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03939 Enhancement of convective heat transfer in ribroughened rectangular ducts
13
conventional CHP system may be practically applied. It has also been shown that compared to the traditional supermarket design, the proposed CHP system will use slightly less primary energy and the running costs will be significantly reduced. An attractive payback period of approximately 4 years has been calculated. Despite these advantages a considerable quantity of heat is rejected to atmosphere with this system and this is because the configuration utilizes the heat mainly for space heating which is only required for part of the year. To increase the utilization time, a novel CHP/ absorption system has been investigated. This configuration provides a continuous demand for the waste heat, which is used to drive an absorption chiller that refrigerates propylene glycol to -10°C for cooling the chilledfood cabinets. The results show this concept to be theoretically practical. The system has also been shown to be extremely efficient, with primary energy savings of approximately 20%, when compared to traditional supermarket designs and this would result in significant revenue cost savings as well as environmental benefits. Based upon these savings, a payback period for this system of approximately five years has been demonstrated.
Space
heating
and cooling
temperature (SET) within one scale error of thermal sensation. Small air movement with the radiant cooling system had a possibility of improving the comfortable sensation votes in the radiant cooling.
Energy and peak power savings potentlai of radiant cooling systems in US commercial buildings
99103938
Stetiu, C. Energy and Buildings, 1999, 30, (2). 127-138. Developed to estimate the energy and peak power savings potential of radiant cooling systems in commercial buildings in the USA, a parametric study is presented in this work. The study is based on the numerical modelling of a radiant cooling system and an all-air system at different locations in the USA. The results show that a building eauiDoed with a radiant cooling system can be operated in any US climate \;ith ‘low risk of condensation. For the office space examined in the study, employing a radiant cooling system instead of a traditional all-air system can save on average 30% of the energy consumption and 27% of the peak power demand due to space conditioning. The savings potential is climatedependent, and is larger in retrofitted buildings than in new construction.
Enhancement of convective heat transfer in rlbroughened rectangular ducts
99103934
99103939
In recent years. eiector refrigeration svstems have attracted manv research activities. ?hese sistems tra&tionally dperate with water as refrigerant with low COP values. Other refrigerants commonly used in mechanical vapour compression cycles may provide better performance for ejector refrigeration cycles. Eleven refrigerants, including water, halocarbon compounds (CFCs, HCFCs and HFCs), a cyclic organic compound and an azeotrope, were chosen as working fluids in an ejector refrigeration system and their performances compared. The results show that steam jet systems have very low COP values, the system using R152a as refrigerant has better performance and the variation in COP values for various refrigerants is almost independent of system operating conditions.
SundCn, B. Enhanced Heat Transfer, 1999, 6, (2-4), 89-103. In many engineering applications, enhancement of forced convection is important. Surface modifications like rib-roughening are commonly used in applications such as compact heat exchangers and cooling systems in gasturbine systems. Flow fields, friction factors and local and average heat transfer coefficients in rib-roughened ducts of the type appearyng are considered, here. Both experimental and numerical investigations are discussed. Details of the flow pattern and the influence of rib configuration, rib angle, rib pitch and rib height are discussed and physical interpretation of the results are provided. Some general conclusions are provided but it is also found that accurate numerical modelling of the flow and heat transfer from ribbed surfaces is difficult. Suggestions for further research are given.
Comparative study of the performance of an ejector refrigeration cycle operating with various refrigerants Sun,D.-W. Ener# Convers. Manage., 1999, 40, (S), 873-884.
Enhancement of heat transfer by turbulent decavina -~ --#~ swirl flaw
99103940
Dehumidifying chilled radiator system for hot and humid climates
99103935
Hirayama, Y. and Batty, W. J. Energy and Buildings, 1999, 30, (2), 203210. The paper investigates the application of room radiators for the purposes of cooling and dehumidification in buildings for hot and humid climates. The radiator is purposely brought below the dew point temperature of the room air thereby creating condensation on the radiator surface. The condensate is then collected at the base of the radiator and removed. A mathematical model describing the heat transfer regime within a room when this system is used has been verified using climate chamber tests. Results show the importance of the radiant transfer component for thermal comfort and suggests that more emphasis should be placed on this aspect during design. Furthermore, the possibilities for the chilled radiator system as an alternative to convdntional air conditioning systems by pa&ally or fully matching the sensible and latent component of the radiator output to the load requirements of a building is discussed. Since the temperature difference between the air and the radiator surface is small in this cooling application, larger surface areas are required than usual for the heating application. However, it means that the hot water temperature can be reduced for the heating mode. This allows the use of heat pumps to provide both hot and cold water at higher coefficients of performance than normally achievable. 99103936 Economic viability of cooling ceiling systems Sodec, F. Energy and Buildings, 1999, 30, (2), 195-201. Applying the numerical simulation program TRNSYS, the energy costs of a VAV system and a cooling ceiling system have been compared. The initial costs and the space requirements for the plants have also been collated. The cooling ceiling system was combined by the mechanical ventilation for the supply of outside air rate. Several parameters were varied to determine their influence on costs. A cooling ceiling system incurs lower energy costs and space requirements than VAV systems. Concerning the initial costs there is a break even point at a specific cooling load of 45-55 W m-*. At higher cooling loads, the first costs of a cooling ceiling system are more favourable.
Effect of humidity and small air movement on thermal comfort under a radiant cooling ceiling by subjective experiments
99103937
Kitagawa, K. et al. Energy and Buildings, 1999, 30, (2), 185-193. In comparison to the more frequently used convective air conditioning systems, radiant air-conditioning is expected to be more comfortable and have superior energy-savings. The objective of this study is to investigate the thermal comfort of local parts of the body and the whole body, in particular, including the effects of humidity and small air movements, by subjective experiments under a radiant cooling system. The experiments have been performed by using radiant cooling panels in a climate chamber. Subjects were seated on a chair under the radiant cooling panels, and voted their thermal sensation and comfortable sensation. The following results were obtained. Even in the radiant cooling system, the influence of humidity and small air movement on thermal sensation votes of the whole body could be correctly estimated by using a standard new effective
~G.
-
Yilmaz, M. et al. Energy Comers. Manage., 1999, 40, (13). 1365-1376. An experimental investigation was carried out on the heat transfer and friction characteristics of a decaying swirl flow. The swirling motion of the air was uroduced bv a radial euide vane swirl eenerator. The vanes of the swirl geherator we;e designeYd to be adjustable to obtain different swirl intensities. Different guide vane angles were used for the swirling flow experiments. The results were correlated in the form of Nusselt number as a function of Reynolds number, Prandtl number and the vane angle as Nu = 0.133Re”.h5Pr”.4(1 + tan )” 4”h. An augmentation of up to 98% in Nusselt number was obtained in the decaying swirl flow depending upon the Reynolds number and the vane angle. It was found that the performance of swirling flow is higher than corresponding axial flow with high vane angles and relatively low Reynolds numbers. 99103941 Estimation and measurement of electric energy consumption due to air conditioning cooling load Al-Rabghi, 0. M. et al. Energy Comers. Manage., 1999, 40, (14). 15271542. Due to air conditioning in buildings, electric energy consumption is tremendous. esoeciallv in nlaces havine hot humid weather. such as Jeddah. Saudi Arabia. ‘Building simulation pr&rammes, such as DOE2, are ve; valuable tools for studying building energy consumption under different conditions. These programmes can be used to investigate the effect of different building designs on their energy consumption. This paper presents the experimental and theoretical variations of electric power consumed by an air conditioning system. For the experimental part, a building has been chosen, and different sensors were installed to measure and record electric kW consumption at different indoor and outdoor conditions. In the theoretical part, the Visual DOE simulation programme, which is based on the well known DOE2E programme, has been used. Actual building data was fed to the programme to generate the instantaneous electric consumption due to air conditioning cooling load. Comparison between measured and predicted electric consumptions is presented.
Experimental analysis of a condenser heat recovery in an air condittoning plant
99103942
Schibuola, L. Energy, 1999, 24, (4), 273-283. The performance of a total heat recovery system was analysed by monitoring building-plant system long-term behaviour. Some of the installed chillers offer the possibility of a total recovery of the heat rejected by condenser. The results are very satisfactory both in energy and economic-financial terms. The experimental test takes advantage of the supervisor just existing in the building. Therefore it is an example of how these control systems can be used not only for safety and management needs, but also for a detailed performance analysis able to permit an easy simulation of the effects of different design and control options.
An experimental study of multiple parameter switching control for radiant floor heating systems
99103943
Cho, S.-H. and Zaheer-uddin, M. Energy, 1999, 24, (5), 433-444. Consisting of two identical 3 x 4.4 x 3.8 m3 rooms, an experimental facility was built; each room has a gas-fired boiler supplying hot water to the radiant-floor heating system. An electrically heated storage tank installed in
Fuel and Energy Abstracts
November 1999 413
conventional CHP system may be practically applied. It has also been shown that compared to the traditional supermarket design, the proposed CHP system will use slightly less primary energy and the running costs will be significantly reduced. An attractive payback period of approximately 4 years has been calculated. Despite these advantages a considerable quantity of heat is rejected to atmosphere with this system and this is because the configuration utilizes the heat mainly for space heating which is only required for part of the year. To increase the utilization time, a novel CHP/ absorption system has been investigated. This configuration provides a continuous demand for the waste heat, which is used to drive an absorption chiller that refrigerates propylene glycol to -10°C for cooling the chilledfood cabinets. The results show this concept to be theoretically practical. The system has also been shown to be extremely efficient, with primary energy savings of approximately 20%, when compared to traditional supermarket designs and this would result in significant revenue cost savings as well as environmental benefits. Based upon these savings, a payback period for this system of approximately five years has been demonstrated.
Space
heating
and cooling
temperature (SET) within one scale error of thermal sensation. Small air movement with the radiant cooling system had a possibility of improving the comfortable sensation votes in the radiant cooling.
Energy and peak power savings potentlai of radiant cooling systems in US commercial buildings
99103938
Stetiu, C. Energy and Buildings, 1999, 30, (2). 127-138. Developed to estimate the energy and peak power savings potential of radiant cooling systems in commercial buildings in the USA, a parametric study is presented in this work. The study is based on the numerical modelling of a radiant cooling system and an all-air system at different locations in the USA. The results show that a building eauiDoed with a radiant cooling system can be operated in any US climate \;ith ‘low risk of condensation. For the office space examined in the study, employing a radiant cooling system instead of a traditional all-air system can save on average 30% of the energy consumption and 27% of the peak power demand due to space conditioning. The savings potential is climatedependent, and is larger in retrofitted buildings than in new construction.
Enhancement of convective heat transfer in rlbroughened rectangular ducts
99103934
99103939
In recent years. eiector refrigeration svstems have attracted manv research activities. ?hese sistems tra&tionally dperate with water as refrigerant with low COP values. Other refrigerants commonly used in mechanical vapour compression cycles may provide better performance for ejector refrigeration cycles. Eleven refrigerants, including water, halocarbon compounds (CFCs, HCFCs and HFCs), a cyclic organic compound and an azeotrope, were chosen as working fluids in an ejector refrigeration system and their performances compared. The results show that steam jet systems have very low COP values, the system using R152a as refrigerant has better performance and the variation in COP values for various refrigerants is almost independent of system operating conditions.
SundCn, B. Enhanced Heat Transfer, 1999, 6, (2-4), 89-103. In many engineering applications, enhancement of forced convection is important. Surface modifications like rib-roughening are commonly used in applications such as compact heat exchangers and cooling systems in gasturbine systems. Flow fields, friction factors and local and average heat transfer coefficients in rib-roughened ducts of the type appearyng are considered, here. Both experimental and numerical investigations are discussed. Details of the flow pattern and the influence of rib configuration, rib angle, rib pitch and rib height are discussed and physical interpretation of the results are provided. Some general conclusions are provided but it is also found that accurate numerical modelling of the flow and heat transfer from ribbed surfaces is difficult. Suggestions for further research are given.
Comparative study of the performance of an ejector refrigeration cycle operating with various refrigerants Sun,D.-W. Ener# Convers. Manage., 1999, 40, (S), 873-884.
Enhancement of heat transfer by turbulent decavina -~ --#~ swirl flaw
99103940
Dehumidifying chilled radiator system for hot and humid climates
99103935
Hirayama, Y. and Batty, W. J. Energy and Buildings, 1999, 30, (2), 203210. The paper investigates the application of room radiators for the purposes of cooling and dehumidification in buildings for hot and humid climates. The radiator is purposely brought below the dew point temperature of the room air thereby creating condensation on the radiator surface. The condensate is then collected at the base of the radiator and removed. A mathematical model describing the heat transfer regime within a room when this system is used has been verified using climate chamber tests. Results show the importance of the radiant transfer component for thermal comfort and suggests that more emphasis should be placed on this aspect during design. Furthermore, the possibilities for the chilled radiator system as an alternative to convdntional air conditioning systems by pa&ally or fully matching the sensible and latent component of the radiator output to the load requirements of a building is discussed. Since the temperature difference between the air and the radiator surface is small in this cooling application, larger surface areas are required than usual for the heating application. However, it means that the hot water temperature can be reduced for the heating mode. This allows the use of heat pumps to provide both hot and cold water at higher coefficients of performance than normally achievable. 99103936 Economic viability of cooling ceiling systems Sodec, F. Energy and Buildings, 1999, 30, (2), 195-201. Applying the numerical simulation program TRNSYS, the energy costs of a VAV system and a cooling ceiling system have been compared. The initial costs and the space requirements for the plants have also been collated. The cooling ceiling system was combined by the mechanical ventilation for the supply of outside air rate. Several parameters were varied to determine their influence on costs. A cooling ceiling system incurs lower energy costs and space requirements than VAV systems. Concerning the initial costs there is a break even point at a specific cooling load of 45-55 W m-*. At higher cooling loads, the first costs of a cooling ceiling system are more favourable.
Effect of humidity and small air movement on thermal comfort under a radiant cooling ceiling by subjective experiments
99103937
Kitagawa, K. et al. Energy and Buildings, 1999, 30, (2), 185-193. In comparison to the more frequently used convective air conditioning systems, radiant air-conditioning is expected to be more comfortable and have superior energy-savings. The objective of this study is to investigate the thermal comfort of local parts of the body and the whole body, in particular, including the effects of humidity and small air movements, by subjective experiments under a radiant cooling system. The experiments have been performed by using radiant cooling panels in a climate chamber. Subjects were seated on a chair under the radiant cooling panels, and voted their thermal sensation and comfortable sensation. The following results were obtained. Even in the radiant cooling system, the influence of humidity and small air movement on thermal sensation votes of the whole body could be correctly estimated by using a standard new effective
~G.
-
Yilmaz, M. et al. Energy Comers. Manage., 1999, 40, (13). 1365-1376. An experimental investigation was carried out on the heat transfer and friction characteristics of a decaying swirl flow. The swirling motion of the air was uroduced bv a radial euide vane swirl eenerator. The vanes of the swirl geherator we;e designeYd to be adjustable to obtain different swirl intensities. Different guide vane angles were used for the swirling flow experiments. The results were correlated in the form of Nusselt number as a function of Reynolds number, Prandtl number and the vane angle as Nu = 0.133Re”.h5Pr”.4(1 + tan )” 4”h. An augmentation of up to 98% in Nusselt number was obtained in the decaying swirl flow depending upon the Reynolds number and the vane angle. It was found that the performance of swirling flow is higher than corresponding axial flow with high vane angles and relatively low Reynolds numbers. 99103941 Estimation and measurement of electric energy consumption due to air conditioning cooling load Al-Rabghi, 0. M. et al. Energy Comers. Manage., 1999, 40, (14). 15271542. Due to air conditioning in buildings, electric energy consumption is tremendous. esoeciallv in nlaces havine hot humid weather. such as Jeddah. Saudi Arabia. ‘Building simulation pr&rammes, such as DOE2, are ve; valuable tools for studying building energy consumption under different conditions. These programmes can be used to investigate the effect of different building designs on their energy consumption. This paper presents the experimental and theoretical variations of electric power consumed by an air conditioning system. For the experimental part, a building has been chosen, and different sensors were installed to measure and record electric kW consumption at different indoor and outdoor conditions. In the theoretical part, the Visual DOE simulation programme, which is based on the well known DOE2E programme, has been used. Actual building data was fed to the programme to generate the instantaneous electric consumption due to air conditioning cooling load. Comparison between measured and predicted electric consumptions is presented.
Experimental analysis of a condenser heat recovery in an air condittoning plant
99103942
Schibuola, L. Energy, 1999, 24, (4), 273-283. The performance of a total heat recovery system was analysed by monitoring building-plant system long-term behaviour. Some of the installed chillers offer the possibility of a total recovery of the heat rejected by condenser. The results are very satisfactory both in energy and economic-financial terms. The experimental test takes advantage of the supervisor just existing in the building. Therefore it is an example of how these control systems can be used not only for safety and management needs, but also for a detailed performance analysis able to permit an easy simulation of the effects of different design and control options.
An experimental study of multiple parameter switching control for radiant floor heating systems
99103943
Cho, S.-H. and Zaheer-uddin, M. Energy, 1999, 24, (5), 433-444. Consisting of two identical 3 x 4.4 x 3.8 m3 rooms, an experimental facility was built; each room has a gas-fired boiler supplying hot water to the radiant-floor heating system. An electrically heated storage tank installed in
Fuel and Energy Abstracts
November 1999 413