Energy and Exergy Efficiency Analysis of an Ejector-Expansion Refrigeration Cycle Using the Working Fluid R134a and Its Potential Substitutes

Abstract

This paper proposes an ejector-expansion refrigeration cycle (EERC) with two evaporating temperatures to recover partial expansion work and greatly reduces the throttling loss of the other expansion valve connected to the evaporator compared with the conventional bievaporator refrigeration cycle (CBEC). Furthermore, R134a will be phased out due to its high global warming potential, while the mixture refrigerants of R1234yf, R1234ze, and R152a were considered as potential alternatives. The energy and exergy analysis methods are used to evaluate and compare the performance of two cycles and seven kinds of different refrigerants. Results show that the coefficient of performance (COP) and exergy efficiency of EERC are 17.1% and 16.4% higher than those of CBEC, and the total exergy loss can be reduced by 26.1% under given operating conditions. The drop-in analysis is carried out for equal operating conditions, and the EERC performances of mixtures are analyzed. The mixture refrigerants of R1234yf R152a/R1234yf/R1234ze (mass fraction of 0.4/0.3/0.3) and R134a/R1234yf (mass fraction of 0.9/0.1) appear to be a good candidate for drop-in replacement of R134a due to similar COP, volumetric cooling capacity, and exergy efficiency.