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Discussion on refrigeration cycle for regenerative cryocoolers
13 Space heating and cooling transport, and that the COz emissions of dormitory residents are lower than those of students living in other situations. Practical methods for reducing student CO2 emissions are also examined.
03100791 Daylighting as a passive solar design strategy in tropical buildings: a case study of Malaysia Zain-Ahmed, A. et al. Energy Conversion and Management, 2002, 43, (13), 1725-1736. The use of daylighting in buildings and architecture is not new. Natural lighting became out of vogue due to the availability of cheap electricity, the predictability and the ability to control illumination levels due to artificial lighting. However, the alarm over rapid depletion of energy resources and the environmental effects of their applications have led designers to reuse daylighting strategies in buildings in order to minimize energy use for lighting and air conditioning as a result of heat gains from the daylight sources and the electrical fixtures. This paper describes a study on the savings achieved by using daylight in passive solar design of buildings and, in this case, the size of windows. Simulated exterior illuminance levels based on long-term measured solar irradiation and cloud cover data were used to estimate interior illumination on normal working planes using simple building configurations. Illumination on these planes decreases the need for artificial lighting, thus energy can be saved. A simple algorithm was then used to calculate the overall cooling load to ascertain that the daylighting strategies used do not invoke an increase in thermal gains through walls and glazings. The findings from this study show that at least 10% savings can be produced from simple daylighting strategies.
03100792 Design of stationary PEFC system configurations to meet heat and power demands Wallmark, C. and Alvfors, P. Journal o[Power Sources, 2002, 106, (12), 83-92. This paper presents heat and power efficiencies of a modelled Polymer electrolyte fuel cell (PEFC) system and the methods used to create the system configuration. The paper also includes an example of a simulated fuel cell system supplying a building in Sweden with heat and power. The main method used to create an applicable fuel cell system configuration is pinch technology. This technology is used to evaluate and design a heat exchanger network for a PEFC system working under stationary conditions, in order to find a solution with high heat utilization. The heat exchanger network in the system connecting the reformer, the burner, gas cleaning, hot-water storage and the PEFC stack will affect the heat transferred to the hot-water storage and thereby the heating of the building. The fuel, natural gas, is reformed to a hydrogen-rich gas within a slightly pressurized system. The fuel processor investigated is steam reforming, followed by highand low-temperature shift reactors and preferential oxidation. The system is connected to the electrical grid for backup and peak demands and to a hot-water storage to meet the varying heat demand for the building. The procedure for designing the fuel cell system installation as co-generation system is described, and the system is simulated for a specific building in Sweden during 1 year. The results show that the fuel cell system in combination with a burner and hot-water storage could supply the building with the required heat without exceeding any of the given limitations. The designed co-generation system will provide the building with most of its power requirements and would further generate income by sale of electricity to the power grid.
03/00793 Discussion on refrigeration cycle for regenerative cryocoolers Chert, G. et al. Cryogenics, 2002, 42, (2), 133-139. Thermodynamic cycle with two isentropic and two polytropic processes, which can achieve the Carnot value of thermodynamic efficiency, is developed on the basis of analysis of thermodynamic efficiency e of the Carnot cycle. Thermodynamically, efficiency expressions of a number of ideal regenerative refrigeration cycles are derived, including the ideal pulse tube refrigeration cycle. A classified branch chart and a plot of ideal thermodynamic efficiency of regenerative refrigeration cycles are given for the purpose of comparison.
03•00794 Durability, adaptability and energy conservation (DAEC) assessment tool Langford, D. A. el al. Int. J. Environmental Technology and Management, 2002, 2, (1/2/3), 142-159. This paper presents an evaluation tool assessing and the durability, adaptability and energy conservation of existing buildings and new building designs - DAEC Tool. The tool is one of outcomes of the research project 'Sustainability of Buildings: Durability, Adaptability and Energy Conservation'. The paper examines the issues which were the basis for developing the metrics, and the application of the DAEC Tool in the evaluation of selected higher education buildings and a new building design for a community hospital. The paper explains how the DAEC Tool can be used in building design and building management.
03100795 Experimental and theoretical analysis of natural ventilation by windows opening Fracastoro, G. V. et al. Energy and Buildings, 2002, 34, (8), 817-827. A number of simple models are available for the analysis of airing by window opening, but its transient behaviour is not yet well known, in terms of air change rates, air temperature and ventilation efficiency. In this paper, a synthesis of numerical modelling activity will be presented. A critical analysis of calculation procedures will be developed, comparing both detailed analysis results and simplified (zonal) models predictions. A comprehensive discussion of models limitations, features and applications is presented. Moreover, the performance of theoretical models will be compared with the experimental results obtained during a full-scale measurement campaign. Finally, a simplified procedure, based on charts and non-dimensional groups, is proposed in order to make available to the designers a quick calculation method to evaluate the ventilation rate through an open vertical window.
03100796 Experimental study on work flow in the pulse tube refrigerator Ikeguchi, T. et aL AlP Conference Proceedings, 2002, (613), 799-806. The variations in the P-V work and the enthalpy flow while gas flows through a regenerator ~,f a pulse tube refrigerator were investigated experimentally. The P-V work and the enthaipy flow were estimated from the data of the pressure, velocity, and temperature oscillations simultaneously measured at several positions along the regenerator. A hot wire anemometer was used for the velocity measurement. Differences in the P-V work and the enthalpy flow between those at the warm and cold ends of the regenerator were obtained as a function of orifice valve opening. The P-V work and the enthalpy flow at the warm end increase monotonically, but the differences increase to a maximum and then decrease with the increase of the valve opening. The maximum values of the differences were attained around the optimum opening where the temperature of the cold end reaches the lowest level, The average or net enthalpy flow at the middle of the regenerator during one cycle was also estimated. The enthalpy flow increases with the increase of the opening for small opening, while the rate of the increase becomes small for large valve opening.
03•00797 Further investigations of a new parameter to assess noise annoyance in air-conditioned buildings Ayr, U. et al. Energy' and Buildings, 2002, 34, (8), 765-774. At the conclusion of a noise annoyance survey in air-conditioned offices a new parameter was proposed. The aim was to define a noise index well correlated with subjective ratings of noise annoyance and able to account for the imbalance of the noise spectrum. As the RC Mark II procedure for rating the noise of HVAC systems in buildings introduced the 'quality assessment index' (QAI), which provides a measure of the spectral imbalance of a noise, the combination of this parameter with the RC criterion number (which only measures noise level) was proposed. In a previous paper, the combination factor that maximized the correlation was determined and a validation procedure was used to test the repeatability of the results. In this paper, a new procedure to calculate the mean subjective ratings has been introduced and more demanding procedures to test the repeatability of the results have been used. Finally, it was found that a combination factor varying in a range from 0.24 to 0.31 provided the highest correlation between the new parameter and the subjective sensation of annoyance.
03100798 Influence of quantum degeneracy on the performance of a Stirling refrigerator working with an ideal Fermi gas He, J. et al. Applied Energy, 2002, 72, (3-4), 541-554. The influence of quantum degeneracy on the performance of a Stirling refrigeration cycle is investigated, based on the equation of state of an ideal Fermi gas. The inherent regenerative losses and the coefficient of performance (COP) of the cycle are calculated. It is found that, under the condition of strong gas degeneracy, the COP of the cycle in the first approximation is a function only of the temperatures of the heat reservoirs, while under other conditions, the COPs of the cycle depend on the temperatures of the heat reservoirs and other parameters of the cycle. The results obtained here reveal the general performance characteristics of a Stirling refrigeration cycle having a Fermi gas as its working substance.
03100799 Influence of sensor position in building thermal control: criteria for zone models Riederer, P. et al. Energy and Buildings, 2002, 34, (8), 785-798. This paper presents modelling choices adapted to the study of the influence of the sensor position in building thermal control. The model is implemented in a toolbox of dynamic models of heating, ventilation, air conditioning (HVAC) components. It must be suitable for the optimization and the test of controllers and control strategies by simulation and emulation. Due to the convective coupling between the zone and its particular HVAC system, the temperature measured by
Fuel and Energy Abstracts
March 2003
105
03100791 Daylighting as a passive solar design strategy in tropical buildings: a case study of Malaysia Zain-Ahmed, A. et al. Energy Conversion and Management, 2002, 43, (13), 1725-1736. The use of daylighting in buildings and architecture is not new. Natural lighting became out of vogue due to the availability of cheap electricity, the predictability and the ability to control illumination levels due to artificial lighting. However, the alarm over rapid depletion of energy resources and the environmental effects of their applications have led designers to reuse daylighting strategies in buildings in order to minimize energy use for lighting and air conditioning as a result of heat gains from the daylight sources and the electrical fixtures. This paper describes a study on the savings achieved by using daylight in passive solar design of buildings and, in this case, the size of windows. Simulated exterior illuminance levels based on long-term measured solar irradiation and cloud cover data were used to estimate interior illumination on normal working planes using simple building configurations. Illumination on these planes decreases the need for artificial lighting, thus energy can be saved. A simple algorithm was then used to calculate the overall cooling load to ascertain that the daylighting strategies used do not invoke an increase in thermal gains through walls and glazings. The findings from this study show that at least 10% savings can be produced from simple daylighting strategies.
03100792 Design of stationary PEFC system configurations to meet heat and power demands Wallmark, C. and Alvfors, P. Journal o[Power Sources, 2002, 106, (12), 83-92. This paper presents heat and power efficiencies of a modelled Polymer electrolyte fuel cell (PEFC) system and the methods used to create the system configuration. The paper also includes an example of a simulated fuel cell system supplying a building in Sweden with heat and power. The main method used to create an applicable fuel cell system configuration is pinch technology. This technology is used to evaluate and design a heat exchanger network for a PEFC system working under stationary conditions, in order to find a solution with high heat utilization. The heat exchanger network in the system connecting the reformer, the burner, gas cleaning, hot-water storage and the PEFC stack will affect the heat transferred to the hot-water storage and thereby the heating of the building. The fuel, natural gas, is reformed to a hydrogen-rich gas within a slightly pressurized system. The fuel processor investigated is steam reforming, followed by highand low-temperature shift reactors and preferential oxidation. The system is connected to the electrical grid for backup and peak demands and to a hot-water storage to meet the varying heat demand for the building. The procedure for designing the fuel cell system installation as co-generation system is described, and the system is simulated for a specific building in Sweden during 1 year. The results show that the fuel cell system in combination with a burner and hot-water storage could supply the building with the required heat without exceeding any of the given limitations. The designed co-generation system will provide the building with most of its power requirements and would further generate income by sale of electricity to the power grid.
03/00793 Discussion on refrigeration cycle for regenerative cryocoolers Chert, G. et al. Cryogenics, 2002, 42, (2), 133-139. Thermodynamic cycle with two isentropic and two polytropic processes, which can achieve the Carnot value of thermodynamic efficiency, is developed on the basis of analysis of thermodynamic efficiency e of the Carnot cycle. Thermodynamically, efficiency expressions of a number of ideal regenerative refrigeration cycles are derived, including the ideal pulse tube refrigeration cycle. A classified branch chart and a plot of ideal thermodynamic efficiency of regenerative refrigeration cycles are given for the purpose of comparison.
03•00794 Durability, adaptability and energy conservation (DAEC) assessment tool Langford, D. A. el al. Int. J. Environmental Technology and Management, 2002, 2, (1/2/3), 142-159. This paper presents an evaluation tool assessing and the durability, adaptability and energy conservation of existing buildings and new building designs - DAEC Tool. The tool is one of outcomes of the research project 'Sustainability of Buildings: Durability, Adaptability and Energy Conservation'. The paper examines the issues which were the basis for developing the metrics, and the application of the DAEC Tool in the evaluation of selected higher education buildings and a new building design for a community hospital. The paper explains how the DAEC Tool can be used in building design and building management.
03100795 Experimental and theoretical analysis of natural ventilation by windows opening Fracastoro, G. V. et al. Energy and Buildings, 2002, 34, (8), 817-827. A number of simple models are available for the analysis of airing by window opening, but its transient behaviour is not yet well known, in terms of air change rates, air temperature and ventilation efficiency. In this paper, a synthesis of numerical modelling activity will be presented. A critical analysis of calculation procedures will be developed, comparing both detailed analysis results and simplified (zonal) models predictions. A comprehensive discussion of models limitations, features and applications is presented. Moreover, the performance of theoretical models will be compared with the experimental results obtained during a full-scale measurement campaign. Finally, a simplified procedure, based on charts and non-dimensional groups, is proposed in order to make available to the designers a quick calculation method to evaluate the ventilation rate through an open vertical window.
03100796 Experimental study on work flow in the pulse tube refrigerator Ikeguchi, T. et aL AlP Conference Proceedings, 2002, (613), 799-806. The variations in the P-V work and the enthalpy flow while gas flows through a regenerator ~,f a pulse tube refrigerator were investigated experimentally. The P-V work and the enthaipy flow were estimated from the data of the pressure, velocity, and temperature oscillations simultaneously measured at several positions along the regenerator. A hot wire anemometer was used for the velocity measurement. Differences in the P-V work and the enthalpy flow between those at the warm and cold ends of the regenerator were obtained as a function of orifice valve opening. The P-V work and the enthalpy flow at the warm end increase monotonically, but the differences increase to a maximum and then decrease with the increase of the valve opening. The maximum values of the differences were attained around the optimum opening where the temperature of the cold end reaches the lowest level, The average or net enthalpy flow at the middle of the regenerator during one cycle was also estimated. The enthalpy flow increases with the increase of the opening for small opening, while the rate of the increase becomes small for large valve opening.
03•00797 Further investigations of a new parameter to assess noise annoyance in air-conditioned buildings Ayr, U. et al. Energy' and Buildings, 2002, 34, (8), 765-774. At the conclusion of a noise annoyance survey in air-conditioned offices a new parameter was proposed. The aim was to define a noise index well correlated with subjective ratings of noise annoyance and able to account for the imbalance of the noise spectrum. As the RC Mark II procedure for rating the noise of HVAC systems in buildings introduced the 'quality assessment index' (QAI), which provides a measure of the spectral imbalance of a noise, the combination of this parameter with the RC criterion number (which only measures noise level) was proposed. In a previous paper, the combination factor that maximized the correlation was determined and a validation procedure was used to test the repeatability of the results. In this paper, a new procedure to calculate the mean subjective ratings has been introduced and more demanding procedures to test the repeatability of the results have been used. Finally, it was found that a combination factor varying in a range from 0.24 to 0.31 provided the highest correlation between the new parameter and the subjective sensation of annoyance.
03100798 Influence of quantum degeneracy on the performance of a Stirling refrigerator working with an ideal Fermi gas He, J. et al. Applied Energy, 2002, 72, (3-4), 541-554. The influence of quantum degeneracy on the performance of a Stirling refrigeration cycle is investigated, based on the equation of state of an ideal Fermi gas. The inherent regenerative losses and the coefficient of performance (COP) of the cycle are calculated. It is found that, under the condition of strong gas degeneracy, the COP of the cycle in the first approximation is a function only of the temperatures of the heat reservoirs, while under other conditions, the COPs of the cycle depend on the temperatures of the heat reservoirs and other parameters of the cycle. The results obtained here reveal the general performance characteristics of a Stirling refrigeration cycle having a Fermi gas as its working substance.
03100799 Influence of sensor position in building thermal control: criteria for zone models Riederer, P. et al. Energy and Buildings, 2002, 34, (8), 785-798. This paper presents modelling choices adapted to the study of the influence of the sensor position in building thermal control. The model is implemented in a toolbox of dynamic models of heating, ventilation, air conditioning (HVAC) components. It must be suitable for the optimization and the test of controllers and control strategies by simulation and emulation. Due to the convective coupling between the zone and its particular HVAC system, the temperature measured by
Fuel and Energy Abstracts
March 2003
105