- Email: [email protected]
Residential sector air conditioning loads and electricity use in Hong Kong
13 Space heating and cooling of lighting&IVAC (heating, ventilation and air conditioning) interactions on the annual heating/cooling requirements of prototypical US commercial buildings through computer simulations using the DOE2.IE building energy analysis program. Twelve building types of two vintages and five climates are chosen to represent the US commercial building stock. For each combination of building type, vintage, and climate, a prototypical building is simulated with varying lighting power densities and the resultant changes in heating and cooling loads are recorded. These loads are used together with market information on the saturation of the different HVAC equipment in commercial buildings to determine the changes in energy use and expenditures for heating and cooline. Results are oresented bv building tvoe for the US as a whole. Theref&e, the data piesented in ihis pape; can be used to assess the secondary effects of lighting-related federal policies with widespread impacts, such as minimum efficiency standards. Generally, in warm climates the interactions will induce monetary savings and in cold climates the interactions will induce monetary penalties. For the commercial building stock in the US, a reduction in lighting energy that is well distributed geographically will induce neither significant savings nor significant penalties from associated changes in HVAC primary energy and energy expenditures.
In this paper a methodology for the optimal integration of water/ lithium bromide absorption chillers in combined heat and power plants is proposed. This method is based on the economic optimization of an energy plant that interacts with a refrigeration cycle by using a successive linear programming technique (SLP). The aim of this paper is to study the viability of the integration of absorption chillers in CHP plants. The results of this alternative are compared with the results obtained using the conventional way of producing chilled water, that is, using mechanical vapour compression chillers in order to select the best refrigeration cycle alternative for a given refrigeration demand. This approach is implemented in the computer program XV, and tested using the data obtained in the water/LiBr absorption chiller of Bayer in Tarragona (Catalonia, Spain). The results clearly show that absorption chillers are not only a good option when lost cost process heat is available, but also when a cogeneration system is present. In this latter case, the absorption chiller acts as a bottoming cycle by using steam generated in the heat recovery boiler. In this way, the cogeneration size can be increased, producing higher benefits than those obtained with the use of compression chillers.
00100583 Latent heat storage unit Fieback, K. et al. Ger. Offen. DE 19.823.417. 4. (In Germany) The latent heat storage unit consists of a paraffin wax-based latent heat storage core material and a paraffin wax-based casing. The melting point of the casing is higher than that of the core. The core can be encased by wither immersion or spraying with molten casing material.
Pottler, K. er al. Solar Energy, 1999, 67, (l-3), 35-52. Solar air heaters are limited in their thermal performance due to the low density, the small volumetric heat capacity and the small heat conductivity of air. For high solar gains, an efficient thermal coupling between absorber and fluid is required, while the electrical power for the fan operation ought to be as small as possible. As heat transfer augmentation usually increases friction losses, an optimum fin geometry has to be found. For a solar ventilation air preheater, mounted on a south facing facade in Wiirzburg, Germany, optimized geometries have been derived. For a specific air mass flow rate of 70 ke/(m’ h) the air eao for smooth absorbers without fins should be about 7td 8 mm to get amaximized yearly net energy output of aboutd8~~IvfJ/ m* during the heating season from October through April. Finned absorbers-perform much better. Continuous alumin&m-fins, 0.1 mm thick and spaced about 6 mm apart in a 30-mm-wide air gap yield about 900 MJ/m’ yearly net output. Offset strip fins do not show an improved performance compared to optimally spaced continuous fins, due to the larger electrical power for this geometry. However, offset strip fins yield high net energy gains for large fin spacings.
00100584
Management of industrial heating equipment
Gar dhuiourd’hui. 2000. 124. (6). 20-26. This article continues the series on this theme which examines the classification and choice of industrial burners. This particular article looks at the heat balance of an industrial installation and the third will look at ways to optimize this heat balance.
Mathematical models for the study of solidification within a longitudinally finned heat pipe latent heat thermal storage system
00100585
Horbaniuc, B. et al. Energy Convers. Manage., 1999,40, (15-16), 17651774. The solidification of the phase change material within a finned heat pipe latent heat thermal storage system is studied by means of an analytical technique considering the radial heat propagation toward the heat pipe wall and the angular propagation toward the fin. Two approximations for the temperature profile along the fin height are used: a Darabohc aooroximation (method I)I and an exoonential approximation (method II). The position of the solid-liquid’interface is plotted for the two methods for different fin numbers and the results are compared and discussed. 1.
Multi-pressure absorption cycles In solar refrigeration: a technical and economical study W/O0586
Alizadeh, S. Solar Energy, 2000, 69, (l), 37-44. A technical and economical study of regenerative absorption chillers with multi-pressure cycle has been undertaken as solar operated refrigeration systems. Referred to as advanced absorption chillers they represent one of the new technology options that are under development. Advanced absorption cooling technology offers the possibility of chillers with thermal coefficients of performances (COP) of 1.5 or greater at driving temperatures of 14o”C, which reduces the collector area and the heat rejection requirements compared to current absorption cooling technology. Two different absorption systems have been considered. The first is an advanced, double-effect regenerative absorption cooling system, driven at 140°C whose efficiency is about 55% of the Carnot efficiencv. The second is an ideal, single-effect regenerative absorption system that achieves 70% of the Carnot efficiency driven at 140 or 200°C. To evaluate the solar performance of a thermally driven chiller requires a separate analysis of the solar availability for a given location compared to the required monthly average solar input. In this analysis differenssystems, including the vapour compression chillers, have been compared in terms of the thermal and electrical energy input. An effective electrical COP may be computed assuming that the ratio of electrical energy cost to thermal energy cost is four, which is typical of today’s fossil fuel costs. The effective electrical COPS of different technical options can then be compared. Those systems with higher electrical COPS will have lower energy costs. If solar is to be competitive, then the cost of delivered solar thermal energy should be less than the cost of delivered fossil thermal energy.
Optimization of ener y plants Including water/ llthium bromide absorption chrl I ers
00100587
Bruno, J. C. In?. J. Energy Res., 2000, 24, (8), 695-717.
Optimized finned absorber geometries for solar air heating collectors 00/00588
00100589 Performance analysis of new alternatives to HCFC-22 inside air/refrigerant-enhanced surface tubing Sami, S. M. and Desjardins, D. E. Inf. J. Energy Res., 2000, 24, (9), 759-768. In this paper, the test results of a performance analysis of new alternatives; R-410A, R-507, R-407C, R-408A and R-404A proposed as substitutes to HCFC-22 are presented. The test results were obtained using an air-source heat -pump with enhanced surface tubing. Performance tests were conducted according to the ARI/ASHRAE Standards. The performance data demonstrated that as an interim replacement, the R-404A blend has a superior performance particularly at low temperatures among the proposed blends. Furthermore, the alternatives to R-22 are characterized by high discharge pressure compared to that of R-22. In particular, R-410A has the highest discharge pressure among the blend studied. R-407C has similar discharge temperature to R-22 at temperatures lower than -8°C.
Performance evaluation of hot-gas by-pass capacity control schemes for refrigeration and airconditioning systems 00/00590
Yaqub, M. Energy, 2000, 25, (6), 543-561. The capacity control of a vapour-compression refrigeration system is investigated by injecting hot gas and liquid refrigerant into the suction side of the compressor. Three different possibilities for the by-pass schemes are investigated for HFC-134a by considering finite size of the components that are used in the refrigeration systems. The model considers the finite-temperature difference in the heat exchangers, thus allowing the variations in the condenser and evaporator temperatures with respect to capacity and external fluid inlet temperatures. It is demonstrated that the compressor discharge temperatures increase significantly when the hot-gas from the compressor discharge is extracted and injected (without any liquid injection) directly into the suction side of the compressor. A comparative study is also performed of these schemes in terms of the system coefficient of performance, operating temperatures and the refrigerant by-pass fraction as a function of the percentage capacity reduction.
00/00591 Residential sector air conditioning loads and electricity use in Hong Kong
Lam, J.C. Energy Comers. Manage., 2000, 41, (15), 1757-1768. This paper presents the household electricity use for air conditioning in the residential sector in Hong Kong during the 26 year period from 1971 to 1996. Air conditioning accounts for about one third of the total Fuel end Energy Abstracts
January 2001
61
14 Heat pumps electricity use in the residential sector. A survey of the existing residential buildings has been conducted to establish typical design features. Based on these typical design variables, computer simulation techniques are used to estimate the likely energy savings from two energy efficient measures -the use of tinted glass to reduce solar heat and the application of thermal insulation to the external walls to lower heat conduction. The building energy computer program DOE-2 was used to predict the electricity savings for the 11-year period from 1997 to 2007. It has been found that the electricity savings are small during the initial years, about 0.2% of the total electricity use in the residential sector in 1997. However, as older buildings are replaced by newer ones with more energy efficient design features, the energy savings in subsequent years will have a bigger impact on the overall electricity use situation in the residential sector.
OOlOO592 The state significance of energy savin in buildings and principles of support programs in I!*rthuania
KIevas, V. and Zinevicius, F. Energy Policy, 2000, 28, (1 I), 791-798. This paper analyses by Lithuanian example multiflat houses problem which exists in most Central and Eastern Europe countries. Demand for heating in these houses is two or more times higher than in those in Western countries. Delay with solving of this problem has serious economic consequences. The problem is complicated because of the realization that heat saving potential is closely connected with the necessity to technical, economic and organizational reconstruction of district heating systems. State support for heat saving in buildings should be co-ordinated with programmes of technical reconstruction and organizational reorganization of district heating systems. A scenario for preparing district heating reconstruction programmes is proposed in which thermal renovation of buildings should be an integrated part.
00100593 Thermodynamic and physical properties of mixtures of refrigerants and oils Mermond, Y. et al. Znr. J. Refrig., 1999, 22, (7), 569-579. In order to detect the thermodynamic and transport properties of lubricating oils and of refrigerant and oil mixtures, predictive models have to be used, because of the effect of lubricants circulating within the refrigerating plant on boiling and convective condensation mechanisms and the shortage of data supplied by the manufacturers. Data obtained from the literature is compared with the results from the study.
00100594 Thermodynamic simulation and analysis on adsorption air conditioning system driven by exhausted gas in automobiles Tan, Z-C. and Wang, R-Z. Shanghai Jiaotong Dame Xuebao, 1999, 33, (8), 922-927. (In Chinese) Presented in this paper are the characteristics of an adsorption air conditioning system driven by the exhausted gas produced by automobiles. An analysis of heat transfer in heated/cooled fluids and adsorber is developed by numerical methods. The temperature field and heat transfer in the adsorber are obtained. It is found that the ‘heat pipe effect’ is apparent in isosteric heating and isosteric cooling stages, which can greatly enhance the effectiveness of heat transfer. A discussion is also included on several factors, such as working conditions and physical characteristics of adsorbent, which influence the performance of the system. It is stressed that the key technologies in this system are the enhancing of the effective thermal conductivity of the adsorber and decreasing the contact resistance.
00/00595 Typical weather data of main Turkish cities for energy apphcations
Tuner, M and Ileri, A. Znr. J. Energy Res., 2000, 24, (8) 727-748. Energy consumption and performance investigations of environmentdependent systems such as building HVAC and refrigeration systems, solar collectors, cooling towers, usually require weather information. This introduces a problem because there may be significant variances between the recurrent days or years. In this work, typical hourly weather data for the selected 23 provinces that represent demographic and climatic conditions of Turkey are obtained by using actual recordings. The results are stored as computer files ready to be used by simulation programs. By using these typical meteorological years, heating and cooling degree-days, dry-bulb temperature bins and winter and summer design dry-bulb temperatures are calculated. Sample typical-year simulations show for example that energy savings of about 11 and 16% could be expected in Ankara by 3 and 5 k night-setback, respectively. 62
Fuel and Energy Abstracts
January 2001
14
HEAT PUMPS
00100596 An economic and technical case for a compressor/expander unit for heat pumps
Henderson, P.C. et al. Znr. J. Energy Res., 2000, 24, (9). 831-842. Despite their obvious environmental benefit, heat pumps in general have difficulties in penetrating the heating market because of the high initial capital cost. However, given the fact that in the U.K., space heating alone accounts for nearly 50 per cent of all the primary energy used, the universal adoption of heat pump subsidies similar to those offered by certain German utilities for example would be an effective contributor to the reduction of greenhouse gas emission. However, it would be improper for subsidies alone to be the only mechanism by which heat pumps could gain the scale of market acceptance necessary in order to make the required greenhouse gas emission cuts. Therefore, a new generation of heat pumps must have a superior performance than existing units operating with HCFC R22 or R407c. The use of R410a can aid heat pump market penetration by having heat pumps of a superior performance and a smaller size. However, to make full use of R410a, the difficulties of the relatively low critical point must be overcome and the use of a novel compressor/expander unit is illustrated.
00100597 Extended mechanical efficiency theorems for engines and heat pumps
Senft, J. R. Znr. J. Energy Res., 2000, 24, (8), 679-693. Previous work carried out by the author has established basic theorems relating the mechanical efficiency of an engine to its thermodynamic cycle, external pressure and the effectiveness of its mechanism. That work treated the elementary single-workspace reciprocating piston heat engine. This paper extends the analysis to cover more complex engine types and heat pumps, including double-acting and splitworkspace devices. Theorems are derived which allow best-possible estimates and broad comparisons of the overall performance of a large variety of thermomechanical machines. Examples from the field of Stirling engines illustrate the application of the main results.
Reduction of the wear and corrosion of pumps and piping by suitable selection of materials
00100596
Joppien, H. Eur. Comm., /Rep./ EUR, 1999, l-98. (In German) Different methods have been successful for decreasing the wear and corrosion, and thus reducing the repair and maintenance costs, of pumps and piping, especially for operation in coal mines. The use of Ni-Hard-4 steel is one of the main solutions to the corrosion problems. The use of ceramic and elastomer coatings, for increase corrosion resistance and increasing working life of wear-prone pumps has been suggested for novel pumps. The degree of erosion of equipment is influenced significantly by the substitution of older pumps as well as an optimum retrofitting of pumps. In addition, the use of lubricating slide ring seals can also result in increased pump life and lower maintenance costs.
00/00599 Thermal performance of a solar-aided latent heat store used for space heating by heat pump
Mehmet, E. Solar Energy, 2000, 69, (1) 15-25. In this study, the cylindrical phase change strorage tank linked to a solar powered heat pump system is investigated experimentally and theoretically. A simulation model defining the transient behaviour of the phase change unit was used. In the tank, the phase change material (PCM) is inside cylindrical tubes and the heat transfer fluid (HTF) flows parallel to it. The heat transfer problem of the model (treated as two-dimensional) was solved numerically by an enthalpy-based finite differences method and validated against experimental data. The experiments were performed from November to May in the heating seasons of 1992-1993 and 1993-1994 to measure both the mean temperature of water within the tank and the inlet and outlet water temperature of the tank. The experimentally obtained inlet water temperatures are also taken as inlet water temperature of the simulated model. Thus, theoretical temperature and stored heat energy distribution within the tank have been determined. Solar radiation and space heating loads for the heating seasons mentioned above are also presented. 00/00600 Water desalination using heat pumps Siqueiros, J. Holland, F. A. Energy, 2000, 25, (8), 717-729. The USA/Mexico border areas have very limited water resources with salinity a major problem. Experimental work on heat pump assisted water purification has been carried out in Mexico since 1981. Initially, electrically driven mechanical vapour compression heat pumps were used. These were subsequently replaced by absorption heat pumps with the objective of developing systems to operate on environmentally clean low grade heat energy. These thermally driven units can either be designed as small scale mobile units to be used in disaster areas or
In this paper a methodology for the optimal integration of water/ lithium bromide absorption chillers in combined heat and power plants is proposed. This method is based on the economic optimization of an energy plant that interacts with a refrigeration cycle by using a successive linear programming technique (SLP). The aim of this paper is to study the viability of the integration of absorption chillers in CHP plants. The results of this alternative are compared with the results obtained using the conventional way of producing chilled water, that is, using mechanical vapour compression chillers in order to select the best refrigeration cycle alternative for a given refrigeration demand. This approach is implemented in the computer program XV, and tested using the data obtained in the water/LiBr absorption chiller of Bayer in Tarragona (Catalonia, Spain). The results clearly show that absorption chillers are not only a good option when lost cost process heat is available, but also when a cogeneration system is present. In this latter case, the absorption chiller acts as a bottoming cycle by using steam generated in the heat recovery boiler. In this way, the cogeneration size can be increased, producing higher benefits than those obtained with the use of compression chillers.
00100583 Latent heat storage unit Fieback, K. et al. Ger. Offen. DE 19.823.417. 4. (In Germany) The latent heat storage unit consists of a paraffin wax-based latent heat storage core material and a paraffin wax-based casing. The melting point of the casing is higher than that of the core. The core can be encased by wither immersion or spraying with molten casing material.
Pottler, K. er al. Solar Energy, 1999, 67, (l-3), 35-52. Solar air heaters are limited in their thermal performance due to the low density, the small volumetric heat capacity and the small heat conductivity of air. For high solar gains, an efficient thermal coupling between absorber and fluid is required, while the electrical power for the fan operation ought to be as small as possible. As heat transfer augmentation usually increases friction losses, an optimum fin geometry has to be found. For a solar ventilation air preheater, mounted on a south facing facade in Wiirzburg, Germany, optimized geometries have been derived. For a specific air mass flow rate of 70 ke/(m’ h) the air eao for smooth absorbers without fins should be about 7td 8 mm to get amaximized yearly net energy output of aboutd8~~IvfJ/ m* during the heating season from October through April. Finned absorbers-perform much better. Continuous alumin&m-fins, 0.1 mm thick and spaced about 6 mm apart in a 30-mm-wide air gap yield about 900 MJ/m’ yearly net output. Offset strip fins do not show an improved performance compared to optimally spaced continuous fins, due to the larger electrical power for this geometry. However, offset strip fins yield high net energy gains for large fin spacings.
00100584
Management of industrial heating equipment
Gar dhuiourd’hui. 2000. 124. (6). 20-26. This article continues the series on this theme which examines the classification and choice of industrial burners. This particular article looks at the heat balance of an industrial installation and the third will look at ways to optimize this heat balance.
Mathematical models for the study of solidification within a longitudinally finned heat pipe latent heat thermal storage system
00100585
Horbaniuc, B. et al. Energy Convers. Manage., 1999,40, (15-16), 17651774. The solidification of the phase change material within a finned heat pipe latent heat thermal storage system is studied by means of an analytical technique considering the radial heat propagation toward the heat pipe wall and the angular propagation toward the fin. Two approximations for the temperature profile along the fin height are used: a Darabohc aooroximation (method I)I and an exoonential approximation (method II). The position of the solid-liquid’interface is plotted for the two methods for different fin numbers and the results are compared and discussed. 1.
Multi-pressure absorption cycles In solar refrigeration: a technical and economical study W/O0586
Alizadeh, S. Solar Energy, 2000, 69, (l), 37-44. A technical and economical study of regenerative absorption chillers with multi-pressure cycle has been undertaken as solar operated refrigeration systems. Referred to as advanced absorption chillers they represent one of the new technology options that are under development. Advanced absorption cooling technology offers the possibility of chillers with thermal coefficients of performances (COP) of 1.5 or greater at driving temperatures of 14o”C, which reduces the collector area and the heat rejection requirements compared to current absorption cooling technology. Two different absorption systems have been considered. The first is an advanced, double-effect regenerative absorption cooling system, driven at 140°C whose efficiency is about 55% of the Carnot efficiencv. The second is an ideal, single-effect regenerative absorption system that achieves 70% of the Carnot efficiency driven at 140 or 200°C. To evaluate the solar performance of a thermally driven chiller requires a separate analysis of the solar availability for a given location compared to the required monthly average solar input. In this analysis differenssystems, including the vapour compression chillers, have been compared in terms of the thermal and electrical energy input. An effective electrical COP may be computed assuming that the ratio of electrical energy cost to thermal energy cost is four, which is typical of today’s fossil fuel costs. The effective electrical COPS of different technical options can then be compared. Those systems with higher electrical COPS will have lower energy costs. If solar is to be competitive, then the cost of delivered solar thermal energy should be less than the cost of delivered fossil thermal energy.
Optimization of ener y plants Including water/ llthium bromide absorption chrl I ers
00100587
Bruno, J. C. In?. J. Energy Res., 2000, 24, (8), 695-717.
Optimized finned absorber geometries for solar air heating collectors 00/00588
00100589 Performance analysis of new alternatives to HCFC-22 inside air/refrigerant-enhanced surface tubing Sami, S. M. and Desjardins, D. E. Inf. J. Energy Res., 2000, 24, (9), 759-768. In this paper, the test results of a performance analysis of new alternatives; R-410A, R-507, R-407C, R-408A and R-404A proposed as substitutes to HCFC-22 are presented. The test results were obtained using an air-source heat -pump with enhanced surface tubing. Performance tests were conducted according to the ARI/ASHRAE Standards. The performance data demonstrated that as an interim replacement, the R-404A blend has a superior performance particularly at low temperatures among the proposed blends. Furthermore, the alternatives to R-22 are characterized by high discharge pressure compared to that of R-22. In particular, R-410A has the highest discharge pressure among the blend studied. R-407C has similar discharge temperature to R-22 at temperatures lower than -8°C.
Performance evaluation of hot-gas by-pass capacity control schemes for refrigeration and airconditioning systems 00/00590
Yaqub, M. Energy, 2000, 25, (6), 543-561. The capacity control of a vapour-compression refrigeration system is investigated by injecting hot gas and liquid refrigerant into the suction side of the compressor. Three different possibilities for the by-pass schemes are investigated for HFC-134a by considering finite size of the components that are used in the refrigeration systems. The model considers the finite-temperature difference in the heat exchangers, thus allowing the variations in the condenser and evaporator temperatures with respect to capacity and external fluid inlet temperatures. It is demonstrated that the compressor discharge temperatures increase significantly when the hot-gas from the compressor discharge is extracted and injected (without any liquid injection) directly into the suction side of the compressor. A comparative study is also performed of these schemes in terms of the system coefficient of performance, operating temperatures and the refrigerant by-pass fraction as a function of the percentage capacity reduction.
00/00591 Residential sector air conditioning loads and electricity use in Hong Kong
Lam, J.C. Energy Comers. Manage., 2000, 41, (15), 1757-1768. This paper presents the household electricity use for air conditioning in the residential sector in Hong Kong during the 26 year period from 1971 to 1996. Air conditioning accounts for about one third of the total Fuel end Energy Abstracts
January 2001
61
14 Heat pumps electricity use in the residential sector. A survey of the existing residential buildings has been conducted to establish typical design features. Based on these typical design variables, computer simulation techniques are used to estimate the likely energy savings from two energy efficient measures -the use of tinted glass to reduce solar heat and the application of thermal insulation to the external walls to lower heat conduction. The building energy computer program DOE-2 was used to predict the electricity savings for the 11-year period from 1997 to 2007. It has been found that the electricity savings are small during the initial years, about 0.2% of the total electricity use in the residential sector in 1997. However, as older buildings are replaced by newer ones with more energy efficient design features, the energy savings in subsequent years will have a bigger impact on the overall electricity use situation in the residential sector.
OOlOO592 The state significance of energy savin in buildings and principles of support programs in I!*rthuania
KIevas, V. and Zinevicius, F. Energy Policy, 2000, 28, (1 I), 791-798. This paper analyses by Lithuanian example multiflat houses problem which exists in most Central and Eastern Europe countries. Demand for heating in these houses is two or more times higher than in those in Western countries. Delay with solving of this problem has serious economic consequences. The problem is complicated because of the realization that heat saving potential is closely connected with the necessity to technical, economic and organizational reconstruction of district heating systems. State support for heat saving in buildings should be co-ordinated with programmes of technical reconstruction and organizational reorganization of district heating systems. A scenario for preparing district heating reconstruction programmes is proposed in which thermal renovation of buildings should be an integrated part.
00100593 Thermodynamic and physical properties of mixtures of refrigerants and oils Mermond, Y. et al. Znr. J. Refrig., 1999, 22, (7), 569-579. In order to detect the thermodynamic and transport properties of lubricating oils and of refrigerant and oil mixtures, predictive models have to be used, because of the effect of lubricants circulating within the refrigerating plant on boiling and convective condensation mechanisms and the shortage of data supplied by the manufacturers. Data obtained from the literature is compared with the results from the study.
00100594 Thermodynamic simulation and analysis on adsorption air conditioning system driven by exhausted gas in automobiles Tan, Z-C. and Wang, R-Z. Shanghai Jiaotong Dame Xuebao, 1999, 33, (8), 922-927. (In Chinese) Presented in this paper are the characteristics of an adsorption air conditioning system driven by the exhausted gas produced by automobiles. An analysis of heat transfer in heated/cooled fluids and adsorber is developed by numerical methods. The temperature field and heat transfer in the adsorber are obtained. It is found that the ‘heat pipe effect’ is apparent in isosteric heating and isosteric cooling stages, which can greatly enhance the effectiveness of heat transfer. A discussion is also included on several factors, such as working conditions and physical characteristics of adsorbent, which influence the performance of the system. It is stressed that the key technologies in this system are the enhancing of the effective thermal conductivity of the adsorber and decreasing the contact resistance.
00/00595 Typical weather data of main Turkish cities for energy apphcations
Tuner, M and Ileri, A. Znr. J. Energy Res., 2000, 24, (8) 727-748. Energy consumption and performance investigations of environmentdependent systems such as building HVAC and refrigeration systems, solar collectors, cooling towers, usually require weather information. This introduces a problem because there may be significant variances between the recurrent days or years. In this work, typical hourly weather data for the selected 23 provinces that represent demographic and climatic conditions of Turkey are obtained by using actual recordings. The results are stored as computer files ready to be used by simulation programs. By using these typical meteorological years, heating and cooling degree-days, dry-bulb temperature bins and winter and summer design dry-bulb temperatures are calculated. Sample typical-year simulations show for example that energy savings of about 11 and 16% could be expected in Ankara by 3 and 5 k night-setback, respectively. 62
Fuel and Energy Abstracts
January 2001
14
HEAT PUMPS
00100596 An economic and technical case for a compressor/expander unit for heat pumps
Henderson, P.C. et al. Znr. J. Energy Res., 2000, 24, (9). 831-842. Despite their obvious environmental benefit, heat pumps in general have difficulties in penetrating the heating market because of the high initial capital cost. However, given the fact that in the U.K., space heating alone accounts for nearly 50 per cent of all the primary energy used, the universal adoption of heat pump subsidies similar to those offered by certain German utilities for example would be an effective contributor to the reduction of greenhouse gas emission. However, it would be improper for subsidies alone to be the only mechanism by which heat pumps could gain the scale of market acceptance necessary in order to make the required greenhouse gas emission cuts. Therefore, a new generation of heat pumps must have a superior performance than existing units operating with HCFC R22 or R407c. The use of R410a can aid heat pump market penetration by having heat pumps of a superior performance and a smaller size. However, to make full use of R410a, the difficulties of the relatively low critical point must be overcome and the use of a novel compressor/expander unit is illustrated.
00100597 Extended mechanical efficiency theorems for engines and heat pumps
Senft, J. R. Znr. J. Energy Res., 2000, 24, (8), 679-693. Previous work carried out by the author has established basic theorems relating the mechanical efficiency of an engine to its thermodynamic cycle, external pressure and the effectiveness of its mechanism. That work treated the elementary single-workspace reciprocating piston heat engine. This paper extends the analysis to cover more complex engine types and heat pumps, including double-acting and splitworkspace devices. Theorems are derived which allow best-possible estimates and broad comparisons of the overall performance of a large variety of thermomechanical machines. Examples from the field of Stirling engines illustrate the application of the main results.
Reduction of the wear and corrosion of pumps and piping by suitable selection of materials
00100596
Joppien, H. Eur. Comm., /Rep./ EUR, 1999, l-98. (In German) Different methods have been successful for decreasing the wear and corrosion, and thus reducing the repair and maintenance costs, of pumps and piping, especially for operation in coal mines. The use of Ni-Hard-4 steel is one of the main solutions to the corrosion problems. The use of ceramic and elastomer coatings, for increase corrosion resistance and increasing working life of wear-prone pumps has been suggested for novel pumps. The degree of erosion of equipment is influenced significantly by the substitution of older pumps as well as an optimum retrofitting of pumps. In addition, the use of lubricating slide ring seals can also result in increased pump life and lower maintenance costs.
00/00599 Thermal performance of a solar-aided latent heat store used for space heating by heat pump
Mehmet, E. Solar Energy, 2000, 69, (1) 15-25. In this study, the cylindrical phase change strorage tank linked to a solar powered heat pump system is investigated experimentally and theoretically. A simulation model defining the transient behaviour of the phase change unit was used. In the tank, the phase change material (PCM) is inside cylindrical tubes and the heat transfer fluid (HTF) flows parallel to it. The heat transfer problem of the model (treated as two-dimensional) was solved numerically by an enthalpy-based finite differences method and validated against experimental data. The experiments were performed from November to May in the heating seasons of 1992-1993 and 1993-1994 to measure both the mean temperature of water within the tank and the inlet and outlet water temperature of the tank. The experimentally obtained inlet water temperatures are also taken as inlet water temperature of the simulated model. Thus, theoretical temperature and stored heat energy distribution within the tank have been determined. Solar radiation and space heating loads for the heating seasons mentioned above are also presented. 00/00600 Water desalination using heat pumps Siqueiros, J. Holland, F. A. Energy, 2000, 25, (8), 717-729. The USA/Mexico border areas have very limited water resources with salinity a major problem. Experimental work on heat pump assisted water purification has been carried out in Mexico since 1981. Initially, electrically driven mechanical vapour compression heat pumps were used. These were subsequently replaced by absorption heat pumps with the objective of developing systems to operate on environmentally clean low grade heat energy. These thermally driven units can either be designed as small scale mobile units to be used in disaster areas or