The Experts below are selected from a list of 183 Experts worldwide ranked by ideXlab platform
Mingsheng Liu - One of the best experts on this subject based on the ideXlab platform.
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Choosing the Right Parameter for Single-Duct Constant Air Volume System Supply Air Temperature Reset
Journal of Architectural Engineering, 2005Co-Authors: G. Wei, W. D. Turner, David E. Claridge, Mingsheng LiuAbstract:To improve system efficiency under part-load conditions, the supply Air Temperature set point for a single-duct constant Air volume Air handling unit (AHU) system is often reset based on either Return Air Temperature or outside Air Temperature. Both reset strategies make engineering sense as long as the reset schedules are reasonable. Quite often the decision to use one over the other is made with the assumption that they will both achieve some energy savings. However, the impact of these two strategies on AHU energy consumption could be very different. An in-depth analysis and comparison of these two commonly used supply Air Temperature reset strategies for a single-duct constant Air volume system is presented in this paper. It is shown that the reset strategy based on outside Air Temperature is inherently better than that based on Return Air Temperature, with lower energy consumption and improved building comfort level.
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Single-Duct Constant Air Volume System Supply Air Temperature Reset: Using Return Air Temperature or Outside Air Temperature?
Architectural Engineering 2003, 2003Co-Authors: G. Wei, W. D. Turner, David E. Claridge, Mingsheng LiuAbstract:The supply Air Temperature set point for a singleduct constant Air volume Air handling unit (AHU) system is often reset based on either Return Air Temperature or outside Air Temperature in order to reduce simultaneous cooling and heating energy consumption. Both reset strategies make engineering sense as long as the reset schedules are reasonable. Quite often the decision to use one over the other is made with the assumption that they will all achieve some sorts of energy savings. However, the impact of these two strategies on AHU energy consumption could be very different. A comparison of these two commonly used supply Air Temperature reset strategies for a single-duct constant Air volume system is presented in this paper. It is shown that from either the building energy consumption or building comfort point of view, the reset strategy based on outside Air Temperature is inherently better than that based on Return Air Temperature. Significant amount of heating energy savings can be achieved by switching from Return Air Temperature based reset to outside Air Temperature based reset. The reset strategy can also benefit variable Air volume (VAV) AHUs. An improved supply Air Temperature set point reset control strategy is proposed by combining and staging the outside Air and Return Air Temperature based resets.
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An Advanced Economizer Controller for Dual Duct Air Handling Systems -with a Case Application
1996Co-Authors: Mingsheng Liu, David E. ClaridgeAbstract:penalty is expected when economizers are applied to dual-duct Air handling systems. The heating penalty can even be higher than the cooling savings when the hot Air flow is higher than the cold Air flow. To avoid the excessive heating penalty, advanced economizers are developed in this paper. The application of the advanced economizer has resulted in $7,00O/yr savings in one 95,000 ft2 school building since 1993. The impacts of cold and hot deck settings on the energy consumption are also discussed. INTRODUCTION economizer cycle is currently one of the most popular energy conservation measures for Air handling units (AHU) in buildings. There are two types of economizers, the Temperature economizer and the enthalpy economizer (I). The Temperature economizer maintains the mixed Air Temperature at the cold deck discharge Air Temperature when the outside Air Temperature is lower than the cold deck discharge Air Temperature. Consequently, the need for mechanical cooling is eliminated. When the outside Air Temperature is higher than the cold deck discharge Air Temperature, but lower than a change point Temperature which is generally a few degrees lower than the Return Air Temperature, the Temperature economizer uses maximum outside Air to minimize the mechanical cooling
David E. Claridge - One of the best experts on this subject based on the ideXlab platform.
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Choosing the Right Parameter for Single-Duct Constant Air Volume System Supply Air Temperature Reset
Journal of Architectural Engineering, 2005Co-Authors: G. Wei, W. D. Turner, David E. Claridge, Mingsheng LiuAbstract:To improve system efficiency under part-load conditions, the supply Air Temperature set point for a single-duct constant Air volume Air handling unit (AHU) system is often reset based on either Return Air Temperature or outside Air Temperature. Both reset strategies make engineering sense as long as the reset schedules are reasonable. Quite often the decision to use one over the other is made with the assumption that they will both achieve some energy savings. However, the impact of these two strategies on AHU energy consumption could be very different. An in-depth analysis and comparison of these two commonly used supply Air Temperature reset strategies for a single-duct constant Air volume system is presented in this paper. It is shown that the reset strategy based on outside Air Temperature is inherently better than that based on Return Air Temperature, with lower energy consumption and improved building comfort level.
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Single-Duct Constant Air Volume System Supply Air Temperature Reset: Using Return Air Temperature or Outside Air Temperature?
Architectural Engineering 2003, 2003Co-Authors: G. Wei, W. D. Turner, David E. Claridge, Mingsheng LiuAbstract:The supply Air Temperature set point for a singleduct constant Air volume Air handling unit (AHU) system is often reset based on either Return Air Temperature or outside Air Temperature in order to reduce simultaneous cooling and heating energy consumption. Both reset strategies make engineering sense as long as the reset schedules are reasonable. Quite often the decision to use one over the other is made with the assumption that they will all achieve some sorts of energy savings. However, the impact of these two strategies on AHU energy consumption could be very different. A comparison of these two commonly used supply Air Temperature reset strategies for a single-duct constant Air volume system is presented in this paper. It is shown that from either the building energy consumption or building comfort point of view, the reset strategy based on outside Air Temperature is inherently better than that based on Return Air Temperature. Significant amount of heating energy savings can be achieved by switching from Return Air Temperature based reset to outside Air Temperature based reset. The reset strategy can also benefit variable Air volume (VAV) AHUs. An improved supply Air Temperature set point reset control strategy is proposed by combining and staging the outside Air and Return Air Temperature based resets.
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Evaluation of Energy Conservation Measures by Model Simulation
1998Co-Authors: Tim Giebler, M. Liu, David E. ClaridgeAbstract:Numerous energy conservation measures are being implemented into the Air handler units of today's commercial buildings. The economizer cycle has proven potential, and has become increasingly more common. Work has also been done demonstrating that hot and cold deck reset schedules, optimized according to outside Air Temperature, can result in significant energy savings. This paper presents a case study of these energy conservation control schemes in a dual duct VAV building on the Texas A&M campus in College Station, the Hanington Education Tower. The current system was simulated and the model used to investigate the effects of economizer cycles and optimization of the hot and cold deck reset schedules. Introduction There is a growing necessity to design energy efficiency and conservation measures into new commercial building systems and also retrofitting them into existing buildings. The economizer cycle has become a recognized and popular measure used in building Air handler units (AHU). The Temperature economizer minimizes the AHU mechanical cooling by controlling the outside Air flow rate and using it to cool the mixed Air to the cold deck set point, if possible. The Temperature economizer operates between a protective low Temperature limit and the change point Temperature. The change point Temperature should be at least a few degrees lower than the Return Air Temperature. The mechanical cooling is eliminated when the outside Air Temperature is below the cold deck set point and within the economizer operating range. The Temperature economizer can continue to reduce the amount of mechanical cooling when the outside Air Temperature is above the cold Air discharge Temperature and below the change point Temperature, by using maximum outside Air [I]. Above the change point, as well as below the low Temperature set point, the economizer is disabled and minimum outside Air is used. There is also an enthalpy economizer, which works the same way, only the outside Air intake is determined by Air enthalpy rather than Temperature [2]. An additional sensor, measuring dew point Temperature or relative humidity, is required for enthalpy based control. Economizers can reduce the cooling energy significantly. However, the heating penalty may be higher than the cooling savings [5, 7, 81. Therefore, a careful analysis should be performed before its installation. Optimized hot and cold deck reset schedules are another energy conservation measure. Many dual duct VAV systems in operation today only reset the hot deck according to outside Air Temperature, leaving the cold deck set point constant. Hot and cold deck reset schedules optimized according to outside Air Temperature have been studied and documented by Liu et a1 [3,4]. Knowledge of outside Air dew point Temperature or relative humidity can further improve the operation schedule. In this paper, computer simulation was used to evaluate the econornjzer cycle and optimized hot and cold deck reset schedule energy conservation measures. The case building was modeled using AirModel, a steady state method simulation program first written in 1993 at the Energy Systems Laboratory, Texas A&M University [6]. Given hourly outside Air Temperature, outside Air relative humidity, measured heating energy consumption, and measured cooling energy consumption, AirModel simulated the building based on the building characteristics entered into the input file. Upon development of an accurate baseline model, the aforementioned energy conservation measures were each included into the model separately, with the results to be discussed. Building Description The building simulated in the case study is Harrington Education Tower (see Figure I) , at Texas A&M University, College Station. It is an eight story education building, and consists primarily of offices and other meeting rooms. ESL-HH-98-06-30 Proceedings of the Eleventh Symposium on Improving Building Systems in Hot and Humid Climates, Fort Worth, TX, June 1-2, 1998 It has a basement as well. There are an estimated 400 occupants, and the occupancy schedule is essentially 8 a.m. to 5 p.m., Monday through Friday. The overall building dimensions are 124 feet by 136 feet by 110 feet high. The first and second floor are 90 feet wide by 102 feet deep, and the eighth floor is 114 feet wide by 81 feet deep. Thereis 19,000 square feet of glazing, with 50% of it being on the first, second, and eighth floors, as they are predominantly glass sided. Harrington Tower receives hot and chilled water from the Texas A&M Physical Plant for its HVAC systems. The building received retrofit in 1995, from DDCAV system with pre-treated outside Air to DDVAV with Temperature economizer. The sole DDVAV Air handler unit (see Figure 2) is housed in the basement, with a 200 hp motor producing up to 138,000 cfm of Air for the second through eighth floors, as well as portions of the basement and first floor On the upper floors, the hot and cold supply ducts run through a central chase to ducting and then VAV terminal boxes. The first floor has three small constant volume single duct systems to meet its primary heating and cooling requirements. The control program for the VAV system has nighttime setback of Temperature and Figure 1. Harrington Tower on Texas A&M Air flow.
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An Advanced Economizer Controller for Dual Duct Air Handling Systems -with a Case Application
1996Co-Authors: Mingsheng Liu, David E. ClaridgeAbstract:penalty is expected when economizers are applied to dual-duct Air handling systems. The heating penalty can even be higher than the cooling savings when the hot Air flow is higher than the cold Air flow. To avoid the excessive heating penalty, advanced economizers are developed in this paper. The application of the advanced economizer has resulted in $7,00O/yr savings in one 95,000 ft2 school building since 1993. The impacts of cold and hot deck settings on the energy consumption are also discussed. INTRODUCTION economizer cycle is currently one of the most popular energy conservation measures for Air handling units (AHU) in buildings. There are two types of economizers, the Temperature economizer and the enthalpy economizer (I). The Temperature economizer maintains the mixed Air Temperature at the cold deck discharge Air Temperature when the outside Air Temperature is lower than the cold deck discharge Air Temperature. Consequently, the need for mechanical cooling is eliminated. When the outside Air Temperature is higher than the cold deck discharge Air Temperature, but lower than a change point Temperature which is generally a few degrees lower than the Return Air Temperature, the Temperature economizer uses maximum outside Air to minimize the mechanical cooling
Mouriya Nethaji - One of the best experts on this subject based on the ideXlab platform.
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Energy conservation in room Air conditioner unit by recovering cold energy from condensate
International Journal of Refrigeration, 2019Co-Authors: N. Nethaji, Tharves Mohideen, Mouriya NethajiAbstract:Abstract Cooling the room with Air Conditioner condensate drips is an energy saving measure. In tropical countries which have 70 to 80% Relative Humidity (RH) year round, the quantity of cool energy in the condensate is significant while room Air conditioners are on. These defrost drips at about 10–15 °C is circulated along the inner walls of the room through copper tubes that absorbs the heat from the room walls and reduces the infiltration load. This in turn pre cools the room Return Air that results in reduction of run time of the Air conditioner system, which ultimately reduces the energy consumption of the compressor. For given conditions of Air Conditioner(AC) unit, the condensate Temperature, the run time, the Return Air Temperature, supply Air Temperature and energy saved are tabulated and investigated before and after wall cooling using TEMPTROL Psychrometric software. The investigation reveals that around 6–8% energy savings are achieved through wall cooling.
G. Wei - One of the best experts on this subject based on the ideXlab platform.
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Choosing the Right Parameter for Single-Duct Constant Air Volume System Supply Air Temperature Reset
Journal of Architectural Engineering, 2005Co-Authors: G. Wei, W. D. Turner, David E. Claridge, Mingsheng LiuAbstract:To improve system efficiency under part-load conditions, the supply Air Temperature set point for a single-duct constant Air volume Air handling unit (AHU) system is often reset based on either Return Air Temperature or outside Air Temperature. Both reset strategies make engineering sense as long as the reset schedules are reasonable. Quite often the decision to use one over the other is made with the assumption that they will both achieve some energy savings. However, the impact of these two strategies on AHU energy consumption could be very different. An in-depth analysis and comparison of these two commonly used supply Air Temperature reset strategies for a single-duct constant Air volume system is presented in this paper. It is shown that the reset strategy based on outside Air Temperature is inherently better than that based on Return Air Temperature, with lower energy consumption and improved building comfort level.
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Single-Duct Constant Air Volume System Supply Air Temperature Reset: Using Return Air Temperature or Outside Air Temperature?
Architectural Engineering 2003, 2003Co-Authors: G. Wei, W. D. Turner, David E. Claridge, Mingsheng LiuAbstract:The supply Air Temperature set point for a singleduct constant Air volume Air handling unit (AHU) system is often reset based on either Return Air Temperature or outside Air Temperature in order to reduce simultaneous cooling and heating energy consumption. Both reset strategies make engineering sense as long as the reset schedules are reasonable. Quite often the decision to use one over the other is made with the assumption that they will all achieve some sorts of energy savings. However, the impact of these two strategies on AHU energy consumption could be very different. A comparison of these two commonly used supply Air Temperature reset strategies for a single-duct constant Air volume system is presented in this paper. It is shown that from either the building energy consumption or building comfort point of view, the reset strategy based on outside Air Temperature is inherently better than that based on Return Air Temperature. Significant amount of heating energy savings can be achieved by switching from Return Air Temperature based reset to outside Air Temperature based reset. The reset strategy can also benefit variable Air volume (VAV) AHUs. An improved supply Air Temperature set point reset control strategy is proposed by combining and staging the outside Air and Return Air Temperature based resets.
Kwang Ho Lee - One of the best experts on this subject based on the ideXlab platform.
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Influences of different operational configurations on combined effects of room Air stratification and thermal decay in UFAD system
Energy and Buildings, 2018Co-Authors: Byeongmo Seo, Sung Hyup Hong, Sanghun Yeon, Kwang Ho LeeAbstract:Abstract The non-insulated underfloor supply plenum and the heat gain of the cool supply Air into supply plenum results in significant magnitude of thermal decay defined as the supply Air Temperature rise. Eventually, these changes have influence on the room Air stratification, causing negative effects throughout whole system. Therefore, for the optimization of UFAD system, it is important to understand these fundamentals and relevant effects on the overall system operation. In this study, comparative analysis was conducted during cooling period using validated EnergyPlus model, after employing different operational configurations related to room Air stratification and thermal decay. The thermal behavior and cooling energy performance were analyzed by observing the convective heat transfer, thermal decay, Airflow, stratification among different operational configurations. As a result, it was observed that the existence of non-insulated supply plenum have influences on the thermal behavior in occupied zone, and the corresponding heat transfer has load reduction effect of the space by about 40%. However, there were still significant amounts of cooling energy consumption in the form of thermal decay despite the reduced cooling load, indicating that unintended and additional energy consumption was occurred in supply plenum. In addition, Return Air Temperature rise by the room Air stratification increased the cooling coil load. Eventually, these effects canceled each other out. As a result, compared to CBAD system, standard UFAD system consumed more electric energy by approximately 30%, and for fully-insulated UFAD system, 6% energy saving could be achieved.