In view of different compressor adding ways in the ammonia-water absorption/compression combined refrigeration AWA /CCR cycle combining the Schulz state equation of the ammonia-water solution the theoretical analysis ...In view of different compressor adding ways in the ammonia-water absorption/compression combined refrigeration AWA /CCR cycle combining the Schulz state equation of the ammonia-water solution the theoretical analysis and calculations on two combination ways by adding the compressor in the high-pressure area and in the low-pressure area are conducted respectively.The effects of several factors including the evaporation temperature Te heat-source temperature Th as well as the cooling water temperature Tw on the equivalent heat consumption in compression qCW heat consumption in absorption qG and the system coefficient of performance COP are analyzed under the two combination configurations.The results show that the effect of the equivalent heat consumption in compression on the COP is less than that of the heat consumption in absorption.Besides the compressor set in the high-pressure area uses more energy than that in the low-pressure area. Moreover the compressor in the low-pressure area is superior to that in the high-pressure area with respect to the COP. Under the given intermediate pressure there is an optimum heat-source temperature corresponding to the maximum COP of the AWA/CCR cycle.展开更多
The utilization of sensible waste heat such as flue gas and industrial surplus heat is essential for energy saving. Supercritical CO2 power generation cycle is a promising way to be used in this field. In this paper, ...The utilization of sensible waste heat such as flue gas and industrial surplus heat is essential for energy saving. Supercritical CO2 power generation cycle is a promising way to be used in this field. In this paper, a new supercritical CO2 Rankine cycle coupled with an absorption refrigeration cycle is proposed, which consists of a reheating supercritical CO2 cycle, a mixed-effect Li Br-H2O absorption refrigeration cycle and solar subsystem including evacuated-tube collector and a hot water storage tank. The system has four variants according to the presence or absence of solar subsystem and net cooling energy output. The thermodynamic model of the proposed system was established and its performance was evaluated. The proposed system is able to realize cascade utilization of flue gas waste heat and efficient conversion of solar energy. It has much higher thermodynamic efficiency than the reference system(i.e., the conventional supercritical CO2 Brayton cycle). Taking combined power and cooling system driven by flue gas waste heat and solar energy as an example, its thermal efficiency and exergy efficiency are 20.37% and 54.18% respectively, compared with the 14.74% and 35.96% of the reference system. Energy Utilization Diagrams(EUD) are implemented to investigate the irreversible losses and variation of the exergy destruction in the energy conversion process. Parametric analysis in two key parameters is conducted to provide guidance for the system optimal design.展开更多
A novel power and cooling cogeneration system which combines a supercritical CO_(2) recompression cycle(SCRC), an ammonia-water absorption refrigeration cycle(AARC) and a Kalina cycle(KC) is proposed and investigated ...A novel power and cooling cogeneration system which combines a supercritical CO_(2) recompression cycle(SCRC), an ammonia-water absorption refrigeration cycle(AARC) and a Kalina cycle(KC) is proposed and investigated for the recovery of medium-temperature waste heat. The system is based on energy cascade utilization, and the waste heat can be fully converted through the simultaneous operation of the three sub-cycles. A steady-state mathematical model is built for further performance study of the proposed system. When the exhaust temperature is 505℃, it is shown that under designed conditions the thermal efficiency and exergy efficiency reach 30.74% and 61.55%, respectively. The exergy analysis results show that the main exergy destruction is concentrated in the heat recovery vapor generator(HRVG). Parametric study shows that the compressor inlet pressure, the SCRC pressure ratio, the main compressor and the turbine I inlet temperature, and the AARC generator pressure have significant effects on thermodynamic and economic performance of the combined system. The findings in this study could provide guidance for system design to achieve an efficient utilization of medium-temperature waste heat(e.g., exhaust heat from gas turbine, high-temperature fuel cells and internal combustion engine).展开更多
Auto-cascade absorption refrigeration(ACAR) systems are a class of new cycles that can achieve low refrigeration temperatures by utilizing low-quality thermal energy. In this study, the equivalent thermodynamic proces...Auto-cascade absorption refrigeration(ACAR) systems are a class of new cycles that can achieve low refrigeration temperatures by utilizing low-quality thermal energy. In this study, the equivalent thermodynamic processes of a reversible ACAR system are established, and illustrated in a T-s diagram. The formula of the coefficient of performance for the reversible ACAR system is derived from the first and second thermodynamic laws. And then, the equivalent cycle of an irreversible ACAR system is established. The irreversible ACAR system is optimized by minimizing entropy generation of the thermodynamic processes. As a result, the optimum distribution ratio of heat fluxes at cascade process, which is defined as a ratio of heat fluxes between a condensing reservoir and cascade reservoir, and the optimum cascade temperature are obtained. Finally, its coefficient of performance and thermodynamic perfect degree are determined with minimum entropy generation.展开更多
The objective of this paper is to present a simulation study on the two-stage absorption refrigeration systems of 2.5 kW capacity using LiBr-H2O,NH3-H2O and R124-DMAC as working pairs.Under the design condition that t...The objective of this paper is to present a simulation study on the two-stage absorption refrigeration systems of 2.5 kW capacity using LiBr-H2O,NH3-H2O and R124-DMAC as working pairs.Under the design condition that the generating,absorbing,evaporating and condensing temperatures are 75℃,45℃,5℃and 40℃,respectively,the high and low pressure side solution circulation ratios and the coefficient of performance(COP)for the systems are calculated.Then the influences of medium,generating,absorbing,evaporating and condensing temperatures on system performances are analyzed.The results show that under the design condition,the COP of the LiBr-H2Osystem can reach 0.49,superior to those of the NH3-H2O and R124-DMAC systems,which are 0.32 and 0.31,respectively.Furthermore,the medium temperature for higher COP lies in an interval of 64-67℃for the LiBr-H2O.NH3-H2O and R124-DMAC systems.High generating temperature and low absorbing temperature can decrease the high and low pressure side solution circulation ratios,and can also increase the COP.High evaporating temperature can decrease the low pressure side solution circulation ratio and increase the COP.Low condensing temperature can decrease the high pressure side solution circulation ratio and increase the COP.展开更多
基金The National Natural Science Foundation of China(No.51176029)
文摘In view of different compressor adding ways in the ammonia-water absorption/compression combined refrigeration AWA /CCR cycle combining the Schulz state equation of the ammonia-water solution the theoretical analysis and calculations on two combination ways by adding the compressor in the high-pressure area and in the low-pressure area are conducted respectively.The effects of several factors including the evaporation temperature Te heat-source temperature Th as well as the cooling water temperature Tw on the equivalent heat consumption in compression qCW heat consumption in absorption qG and the system coefficient of performance COP are analyzed under the two combination configurations.The results show that the effect of the equivalent heat consumption in compression on the COP is less than that of the heat consumption in absorption.Besides the compressor set in the high-pressure area uses more energy than that in the low-pressure area. Moreover the compressor in the low-pressure area is superior to that in the high-pressure area with respect to the COP. Under the given intermediate pressure there is an optimum heat-source temperature corresponding to the maximum COP of the AWA/CCR cycle.
基金support of the China Postdoctoral Science Foundation(No.2018M641288)the Science and Technology Project of China Electric Power Planning&Engineering Institute(No.K201730-X)。
文摘The utilization of sensible waste heat such as flue gas and industrial surplus heat is essential for energy saving. Supercritical CO2 power generation cycle is a promising way to be used in this field. In this paper, a new supercritical CO2 Rankine cycle coupled with an absorption refrigeration cycle is proposed, which consists of a reheating supercritical CO2 cycle, a mixed-effect Li Br-H2O absorption refrigeration cycle and solar subsystem including evacuated-tube collector and a hot water storage tank. The system has four variants according to the presence or absence of solar subsystem and net cooling energy output. The thermodynamic model of the proposed system was established and its performance was evaluated. The proposed system is able to realize cascade utilization of flue gas waste heat and efficient conversion of solar energy. It has much higher thermodynamic efficiency than the reference system(i.e., the conventional supercritical CO2 Brayton cycle). Taking combined power and cooling system driven by flue gas waste heat and solar energy as an example, its thermal efficiency and exergy efficiency are 20.37% and 54.18% respectively, compared with the 14.74% and 35.96% of the reference system. Energy Utilization Diagrams(EUD) are implemented to investigate the irreversible losses and variation of the exergy destruction in the energy conversion process. Parametric analysis in two key parameters is conducted to provide guidance for the system optimal design.
基金supported by the Shandong Provincial Natural Science Foundation of China(No.ZR2019MEE045)the National Natural Science Foundation of China(No.51776203)the Key Project of National Natural Science Foundation of China(No.61733010)。
文摘A novel power and cooling cogeneration system which combines a supercritical CO_(2) recompression cycle(SCRC), an ammonia-water absorption refrigeration cycle(AARC) and a Kalina cycle(KC) is proposed and investigated for the recovery of medium-temperature waste heat. The system is based on energy cascade utilization, and the waste heat can be fully converted through the simultaneous operation of the three sub-cycles. A steady-state mathematical model is built for further performance study of the proposed system. When the exhaust temperature is 505℃, it is shown that under designed conditions the thermal efficiency and exergy efficiency reach 30.74% and 61.55%, respectively. The exergy analysis results show that the main exergy destruction is concentrated in the heat recovery vapor generator(HRVG). Parametric study shows that the compressor inlet pressure, the SCRC pressure ratio, the main compressor and the turbine I inlet temperature, and the AARC generator pressure have significant effects on thermodynamic and economic performance of the combined system. The findings in this study could provide guidance for system design to achieve an efficient utilization of medium-temperature waste heat(e.g., exhaust heat from gas turbine, high-temperature fuel cells and internal combustion engine).
基金financially supported by National Natural Science Foundation of China under Grant No.51206140 and No.50890184。
文摘Auto-cascade absorption refrigeration(ACAR) systems are a class of new cycles that can achieve low refrigeration temperatures by utilizing low-quality thermal energy. In this study, the equivalent thermodynamic processes of a reversible ACAR system are established, and illustrated in a T-s diagram. The formula of the coefficient of performance for the reversible ACAR system is derived from the first and second thermodynamic laws. And then, the equivalent cycle of an irreversible ACAR system is established. The irreversible ACAR system is optimized by minimizing entropy generation of the thermodynamic processes. As a result, the optimum distribution ratio of heat fluxes at cascade process, which is defined as a ratio of heat fluxes between a condensing reservoir and cascade reservoir, and the optimum cascade temperature are obtained. Finally, its coefficient of performance and thermodynamic perfect degree are determined with minimum entropy generation.
基金the National Natural Science Foundation of China(No.51776115)the Shandong Province Graduate Student Supervisor Guidance Ability Promotion Program(No.SDYY17037)the Shandong Univeisity uf 3uieuue ad Teuluulugy Giauluale 3uusdent Supervisor Guidance Ability Promotion Program(No.KDYC17009)。
文摘The objective of this paper is to present a simulation study on the two-stage absorption refrigeration systems of 2.5 kW capacity using LiBr-H2O,NH3-H2O and R124-DMAC as working pairs.Under the design condition that the generating,absorbing,evaporating and condensing temperatures are 75℃,45℃,5℃and 40℃,respectively,the high and low pressure side solution circulation ratios and the coefficient of performance(COP)for the systems are calculated.Then the influences of medium,generating,absorbing,evaporating and condensing temperatures on system performances are analyzed.The results show that under the design condition,the COP of the LiBr-H2Osystem can reach 0.49,superior to those of the NH3-H2O and R124-DMAC systems,which are 0.32 and 0.31,respectively.Furthermore,the medium temperature for higher COP lies in an interval of 64-67℃for the LiBr-H2O.NH3-H2O and R124-DMAC systems.High generating temperature and low absorbing temperature can decrease the high and low pressure side solution circulation ratios,and can also increase the COP.High evaporating temperature can decrease the low pressure side solution circulation ratio and increase the COP.Low condensing temperature can decrease the high pressure side solution circulation ratio and increase the COP.
