The one-stream hybrid thermal network is analyzed and discussed based on the entransy theory,and the results are compared with those from the entropy generation optimization.The theoretical analysis indicates that the...The one-stream hybrid thermal network is analyzed and discussed based on the entransy theory,and the results are compared with those from the entropy generation optimization.The theoretical analysis indicates that the minimum heat-flow-weighted temperature of the thermal networks corresponds to the minimum entransy dissipation rate and the minimum thermal resistance.For a simple hybrid thermal network consisting of three thermal components,the expression of entransy dissipation is conducted,and the heat transfer area and the mass flow rate are calculated and optimized.The optimal results are obtained in order to minimize the entransy dissipation and the thermal resistance.The optimal results are calculated for various combinations,such as series connection,parallel connection and other hybrid connections.The numerical results are in accordance with the theoretical analysis.Both the theoretical analysis and the numerical results show that the minimum entransy dissipation and the minimum thermal resistance correspond to the minimum heat-flow-weighted temperature of the thermal networks while the minimum entropy generation does not.展开更多
It is of great importance to improve the energy performance of the air-conditioning system for building energy conversation. Entransy provides a novel perspective to investigate the losses existing in the air-conditio...It is of great importance to improve the energy performance of the air-conditioning system for building energy conversation. Entransy provides a novel perspective to investigate the losses existing in the air-conditioning system. The progress of entransy analysis in the air-conditioning system is comprehensively investigated in the present study. Firstly missions and characteris- tics of the air-conditioning system are analyzed with emphasis on heat or mass transfer process. It is found that reducing the temperature difference, i.e. reducing the entransy dissipation helps to improve the performance. Entransy dissipations and thermal resistances of typical transfer processes in the air-conditioning system are presented. Characteristics of sensible heat transfer process and coupled heat and mass transfer processes are researched in terms of entransy dissipation analysis. Reasons leading to entransy dissipation are also clarified with the help of unmatched coefficient 4. Principles for reducing the entransy dissipation and constructing a high temperature cooling system are summarized on the basis of case studies in typical handling processes. It＇s recommended that reducing mixing process, improving match properties are main approaches to reduce the entransy dissipation. The present analysis is beneficial to casting light on the essence of the air-conditioning system and proposing novel approaches for performance optimization.展开更多
基金supported by the Natural Science Foundation of China(Grant No. 51136001)the Tsinghua University Initiative Scientific Research Program
文摘The one-stream hybrid thermal network is analyzed and discussed based on the entransy theory,and the results are compared with those from the entropy generation optimization.The theoretical analysis indicates that the minimum heat-flow-weighted temperature of the thermal networks corresponds to the minimum entransy dissipation rate and the minimum thermal resistance.For a simple hybrid thermal network consisting of three thermal components,the expression of entransy dissipation is conducted,and the heat transfer area and the mass flow rate are calculated and optimized.The optimal results are obtained in order to minimize the entransy dissipation and the thermal resistance.The optimal results are calculated for various combinations,such as series connection,parallel connection and other hybrid connections.The numerical results are in accordance with the theoretical analysis.Both the theoretical analysis and the numerical results show that the minimum entransy dissipation and the minimum thermal resistance correspond to the minimum heat-flow-weighted temperature of the thermal networks while the minimum entropy generation does not.
基金supported by National Natural Science Foundation of China(Grant Nos.51422808&51521005)the National Science&Technology Pillar Program during the 12th Five-year Plan Period(Grant No.2014BAJ02B01)the China Postdoctoral Science Foundation(Grant No.2015M570107)
文摘It is of great importance to improve the energy performance of the air-conditioning system for building energy conversation. Entransy provides a novel perspective to investigate the losses existing in the air-conditioning system. The progress of entransy analysis in the air-conditioning system is comprehensively investigated in the present study. Firstly missions and characteris- tics of the air-conditioning system are analyzed with emphasis on heat or mass transfer process. It is found that reducing the temperature difference, i.e. reducing the entransy dissipation helps to improve the performance. Entransy dissipations and thermal resistances of typical transfer processes in the air-conditioning system are presented. Characteristics of sensible heat transfer process and coupled heat and mass transfer processes are researched in terms of entransy dissipation analysis. Reasons leading to entransy dissipation are also clarified with the help of unmatched coefficient 4. Principles for reducing the entransy dissipation and constructing a high temperature cooling system are summarized on the basis of case studies in typical handling processes. It＇s recommended that reducing mixing process, improving match properties are main approaches to reduce the entransy dissipation. The present analysis is beneficial to casting light on the essence of the air-conditioning system and proposing novel approaches for performance optimization.
