Exergy-based efficient ecological-function optimization for endoreversible Carnot refrigerators

Abstract

Based on the definition of exergy-based efficient ecological-function (EEF) proposed in the existing literature, which is the product of energy conversion coefficient-of-performance (ɛ) and exergy-based ecological-function (E), this paper will introduce the exergy-based EEF into performance optimization for Carnot refrigerator cycle. Via endoreversible Carnot refrigerator model established in previous literature, expression of the exergy-based EEF of refrigerator is derived based on finite-time thermodynamic theory, relationships of dimensionless exergy-based EEF versus ɛ and cooling load (R) are studied, and performance differences of refrigerator cycles at the maximum exergy-based EEF, at the maximum E, and at the maximum efficient cooling-load conditions are compared. The results demonstrate that relationships of dimensionless exergy-based EEF versus R and ɛ are parabolic-like ones; in actual design, the refrigerator should be designed at the larger R and ɛ points. When exergy-based EEF is taken as optimization-objective, although R decreases slightly, ɛ is increased, and entropy-generation-rate (σ) is greatly decreased, so exergy-based EEF does not only reflect the compromise between the R and σ, but also reflect the compromise between the R and ɛ.