IMCLONE LABORATORY RENOVATION PROJECT 2007 ASHRAE STUDENT DESIGN COMPETITION HVAC SYSTEM SELECTION New York, New York
KANSAS STATE UNIVERSITY
Department of Architectural Engineering and Construction Science 240 Seaton Hall Manhattan, KS 66506
PREPARED BY: Kevin Chow 4th Year Architectural Engineering Anticipated Graduation: May 2008
[email protected] Present Address Permanent Address 1737 Laramie St. 2725 Cogan Drive Manhattan, KS 66502 Indep., MO 64055 (816) 686-9028 (816) 373-2107
Jeremy Fowler 4th Year Architectural Engineering Anticipated Graduation: May 2008
[email protected] Present Address Permanent Address 1832 Claflin Apt. 10 1832 Claflin Apt. 10 Manhattan, KS 66502 Manhattan, KS 66502 (970) 389-7238 (970) 389-7238
Brendan Gleason 5th Year Architectural Engineering Anticipated Graduation: May 2007
[email protected] Present Address Permanent Address 815 N 10th St. 1 Cedar Drive Manhattan, KS 66502 Halstead, KS 67056 (316) 259-7453 (316) 835-3294
Brandon Damas 5th Year Architectural Engineering Anticipated Graduation: May 2007
[email protected] Present Address Permanent Address 2039 College View Rd. 14395 W. 142nd St. Manhattan, KS 66502 Olathe, KS 66062 (913) 481-2913 (913) 481-2913
Brandon Frey 4th Year Architectural Engineering Anticipated Graduation: May 2008
[email protected] Present Address Permanent Address 1114 Vattier St. Apt. 8 218 N. Racehorse Manhattan, KS 66502 Wichita, KS 67235 (316) 371-6127 (316) 371-6127
Ben Willey 5th Year Architectural Engineering Anticipated Graduation: December 2007
[email protected] Present Address Permanent Address 801 Osage 8713 W. 19th St. Manhattan, KS 66502 Wichita, KS 67212 (316) 393-8299 (316) 721-0354
KANSAS STATE UNIVERSITY ASHRAE System Selection TABLE OF CONTENTS Section Page List of Figures ............................................................................................................................................................................. ii List of Tables............................................................................................................................................................................... ii 1.0 Executive Summary ............................................................................................................................................................. 1 2.0 Introduction.......................................................................................................................................................................... 1 2.1 Design Criteria .............................................................................................................................................................. 1 2.1.1 Performance Requirements.............................................................................................................................. 2 2.1.2 Capacity Requirements...................................................................................................................................... 2 2.1.3 Spatial Requirements ......................................................................................................................................... 2 2.1.4 First Cost............................................................................................................................................................. 2 2.1.5 Operating Cost ................................................................................................................................................... 2 2.1.6 Reliability............................................................................................................................................................. 2 2.1.7 Flexibility ............................................................................................................................................................. 3 2.1.8 Maintainability .................................................................................................................................................... 3 2.1.9 Sustainability ....................................................................................................................................................... 3 2.2 Major Design Goals ..................................................................................................................................................... 4 2.2.1 Low 20 Year Life Cycle Cost ........................................................................................................................... 4 2.2.2 Low Environmental Impact............................................................................................................................. 4 2.2.3 Comfort and Health .......................................................................................................................................... 5 2.2.4 Creative High Performance Green Design.................................................................................................... 5 2.2.5 Synergy with Architecture ................................................................................................................................ 5 2.3 Building Description .................................................................................................................................................... 5 2.4 Design Parameters........................................................................................................................................................ 6 3.0 Basic System Concepts........................................................................................................................................................ 8 3.1 System Zoning .............................................................................................................................................................. 8 3.2 Pressurization ................................................................................................................................................................ 8 3.3 Filters.............................................................................................................................................................................. 9 4.0 Major System Components ................................................................................................................................................ 9 4.1 Boilers............................................................................................................................................................................. 9 4.2 Closed-Loop Evaporative Coolers .......................................................................................................................... 10 4.3 Pumps........................................................................................................................................................................... 10 4.4 Heat Recovery............................................................................................................................................................. 10 4.5 Exhaust System........................................................................................................................................................... 11 5.0 System Descriptions and Schematics.............................................................................................................................. 12 5.1 Option 1 – Open-Loop Geothermal Heat Pumps ............................................................................................... 12 5.2 Option 2 – Water Source Heat Pumps ................................................................................................................... 16 5.3 Option 3 – AHU with Terminal Reheat................................................................................................................. 18 5.4 Baseline System........................................................................................................................................................... 22 6.0 System Comparisons ......................................................................................................................................................... 24 6.1 Performance Requirements ...................................................................................................................................... 24 6.2 Capacity Requirements .............................................................................................................................................. 24
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KANSAS STATE UNIVERSITY ASHRAE System Selection 6.3 Spatial Requirements.................................................................................................................................................. 24 6.4 First Cost...................................................................................................................................................................... 24 6.5 Operating Cost............................................................................................................................................................ 24 6.6 Reliability...................................................................................................................................................................... 25 6.7 Flexibility...................................................................................................................................................................... 25 6.8 Maintainability............................................................................................................................................................. 25 6.9 Sustainability................................................................................................................................................................ 25 6.10 Summary .................................................................................................................................................................... 26 7.0 Design Goals ...................................................................................................................................................................... 28 8.0 Final System Selection and Recommendations............................................................................................................. 29 9.0 Appendices.......................................................................................................................................................................... 30 9.1 Appendix A – Assumptions ..................................................................................................................................... 30 9.2 Appendix B – Initial Cost Spreadsheets ................................................................................................................. 31 9.3 Appendix C – Operating Cost.................................................................................................................................. 34 9.4 Appendix D – 20 Year Live Cycle Cost Analysis.................................................................................................. 35 9.5 Appendix E – Sample Calculation of Lab Space Where Internal Load Governs............................................ 38 9.6 Appendix F – Psychrometric Chart of Lab Space ................................................................................................ 40 10.0 References ......................................................................................................................................................................... 41 List of Figures Page Figure 2.1-Existing Building Site in Relation to City Grid .................................................................................................. 6 Figure 3.1- Total Building Pressurization Detail ................................................................................................................... 9 Figure 4.1- Heat Pipe Heat Exchanger Detail ..................................................................................................................... 11 Figure 5.1- Geothermal Heat Pump Detail.......................................................................................................................... 13 Figure 5.2- Geothermal Heat Pump One Lines .................................................................................................................. 15 Figure 5.3- Water Source Heat Pump One Lines ............................................................................................................... 17 Figure 5.4- Reverse Return Piping Example........................................................................................................................ 18 Figure 5.5- Direct Return Piping Example .......................................................................................................................... 18 Figure 5.6- ImClone Thermal Ice Sculpture ........................................................................................................................ 19 Figure 5.7- Typical Building Electrical Demand Profile .................................................................................................... 19 Figure 5.8- AHU with Terminal Reheat One Lines............................................................................................................ 21 Figure 5.9- Baseline One Lines .............................................................................................................................................. 23 List of Tables Page Table 2.1-Outdoor Design Conditions ................................................................................................................................... 6 Table 2.2-Internal Loads ........................................................................................................................................................... 7 Table 2.3-Utility Rates ............................................................................................................................................................... 7 Table 6.1- Design Criteria Matrix .......................................................................................................................................... 26 Table 6.2- System Comparison Rating System .................................................................................................................... 27 Table 7.1-Major Design Goals Matrix .................................................................................................................................. 28
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KANSAS STATE UNIVERSITY ASHRAE System Selection 1.0 EXECUTIVE SUMMARY The objective of this proposal is to present the most favorable HVAC system for the ImClone Lab Building located in New York City, New York. To determine this, the design team first evaluated the building and became familiarized with the design criteria and goals. The building was then zoned by grouping rooms with similar internal/external loads and occupancies. After zoning, it was evident the office areas and lab areas needed to be separated because of the stringent pressurization and ventilation requirements in the lab spaces. The next step was to calculate the building loads using Trane Trace 700. Even though many different systems were initially considered, only three appeared to be worthy of further analysis. Geothermal heat pumps, water source heat pumps, and AHUs with terminal reheat were chosen to be evaluated. After determining the system options, the design team further analyzed additional components to improve the overall efficiency of the system. Some components include types of heat recovery equipment, heat pumps, boilers, chillers, variable frequency drives, thermal storage, etc. Additionally, nontraditional and creative ideas were considered in each design, such as, an ice sculpture for thermal ice storage, a fountain to prevent thermal pollution, and a heat pump compressor lockout (heat pump economizer) control sequence to save energy. Trade-offs between major design criteria were evaluated to determine the parts and pieces of each system. Once the components for each system option were determined, a detailed Trace 700 energy analysis was used to determine the total energy consumption for each option. Using the energy consumption calculated, operating costs were developed for the system options. Next, the first cost was calculated. These two cost breakdowns were used in conjunction with the other design criteria to obtain a final system selection. The final selection process utilized a system comparison and major design goal matrix to determine the best option. The system with the highest overall rating, based on a system comparison, was selected as the final option. Next, the system was analyzed for compliance with each major design goal. We propose the installation of geothermal heat pumps with heat pipe heat recovery units, based on system comparison, in order to condition the ImClone lab building. 2.0 INTRODUCTION The objective of this proposal is to present the most favorable HVAC system for the ImClone Lab Building located in New York City, New York. The proposal outlines three system options with a brief description of each system configuration. The systems are compared using design criteria and goals to obtain a final system selection. 2.1 Design Criteria The three system options are analyzed and evaluated using the following criteria defined by ASHRAE: 2.1.1 Performance Requirements 2.1.2 Capacity Requirements 2.1.3 Spatial Requirements 2.1.4 First Cost 2.1.5 Operating Cost 2.1.6 Reliability 2.1.7 Flexibility 2.1.8 Maintainability 2.1.9 Sustainability The first three categories are used as gates (yes or no questions that the system must meet), while the next six categories are comparisons. Based on research and calculations, the systems are rated against each other on a scale of 1-10, with “1” being the worst and “10” being the most suitable. Each criterion is assigned a weighted percentage
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KANSAS STATE UNIVERSITY ASHRAE System Selection directed by ASHRAE to signify its importance. The percentage was multiplied by the initial rating to produce a weighted rating. From these weighted ratings the system that is most appropriate for this application is chosen. 2.1.1 Performance Requirements When comparing each of the three systems, several performance requirements are considered to determine the best system to meet our design criteria. Those requirement categories are as follows: • Regulating the temperature and humidity to control the comfort in the office spaces according to ASHRAE Standard 55-2004 Thermal Environmental Conditions for Human Occupancy • Providing the necessary makeup air and ventilation air to meet ASHRAE Standard 62.1-2004 Ventilation for Acceptable Indoor Air Quality • Using 20% or less energy than ASHRAE Standard 90.1-2004 Energy Standard for Buildings Except Low-Rise Residential Buildings • Meeting the noise criteria for each space given by ASHRAE • Pressurizing laboratory spaces negatively to prevent cross contamination and exterior zones positively to the outside (excluding laboratory spaces) to eliminate infiltration 2.1.2 Capacity Requirements Capacity requirements are used in verifying that each of the systems can handle the calculated peak design loads. Some constraints involved in this analysis are indoor design conditions, outdoor design conditions, ventilation, and internal heat gains. 2.1.3 Spatial Requirements Spatial requirements consist of many different considerations and are not just dependent on floor space. When determining whether or not the systems fit into the allotted space, the following space considerations are evaluated: mechanical rooms (size and location), shaft space, plenum height, floor space, building height limitations, and maintenance access. 2.1.4 First Cost Minimizing first cost is one of the key aspects in determining the best system to meet the design criteria. First cost includes cost of equipment, piping, ductwork, installation, profit, and overhead. Safety factors are included to cover the cost of miscellaneous items that cannot be listed individually. 2.1.5 Operating Cost Operating cost is another key factor in evaluating the overall HVAC system cost. Energy is not the only component used to determine an appropriate operating cost. Total operating cost includes water consumption, labor (operating and maintenance), and a life cycle cost (discount rates, interest rates, replacement costs). All of the costs are calculated using an in-depth economic evaluation. The evaluation is based on a 20 year life cycle for each system and the numbers are all compared at a present value. 2.1.6 Reliability Reliability is evaluated based on longevity and value of the building operations. The project is analyzed and an opportunity cost is associated with downtime as a result of a system’s failure to perform. Critical use facilities, such as hospitals, laboratories, and data centers, have a higher opportunity cost in relation to system downtime. Once a “downtime cost” is established, it is theoretically added to the actual cost to repair the failure. Items
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KANSAS STATE UNIVERSITY ASHRAE System Selection considered during the evaluation are the value, or cost to the owner, during downtime of equipment, the average time to repair equipment, and the affect on the life safety of the building. 2.1.7 Flexibility The likelihood of future changes and the frequency of those changes are considered in a system selection/comparison. The ability to accommodate these changes can be an influencing factor. Additionally, flexibility eases the transition associated with downtime. When equipment fails, having a flexible system allows for other pieces to maintain desirable conditions during repair or replacement. 2.1.8 Maintainability Maintainability defines how much annual work needs to be done to the system once it is installed and operating. The analysis can be broken down into four main components: the skill level required by the maintenance team, the location of the maintenance activity, the preventive maintenance requirements, and the extent of expected breakdown repairs. The skill level required to maintain a system depends on the components and the complexity of the system. The location of maintenance activity is relative to the location of the major pieces of equipment. It is important to take into account if a system is centralized or decentralized. Centralized systems are those that contain most of their components in one space such as a mechanical room, making maintenance issues easier. Decentralized systems are those that contain equipment located throughout the space. This increases the difficulty of locating the failure and can potentially interrupt occupant productivity if located within a workspace. Preventive maintenance is done on a regular basis to keep the equipment operating at its peak condition. These tasks can include changing filters and checking all of the components of the equipment, such as the compressor, refrigerant, fans, and coils. The breakdown repair of a system is the work required to replace or fix components that fail. This also includes the “downtime cost” referred to earlier. 2.1.9 Sustainability ASHRAE defines sustainability as providing for the needs of the present without distracting from the ability to fulfill the needs of the future. Designing a HVAC system with sustainability in mind takes the effort of every member of the design team. When selecting a system, the importance of “green building design” is becoming more and more prevalent in the construction industry today. The U.S. Environmental Protection Agency (EPA) defines green or sustainable building as the practice of creating healthier and more resource-efficient models of construction, renovation, operation, maintenance, and demolition. When determining whether or not the system is considered to be “green,” there are a couple of resources that are helpful to follow. First, ASHRAE publishes a GreenGuide to help in designing towards a greener future. Second, the U.S. Green Building Council (USGBC) developed a Leadership in Energy and Environmental Design (LEED) rating system checklist that assigns point values to gauge the sustainability characteristics of a building. Third, the EPA publishes Labs-21, which adopts LEED credits specifically for laboratory projects.
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KANSAS STATE UNIVERSITY ASHRAE System Selection 2.2 Major Design Goals Along with the previously stated selection criterion, the system selected is designed to comply with the following major design goals: 2.2.1 Low 20 Year Life Cycle Cost 2.2.2 Low Environmental Impact 2.2.3 Comfort and Health 2.2.4 Creative High Performance Green Design 2.2.5 Synergy with Architecture 2.2.1 Low 20 Year Life Cycle Cost When analyzing the systems, a low 20 year life cycle cost is essential in quality HVAC design. This is primarily because in today’s industry the bottom line is, most often, money. When calculating the life cycle cost, there are four main components to the analysis: first cost, operating cost, replacement cost, and maintenance/repair cost. An interest rate of 6% per year and an escalation rate of 5% per year are used for all of the cost components. The initial cost is converted to a future value using an interest rate of 6% per year over a period of 20 years. The operating cost is determined by calculated building loads and energy consumption produced in Trace700. These consumption values are converted to costs using the given energy prices in Table 2.3. The costs are considered to be amounts that are incurred each year. These amounts are converted to a present value with the 5% per year escalation rate over a 20 year period. The present value is converted to a future value with the interest rate of 6% per year over a 20 year period. For replacement cost, the initial cost of each piece of equipment is converted to a future value over a period equal to its life expectancy using an escalation rate of 5% per year. This accounts for the new price of equipment when it needs to be replaced. Each piece of equipment is then brought to a least common multiple of years. This eliminated the need for a salvage value and a depreciation value. A new replacement cost had to be found for each replacement period. (For example, if equipment A initially costs $10,000 with a life expectancy of 15 years and equipment B initially costs $15,000 with a life expectancy of 20 years, the common year multiple is 60 years. For A, a replacement cost needs to be calculated at year 15, and then new ones at year 30 and 45. For B, a replacement cost needs to be calculated at year 20 and then a new one at year 40.) Replacement costs are converted to final values in the common multiple year using an interest rate of 6% per year over the period remaining until the common multiple year is reached. (If replacement of equipment A at year 15 costs $15,000, that new price is brought to year 60 using an interest rate of 6% per year for the remaining 45 years.) Once all of the replacement costs are obtained as a future value in the common multiple year, they are added together. Maintenance cost is calculated into a present value using a 5% per year escalation rate and calculated to a future value using 6% per year interest rate over the entire 20 year period. All components are in future values and added directly together. The final total future value is converted to a present 20 year life cycle cost. To simplify calculations, all costs are first brought to a 20 year future value and then to an overall present value. It is important to bring the cost to a present value to show an owner how much money they would need to set aside, today, to finance the selected options for a 20 year life cycle. An in depth economic analysis spreadsheet can be found in Appendix D. 2.2.2 Low Environmental Impact The environmental impact of an HVAC system has many aspects to consider. Since environmental issues are becoming more prevalent, minimizing the impact on the environment is very crucial. One of the major concerns of the design industry is buildings contributing large amounts of pollution to the atmosphere. According to the Department of Energy, U.S. buildings use one third of total energy, two-thirds of total electricity, and one-eighth of total water consumed. When buildings burn fossil fuels for operation, carbon dioxide gas is released. This
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KANSAS STATE UNIVERSITY ASHRAE System Selection causes an effect known as the “greenhouse effect”. This includes the use of carbon producing power plants that supply electricity. The greenhouse effect is believed to be a contributor to global climate change. A major design initiative of ASHRAE (specifically the Architecture 2030 Challenge) is to get buildings to become carbon neutral. The reduction of carbon emissions will have a sizable impact on the environment and air quality. When selecting an appropriate system, eliminating or reducing the quantity of components that emit carbon gases is desirable. Another area of concern, in relation to low environmental impact, is the total consumption of nonrenewable resources. By limiting the amount of fossil fuels (oil, coal, and gas) used, the building lowers its impact to the environment. In conjunction with lower emission of gases, having more efficient equipment also decreases total consumption of nonrenewable resources. 2.2.3 Comfort and Health Controlling the building systems to provide adequate comfort and a healthy atmosphere is always a necessity of any well designed system. This is particularly important when designing a lab space, especially in the area of health. Two standards of design that ASHRAE publishes, ASHRAE Standard 55-2004 and ASHRAE Standard 62.1-2004, give guidelines on how to best accomplish a comfortable environment and how to supply the necessary ventilation to obtain a high indoor air quality. In regards to this specific design, other health aspects need to be addressed. For a lab space, cross contamination is a major concern. Many different chemicals and harmful pollutants are dealt with daily in most lab applications. Cross contamination can be a problem in two main areas of design. First, if there is any heat recovery utilized from the exhaust air, the supply air stream and exhaust air stream cannot come in contact in any way. Complete separation is necessary to eliminate any chance for harmful air to infiltrate the supply air stream. Second, cross contamination is an issue in terms of total building pressurization. If the lab spaces are not kept negative relative to the adjacent spaces, contaminated air could infiltrate the adjacent spaces. Providing effective building pressurization is vital to maintain environments without any major health concerns. 2.2.4 Creative High Performance Green Design Creative high performance green design runs in parallel with low environmental impact. A good starting point with any green design is the USGBC’s LEED Green Building Rating System Version 2.2. Although this building is not trying to achieve certification status, the LEED checklist can be used as a guide on how to perform excellent green design. In accordance with the LEED checklist, EPA’s LABS 21 Version 2.1 is also a valuable resource in green laboratory design. It is easier for engineers to follow typical design practices and general rules of thumb. When designing within a creative realm, it is important to utilize imagination and “think outside the box” to come up with new and creative ways to solve problems. 2.2.5 Synergy with Architecture Synergy with architecture is especially important when renovating existing buildings. The building’s façade should hopefully remain untouched and the building’s integrity intact. Using the provided chases and mechanical room space is critical because it eliminates the need to alter the original structure. Any of these items are extremely desirable and are mainly owner driven. When choosing a system, it is important to select one that can perform to the requirements while still blending well with the surrounding architecture. Owners and architects prefer HVAC systems with the least architectural impact. 2.3 Building Description The building is located at 325 Spring Street New York City, New York in the borough of Manhattan. The structure, originally erected in the 1940’s, is currently used as a United Parcel Service (UPS) distribution center and will be leased
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KANSAS STATE UNIVERSITY ASHRAE System Selection by the client ImClone Systems Inc. This art deco style building is located roughly 500 feet to the east of the Hudson River between Washington and Greenwich Street. Refer to Figure 2.1 for an existing site layout.
Figure 2.1 – Existing Building Site in Relation to City Grid The 120,000 square foot lab/office building renovation creates many design challenges for the HVAC system. The design team’s intent is to create a mechanical system that is efficient and effective in providing optimal comfort and safety to the occupants. With the increase in energy costs, it is vital to install a system that will dramatically lower energy use for the life of the building without the loss of comfort or control. Three viable systems were selected through research and previous knowledge. The three system options analyzed are: • Open-Loop Geothermal Heat Pumps • Water Source Heat Pumps • Air handling unit (AHU) with Variable Air Volume (VAV) Reheat Boxes 2.4 Design Parameters The design parameters for cooling and heating conditions are based on the New York State Energy Conservation Construction Code and Exhibit 7 of ASHRAE Design Competition 2007. The outdoor design conditions are as follows: ASHRAE 99.6% ASHRAE 1% ASHRAE 1% Heating Design Cooling Design DB Cooling Design MWB New York, La Guardia Airport 13°F 89°F 76°F Table 2.1 – Outdoor Design Conditions The indoor design conditions for office spaces are given below: • Summer 75°F DB with 55 +/- 5% relative humidity • Winter 72°F DB with 25 +/- 5% relative humidity The indoor design conditions for lab spaces are give below: • Summer 72 +/- 2°F DB with 55 +/- 5% relative humidity • Winter 72 +/- 2°F DB with 25 +/- 5% relative humidity
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KANSAS STATE UNIVERSITY ASHRAE System Selection The design parameters for mechanical and electrical rooms are given below: • Summer Maximum of 104°F DB with no humidity control. • Winter Minimum of 60°F DB with no humidity control. The indoor design loads were as follows: Type Laboratories Offices Occupancy 1 person/200 SF Per Occupancy on plans Lighting 1.5 Watts/SF 1.5 Watts/SF Power 5 Watts/SF 4.5 Watts/SF 20 Watts/SF for equipment rooms Table 2.2 – Internal Loads The hours of operation for each type of space are given below: • Labs 24 hours, 7 days a week • Office 7 AM – 5 PM 5 days a week • Kitchen/Cafeteria 7 AM – 5 PM 5 days a week The ventilation criteria for each type of space are given below: • Laboratories 100% outside air 8-10 air changes per hour for biological labs 15-25 air changes per hour for vivarium spaces 7.5 air changes per hour during unoccupied times • Office 15 cfm per person outside air • Public Restrooms 75 cfm per water closet or urinal and or 6 air changes per hour The site utilities available for the ImClone renovation are natural gas, electricity, water, sewer, and high pressure steam. The average rates for the utilities at the site are as follows: Utility Rate ($) Natural Gas $7.00/MMBTU Electricity $.12/kWh Water $.002/gal. Sewer $.003/gal. High Pressure Steam $21.00/1000 lbs. Table 2.3 – Utility Rates Natural Gas will be provided at 5 psig, water at 80 psig, and high pressure steam at 125 psig. The electricity will be provided at 480V/3 phase, 208V/3 phase, 208/1 phase and 120/1 phase. It is assumed that the capacities of these utilities are adequate to support the proposed systems.
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KANSAS STATE UNIVERSITY ASHRAE System Selection 3.0 BASIC SYSTEM CONCEPTS Before specific system options are considered, basic design concepts must be analyzed. The basic system concepts for all the options are listed below: 3.1 System Zoning 3.2 Pressurization 3.3 Filters 3.1 System Zoning When examining the building, there are two distinctly different occupancies: lab areas and general office spaces. Ventilation requirements are the driving force in separating these spaces. The lab spaces require 100% outside air and also minimum air change rates, described in Section 2.4. This air is exhausted with no recirculation. The office spaces, however, only require 15 cfm/person of ventilation air and recirculation is acceptable. Occupancy densities are based on the architect’s furniture plan and ASHRAE Standard 62.1-2004. Along with ventilation, the different zones varied drastically by use and internal loads. All of these issues need to be considered before selecting systems. Six AHUs/DOAS units were selected for each system option to provide the required ventilation air. This selection is based on use of space and proximity. Similar spaces are grouped together to optimize the system’s efficiency. Four units are utilized to serve the lab spaces. Each unit is sized to handle the loads incurred in their system. The four large lab units separately supply the east and west wings of the third and fourth floor, respectively. An advantage to having a separate unit for each wing is that if one unit fails the other wings are unaffected. Two units are utilized in the office spaces. One unit serves the central atrium and open office area, while the other unit serves the south end offices and conference rooms. The reasoning behind this configuration is driven by the layout of the building and that two units can serve each respective area more easily. Splitting the areas allows smaller fans to be used with lower external static pressure. It would be difficult to combine the two areas onto one system because of the long duct runs down to the cellar space and high occupancy loads/ventilation requirements in the atrium/open office space. 3.2 Pressurization Pressurization is a significant issue when discussing lab spaces. It is important to maintain a negative pressure in the labs relative to corridors and/or adjacent spaces. To reach this pressure difference an 8:10 ventilation air to exhaust air ratio is utilized in the lab areas. The ratio was chosen to maintain an appropriate negative pressurization within the lab spaces. Each option considered has its own unique way of dealing with the controls of the exhaust and ventilation air. However, each option is very similar in the total cfm and room pressurization. The cfm in the adjacent corridors/spaces is increased to transfer the necessary amount of make-up air into the lab areas. The additional air supplied results in a net building pressurization of 5.8% positive. Refer to Figure 3.1 – total building pressurization detail for more detail on the pressurization concept utilized in these designs.
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KANSAS STATE UNIVERSITY ASHRAE System Selection
Figure 3.1 – Total Building Pressurization Detail 3.3 Filters Filters are a vital element in improving indoor air quality, particularly in labs. In lab spaces, a high efficiency filter is needed to keep contaminants out to ensure the accuracy of the experiments. To accomplish this, ventilation equipment serving the lab spaces are designed with 25% pre-filters to remove large particles from the air stream before it reaches the final filter. This is done to lengthen the life of the more expensive HEPA 95% efficient final filter. The HEPA filters are needed to satisfy the design parameters. The office spaces have the same filter configuration as the labs, but have slightly lower efficiency filters. The filter section consists of a 25% pre-filter and 85% final filter. Both filters were placed in the main ventilation units because individual heat pumps are not capable of dealing with the pressure drop associated with the high efficiency filters. 4.0 MAJOR SYSTEM COMPONENTS Each major system component was analyzed and selected to best fit the criteria and goals of the design. Not all of the components, described below, are in every system option. Each component is referenced in the system description, if they apply. 4.1 Boilers The boilers used in the systems described below are water-tube, gas fired boilers. Water-tube type boilers are chosen over fire-tube type boilers for their ability to reach higher efficiencies and are less susceptible to temperature shock. The system options using boilers have two sized at 66% of the calculated peak heating load. The design team chose not to design the boilers for 100% of the design load because of the high internal heat gain in the 24 hour lab spaces (assumed to handle the remaining 33% during peak calculated load). Also, a boiler designed for 2/3 of the load, operating at full capacity, is more efficient than a boiler designed for full load operating well below its capacity a majority of the time.
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KANSAS STATE UNIVERSITY ASHRAE System Selection Since steam is supplied to the building it was considered as a heating option, analyzed, and compared to a boiler. Due to a relatively high price per 1000 pounds of steam, using a shell and tube heat exchanger did not seem to be a viable option. Over a 20 year analysis period a steam heating system was over $400,000 more expensive than a boiler system. 4.2 Closed-Loop Evaporative Coolers The closed-loop evaporative coolers in the systems described below were selected due to the use of fewer chemicals, the reduction in water consumption, and the elimination of a heat exchanger. The system options using evaporative coolers have two sized at 100% of the design cooling load for redundancy. The closed system allows for a lower maintenance cost compared to an open-loop system (cooling tower) because it uses fewer chemicals to clean the water. In an open system, the water can collect particles from the air causing it to be corrosive. To correct this problem, chemicals are added to the collection basin to neutralize the water. In the event of a leak, these chemicals can cause adverse health effects. Additional make-up water is drastically decreased, reducing water consumption in a closed-loop system, because evaporation to the atmosphere does not occur. Other advantages of a closed system are the elimination of a heat exchanger and reduction in water consumption due to evaporation. Heat exchangers are used to keep cross-contamination from occurring between the cooling loop and system loop. Since there are no contaminants introduced into the cooling loop of an evaporative cooler, a heat exchanger is no longer necessary. 4.3 Pumps The pumps used in the systems below are base-mounted, end suction pumps. These pumps are selected for their optimal efficiency to handle the required gpm and feet of head. Each pump is sized for 100% of the required total gpm and ft of head. In each system, these pumps are designed in parallel for 100% redundancy. The pumps have a variable frequency drive (VFD) controlled by the pressure within the piping system. The VFDs handle varying load demands and save energy during off peak periods. The two pumps cycle from lead to lag based on an operating schedule. If the operating pump fails, the pump in standby mode will be switched over to operating mode. An alarm sent out through the building automation system calls for maintenance on the dysfunctional pump. When the pump is fixed, the pump operating cycle is reinstated. 4.4 Heat Recovery When examining the buildings large ventilation load, it is evident some type of heat recovery can significantly decrease the burden of conditioning the outside air. The heat recovery in the systems described below is a heat pipe heat exchanger. Heat pipes are used because of their ability to eliminate cross-contamination between the lab exhaust air and outdoor air intake. Original concepts included the use of an energy recovery ventilator (ERV) in the office spaces. Upon further analysis, the exhaust air flow rate from the office space would not be adequate to maintain an efficient ERV system because of the large quantities of outdoor air needed to maintain a positively pressurized building. Refer to Section 3.2 for building pressurization. The heat pipes use a water-glycol mix to transfer heat from the evaporator end (warmer side) to the condenser side (cooler side). A mechanically operated tilting mechanism is used to switch the operation during different seasons. A temperature actuator is connected to the heat pipe and tilts the pipe by rotating it about a center pin. Refer to Figure 4.1 for a heat pipe heat exchanger detail. A bypass around the heat pipe system is utilized to increase energy efficiency during optimal design outdoor design conditions. The heat pipe is bypassed at any outdoor temperature between 55°F DB and 72°F DB. These temperatures are selected because the heat pipe would raise the air temperature supplied to the system equipment that would in turn condition the air to 55 deg. An enthalpy override control sequence for the bypass will be utilized in the case of optimal dry bulb temperatures but higher than desired wet bulb temperatures. The wet bulb is important because the heat pipe heat exchanger can be used to decrease the relative humidity by raising the dry bulb temperature. The low temperature is selected given that 55°F DB supplied to the spaces will optimally satisfy general
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KANSAS STATE UNIVERSITY ASHRAE System Selection cooling requirements. The upper limit of 72°F DB is the temperature when the heat pipe will begin to be effective and precondition the outside air.
Figure 4.1 – Heat Pipe Heat Exchanger Detail 4.5 Exhaust System The exhaust system for all system options consist of fume hoods with a restricted sash, biological safety cabinets, point exhaust units (snorkel), standard ceiling exhaust grilles, and high velocity upblast exhaust fans. The kitchen design is not in the scope of work and is not accounted for in this paper. A typical lab space is shown on the lab airside schematic on page 15. The biosafety cabinet, point exhaust, and fume hood all exhaust a set amount of air. The fume hood draws a constant amount of air through the sash opening. The biosafety cabinet draws air either through the cabinet or, when the cabinet is not in use, through a thimble connection. The remaining exhaust air necessary to keep the room negatively pressured is exhausted by general exhaust grilles located in the ceiling. These grilles have venturi pressurization control air valves located in upstream ductwork, which are linked in operation with supply air venturi valves. These valves have extremely high pressurization control capability compared to traditional variable volume valves/boxes. This feature gives the ability to modulate the supply air during non load driven conditions down to the given minimum air change rate. The exhaust is combined together, ducted through the heat pipe heat exchanger, and propelled out of the building with high velocity upblast exhaust fans. Two of the upblast exhaust fans will be constant volume, while the other two fans will have louvers and motorized dampers that allow the exhaust to mix with outside air (maintaining constant volume through the exhaust fan). A mix design is considered necessary due to modulation of exhaust required during non load driven conditions. The dampers help prevent damage to the exhaust ducts if the pressure is to climb too high. The mix design, it also eliminates the need for the added expense of a VFD on the exhaust fans. Exhaust air for the office spaces will be ducted and combined with the lab exhaust. This configuration is used because of the low amount of exhaust air required in the office spaces. This eliminates the expense related to an additional exhaust fan serving only the office spaces. Moreover, this will allow the system to utilize the extra airflow to add heat recovery capacity to the heat pipe heat exchanger.
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KANSAS STATE UNIVERSITY ASHRAE System Selection 5.0 SYSTEM DESCRIPTIONS AND SCHEMATICS The selection process started out with many different possible systems and configurations. Initially the options were refined to include geothermal heat pumps, water source heat pumps, AHU’s with terminal reheat, fan coil units, and chilled beams. These systems were chosen because of their ability to control thermal comfort at the zone level. Each system was analyzed on the given design criteria to further reduce the list. Chilled beams were considered but ultimately found to be inadequate in meeting the design criteria. This system was eliminated due to it being a considerably new technology to the United States. Most general contractors are not familiar with its installation and also are not fully capable of giving an accurate price estimate. Inflated prices could ensue, resulting in higher initial cost for the owner. Furthermore, compared to typical chilled water systems, chilled beams require a higher than normal water temperature (normally 55-60°F) to eliminate condensation problems during cooling mode. This is a problem because it will result in higher flow rates, larger pipe sizes, and greater horsepower pumps. All of these items increased first cost. Likewise, when analyzing whether or not the chilled beams first cost would be offset by construction costs and energy costs, in depth research is performed. According to an article in the January 2007 ASHRAE Journal, if a building served by chilled beams was to be cost effective, the space cooling requirements needed to be governed by internal heat gain and not by air changes per hour. Initially, an assumption was made that the lab spaces were governed by internal heat gain, so chilled beams were considered. Upon further inspection and calculations, the assumption only proved correct in a portion of lab spaces. In addition, chilled beams life cycle cost is extremely high compared to the other systems. This is partly due to the fact that the large chilled beams could not efficiently serve the office spaces because of space requirements. Therefore, another system (heat pumps) had to be utilized in conjunction with chilled beams, increasing first cost again. Fan coil units were also considered but an in depth evaluation was not necessary. This is because fan coil units are very similar in design to water source heat pumps, in terms of space control, but are less efficient and require twice as much piping for the four pipe system considered. Consequently, fan coil units were eliminated from the selection process because of their high first cost and inefficiency. Ultimately, the systems were narrowed down to the three options outlined in the following sections. These options are open-loop geothermal heat pumps, water source heat pumps, and AHUs with terminal reheat. Each system was chosen based on its compliance with the mechanical design criteria and meeting design goals. 5.1 Option 1 – Open-Loop Geothermal Heat Pumps The open-loop geothermal heat pump’s primary (open) loop pumps, described in Section 4.3, are used to extract water, as a heat sink or source, from the adjacent Hudson River. A piping filtration system is employed to effectively eliminate particulate from the river loop before reaching the pumps and heat exchanger. The primary pumps move water through a plate-and-frame heat exchanger. This type of heat exchanger is more efficient than other types because of a high surface area to volume ratio. They are also very flexible for future expansion applications. Thermal energy is exchanged between the open, primary loop from the river and the closed, secondary loop serving the heat pumps throughout the building. The two secondary pumps are sized, operated, and controlled in the same manner as the primary pumps. The gpm is modulated by VFDs (by varying the frequency of the voltage to the pump motor) on the pumps due to a compressor bypass valve integral in each heat pump unit. This bypass decreases the feet of head by not having the water pass through the compressor. Refer to the hydronic one-line diagram located on page 15 for configuration and routing of the hydronic system. The heat exchanger between the interior/exterior loops allows the interior loop to extract or reject heat depending on the demand. During heating mode, the interior loop extracts heat via a heat exchanger, lowering the temperature of the exterior (river) loop. During cooling mode, the interior loop rejects heat via a heat exchanger, raising the temperature of the water returned to the river. This type of design is effective due to the fact that the river temperature is approximately 55°F all year if the water is drawn from a depth of at least 15 feet. The interior loop is sized for a total gpm according to the design loads of the building. The river loop’s gpm is matched accordingly to
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KANSAS STATE UNIVERSITY ASHRAE System Selection maximize efficiency of the heat exchanger. This heat exchanger keeps the interior loop between 55°F - 60°F year round, which is in turn supplied to each heat pump.
Figure 5.1 – Geothermal Heat Pump Detail The ventilation air is introduced into the zones by dedicated outdoor air systems (DOAS) located in the mechanical penthouse. The DOAS units draw the air through a heat pipe heat exchanger with the bypass described in Section 4.4 that recovers heat from the exhaust system described in Section 4.5. The major components within the DOAS units will be filters, a fan with VFD, a cooling coil, and a heating coil. The filter section is as stated in Section 3.3. The VFD regulates the fan speed and airflow in response to the system duct static pressure. This is needed because of the two-stage heat pumps utilized in spaces where load controls instead of air changes, varying the supply cfm between two set points depending on the demand. As static pressure increases in the duct, due to a decrease in cfm needed to condition the space, the VFD decreases the frequency of the electric current supplying the fan motor resulting in lower fan speed. The cooling coil is direct expansion (DX) and is supplied by an air cooled condensing unit located on the roof. A DX system is chosen over a hydronic system because of the minimal cooling requirements of the DOAS units and the increased initial cost of hydronic chilling equipment. The heating coil is electric due to the minimal heating load and lower first cost. During cooling mode, a cooling coil in the DOAS would first appear to be unnecessary because of the sensible heat recovered from the heat pipe heat exchanger. The heat pipe system is capable of bringing the outdoor air (at cooling design conditions) to 78.3°F DB/73.1°F WB. However, dehumidification is considered because the heat exchangers are sensible only and the heat pumps are packaged pieces of equipment that only operate under specific design parameters. Refer to Appendix E on page 37 for psychometric chart analysis. When dehumidification is needed, the direct expansion (DX) cooling coil cools and dehumidifies the air. The air is then reheated to 77°F DB/66°F WB (worst case design condition) and supplied to the heat pumps. The heat pumps then condition the air further to meet the zone loads. During heating mode, the heat pipe heat exchanger is capable of bringing the outdoor air (at heating design conditions) to 50.1°F dB. Since this is below the design supply air temperature, the DOAS units utilize an electric reheat coil to heat the leaving air temperature up to 55°F. This temperature is chosen because many of the zones (especially interior ones) will be asking for cooling even in extreme winter outdoor conditions due to the intense internal loads. The spaces calling for cooling make use of an electric compressor lockout control feature allowing the
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KANSAS STATE UNIVERSITY ASHRAE System Selection 55°F
air to be supplied directly to the space. Duct heaters are utilized throughout the spaces to reach the ARI/ISO certified conditions of 68°F entering air conditions for a two-stage heat pump in heating mode. Based on our calculations, some of the zones are governed by air changes per hour, while many of the zones are not. The zones not governed by air changes can have two-stage heat pumps. The low setting can be sized to cover the air changes and the upper setting to cover the maximum load based on internal loads and envelope loads. Refer to Appendix C page 35 for a sample load calculation of a lab space where internal loads govern. The office spaces do not have near the ventilation load/requirements that the lab spaces do. To obtain the required amount of supply air, return air from the space mixes with ventilation air from the DOAS at the heat pumps. The heat pumps utilize a 20% filter to protect the coils and compensate for any contaminants in the plenum and occupied space. In regards to hydronics, some jurisdictions may consider the water re-injected into the river to be a pollutant to the natural environment because of the slight temperature change. The design addresses this issue. After sizing the hydronic loop, a temperature change of 8°F, for the open loop, was calculated. It is assumed that this would be small enough to avoid impacting the river temperature, especially, since it is flowing into the ocean and the volume is nearly insignificant in comparison. However, in case New York City has some issues with the design, a supplemental alternative is incorporated to minimize the change in temperature re-injected into the river. The use of an exterior fountain to work in a manner similar to a cooling tower is a viable and innovative option. It will spray river return water directly into a stainless steel diffusion shield that disperses the flow. The droplets then trickle down multiple layers of stainless steel, with an integral fan blowing over the baffles, cooling the water as it trickles down to the holding tank where it is eventually returned back to the river. A control sequence is utilized to bypass the river entirely when the fountain heat transfer is sufficient to handle the load (part load conditions). Temperature sensors will be utilized to control the bypass valve so an optimal temperature change is acquired. This fountain could be integrated with the surrounding areas and used to potentially be incorporated into a park facility for the community. An assumption is being made that the proposed land real estate can be purchased. The design team believes that this is an excellent way for ImClone to give back to the community. Refer to Geothermal Heat Pump Hydronic one-line on page 15 for visual explanation of the fountain heat rejection process. System Components Airside System - (4) High Velocity Upblast Exhaust Fans - Variable Volume by use of an OA Louver - (2) Heat Pipe Heat Exchangers - (6) DOAS Units (4 – Labs, 2 – Offices) - DX Cooling Coils - Electric Reheat Coils - VFDs on Fans - 25% pre-filter and 95% final filter (labs) - 25% pre-filter and 85% final filter (offices) - Horizontal Heat Pumps at Zone Level - Two-Stage Units - Duct Heaters (if necessary) - 20% “throw away” filter - Venturi Air Flow Control Valves - Other Components - Ductwork - Dampers
Hydronic System - (2) 100% Load Open-Loop (Primary) Pumps - (2) 100% Load System Loop (Secondary) Pumps - (6) 100% Air Cooled Condensing Units - Other Components - Black Steel Pipe (Open River Loop) - Plate-and-Frame Heat Exchanger - Steel Pipe (Interior System Loop) - Possible “Cooling Tower” like Fountain
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KANSAS STATE UNIVERSITY ASHRAE System Selection 5.2 Option 2 – Water Source Heat Pumps The second system analyzed is a water source heat pump (WSHP) system. This system utilizes the heat recovery with a bypass and exhaust system as described in Sections 4.4 and 4.5, respectively. The WSHP system is similar to the open-loop geothermal heat pumps. The dissimilarities between them are found in the hydronic system and the airside supply. The WSHP system’s major hydronic components are boilers, closed-loop evaporative coolers, and pumps. These are described in Sections 4.1, 4.2, and 4.3, respectively. These components are used to condition the circulating loop supplying the WSHPs, as opposed to the open river loop described for the geothermal option. The circulating loop will bypass the boiler and evaporative cooler when the loop’s temperature is between 55°F and 90°F (the water loop temperature recommended by ASHRAE Handbook 2004 HVAC Systems and Equipment). When the temperature is outside the acceptable range, the boiler or evaporative cooler conditions the water to obtain a temperature within the acceptable parameters. When the loop reaches a temperature below 55°F, a three-way valve regulates the flow of water directed to the boiler, depending on how much heat is needed. Water routed to the boiler is mixed with hot water in a recirculation loop to prevent system shock caused by supplying low temperature water. Hot water from the boiler is then mixed into the loop to achieve an acceptable supply temperature to the heat pumps. When the loop reaches a temperature above 90°F, a three-way valve regulates the flow of water directed through the closed-loop evaporative cooler. Cooled water from the evaporative cooler is mixed into the loop to achieve an acceptable supply temperature to the heat pumps. Refer to Water Source Heat Pump Hydronic one-line on page 17 for a visual representation of the system. The airside supply is essentially the same as described in the geothermal option. The only difference associated is that each individual heat pump will have different capacities due to slightly varying entering water temperatures. Originally, the design team figured supplying the WSHPs with air between 68°F and 80°F was advantageous. The DOAS was going to heat the air, during heating mode, to 68°F, which is the lower limit that most heat pumps can handle. This temperature was chosen instead of the 55°F in the geothermal heat pumps to take advantage of a reverse return piping system’s ability to self-balance. However, realizing conditioning water is more efficient than air due to the thermal properties of each, the bypass is incorporated. System Components Airside System - (4) High Velocity Upblast Exhaust Fans - Variable Volume by use of an OA Louver - (2) Heat Pipe Heat Exchangers - (6) DOAS Units (4 – Labs, 2 – Offices) - DX Cooling Coils - Electric Reheat Coils - VFDs on Fans - 25% pre-filter and 95% final filter (labs) - 25% pre-filter and 85% final filter (offices) - Horizontal Heat Pumps at Zone Level - Two-Stage Units - 20% “throw away” filter - Venturi Air Flow Control Valves - Other Components - Ductwork - Dampers
Hydronic System - (2) 100% Load Frame-Mounted, End Suction Pumps - (6) 100% Air Cooled Condensing Units - (2) 66% Water-Tube Gas Fired Boilers - (2) 100% Closed-Loop Evaporative Coolers - Other Components - Steel Pipe (Interior System Loop)
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KANSAS STATE UNIVERSITY ASHRAE System Selection 5.3 Option 3 – AHUs with Terminal Reheat The third system analyzed is AHUs with terminal reheat devices. This system utilizes the heat recovery with bypass and exhaust system as described in Sections 4.4 and 4.5, respectively. The airside supply consists of AHUs supplying VAV reheat terminals, in the office spaces, and venturi air flow control valves with reheat coils, in the lab spaces. Both hydronic reheat applications are supplied by the boilers described in Section 4.1. VAV reheat terminals were chosen to provide zone level control to the occupants by varying the volume of air to the zone in response to occupants needs. Venturi valves were chosen because of the lab space’s need for a negative pressure relative to adjoining spaces. Venturi valves are placed in both the supply and exhaust runs to modulate both air flows to keep the required space pressurization and air change rates. This pressurization control is not possible when using standard VAV reheat terminals. The AHUs (supplying the terminal devices) major components are filters, a VFD, and hydronic heating and cooling coils. The filter section is as described in Section 3.3. The VFD on the AHU regulates the fan speed and airflow in response to the system duct static pressure. When heating is needed, the AHUs utilize a coil with hot water supplied by boilers described in Section 4.1. When cooling, the AHUs cooling coil utilizes chilled water provided by two centrifugal chillers and/or thermal ice storage. The chillers and boilers supply water using pumps described in Section 4.3. The hydronic system, serving the coils in the AHUs, is a four pipe configuration that utilizes two independent coils, one for heating and one for cooling. All of the coils will have a 2-way control valve on the return line that will modulate the amount of chilled/hot water through the coil based on the load demand. The terminal reheat units are hydronic and all of the piping is laid out in a reverse return arrangement as shown in Figure 5.4. An advantage to this system is that all of the pipe runs will have a more uniform pressure drop than if a direct return system was utilized, allowing higher level of control and balancing. In direct return, the various paths through each of the coil loops have different pressure drops. This forces balancing valves for the coils closest to the boiler/chiller to be mostly closed to compensate for the pressure drops. Figure 5.5 shows a typical direct return piping layout. A water side economizer is used to bypass the coils in the terminal reheat units and/or in the AHUs to reduce feat of head on the system’s pumps and utilize the pump VFDs.
Figure 5.4 - Reverse Return Piping Example
Figure 5.5 - Direct Return Piping Example
The cooling coils are served by two centrifugal chillers sized at full capacity and/or by thermal ice storage units when ice capacity is available. The centrifugal chillers are connected to two closed-loop evaporative coolers, described in Section 4.2, to reject heat. Overnight, the chillers are set to produce sub-freezing temperature water (hydronic lines have a glycol/water mixture to reach sub-freezing temperatures) used to create ice in thermal ice storage units and an ice sculpture. The sub-freezing glycol/water mixture can by-pass (by use of a three-way valve) all the cooling coils, when conditions are favorable, and can be routed through a thermal storage unit full of water and back to the chillers. The water is frozen overnight so that it may be used during the day during peak electric rates. This allows the chillers and closed-loop evaporative coolers to be potentially shut down during peak rate times and save on operating costs. In New York City, the electric energy rates are an average of 4¢/kwh greater (rates are from Con Edison, Inc.) during
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KANSAS STATE UNIVERSITY ASHRAE System Selection peak times (8am-10pm). See Figure 5.7 for a typical building electrical demand profile. During peak times the chilled water loop is pumped through the thermal ice storage units out to the cooling coils. As an innovative design feature, a thermal ice storage sculpture is proposed. During ice building mode, an ice sculpture is created in the shape of the ImClone logo. It will be located in the atrium space and add to the architectural aesthetics. Primarily, it will be used in accordance with the other ice storage units and serve in a typical thermal application. This is because it is not feasible to size the sculpture to handle the full cooling load. During the day, the sculpture will open its casing and the ice will be visible to the public. As an added feature, it will radiantly cool the surroundings. See below for the hydronic schematic drawing of the ImClone ice sculpture and refer to the terminal reheat hydronic one line in Figure 5.8 for hydronic schematics.
Ice Sculpture
Movable Forms in Daytime Position Water Collection Basin
Figure 5.6 – ImClone Thermal Ice Sculpture If at any time the thermal ice storage unit cannot support the building’s chilled water demand, the chillers and closedloop evaporative coolers will turn on and the thermal ice storage unit will be by-passed. Additionally, if cooling is required at night, some of the chilled water can be routed to the cooling coils to handle the demand during that time. This is accomplished by a three-way modulating valve that varies how much water goes to the cooling demand and how much goes to the ice storage. Some of the ice storage capacity will be lost during this period but since a large cooling load at night will be rare, the ice storage units, more often than not, will be fully charged leading into peak times. The only time a large cooling load will happen is during the worse case scenario. Ultimately, the ice storage will normally be fully charged during normal operating conditions.
Figure 5.7 – Typical Building Electrical Demand Profile
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KANSAS STATE UNIVERSITY ASHRAE System Selection System Components Lab Airside System - (4) High Velocity Upblast Exhaust Fans - Variable Volume by use of an OA Louver - (2) Heat Pipe Heat Exchangers - (4) AHUs - Hydronic Heating & Cooling Coils - Supply Fans - VFDs on Fans - Venturi Air Flow Control Valves - Hydronic Reheat Coils - Other Components - Ductwork - Dampers
Office Airside System - (2) AHUs - Supply & Exhaust Fans (with VFDs) - Hydronic Heating Coils - Hydronic Cooling Coils - VAV Boxes - Hydronic Reheat Coils - Other Components - Ductwork - Dampers
Hydronic System - (2) 66% Water-Tube, Gas Fired Boilers - (2) 100% Load Hot Water Circulating Pumps - (2) Closed-loop evaporative coolers - (2) 100% Load Closed-loop evaporative cooler Pumps - (2) 100% Load Centrifugal Chillers - Thermal Ice Storage Units and Ice Sculpture - (2) 100% Load Chilled Water Circulating Pumps - Other Components - Black Steel Pipe (over 2”) - Copper Pipe (2” and under)
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KANSAS STATE UNIVERSITY ASHRAE System Selection 5.4 Baseline System This system was created to show the minimum requirements of ASHRAE 90.1-2004. It is therefore a baseline system that the proposed system options can be compared to. Energy calculations were used to prove a minimum 20% reduction in energy consumption. The baseline system is the same as option 3 (AHUs with terminal reheat), except all heat recovery, economizers, and thermal storage components have been removed. Additionally, the general exhaust requirements in the office areas were taken care of by separate exhaust fans. Without these components, the AHUs will have to be upsized to handle the loads needed to condition the large quantities of ventilation air. Also, the centrifugal chillers will have to run during peak electric rate periods, which will increase the operating cost. System Components Lab Airside - (4) High Velocity Upblast Exhaust Fans - Variable Volume by use of an OA Louver - (4) AHUs - Hydronic Heating & Cooling Coils - Supply Fans - VFDs on Fans - Venturi Air Flow Control Valves - Hydronic Reheat Coils - Other Components - Ductwork - Dampers
Office Airside - (2) AHUs - Supply & Exhaust Fans - Hydronic Heating Coils - Hydronic Cooling Coils - VAV Boxes - Hydronic Reheat Coils - Other Components - Ductwork - Dampers
Hydronic System - (2) 66% Water-Tube, Gas Fired Boilers - (2) 100% Load Hot Water Circulating Pumps - (2) Closed-loop evaporative coolers - (2) 100% Load Closed-loop evaporative cooler Pumps - (2) 100% Load Centrifugal Chillers - Other Components - Black Steel Pipe (over 2”) - Copper Pipe (2” and under)
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KANSAS STATE UNIVERSITY ASHRAE System Selection 6.0 SYSTEM COMPARISONS Mechanical Cost Data 2006 and Building Maintenance and Repair 2004, both by RS Means, were referenced for determining installed first cost and maintenance cost. Some pieces of equipment could not easily be estimated using the RS Means catalogs. For these items, local product representatives were utilized to estimate equipment cost. Spreadsheets were then created to tabulate the installed first cost and maintenance cost data. These spreadsheets can be found in Appendix B on page 32. The energy consumption data was calculated using Trane Trace 700 to estimate the operating cost. All of these cost evaluations were used to calculate a full 20 year life cycle system analysis, which is located in Appendix D on page 36. The system options were compared using the given design criteria. These comparisons are explained in depth below and refer to Table 6.1. 6.1 Performance Requirements This requirement is either a yes or a no answer. If the requirement is not met, that system is automatically eliminated from the selection process. All system options met the requirement of performing 20% more efficient than ASHRAE Standard 90.1-2004, as shown in Table 6.1. All systems selected met the ventilation requirements, ASHRAE Standard 62-2004, and ASHRAE Standard 55-2004. 6.2 Capacity Requirements This requirement is straightforward in its analysis. All of the systems compared met the peak loads that were calculated and sized to handle these loads. Thus, there are no real comparisons between options when analyzing this requirement. 6.3 Spatial Requirements This requirement is a yes/no answer, but since each system met the minimum spatial requirements a rating from 1-10 was used to better compare them. Floor-floor height, floor space, shaft space, and maintenance access were used to rate the overall spatial requirements. For floor to floor height, the terminal reheat system was rated higher because less plenum space is necessary for terminal boxes when compared to heat pumps. But the AHU with terminal reheat system received the lowest rating because it has boilers, chillers, and large thermal ice storage units. The geothermal system was given the highest rating in the floor space category due to more available mechanical space. Its design inherently uses less equipment because it does not have to produce any chilled or hot water. The Hudson River is used as an indirect heat sink/source to condition the hydronic loop supplying the heat pumps. This inherently eliminates big items like boilers, chillers, or cooling towers. Heat pumps do require more space for maintenance, but the geothermal heat pump system is the most desirable in terms of overall space required. 6.4 First Cost In analyzing the first cost, the water source heat pump had the lowest first cost. This is because it does not have the added cost of a trench to the river (geothermal) or multiple thermal storage units (AHU with terminal reheat). Geothermal is the most expensive due to the high cost of the piping to the river, trenching, and duct heaters for the heat pumps. See Appendix B on page 32 for the detailed first cost analysis. 6.5 Operating Cost The total operating cost includes water consumption, labor (operating and maintenance), and a life cycle cost (discount rates, interest rates, replacement costs). The geothermal heat pump system scored the highest because of its low total energy consumption. By utilizing the constant water temperature available from the river, the system
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KANSAS STATE UNIVERSITY ASHRAE System Selection eliminates the need for additional hydronic conditioning equipment. The AHU system scored the worst because, overall, heat pumps operate at a higher efficiency. See Appendix C on page 35 for the operating cost analysis. 6.6 Reliability Reliability is evaluated based on longevity and value of the building operations. The project was analyzed and an opportunity cost was associated with downtime as a result of a system’s failure to perform. Since this is a laboratory facility, downtime could be devastating to any of the laboratory experiments. To minimize any downtime, redundancy was designed for all of the system options. If failure was to occur, an optimum system would be one that does not have a large lead time on its component replacements. The geothermal system had a slightly higher rating than the other options due to fewer moving parts, fewer overall components and heating and cooling being provided at the zone level. Heating and cooling at the zone level is more reliable because in the event of a heat pump failure only one zone is affected, instead of an entire system. 6.7 Flexibility Flexibility includes the cost and ease of future changes to the system in order to provide comfort for future inhabitants. The system components of each option have the same ease of integration; therefore, flexibility was evaluated at the zone level. The AHU with terminal reheat system received a slightly higher rating because it is less expensive to replace or modify the terminal units than the heat pumps. 6.8 Maintainability The maintainability of an HVAC system is evaluated on the skill level required to maintain, location of maintenance activity, preventive maintenance, and activities required if the equipment fails. The water source heat pumps have the lowest rating since the system includes the most equipment to maintain. The geothermal system has the least amount of equipment to maintain, but still requires the highest skilled maintenance personnel compared to the other system options. The terminal reheat option scored slightly higher than the geothermal option, even though it has boilers and chillers to maintain, because the terminal units require significantly less preventative maintenance. Another reason the terminal reheat system received the highest rating is because of its more centralized configuration compared to the other system options. 6.9 Sustainability The impact the system has on the surrounding environment is a main consideration in evaluating sustainability. Heat recovery was implemented into all system options to elevate some of the ventilation load associated with 100% outside air. This is a relatively simple method of increasing a system’s green design. Heat energy is recovered in accordance with the system described in Section 4.4. The designer must also consider the condition of the air that will be exhausted. It must be controlled to limit the amount of contaminants that could harm the environment both locally and globally. All systems utilize high velocity upblast exhaust fans to disperse any contaminants high into the atmosphere to allow dilution to occur before it returns to a habitable elevation. The geothermal heat pump system achieved the highest rating on green design by using a renewable resource. This eliminates the need for a boiler, cooling tower, and chiller. Removing these components from the system lowers the operational cost and the impact on the environment. It does this by eliminating the need for fuel/electricity to power these components and by reducing overall emissions. LEED points are given to HVAC systems that are more efficient than the ASHRAE 90.1-2004 minimums and the reduction of ozone depleting refrigerants. The heat pumps use HFC-410A refrigerant, which is zero ozone depleting. All these factors contributed in the geothermal system receiving a perfect 10 points.
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KANSAS STATE UNIVERSITY ASHRAE System Selection 6.10 Summary The design criteria matrix shown below in Table 6.1 was used to describe in depth how each of the system options related to the design criteria established. All of these criteria were assigned a numerical rating from 1-10, with 10 being the most suitable, that accurately quantifies the differences between each option. These numerical ratings were then multiplied by a given weighted factor and added together. The system having the highest total weighted rating would be considered the best possible system for this project. The results of this comparison are shown in Table 6.2.
Performance Requirements Capacity Requirements Spatial Requirements
First Cost Operating Cost Reliability
Flexibility Maintainability
Sustainability
Design Criteria Matrix Geothermal Heat Pump Water Source Heat Pumps Met ASHRAE Standard 55 and Met ASHRAE Standard 55 and Standard 62 Standard 62 Beat ASHRAE Standard 90.1 Beat ASHRAE Standard 90.1 by 32% by 72% Met peak loads calculated Met peak loads calculated Least mechanical space used due to less equipment Least available plenum space due to size of heat pumps Medium ease of maintenance access to the heat pumps
Medium mechanical space used due to large AHUs, boilers, and chillers Least available plenum space due to size of heat pumps Medium ease of maintenance access to the heat pumps $3,798,800 $3,210,900 $90,177 $124,015 Medium lead time on heat Medium lead time on heat pumps pumps Low lead time on other High lead time on other equipment equipment Low effect on life safety if Low effect on life safety if there there is failure due to redundancy is failure due to redundancy Medium cost for future Medium cost for future changes changes Medium skilled HVAC laborer Medium skilled HVAC laborer needed for repairs needed for repairs Medium skilled laborer needed Medium skilled laborer needed for preventative maintenance. for preventative maintenance. Least amount of annual Most amount of annual maintenance due to amount of maintenance due to amount of equipment equipment Most Sustainability with Medium Sustainability due to geothermal system boilers, chillers, etc. LEED points are available LEED points are available because the heat pumps utilize because the heat pumps utilize HFC-410A (zero ozone HFC-410A (zero ozone depleting) depleting) The heat pipe heat recovery LEED points available for lowers the overall building energy using geothermal system consumption The heat pipe heat recovery lowers the overall building energy consumption
Table 6.1 – Design Criteria Matrix
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AHU with Terminal Reheat Met ASHRAE Standard 55 and Standard 62 Beat ASHRAE Standard 90.1 by 31% Met peak loads calculated Most mechanical space used due to large AHUs, boilers, thermal storage units, and chillers Most available plenum space due to smaller terminal units Most ease of maintenance access to the terminal units $3,617,800 $127,820 Lowest lead time on terminal units High lead time on other equipment Low effect on life safety if there is failure due to redundancy Inexpensive for future changes Low skilled HVAC laborer needed for repairs Low skilled laborer needed for preventative maintenance Medium amount of annual maintenance due to amount of equipment Least Sustainability due to boilers, chillers, etc. LEED points possible with thermal ice storage The heat pipe heat recovery lowers the overall building energy consumption
KANSAS STATE UNIVERSITY ASHRAE System Selection
Geothermal Heat Pump Water Source Heat Pump AHU with Terminal Reheat Design Criteria Initial Weighted Initial Weighted Initial Weighted (weighted percentage) Rating Rating Rating Rating Rating Rating First Cost (30%) 5 1.50 7 2.10 6 1.80 Operating Cost (20%) 9 1.80 6 1.20 6 1.20 Reliability (15%) 8 1.20 7 1.05 7 1.05 Flexibility (15%) 5 0.75 5 0.75 6 0.90 Maintainability (10%) 5 0.50 3 0.30 6 0.60 Sustainability (10%) 10 1.00 8 0.80 5 0.50 Total
6.75
6.20
Table 6.2 - System Comparison
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6.05
KANSAS STATE UNIVERSITY ASHRAE System Selection 7.0 DESIGN GOALS Once the system was selected from Table 6.2, it was analyzed to see if it met the major design goals that were established. The geothermal heat pump system did meet each of the goals and, in fact, was superior to the other options considered in every facet. Table 7.1 summarizes how the system responded to each of the design goals. Low 20 year Life Cycle Cost Low Environmental Impact
Comfort and Health Creative High Performance Green Design
Synergy with Architecture
Geothermal Heat Pumps $ 7,429,000 This represented lowest cost of all options presented Optional fountain (cooling tower) to prevent thermal pollution into the Hudson River Heat Pumps with refrigerant HFC-410A Meet all mechanical design comfort criteria for both office and lab spaces Heat pipe recovery Heat Pumps with refrigerant HFC-410A Open geothermal water loop integrated with the river w/optional fountain (cooling tower) to prevent thermal pollution Optimal energy performance Fume exhaust fans on the roof Least amount of other equipment located on roof Minimal vertical shafts in building
Table 7.1 – Major Design Goals Matrix
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KANSAS STATE UNIVERSITY ASHRAE System Selection 8.0 FINAL SYSTEM SELECTION AND RECOMMENDATIONS We propose the installation of geothermal heat pumps with heat pipe heat recovery units, based on the system selection process established, in order to condition the ImClone lab building. The final selection process utilized the Design Criteria Matrix in Table 6.1, System Comparison in Table 6.2, and Major Design Goal Matrix in Table 7.1 to determine the best option. The system with the highest overall rating, based on the system comparison, was initially selected as the final option. Next, the system was analyzed for compliance with each major design goal. When looking at the system design criteria, it is not advisable to look just at the highest number. Each criterion had a different importance factor designated by a weighted percentage. These percentages are in direct correlation to establishing values associated with trade offs between criteria. Granted, a lower first cost might be more appealing up front, but every designer must ask “is the juice worth the squeeze”? Ultimately, all systems selected were evaluated to only include energy efficient components that achieved enough operational savings to compensate for the first cost. The geothermal heat pump option garnered a 6.75 rating compared to a 6.20 and a 6.05 rating for WSHP and AHU with terminal reheat options, respectively. Also, this system addresses the major design goals while going above and beyond its counterparts, especially in the areas of 20 year life cycle cost, environmental impact, green design, and synergy with architecture. For 20 year life cycle cost, the geothermal heat pump system was the lowest value at $7,429,000. The WSHP system was next, at $7,634,000, followed by the AHU with terminal reheat, at $8,594,000. Ultimately, this shows that over the 20 year life of the building, the maximum amount of money an owner would need to set aside to finance the geothermal system for the duration is $7,429,000. One way the environmental impact can be reduced is by incorporating an overall green design. The heat recovery equipment will save energy and minimize the loads on the heat pumps. The need for cooling will be satisfied by the heat pumps’ self-contained refrigeration equipment, thus eliminating boilers and chillers. The heat pumps selected utilize HFC-410A zero ozone depletion refrigerant, making it an extremely environmentally-friendly option. Overall, the greatest benefit realized by the owner will be due to the efficient nature of the geothermal heat pumps and the heat pipe heat recovery unit. Geothermal heat pumps utilize natural heating and cooling energy from the earth (river), reducing the amount of natural resources consumed for operation. This minimizes the impact on the environment when compared to the other systems by reducing the carbon dioxide gas associated with burning fossil fuels. In existing building renovations, maintaining the architectural integrity is normally an important goal of the design team. The majority of the geothermal system will reside above the ceiling (heat pumps and ductwork) and the need for central plant equipment is minimal, creating increased floor space and minimizing equipment in penthouse. In heat pump systems ductwork sizes are considerably less when compared to variable volume systems. This result frees up plenum space for other trades preventing unnecessary architectural conflicts. When investigating each system option in accordance with the design criteria and major design goals, the geothermal heat pump option was found to be the most favorable HVAC system selection.
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KANSAS STATE UNIVERSITY ASHRAE System Selection 9.0 APPENDICES The following appendices are supplemental information regarding the design process. 9.1 Appendix A - Assumptions 1. The kitchen space on the ground level to be handled by an independent contract with its own ventilation and exhaust system because of the many variables that need to be known to size it. 2. Excavation for geothermal loop to Hudson River is feasible. 3. Noise criteria is achieved in selecting heat pumps.
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KANSAS STATE UNIVERSITY ASHRAE System Selection 9.3 Appendix C – Operating Cost
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KANSAS STATE UNIVERSITY ASHRAE System Selection 9.4 Appendix D – 20 Year Life Cycle Cost Analysis
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KANSAS STATE UNIVERSITY ASHRAE System Selection
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KANSAS STATE UNIVERSITY ASHRAE System Selection
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KANSAS STATE UNIVERSITY ASHRAE System Selection 9.5 Appendix E – Sample Calculation of Lab Space Where Internal Load Governs
CONDUCTION (TRANSMISSIO
7-33 7V,17
EXPOSURE
ITEM
W all
Page: 1 of 76 Inside db 72 RH % 72 Re: Tbl 4-7A-B 5-15-17
AREA
N S E W
Glass
U
UXA
44.25
0.041
1.81
45
0.43
19.35
HTG ∆T
GLASS GLASS
GLASS GLASS
ITEM unshaded shaded windows doors shaded unshaded shaded windows doors
AREA
W /Fixt or W /SF
Total W atts
EXPOSURE
BTUh COOLING LOAD
7-35
∆T or CLTD
107
17 17 17 17
329
1142
CONDUCTION SUBTOTALS
365
1249
7-4-10
7-3
SC
SHGF
N S 45
E
0.63
216
6124
W
ELECT
1.5 5
PEOPLE
6124 CLG SENS LOAD
7-15
225 750
W atts x 3.413 = BTUh ELECT SUBTOTAL
EQUIP
INTERNAL LOADS
150 150
BTUh HEATING LOAD
36
SOLAR SUBTOTAL LIGHTS / POW ER
Date: 3/26/2007 ∆Grains
19.7
0.068
ROOF/CEILING FLOOR
TIME
3 55
59 59 59 5pm 59 59 59 59 59 59 59 59 59
Doors
21
SOLAR
EXTERNAL LOADS
Project: ImClone - Rm 4062 Isotope Lab Cooling: Outside db 89 mwb Heating: Outside db 13 Inside db
768 2560 3328
7-14
5-9
# of PEOPLE
1 EQUIP
LATENT BTUh/ea
200 LATENT
CLG LAT LOAD
SENS BTUh/ea
250 SENS
200 Hooded
ITEM
CFM
Space CLG INFILT Space HTG Door CLG Door HTG
250
Unhooded 7-16 - 7-27
EQUIPMENT SUBTOTALS CLG HTG ∆T CLG ∆T ∆G
5-1, 13A/B
CLG SENS LOAD
200 CLG LAT LOAD
250 CLG SENS HEATING LOAD LOAD
Q L = CFM x .69 x ∆G Q S = CFM x 1.08 x ∆T
INFILTRATION SUBTOTALS Cooling & Heating Space Load Subtotals = Conduction + Solar + Internal + Infiltration
200
10066 CLG CFM
1249 HTG CFM
466 33 Required Supply Air CFM = Sensible Space Load Subtotals / 1.08 (SA - RA ∆T) CLG CLG LAT CLG SENS HEATING HTG ∆T CLG ∆T ∆G CFM/SF LOAD LOAD CFM LOAD 5-9
VENT
15
Q L = CFM x .69 x ∆G
59
13
211
956
211
956
10277
2204
Q S = CFM x 1.08 x ∆T
VENTILATION SUBTOTALS
Cooling & Heating Equipment Loads = Space Load Subtotals + Ventilation Loads Cooling Tons = (Clg Lat + Clg Sens) / 12,000 = 0.87
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200
KANSAS STATE UNIVERSITY ASHRAE System Selection
AIR CHANGE CHECK AIRCHANGES PER HOUR (SUPPLY) 8 ACH AIRCHANGES PER HOUR (EXHAUST) 10 ACH 2 FLOOR AREA 150 FT FLOOR TO CEILING HEIGHT 11.5 FT 3 VOLUME 1725 FT CFM= 230 CFM (ACH)(VOL)/(60) LOAD= 4301 BTUH 1.1(CFM)(?T) *LOAD GOVERNS FOR THIS ROOM NOT AIR CHANGE RATE*
8*1725/60 1.1*170*17
SUPPORTING INFORMATION (ALL TABLES AND VALUES ARE FROM PRINCIPLES OF HVAC) Wall R-Value Wall U-Value Wall Type
WALLS 24.4 (1/U) 0.041 Given 15 Table 7-37C Mass outside insulation (C2-Lightweight Concrete Block)
Table 7-35-J40 Wall No. 16 @ 8am (New York = 40˚ Lat) (USED BECAUSE IT IS WORST CASE FOR GLASS) CLTD= 9+(78-72)+((97-(14.6/2))-85) CLTD= 19.7
Window U-Value
WINDOWS 0.43
PEOPLE TABLE 7-14 RATES OF HEAT GAIN FROM OCCUPANTS SENSIBLE 250 BTU/h LATENT 200 BTU/h
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KANSAS STATE UNIVERSITY ASHRAE System Selection 9.6 Appendix F Psychrometric Chart of Lab Space
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KANSAS STATE UNIVERSITY ASHRAE System Selection 10.0 REFERENCES Peter Rumsey and John Weale. ASHRAE Journal. January 2007. Pgs 18-25. ASHRAE. 2004. ANSI/ASHRAE, Standard 62.1 – 2004, Ventilation for Acceptable Indoor Air Quality. American Society of Heating Refrigeration and Air Conditioning Engineers, Inc., Atlanta, GA. 2004 ASHRAE. 2004. ANSI/ASHRAE, Standard 90.1 – 2004, Energy Standard for Buildings Except Low-Rise Residential Buildings. American Society of Heating Refrigeration and Air Conditioning Engineers, Inc., Atlanta, GA. 2004 ASHRAE. 2005 ASHRAE Handbook – Fundamentals . American Society of Heating Refrigeration and Air Conditioning Engineers, Inc., Atlanta, GA. 2001. ASHRAE. 2003 ASHRAE Handbook – Applications . American Society of Heating Refrigeration and Air Conditioning Engineers, Inc., Atlanta, GA. 2001. ASHRAE. 2004 ASHRAE Handbook – Systems and Equipment . American Society of Heating Refrigeration and Air Conditioning Engineers, Inc., Atlanta, GA. 2001. ASHRAE. GreenGuide. American Society of Heating Refrigeration and Air Conditioning Engineers, Inc., Atlanta, GA. 2003. Baltimore Air Coil Company, "BAC Product & Application Handbook, Vol. II." Baltimore Air Coil Company. 26 April 2007. .http://www.epa.gov/greenbuilding/ COLMAC COIL MFG., INC., "COLMACHEAT PIPE COILS Air-to-Air Heat Exchangers for Commercial & Light Industrial Markets." 1 March 2000. COLMAC COIL MFG., INC. 26 April 2007. . EPA. Labs 21 Environmental Performance Criteria. Environmental Protection Agency, Washington, DC. 2005 “HVAC System Selection.” ASHRAE. 26 April 2007 McQuay Products Catalog, "Water Source Heat Pumps." Enfinity™ and Model CRH/CRW Horizontal Water Source Heat Pumps—1/2 to 6 Tons. 26 April 2007. . R.S. Means. 2006. Mechanical Cost Data, 29th Annual Edition. R.S. Means. Kingston, MA. R.S. Means. 2006. Facilities Maintenance & Repair Cost Data. R.S. Means. Kingston, MA. USGBC 2002. LEED. Green Building Rating System For New Construction & Major Renovations. Leadership in Energy and Environmental Design, Washington, DC.
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