The Fundamental Optimum Relation Of A Multi-heat-source Irreversible Refrigeration Cycle And Its Performance Analysis

Theory of finite-time thermodynamics is an extension of classical thermodynamics. Because it has specific contents and distinct research methods, it has become an important theoretical tool that is often used in the research of irreversible thermodynamic process constrained in finite time. In this paper, theories of finite-time thermodynamics and optimal control are used to investigate the optimum performance of an irreversible absorption refrigerator working in multi-temperature-level heat sources. Firstly, the irreversible cycle model of an absorption refrigerator operating between four-temperature-level is used to derive the fundamental optimum relation between the cooling load per unit heat-transfer area and the coefficient of performance of the absorption refrigerator affected by the irreversibility of finite-rate heat transfer and the internal irreversibilities of the working substance. Secondly, The curves of the cooling load per unit heat-transfer area varying with the coefficient of performance are investigated based on the fundamental optimum relation. The characteristics of the maximal cooling load per unit heat-transfer area and the corresponding coefficient of performance are searched. A criterion of finite time thermodynamics is obtained, which is helpful for the selection of optimally operating conditions. Moreover, the influence of the heat source temperatures-. the irreversibility of heat transfer and the internal irreversibilities on the performance of the absorption refrigerator are analyzed. The new significant conclusions obtained here may provide some theoretical bases for the optimal design. Finally, the fundamental optimum relations of several special cases such as four-heat-source endorreversible absorption refrigerators and three-heat-source absorption refrigerators are derived. The results obtained here may include some important conclusions relative to absorption refrigerators in the literature. To sum up, the conclusions obtained in the present paper are of general significance. They can be suitable for multi-heat-source refrigerators with absorption refrigeration as well as other refrigeration methods.