Exergetic optimisation of a four-temperature-level absorption heat pump based on finite-time thermodynamics

Abstract

A finite-time thermodynamics study and an exergetic optimisation for a four-temperature-level absorption heat pump have been performed. The maximum of the exergetic-performance coefficient (EPC) and the corresponding optimal ecological coefficient of performance (ECOP), ecological objective function (E), exergetic efficiency (ex), coefficient of performance (COP), specific entropy generation rate and heating load have been obtained. The effects of internal irreversibilities, external irreversibilities, heat leakages, ratio of the rejected heat of the absorber to the condenser and the heat-transfer coefficients of different components on the system performance have been analysed and discussed. It was noticed a greater harmful impact of heat losses in the generator-absorber assembly. Comparisons of EPC criterion with ECOP, COP, E and ex criteria have been provided. The results demonstrate that the four-temperature-level absorption heat pump working at maximum EPC conditions has a significant advantage in terms of entropy generation rate and coefficient of performance.

Keywords

• irreversibilities
• exergetic-performance coeffiecient
• absorption heat pump
• four-temperature-level
• optimisation