Exergetic efficiency optimization of a refrigeration system with multi-irreversibilities

Abstract

Exergetic efficiency optimization has been carried out for a refrigeration system with multi-irreversibilities, including finite-rate heat transfer, internal dissipation of the working fluid and heat leak between the heat reservoirs. The exergetic efficiency is defined as the ratio of the rate of exergy output to the rate of exergy input in the refrigeration system and is considered as an objective function to be maximized. By combining the exergy concept and finite-time thermodynamic theory, the maximum exergetic efficiency is determined analytically. The optimum values of the cycle cooling rate and the coefficient of performance of the system are obtained simultaneously. The influences of various parameters on the maximum exergetic efficiency are investigated by numerical calculation. The allocation problem of a fixed total thermal conductance between the hot-side and the cold-side heat exchangers is also studied. The results show that the method of exergetic efficiency optimization is practical and effective for the evaluation of an irreversible refrigeration system.