-9, Font Properties Dialog
12.1.6 Overlay Editor - Edit Mode In Edit mode it is possible to modify existing objects in the plot overlay. Edit mode is selected by clicking the button in the tool bar. Once the editor is in edit mode the cursor will change to show a simple arrow. Edit mode can be used to move, resize, change the properties or change the arrangement of the objects that make up a plot overlay. Selecting Objects A single object can be selected by clicking on it with the left mouse button. Once selected the object will display white boxes at the corners and sides of its bounding rectangle as shown below. Figure 12-10, Selected Object
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Overlay View
Multiple objects can be selecting by clicking and holding the left mouse button to draw a rectangle around multiple objects. In this case grey boxes are displayed at the corners and sides of the rectangles bounding each selected object. Alternatively hold down the Shift key and click to select multiple objects. Resizing Objects A selected object can be resized by moving the cursor over one of the white boxes in the bounding rectangle. When the cursor changes to a two headed arrow, click and hold the left mouse button then drag to resize the object. Moving Objects An object can be moved by clicking and holding the left mouse button on the object and dragging the object to the new position. The cursor will show a four arrowed icon. To move multiple objects first select them then click and drag one of the them. Changing Object Properties The properties of an object can be changed by selecting it then using the drop down to select the property to be changed. Rotating and Flipping Objects Objects can be rotated or flipped by selecting it then using the drop down to select the angle of rotation or horizontal or vertical flip. Changing Object Stacking Order The stacking order of objects, i.e. whether one object is displayed in front or behind another object, is set by selecting it then using the drop down to bring the object forward or in front of other objects or send it backwards or behind other objects. Grouping or Ungrouping Objects Multiple objects may be grouped together by selecting them and then using the group option from the drop down. The group of objects can then be treated as a single object for other transformations. A grouped object can be broken into individual objects again by selecting it and using the ungroup from the same drop down menu. 12-14
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12.2 Zoom View The Zoom view shown below will appear on clicking the Zoom button on a Receptor Grid isopleth or a Dispersion object contour plot. The view will appear beside the parent object view and will remain open until closed or until a different tab is selected in the parent object. More than one Zoom view can be open at a time. Figure 12-11, Zoom View
The zoom view allows the isopleth to be rescaled to zoom in on a particular section of the isopleth and view its contents in more detail. This is done without recalculating the results, all isopleths drawn will be calculated by interpolation from the original results. There are two ways of establishing the new scale for the isopleth plot axes. Firstly, when the Zoom view is open, moving the cursor over isopleth shows a cursor. When this is displayed you can click and drag in the isopleth to select the new zoom region. The updated scale values will be displayed in the Zoom view. Alternatively the Zoom extents can be set through the zoom view. Zoom Extents - Min Range: Constrained by isopleth extents Enter the minimum scale value for the axis.
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Zoom View
Zoom Extents - Max Range: Constrained by isopleth extents Enter the minimum scale value for the axis. Note the labels for the Min and Max entries will be updated according to the orientation of the parent object isopleth. Apply Button Clicking this button redraws the isopleths with the current zoom extents. Reset Button Clicking this button sets the zoom extents back to the original Receptor Grid or Dispersion extents and redraws the isopleths. Update Extents From Zoom Button Clicking this button copies the current zoom extents to the input extents of the parent Receptor Grid or Dispersion object. Since this effectively changes the input data for the grid the current results will be cleared. The case must be recalculated before any new isopleth results can be viewed. Update All Isopleths in this Grid Button Clicking this button copies the zoom extents for the current isopleth to the other isopleths of the same Receptor Grid. For example updated zoom extents on the Radiation isopleth can be copied to the Noise, Temperature and Concentration isopleths. It should be emphasised again that the number and range of points calculated are specified on the Extent tab of a Receptor Grid or the Input Data tab of a Dispersion object. Expanding the scale of the plots using the zoom feature does not add any detail to the calculations. To do this you must update the Grid or Dispersion extents and recalculate.
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Overlays And Isopleths
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12.3 Isopleth Customise View The Isopleth Customise view shown below will appear on clicking the Customise button on a Receptor Grid isopleth or a Dispersion object contour plot. The view will appear beside the parent object view and will remain open until closed or until a different tab is selected in the parent object. More than one Isopleth Customise view can be open at a time. Figure 12-12, Isopleth Customise View
There is one button on this view. Update All Isopleths of This Type Button Clicking this button copies the settings for this isopleth to all other isopleths of the same type in the case. For example if you click the button when updating a Radiation isopleth, the Radiation isopleths of all other Receptor Grids in the case will be updated. The detailed customisation settings are split across three tabs.
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Isopleth Customise View
12.3.1 Plot Details Tab The Plot Details tab of the Isopleth Customisation view is shown as Figure 12-12. Plot Details - Display Grid Check box When selected plots will show a background grid. Plot Details - Display Flame Check box When selected isopleth plots will show a line representing the shape of the flames from any active flare tips. Plot Details - Display Stack Check box When selected isopleth plots will show lines representing the size and orientation of active flare stacks. Plot Details - Display Tip Check box When selected isopleth plots will show lines representing the size and orientation of active flare tips. Plot Details - Display Shield Check box When selected isopleth plots will show lines representing the intersection of active shield sections with the plane of the isopleth. Note that it is the intersection that is displayed not the projection of the shield on the isopleth. If plan view isopleth is at ground level i.e. 0m then the shields will require at least one point with an elevation dimension < 0m in order to intersect with the isopleth plane. Plot Parameter - Number of lines Integer range: 1 to 9 This value determines the number of grid lines that will be displayed for each axis of the isopleth plots.
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Plot Parameter - Flame Thickness Integer range: 1 to 50 This values defines the width in pixels of the line that will be drawn to represent the flame shape. Plot Parameter - Stack Thickness Integer range: 1 to 50 This values defines the width in pixels of the line that will be drawn to represent each active stack on the isopleth plots. Plot Parameter - Tip Thickness Integer range: 1 to 50 This values defines the width in pixels of the line that will be drawn to represent the each active tip on the isopleth plots. Plot Parameter - Shield Thickness Integer range: 1 to 50 This values defines the width in pixels of the line that will be drawn to represent the shield sections on the isopleth plots. Plot Colour - Grid Colour Colour dialog This shows the colour that will be used for the background of the isopleth plots. The colour may be selected by double-clicking the sample panel to display the Flaresim colour dialog. Figure 12-13, Colour Dialog
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Isopleth Customise View
Colours are selected in the dialog by clicking on the colour required and then clicking the Ok button. To close the dialog without changing the colour click the Cancel button. Plot Details - Flame Colour Colour dialog This shows the colour that will be used to draw the line representing the flame shape on the isopleth plots. The colour may be selected by double-clicking the sample panel to display the Flaresim colour dialog. Plot Details - Stack Colour Colour dialog This shows the colour that will be used to draw the line representing the flare stacks on the isopleth plots. The colour may be selected by double-clicking the sample panel to display the Flaresim colour dialog. Plot Details - Tip Colour Colour dialog This shows the colour that will be used to draw the line representing the flame shape on the isopleth plots. The colour may be selected by double-clicking the sample panel to display the Flaresim colour dialog. Plot Details - Colour Colour dialog This shows the colour that will be used to draw the line representing the shield sections on the isopleth plots. The colour may be selected by double-clicking the sample panel to display the Flaresim colour dialog.
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12.3.2 Contour Details Tab On the Contour Details tab, see below, it is possible to select the following options for the 10 contour lines that are available for each isopleth. Figure 12-14, Contour Details
Contour Details - Value Number This column defines the value for the selected isopleth contour in the units defined at the head of the column. Contour Details - Display Check box This column specifies whether the selected isopleth contour will be displayed. Set the check box to display the contour, clear it to hide the contour. Contours Contour Details - Colour Colour dialog This column defines the colour to be used for the selected isopleth contour. Double click the sample panel to open the Flaresim colour dialog to change the colour.
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Isopleth Customise View
Contour Details - Width Number This column defines the line width used to draw the selected isopleth contour. Contour Details - Value Drop down list: Solid / Dash / Dot / DashDot / DashDotDot This column selects the line style used to draw the selected isopleth contour.
12.3.3 Text Details Tab The Text Details tab, see below, allows the following settings to be defined. Figure 12-15, Isopleth Text Details
Text Options - Select Text Item Select Row The rows of this table describe the different text elements that can appear on an isopleth plot. The display properties of each different text element can be set by selecting the row and then using the fields below to modify the properties.
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Not all of the defined properties may be supported for all of the text elements. Where a property cannot be set it will be greyed out while that text element is selected. Text Options - Display Item Check box This controls whether the selected text element will be displayed. Set the check box to display the item, clear it to hide it. Text Options - Sample Font dialog The Sample column displays a sample of the font style that is currently defined for the selected text item. Double clicking the sample text opens a standard windows font dialog to allow the family, size and style of the font to be set for the selected text item. Figure 12-16, Font Dialog
Text Options - Spacing Integer range: 1 to 20 This determines the spacing between the selected text element and the item it describes e.g the spacing between the X-Axis of the isopleth plot and the X-Axis of the graph. The value is expressed as a percentage of the dimensions of the isopleth plot.
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Isopleth Customise View
KO Drums
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13 KO Drums Page 13.1 KO Drum View . . . . . . . . . . . . . . . . . . . . . . . 4 13.1.1 13.1.2 13.1.3 13.1.4 13.1.5 13.1.6
Common Fields . . . . . . . . . . . . . . . . . . . . . . 4 KO Drum View - Fluid Data Tab. . . . . . . . . . 5 KO Drum View - Fluid Composition Tab . . 8 KO Drum View - Vessel Data Tab . . . . . . . 10 KO Drum View - Nozzle Data Tab . . . . . . . 15 KO Drum View - Results Tab . . . . . . . . . . . 17
13.2 KO Drum Summary View . . . . . . . . . . . . . .23
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The KO Drum object allows modelling of vessels used to remove liquid from flare gas streams (KO Drums) in either Sizing or Rating mode for horizontal or vertical vessels. The KO Drum calculations consider the relationship between the size of the vessel, the size of liquid droplet that will be removed and the time taken for the vessel to fill with liquid during a flare event. A Flaresim model may contain multiple KO Drum objects allowing the comparison of different vessels. KO Drum objects may be created selecting the KO Drum menu option in the Add Items drop down menu or by selecting the KO Drum branch in the Case Navigator and clicking the Add button. An existing KO Drum object may be viewed by selecting it in the View drop down menu option; by double clicking it in the Case Navigator or by selecting it in the Case Navigator and clicking the View button. All defined KO Drum objects will be included in the calculations unless they have been set to Ignored. A KO Drum may be set to ignored by selecting it in the Case Navigator and clicking the Ignore button. An Ignored KO Drum object can be restored to the calculations by selecting it in the Case Navigator and clicking the Activate button. Alternatively a KO Drum object can be ignored and restored by setting or clearing the Ignored check box on its view. KO Drum calculations can be carried out independently of the main model through use of the Calculate button located on the KO Drum view. A KO Drum object can be deleted either by clicking the Delete button on its view or by selecting it in the Case Navigator and clicking the Case Navigator Delete button. A KO Drum Summary view showing the main details of all of the KO Drum objects in a case can be displayed by double-clicking the KO Drum collection branch in the Case Navigator or by selecting the KO Drum collection branch and clicking the Case Navigator View button. 13-3
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KO Drum View
13.1 KO Drum View The following figure shows the KO Drum view for entering and updating KO Drum data. Figure 13-1, KO Drum View
13.1.1 Common Fields Name Text Enter a name to identify this KO drum object. The entry will be automatically processed to remove any characters that are not allowed in file names.
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Ignored Check box Clear to include this stack in the calculations or set to ignore this stack when calculating. The effect of setting this check box will be to exclude the KO drum from the calculations. Status Text Status message The message displayed in this field and its colour indicates whether the data for this KO drum object is complete and ready for calculation.
13.1.2 KO Drum View - Fluid Data Tab The Fluid Data tab of the Stack View is shown in Figure 13-1 above. The options on this view are. Gas Flow - Mass Flow Range: 0 to 10,000 kg/s Defines the mass flow rate of gas entering the vessel. If the gas density is known, the Actual Volume Flow of the gas will be calculated. Gas Flow - Actual Volume Flow Range: 0 to 10,000 m3/s Defines the volume flow rate of gas entering the vessel at the vessel conditions. If the gas density is known, the Mass Flow of the gas will be calculated. Liquid Flow - Mass Flow Range: 0 to 10,000 kg/s Defines the mass flow rate of liquid entering the vessel. This is assumed to be a single phase liquid. The KO Drum does not attempt to distinguish between hydrocarbon liquid and water. If the liquid density is known, the Actual Volume Flow of the liquid will be calculated. 13-5
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KO Drum View
Liquid Flow - Actual Volume Flow Range: 0 to 10,000 m3/s Defines the volume flow rate of liquid entering the vessel at the vessel conditions. This is assumed to be a single phase liquid. If the liquid density is known, the Mass Flow of the liquid will be calculated. Pump Out Flow - Mass Flow Range: 0 to 10,000 kg/s Defines the mass flow rate at which liquid is pumped out of the vessel during a flaring event. This is assumed to be a single phase liquid. If the liquid density is known, the Actual Volume Flow of the Pump Out flow be calculated. Pump Out Flow - Actual Volume Flow Range: 0 to 10,000 m3/s Defines the volume flow rate at which liquid is pumped out of the vessel during a flaring event. This is assumed to be a single phase liquid. If the liquid density is known, the Mass Flow of the Pump Out flow will be calculated. Pump Out Flow - Include Pump Out Flow Drop down list: Yes/No When set to Yes the KO Drum calculations will assume that liquid is removed out from the vessel at the specified pump out flow during the flaring event. This reduces the size of vessel needed to achieve a particular hold up time. The default value for this setting is No meaning that no credit for the pump out flow is included.
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Fluid Properties - Property Source Drop down list: User Specified / REFPROP When set to User Specified the physical property data for the gas and liquid must be defined by the user. Fields for entering the gas density, gas viscosity and liquid density will be displayed as follows. Fluid Properties - Gas Density Range: 0 to 1000 kg/m3 The density of the gas phase in the vessel. Fluid Properties - Gas Viscosity Range: 0 to 1000 cP The viscosity of the gas phase in the vessel. Fluid Properties - Liquid Density Range: 0 to 2000 kg/m3 The density of the liquid phase in the vessel. When the Property Source is set to REFPROP the gas and liquid properties will be calculated. Fields for defining the temperature and pressure of the fluid and the calculated fluid properties will be displayed. The composition of the fluid must also be defined on the Fluid Composition tab. Fluid Properties - Temperature Range: 10 to 1000 K The temperature to be used for fluid property calculations. Fluid Properties - Pressure Range: 100 to 2.0e Pa The pressure to be used for fluid property calculations. Calculated Properties - Vapour Fraction Calculated value The vapour fraction calculated by flashing the specified fluid composition at the specified temperature and pressure. Calculated Properties - Gas Density Calculated value The gas density calculated after flashing the specified fluid composition at the specified temperature and pressure. 13-7
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KO Drum View
Calculated Properties - Gas Viscosity Calculated value The gas viscosity calculated after flashing the specified fluid composition at the specified temperature and pressure. Calculated Properties - Liquid Density Calculated value The liquid density calculated after flashing the specified fluid composition at the specified temperature and pressure. Calculate Button Clicking this button runs the calculations for an individual KO Drum independently of the main calculations.
13.1.3 KO Drum View - Fluid Composition Tab The Fluid Composition tab of the KO Drum View is shown below. Figure 13-2, KO Drum View - Fluid Composition Tab
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Table - Component Name Selected components Shows the list of components selected for use in the model. Components are added to the list by clicking the Add Component button to open the Component List view; see Figure 13-3. Highlight one or more components in the list that you wish to add and click the OK button. The required components will be added to the component list and the Component List view will close. Components are removed from the list by clicking the Remove Component button to open the Component List view; see Figure 133. Then select one or more components that you wish to remove and click the OK button. The selected components will be removed from the current component list and the Component List view will close. Figure 13-3, Component List view
Table - Composition Values Range: 0 to 1.0 Specifies the fraction of each component in fluid on either a mole or a mass basis as determined by the radio button selection to the right of the table.
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KO Drum View
Composition Basis Radio button: Mass/Mole This radio button selects the basis for the composition data. Note that changing it does not convert any existing component fraction data to the new basis. As component fractions are updated, the running total of the fractions is updated. A composition can be completed by clicking either the Normalise button to set remaining fractions to 0.0 and normalise current totals to add to 1.0 or by clicking the Calculate Last Fraction button to set a single unspecified component fraction to the value required to make the overall fraction equal to 1.0. Flash Options - Flash Method Drop down list: PR / NIST This option selects the method to be used when flashing the specified composition at the specified temperature and pressure. The default PR or Peng Robinson method is widely used and is the default option. The NIST option is the default method provided by the REFPROP package. The PR method is significantly faster than the NIST method.
13.1.4 KO Drum View - Vessel Data Tab The Vessel Data tab of the KO Drum View is shown in Figure 13-4. Calculation Options - Calculation Type Drop down list: Sizing / Rating This selects the type of calculation to be run. In Sizing mode the liquid holdup time and critical droplet size must be specified and the calculations will determine a vessel diameter, length and L/D ratio to meet these criteria. In Rating mode the vessel dimensions are specified and the holdup time and critical droplet diameter are calculated.
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Figure 13-4, KO Drum View - Vessel Data Tab
Calculation Options - Vessel Type Drop down list: Horizontal / Vertical This option selects the vessel type. Calculation Options - Vessel End Type Drop down list: Ellipsoidal / Hemispherical / Flat This option selects the vessel end type. Calculations include the volume of the ends for Horizontal vessels though not for Vertical vessels. Calculation Options - Settling Velocity Method Drop down list: API / GPSA This option selects the method to be used for calculating the settling velocity of a liquid droplet of known diameter. The API method is based on a curve fit to the settling velocity curve data published in API 521. The GPSA method is based on equations 13-11
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KO Drum View
published in the GPSA Data book which vary depending on the droplet Reynolds number (Re). Stoke’s law is used at low values of Re, Newton’s law at high values of Re and a third equation is used in the transition zone. The vessel input data and summary results sections of the view depend on the Calculation Type selected. For Sizing Calculations Vessel Input Data - Initial Liquid Level Range: 0 to 100% This entry defines the initial level of liquid in the vessel at the start of a flaring event. It is sometimes called the Sump level. For a vertical vessel the level is a percentage of the tan tan length. Vessel Input Data - Max. Allowed Liquid Level Range: 0 to 100% This entry defines the maximum liquid level that is allowed in the vessel during normal operation. For a vertical vessel the level is a percentage of the tan tan length. Vessel Input Data - Liquid Holdup Time Range: 0 to 100,000s This entry defines the liquid holdup time required. This is defined as the time taken for the vessel to fill from the initial liquid level to the maximum allowed liquid level at the specified liquid flow rate. The default value is 30 minutes as recommended in API 521. Vessel Input Data - Droplet Diameter Range: 0 to 100mm This entry defines the minimum diameter of liquid droplets that are to be removed from the gas in the KO Drum. The default value of 0.300mm is recommended in API 521. In a Horizontal vessel droplets will be removed from the gas if the droplet has sufficient time to fall to the liquid surface during the time taken for the gas to flow from the inlet nozzle to the exit nozzle. In
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a Vertical vessel droplets will be removed from the gas if the droplet settling velocity is greater than the superficial gas velocity. Vessel Input Data - L/D Ratio Range: 0.2 to 50 This entry defines the ratio of length / diameter to be used when sizing the vessel. If this value is specified the diameter specification is cleared automatically. Vessel Input Data - Diameter Range: 0.2 to 50 This entry defines the ratio of length / diameter to be used when sizing the vessel. If this value is specified the L/D specification is cleared automatically. This value cannot be specified for a Vertical vessel. For a Horizontal vessel a range of possible sizes can be found to meet a given liquid holdup time and droplet diameter. Thus a specification of either L/D Ratio or Diameter is required to generate a unique solution. For a Vertical vessel the minimum diameter is calculated directly from the settling velocity and the length will then be derived from the L/D ratio with the diameter being increased if it is required to meet the liquid holdup time criteria. Summary Results - Diameter Calculated value The calculated vessel diameter. Summary Results - Tan Tan Length Calculated value The calculated vessel tan to tan length of the vessel. The tan tan length for a Horizontal vessel will be determined either by the minimum gas flow path or minimum volume requirement as required. Summary Results - L/D Ratio Calculated value The calculated ratio of vessel length / vessel diameter.
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KO Drum View
For Rating Calculations Vessel Input Data - Initial Liquid Level Range: 0 to 100% This entry defines the initial level of liquid in the vessel at the start of a flaring event. It is sometimes called the Sump level. For a vertical vessel the level is a percentage of the tan tan length. Vessel Input Data - Max. Allowed Liquid Level Range: 0 to 100% This entry defines the maximum liquid level that is allowed in the vessel during normal operation. For a vertical vessel the level is a percentage of the tan tan length. Vessel Input Data - Tan Tan Length Range: 0 to 100m This entry defines the tan tan length of the vessel being rated. Vessel Input Data - Diameter Range: 0 to 20m This entry defines the diameter of the vessel being rated. Vessel Input Data - Liquid Level Range: 0 to 100% This entry defines the liquid level at which the rating calculation is to be done. If this value is specified the Liquid Holdup time is cleared automatically. For a vertical vessel the level is a percentage of the tan tan length. Vessel Input Data - Liquid Holdup Time Range: 0 to 100,000s This entry defines the liquid holdup time for which the rating calculation is required. Summary Results - Droplet Diameter Calculated value This is the minimum size of droplet that will be separated for a vessel of the specified size operating at the specified liquid level or at the specified holdup time.
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Summary Results - Liquid Holdup Time Calculated value The calculated liquid hold up time for the specified vessel operating at the specified liquid level. Summary Results - Liquid Level Calculated value The calculated liquid level that will be reached in the specified vessel after the specified liquid holdup time. Calculate Button Clicking this button runs the calculations for an individual KO Drum independently of the main calculations.For a vertical vessel the level is a percentage of the tan tan length.
13.1.5 KO Drum View - Nozzle Data Tab The Nozzle Data tab of the KO Drum view is shown below. It allows definition and calculation of inlet and outlet nozzle diameters and velocities. Figure 13-5, KO Drum View, Nozzle Data Tab
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KO Drum View
The view contains two similar sections, one for the inlet nozzle and one for the exit nozzle. Nozzle Data - Use Nominal Diameters Drop down list: Yes / No When set to Yes, the nozzle calculations will be based on nominal diameters. If the design velocity is specified the required nozzle internal diameter will be calculated and then the specified schedule searched for the next nominal size with a larger internal diameter. If the Nominal diameter is specified the nozzle internal diameter will be obtained from the specified schedule. When set to No, all calculations will use the internal diameter and the nominal diameter will not be set. Nozzle Data - Design Velocity Range: 0.1 to 500 m/s This specifies the design velocity for the nozzle. As long as the flow and fluid properties are known, specification of this value will do a sizing calculation and update the nozzle internal or nominal diameter as appropriate. This value will be cleared when the nominal diameter or internal diameter is specified. Nozzle Data - Schedule Drop down list: Available pipe schedules This entry defines the pipe schedule to be used for determining the nozzle internal diameter from the nominal diameter. The data for the available pipe schedules is defined in the Pipe Schedules data file specified in the Preferences view - the default is PipeSizes.xml. Nozzle Data - Nominal Diameter Drop down list: Available nominal diameters for selected schedule This entry defines the nominal diameter of the nozzle. It is only available for use when the Use Nominal Diameters option is set to Yes; otherwise this entry will be set to . The actual internal diameter will be obtained by looking up the specified nominal diameter defined for the selected schedule in the Pipe Schedules data file. 13-16
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When a sizing calculation is performed and the specified schedule does not have a nominal diameter with an internal diameter that exceeds the required size then the Nominal Diameter, Internal Diameter and Calculated Velocity entries will be blank. Nozzle Data - Internal Diameter Range: 1 to 5000.0 mm This entry specifies the internal diameter of the nozzle. It is only available for use when the Use Nominal Diameters option is set to No. Otherwise it displays the internal diameter for the selected nominal diameter and schedule obtained from the Pipe Schedules data file. Nozzle Data - Calculated Velocity Calculated value This entry displays the calculated velocity through the nozzle.
13.1.6 KO Drum View - Results Tab The Results tab of the KO Drum view displays the vessel dimensions, operating conditions and separation performance calculated for the vessel, see Figure 13-6. Vessel Dimensions - Tan Tan Length Calculated value This displays the length of the vessel calculated in a sizing calculation or specified for a rating calculation. Vessel Dimensions - Diameter Calculated value This displays the diameter of the vessel calculated in a sizing calculation or specified for a rating calculation. Vessel Dimensions - L/D Ratio Calculated value This displays the length / diameter ratio of the vessel.
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Figure 13-6, KO Drum View, Results Tab
Vessel Dimensions - Vessel Volume Calculated value This displays the vessel volume. Vessel Dimensions - Inlet Nozzle Diameter Calculated value This displays the diameter of the inlet nozzle. Vessel Dimensions - Outlet Nozzle Diameter Calculated value This displays the diameter of the outlet nozzle.
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Operating Results - Capacity Ok Calculated value This Yes/No result indicates whether the vessel has sufficient capacity to meet the required holdup time without exceeding the specified maximum allowed liquid level. Operating Results - Liquid Holdup Time Calculated value This displays the required holdup time if this has been specified or the calculated holdup time in rating calculations when the liquid level is specified. Operating Results - Additional Holdup Time Calculated value In rating calculations this displays the additional holdup time over and above the required holdup time. Operating Results - Liquid Level Calculated value This displays the calculated liquid level at the required holdup time. For a vertical vessel the level is a percentage of the tan tan length. When running sizing calculations if this value equals the maximum allowed liquid level it indicates that the vessel size is determined by capacity. When running rating calculations a value greater than the maximum allowed liquid level may be displayed. Results will never exceed 100%. Operating Results - Total Liquid Volume Calculated value This displays the total volume of liquid in the vessel at the indicated liquid level. For a vertical vessel this includes the volume of a single dished end. Operating Results - Holdup Liquid Volume Calculated value This displays the volume of liquid accumulated during the holdup time or when the specified liquid level is reached. This is calculated from the input liquid rate less any pumpout liquid rate.
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Operating Results - Slops Liquid Volume Calculated value This displays the volume of liquid in the vessel at the start of a flaring event when the vessel is assumed to have been drained to the specified initial liquid level. For a vertical vessel this includes the volume of a single dished end. Operating Results - Pump Out Liquid Volume Calculated value This displays the volume of liquid removed by the pumpout flow during a flaring event over the specified holdup time or during the time taken to reach as specified liquid level. Operating Results - Total X Section Area Calculated value This displays the total cross sectional area of the vessel. Operating Results - Liquid X Section Area Calculated value This displays the cross sectional area of the vessel occupied by the liquid phase. Operating Results - Gas X Section Area Calculated value This displays the cross sectional area of the vessel occupied by the gas phase. Operating Results - Inlet Nozzle Velocity Calculated value This displays the calculated velocity in the inlet nozzle. Operating Results - Outlet Nozzle Velocity Calculated value This displays the calculated velocity in the outlet nozzle. Separation Results - Droplet Diameter Calculated value For sizing calculations this displays the specified minimum droplet diameter that must be separated by the vessel. Other results for Min. Gas Flow Path and Settling velocity are derived from this value. 13-20
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For rating calculations the droplet diameter displayed is the minimum droplet size that can be separated in the vessel. Separation Results - Actual Gas Flow Path Calculated value This result is displayed for horizontal vessels only. It is the actual gas flow path calculated as the vessel tan tan length - 1.5 time the sum of the inlet and outlet nozzle diameters. Separation Results - Min Gas Flow Path Calculated value This value is only displayed for sizing calculations for a horizontal vessel. It is the minimum flow path required to allow the liquid droplet to settle to the liquid surface. If this value equals the actual gas flow path it indicates that the vessel size is determined by the minimum droplet size specification. Separation Results - Gas Superficial Velocity Calculated value This entry displays the superficial velocity of the gas in the vessel. For a horizontal vessel this value is used with the settling time to determine the minimum gas flow path required. For a vertical vessel this value must be less than the droplet settling velocity. In sizing mode for a vertical vessel if this value is equal to the settling velocity it indicates that the vessel size is determined by the minimum droplet size specification. Separation Results - Settling Height Calculated value This entry is displayed only for horizontal vessels. It is the height through which the droplet must settle from its entry assumed to be at the top of the vessel to the surface of the liquid. Separation Results - Settling Velocity Calculated value This entry displays the settling velocity for the indicated droplet diameter.
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In a horizontal vessel this value is used together with the settling height to determine the settling time. For a vertical vessel this value must be greater than the gas superficial velocity. In sizing mode for a vertical vessel if this value is equal to the gas superficial velocity it indicates that the vessel size is determined by the minimum droplet size specification. Separation Results - Settling Time Calculated value This entry is displayed only for horizontal vessels. It is calculated from the settling height and settling velocity of the droplet. Once the settling time is known the minimum gas flow path can be calculated from the gas superficial velocity.
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13.2 KO Drum Summary View The KO Drum Summary view is shown below. It may be opened by selecting KO Drum collection branch in the Case Navigator view and clicking the View button or by double-clicking the KO Drum collection branch. Figure 13-7, KO Drum Summary View
The KO Drum Summary view shows the input data and results for all of the KO drums in the case. Data input values can be updated through the summary view if required. Export Table Button Clicking this button opens a File Save dialog to allow the KO Drum summary table to be saved as a comma separated value (CSV) file, an Excel format file (XLS) or tab separated text file(TXT).
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Case Studies
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14 Case Studies Page 14.1 Case Study View. . . . . . . . . . . . . . . . . . . . . . 4 14.1.1 14.1.2 14.1.3 14.1.4 14.1.5 14.1.6 14.1.7 14.1.8
Common Fields . . . . . . . . . . . . . . . . . . . . . . 4 Case Study View - Input Variables Tab. . . . 5 Input Variables Tab - Discrete Variable . . . 6 Input Variables Tab - Incremental Variable 8 Case Study View - Result Variable Tab . . 10 Case Study View, Results Tab. . . . . . . . . . .11 Case Study View - Plots Tab . . . . . . . . . . . 13 Case Study View - Descriptions Tab . . . . 16
14.2 Select Variable View. . . . . . . . . . . . . . . . . . 18
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The Case Study object allows a set of comparison calculations to be defined and run automatically within a single Flaresim model. A Case Study is defined by selecting a set of input variables and specifying the values to be used for each selected variable in each case to be studied. Either discrete values are specified or, if appropriate, incremental values. A set of result variables which are to be recorded and compared are also selected. When the Flaresim model is calculated, each set of input values defined in the Case Study will be applied to the base model, the results will be recalculated and the specified result values will be saved. Following completion of the run the input and result values for each case can be viewed as either a table or a plot. Case Study objects may be created using the Add-Case Study drop down menu option or by selecting the Case Study branch in the Case Navigator view and clicking the Add button. An existing Case Study object may be viewed by double clicking it in the Case Navigator view or by selecting it in the Case Navigator view and clicking the View button. All defined Case Study objects will be included in the calculations unless they have been set to Ignored. A Case Study may be set to ignored by selecting it in the Case Navigator view and clicking the Ignore button. An Ignored Case Study object can be restored to the calculations by selecting it in the Case Navigator view and clicking the Activate button. Alternatively a Case Study object can be ignored and restored by setting or clearing the check box on its view. A Case Study object can be deleted either by clicking the Delete button on its view or by selecting it in the Case Navigator view and clicking the Delete button on this view.
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Case Study View
14.1 Case Study View The following figure shows the Case Study view as it would appear for a newly created Case Study object. Figure 14-1, Case Study View, Input Variables
14.1.1 Common Fields Name Text Enter text to identify this Case Study object. Status Text Status message The message displayed in this field and its colour indicates whether the data for this Case Study object is complete and ready for calculation. Ignored Check box Clear to include this Case Study in the calculations or set to ignore this Case Study when calculating.
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14.1.2 Case Study View - Input Variables Tab The Input Variables tab for a Case Study view is shown above in Figure 14-1. It is used firstly to select the type of case study that is to be created. Two types are available. The first is a case study based on Discrete values where the input variables are selected and the values of each variable are defined for every case to be considered. Any type of input variable can be included in a Discrete study including: Numeric inputs such as “tip mass flow” Integer inputs such as the “number of flame elements” Selection variables such as “calculation method” Option variables such as “include solar radiation” The other type of case study is based on Incremental values where the input variables selected must be a numeric input. The input data for the variable then defines the range over which the values will be varied and the number or size of each incremental step that will be calculated. The layout of the Input Variables tab will change depending on the type of study selected. The following fields are common to both types of study. Study Type Radio buttons: Study Discrete Values / Study Incremental Values Selection of this option defines whether the Case Study is based on Discrete Variables or Incremental Variables. After selection of this option the lower half of the view changes to show an appropriate table to allow input of the data. Case Study Information - Number of Cases Calculated value This displays the number of cases that will be calculated when the Case Study runs. For Discrete case studies this is the number of cases that have been added. For Incremental case studies this value is calculated from the range of values to be considered and the step size. 14-5
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Case Study View
14.1.3 Input Variables Tab - Discrete Variable Study The input variables tab for new Case Study after setting the study type to a Discrete variable case study is shown in Figure 14-1 above. The input data for a Discrete variable case study has three parts: 1.
Select the variables
2.
Add cases and optionally name them
3.
Define the data values for each selected variable and case
This input does not have to be entered in any particular order. For example it is possible to define the cases before selecting variables or to define all of the variables, cases and data values for a study and then add new variables and cases later. Add Variable Button Clicking this button opens the Select Variable view which allows new variables to be added to the Discrete Variable selection grid. Usage of the Select Variable view is described in section14.2. Remove Variable Button Clicking this button removes the variable whose column is currently selected in the Discrete Variable Selection grid. Add Case Button Clicking this button adds a new case to the Case Study as a new row in the Discrete Variable Selection grid. The new case will be added after the existing cases. The new case will be given a default name and default data values for the new case will set from the previous row in the grid.
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Remove Case Button Clicking this button removes the case whose row is currently selected in the Discrete Variable Selection grid. Once the required cases and variables have been added to the Discrete Variable selection grid, the data values in the individual cells can be updated by simply clicking on a cell and entering a new value. Should you wish to edit a few characters of an existing value, a double click will allow modifications to the previous cell contents. Data values for numeric variables must be entered in the units listed in the column header. If you need to use a different set of units then use the Preferences view to select the appropriate unit set. If the data values are being entered for a “selection variable”, the cell will display the appropriate choices as a drop down list in the usual way. An example of a completed Discrete Variable selection grid is shown below Figure 14-2, Input Variables Tab - Discrete Variable Selection
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14.1.4 Input Variables Tab - Incremental Variable Study The input variables tab for a new Case Study after setting the study type to an Incremental Variable case study is shown in below. Figure 14-3, Case Study View, New Increment Study Input
The input data for a Incremental variable case study is entered in two steps which must be carried out in order: 1. Select the variable 2.
Complete the variable information (min, max etc) in the Incremental Variable Selection grid.
Add Variable Button Clicking this button opens the Select Variable view which allows new variables to be added to the Incremental Variable selection grid. Usage of the Select Variable view is described in section 14.2. Only numerical variables may be selected for inclusion in an incremental variables study.
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Remove Variable Button Clicking this button removes the variable whose column is currently selected in the Incremental Variable Selection grid. Incremental Variable Selection - Active Drop down list: Yes/No This cell defines whether the selected variable is to be included when the case study is calculated. A maximum of 2 incremental variables can be active in a single run of the case study. Incremental Variable Selection - Minimum Value Range: As appropriate for variable This cell defines the minimum value for the selected variable. Incremental variable studies run for a range of values from a minimum to a maximum value. Incremental Variable Selection - Maximum Value Range: As appropriate for variable This cell defines the maximum value for the selected variable. Incremental variable studies run for a range of values from a minimum to a maximum value. Incremental Variable Selection - Number of Points Number This cell how many cases are to be generated over the range from the minimum value to maximum value. The step size cell is automatically updated when the number of points is changed. Incremental Variable Selection - Step Size Range: As appropriate for variable This cell defines the value of the step size to be used when generated cases over the range from the minimum to the maximum value. The number of points is automatically updated when the step size is changed. If the specified step size leads to a non-integer number of points an error message is displayed. All values for the Minimum, Maximum and Step Size entries must be defined in the default units for the variable displayed in the
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Case Study View
column header. If you need to enter values in different units they can be changed in Preferences view. As the values for Active, Minimum Value, Maximum Value and Number of Points/Step Size are updated, the total number of cases that will be generated is updated at the top right corner of the view. When two variables are set active (the maximum) then total number of cases is the product of the number of points defined for the two variables. E.g. if variable 1 defines 10 points over its range and variable 2 15 points then the total number of cases to be calculated will be 150. An example of a completed Incremental Variable Selection Grid is shown below. Figure 14-4, Input Variables Tab - Discrete Variable Selection
14.1.5 Case Study View - Result Variable Tab The Result Variable tab of the Case Study view is used to select the results variables whose values will be recorded as each case is run. It is shown below in. Its usage is similar to the input variable selection.
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Add Variable Button Clicking this button opens the Select Variable view which allows new variables to be added to the Result Variable selection grid. Usage of the Select Variable view is described in section 14.2. Only calculated variables may be selected. Remove Variable Button Clicking this button removes the variable whose column is currently selected in the Result Variable Selection grid. Figure 14-5, Case Study View, Result Variable Selection
14.1.6 Case Study View, Results Tab The Results tab of the Case Study view shows the results of the case study calculations. The results are displayed as a table with both the input values and result values displayed side by side. For a Discrete Variable study the cases are labelled with either the initial automatic case label or the user supplied label if this has been defined. Double clicking a case label will allow the input values for that case to be copied to the underlying base case. A confirmation
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Case Study View
window will pop up to ask you to confirm this action. When the variables values are copied, the information on the Active Case Study tab of the Case Summary view will be updated at the same time with the selected case name and description. Logging informations showing when the update was done will also be recorded. An Incremental Variable study will always label the cases in sequence. There is no option to transfer input values to the underlying base case for this type of case study. Export Button Clicking this button opens a File Save dialogue to allow the case study results table to be saved as an Excel (XLS), comma separated value (CSV) or text (TXT) file. A sample results tab view for a Discrete Variable study is shown below. Figure 14-6, Case Study View, Results Tab
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14.1.7 Case Study View - Plots Tab The Plots Tab of the Case Study view allows the case study results to be displayed as a plot. The details of plots tab vary with the type of case study but there is one common feature: Export Button Clicking this button displays a File Save dialog allowing the current plot to be saved as a JPG, PNG, BMP, WMF or EMF graphics file. For a Discrete Variable study, the plots generated are bar charts. Two grids are displayed allowing selection of the variables and cases to be plotted. Variables - Description Text cell The Variables grid displays names of all the variables in the case study, both input and result variables. Initially a default name is generated but these can be updated by clicking on the cell and entering a new value. Variables - Select Check box The Variables grid displays all the variables in the case study, both input and results variables. Selecting the check box against a variable indicates values that are to be included in the bar chart for each case. The number of variables that can be selected depends on their units; variables with up to two different unit types can be chosen. Cases - Description Text cell The Cases grid displays names of all the cases defined in the study. These are the same names defined in the Input Variables tab but they can be updated here by clicking on the cell and entering a new value.
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Case Study View
Cases - Select Check box The Cases grid displays all the cases defined in the case study. Selecting the check box against a case indicates that it is to be included in the bar chart. The number of cases that can be selected is unlimited though in practice the plot will be rather congested if more than 4-5 cases are selected. Horizontal Chart Check box Selecting this check box changes the plot from one with vertical bars to one with horizontal bars. This can assist in readability of the plot when longer case names are used. A sample plots tab for a Discrete Variable study is shown below. Figure 14-7, Case Study View, Discrete Study Plot
For an Incremental Variable study, the plots generated are line plots. Two grids are displayed allowing selection of the variables for the X and Y axes. Select X Variable - Description Text cell The Select X Variable grid displays names of all the variables in the case study, both input and result variables. Initially a default name is
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generated but these can be updated by clicking on the cell and entering a new value. Select X Variable - Select Check box The Select X Variable grid displays all the variables in the case study, both input and results variables. Selecting the check box against a variable indicate its values are to be used for the X axis of the plot. Only one variable can be selected for the X axis. Normally this will be an input variable but it is possible to select a result variable to allow a plot of one result variable against another. Result Variables - Description Text cell The Result Variables grid displays the names of all the result variables defined in the study. The default name displayed can be updated by clicking it and entering a new name. Result Variables - Select Check box The Result Variables grid displays all the result variables defined in the case study. Selecting the check box against a variable indicates that its results are to be included in the plot. Any number of variables can be selected as long as they all have the same unit type. When an Incremental study is run with 2 Active input variables a 3D plot using the data values from the input variables for the X and Y axes. One table is shown to select the result variable. 3D Plot Variables - Description Text cell The 3D Plot Variables grid displays the names of all the result variables defined in the study. The default name displayed can be updated by clicking it and entering a new name. 3D Plot Variables - Select Check box The 3D Plot Variables grid displays all the result variables defined in the case study. Selecting the check box against a variable
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indicates that its results are to be included in the plot. Only one variable can be selected. A sample Incremental Variable study plot is shown below. Figure 14-8, Case Study View, Incremental Study Plot
14.1.8 Case Study View - Descriptions Tab The Descriptions Tab of the Case Study view is used to provide descriptive information for individual cases. The descriptive information provided is used to update the Active Case description entry on the Active Case Study tab of the Case Summary view. This is to make it available for inclusion in reports. The description option is only available in Discrete Variable studies. Case - Description The Case grid displays names of all the cases defined in the study. These are the same names defined in the Input Variables tab but they can be updated here by clicking on the cell and entering a new value.
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Case - Select Check box The Cases grid displays all the cases defined in the case study. Selecting the check box against a case displays its descriptive text in the adjacent text box to allow it to be updated. A sample Description view is shown below. Figure 14-9, Case Study View, Descriptions Tab
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Select Variable View
14.2 Select Variable View The Select Variable view is displayed by the Case Study view to allow selection of input variables or result variables. The view is modal and must be closed before other Flaresim views can be used. When first displayed the Select Variable view will appear as shown below. Figure 14-10, Select Variable View, Opening
Selections are made in the Select Variable view in sequence 1. Select the type of object in the Object panel 2.
Select the name of the specific item of that type of object in the Name panel. Note if no items of that type exist in the model there will be no entries to chose from.
3.
Select the variable belonging to that specific item in the Variable panel. The variables displayed in the Variable panel will be appropriate to the type of variable being selected. For a Discrete variable selection, numeric, integer, selection and option input variables are displayed.
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For an Incremental variable selection, numeric input variables are displayed. For Result variable selection, numeric results variables are displayed. 4.
Click the Add or Ok button to add the variable to the case study.
Cancel Button Clicking this button closes the Select Variable view without adding a variable to the case study. Add Button Clicking this button adds the selected variable to the case study. If the variable has already been added an error message will be displayed. The Select Variable view will remain open to allow additional variables to be added. Ok Button Clicking this button adds the selected variable to the case study and then closes the Select Variable view. If the variable already exists in the case study no error will be displayed but it will not be duplicated. Sort A-Z Check box When selected the variables in the Variables panel will be displayed in alphabetical order. When this check box is cleared, which is the default setting, the variables will be displayed with the most commonly used variables at the top of the list.
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Select Variable View
A sample variable selection prior to clicking the Add or Ok button is shown below. Figure 14-11, Select Variable View, Variable Ready to Add
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15 Calculations Page 15.1 Calculation Sequence . . . . . . . . . . . . . . . . . 3 15.2 Calculation Options View . . . . . . . . . . . . . . 4 15.2.1 15.2.2 15.2.3 15.2.4 15.2.5
General Tab. . . . . . . . . . . . . . . . . . . . . . . . . . 4 Sizing Tab . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Heat Transfer Tab . . . . . . . . . . . . . . . . . . . . 12 Emissions Tab . . . . . . . . . . . . . . . . . . . . . . 15 Fitting Tab . . . . . . . . . . . . . . . . . . . . . . . . . . 17
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15.1 Calculation Sequence Calculate Buttons
Flaresim calculations are started by clicking the Calculate button in the Case View tool bar. Once started Flaresim will run through its calculation sequence for the active objects using the settings defined in the Calculation Options view. With the release of Flaresim 4 additional calculations to generate dynamics results and case study results are carried out in addition to the base case calculations. The detailed calculation sequence is: For a Standard Run • Dynamics calculations (cannot be run in sizing mode) • Case study calculations • Base case calculations For a Fitting Run • Fitting calculations • Base case calculations Each set of base case calculations runs through the following stages • Sizing calculations • Wind rose calculations • Sterile area calculations • Receptor point calculations • Receptor grid calculations • Knock out drum calculations • Dispersion calculations Each case study calculation runs through the following stages • Sizing calculations • Wind rose calculations • Sterile area calculations • Receptor point calculations • Receptor grid calculations - maximum radiation only • Knock out drum calculations The progress through the different calculation stages is reported in the Error/Warnings log panel. 15-3
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Calculation Options View
15.2 Calculation Options View The Calculation Options view shown below is accessed by selecting the Calculation Options branch in the Case Navigator view and clicking the View button. Alternatively you can double click the Calculation Options branch.. Figure 15-1, Calculation Options View
Status Text Status message The message displayed in this field and its colour indicates whether the calculation options are complete and the model is ready for calculation.
15.2.1 General Tab The following data entry fields are found on the General tab of the Calculation Options view (see Figure 15-1). 15-4
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Calculation Methods - Radiation Method Drop down list: Flaresim API / Strict API / Point / Diffuse / Mixed / Brzustowski / M.Point Brz / Chamberlain Selects the method to be used to model the thermal radiation from the flame. The Flaresim API and Strict API methods model the single point source method of Hajek and Ludwig given in API RP-521. The difference between the methods is in the method of calculating the flame shape before finding the centre point to act as the source. The Flaresim API method uses the vector based flame shape method and allows multiple flame elements to be used to model the shape more accurately even though a single, centre point will be used as the source. The Strict API method uses the graphical method presented in API 521 through a curve fit to the data presented there. The API method in DOS versions of Flaresim and Flaresim for Windows versions prior to version 2.0 was the Flaresim API method. Either API method may be generally applied to most flare systems. The Point source method is a multiple point extension of the API method in which the flame is assumed to be completely transparent such that radiation from one point does not either interfere with or occlude another. The flame is divided into a series of smaller point source elements whose contributions are summed to derive the total radiation from the flame. In practice this method generally gives more realistic and less conservative values than the API method. It does however tend to over predict thermal radiation in the near field. The Diffuse source method assumes that the flame is completely opaque such that radiation is emitted entirely from the surface of the flame envelope. This method tends to under predict the thermal radiation in the near field. The Mixed source method is an empirical combination of both the Point and Diffuse source methods. This has been found to give more realistic results in both the near and far fields. The Brzustowski method is a single point method in which the flame centre is determined from jet dispersion theory. The method as
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described in API RP-521 is subject to a number of limitations in its implementation in Flaresim:• Only vertical tips may be modelled. • Air assisted flares may not be modelled. • Liquid burners may not be modelled. The M.Point Brz method is a Flaresim extension to the standard Brzustowski method to allow the number of flame elements and the element position to be specified by the user. In versions of Flaresim prior to 1.2 these options could be set for the Brzustowski method. In Flaresim 1.2 the Brzustowski method is forced to be a single flame element with fixed element position. Old cases that specify the Brzustowski method will be updated automatically to M.Point Brz if they have more than one flame element or the element position is not 50%. The Chamberlain method, also known in the industry as the Shell Thornton method is based on a modelling the flame as a conical frustum radiating from its surface with a uniform emissive power. The method was developed to provide more accurate predictions of flame shape and radiation in the near field. Calculation Methods - No of Elements Range: 1 to 50 The number of elements that the flame is divided into for calculation of flame shape and the sources for the Point, Diffuse and Mixed methods. Larger values will generally give more realistic values for the thermal radiation at the expense of calculation time. Unless you are modelling a system with a highly distorted flame shape, 25 elements should be more than adequate. The combination of a high flaring rate and an inclined tip flaring into a high wind may require 50 elements to adequately model the flame shape. Calculation Methods - Element Position Range: 0 to 100% The element position indicates the source point within a flame element that is used for calculations. Typically this is 50% i.e. the
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middle of the flame element is taken to be the point source. 0% indicates the source is the start of the element, 100% is the end. Calculation Methods - Noise Method Drop down list: API/Spectrum Selects the method to be used for the noise calculations. The API method taken from RP521 is a simple single value method and considers jet noise only. The Spectrum method uses multiple frequency values and includes combustion noise. Generally the Spectrum method is recommended. Options - Expert Mode Check box When set this option allows the user to select additional options that have been classified as being for expert use only. These options include:1. Allowing the flame length method to be set independently of the calculation method for each Tip - See Tip view. 2.
Allowing the plane of orientation to be set for Receptor Points - See Receptor Point view.
3.
Allowing the plane of orientation to be set for Receptor Grids - See Receptor Grid view.
4.
Allowing the radiation from each tip to be modelled with a different radiation method.
5.
Allowing the emissions data for each Tip to be set separately.
6.
Allowing user specified F Factors to be corrected by internal correlations for use of HP/LP tips and Assist Fluids.
Options - Windchill Check box When set an empirical correlation is used to correct the incident thermal radiation at any receptor point by taking into account the heat losses due to passage of wind over the point. Use of this option
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will generally be a matter of individual judgement or your company standards. It is recommended that you do not use this option if you are interested in the surface temperature calculations. Note that effective of wind on convective heat transfer in the surface temperature calculations is independent of the setting of this option. Options - Atm. Noise Attenuation Check box When set a correction will be applied to the noise calculations to allow for the attenuation in noise due to atmospheric absorption. This option should normally be set on. Include Options - Jet Dispersion Check box Selecting this enables the jet dispersion calculations and will calculate concentrations of flare fluid at receptor points and for receptor grids under flame out conditions. Include Options - Gaussian Dispersion Check box Selecting this enables the calculations for all Gaussian Dispersion objects defined in the model. Include Options - Run Dynamics Check box Selecting this enables dynamics calculations to be run to evaluate the change in radiation and other results with time as the flare flow varies with time. The variation in flare flow with time must be defined on the Tip Dynamics View and the results variation with time can be viewed on the Receptor Point Dynamics View. The dynamics calculations are run in addition to the defined base case. Receptor Grid objects and Dispersion objects are not included in the dynamic calculations.
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Include Options - Run Case Studies Check box Selecting this enables the calculation of all the active Case Study objects. Case study calculations are run in addition to the defined base case. Buoyancy For all methods except the Brzustowski and Chamberlain methods, the flame shape is calculated by resolving the velocity vectors in three dimensions. The main components are the tip exit velocity and the wind velocity. There is however an additional velocity component which is due to the density differences between the hot combustion gases and the surrounding air. This is referred to as the flame buoyancy term. Buoyancy - Pipe Range: 0 to 30 m/s The flame buoyancy which should be used for Pipe flares. A value of 3.0 m/s is recommended unless specific vendor information suggests otherwise. Buoyancy - Sonic Range: 0 to 30 m/s The flame buoyancy to be used for Sonic flare tips. A value of 4.6 m/s is suggested unless specific vendor information suggests otherwise. Buoyancy - Welltest Range: 0 to 30 m/s The flame buoyancy to be used for Liquid flare tips. A value of 0.03 m/s is suggested unless specific vendor information suggests otherwise. The recommended buoyancy values are based on empirical information supplied by a flare vendor. The wide range of allowed values is intended to provide flexibility for users with specific information and the validity of any values entered is the responsibility of the user.
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Environment - Active Environment Drop down list: All defined environments Allows selection of the set of environmental data to be used for the calculations. This can also be set through activating a specific Environment object.
15.2.2 Sizing Tab The following figure shows the Sizing tab of the Calculation Options view. Figure 15-2, Sizing Tab
Stack Sizing - Select Stack Drop down list of defined stacks Allows one of the existing stacks to selected for sizing calculations i.e. calculation of the stack length to meet the sizing constraints defined on the active receptor points. To stop the sizing calculations i.e. to do a rating calculation this should be set to None.
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Stack Sizing - Minimum Length Range: 0 to 500 m The minimum length allowed for the stack being sized. Stack Sizing - Maximum Length Range: 0 to 500 m The maximum length allowed for the stack being sized. Sizing Result - Calculated Length Calculated value: m The calculated length of the stack required to meet the sizing constraints. If the sizing calculations fail the value will be blank. Sizing Result - Wind Speed Used Calculated value: m/s The wind speed used to calculate the final stack size. In a simple sizing case this is the wind speed defined for the active environment. If Wind Rose data has been considered in the sizing calculations, see Environment View, then this will be the wind speed in the wind rose data that resulted in the highest stack length. The wind speed used to calculate and display the final results will always be the wind speed specified in the active environment. Note wind speeds corrected for elevation used at the tip exit and at receptor points are reported on the Tip Views and Receptor Point Views. Sizing Result - Wind Direction Used Calculated value: angle The wind direction used to calculate the final stack size. In a simple sizing case this is the wind direction defined for the active environment. If Wind Rose data has been considered in the sizing calculations, see Environment View then this will be the wind direction in the wind rose data that resulted in the highest stack length. The wind direction used to calculate and display the final results will always be the wind direction specified in the active environment.
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Pressure Profile Options - Pressure Tolerance Range: 1.0e-6 to 10 Pa This value defines the convergence tolerance that is used in the pressure profile calculations for the tip and stack pressure drop. Prior to Flaresim version 4 this value was internally set to 0.01 Pa. The default in Flaresim version 4 is set to 0.1Pa to increase the speed of calculations when using Refprop calculated properties since these are significantly slower than the simple correlations used in earlier versions. Testing has shown that in general results show no significant changes but some differences might be seen when tip and stack pressure drops are low. Pressure Profile Options - Tip Elements Range: 2 to 100 This defines the number of elements that the tip length is divided into for the pressure drop calculation. Prior to Flaresim version 4 this value was set internally to 10. Since the calculation speed when using Refprop calculated properties is significantly slower in Flaresim 4 this has been reduced to a default value of 4. Testing has shown this does not have a significant effect on the overall pressure drop. Pressure Profile Options - Riser Elements Range: 2 to 100 This defines the number of elements that the stack riser length is divided into for the pressure drop calculation. Prior to Flaresim version 4 this value was set internally to 1000. Since the calculation speed when using Refprop calculated properties is significantly slower in Flaresim 4 this has been reduced to a default value of 40. Testing has shown this does not have a significant effect on the overall pressure drop.
15.2.3 Heat Transfer Tab The following figure shows the Heat Transfer tab of the Calculation Options view.
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Figure 15-3, Heat Transfer Tab
This view allows definition of coefficients for calculating the heat transfer coefficient as a function of wind speed. Two sets of parameters may be defined to apply above and below a limiting wind speed. The equation is:B
HTC = A ⋅ Windspeed + C
(1)
Wind Speed Units Drop down list: Speed Units This drop down selects the wind speed units that are appropriate for the A and C constants entered.
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Transition Wind Speed Range: 0.01 to 100 m/s The transition wind speed at which the heat transfer coefficient calculation switches from the first set of defined constants to the second. There are then two groups of equation parameters, the first apply for wind speeds below the defined transition wind speed, the second when the wind speed is higher than the transition value. Equation Parameter A Range: 0.01 to 100 The constant factor to be multiplied by the wind speed. Equation Parameter B Range: 0 to 10 The power to which the wind speed is raised. Equation Parameter C Range: 0.01 to 100 The constant factor to be added to the heat transfer coefficient. Dynamics Parameters - Exposure Time Range: 1 to 1,000,000 s The time over which the dynamics results and changes in surface temperatures are calculated. Dynamics Parameters - Time Steps Range: 1 to 1,000 The number of calculations to be made between the starting point and the final exposure time for dynamics calculations and the base case temperature rise. A higher number will track the change in results with time more accurately but at the cost of greater calculation time. The appropriate value will depend on the rate of change in results with time; the faster values are changing the greater need for additional time steps.
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15.2.4 Emissions Tab The Emission tab defines the default calculation basis and corresponding rate of emissions of NOx, CO and unburnt hydrocarbons to be used for all tip. These values will be used unless the Expert Mode option is in use in which case they can be set individually for each Tip on the Emissions Tab of the Tip View. Figure 15-4, Emissions Tab
NOx Emission Rate - Basis Drop down list: Mass/Heat Release / Mass/Mass Flare Fluid / Mass/ Mole Flare Fluid / Sintef Method This entry defines the basis used to calculate the NOx emission rate for each tip. The NOx emission can be set to a fixed proportion based on the heat release, mass flow or mole (volume) flow of the flared fluid or calculated using a method published by Sintef, see Methods chapter.
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Calculation Options View
NOx Emission Rate - Rate Range: 0 to 100, units depend on selected Basis This entry defines the fixed proportion used to calculate the total emissions of NOx according to the defined Basis. Leave blank if the Sintef calculation basis is selected. CO Emission Rate - Basis Drop down list: Mass/Heat Release / Mass/Mass Flare Fluid / Mass/ Mole Flare Fluid This entry defines the basis used to calculate the CO emission rate for each tip. The CO emission can be set to a fixed proportion based on the heat release, mass flow or mole (volume) flow of the flared fluid. CO Emission Rate - Rate Range: 0 to 100, units depend on selected Basis This entry defines the fixed proportion used to calculate the total emissions of CO according to the defined Basis. Unburnt HC Emission Rate - Basis Drop down list: Mass/Heat Release / Mass/Mass Flare Fluid / Mass/ Mole Flare Fluid This entry defines the basis used to calculate the emission rate of unburnt hydrocarbons for each tip. The unburnt HC emission can be set to a fixed proportion based on the heat release, mass flow or mole (volume) flow of the flared fluid. Note that unburnt hydrocarbons are assumed to be Methane. Unburnt HC Emission Rate - Rate Range: 0 to 100, units depend on selected Basis This entry defines the fixed proportion used to calculate the total emissions of unburnt according to the defined Basis. Reset Defaults Button Clicking this button will reset the Emission Bases and rates to their default values.
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Calculations
15-17
Dispersion Options - Averaging Time Drop down list: Short/Long The averaging time used in the Jet Dispersion calculations. Generally this should be set to Short for typical short duration flaring events. Dispersion Options - Stopping Concentration Range: 1.0e-5 to 1.0 The minimum concentration calculated by the Jet Dispersion calculations.
15.2.5 Fitting Tab The Fitting tab provides access to a data fitting process in Flaresim that allows the F Factor for a selected tip to be adjusted to achieve a best fit between the calculated and observed radiation levels at one or more receptor points. The data fields that control the fitting process are shown below. Figure 15-5, Fitting Tab
Fitting Parameters - Target Tip Drop down List This selects the Tip whose F Factor value is to be adjusted to try to match the calculated and observed values of radiation. The list 15-17
15-18
Calculation Options View
shows all of the tips configured in the model. The tip that is selected must have its F Factor method set to User Defined. It does not matter what starting value of F Factor is defined on the tip. Fitting Parameters - Target Receptor Point Drop down list: Available receptor points This selects the Receptor Points which are to be included in the fitting calculation. Either a single point can be selected or the “All Active” option can be selected in which case all Receptor points that are not set to Ignored will be included in the calculation. All of the points included in the calculation must have a value defined for the Observed Radiation field. Fitting Parameters - Result Calculated value This displays the value for the F Factor that was calculated by the fitting process. Fitting Parameters - Error Calculated value This displays the square root of the sum of the square of the relative errors between the calculated and observed radiation values for the selected Receptor points. Run Fitting Button Clicking this starts the fitting process. The fitting process first reconfigures the model to solve for Receptor points only. It will then set the selected Tip to a low F Factor and run the model to calculate the radiation at each selected Receptor point. The sum of the square of the relative errors between the calculated and observed radiation values will then be calculated. The F Factor is then raised by a step and the process repeated until the calculated error begins to rise. At this point a bisection search for the F Factor that gives the minimum value for the error is obtained. When the value of the F Factor that gives the minimum error has been found the whole model will be reinstated and re-run at the resulting F Factor. 15-18
Calculations
15-19
Note if the fitting process is run for a single Receptor Point the final error should always be 0 as long as there is a feasible value for the F Factor which cannot be greater than 1.
15-19
15-20
15-20
Calculation Options View
Printing
16-1
16 Printing Page 16.1 Report View . . . . . . . . . . . . . . . . . . . . . . . . . 4 16.1.1
Report File . . . . . . . . . . . . . . . . . . . . . . . . . . 7
16.2 Output Graphic Report View . . . . . . . . . . . .9 16.3 Select Graphic Report Printer. . . . . . . . . . 13 16.4 Graphic Report Page Settings . . . . . . . . . 14
16-1
16-2
16-2
Printing
16-3
Output of Flaresim results is through the tool bar Print and Graphic Report buttons or the File-Print and File-Print Graphic Report menu options. Selecting the Print option creates a Report view which contains a report of the current input data and results for the case. The Report view allows the contents to be customised by selecting different sections of data input and output. Multiple Report views can be created from the same case as data is changed and the case recalculated to allow for side by side comparison of results. Report views can then be output to a printer or saved as a case. Selection of the Graphic Reports option opens the Output Graphic Report view which offers selection of the graphic reports to be output and the output method to be used. These views are described below. Flaresim produces its standard reports through an HTML file which is created by using a style sheet file, by default Flaresim.xsl, to format the contents of the Flaresim model file. The Preferences view allows the user to specify the name of the style sheet file to be used. Both the Flaresim XML data files and the XSL style sheet file comply with the appropriate W3C.org standards. This provides the capability to reformat the output of Flaresim through definition of an alternate style sheet file. Third party documentation on the use of XSL files should be consulted since this is beyond the scope of this documentation. Flaresim’s graphic reports are produced through a layout file which is an XML formatted file that describes the text, data and graphical elements to be included in the report and their layout. The default layout file to be used may be selected in the Preferences view or for each receptor grid individually.
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Report View
16.1 Report View When the Print button on File-Print menu option is selected a Report view is opened. This requires that the case is saved to a temporary file and there can be a short delay before the report appears. Figure 16-1, Report View
The Report view is a separate window from the main Flaresim program allowing multiple Report views to be compared side by side as the case is recalculated with different input data. To aid identification of different Reports, the Report view title bar shows the time that the Report was generated and the name of the case that generated it. 16-4
Printing
16-5
Note that the Report view being displayed is of the HTML report file generated by Flaresim. Some elements of this report file will float and be reformatted to try and fit into the area available for display. It may be necessary to expand the view to see the report as it will be printed. Report Item Tree view This section of the view lists the items that can be included in a report as a tree structure in a similar way to the Case Navigator view. As in the case summary, the and icons can be used to expand and collapse branches of the tree as required. The complete Report Items panel can be collapsed using the button and expanded again using the button. Include Item Check box Each item available for the report has a check box against it. The check box should be set to include the topic or cleared to exclude it. Lines Per Page Range: 10 to 1000 The maximum number of lines of text for each report page. Reset Options Button Resets the include item check boxes for each item to the defaults contained in the PrintPreferences.xml file. Clear All Button Clears the include item check boxes for all items. Save Options Button Opens a File Save dialog to allow the current report item selection to be saved to a dedicated configuration file. This option can be used to update the default settings in the PrintPreferences.xml file.
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Report View
Read Options Button Opens a File Open dialog to allow a configuration file contain report item selection to be read and applied to the current case. Note that whenever a case is saved the current report settings are saved with it. The Save Options and Read Options buttons provide a way for settings copied from one case to another without the need to update the main PrintPreferences file. Save Report As Case Button Since the Report view is independent of a case and because multiple Reports can be generated with different input data, the Save Report As Case allows the information associated with a particular report to be saved as a Flaresim case. Note that all of the case data and results will be saved, not just the current selected items. Print Button Prints the report using the current selection of included and excluded items. Clicking this button starts the printing process by displaying the standard Windows Printer dialog view below to allow the user to select the printer to be used and to control the setup of the print options.
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Printing
16-7
Figure 16-2, Print Dialog
Once the printer options have been set the Print button on this view should be clicked to send the output to the printer. Page Setup Button This displays a standard windows page setup view to allow the page margins etc to be defined for the report. While these changes may have an impact on the number of lines of text that will fit on the page it is still necessary to update the Lines Per Page entry separately. Refresh Button Updates the report preview to reflect any changes that have been made to the included or excluded topics. The report cannot be refreshed if any data has changed since it was generated.
16.1.1 Report File When a case is saved, the HTML report file and the associated graphic files will be automatically saved at the same time. These files will be saved to a sub-folder in the folder to which the case is 16-7
16-8
Report View
being saved. The sub-folder name will be the same as the saved file name. This HTML file can be viewed at any time using an internet browser, independently of Flaresim.
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Printing
16-9
16.2 Output Graphic Report View When the button or File-Print Graphic Reports menu option is selected displays the Output Graphic Report view to allow selection of the graphic reports to be output and whether these are to be output to printer or to a file. The Output Graphic Report view is shown below. This is a modal view that does not allow use of other parts of the Flaresim program until it is closed. Figure 16-3, Output Graphic Report View
Select List box: Receptor Grids, Receptor Points, Dispersions This displays as list of the Receptor Grids, Receptor Points and Dispersion objects for which a graphic report is available. Receptor Points only appear in the list if a wind rose graphic report is available. Dispersion objects only appear in the list when a contour plot report is available.
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Output Graphic Report View
Objects are selected in the list by clicking on the name in the list. Multiple items may be selected using Shift-Click and Ctrl-Click in the usual way. For convenience an All option is provided at the top of the list which can be selected to output graphic reports for all the receptor grids and receptor points in the model. Select Plots Check boxes Each receptor grid can generate four separate graphic reports, one for each of the radiation, noise, temperature isopleths and concentrations (as long as jet dispersion calculations are enabled). These check boxes allow selection of which reports will be output. Set a check box to output the associated report and clear a check box to suppress the report. Save File Type Drop down list: JPG / PNG / BMP / WMF / EMF This allows selection of the graphic file type that will be generated if the reports are output to file using the Save Graphic Reports button. The options are JPG, PNG or BMP bitmap files and WMF or EMF vector meta files. Save Graphic Reports Button This creates the selected graphic reports and saves them as files of the type selected by the Save File Type item. A pop-up window will be displayed to select the output folder. Each file will be automatically named with the type of the isopleth and the name of the receptor grid e.g. Radiation-Helideck. Confirmation of each file saved is output to the information log. Isopleths To CSV Button This saves a list of the isopleth data points for each selected report to a text file in Comma Separated Value or CSV format. This allows the isopleths to be plotted using third party applications such as Excel. A pop-up window will be displayed to select the output
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Printing
16-11
folder. Confirmation of each file saved is output to the information log. Isopleths To XML Button This saves a list of the isopleth data points for each selected report to a text file in XML format. A pop-up window will be displayed to select the output folder. Confirmation of each file saved is output to the information log. Isopleths To DXF Script Button This creates and saves an Autocad script that will allow the isopleth data for each selected report to be imported into a plot plan or other drawing using Autocad or compatible software such as Intellicad. A pop-up window will be displayed to select the output folder. The files will be stored with a .scr extension in the selected folder. Confirmation of each file generated is output to the information log. The script generated will create one new layer in the target drawing file for each isopleth value defined. Each layer will be named according to the isopleth value and the isopleth value will also be displayed on a text label within the added layer. An additional layer will be created to draw the flame location. Note that the generated script requires that the “Snap to guides” features of Autocad are turned off before playing the script. Print Graphic Reports Button This button prints the selected graphic reports to the currently selected graphic report printer.
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Output Graphic Report View
Preview Graphic Reports Button This button generates a preview of the selected graphic reports and displays it in the Preview Graphic Reports view shown below. Figure 16-4, Preview Graphic Reports View
This view allows output pages to be reviewed and page settings adjusted. The Print button in the view can then be clicked to send the output to the printer or the Save button can be used to save the output to a PDF file. Close Button This button closes the Output Graphic Report view and returns to the main Flaresim views.
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Printing
16-13
16.3 Select Graphic Report Printer The Select Graphic Report Printer option on the File Menu can be used to select the printer that will be used for output of graphic reports. It opens a standard Printer Selection Dialog as shown below. Figure 16-5 Printer Selection Dialog
In addition to the printer, the paper size and orientation can also be selected through the Properties button of the view. The selection of graphic report printer will be remembered and reselected next time Flaresim is used if the appropriate option is set on the Files tab of the Preferences view.
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Graphic Report Page Settings
16.4 Graphic Report Page Settings The Graphic Report Page Settings menu option on the File Menu can be used to set the page size, orientation and margin for output of Graphic Reports. The view is shown below. Figure 16-6, Page Settings Dialog
The allowed paper sizes and paper source are those for the currently selected printer. The paper size, orientation and margins will be saved as Flaresim is closed and reloaded next time Flaresim is used. Graphic reports will override the default page size specified in the selected layout file if required to fit within the page size defined in this dialog.
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Calculation Methods
17-1
17 Calculation Methods Page 17.1 Thermal Radiation . . . . . . . . . . . . . . . . . . . . 4 17.1.1 17.1.2 17.1.3 17.1.4 17.1.5 17.1.6 17.1.7 17.1.8 17.1.9 17.1.10
API Method . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Integrated Point Source Method. . . . . . . . . 5 Integrated Diffuse Source Method . . . . . . . 6 Integrated Mixed Source Method . . . . . . . . 7 Brzustowski and Sommer Method . . . . . . . 7 Chamberlain Method (Thornton Method). . 8 F Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Atmospheric Attenuation . . . . . . . . . . . . . 10 Windchill . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Flame Shape . . . . . . . . . . . . . . . . . . . . . . . . 13
17.2 Surface Temperature . . . . . . . . . . . . . . . . .20 17.3 Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 17.3.1 17.3.2 17.3.3
Combustion Noise . . . . . . . . . . . . . . . . . . . 22 Jet Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Atmospheric Attenuation . . . . . . . . . . . . . 26
17.4 Purge Gas . . . . . . . . . . . . . . . . . . . . . . . . . . 28 17.4.1 17.4.2
HUSA Method . . . . . . . . . . . . . . . . . . . . . . . 28 Reduced HUSA Method . . . . . . . . . . . . . . . 29
17.5 Water Sprays . . . . . . . . . . . . . . . . . . . . . . . 31 17.5.1
Thickness of Water Curtain . . . . . . . . . . . 32
17-1
Calculation Methods
17-2
Page 17.6 Gas Dispersion. . . . . . . . . . . . . . . . . . . . . . 33 17.6.1 17.6.2 17.6.3
Jet Dispersion . . . . . . . . . . . . . . . . . . . . . . 33 Gaussian Dispersion . . . . . . . . . . . . . . . . . 33 Emission Rates . . . . . . . . . . . . . . . . . . . . . 35
17.7 Nomenclature . . . . . . . . . . . . . . . . . . . . . . . 36 17.7.1 17.7.2
Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Subscripts. . . . . . . . . . . . . . . . . . . . . . . . . . 37
17.8 References . . . . . . . . . . . . . . . . . . . . . . . . . 38
17-2
Calculation Methods
17-3
This chapter contains a summary of the mathematical models used for the calculation of incident thermal radiation, noise and surface temperatures. It is not intended to be a detailed treatise on combustion theory, but rather a summary of the models available in the program to assist the engineer in making his own judgement as to the applicability of the models to his particular system.
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17-4
Thermal Radiation
17.1 Thermal Radiation 6 options are available for calculating the incident thermal radiation at a point receptor. These are:• API Method • Integrated Point Source • Integrated Diffuse Source • Integrated Mixed Source • Brzustowski and Sommer • Chamberlain (Thornton) These methods primarily differ in the approach to the calculation of the contributions of individual elements within the flame to the total incident heat flux and the method for calculation of the flame shape. Each of these methods can be used for most applications either as preferred by the program user or as required by client preference and specifications. A key parameter in calculation of thermal radiation is the fraction of the combustion heat radiated by the flame, known as the F Factor. Flaresim includes a number of different correlations for predicting F Factor. Predicted thermal radiation values may be corrected for a range of environmental conditions. These corrections are available for: • Windchill • Atmospheric attenuation The inclusion of the attenuation effects due to windchill or atmospheric attenuation must be either a matter of sound engineering judgement or as required by client specifications. All thermal radiation values calculated by any of these methods are to point receptors and do not take account the relative orientation of the receptor to the flame.
17-4
Calculation Methods
17-5
17.1.1 API Method This is based upon the simple heat release method outlined in API RP-521, "Guide For Pressure Relieving and Depressuring Systems", 1997 [1]. This method uses Equation (1) proposed by Hajek and Ludwig [2] to evaluate the flux at a given distance from the flame.
FQ K = -------------2 4πD
(1)
It is assumed that the flame can be treated as a single point source located at the centre of the flame which radiates in all directions from this centre. There are two variants of the API method implemented in Flaresim. In the Flaresim API method the flame shape is calculated from the resolution of the velocity vectors for the flared fluid, wind and flame buoyancy. Multiple flame elements can be defined to model the flame shape more accurately but the source is still modelled as a single point at the centre. In the Strict API method, the flame shape is calculated using the graphical method described in the API RP521 implemented using a data fit to the curves presented in the guide.
17.1.2 Integrated Point Source Method. The integrated point source method is an extension to the API method in which the flame is divided into a series of smaller point source elements whose contributions are summed to derive the total thermal radiation from the flame. The centre of each of the elements is used for the calculation of the distance between the flame element and the target receptor. Two major assumptions are made: • The flame radiates uniformly along its entire length. • The flame is long in comparison to its width. As such it may be considered to be a line source. 17-5
17-6
Thermal Radiation
In making these assumptions, it is accepted that the flame itself is completely transparent to thermal radiation and that one point source does not either interfere with or occlude another. This occlusion effect would generally be negligible to the side of the flame but could be significant at locations directly below the flame where there is a shallower angle of view. These assumptions lead to Equation (2) proposed by McMurray[4].
FQ L 1 K ips = ---------- ------- dl 4πL 0 D 2
(2)
The distance between the point source and the receptor is calculated from a flame shape derived from the resolution of the velocity vectors for the flared fluid, wind and flame buoyancy.
17.1.3 Integrated Diffuse Source Method The diffuse source model assumes that the flame itself is completely opaque such that the thermal radiation is emitted entirely from the surface of the flame. This model is represented by Equation (3).
FQ L sin β -------- ----------- dl K ids = 2 2 π L 0 D
(3)
The distance between the point source and the receptor is calculated from a flame shape derived from the resolution of the velocity vectors for the flared fluid, wind and flame buoyancy.
17-6
Calculation Methods
17-7
17.1.4 Integrated Mixed Source Method The mixed source model is basically a combination of the point and diffuse source models. This was developed as a result of observations during field tests [4] that showed: • The Integrated Point Source (IPS) model tends to over predict the thermal radiation close to the flare. • The Integrated Diffuse Source (IDS) model tends to under predict the thermal radiation close to the flare. • Both models predict similar values for thermal radiation in the far field. The mixed source model is given by Equation (4) which is a linear combination of the IPS and IDS models.
K ims = aK ips + ( 1 – a )K ids
(4)
17.1.5 Brzustowski and Sommer Method The equation for the calculation of the heat flux at a given distance is identical to that given for the API method as Equation 1. Both this method and the API method are based upon the flame being considered as a single point heat source. The distance between the point source and the receptor is calculation from a flame shape which is based upon the diffusion of a turbulent jet to the to the lean flammability concentration limit [3]. Flaresim allows an extension to the standard Brzustowski method by allowing the user to specify multiple flame elements or an element position that is not 50%. In versions of Flaresim prior to 1.2 these options could be set for the Brzustowski method. In Flaresim 1.2 and following these options can only be set if the extended M.Point Brzustowski method is selected.
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17-8
Thermal Radiation
17.1.6 Chamberlain Method (Thornton Method) The Chamberlain method, also known as the Shell Thornton method, for modelling thermal radiation is based on modelling a flame as an inverted conical frustum emitting radiation from its surface. The method is explained in detail in references [14] and [15].
17.1.7 F Factors The F Factor or fraction of combustion heat radiated from a flame is the most important single parameter in the calculation of thermal radiation calculation. The following is a summary of the correlations available in Flaresim, see reference [13] except where otherwise indicated. Note that some of these correlations are explicitly for Fs. or fraction of heat radiated from surface of the flame whereas in others F is for fraction of total heat radiated. Natural gas (Chamberlain) Correlation based on tip exit velocity assuming a natural gas fluid of molecular weight 19.
F s = 0.11 + 0.21e
– 0.00323u j
(5)
Tan Correlation based on mole weight
F = 0.048 ⋅ MW
17-8
(6)
Calculation Methods
17-9
Kent Correlation based on mole weight.
50 ⋅ MW + 100 F = 0.2 ⋅ -----------------------------------900
(7)
High Efficiency Proprietary correlation between tip type, exit velocity, fluid molecular weight and degree of hydrocarbon saturation. Formally known as the Flaresim method in versions prior to 1.2. Cook Correlation based on exit velocity.
F = 0.321 – 0.000418u j
(8)
Generic Pipe Proprietary correlation based on refitting Kent, Tan, Natural gas and Cook methods across a range of exit velocities and molecular weights. Mod. Chamberlain Method This correlation corrects the basic Natural Gas (Chamberlain) method for mole weight [14].
F s = [ 0.11 + 0.21e
– 0.00323u j
] ⋅ f ( MW )
(9)
17-9
17-10
Thermal Radiation
where
f ( MW ) = 1, MW < 21 f ( MW ) = ( MW ⁄ 21 )
0.5
, 21 < MW < 60
f ( MW ) = 1.69, 60 < MW 17.1.8 Atmospheric Attenuation Brzustowski and Sommer[3] recommend the use of the atmospheric transmissivity, as the fraction of the heat intensity which is transmitted to a point, in order to correct the calculated values for thermal radiation. This correction is given by Equation (10).
Kτ = τ ⋅ K
(10)
In all cases, atmospheric absorption attenuates the incipient radiation at a point. This will typically be 10 to 20% over distances of up to 500 ft. The empirical Equation (11) given below was obtained by cross plotting absorptivities calculated from Hottel charts. It is strictly applicable only under the following conditions of: • • • •
A luminous hydrocarbon flame radiating at 2240 ° F Dry bulb temperature of 80 ° F Relative humidity greater than 10% Distances from flame between 100 and 500 ft
It is generally used to estimate the order of magnitude of the atmospheric transmissivity under a wider range of conditions.
100 0.0625 100 0.0625 τ = 0.79 --------⋅ --------H D
17-10
(11)
Calculation Methods
17-11
Equation(11) should prove adequate for most situations. However, for cases in which the design conditions are significantly different from those under which the equation was derived, the designer should revert to the Hottel charts. Equation (11) is implemented in Flaresim with 2 options, selected in the Environment view, see Chapter 7. If the Calculated method is selected, equation 6 is used after limiting the distance values to the minimum of 100ft and maximum of 500ft as per the strict applicability limits of the equation. If the CalcNoLimits method is selected, equation (11) is used without regard to the distance limits. Wayne Transmissivity Wayne [12] presented a method of calculating transmissivity as a function of distance that is effectively a function of both atmospheric temperature and humidity. The equation is. τ = 1.006 – 0.01171 ( Log 10 X ( H 2 O ) ) – 0.02368 ( Log 10 X ( H 2 O ) )
2
(12)
– 0.03188 ( Log 10 X ( CO 2 ) ) + 0.001164 ( Log 10 X ( CO 2 ) )
2
where X ( H 2 O ) = ( 288.651R H DS mm ) ⁄ T X ( CO 2 ) = 273.0D ⁄ T RH = Fractional humidity Smm = Saturated water vapour pressure in mmHg at T T = Atmospheric temperature K D = Distance between receptor and emittor m
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Thermal Radiation
17.1.9 Windchill The design of offshore flare systems often takes into account the effect of heat loss from the target surface due to windchill. Equation (13) gives the simple correction to the calculated value for thermal radiation.
Kw = K – Kf
(13)
The correction K f is taken from Figure 17-1 below. Figure 17-1, Windchill Correction
For conditions beyond the range of this figure, the following constraints are applied:• If the wind speed is greater than 35 knots, the 35 knot value is used.
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Calculation Methods
17-13
• If the ambient temperature is less that 30 ° F, the 30 ° F value is used. If the ambient temperature is greater than 80 ° F, the correction is taken to be zero regardless of the wind speed
17.1.10 Flame Shape The calculation of the distance between any point on the flame and the target receptor requires a knowledge of the flame length and shape. This is a function of: • Flare exit velocity • Wind speed and direction • Orientation of the tip The flare exit velocity is calculated by simply dividing the volumetric flare rate by the cross sectional area of the flare tip according to Equation 8.
4WZRT u j = ------------------2 PMπd
(14)
The gas mach number is calculated from the sonic velocity which is calculated from Equation (15).
us =
gkRT ------------M
(15)
The pressure used in equation (14) for a tip operating at sub-sonic velocity is either the specified tip exit pressure or the pressure specified for the active environment. Where the tip operates at sonic velocities an iterative calculation is made to find the pressure at which the tip can pass the specified mass flow at the sonic velocity calculated at that pressure.
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Thermal Radiation
The temperature used in these equations is either the specified fluid temperature or, when the temperature correction option is selected the fluid temperature corrected for adiabatic isentropic expansion/ contraction from the specified fluid reference pressure. API & Integrated Methods The method for calculation of the flame length and deflection is dependent upon the method selected for calculation of the thermal radiation. If the API, IPS, IDS or IMS method is selected then the flame length is calculated from the heat released by the flame, then the deflection is calculated by resolving the vectors for the jet, flame buoyancy and wind. The flame length is calculated from an empirical equation (16) relating the flame length to the heat release. The heat release is the total heat produced by the combustion of the fluid.
Q = W ⋅ LHV
(16)
The flame length is calculated from Equation (17). The constants l1 and l2 are a function of the type of tip
Q I2 L = I 1 ---N
(17)
Tip Type
l1
l2
Pipe flare
0.00331
0.4776
Single Burner Sonic
0.00241
0.4600
Multiple Burner Sonic
0.00129
0.5000
Steam and air assisted flares will generally have shorter flames than those calculated by these equations. The program contains proprietary algorithms for prediction of the shortening of the flame
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Calculation Methods
17-15
as a function of the rate of injection of the assist fluid. Due to the proprietary nature of these algorithms, they are not presented here. In windy conditions the flame will be distorted from the straight vertical. This distortion may be calculated by the resolution of the velocity vectors for the exit jet, wind and flame buoyancy. The jet velocity as a function of the curvilinear distance along the flame is modelled according to the formula proposed by McMurray[4].
1 1 u l = 5.0u j d --- – --l A
(18)
Equations (19), (20) and (21) are resolved according to the Cartesian coordinate system shown by Figure 17-2.
dx ------ = u l sin Φ cos ω + u ∞ cos ψ dt
(19)
dy ------ = u l sin Φ cos ω + u ∞ sin ψ dt
(20)
dz ----- = u l cos Φ + u b dt
(21)
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17-16
Thermal Radiation
Figure 17-2, Coordinate System
Brzustowski If the Brzustowski method [3] is selected then the flame length and deflection are calculated from a method based upon the distance required for the dilution of the flared gas to the lean flammability limit concentration. Dimensionless parameters are defined which relate the lean flammability limit concentration and the following parameters to the deflection of the end point of the flame: • Tip exit velocity • Wind velocity • Gas molecular weight • Air molecular weight • Tip diameter
17-16
Calculation Methods
17-17
The following dimensionless parameters are defined:
Mj uj c l = c l ------ ⋅ -------u∞ M∞
(22)
xl x l = -------------------------dj uj ρ --------- ⋅ ------ju∞ ρ∞
(23)
zl z l = -------------------------dj uj ρ --------- ⋅ ------ju∞ ρ∞
(24)
Figure 17-3 gives the values for the horizontal and vertical distance factors for a range of values for the dimensionless concentration parameter.
17-17
17-18
Thermal Radiation
Figure 17-3, Dimensionless Distance Parameters
This procedure cannot strictly be used for calculation of the flame deflection in cases where there is no wind. The limiting case is a ratio of gas exit velocity to wind velocity of 110. This value corresponds to a sonic discharge of methane at 400 ° F into a 10 mph wind. When analysing any calculation results this ratio should be checked if you are evaluating the effect of low wind speeds. Chamberlain (Thornton) The Chamberlain method models the flame as an inverted conical frustum as shown in Figure 17-4 below. See reference [15] for the methods used to calculate the characterising dimensions.
17-18
Calculation Methods
17-19
Figure 17-4, Chamberlain Flame Model
W2
θ
α
RL
L W1
b
Flare Stack
17-19
17-20
Surface Temperature
17.2 Surface Temperature The equilibrium surface temperature of metal surfaces exposed to the thermal radiation is calculated from a heat balance between the thermal radiation from the flame incident at the specified point and the heat losses from the same point.
Kα = ( h c + h r ) ⋅ ( T m – T ∞ )
(25)
This heat balance equation assumes that heat losses by convection and radiation occur only from the surface exposed to the radiation. The overall heat loss from the point is the sum of the radiation from the point and the forced/free convection from the point. The radiative heat transfer coefficient is given by: 4
4
( Tm – T∞ ) h r = σE ⋅ -----------------------------( Tm – T∞ )
(26)
Convective heat transfer coefficients are calculated from a series of empirical correlations that are a function of air velocity. 0 ≤ u ∞ ≤ 15
h c = 0.80 + 0.22u ∞
(27)
u ∞ > 15
h c = 0.56u ∞
0.75
(28)
A value of 0.70 is used for both the absorbtivity and emissivity of the surface. This is a typical value for steels.
17-20
Calculation Methods
17-21
17.3 Noise The noise generated by a flare may be broken down into 2 basic components: • Combustion noise • Jet noise Although the noise may be expressed in terms of an average value, it is frequency dependant. The shape of this noise spectrum is dependant upon whether the major contribution is due to combustion noise as in the case of pipe flares, or jet noise as in the case of sonic flares. The noise spectrum is generally given in 7 octave bands from 63 Hz to 8000 Hz. Attenuation of the noise occurs due to atmospheric absorption. This absorption is a function of the frequency of the noise with higher frequencies being more readily absorbed. Noise is expressed either in terms of the Sound Power Level (PWL) or the Sound Pressure Level (SPL) where these terms are defined by Equations 23 and 24.
W PWL = 10 log ------- W 0
(29)
P2 SPL = 10 log --------- P 2 0
(30)
The international standard reference conditions are 10-12 Watts (W0) and 2 x 10-6 N/m2 (P0). In the case of a flare stack where the acoustic source may be considered to be in a free field with directivity factor of unity then
17-21
17-22
Noise
the Sound Pressure Level is related to the Sound Power Level by Equation 25.
SPL = PWL – 20 log D – 0.49 – SPL A
(31)
Noise data predicted by the program refer to the Sound Pressure Level in all cases.
17.3.1 Combustion Noise Combustion noise is a function of the heat release from the flame and the design of the flare tip. The calculation of the noise spectrum due to combustion is based upon a typical characteristic curve for the type of tip under consideration (pipe, sonic etc). An example of the shape is given by Figure 17-5 which gives the noise levels at a distance of 20 ft from a combustion source of power 81 MM btu/hr. The noise level at each frequency is then corrected for the actual combustion duty and distance from Equation 26.
Q SPL = SPL 20 + 10 log --------------------- + 6 81 × 10 20 20log ------ – SPL A D
17-22
(32)
Calculation Methods
17-23
Figure 17-5, Typical Noise Combustion Spectrum
17.3.2 Jet Noise The expansion of an unchoked gas stream will produce noise whose sound power at the peak frequency is determined from the kinetic energy and acoustic efficiency of the expanded jet according to Equation 27 [6]. 2
ρj uj PWL = ηV -----------2
(33)
The acoustic efficiency of the expanded jet is related to the jet velocity and whether or not the flow is choked.
17-23
17-24
Noise
If the flow is not choked, then the acoustic efficiency may be obtained from Figure 17-6. In this figure the dimensionless factor B is given by the equation:
ρj Tj 2 B = ------- ⋅ ------- ρ ∞ T ∞
(34)
Figure 17-6, Acoustic Efficiency For Normal Flow
If the flow is choked, then the acoustic efficiency may be obtained from Figure 17-7.
17-24
Calculation Methods
17-25
Figure 17-7, Acoustic Efficiency For Choked Flow
The expansion of a gas stream will produce noise which has a spectrum which peaks with a frequency calculated by a method due to MacKinnon [6].
0.2mu s f max = ----------------dj
(35)
At frequencies other than the peak frequency the noise is calculated using Equation 30.
17-25
17-26
Noise
SPL i = SPL tot – 10 ⋅ f i 2 f max 4 log 1 + -------------- 1 + ----------- – 5.3 2f max 2f i
(36)
17.3.3 Atmospheric Attenuation At distances greater than approximately 100 ft, the noise becomes attenuated due to absorption by the atmosphere. The attenuation is a function of the frequency of the noise, with higher frequencies being more readily attenuated than lower ones. Figure 17-8 gives the attenuation of noise for a range of frequencies. This figure is strictly applicable only to still air at a temperature of 70 ° F and a relative humidity greater than 60%. Extension to temperatures in the range 40 ° F to 100 ° F may be made by increasing the attenuation by 10% for each 10 ° F below 70 ° F.
17-26
Calculation Methods
17-27
Figure 17-8, Atmospheric Attenuation Of Noise
17-27
17-28
Purge Gas
17.4 Purge Gas This section details the different methods used to calculate purge gas rates.
17.4.1 HUSA Method The full HUSA method is based on the following equation 31[8].
Q p = 0.07068d
3.46 1
20.9 --- ln --------- F y O2 b
(37)
where Qp d O2 y Fb
Purge rate (ft3/h) Stack diameter (in) % oxygen Depth into stack (ft) Gas buoyancy factor
The gas buoyancy factor F b is calculated using either equation 32 or 33. Where composition of purge gas is known, equation 32 is used[8].
Fb =
Ci
0.65
exp [ 0.065 ( 29 – M i ) ]
i where Ci Volume fraction of ith component Mi Molecular weight of ith component
17-28
(38)
Calculation Methods
17-29
Where only the molecular weight of the purge gas is known, equation 33 is used[9].
F b = 6.25 [ 1 – 0.75 ( M ⁄ 28.96 )
1.5
]
(39)
where M Molecular weight of purge gas. If the purge gas buoyancy factor calculated using either method is less than the buoyancy factor of nitrogen then the buoyancy factor for nitrogen is used.
17.4.2 Reduced HUSA Method The reduced HUSA method is based on the following equation 34.[8]
Q p = 0.003528d
3.46
Ci
0.65
Ki
(40)
i where Qp d Ci Ki
Purge rate (ft3/h) Stack diameter (in) Volume fraction of ith component Constant for ith component from following table
17-29
17-30
Purge Gas
Component
K
Hydrogen
5.783
Helium
5.078
Methane
2.328
Nitrogen
1.067 (no wind) 1.707 (wind)
Ethane
-1.067
Propane
-2.651
Carbon Dioxide
-2.651
Butane and heavier
-6.586 0.65
If the sum of the C i K i terms is less than the K value for nitrogen then the value for nitrogen is used.
17-30
Calculation Methods
17-31
17.5 Water Sprays The modelling of water sprays used for shields is based on the method presented by Long and Rogers [10]. The transmissivity of the water curtain is given by the ratio
E τ = -----Eb
(41)
where
τ E Eb
Transmissivity Total transmitted flux Total black body radiated flux
The total transmitted flux is calculated by integration over the range of radiation wavelengths emitted by the flame. λ max
E =
( λ
min )
E λb exp ( – α λ ⋅ s )
(42)
where
E λb λ αλ s
Black body radiation at wavelength λ , W/m2 Radiation wavelength, m Absorption coefficient at wavelength λ m-1 Thickness of water curtain layer m
The black body radiation at wavelength λ is given by the Planck equation. 2 –5
E λb = ( 2πHc λ
) ⁄ ( exp ( ( Hc ) ⁄ ( KλT ) – 1 ) )
(43)
17-31
17-32
Water Sprays
where
H c λ K T
Planck constant J/s Speed of light m/s2 Wavelength of radiation m Boltzman constant J/K Temperature K
The absorption coefficient for water is calculated by interpolation from graphical data presented in the paper [10].
17.5.1 Thickness of Water Curtain The effective thickness of a water curtain is calculated for a given water flow and nozzle characteristics using an equation presented by Long, [11].
6u noz s = ( ( 0.5D noz ) ⁄ π ) ------------u drop where
s Layer thickness m D noz Nozzle diameter m u noz Nozzle exit velocity m/s u drop Droplet velocity m/s
17-32
(44)
Calculation Methods
17-33
17.6 Gas Dispersion Flaresim includes two separate gas dispersion models. The first is a jet dispersion model intended to calculate flammable gas concentrations close to the flare tip in the event of a flame out condition. The second is a Gaussian dispersion model intended to model the dispersion over longer distances of combustion gases or flared gas components in the event a flame out.
17.6.1 Jet Dispersion The jet dispersion model provided by Flaresim is that proposed by Cleaver and Edwards [16]. This is an integral model for predicting dispersion of a turbulent jet into a cross flow in the absence of any obstructions. The implementation in Flaresim generalises this model into the 3 dimensional coordinate system used by Flaresim. The model is limited to wind speeds of less than 20 m/s. The model cannot be used for horizontal tips projecting directly into the wind.
17.6.2 Gaussian Dispersion The Gaussian Dispersion calculations are based on the widely used generalised gaussian dispersion equation for a continuous pointsource plume. 2 2 – y ⁄ ( 2σ y ) Q C = ---------------------- ⋅ e uσ z σ y 2π 2
e
–( zf – He ) ⁄
2 2σ z
2
+e
–( zf + He ) ⁄
2 2σ z
(45)
17-33
17-34
Gas Dispersion
where C = Emissions concentration g/m3 at receptor located at x m downwind y m crosswind from centre line z m above ground Q = Source emission rate, g/s u = Horizontal wind velocity m/s He = plume centre line above ground, m σ z = vertical standard deviation of emissions distribution m σ y = horizontal standard deviation of emissions distribution m This equation is valid subject to the following constraints • Vertical and crosswind diffusion follow Gaussian distribution • Downwind diffusion is negligible • Emissions rate is constant and continuous • All emissions are conserved in plume • No barriers to diffusion other than ground • Emissions are reflected from ground as if generated from imaginary plume beneath the ground and are additive to primary plume. • Turbulence within x, y, z dimensions of plume is homogenous. The dispersion coefficients used by Flaresim σ z and σ y in equation (45) in rural terrain are calculated using McMullen’s equation fit to the Pasquill dispersion coefficients published by Turner[17], page 53. In urban terrain the equation developed by Gifford to fit the dispersion coefficients published by Briggs are used [17], page 56. In both cases the data to which equations apply is for distances greater than 100 m downwind of the source. The Gaussian Dispersion equation (45) requires the effective height of the plume He. This is calculated using the Briggs equations for a bent-over buoyant plume in their 1972 version [17], pages 72, 73. The Briggs buoyancy parameter required by these equations is calculated using the fully generalised method given in [17], page 184. The effective release height for dispersion of combustion gases
17-34
Calculation Methods
17-35
is taken to be the end of the flame calculated using Flaresim’s standard methods. Where multiple tips are in operation the final emission concentrations are calculated by simple addition of the contributions from the individual tips.
17.6.3 Emission Rates The default NOx, CO and unburnt hydrocarbon emission rates calculated by Flaresim are based on the heat released and are taken from the John Zink Combustion Handbook [18]. The Sintef method for NOx emission prediction is based on the following equation, given in reference [19].
u0 3⁄5 EI NOx ------------ = 3.5 ⋅ Fr d 0.55 0
(46)
where EINOx = NOx emissions rate in gNOx / kg fuel 2 Fr = Froude number = u 0 ⁄ g ⋅ d 0 u 0 = Nozzle outlet velocity m/s at ambient conditions (298K, 1.013 bar) d 0 = Nozzle outlet diameter, m
17-35
17-36
Nomenclature
17.7 Nomenclature The following nomenclature is used in this chapter unless otherwise specified in the body of the text.
17.7.1 Symbols A a B c D d E F Fs f H h L LHV l l1 l2 M m N K k P
API flame length (ft) Empirical constant used in IMS method Dimensionless scaling parameter Flammability lean limit concentration Distance from flame midpoint to receptor (ft) Tip diameter (ft) Metal surface emissivity Fraction of heat radiated Fraction of heat radiated from surface of flame Frequency (Hz) Relative humidity (%) Heat transfer coefficient (btu/hr/ft2/(R) Flame length (ft) Lower heating value (btu/lb) Curvilinear flame length (ft) Constant in flame length equation Constant in flame length equation Molecular weight Mach number Number of burners in tip assembly Thermal radiation at receptor (btu/hr/ft2) Heat capacity ratio Pressure (psi a) PWL Sound Power Level (W) Heat release based upon LHV (btu/hr) Q Universal gas constant R SPL Sound Pressure Level (dB) Temperature ((R) T Velocity (ft/s) u Volumetric flow (ft3/s) V
17-36
Calculation Methods
W x x' y Z z' z α β η ω Φ ψ ρ σ τ
17-37
Flow rate (lb/hr) Distance north of tip (ft) Horizontal plume distance factor Distance east of tip (ft) Compressibility factor (-) Vertical plume distance factor Distance above tip (ft) Metal surface absorbtivity Angle between flame tangent and line of sight to receptor (degrees) Efficiency Rotation of flare from x axis (degrees) Angle of tip from vertical (degrees) Rotation of wind from x axis (degrees) Fluid density (lb/ft3) Stephan Boltzman constant (0.171 x 10-8 btu/hr/ft2/(R4) Transmissivity
17.7.2 Subscripts A b c f
i ids ims ips j l m r s w ∞ τ 0 20
Atmospheric attenuation Buoyancy Convective Correction Frequency band Integrated diffuse source Integrated mixed source Integrated point source Jet exit Curvilinear length Metal Radiative Sonic Corrected for windchill Wind/atmospheric Corrected for transmissivity Reference condition At 20 ft from source
17-37
17-38
References
17.8 References
17-38
1.
API RP521, “Guide For Pressure-Relieving and Depressuring Systems”, 4th ed, American Petroleum Institute, Washington DC, 1997.
2.
Hajek, J.D. and Ludwig, E.E., “How To Design Safe Flare Stacks”, Part 1, Petro/Chem Engineer, 1960, Vol 32, No. 6, pp.C31-C38; Part2, Petro/Chem Engineer, 1960, Vol 32, No. 7, pp.C44-C51.
3.
Bruztowski, T.A. and Sommer, E.C. Jr., “Predicting Radiant Heating From Flares”, Proceedings - Division of Refining, Vol. 53, pp. 865-893, American Petroleum Institute, Washington DC, 1973.
4.
McMurray, R., “Flare Radiation Estimated”, Hydrocarbon Processing, Nov. 1982, pp. 175-181.
5.
Narasimhan, N.D., “Predict Flare Noise”, Hydrocarbon Processing, April 1986, pp. 133-136.
6.
MacKinnon, J.G., “Recent Advances in Standardizing Valve Noise Prediction”, Society of Instrument & Control Engineers, Tokyo, Sept. 1984.
7.
Husa, H.W., “How to Compute Safe Purge Rates”, Hydrocarbon Processing, 1964, 43, No. 5.
8.
Husa, H.W., “Purging Requirements of Large Diameter Stacks”, American Petroleum Institute, Fall Meeting 1977.
9.
Shore, D, “Making the Flare Safe”, Journal of Loss Prevention Process Industry, 1996, Vol 9, No 6, 363-381
10.
Long, C.A and Rogers M.C, “Temperature Prediction for Surfaces Exposed to Flare Radiation and Attenuation of Radiative Fluxes by Water Curtain”, 5th International Conference - ‘Offshore Structures - Hazard & Integrity Management’ 4-5th December 1996.
Calculation Methods
17-39
11.
Long C.A. “Attenuation of Thermal Radiative Heat Fluxes by Water Curtain”, 1995, School of Engineering, University of Sussex, Report No 95/TFMRC/181.
12.
Wayne F.D. “An Economical Formula for Calculating Atmospheric Infrared Transmissivities”, Journal of Loss Prevention Process Industry, 1991, Vol 4, January, 86-92
13.
Guidard, S.E., W.B. Kindzierski and N. Harper, 2000. “Heat Radiation from Flares.” Report prepared for Science and Technology Branch, Alberta Environment, ISBN 0-77851188-X, Edmonton, Alberta
14.
Cook J., Bahrami Z, Whitehouse R.J. “A Comprehensive Program for Calculation of Flame Radiation Levels”, Journal of Loss Prevention Process Industry, 1990, Vol 3, January, 150-155
15.
Chamberlain G.A. “Developments in Design Methods for Predicting Thermal Radiation from Flares”, Chem Eng Res Des, Vol 65, July 1987, 299-309
16.
Cleaver R.P, Edwards P.D., "Comparison of an integral model for predicting the dispersion of a turbulent jet in a cross flow with experimental data", Journal of Loss Prevention Process Industry, 1990, Vol3, January 91-96
17.
Beychok M.R. “Fundamentals of Stack Gas Dispersion”, 2005 Edn. ISBN 0-9644588-0-2, Milton R. Beychok, 1102 Colony Plaza, Newport Beach, CA 92660.
18.
Baukal jr. C.E. (Editor), “John Zink Combustion Handbook”, 2001 Edn, ISBN 0-8493-2337-1, John Zink Company LLC, Tulsa, Oklahoma.
19.
Bakken J., Langørgen Ø, “Improving Accuracy in Calculating NOx Emissions from Gas Flaring”, Society of Petroleum Engineers International Conference on Health, Safety and Environment in Oil and Gas Exploration and Production, Nice, April 2009, SPE 111561.
17-39
17-40
17-40
References
Graphic Report Layout
A-1
A Graphic Report Layout Page A.1
Introduction to XML . . . . . . . . . . . . . . . . . . . 4
A.1.1 A.1.2 A.1.3
A.2
Tags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Layout File Structure . . . . . . . . . . . . . . . . . .6
A.2.1 A.2.2 A.2.3 A.2.4 A.2.5 A.2.6 A.2.7 A.2.8 A.2.9 A.2.10 A.2.11
Allowed Elements . . . . . . . . . . . . . . . . . . . . 6 PageSize Element . . . . . . . . . . . . . . . . . . . . 7 Text Element . . . . . . . . . . . . . . . . . . . . . . . . . 7 Unit Element . . . . . . . . . . . . . . . . . . . . . . . . . 8 Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Logo Element . . . . . . . . . . . . . . . . . . . . . . . 14 CaseData Element . . . . . . . . . . . . . . . . . . . 14 Line Element. . . . . . . . . . . . . . . . . . . . . . . . 15 PlotArea Element . . . . . . . . . . . . . . . . . . . . 16 LegendArea Element . . . . . . . . . . . . . . . . . 21 ContourSet Element. . . . . . . . . . . . . . . . . . 22
A-1
A-2
A-2
Graphic Report Layout
A-3
The appearance of graphic reports produced by Flaresim is controlled by layout files. These files contain a list of instructions in a XML format that describe how data items, graphic items, background text, background lines and background graphics will appear on the report. This appendix describes the format of the layout files.
A-3
A-4
Introduction to XML
A.1 Introduction to XML XML is a standardised markup language for describing structured data. The following description of the language is intended to introduce the terms used in this appendix. For a full description of the XML standard see http://www.w3.org/xml. The figure below shows a fragment of the XML language taken from one of the Flaresim layout files. Figure A-1, XML File Fragment
The basic building block of a XML file is the element. An element is a data fragment that has a tag, attributes and data.
A.1.1 Tags An element’s tag can be thought of as its name. A tag enclosed in a pair of “< >” brackets starts the description of an element and the same tag preceded by a / character and enclosed in a pair of “< >” brackets ends the description of the element. For example, an element containing text data might be given the tag Description and would appear as follows The descriptive text. A XML file can contain more than one element with the same tag describing repeating data items. Tags are case sensitive, i.e. is different to . Taking the XML fragment shown in Figure A-1 as an example, there are six elements in total with four unique tags namely , , and . There are three elements. A-4
Graphic Report Layout
A-5
A.1.2 Attributes The attributes of an element can be thought of as data parameters or additional descriptions of the element. Attributes are defined within the “< >” brackets of the elements opening tag. A single attribute is introduced by a name followed by an “=” sign followed by the value of the attribute enclosed in quotes. For example our Description tag might be extended to have an attribute called Font to define the typeface to be used to print it thus. The descriptive text An element may have no attributes or multiple attributes. Attribute names are case sensitive i.e. Font is different to font. Taking the XML fragment shown in Figure A-1 as a further example, the elements there each have four attributes name X, Y, Font and Size.
A.1.3 Data The data part of an element is contained between the opening tag and the closing tag. The data can be either text or another element. In our element example the data is the text “The descriptive text”. The data part of an element does not have to contain data, it can be empty if for example all of the data contained in an element is described through attributes. When the data part of an element is empty the closing “/” character can be included in the opening tag and the closing tag omitted thus. Looking at our example XML fragment shown in Figure A-1 again, we can see that the data sections of the elements contain descriptive text, the data section of the element contains a file name and the data section of the element contains another element introduced by the tag.
A-5
A-6
Layout File Structure
A.2 Layout File Structure A Flaresim graphic report layout file must contain the following top level data elements in order to be recognised as a valid graphic report layout file This defines the version of the XML standard used to encode the file and the unicode character set used. This is a standard element that must appear as the first element in the file. This element is the top level data element that contains all other elements that define the layout of the graphic report.
A.2.1 Allowed Elements The following element tags are recognised within the main element within the layout file. Each of these elements is described in more detail below. Element Tag
A-6
Description
Number
PageSize
Defines the overall dimensions
Single
Text
Defines background text
Multiple
Unit
Defines units of measurement
Multiple
Data
Defines data items
Multiple
Logo
Defines background graphics items
Multiple
CaseData
Defines case description items
Multiple
Line
Defines background lines
Multiple
PlotArea
Defines plot area and style
Single
LegendArea
Defines plot legend area and style
Single
ContourSet
Defines contour list and styles
Single
Graphic Report Layout
A-7
A.2.2 PageSize Element Description Defines the overall size of the plot to be produced. Attributes X Y
Size of plot in X dimension in mm. Size of plot in Y dimension in mm.
Data Value None.
A.2.3 Text Element Description Defines individual items of background text to appear on the plot such as titles and headings. Attributes X Y Font
Size Style
Required - X position in mm of the left edge of the text Required - Y position in mm of the centre line of the text Required - Integer denoting font to be used 0 = Arial 1 = Courier 2 = Times Roman Required - Value defining text height as % of plot page height Optional - Text describing style of text Bold Italic BoldItalic
Data Value The background text to be added to the plot.
A-7
A-8
Layout File Structure
A.2.4 Unit Element Description Defines individual items of unit of measurement text to appear on the plot. Attributes X Y Font
Size Style
Required - X position in mm of the left edge of the unit text Required - Y position in mm of the centre line of the unit text Required - Integer denoting font to be used 0 = Arial 1 = Courier 2 = Times Roman Required - Value defining unit text height as % of plot page height Optional - Text describing style of unit text Bold Italic BoldItalic
Data Value The name of the unit of measurement type to be output e.g. length, temperature. The full list of recognised type names is the same as the list of quantity names defined in the units.xml file as followstime, length, mass, temperature, sound, frequency, surface_area, volume, force, small_length, energy, pressure, velocity, plane_angle, fraction, percentage, power, mass_flow, mass_heat_capacity, mass_energy, heat_flux_density, heat_transfer_coefficient, mass_per_area, mass_density, volume_flow.
A.2.5 Data Description Defines individual data items that will appear on the plot.
A-8
Graphic Report Layout
Attributes X Y Font
Size Style
A-9
Required - X position in mm of the left edge of the data value Required - Y position in mm of the centre line of the value Required - Integer denoting font to be used 0 = Arial 1 = Courier 2 = Times Roman Required - Value defining data value height as % of plot page height Optional - Text describing style of data value Bold Italic BoldItalic
Data Value A data element defining the data item to be output as follows.
A.2.5.1 Var Element Description Identifies individual data item. Attributes Stack Tip
Optional - index of stack which variable is associated with. Optional - index of tip which variable is associated with. Note this is the index of the tip on the specified stack i.e. a Tip index value of 1 denotes the first tip on the specified stack regardless of whether the tip is the first listed in the model.
A-9
A-10
Layout File Structure
Data Value A text string identifying the data item to be output. The list of data identifiers recognised is as follows. Identifier
A-10
Stack Id
Tip Id
WindSpeed
Not specified
Not specified
WindDirection
Not specified
Not specified
SolarRadiation
Not specified
Not specified
Transmissivity
Not specified
Not specified
Humidity
Not specified
Not specified
BackgroundNoise
Not specified
Not specified
TransmissivityMin
Not specified
Not specified
TransmissivityMax
Not specified
Not specified
AtmTemperature
Not specified
Not specified
AtmPressure
Not specified
Not specified
CalculationMethod
Not specified
Not specified
NumberOfElements
Not specified
Not specified
BuoyancyPipe
Not specified
Not specified
BuoyancySonic
Not specified
Not specified
BuoyancyWellTest
Not specified
Not specified
OptSolarRadiation
Not specified
Not specified
OptWindchill
Not specified
Not specified
OptBackgroundNoise
Not specified
Not specified
OptAtmNoiseAttenuation
Not specified
Not specified
OptAdiabaticTempCorr
Not specified
Not specified
OptRKZFactor
Not specified
Not specified
NoiseCalcMethod
Not specified
Not specified
Graphic Report Layout
Identifier
Stack Id
A-11
Tip Id
Name
Required
Not specified
Length
Required
Not specified
AngleToHorizontal
Required
Not specified
AngleToNorth
Required
Not specified
Name
Required
Required
Type
Required
Required
NbrOfBurners
Required
Required
Length
Required
Required
Diameter
Required
Required
BurnerOpening
Required
Required
ContractionCoefficient
Required
Required
ExitLossCoefficient
Required
Required
Roughness
Required
Required
OutletPressureSpec
Required
Required
SealType
Required
Required
AngleToHorizontal
Required
Required
AngleToNorth
Required
Required
Fluid
Required
Required
MassFlow
Required
Required
LHV
Required
Required
MW
Required
Required
CpCv
Required
Required
EmissivityMethod
Required
Required
Emissivity
Required
Required
Temperature
Required
Required
A-11
A-12
Layout File Structure
Identifier
A-12
Stack Id
Tip Id
RiserDiameter
Required
Required
NoiseMethod
Required
Required
NoiseSPL
Required
Required
PeakFrequency
Required
Required
CombustionEfficiency
Required
Required
ExitVelocity
Required
Required
MachNumber
Required
Required
VolumeFlow
Required
Required
HeatRelease
Required
Required
FlameLength
Required
Required
APIFlameLength
Required
Required
WindSpeedAtTip
Required
Required
TipExitPressure
Required
Required
TipInletPressure
Required
Required
TipDP
Required
Required
SealInletPressure
Required
Required
SealDP
Required
Required
StackInletPressure
Required
Required
StackDP
Required
Required
TotalTipExitPressure
Required
Required
TotalTipInletPressure
Required
Required
TotapTipDP
Required
Required
TotalSealInletPressure
Required
Required
TotalSealDP
Required
Required
TotalStackInletPressure
Required
Required
Graphic Report Layout
Identifier
Stack Id
A-13
Tip Id
TotalStackDP
Required
Required
PurgeFluid
Required
Required
PurgeFixVolFlow
Required
Required
PurgeHUSAO2
Required
Required
PurgeHUSAHeight
Required
Required
PurgeFixedVel
Required
Required
PurgeFixVelCalcFlow
Required
Required
PurgeFixVolFlowCalcVel
Required
Required
PurgeFixVolFlowCalcFlow
Required
Required
PurgeHUSACalcVel
Required
Required
PurgeHUSACalcFlow
Required
Required
PurgeRedHUSACalcVel
Required
Required
PurgeRedHUSACalcFlow
Required
Required
Fluid2
Required
Required
MassFlow2
Required
Required
LHV2
Required
Required
MW2
Required
Required
CpCv2
Required
Required
Temperature2
Required
Required
AssistFluid
Required
Required
AssistFluidMassFlow
Required
Required
AssistFluidFlowRatio
Required
Required
A-13
A-14
Layout File Structure
A.2.6 Logo Element Description Defines individual graphic files to be output on the plot. This is usually used to include company logos etc in the plot. Attributes X1 Y1 X2 Y2
Required - X position in mm of the top left corner of the graphic item. Required - Y position in mm of the top left corner of the graphic item. Required - X position in mm of the bottom right corner of the graphic item. Required - Y position in mm of the bottom right corner of the graphic item.
Data Value A text string naming the graphic file to be included.
A.2.7 CaseData Element Description Defines items of case description data that will appear on the plot. Attributes X1 Y1 X2 Y2 Font
Size
A-14
Required - X position in mm of the top left corner of the area for output of the data item. Required - Y position in mm of the top left corner of the area for output of the data item. Required - X position in mm of the bottom right corner of the area for output of the data item. Required - Y position in mm of the bottom right corner of the area for output of the data item. Required - Integer denoting font to be used 0 = Arial 1 = Courier 2 = Times Roman Required - Value defining data item text height as % of plot height
Graphic Report Layout
Style
A-15
Optional - Text describing style of data value Bold Italic BoldItalic
Data Value A text string defining the data item to be output. Recognised values are. Title DataFile Description LastModified Author Revision CheckedBy FSWVersion ActiveCaseName ActiveCaseTag ActiveCaseDesc ActiveCaseTime
A.2.8 Line Element Description Defines background lines to be drawn on the plot. Typically these are used to frame areas of the report. Attributes X1 Y1 X2 Y2 LineWidth
Required - X position in mm of the first end of the line. Required - Y position in mm of the first end of the line. Required - X position in mm of the second end of the line. Required - Y position in mm of the second end of the line. Required - Line width in pixels.
A-15
A-16
Layout File Structure
Data Value None
A.2.9 PlotArea Element Description Defines the area used to output the isopleth graph on the plot and sets the options used when drawing it. Attributes X1 Y1 X2 Y2
Required - X position in mm of the top left corner of the graph area. Required - Y position in mm of the top left corner of the graph area. Required - X position in mm of the bottom right corner of the graph area. Required - Y position in mm of the bottom right corner of the graph area.
Data Value Elements defining the options used to draw the isopleth graph as follows. Note one instance of each of these elements is required in the data. None of these elements has any data value, all the required information is contained as attributes.
A.2.9.2 Grid Element Description Describes how the background grid for the isopleth graph is to be drawn. Attributes Display Lines
A-16
Required - defines whether grid is drawn. Allowed values are Yes or No. Required - defines number of grid lines within graph on each axid. Integer
Graphic Report Layout
BackColour
A-17
Required - defines colour of graph background. Value can be Transparent or one of the colours from Table A.1 below.
Table A.1, Allowed Colours Yellow Red Green Cyan Orange Lemon PaleGreen BlueGreen PaleBlue LightGrey MidGrey DarkGrey White Black Other colours may be defined using a hex code to define the RGB contributions as follows 0xRRGGBB where RR is red value, GG is green value and BB blue value in hex. For example 0xFF0000 is pure red.
A.2.9.3 Title Element Description Defines how the isopleth graph title will be output. The title is the name of the receptor grid that the isopleth applies to. Attributes Display Space
Required - defines whether title is included. Allowed values are Yes or No. Required - Vertical spacing allowed for title as a percentage of the Y range of the graph.
A-17
A-18
Layout File Structure
Font
Size Style
Required - Integer denoting font to be used 0 = Arial 1 = Courier 2 = Times Roman Required - Value defining title text height as % of graph height. Optional - Text describing style of title text Bold Italic BoldItalic
A.2.9.4 Desc Element Description Defines how the graph description will be output. The description identifies whether the graph is a radiation, noise or temperature isopleth and the current units of measurement. Attributes Display Space Font
Size Style
Required - defines whether description is included. Allowed values are Yes or No. Required - Vertical spacing allowed for description as a percentage of the Y range of the graph. Required - Integer denoting font to be used 0 = Arial 1 = Courier 2 = Times Roman Required - Value defining description text height as % of graph height. Optional - Text describing style of description text Bold Italic BoldItalic
A.2.9.5 XAxis Element Description Defines how the isopleth X axis label will be output. A-18
Graphic Report Layout
Attributes Display Space Font
Size Style
A-19
Required - defines whether X axis label is included. Allowed values are Yes or No. Required - Vertical spacing allowed for X axis label as a percentage of the Y range of the graph. Required - Integer denoting font to be used 0 = Arial 1 = Courier 2 = Times Roman Required - Value defining title X axis label height as % of graph height. Optional - Text describing style of X axis label text Bold Italic BoldItalic
A.2.9.6 YAxis Element Description Defines how the isopleth Y axis label will be output. Attributes Display Space Font
Size Style
Required - defines whether Y axis label is included. Allowed values are Yes or No. Required - Horizontal spacing allowed for Y axis label as a percentage of the X range of the graph. Required - Integer denoting font to be used 0 = Arial 1 = Courier 2 = Times Roman Required - Value defining Y axis label height as % of graph height. Optional - Text describing style of Y axis label text Bold Italic BoldItalic
A-19
A-20
Layout File Structure
A.2.9.7 Scale Element Description Defines how the scale labels will be output. Attributes Font
Size
Required - Integer denoting font to be used 0 = Arial 1 = Courier 2 = Times Roman Required - Value defining scale label height as % of graph height.
A.2.9.8 Flare Element Description Defines how the stack, tip and flare will be drawn on the isopleth graph. Attributes Display
Required - defines whether the flare will be drawn. Allowed values are Yes or No. FlameThick Required - defines thickness of line used to draw flame in pixels. FlameColour Required - defines colour of line used to draw flame. Allowed values are given in Table A.1. StackThick Required - defines thickness of line used to draw stack in pixels. StackColour Required - defines colour of line used to draw stack. Allowed values are given in Table A.1. TipThick Required - defines thickness of line used to draw tip in pixels. TipColour Required - defines colour of line used to draw tip. Allowed values are given in Table A.1.
A-20
Graphic Report Layout
A-21
A.2.10 LegendArea Element Description Defines the area used to output the legend for the isopleth graph on the plot and sets the options used when drawing it. Attributes X1 Y1 X2 Y2
Required - X position in mm of the top left corner of the legend data area. Required - Y position in mm of the top left corner of the legend data area. Required - X position in mm of the bottom right corner of the legend data area. Required - Y position in mm of the bottom right corner of the legend data area.
Data Value Elements defining the options used to draw the legend data on the isopleth graph as follows. Note one instance of each of these elements is required in the data. None of these elements has any data value, all the required information is contained as attributes.
A.2.10.9 Layout Element Description This defines the number of columns used to output the legend and the characteristics of the text part of the legend. Attributes NumCols Font
Size
Required - Integer defining number of colums to be used for drawing the legend. Required - Integer denoting font to be used for legend label 0 = Arial 1 = Courier 2 = Times Roman Required - Value defining legend label height as % of legend data area height. A-21
A-22
Layout File Structure
A.2.10.10 Desc Element Description Defines how the legend description will be output. The description identifies whether the graph is a radiation, noise or temperature isopleth as well as the units used. Attributes Display Font
Size Style
Required - defines whether description is included. Allowed values are Yes or No. Required - Integer denoting font to be used 0 = Arial 1 = Courier 2 = Times Roman Required - Value defining description text height as % of legend data area height. Optional - Text describing style of description text Bold Italic BoldItalic
A.2.11 ContourSet Element Description Defines the details of the contours to be output on the isopleth graph. Attributes UseLayout
Required - Specifies whether the contour data from the layout file is to be used. Allowed values Yes or No. If set to Yes the contour data will be taken from the layout file. If not, the contour data will be taken from the current isopleth definition for the receptor grid.
Data Value Multiple elements defining the individual contour lines to be output. Up to 10 instances of , and can be specified.
A-22
Graphic Report Layout
A-23
A.2.11.11 RadiationContour Element Description Defines the details of a single radiation contour to be output on the isopleth graph. Attributes IsoValue Colour LineWidth Style
Required - Specifies the radiation value of the isopleth contour in internal program units of W/m2. Required - Specifies the colour used to draw the contour. Allowed values are given in Table A.1. Required - Integer specifying the width of the line used to draw the contour in pixels. Required - Specifies the style of the line used to draw the contour. Allow values are. Solid Dashed Dotted DashDot DashDotDot
A.2.11.12 NoiseContour Element Description Defines the details of a single noise contour to be output on the isopleth graph. Attributes IsoValue Colour LineWidth Style
Required - Specifies the noise value of the isopleth contour in internal program units of dB. Required - Specifies the colour used to draw the contour. Allowed values are given in Table A.1. Required - Integer specifying the width of the line used to draw the contour in pixels. Required - Specifies the style of the line used to draw the contour. Allow values are. Solid Dashed Dotted A-23
A-24
Layout File Structure
DashDot DashDotDot
A.2.11.13 TemperatureContour Element Description Defines the details of a single temperature contour to be output on the isopleth graph. Attributes IsoValue Colour LineWidth Style
A-24
Required - Specifies the temperature value of the isopleth contour in internal program units of K. Required - Specifies the colour used to draw the contour. Allowed values are given in Table A.1. Required - Integer specifying the width of the line used to draw the contour in pixels. Required - Specifies the style of the line used to draw the contour. Allow values are. Solid Dashed Dotted DashDot DashDotDot
