WL110e V1.1 Duplex
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Experiment Instructions WL 110-SERIES Heat Exchanger with Service Unit
WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
All rights reserved, G.U.N.T. Gerätebau, Barsbüttel, Germany 11/2011
WL 110.04 WL 110
WL 110.01
WL 110.03
WL 110.02
Experiment Instructions Dipl.-Ing. (FH) Klaus Schröder
This manual must be kept by the unit. Before operating the unit: - Read this manual. - All participants must be instructed on handling of the unit and, where appropriate, on the necessary safety precautions.
Version 1.1
Subject to technical alterations
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
Table of Contents 1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1 Modular design of WL 110 series . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Objectives of unit, target group and learning content . . . . . . . . . . . . . 2 1.3 Information for the teacher . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2
Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
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2.1 Intended Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.2 Structure of the Safety Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.3 Safety instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3
Unit description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.1 Introduction to the WL 110 series . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.2 WL 110 Heat Exchanger with Supply Unit process schematic . . . . . 11 3.3 WL 110 Service Unit with Heat Exchanger . . . . . . . . . . . . . . . . . . . . 13 3.4 Unit function and components, WL 110 Service Unit with Heat Exchanger . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.4.1
Unit description and function . . . . . . . . . . . . . . . . . . . . . . . . 14
3.4.2
Control and display panel . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
3.5 Data acquisition program. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 3.5.1
Installing the program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
3.5.2
Operating the program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3.6 WL 110.01 Tubular Heat Exchanger unit description . . . . . . . . . . . . 25 3.6.1
Layout and function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
3.6.2
Connection to the service unit . . . . . . . . . . . . . . . . . . . . . . . 26
3.6.3
General information for tubular heat exchanger . . . . . . . . . . 27
3.7 WL 110.02 Plate Heat Exchanger unit description . . . . . . . . . . . . . . 28 3.7.1
Layout and function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
3.7.2
Connection to the service unit . . . . . . . . . . . . . . . . . . . . . . . 29
3.7.3
General information for plate heat exchanger . . . . . . . . . . . 30
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
3.8 WL 110.03 Shell & Tube Heat Exchanger unit description . . . . . . . . 32 3.8.1
Layout and function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
3.8.2
Connection to the service unit . . . . . . . . . . . . . . . . . . . . . . . 33
3.8.3
General information for shell and tube heat exchanger . . . . 34
3.9 WL 110.04 Jacketed Vessel with Stirrer and Coil unit description . . 35 3.9.1
Layout and function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
3.9.2
Connection to the service unit . . . . . . . . . . . . . . . . . . . . . . . 38
3.9.3
General information for jacketed heat exchanger . . . . . . . . . 39
3.10 Commissioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 3.11 Hot water pump does not start? . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 3.12 Shutting down . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 4
Fundamental principles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 4.1 Heat transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 4.2 Indirect heat transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 4.2.1
Heat transfer from fluid-partition. . . . . . . . . . . . . . . . . . . . . . 47
4.2.2
Thermal conduction in the partition. . . . . . . . . . . . . . . . . . . . 48
4.2.3
Heat transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
4.2.4
Analogy to fluid dynamics and electrics . . . . . . . . . . . . . . . . 50
4.3 Heat flow through the heat exchanger. . . . . . . . . . . . . . . . . . . . . . . . 51 4.4 Temperature curve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 5
Experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 5.1 Experiments with WL 110.01, WL 110.02 and WL 110.03 . . . . . . . . 57
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5.1.1
Experiment aims . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
5.1.2
Experiment series, general conditions . . . . . . . . . . . . . . . . . 58
5.1.3
Experimental setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
5.1.4
Performing the experiment . . . . . . . . . . . . . . . . . . . . . . . . . . 59
5.1.5
Measured values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
5.1.6
Analysis, comments and evaluation . . . . . . . . . . . . . . . . . . . 65
WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
5.2 Experiments with WL 110.04. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
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5.2.1
Experiment aim. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
5.2.2
General conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
5.2.3
Experimental setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
5.2.4
Performing the experiment . . . . . . . . . . . . . . . . . . . . . . . . . . 75
5.2.5
Measured values, time response . . . . . . . . . . . . . . . . . . . . . 77
5.2.6
Analysis, comments and evaluation . . . . . . . . . . . . . . . . . . . 78
Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 6.1 Technical data for WL 110, Heat Exchanger Service Unit . . . . . . . . 79 6.2 Technical data for accessories (heat exchangers) . . . . . . . . . . . . . . 81 6.2.1
WL 110.01 Tubular Heat Exchanger . . . . . . . . . . . . . . . . . . 81
6.2.2
WL 110.02 Plate Heat Exchanger . . . . . . . . . . . . . . . . . . . . 82
6.2.3
WL 110.03 Shell and Tube Heat Exchanger . . . . . . . . . . . . 83
6.2.4
WL 110.04 Jacketed Vessel with Stirrer and Coil . . . . . . . . . 84
6.3 List of abbreviations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 6.4 List of key symbols and units used . . . . . . . . . . . . . . . . . . . . . . . . . . 86 6.5 List of symbols for process schematic. . . . . . . . . . . . . . . . . . . . . . . . 88 7
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
1
Introduction Heat transfer is a fundamental method in thermal process engineering.
1.1
Modular design of WL 110 series The WL 110 Heat Exchanger Service Unit series has a modular design.
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The heat exchangers are supplied with the required flow rates of cold water and hot water by the WL 110 Service Unit. The service unit can be combined with the following heat exchangers: • WL 110.01 Tubular Heat Exchanger • WL 110.02 Plate Heat Exchanger • WL 110.03 Shell and Tube Heat Exchanger • WL 110.04 Jacketed Vessel with Stirrer and Coil Together, the service unit and a connected heat exchanger make up a complete experimental setup. In the heat exchanger, thermal energy is transferred from the hot water to the cold water. This thermal energy is added in the service unit by heating the hot water. These experiment instructions provide a detailed description of the service unit and the four heat exchangers mentioned above. The WL 110 series is supplemented by the WL 110.20 Water Chiller.
1 Introduction
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
The WL 110.20 allows operation at high ambient and water temperatures. A separate operating manual is available for the WL 110.20 Water Chiller.
1.2
Objectives of unit, target group and learning content The WL 110 series is used to investigate and compare different types of heat exchanger. The water connection between a heat exchanger and the service unit is based on couplings. Reversing two couplings changes the direction of flow, allowing both parallel flow and counter flow operation. The various measured values are displayed digitally. At the same time, the measured values can be transferred directly to a PC via USB (PC is not included). The data acquisition program supplied is used to record, evaluate and plot the current measured values. A system diagram, the time response of the measured values and the current temperature progression along the heat exchanger are available.
The WL 110 series can be used both for training specialist staff and for engineering training in an academic setting.
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1 Introduction
WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
The learning objectives are: • Plotting temperature curves – in parallel flow mode – in counter flow mode • Calculating mean coefficients of heat transfer • Function and behaviour when operating different heat exchanger types
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• Comparing different heat exchanger types • Specifically for the WL 110.04 Jacketed Vessel with Stirrer and Coil: – Plotting temperature curves for heating with jacket and with tube coil modes. – Influence of stirrer
1 Introduction
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
1.3
Information for the teacher To operate the WL 110 series a suitable laboratory environment is required. Operation requires prior experience of experiments. Applications of the WL 110 series include: • Practical experiments Small groups of two to three students can perform experiments independently. The estimated time required to perform an experiment is around one hour. • Project work The WL 110 series is well suited for carrying out project work. Series of experiments can be used to determine the influence of changes on heat transfer. An individual experienced student can operate the equipment in this situation.
This teaching material is designed to assist you in preparing your lessons. You can put together sections of the material as information for your students and use them in their lessons. To support your teaching, we also provide these experimental instructions in PDF format on a CD.
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1 Introduction
WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
2
Safety
2.1
Intended Use The unit is to be used only for teaching purposes.
2.2
Structure of the Safety Instructions
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The signal words DANGER, WARNING or CAUTION indicate the probability and potential severity of injury. An additional symbol indicates the nature of the hazard or a required action.
Signal word
DANGER
Indicates a situation which, if not avoided, will result in death or serious injury.
WARNING
Indicates a situation which, if not avoided, may result in death or serious injury.
CAUTION
Indicates a situation which, if not avoided, may result in minor or moderately serious injury.
NOTICE
2 Safety
Explanation
Indicates a situation which may result in damage to equipment, or provides instructions on operation of the equipment.
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
Symbol
Explanation Electrical voltage
Hot surfaces
Hand injuries
Notice
Wear gloves
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2 Safety
WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
2.3
Safety instructions
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WARNING Electrical connections are exposed when the rear panel is open. Risk of electric shock. • Before opening the rear panel, disconnect the mains plug. • Work should only be performed by qualified electricians. • Protect electrical installations from moisture.
WARNING The hot water circuit can be operated at temperatures up to 70°C. Contact with hot water can cause scalding. • Avoid contact with hot water.
WARNING The hot water circuit can be operated at temperatures up to 70°C. Touching hot surfaces can cause burns. • Do not touch hot surfaces. • Put on appropriate protective gloves before touching hot couplings for hot water.
2 Safety
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
WARNING Reaching into the rotating stirrer on the WL 110.04 Jacketed Vessel with Stirrer and Coil can cause injury. • Do not reach into the rotating stirrer. • Before removing the cover, stop the stirrer and disconnect the plug from the connection socket.
NOTICE Frost damage is possible when storing the service unit and the heat exchangers. • Only store in a frost-free environment. • If there is a risk of frost or the unit will not be used for a long period, completely drain the water.
NOTICE The hot water pump is destroyed if operated without water. • Never operate the hot water pump without water.
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2 Safety
WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
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Unit description
3.1
Introduction to the WL 110 series
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The WL 110 Heat Exchanger with Service Unit series has a modular design. Fig. 3.1 shows the main modules of the WL 110 series.
WL 110
WL 110.01 WL 110.03
WL 110.04
WL 110.02 Fig. 3.1
The WL 110 series
3 Unit description
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
The heat exchangers are supplied with the required flow rates of cold water and hot water by the WL 110 Service Unit (referred to below as the service unit for short). The service unit can be combined with the following heat exchangers: • WL 110.01 Tubular Heat Exchanger • WL 110.02 Plate Heat Exchanger • WL 110.03 Shell and Tube Heat Exchanger • WL 110.04 Jacketed Vessel with Stirrer and Coil Together, the service unit and a connected heat exchanger make up a complete experimental setup. These experiment instructions provide a detailed description of the service unit and the four heat exchangers mentioned above.
The WL 110 series also includes the WL 110.20, the Water Chiller for WL 110. The service unit normally uses cold water from the local mains water supply with no additional cooling.
Fig. 3.2
WL 110.20, Water Chiller for WL 110
However, depending on the laboratory the available cold water may be too warm to provide useful experimental conditions (for recommended maximum cold water temperature, see Chapter 6.1, Page 79). In such cases, it is useful to supplement the service unit with the WL 110.20.
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3 Unit description
WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
A separate operating manual is available for the WL 110.20 Water Chiller for WL 110.
3.2
WL 110 Heat Exchanger with Supply Unit process schematic
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The process schematic for the WL 110 series is located on the service unit. This process schematic shows both the schematic structure of the service unit and the basic flow through the individual heat exchangers. These experiment instructions deal with each of these areas of the process schematic in turn.
Fig. 3.3, Page 12 shows the area of the process schematic that relates to the WL 110 service unit. The symbols used are explained in Chapter 6.5, Page 88. Further information about the design and function of the unit follows in Chapter 3.3, Page 13 and Chapter 3.4, Page 14 onwards.
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
FI 1
TI 1
TI 6
V1 Warmwasserkreislauf / Hot Water Circuit
Kaltwasserkreislauf / Cold Water Circuit
P LSL
1
B
W
TI 2
TI 5
H TIC
FI 2
TI 7 V3
Main components B Hot water tank H Hot water heater P Hot water pump W Interchangeable heat exchanger (Accessories) V1 Regulator valve for hot water V2 Regulator valve for cold water V3 Ball valve
Fig. 3.3
12
TI 3
TI 4
V2
Measurement and control engineering FI1 Hot water flow FI2 Cold water flow LSL1 Level switch TI1 Hot water feed temperature TI2 Hot water temperature, centre TI3 Hot water return temperature TI4 Cold water feed temperature TI5 Cold water temperature, centre TI6 Cold water return temperature TI7 Hot water temperature TIC Temperature controller
WL 110, process schematic
3 Unit description
WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
3.3
WL 110 Service Unit with Heat Exchanger 5
4
3
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6 2
7
8
9
10
1
11
1 2 3 4 5 6 Fig. 3.4
Base plate Connecting block Right housing half Tank cover Left housing section Control and display panel
7 8 9 10 11
Couplings Bolts Regulator valve for hot water (V1) Regulator valve for cold water (V2) USB connecting socket
WL 110, general view
3 Unit description
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
3.4
Unit function and components, WL 110 Service Unit with Heat Exchanger
3.4.1
Unit description and function The key function of the service unit is to provide the required cold and hot water flow rates for the connected heat exchanger. In the heat exchanger, thermal energy is transferred from the hot water to the cold water. The thermal energy transferred to the cold water is added in the service unit by heating the cooled hot water. In addition, the service unit displays the measured values and transfers them to a PC.
The selected heat exchanger is connected to the service unit using the four self-locking plug-in couplings for cold water and hot water (referred to below as couplings (7) for short). Fig. 3.5 shows both versions of the couplings. The couplings are different for cold water and hot water to make it easier to connect the heat exchangers. The cable emerging from the coupling provides the connection between the integrated temperature sensor and the service unit.
The service unit consists of two housing sections (3, 5), which are mounted on the base plate (1).
Fig. 3.5
14
Couplings (7)
3 Unit description
WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
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TI7
LSL1
The front of the left housing section is used as the control and display panel (6). Further information can be found in Chapter 3.4.2, Page 18 onwards. The left housing section contains the electrical installation with the hardware for the measurement and control engineering. The right housing section contains the hot water tank (B). The tank has a cover (4). Opening the cover allows water to be added. Sealing the cover can prevent leaks with strongly heated hot water. Fig. 3.6 shows the top view of the open hot water tank (B), with the electric hot water heater (H), the level switch (LSL1) and the immersion sleeve for the temperature sensor (TI7).
H Fig. 3.6
Hot water tank (B) 4
Fig. 3.7 shows a rear view of the right housing section (rear panel removed). The hot water tank (B), the hot water pump (P) and other components of the hot and cold water circuit can be seen, with the pipework and internal hoses.
The regulating valves V1 (9) and V2 (10) enable the required hot water and cold water flow rates to be set.
P Fig. 3.7
B
Right housing section (3), rear panel removed
3 Unit description
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
Hot water drainage
Cold water feed
Cold water return
Fig. 3.8
The service unit is connected to the water supply using hose couplings to the connection block (2). Details are shown in Fig. 3.8 and supplement the markings on the connection block itself. Fig. 3.9 shows the connection block (2) with coupled water connections. Opening the ball valve V3 drains the hot water tank (B).
Connection block (2) V3
Fig. 3.9
16
Connection block (2), with hoses
3 Unit description
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
Fig. 3.10
Service unit with WL 110.01 connected
Fig. 3.10 shows the service unit with the WL 110.01 Tubular Heat Exchanger connected. Details on connecting the different heat exchangers follow in Chapter 3.6, Page 25 to Chapter 3.9.
3 Unit description
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
3.4.2
Control and display panel The control and display panel (item 6 in Fig. 3.4, Page 13) is divided into various areas. The following illustration indicates these areas.
Heater controls
Displays for hot water circuit
Stirrer controls
Displays for cold water circuit
Pump controls
Connecting sockets for stirrer and temperature sensor Fig. 3.11
WL 110, Areas of control and display panel (6)
Details of the switching and control functions follow in Fig. 3.12, Page 19.
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3 Unit description
WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
28
27
26
25
24
29 23 30
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31 32 22 33 21
34
35 36
21 22 23 24 25 26 27 28 29 30
37
Cold water return temperature display (TI6) Cold water temperature display, centre (TI5) Cold water flow rate display (FI2) Hot water flow rate display (FI1) Hot water temperature display, centre (TI2) Hot water return temperature display (TI3) Hot water feed temperature display (TI1) Controller TIC7 for temperature TI7 Low water warning lamp (LSL1) Switch for heater (H)
Fig. 3.12
38
31 32 33 34 35 36 37 38
Cold water feed temperature display (TI4) Adjusting knob for stirrer speed Switch for Pump (P) Switch for stirrer Master switch with emergency stop function Connecting socket for stirrer Connecting socket for hot water temperature, centre Connecting socket for cold water temperature, centre
WL 110, Details of control and display panel (6)
3 Unit description
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
The hot water pump (P) is turned on and off using the switch (33). For experiments with the WL 110.04 Jacketed Vessel with Stirrer and Coil the electrical connection for the stirrer is provided by the connecting socket (36). The stirrer can be turned on and off using the switch (34). The speed of the stirrer is set using the adjusting knob (32) in the range 0...100%. The connecting sockets (37) and (38) are used to connect additional temperature sensors for the heat exchangers to the service unit.
The digital displays show the following measured variables (example of hot water circuit): • Hot water feed temperature T1 (27). • Hot water return temperature T3 (26). • Hot water temperature, centre T2 (25). · • Hot water flow rate V 1 (24).
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3 Unit description
WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
Controllers, operation and function: A hardware controller with display (28) is installed for the temperature control loop.
Actual value
Fig. 3.13 shows this controller TIC7 (28). It displays the actual value and setpoint. The desired setpoint can be set using the two arrow buttons.
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The controller is enabled using the switch (30).
The controller TIC7 (28) regulates the hot water temperature T7. It operates as a step controller. If the hot water temperature is too low, the heater (H) is activated. When the setpoint for T7 is reached, the heater is deactivated. Arrow buttons Fig. 3.13
Setpoint
Controller TIC7 (28)
The parameters for the TIC7 controller are preset during production (for values see Chapter 6.1, Page 79).
The warning lamp (29) indicates low water in the hot water tank (after tripping of the level switch LSL1). If the water is low, operation of the heater is interrupted. The aim is to prevent overheating and unacceptably high loads on the heater.
3 Unit description
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
3.5
Data acquisition program The data acquisition program supplied is used to record and evaluate the current measured values. The data acquisition program provides the following options for displaying the current measured values and calculated values: • System diagram • Time response for measured values • Current temperature curve, with display of calculated values • The available measured and calculated values are recorded at definable intervals in measured value files. These measured value files can be imported into spreadsheet programs (such as MS Excel®) and processed. The program’s Help function explains how to use the data acquisition program (see also Chapter 3.5.2, Page 24).
3.5.1
Installing the program The following is needed for the installation: • A fully operational PC, laptop or notebook with USB port (for minimum requirements see Chapter 6.1, Page 79 onwards). • G.U.N.T. CD-ROM.
Notice! All components necessary to install and run the program are contained on the CD-ROM supplied by G.U.N.T. along with the WL 110. No other items are necessary!
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3 Unit description
WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
After starting, the installation runs automatically. During the course of the installation, various program components are loaded onto the PC: • LabVIEW® runtime program for PC data acquisition. • Driver routines for the “LabJack®” USB converter.
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Installation routine Notice! The trainer must not be connected to the PC's USB port during the installation of the program. Only after the software has been installed can the trainer be connected. • Start the PC. • Insert the G.U.N.T. CD-ROM for the WL 110. • From the “Installer” folder, launch “Setup.exe” installation program.
the
• Follow the installation procedure on-screen. • Reboot the PC after the installation is finished.
3 Unit description
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
3.5.2
Operating the program The program for the WL 110 is selected and started using: Start / All Programs / G.U.N.T. / WL 110. When the software is run for the first time after installation, the language to be used for the program is requested (once only). Notice! The language selected can subsequently be changed at any time in the “Language” menu.
Fig. 3.14
Language selection
The system diagram for the WL 110 series then appears on the screen.
Various pull-down menus are provided for additional functions. For detailed instructions on use of the program refer to its Help function. This Help function is accessed by opening the „?“ pull-down menu and selecting „Help“.
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
3.6
WL 110.01 Tubular Heat Exchanger unit description
3.6.1
Layout and function
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The adjacent photo shows the WL 110.01 Tubular Heat Exchanger with base plate.
Fig. 3.15
WL 110.01, with base plate
Parallel flow
Counter flow
Fig. 3.16
WL 110.01, schematic
The tubular heat exchanger consists of two double tubes. In the double tubes, the transparent outer tube allows the stainless steel inner tube to be seen. Two separate areas are created, the tube area (inside the inner tube) and the shell (between the inner tube and the outer tube). Both the tube areas and the shells of the two double tubes are connected in series. The split into two double tubes reduces the overall length and enables temperature measurement for cold and hot water in the centre of the overall heat exchanger. Fig. 3.16 illustrates the flow. As determined by the two different coupling designs (7), hot water (red) flows through the tube area and cold water (shown in blue) through the shell. Cold and hot water flow along the inner tubes either in the same direction (parallel flow) or in opposite directions (counter flow).
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
3.6.2 TI2
Connection to the service unit TI5
Fig. 3.17 explains the individual steps required to connect the WL 110.01 to the service unit: 1. Secure the base plate of the tubular heat exchanger on the base plate (1) of the service unit using the star grip bolts. 2. Connect the plug for the hot water temperature, centre (TI2) measuring lead to the appropriate socket (item 37 in Fig. 3.12, Page 19). 3. Connect the plug for the cold water temperature, centre (TI5) measuring lead to the appropriate socket (item 38 in Fig. 3.12, Page 19). 4. Plug the couplings (7) for hot water into the corresponding connections on the tubular heat exchanger.
Fig. 3.17
26
Connection for WL 110.01
5. Plug the couplings (7) for cold water into the corresponding connections on the tubular heat exchanger. Ensure that the required flow is produced (parallel flow or counter flow).
3 Unit description
WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
3.6.3
General information for tubular heat exchanger Advantages of tubular heat exchangers: • Simple construction. • Connecting together several double tubes enables the heat transfer area to be varied by changing the number of double tubes.
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• Because it is possible to have large flow crosssections, the unit is also suitable for high viscosity fluids and for products containing solid pieces or fibres. • There is a hygienic advantage as the tube area is free of flow dead zones (important in the food industry, for example).
Tubular heat exchangers are used for applications including the food industry, with an example shown in the adjacent photo. It shows a module consisting of a large number of tubular heat exchangers connected in series. Here, the individual double tubes are arranged in several rows in a frame. The individual double tubes are connected using double tube bends.
Fig. 3.18
Module with several tubular heat exchangers
3 Unit description
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
3.7
WL 110.02 Plate Heat Exchanger unit description
3.7.1
Layout and function The adjacent photos show the WL 110.02 Plate Heat Exchanger.
Fig. 3.19
WL 110.02, with base plate
Fig. 3.19 shows the plate heat exchanger with the base plate. Fig. 3.20 shows an enlarged view of the plate heat exchanger screwed onto the base plate. This plate heat exchanger is essentially made up of six plates soldered together, which form two separate flow channels. The solder points seal the plates against one another.
Fig. 3.20
WL 110.02, enlarged
Fig. 3.21 illustrates the principle (illustrated with four plates). Cold (blue) and hot spaces (red) alternate in the arrangement. Openings in the plates allow the media to flow. The surface of the plates is not smooth but has a characteristic profile (embossing). This causes narrow flow cross-sections to be established in the spaces, in which significant turbulences occur. The turbulent flow facilitates efficient heat transfer and also has a self-cleaning effect. The wall thicknesses of the heat transfer areas are generally smaller than in tubular heat exchangers.
Fig. 3.21
28
WL 110.02, schematic
3 Unit description
WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
3.7.2
Connection to the service unit Fig. 3.22 explains the individual steps required to connect the WL 110.02 to the service unit:
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1. Secure the base plate of the plate heat exchanger on the base plate (1) of the service unit using the star grip bolts (8). 2. Plug the couplings (7) for hot water into the corresponding connections on the plate heat exchanger to give a flow in the direction of the arrow (see Fig. 3.23). 3. Plug the couplings (7) for cold water into the corresponding connections on the plate heat exchanger. Ensure that the required flow is produced (parallel flow or counter flow).
Fig. 3.22
Connection for WL 110.02
Fig. 3.23
WL 110.02, direction of flow
3 Unit description
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
3.7.3
General information for plate heat exchanger Advantages of plate heat exchangers: • Outstanding heat transfer. • Compact design. • Little space required relative to the heat transfer area.
Soldered plate heat exchangers are widespread in refrigeration engineering and building services.
Fig. 3.24
Sealed plate heat exchanger
The disadvantage of the soldered design is that it cannot be opened. If this kind of plate heat exchanger is blocked by deposits, residue or foreign bodies, it has to be replaced. The soldered design is a version developed from the widely used sealed plate heat exchangers. On the sealed design, the plate package, consisting of the plates and seals, is pressed together with clamp bolts. The adjacent figures show this kind of plate heat exchanger, as a photo and schematically. Key advantages of sealed plate heat exchangers:
Fig. 3.25
Plate with seal Platten
• Opening and cleaning possible. • Large heat transfer areas can be achieved (several 1000m² per unit). • The heat transfer area can be varied by changing the number of plates. Platten
Fig. 3.26
30
Sealed plate heat exchanger, schematic
3 Unit description
WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
Example applications of plate heat exchangers include: • Chemical plants • Petrochemicals • Food industry
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• HVAC (heating, ventilation and air conditioning)
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
3.8
WL 110.03 Shell & Tube Heat Exchanger unit description
3.8.1
Layout and function The adjacent photos show the WL110.03 Shell & Tube Heat Exchanger. Fig. 3.27 shows the shell and tube heat exchanger with the base plate. Fig. 3.28 shows an enlarged view.
Fig. 3.27
WL 110.03, with base plate
Fig. 3.28
WL 110.03, enlarged
Fig. 3.29
WL 110.03, tube bundle
The transparent shell allows the tube bundle to be seen. The tube bundle (shown in Fig. 3.29) is an assembly consisting of parallel tubes (seven tubes in this case). These seven tubes are soldered to the tube plates on both sides. This creates two separate areas, the tube area (inside the tubes) and the shell area (between the tubes and the outer shell). The shell area is divided by four baffle plates. They deflect the fluid in the shell area, thus improving the heat exchange. The flow in the shell area is essentially perpendicular to the tubes, i.e. the directions of flow cross (cross current flow). Fig. 3.30 illustrates the principle (illustrated with more than seven tubes). As determined by the two different coupling designs (7), hot water (red) flows through the tube area and cold water (shown in blue) through the shell area. Viewed axially, the flows can run in the same direction or in opposite directions. We therefore differentiate between cross parallel flow and cross counter flow.
Fig. 3.30
32
WL 110.03, schematic, cross counter flow
3 Unit description
WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
3.8.2
Connection to the service unit Fig. 3.31 explains the individual steps required to connect the WL 110.03 to the service unit:
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1. Secure the base plate of the shell and tube heat exchanger on the base plate (1) of the service unit using the star grip bolts (8). 2. Plug the couplings (7) for hot water into the corresponding connections on the shell and tube heat exchanger. Connect the hot water feed to the lower connection to support bleeding. 3. Plug the couplings (7) for cold water into the corresponding connections on the shell and tube heat exchanger. Ensure that the required flow is produced (cross parallel flow or cross counter flow).
Fig. 3.31
Connection for WL 110.03
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
3.8.3
General information for shell and tube heat exchanger Advantages of shell and tube heat exchangers: • Excellent heat transfer. • Compact design. • Comparatively little space required relative to the heat transfer area. • On many designs, the tube bundle can be removed from the shell for cleaning and maintenance.
Fig. 3.32 shows two tube bundles with tubes, baffle plates and tube plates. Shell and tube heat exchangers are widely used. The wide range of designs means that: • Wide permitted temperature ranges can be achieved, if almost unrestricted expansion of the tube bundle is possible. • Adaptations are possible for processes with a change of phase (evaporation, condensation). Fig. 3.32
Tube bundle
• Wide variety of material combinations can be used, depending on temperatures, pressures and fluid properties (corrosion etc.). Example applications of shell and tube heat exchangers include: • Chemical plants • Petrochemicals • Food industry • Power stations
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
3.9
WL 110.04 Jacketed Vessel with Stirrer and Coil unit description
3.9.1
Layout and function
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41
41
In many process engineering applications, several basic operations are combined, for example a fluid is heated by another fluid while being stirred, with a chemical reaction taking place at the same time. Such processes frequently take place in tanks. Depending on the specific perspective, the corresponding tanks can have various designations, including agitating vessels, chemical reactors or heated reaction tanks. The process can generally be carried out in batches or continuously.
Fig. 3.33
WL 110.04, with base plate
The WL 110.04 Jacketed Vessel with Stirrer and Coil is a model of this type of tank. It focuses on investigation of heat transfer. On the WL 110.04, heat transfer can occur through the wall of the tank. To allow this, the tank has a double jacket and the outer jacket is insulated. As an alternative to the double jacket, an internal heating coil can be used to transfer the heat. The installed stirrer improves the heat transfer.
Fig. 3.34
WL 110.04, cover
Fig. 3.35
WL 110.04, stirrer, propeller
3 Unit description
Fig. 3.33 shows the jacketed heat exchanger with base plate. After loosening the three knurled screws (41), the transparent cover can be removed. Fig. 3.34 shows the cover with the stirrer attached to it. Next to the stirrer is the immersion sleeve with temperature sensor for measuring the water temperature in the tank.
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
51
52
51
Fig. 3.35, Page 35 shows an enlarged view of the propeller of the stirrer. The top view of the open jacketed heat exchanger is shown in Fig. 3.36. As well as the heating coil (52) the flow breakers (51) attached to the tank wall can clearly be seen. They ensure a good stirring effect by preventing rotation of the liquid in the tank.
The tank is filled with cold water before an experiment. This cold water in the tank is then heated by hot water. The schematic view in Fig. 3.37 illustrates the experiment options: Fig. 3.36
WL 110.04, top view, cover removed
• Heating with hot water flowing through the heating jacket (a) • Heating with hot water flowing through the heating coil (b) As determined by the two different coupling designs (7), only hot water (red) can be connected to the jacket and heating coil. The WL 110.04 is mainly suitable for batch experiments.
Fig. 3.37
WL 110.04, flow, schematic
With practice, continuous operation can also be achieved. In this case, heated water flows out of the tank while fresh cold water is simultaneously fed in. However, the level in the tank can only be roughly adjusted when doing this. Therefore, reproducibility of the experiments is limited with continuous operation.
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
Fig. 3.38 explains the water connections for the WL 110.04. The cold water return (E) can be identified by the ball valve (V4). The tank can be drained by opening the ball valve V4. F
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The tank can be filled with cold water using the cold water feed (B).
V4 E
A A B C D E V4 F
B
C
D
Hot water heating jacket Cold water feed Hot water heating coil Hot water heating coil Cold water return Ball valve for draining Hot water heating jacket
Fig. 3.38
WL 110.04, water connections
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
3.9.2
Connection to the service unit The figures below explain the individual steps required to connect the WL 110.04 to the service unit: 1. Secure the base plate of the jacketed heat exchanger on the base plate (1) of the service unit using the star grip bolts (8). 2. Connect the plug for the stirrer cable to the connecting socket on the service unit (item 36 in Fig. 3.12, Page 19). 3. Connect the measuring lead for the water temperature (TI5) in the tank to the corresponding socket on the service unit (item 38 in Fig. 3.12, Page 19). 4. Plug the couplings (7) for cold water into the corresponding connections on the jacketed heat exchanger as shown in Fig. 3.38, Page 37. 5. Plug the couplings (7) for hot water into the corresponding connections on the jacketed heat exchanger, see also Fig. 3.38, Page 37.
Fig. 3.39
WL 110.04, attachment and electrical connection
Fig. 3.40, Page 39 shows the WL 110.04 connected for option (a) from Fig. 3.37, Page 36, heating with hot water flowing through the heating jacket. The hot water feed is connected to the lower connection to support bleeding. Fig. 3.41, Page 39 shows the WL 110.04 connected for option (b) from Fig. 3.37, Page 36, heating with hot water flowing through the heating coil.
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3 Unit description
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
Fig. 3.40
WL 110.04, operation with heating jacket
Fig. 3.41
WL 110.04, operation with heating coil
3.9.3
General information for jacketed heat exchanger The adjacent photo shows a jacketed heat exchanger for production. Advantages of jacketed heat exchangers: • Product temperature precisely adjustable with even temperature distribution. • Easy cleaning of the interior of the tank Jacketed heat exchangers are widely used for batch processes Example applications of jacketed heat exchangers include: • Chemical plants • Food industry
Fig. 3.42
Example of a jacketed heat exchanger
3 Unit description
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
3.10
Commissioning • Observe the safety instructions (see Chapter 2, Page 5). • Install the data acquisition program on the PC (see Chapter 3.5.1, Page 22 onwards). • Connect the service unit to the PC using the cable supplied (USB port, see item 11 in Fig. 3.4, Page 13). • Connect the service unit to the mains. • Connect the hoses to the connecting block (2) (see Fig. 3.8, Page 16). • Set the main switch (item 35 in Fig. 3.12, Page 19) to „1“. • Fill the hot water tank (B) with water (see Fig. 3.6, Page 15). • Connect one of the available heat exchangers (see also Chapter 3.6 to Chapter 3.9). • Open the cold water feed at the cold water mains. Fully open the regulator valve for cold water V2 (10). • Start the pump (P). If the pump does not start running, stop it immediately. Continue from section 3.11 on page 41 onwards. • Repair any leaks. • Turn on the heater (H). • Operate the experimental unit for a few minutes. During this time, practice using the data acquisition program. • Turn off the heater (H). • Stop the pump (P).
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
• Close the cold water feed at the cold water mains. Close the regulator valve V2 (10). • Set the main switch (item 35 in Fig. 3.12, Page 19) to „0“.
3.11
Hot water pump does not start?
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This section can be skipped if the hot water pump (P) starts up with no problems. Experience has shown that long stoppages make it more difficult to start up the hot water pump (P). It is possible that the pump will not start up at the first attempt. Starting the pump repeatedly does not resolve the problem. On the contrary, it can actually cause the electric fuse to trip. The following procedure is recommended:
1. Rinse the pump with cold water. Using the admission pressure of the cold water feed is recommended. Reversing the flow direction through the pump enables the cold water to be fed into the hot water tank (B). This circuit is created by connecting the couplings for the cold water feed and the hot water feed (see adjacent photo). Fig. 3.44, Page 42 shows a schematic view of this circuit, based on the process schematic in Fig. 3.3, Page 12. Fig. 3.43
Rinse the pump (P) with cold water, photo
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
FI 1
TI 1 V1
FI 2
P LSL
1
B B
TI 4
V2
Kaltwasser / Cold Water
H TIC Fig. 3.44
TI 7 Rinse the pump (P) with cold water, schematic circuit
Method: First ensure that the pump is not actuated (set the switch (33) in Fig. 3.12, Page 19 to "0" position). After connecting the couplings, completely open regulating valves V1 and V2. Open the cold water supply. As soon as water is flowing, allow the level in the tank (B) to rise by several litres. Then shut off the cold water supply and disconnect the couplings. Reconnect the original heat exchanger and continue with commissioning or the experiment. If the pump still does not start up, continue with 2. below.
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
2. Turn motor shaft with screwdriver. First ensure again that the pump is not actuated (set the switch (33) in Fig. 3.12, Page 19 to "0" position). Disconnect the WL 110 service unit from the mains electricity.
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The adjacent figure repeats the photo from Fig. 3.7, Page 15. It shows the pump in the right-hand half of the housing, with the rear panel removed. The front of the motor shaft has a slotted design and is intended to be accessible.
P
However, the carrying handle on the right-hand half of the housing next to the pump must be removed first. The motor shaft can then be turned with a screwdriver. The series of photos below illustrates the procedure.
Fig. 3.45
Right housing section, rear panel removed
Fig. 3.46
Remove carrying handle and turn motor shaft with screwdriver
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
3.12
Shutting down • Observe the safety instructions (see Chapter 2, Page 5). • Disconnect the service unit from the mains electricity supply. • Remove the USB cable from the USB port on the service unit. • Drain the hot water tank (B). This is done by opening the ball valve V3. • Open the regulator valve V2 (10). • Uncouple the cold water feed and return hoses. • Store the trainer covered, in a clean, dry and frost-free location.
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
4
Fundamental principles The basic principles set out in the following make no claim to completeness. For further theoretical explanations, refer to the specialist literature.
4.1
Heat transfer
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We differentiate between direct heat transfer and indirect heat transfer. An example of direct heat transfer is introducing hot steam into water to rapidly heat the water stored in a tank. The hot steam condenses in the liquid water and gives up its condensation heat to the content of the tank. Direct heat transfer can only be used if the heat carrier introduced does not interfere with the composition and concentration of the tank filling. In indirect heat transfer the heat is transferred from one fluid to another through a partition in a heat exchanger. The fluid flows on the two sides of the partition do not mix. In terms of the flow directions of the fluids on both sides of the partition, we differentiate between parallel flow, counter flow and cross flow. In other words, the fluids either flow in the same direction, in opposing directions or perpendicular to one another.
4 Fundamental principles
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
4.2
Indirect heat transfer
Hot fluid
Partition
Cold fluid
Th Tp,h Tp,c Tc
Δ Th ΔT
Δ Tp
Heat transfer at the partition can be sub-divided into three separate processes.
Δ Tc s
1. The hot fluid gives up heat to the partition. Travel
Fig. 4.1
Whilst the hot fluid is flowing along the partition, it is cooled and gives up heat to the partition. In turn, the heated partition gives up heat to the cold medium flowing along the other side of the partition. This heats the cold fluid.
Temperature curve at the partition
2. The partition conducts heat from the hot surface to the cold surface. 3. The partition gives up the heat to the cold fluid. The temperature curve at the partition is shown schematically in Fig. 4.1. Each of the three heat transfer processes is assigned a temperature difference ( Δ T h , Δ T p and Δ T c ). Note: Below, the variables for the hot side are indicated by the suffix h and those for the cold side with the suffix c. The suffix p represents the partition, while the suffixes in and out indicate the inlet and outlet. The efficiency of a heat exchanger is defined by the quality of the transfer of heat during the three heat transfer processes.
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4 Fundamental principles
WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
4.2.1
Heat transfer from fluid-partition The ability to transfer heat from one fluid to the partition or vice versa is described by the coefficient of heat transfer α . Q = α ⋅ A ⋅ ΔT ⋅ t
(4.1)
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The formula defines the amount of heat Q transferred in the time t. As well as the coefficient of heat transfer α and the partition area A, the temperature difference Δ T between the fluid and partition temperatures is a crucial factor in the heat transfer. In general the heat flow is of interest, i.e. the amount of heat per unit time that a heat exchanger transfers. The heat flow is specified using a power unit, e.g. kW or kJ/s. · For heat flow Q the equation is generally: · Q = α ⋅ A ⋅ ΔT
(4.2)
In the specific case of the hot side of the partition with hot fluid (suffix h) or the cold side with cold fluid (suffix c): · Q = αh ⋅ A ⋅ Δ Th where
Δ T h = T h – T p, h
(4.3) (4.4)
and · Q = αc ⋅ A ⋅ Δ Tc where
4 Fundamental principles
Δ T c = T p, c – T c
(4.5) (4.6)
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
4.2.2
Thermal conduction in the partition Within the partition the heat is transferred from the hot side to the cold side by thermal conduction. Here the following relationship applies:
λ · Q = --- ⋅ A ⋅ Δ T p s where
(4.7)
Δ T p = T p, h – T p, c
(4.8)
Here λ is the thermal conductivity of the partition material and s is the wall thickness of the partition.
4.2.3
Heat transmission Because the three heat flows are of equal magnitude in a steady state:
λ · Q = α h ⋅ A ⋅ Δ T h = --- ⋅ A ⋅ Δ T p = α c ⋅ A ⋅ Δ T c s
(4.9)
or, summarised at the mean coefficient of heat transfer km of the heat exchanger: 1 k m = ----------------------------1 1- s --------+ --- + -
αh
λ
(4.10)
αc
· With the heat flow Q · Q = k m ⋅ A m ⋅ Δ T lm
48
(4.11)
4 Fundamental principles
WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
Explanations of Formula (4.11): 1. As the temperatures along the partition are not constant, a mean temperature difference must be used for calculations. The temperature curve is non-linear, which means that rather than the arithmetic mean, the logarithmic mean temperature difference Δ T lm must be used.
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Δ T max – Δ T min Δ T lm = -----------------------------------Δ T max ln --------------- Δ T min
(4.12)
Δ T max and Δ T min relate to the temperature difference between the fluids, each at one point in the heat exchanger. Further information follows in Chapter 4.4, Page 53. 2. The surfaces on the cold and hot sides are not generally of equal size. For example, in a tubular heat exchanger, the inner surface of the tube is smaller than the outer surface, which means that in this case a mean area Am should be used. Ah – Ac A m = ------------------Ah ln ------ Ac
(4.13)
3. ln defines the natural logarithm for the base e = 2,71828. The mean coefficient of heat transfer km characterises the heat exchanger. It can be used to compare different heat exchangers with one another. There are guideline values for km for particular designs, enabling similar heat exchangers to be dimensioned.
4 Fundamental principles
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
When comparing coefficients of heat transfer from different sources, we recommend paying attention to the reference. In many cases, for heat exchange tubes they do not refer to the mean area Am but, due to the reduced calculation required, to either the inner or outer surface of the tube. However, all figures for the WL 110 series refer to Am to allow a fair comparison between the WL 110.02 plate heat exchanger on the one hand and the WL 110.01 tubular heat exchanger and WL 110.03 shell & tube heat exchanger on the other.
4.2.4
Analogy to fluid dynamics and electrics The inverse of the mean coefficient of heat transfer km is known as the heat transition coefficient. Rearranging Formula (4.10), Page 48 gives the heat transition coefficient: 1 s 1 1 ------ = ------ + --- + -----km αh λ αc
(4.14)
The term s / λ is known as the thermal conductivity resistance. The quotients 1/ α h and 1/ α c are also known as the heat transfer resistance. The heat transmission can thus be understood as series connection of the three individual resistances. As in fluid mechanics and electrics, the total resistance here is given by the sum of the individual resistance values.
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
4.3
Heat flow through the heat exchanger Hot fluid
· Q h,out
· Q h,in
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· Q = Transferred heat flow
· Q c,out · Q c,in Cold fluid
Fig. 4.2
Energy flow in heat exchanger (loss free)
Fig. 4.2 shows a schematic view of the energy and heat flow in a heat exchanger (losses are not indicated). · The transferred heat flow Q is calculated from the difference between the input and output heat · · flows ( Q in - Q out ). In an ideal heat exchanger without losses it is not relevant whether the hot or cold medium is used for the calculation (see Fig. 4.2). Generally the heat flow is determined from the · , the specific heat capacity c mass flow rate m p and the absolute temperature T : · · ⋅T Q = cp ⋅ m
4 Fundamental principles
(4.15)
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
The transferred heat flow is thus: · · · · ⋅ (T Q h = Q h,out – Q h,in = c p,h ⋅ m h h,out – T h,in )
(4.16)
for the hot fluid, and · · · · ⋅ (T Q c = Q c,out – Q c,in = c p,c ⋅ m c c,out – T c,in )
(4.17)
for the cold fluid. With no exchange of heat with the surroundings: · · · Q = –Qh = Qc
(4.18)
· If the heat flow figures differ, the mean value Q m is calculated. · · · · –Qh + Qc Qc – Qh · Q m = ------------------------------ = -------------------(4.19) 2 2
This enables the mean coefficient of heat transfer km for the heat exchanger to be calculated: · Qm k m = ------------------------A m ⋅ Δ T lm
(4.20)
· ⋅ (T · c p,c ⋅ m c c,out – T c,in ) – c p,h ⋅ m h ⋅ ( T h,out – T h,in ) k m = --------------------------------------------------------------------------------------------------------------------------------2 ⋅ A m ⋅ Δ T lm where and
52
· = ρ ⋅ V· h m h h · = ρ ⋅ V· m c c c
(4.21)
(4.22) (4.23)
4 Fundamental principles
WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
4.4
T h,in
Temperature curve
Hot fluid
T h,out
T c,in
T c,out
The adjacent two figures show example temperature curves for a tubular heat exchanger with parallel flow (Fig. 4.3) and counter flow (Fig. 4.4).
Cold fluid
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Cold
Travel x
The temperatures are normally exponential rather than linear.
Hot
Fig. 4.3
T h,in
If we plot the fluid temperatures in the heat exchanger in a combined graph against the travel x we obtain the temperature curve. The travel x runs along the heat transfer surface from the fluid inlet to the outlet.
This is clearly illustrated by the parallel flow example (see Fig. 4.3). The temperature difference is at its maximum when the fluids enter the heat exchanger (x =0) and at its minimum at the outlet. With the maximum temperature difference, a large heat flow can be transferred, i.e. the temperatures change quickly. As the temperature difference is reduced, the temperatures change more slowly.
Temperature curve for parallel flow
Hot fluid
T c,out
Cold fluid
T h,out T c,in
With parallel flow, the outlet temperature T c,out always remains lower than T h,out . By contrast, with counter flow the outlet temperature T c,out of the heated fluid can be higher than the outlet temperature T h,out of the cooled fluid.
Travel x
Hot Cold
Fig. 4.4
Temperature curve for counter flow
4 Fundamental principles
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
In Chapter 4.2.3, Page 48 onwards, the logarithmic mean temperature difference Δ T lm was used to calculate the temperature differences Δ T max and Δ T min . The following equations explain these temperature differences:
For parallel flow:
Δ T max = T h,in – T c,in
(4.24)
Δ T min = T h,out – T c,out
(4.25)
For counter flow, as shown by the example in Fig. 4.4, Page 53, the equations are:
Δ T max = T h,in – T c,out
(4.26)
Δ T min = T h,out – T c,in
(4.27)
At this point, it is important to mention that for counter flow there are also temperature curves in which the difference increases along the travel x.
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
5
Experiments
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The selection of experiments makes no claims of completeness but is intended to be used as a stimulus for your own experiments. The results shown are intended as a guide only. Depending on the construction of the individual components, experimental skills and environmental conditions, deviations may occur in the experiments. Nevertheless, the laws can be clearly demonstrated.
Note: In the experiments performed by G.U.N.T., the temperature of the incoming cold water T4 was around 15°C. Different temperatures T4 lead to changed measured values.
Note on the water quality of the water used: Cold water from the cold water mains is required for cooling. The hot water tank is normally filled with tap water. We recommend avoiding the use of water with a high water hardness (>5°dH). The lower the water hardness, the fewer deposits form in the experimental units.
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
This experiment chapter is split into two sections because the WL 110.04 Shell & Tube Heat Exchanger has a different design to the other three heat exchangers. As explained in Chapter 3.9, Page 35 onwards, the WL 110.04 is primarily intended for batch operation, in contrast to the other three heat exchangers. In addition, only the WL 110.04 has a stirrer. Therefore, there are also different experiment aims, methods of performing experiments, measured values and evaluations.
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5.1
Experiments with WL 110.01, WL 110.02 and WL 110.03 The experiments described here relate to the following three heat exchangers from the WL 110 series: • WL 110.01 Tubular Heat Exchanger • WL 110.02 Plate Heat Exchanger
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• WL 110.03 Shell and Tube Heat Exchanger
5.1.1
Experiment aims 1. Comparison of parallel flow and counter flow operation. Heat transmission and representation of temperature curves. 2. Investigation of heat transmission when changing the cold water and hot water flow rates. 3. Investigation of heat transmission when changing the hot water temperature. 4. Comparison of heat transmission for the different heat exchanger types.
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
5.1.2
Experiment series, general conditions The WL 110 series offers a wide range of options for carrying out experiments under widely varying conditions. A series of experiments is set out below, which can be used to investigate the experiment aims described in Chapter 5.1.1. This series of experiments includes experiments V1-01 to V10-03. The first number in this designation indicates the experiments, while the second number indicates the heat exchanger used.
Experiment
HE
Flow direction
Key:
· · V c ,V h
SP(T7 )
ltr/min
°C
HE:
Heat exchanger
V1-01
01
PF
0,7
70
PF:
Parallel flow
V2-01
01
PF
1,4
70
CF:
Counter flow
V3-01
01
PF
2,1
70
· Vc :
Cold water flow rate
V4-01
01
CF
1,4
70
· Vh :
Hot water flow rate
V5-01
01
CF
1,4
45
V6-01
01
CF
1,4
20
V7-02
02
PF
1,4
70
V8-02
02
CF
1,4
70
V9-03
03
PF
1,4
70
V10-03
03
CF
1,4
70
SP(T7 ): Setpoint for T7
Tab. 5.1
Parameters for experiments V1-01 to V10-03
Tab. 5.1 summarises the selected general conditions. Changed general conditions are shown with yellow shading. The designation SP(T7 ) indicates the setpoint (SP) for the temperature T7 of the hot water in the tank (B).
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5.1.3
Experimental setup
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Connected WL 110 Heat Exchanger Service Unit, commissioning carried out as described in Chapter 3.10, Page 40, in conjunction with the associated heat exchangers.
5.1.4
Performing the experiment The parameters to be set are set out in Tab. 5.1, Page 58. 1.
Observe the safety Chapter 2, Page 5).
instructions
(see
2.
Secure the selected heat exchanger on the base plate of the service unit as described in Chapter 3.6, Page 25 to Chapter 3.8 and connect.
3.
Set the main switch (item 35 in Fig. 3.12, Page 19) to „1“.
4.
Check the water level in the hot water tank (B) (see Fig. 3.6, Page 15). – If the hot water tank (B) is empty: Add water until the low level is reached (level switch LSL1 trips and the low water warning lamp (item 29 in Fig. 3.12, Page 19) goes out. Then add 0,5ltr of water with a beaker.
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
– If the hot water tank (B) is filled but with an unknown volume above the low level: Partially drain the hot water tank (B) (see Fig. 3.8, Page 16) until the low level is reached (level switch LSL1 trips and the low water warning lamp lights up). Then add 0,5ltr of water with a beaker. 5.
Start the PC. Start the data acquisition program.
6.
Open the cold water feed at the cold water mains.
7.
Open the regulator valve for cold water V2 (10).
8.
Open the regulator valve for hot water V1 (9).
9.
Start the pump (P).
10. If required, bleed the heat exchanger (Detach the heat exchanger base plate. Turn the heat exchanger with a through flow such that the air can escape upwards. Reattach the base plate). 11. Set the desired hot water setpoint SP(T7 ) on the TIC7 controller (28) (see also Fig. 3.13, Page 21). 12. If the temperature T7 of the hot water in the tank (B) is higher than the setpoint SP(T7 ): Cool the hot water circuit until T7 < SP(T7 ). · 13. Set the desired cold water flow rate V c using the regulator valve V2 (10). · 14. Set the desired hot water flow rate V h using the regulator valve V1 (9).
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
15. Turn on the heater (H). 16. Make settings for the measured value file. Start automatic measured value recording. 17. Observe the measured values. Wait until a steady state is reached, i.e.: – The water temperature T7 is no longer rising.
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– The parts in contact with the product have taken on the water temperatures. – The measured slightly.
values
only
change
· · – The heat flow values Q h and Q c are similar. 18. Save screenshots for the time response of the measured values and the current temperature curve in a file. Give the file a name that will allow you to identify the values in the measured value file later. 19. When the experiment is complete, first turn off the heater (H). 20. Then stop the pump (P). 21. Close the regulator valves V1 (9) and V2 (10). 22. If a further experiment is to be performed with a different heat exchanger, continue from step „2“.
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
23. If a further experiment is to be performed with the same heat exchanger, compare the current water temperature T7 with the new setpoint SP(T7 ). – If the hot water has a significantly higher temperature level, drain the hot water tank (B). Continue the experiment from step „2“. – If the hot water temperature level is similar or lower, continue the experiment from step „7“. 24. When the last experiment is complete, stop recording and save the measured value file. 25. Close the cold water feed at the cold water mains. 26. Set the main switch (35 in Fig. 3.12, Page 19) to “0”.
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5.1.5
Measured values The data acquisition program saves the measured values in measured value files. This measured value file contains a chronological sequence of measured data records. A measured data record is a snapshot of all the measured values at a given point in time.
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An interval of 1s was selected (representing the time between recording of two measured data records). A recording duration of 60min results in 61200 measured values (each measured data record contains 17 measured values). A tabular representation of the complete measured value file, with all measured data records, would be too extensive to set out at this point. Therefore, just a selection will be presented.
The table below supplements the data from Tab. 5.1, Page 58. In addition to the parameters for the experiment series, the following measured values and calculated values are set out here: • Hot water feed temperature T1 • Hot water return temperature T3 • Cold water feed temperature T4 • Cold water return temperature T6 • Mean coefficient of heat transfer km · • Mean heat flow Q m
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
Experiment
HE
· · Flow V c ,V h direction
SP(T7
T1
T3
T4
ltr/min
°C
°C
°C
°C
T6
km
· Qm
kW/(m²K)
kW
V1-01
01
PF
0,7
70
67,0
51,1
15,6
31,5
0,93
0,76
V2-01
01
PF
1,4
70
67,8
54,7
15,6
29,5
1,43
1,32
V3-01
01
PF
2,1
70
67,0
55,6
15,1
27,9
1,83
1,75
V4-01
01
CF
1,4
70
67,1
54,4
15,3
29,5
1,37
1,31
V5-01
01
CF
1,4
45
43,7
37,4
15,1
22,9
1,30
0,69
V6-01
01
CF
1,4
20
20,6
19,8
15,0
17,5
1,68
0,16
V7-02
02
PF
1,4
70
65,2
43,1
14,3
37,5
2,25
2,22
V8-02
02
CF
1,4
70
61,2
36,2
15,2
41,7
2,58
2,50
V9-03
03
PF
1,4
70
67,3
57,4
15,2
26,5
1,27
1,03
V10-03
03
CF
1,4
70
67,8
57,1
15,0
26,7
1,30
1,08
Tab. 5.2
Parameters for experiments V1-01 to V10-03, with measured and calculated values added
The hot water feed temperature T1 is included here so that the actual hot water temperature can be incorporated into the evaluation. The cold water feed temperature T4 helps in comparing the results from your own experiments. For experiment aim 3, the temperatures T3 and T6 are also required.
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5.1.6
Analysis, comments and evaluation Experiment aim 1, comparison of parallel flow and counter flow operation. Heat transmission and representation of temperature curves. The comparison is made using the example of the WL 110.02 Plate Heat Exchanger. Experiments V7-02 (parallel flow) and V8-02 (counter flow) are included.
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The following temperature curves are produced using the data acquisition program. Due to the limited number of measuring points, the links between the feed and return temperatures are shown as simplified straight lines here. In the figures, the designation of the water temperatures is enlarged.
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
T1 T3 T6 T4
Fig. 5.1
Temperature curve for experiment V7-02, WL 110.02, parallel flow
T1 T6
T3 T4
Fig. 5.2
66
Temperature curve for experiment V8-02, WL 110.02, counter flow
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
Comments and evaluation: • In counter flow mode, the heat transmission is better than in parallel flow mode. The values for the mean coefficient of heat transfer km are 2 2,58 kW⁄ ( m ⋅ K ) for counter flow and 2 2,25 kW⁄ ( m ⋅ K ) for parallel flow (see Tab. 5.2, Page 64).
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As defined by Formula (4.20), Page 52 the · mean heat flow rises as km increases Q m . The values in Tab. 5.2, Page 64 confirm this rise. • The temperature curve from experiment V8-02 in Fig. 5.2, Page 66 confirms the assertion from Chapter 4.4, Page 53. In experiment V8-02 the outlet temperature T 6 = T c,out of the heated fluid is higher than the outlet temperature T 3 = T h,out of the cooled fluid. This is not possible in parallel flow mode. For this reason alone, the heat transmission must be better for counter flow mode than for parallel flow mode.
Experiment aim 2, Investigation of heat transmission when changing the cold water and hot water flow rates. The comparison is made using the example of the WL 110.01 Tubular Heat Exchanger in parallel flow mode. The experiments V1-01, V2-01 and V3-01 are analysed. Fig. 5.3 shows the dependency of the mean coefficient of heat transfer km on the flow rates for · · cold water ( V c ) and hot water ( V h ).
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
km
2,0 1,8 1,6
· k m (V )
1,4 1,2 1,0 0,8 0,6 Fig. 5.3
0,8
1
1,2
1,4
1,6
1,8
2
· 2,2 V
Mean coefficient of heat transfer km as a function of cold water and hot water flow rates, for experiments V1-01, V2-01 and V3-01
Comments and evaluation: Tab. 5.2, Page 64 and Fig. 5.3, Page 68 show that the mean coefficient of heat transfer km · increases as the flow rates of cold water ( V c ) and · hot water ( V h ) rise. The cause of this increases is the greater turbulence caused by the increased flow rates on both sides of the „partition“ (in this case the inner tube). The greater turbulence produces higher coefficients of heat transfer α c and α h , and thus lower heat transfer resistances 1/ α h and 1/ α c . As defined by Formula (4.14), Page 50 this results in a lower heat transfer resistance 1/km and therefore greater heat transmission.
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Experiment aim 3, Investigation of heat transmission when changing the hot water temperature.
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The comparison is made using the example of the WL 110.01 Tubular Heat Exchanger in counter flow mode. The experiments V4-01, V5-01 and V6-01 are analysed. The table below supplements the data from Tab. 5.2, Page 64. In addition to the measured values, the following calculated values are also set out: • Δ T max as defined in Formula (4.26), Page 54, here T3 -T4 • Δ T min as defined in Formula (4.27), Page 54, here T1 -T6 • Δ T lm as defined in Formula (4.12), Page 49. · • Mean heat flow Q m , from measured value file. Experiment SP(T7 ) °C
T1
T3
T4
T6
Δ T max
Δ T min
Δ T lm
· Qm
°C
°C
°C
°C
°C
°C
°C
kW
V4-01
70
67,1
54,4
15,3
29,5
39,1
37,6
38,3
1,31
V5-01
45
43,7
37,4
15,1
22,9
22,3
20,8
21,5
0,69
V6-01
20
20,6
19,8
15,0
17,5
4,8
3,1
3,9
0,16
Tab. 5.3
Parameters and measured values for experiments V4-01 to V6-01, calculated values for experiment aim 3 added
Fig. 5.4 shows the dependency of the mean heat · flow Q m on the logarithmic mean temperature difference Δ T lm graphically.
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
· Qm
1,4 1,2 1,0
· Q m (ΔT lm )
0,8 0,6 0,4 0,2 0,0 0 Fig. 5.4
5
10
15
20
25
· Mean heat flow Q m as a function of Δ T lm for experiments V4-01, V5-01 and V6-01
30
35
40
Δ T lm
Comments and evaluation: · Fig. 5.4 shows that the mean heat flow Q m increases as the temperature T4 (hot water feed) or Δ T lm rises. This increase is approximately linear. Formula (5.1) repeats Formula (4.20), Page 52, · rearranged for Q m : · Q m = k m ⋅ A m ⋅ Δ T lm
(5.1)
· The equation states that Q m changes proportionally to Δ T lm if km and Am are constant. Am is constant here as these three experiments were performed with the same heat exchanger km should actually also be largely constant. This is generally the case in experiment V4-01 with 2 km =1,37 and in V5-01 with km =1,30 kW⁄ ( m ⋅ K ) . However, in experiment V6-01 2 km =1,68 kW⁄ ( m ⋅ K ) differs significantly.
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A possible explanation for this difference is that in experiment V6-01 there is a low temperature difference between the cold and hot water. This increases the impact of any measuring inaccuracy.
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Experiment aim 4, Comparison of heat transmission for the different heat exchanger types. Comments and evaluation: The comparison of the average coefficients of heat transfer km is important. Analysing the mean · heat flows Q m is not useful here as the three heat exchangers have different heat transfer areas (see also Chapter 6.2, Page 81 onwards). An evaluation can be carried out using Tab. 5.2, Page 64. This is done by comparing those experFlow km direction iments that only differ in terms of the heat kW/(m²K) exchangers, with identical flow rates and the PF 1,43 same setpoint SP(T7 ) for hot water. Tab. 5.4 shows the corresponding extract from Tab. 5.2: CF 1,37
Experiment
HE
V2-01
01
V4-01
01
V7-02
02
PF
2,25
V8-02
02
CF
2,58
V9-03
03
PF
1,27
V10-03
03
CF
1,30
Tab. 5.4
Heat transmission of heat exchanger types
5 Experiments
• For parallel flow mode (shown shaded in blue) these are the experiments V2-01, V7-02 and V9-03. The values for the average coefficient of heat transfer km rise in the following order of the heat exchangers: WL 110.03, WL 110.01 and WL 110.02.
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
• For counter flow mode the experiments V401, V8-02 and V10-03 are compared. Once again, the values for the mean coefficient of heat transfer km rise in the order of heat exchangers WL 110.03, WL 110.01 and WL 110.02.
The best coefficient of heat transfer by some distance is thus obtained using the WL 110.02 Plate Heat Exchanger. It is notable that the best heat transmission in experiment V8-02 is linked to the highest difference between the hot water setpoint SP(T7 ) = 70°C and the hot water feed temperature T1 = 61,2°C (see Tab. 5.2, Page 64). The explanation for this is that the mean heat flow · Q m = 2,50kW is also at a maximum in this experiment. The remaining difference from the installed electric heating power of 3kW (see also Chapter 6.1, Page 79) corresponds to the heat losses from the hot water outside the heat exchanger (hoses, service unit etc.).
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5.2
Experiments with WL 110.04
5.2.1
Experiment aim Recording the measured value time response.
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5.2.2
General conditions The adjacent figure repeats Fig. 3.37, Page 36. The experiment is performed as described in a), i.e. a defined volume of cold water inside the tank is heated by the hot water flowing through the heating jacket in batch mode. The volume of cold water should: • fill the tank well, so that a large proportion of the heating jacket area is covered.
Fig. 5.5
WL 110.04, flow, schematic
• such that no water spills over during the experiment when stirring. This defined volume of cold water can be adjusted by filling the tank using the cold water feed (item B in Fig. 3.38, Page 37) on the service unit. However, we recommend adding the cold water with a separate beaker and funnel (see Fig. 5.6). It is useful to measure the water into the beaker in advance. This results in greater accuracy and reproducibility for repeat experiments.
Fig. 5.6
Filling the WL 110.04
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
A good fill is obtained with 1200g of water. The flow breakers (see also Fig. 3.36, Page 36) are then completely covered.
The other general conditions are selected to quickly achieve significant heating: • Hot water setpoint SP(T7 )=70°C. · • Hot water flow rate V h = 2,1ltr/min. • Operate the stirrer at maximum speed.
5.2.3
Experimental setup Connected WL 110 Heat Exchanger Service Unit, commissioning carried out as described in Chapter 3.10, Page 40, in conjunction with the WL 110.04 Jacketed Vessel with Stirrer and Coil.
Fig. 5.7
74
Service unit with WL 110.04
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
5.2.4
Performing the experiment
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The parameters to be set are set out in Chapter 5.2.2, Page 73. 1.
Observe the safety Chapter 2, Page 5).
instructions
(see
2.
Secure the WL 110.04 Jacketed Vessel with Stirrer and Coil on the base plate of the service unit as described in Chapter 3.9, Page 35 onwards and connect (see Fig. 5.7, Page 74).
3.
Set the main switch (item 35 in Fig. 3.12, Page 19) to „1“.
4.
Check the water level in the hot water tank (B) (see Fig. 3.6, Page 15). – If the hot water tank (B) is empty: Add water until the low level is reached (level switch LSL1 trips and the low water warning lamp (item 29 in Fig. 3.12, Page 19) goes out. Then add 0,5ltr of water with a beaker. – If the hot water tank (B) is filled but with an unknown volume above the low level: Partially drain the hot water tank (B) (see Fig. 3.8, Page 16) until the low level is reached (level switch LSL1 trips and the low water warning lamp lights up). Then add 0,5ltr of water with a beaker.
5 Experiments
5.
Start the PC. Start the data acquisition program.
6.
Fully open the regulator valve for hot water V1 (9).
7.
Start the pump (P).
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
8.
Set the desired hot water setpoint SP(T7 ) on the TIC7 controller (28) (see also Fig. 3.13, Page 21).
9.
Turn on the heater (H).
10. Measure 1200g of cold water into a separate beaker. 11. Wait until the hot water temperature T7 has reached the setpoint SP(T7 ). · 12. Set the desired hot water flow rate V h using the regulator valve V1 (9). 13. Make settings for the measured value file. Start automatic measured value recording. 14. Add the content of the beaker to the WL 110.04 (see also Fig. 5.6, Page 73). 15. Start the stirrer. Set the maximum speed. 16. Wait until the temperature T5 of the water in the WL 110.04 has approximately reached the hot water temperature. 17. Save a screenshot for the time response of the measured values in a file. Give the file a name that will allow you to identify the values in the measured value file later. 18. When the experiment is complete, first turn off the heater (H). 19. Then stop the pump (P). 20. Close the regulator valve V1 (9). 21. Stop the stirrer.
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22. Stop recording and save the measured value file. 23. Set the main switch (35 in Fig. 3.12, Page 19) to “0”.
5.2.5
Measured values, time response
All rights reserved, G.U.N.T. Gerätebau, Barsbüttel, Germany 11/2011
The following measured value time response was produced using the data acquisition program.
Fig. 5.8
Measured value time response for WL 110.04, batch mode, with heating jacket
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
5.2.6
Analysis, comments and evaluation Explanation of measured value time response (see Fig. 5.8, Page 77): · The hot water flow rate V h is shown in green · here. V h fluctuates around 2,1ltr/min. Before adding the cold water the temperatures T1 (hot water feed) and T3 (hot water return) are around 70°C. When the cold water is added, the hot water return temperature T3 falls because the hot wall of the heating jacket quickly gives up heat to the cold water (see adjacent extract from Fig. 5.8, Page 77). The temperature T5 of the water in the tank is slightly above 30°C directly after adding the water at 16:08. Initially, the tank content is heated quickly due to the large temperature difference. As the temperature difference between the hot water and the tank content is reduced, the temperature T5 rises increasingly slowly. It eventually approaches the hot water temperature asymptotically.
Fig. 5.9
Extract from measured value time response for WL 110.04
The temperature difference between the hot water feed and return reduces as the heat transmission decreases. Heating the tank content from 30°C to 65°C takes around 10min. Similar experiments can be used to simulate real processes on a small scale, to obtain information about the design of larger actual heat exchangers.
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6
Appendix
6.1
Technical data for WL 110, Heat Exchanger Service Unit Dimensions: Length x Width x Height: Weight:
Approx. 1000 x 700 x 600 mm Approx. 52 kg
All rights reserved, G.U.N.T. Gerätebau, Barsbüttel, Germany 11/2011
Connection values: Electrical supply 230 V / 50 Rated consumption (power) Approx. 3,2 Optional alternatives, see rating plate Cold water, required admission pressure: Approx. 3 Cold water, temperature: recommended T < 20 Hot water tank, with heater: Nominal volume: Heating power: Hot water pump: Type: Maximum flow rate: Maximum head: Temperature measurement: Type: Measuring range:
Hz kW bar g °C
Approx. 10 ltr Approx. 3 kW
Centrifugal pump 7 ltr/min 25 mFS
Pt100 0...100 °C
Hot and cold water flow rate measurement: Type: Paddle wheel flow meter Measuring range: 20...250 ltr/h
6 Appendix
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
Temperature controller: Hardware controller with display, used as two point controller. Default settings: Hysteresis: 0,2 °C Setpoint limited to max.: 70 °C Data acquisition:
USB communication. Program environment: LAB-View Runtime System requirements: • PC with Pentium IV processor, 1GHz, or better. • Min. 1024 MB RAM • Min. 1 GB available hard disk space. • 1 x USB port • Graphics card resolution min. 1024 x 768 pixels, TrueColor • Windows XP / Vista
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
6.2
Technical data for accessories (heat exchangers) Various heat exchangers for connection to WL 110. Hot and cold water supply from WL 110.
6.2.1
WL 110.01 Tubular Heat Exchanger Parallel flow and counter flow operation possible.
All rights reserved, G.U.N.T. Gerätebau, Barsbüttel, Germany 11/2011
Dimensions: Length x Width x Height: Weight:
Approx. 480 x 230 x 150 mm Approx. 4 kg
Tubular heat exchanger, essentially consisting of two double tubes. Tubular heat exchanger, geometry and material: Effective tube length, Approx. 360 Transparent outer tube material: PMMA Outer tube wall thickness: 2 Outer tube internal diameter: 16 Inner tube material: Stainless steel Inner tube wall thickness: 1 Inner tube internal diameter: 10 Mean logarithmic heat transfer Approx. 0,025 area, total, Am : Temperature measurement: Type: Measuring range:
6 Appendix
mm each mm mm mm mm m²
Pt100 0...100 °C
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
6.2.2
WL 110.02 Plate Heat Exchanger Parallel flow and counter flow operation possible. Dimensions: Length x Width x Height: Weight:
Approx. 400 x 230 x 85 mm Approx. 3 kg
Plate heat exchanger, geometry and material: Number of soldered plates: Plate material: Heat transfer area, total, A:
82
6 Stainless steel Approx. 0,048 m²
6 Appendix
WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
6.2.3
WL 110.03 Shell and Tube Heat Exchanger Cross parallel flow and cross counter flow operation possible. Dimensions: Length x Width x Height: Weight:
Approx. 400 x 230 x 110 mm Approx. 3 kg
All rights reserved, G.U.N.T. Gerätebau, Barsbüttel, Germany 11/2011
Shell and tube heat exchanger, geometry and material: Shell material: PMMA Shell wall thickness: 3 Shell internal diameter: 44 Tube bundle consisting of 7 tubes. Tube material: Stainless steel Effective tube length: 184 Tube wall thickness: 1 Tube internal diameter: 4 Baffle plate material: Stainless steel Number of baffle plates: 4 Baffle plate wall thickness: 1 Mean logarithmic heat transfer Approx. 0,02 area, total, Am :
6 Appendix
mm mm
mm mm mm
mm m²
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
6.2.4
WL 110.04 Jacketed Vessel with Stirrer and Coil Dimensions: Length x Width x Height: Weight:
Approx. 400 x 230 x 400 mm Approx. 8 kg
Jacketed heat exchanger Insulated jacketed tank with pipe coil and stirrer. Type of stirrer: Propeller, with three blades Stirrer speed range: Approx. 20...330 rpm Jacketed heat exchanger, geometry and material: Nominal tank volume: Approx. 1,2 Jacketed tank and pipe coil material: Stainless steel Inner jacket wall thickness: 2,5 Inner jacket internal diameter: 103 Outer jacket internal diameter: 127 Tank base wall thickness: 4 Transparent cover material: PMMA Pipe coil wall thickness: 1 Pipe coil internal diameter: 6 Pipe coil stretched pipe length: 2300 Mean logarithmic heat transfer Approx. 0,05 area, pipe coil, Am : Mean logarithmic heat transfer area, inner jacket, depending on level, at nominal volume Am : Approx. 0,05 Temperature measurement: Type: Measuring range:
84
ltr mm mm mm mm mm mm mm m² m²
Pt100 0...100 °C
6 Appendix
WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
List of abbreviations Abbreviation
Meaning
PF
Parallel flow
CF
Counter flow
SP
Setpoint
SP(T7 )
Setpoint for temperature measuring point T7
HE
Heat exchanger
All rights reserved, G.U.N.T. Gerätebau, Barsbüttel, Germany 11/2011
6.3
6 Appendix
85
WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
6.4
86
List of key symbols and units used Symbol
Mathematical/physical variable
Unit
A
Heat transfer area
m²
Am
Mean heat transfer area
m²
cp
Specific heat capacity
kJ ⁄ ( kg ⋅ K )
km
Mean coefficient of heat transfer
kW ⁄ ( m ⋅ K )
m
Mass
g, kg
· m
Flow rate
g/s
Q · Q
Amount of heat
J, kJ
Heat flow, general
W, kW
s
Wall thickness
mm, m
t
Time
min, s
T
Temperature
°C, K
Δ T lm
Logarithmic mean temperature difference
K
V
Volume
ltr, m³
· V
Flow rate
ltr/min
x
Travel, travel length
mm, m
α
Coefficient of heat transfer
kW ⁄ ( m ⋅ K )
λ
Thermal conductivity
kW ⁄ ( m ⋅ K )
ρ
Density
kg/ltr
2
2
6 Appendix
All rights reserved, G.U.N.T. Gerätebau, Barsbüttel, Germany 11/2011
WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
6 Appendix
Suffix
Explanation
c
Cold
h
Hot
in
Inlet
lm
Logarithmic mean
m
Mean
max
Maximum
min
Minimum
out
Outlet
p
Partition
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WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
6.5
List of symbols for process schematic Symbol
Name
Apparatus and equipment Centrifugal pump Tank, general Heating or cooling Fittings Regulator valve Ball valve, manually operated General symbols, measuring points Flow line Function line Measuring point with remote evaluation Controller Coupling
88
6 Appendix
WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
7
Index
A Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 Actual value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Amount of heat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 B
All rights reserved, G.U.N.T. Gerätebau, Barsbüttel, Germany 11/2011
Baffle plate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Base plate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Batch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 C Coefficient of heat transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 Continuous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Control and display panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Counter flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25, 45, 65 Coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Cross counter flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Cross flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32, 45 Cross parallel flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 D Data acquisition program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Direct heat transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 E Embossing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 Experiment series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 F Flow breaker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Flow direction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 G General view . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
7 Index
89
WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
H Heat exchanger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Heat flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 Heat transfer resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 Heat transition coefficient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 Heat transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50, 67, 71 Heating coil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35, 36 Help function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Hot water heater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Hot water pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 I Indirect heat transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 Inner tube . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 J Jacketed heat exchanger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 L Level switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Logarithmic mean temperature difference . . . . . . . . . . . . . . . . . . . 49, 54 M Mean coefficient of heat transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . 48, 68 Measured data record . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 Measured value file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22, 63 Modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 O Outer jacket . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Outer shell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Outer tube . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 P Parallel flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25, 45, 65 Partition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 Plate heat exchanger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28, 65, 72 Plate package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 Process schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
90
7 Index
WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
S
All rights reserved, G.U.N.T. Gerätebau, Barsbüttel, Germany 11/2011
Sealed plate heat exchanger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 Series connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 Service unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Setpoint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Shell and tube heat exchanger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Shell area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25, 32 Stirrer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Symbol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 System diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 T Technical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 Temperature curve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53, 66 Thermal conduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 Thermal conductivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 Thermal conductivity resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 Tube area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25, 32 Tube bundle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32, 34 Tube plate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Tubular heat exchanger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25, 67, 69 W Wall thickness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 Water Chiller for WL 110 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Water connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Water quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 WL 110 series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
7 Index
91
WL 110-SERIES HEAT EXCHANGER WITH SERVICE UNIT
92
7 Index
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