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02255 The influence of wind speed, terrain and ventilation system on the air change rate of a single-family house
10 Space heating and cooling~heat pumps higher coefficient of performance and a lower rate of exergy destruction per unit capacity. It is also possible to improve the heating mode performance of the system by redesigning the indoor coil, using another refrigerant with a higher heat rejection rate in the condenser and employing a better heat source such as the engine coolant or exhaust gases.
06102248 Refrigerant 134a liquid flow through micro-scale short tube orifices with/without phase change Tu, X. et al. E,;perimel~tal Thermal and Fluid Science, 2006, 30, (3), 253-262. The paper presents the results of experiments when R134a was flowing through micro-orifices with diameters of 31.0 and 52.0 gm, and lengthto-diameter ratio of 2.5 and 4.2, respectively. For liquid-upstream/ liquid-downstream flow, the discharge coefficient was found to be independent of Reynolds number, which suggests separated flow that was defined in macro-scale orifices. For liquid-upstream/two-phasedownstream flow, the experimental results indicate significant departure of flow characteristics from macro-scale orifices. The flow was not choked even when the downstream pressure was reduced to more than 400.0 kPa below the saturation pressure corresponding to upstream temperature, whereas in normal size orifices with length-to-diameter ratio larger than two, the flow is typically choked as downstream pressure ~s reduced below the saturation pressure. This phenomenon was explained by the strengthening of metastable effect in micro-tubes. For liquid-upstream/two-phase-downstream flow, a semi-empirical correlation was developed by modifying the discharge coefficient of the conventional orifice equation.
06/02249 Refrigerant pressure drop in chevron and bumpy style flat plate heat exchangers Jassim, E. W. et al. Experimental Thermal and Fluid Science, 2006, 30, (3), 213-222. Adiabatic pressure drop in chevron and two styles of bumpy plate heat exchangers were investigated for vertical upward flow with R134a. Qualities ranging from sub-cooled liquid to superheated vapour were investigated. Mass fluxes ranged from 16 kg/m2 s (for superheated vapour) to approximately 300 kg/m 2 s (for sub-cooled liquid). The pressure drop experiments were conducted for 10~C and 20°C inlet temperatures. A two-phase pressure drop model, based on the kinetic energy of the flow, was developed in order to relate the two-phase pressure drop data to the single-phase data. The model predicts twophase pressure drop within 15% of experimental measurements.
06102250 Renewable energy for passive house heating. Model of the active solar heating system Badescu, V. and Dan Staicovici, M. Energy and Buildings, 2006, 38, (2), 129 141. The large windows on the south-oriented facade of a passive house strongly contribute to building space heating. These windows constitute the passive solar heating system. This paper studies the active heating system of a passive house, which includes the following sub-systems: (1) solar thermal collectors, (2) a water storage tank, (3) a secondary water circuit, (4) a domestic hot water preparation system and (5) an air ventilation and heating system. Models for all sub-systems are presented. The integrated model was implemented to Pirmasens Passive House (Rhineland Palatinate, Germany). The active solar heating system provides a smaller amount of heat than the heat provided by the passive solar heating system. Almost all the solar energy collected is not used for space heating but to domestic hot water (DHW) preparation. However, there is still a need for the classical water heater to operate all over the year. Almost all space heating thermal load is covered by using the classical air heater that operates mainly during the nights from November to April. The solar fraction lies between 0.180 in February and 0.679 in October, with a yearly average of 0.446. The study reveals that on a yearly basis it is more advantageous to use vertical south-oriented solar collectors instead of roof placed collectors.
06/02251 south
Study of thermal behaviour of clay wall facing
Collet, F. et al. Building and Environment, 2006, 41, (3), 307-315. Sustainable development includes socio-economic and environmental targets and concerns all sectors of human activity. The main reasons for green building are to reduce energy consumption, green house gases emission, water use, waste production etc. The choice of materials used for the construction of a building has a direct impact on the environment. A material with a low life-cycle cost (LCC) and high technical performance reduces the impact of the building on the enviromnent. Cob is a traditional material with a low LCC; its thermal performances are studied here and compared with the thermal performances of stone walls and of insulated concrete block walls. A first type of simulation concerns a wall model with an interior temperature set at 19°C and a second type of simulation concerns a whole building, the wall model is then coupled with a zone model.
344
Fuel and Energy Abstracts
September 2006
Three types of buildings are simulated: a conventional building and two efficient buildings. One of the efficient buildings is a block of flats that is part of the European programme CEPHEUS: Salvatierra. The simulations show that, for south-facing walls, the thermal behaviour of a 50-cm-thick cob wall is about the same as that of insulated concrete blocks wall with 7.5 cm of insulation. With a 5-cm-thick insulation added, the thermal behaviour of a south-facing cob wail is then about the same as that of an insulated dense concrete block wall with 15 cm of insulation. Cob is, thus, a traditional material that can be used in modern constructions.
06/02252 The application of photo-coupler for frost detecting in an air-source heat pump Byun, J.-s. et al. International Journal of Refrigeration, 2006, 29, (2), 191 198. This experimental study is carried out to investigate reliability and effectiveness of a new method of using photo-coupler for detecting frost formation in an air source heat pump, and further to determine the most efficient initiation point of the defrost cycle. This new method of using photo-coupler as a frost sensing device is evaluated by comparing its performance with conventional time control defrost system in which defrost cycle is set to start at predetermined interval, e.g. about at every 1-1.5 h. Results indicate that overall heating capacity of photo-coupler detection method (case IV) is 5.5% higher than that of time control method. It is also shown that for maximum efficiency the defrost cycle must be initiated before the frost build-up area exceeds 45% of total front surface of the outdoor coil.
06•02253 The cooling potential of earth-air heat exchangers for domestic buildings in a desert climate A1-Ajmi, F. et al. Building and Environment, 2006, 41, (3), 235 244. A theoretical model of an earth-air heat exchanger (EAHE) is developed for predicting the outlet air temperature and cooling potential of these devices in a hot, arid climate. The model is validated against other published models and shows good agreement. A sub-soil temperature model adapted for the specific conditions in Kuwait is presented and its output compared with measurements in two locations. A building model representative of a typical Kuwaiti dwelling has been implemented and all the models have been encoded within the TRNSYS-IISIBAT environment. A typical meteorological year for Kuwait was prepared and used to predict the cooling loads of the airconditioned dwelling with and without the assistance of the EAHE. Simulation results showed that the EAHE could provide a reduction of 1700 W in the peak cooling load, with an indoor temperature reduction of 2.8°C during summer peak hours (middle of July). The EAHE is shown to have the potential for reducing cooling energy demand in a typical house by 30% over the peak summer season.
06102254 The effect of Trombe wall on indoor humid climate in Dalian, China Chen, B. et al. Renewable Energy, 2006, 31, (3), 333 343. The paper clarified the effect of humidity adjustment of Trombe wall on indoor environment by the experimental comparison between a passive solar cell and a reference cell. Theoretical analysis on indoor humidity adjustment of Trombe wall in the passive solar cell is also performed based on steady moisture transfer theory. Simultaneously, the experiment proved that the passive solar cell could provide a relatively comfortable indoor environment.
06/02255 The influence of wind speed, terrain and ventilation system on the air change rate of a single-family house Mattsson, B. Energy, 2006, 31, (5), 719 731. When the heat balance of a building is assessed, the heat needed for the ventilation air is usually calculated according to the intended ventilation rate. However, in order to calculate the air change rate accurately several aspects have to be considered. One important parameter is the ventilation system. Whether the building has a mechanical exhaust-only, supply-only, balanced exhaust-supply or natural ventilation system will influence the air infiltration rate through cracks in the building envelope. High infiltration rates lead to an increase in the heating demand and can result in an inadequate capacity of the designed heating installation. In this paper, computer simulations of the air change rate for a detached single-family house are presented. The house is simulated in different topographical surroundings, equipped with a mechanical exhaust-only, or a balanced exhaust-supply, ventilation system. In addition, the airtightness of the building is varied, from very tight, 1 air change per hour (ACH), to quite leaky, 6 ACH, when pressurized to 50 Pa. Results from the simulations show that the same house has quite different air change rates in different surroundings with different airtightness.
06•02256
Thermal integration of trigeneration systems
Calva, E. T. et al. Applied Thermal Engineering, 2005, 25, (7), 973 984.
06102248 Refrigerant 134a liquid flow through micro-scale short tube orifices with/without phase change Tu, X. et al. E,;perimel~tal Thermal and Fluid Science, 2006, 30, (3), 253-262. The paper presents the results of experiments when R134a was flowing through micro-orifices with diameters of 31.0 and 52.0 gm, and lengthto-diameter ratio of 2.5 and 4.2, respectively. For liquid-upstream/ liquid-downstream flow, the discharge coefficient was found to be independent of Reynolds number, which suggests separated flow that was defined in macro-scale orifices. For liquid-upstream/two-phasedownstream flow, the experimental results indicate significant departure of flow characteristics from macro-scale orifices. The flow was not choked even when the downstream pressure was reduced to more than 400.0 kPa below the saturation pressure corresponding to upstream temperature, whereas in normal size orifices with length-to-diameter ratio larger than two, the flow is typically choked as downstream pressure ~s reduced below the saturation pressure. This phenomenon was explained by the strengthening of metastable effect in micro-tubes. For liquid-upstream/two-phase-downstream flow, a semi-empirical correlation was developed by modifying the discharge coefficient of the conventional orifice equation.
06/02249 Refrigerant pressure drop in chevron and bumpy style flat plate heat exchangers Jassim, E. W. et al. Experimental Thermal and Fluid Science, 2006, 30, (3), 213-222. Adiabatic pressure drop in chevron and two styles of bumpy plate heat exchangers were investigated for vertical upward flow with R134a. Qualities ranging from sub-cooled liquid to superheated vapour were investigated. Mass fluxes ranged from 16 kg/m2 s (for superheated vapour) to approximately 300 kg/m 2 s (for sub-cooled liquid). The pressure drop experiments were conducted for 10~C and 20°C inlet temperatures. A two-phase pressure drop model, based on the kinetic energy of the flow, was developed in order to relate the two-phase pressure drop data to the single-phase data. The model predicts twophase pressure drop within 15% of experimental measurements.
06102250 Renewable energy for passive house heating. Model of the active solar heating system Badescu, V. and Dan Staicovici, M. Energy and Buildings, 2006, 38, (2), 129 141. The large windows on the south-oriented facade of a passive house strongly contribute to building space heating. These windows constitute the passive solar heating system. This paper studies the active heating system of a passive house, which includes the following sub-systems: (1) solar thermal collectors, (2) a water storage tank, (3) a secondary water circuit, (4) a domestic hot water preparation system and (5) an air ventilation and heating system. Models for all sub-systems are presented. The integrated model was implemented to Pirmasens Passive House (Rhineland Palatinate, Germany). The active solar heating system provides a smaller amount of heat than the heat provided by the passive solar heating system. Almost all the solar energy collected is not used for space heating but to domestic hot water (DHW) preparation. However, there is still a need for the classical water heater to operate all over the year. Almost all space heating thermal load is covered by using the classical air heater that operates mainly during the nights from November to April. The solar fraction lies between 0.180 in February and 0.679 in October, with a yearly average of 0.446. The study reveals that on a yearly basis it is more advantageous to use vertical south-oriented solar collectors instead of roof placed collectors.
06/02251 south
Study of thermal behaviour of clay wall facing
Collet, F. et al. Building and Environment, 2006, 41, (3), 307-315. Sustainable development includes socio-economic and environmental targets and concerns all sectors of human activity. The main reasons for green building are to reduce energy consumption, green house gases emission, water use, waste production etc. The choice of materials used for the construction of a building has a direct impact on the environment. A material with a low life-cycle cost (LCC) and high technical performance reduces the impact of the building on the enviromnent. Cob is a traditional material with a low LCC; its thermal performances are studied here and compared with the thermal performances of stone walls and of insulated concrete block walls. A first type of simulation concerns a wall model with an interior temperature set at 19°C and a second type of simulation concerns a whole building, the wall model is then coupled with a zone model.
344
Fuel and Energy Abstracts
September 2006
Three types of buildings are simulated: a conventional building and two efficient buildings. One of the efficient buildings is a block of flats that is part of the European programme CEPHEUS: Salvatierra. The simulations show that, for south-facing walls, the thermal behaviour of a 50-cm-thick cob wall is about the same as that of insulated concrete blocks wall with 7.5 cm of insulation. With a 5-cm-thick insulation added, the thermal behaviour of a south-facing cob wail is then about the same as that of an insulated dense concrete block wall with 15 cm of insulation. Cob is, thus, a traditional material that can be used in modern constructions.
06/02252 The application of photo-coupler for frost detecting in an air-source heat pump Byun, J.-s. et al. International Journal of Refrigeration, 2006, 29, (2), 191 198. This experimental study is carried out to investigate reliability and effectiveness of a new method of using photo-coupler for detecting frost formation in an air source heat pump, and further to determine the most efficient initiation point of the defrost cycle. This new method of using photo-coupler as a frost sensing device is evaluated by comparing its performance with conventional time control defrost system in which defrost cycle is set to start at predetermined interval, e.g. about at every 1-1.5 h. Results indicate that overall heating capacity of photo-coupler detection method (case IV) is 5.5% higher than that of time control method. It is also shown that for maximum efficiency the defrost cycle must be initiated before the frost build-up area exceeds 45% of total front surface of the outdoor coil.
06•02253 The cooling potential of earth-air heat exchangers for domestic buildings in a desert climate A1-Ajmi, F. et al. Building and Environment, 2006, 41, (3), 235 244. A theoretical model of an earth-air heat exchanger (EAHE) is developed for predicting the outlet air temperature and cooling potential of these devices in a hot, arid climate. The model is validated against other published models and shows good agreement. A sub-soil temperature model adapted for the specific conditions in Kuwait is presented and its output compared with measurements in two locations. A building model representative of a typical Kuwaiti dwelling has been implemented and all the models have been encoded within the TRNSYS-IISIBAT environment. A typical meteorological year for Kuwait was prepared and used to predict the cooling loads of the airconditioned dwelling with and without the assistance of the EAHE. Simulation results showed that the EAHE could provide a reduction of 1700 W in the peak cooling load, with an indoor temperature reduction of 2.8°C during summer peak hours (middle of July). The EAHE is shown to have the potential for reducing cooling energy demand in a typical house by 30% over the peak summer season.
06102254 The effect of Trombe wall on indoor humid climate in Dalian, China Chen, B. et al. Renewable Energy, 2006, 31, (3), 333 343. The paper clarified the effect of humidity adjustment of Trombe wall on indoor environment by the experimental comparison between a passive solar cell and a reference cell. Theoretical analysis on indoor humidity adjustment of Trombe wall in the passive solar cell is also performed based on steady moisture transfer theory. Simultaneously, the experiment proved that the passive solar cell could provide a relatively comfortable indoor environment.
06/02255 The influence of wind speed, terrain and ventilation system on the air change rate of a single-family house Mattsson, B. Energy, 2006, 31, (5), 719 731. When the heat balance of a building is assessed, the heat needed for the ventilation air is usually calculated according to the intended ventilation rate. However, in order to calculate the air change rate accurately several aspects have to be considered. One important parameter is the ventilation system. Whether the building has a mechanical exhaust-only, supply-only, balanced exhaust-supply or natural ventilation system will influence the air infiltration rate through cracks in the building envelope. High infiltration rates lead to an increase in the heating demand and can result in an inadequate capacity of the designed heating installation. In this paper, computer simulations of the air change rate for a detached single-family house are presented. The house is simulated in different topographical surroundings, equipped with a mechanical exhaust-only, or a balanced exhaust-supply, ventilation system. In addition, the airtightness of the building is varied, from very tight, 1 air change per hour (ACH), to quite leaky, 6 ACH, when pressurized to 50 Pa. Results from the simulations show that the same house has quite different air change rates in different surroundings with different airtightness.
06•02256
Thermal integration of trigeneration systems
Calva, E. T. et al. Applied Thermal Engineering, 2005, 25, (7), 973 984.