The Optimal Performance of Low-Temperature Hot Source Driven Two-Stage Libr/H_2O Absorption Refrigerator

摘要

An irreversible cycle model of a two-stage LiBr/H_2O absorption refrigerator is established and used to analyze the performance of the refrigerator affected by the irreversibility of finite-rate heat transfer and the internal irreversibilities of the working substance. The total thermal conductance of the six heat exchangers is taken as an objective function for optimization by Lagrange's method of multipliers. The minimum total thermal conductance is described in terms of the rate of the entropy changes of the six heat reservoirs, and then an analogue of the second law of thermodynamics is derived, which is viewed as an extension of the second law. The optimal distribution relation of the thermal conductance of the heat exchangers is derived. The optimal relation between rates of cooling loads, the coefficient of performance and total thermal conductance is achieved. The influence of the internal irreversibilities on the performance of the system is discussed. The results can provide some new theoretical approach of the optimization design and performance improvement of real two-stage absorption refrigerator.