Theoretical Analysis of Energy, Exergy, and Environmental-Related Aspects of Hydrofluoroolefin Refrigerants as Drop-In Alternatives for R134a in a Household Refrigerator

Abstract

There are increasing trends to eliminate refrigerants with a high Global Warming Potential GWP and use alternative environmentally friendly refrigerants in refrigeration systems. In this regard, this study presents a triple analysis of the energy, exergy, and environmental-related aspects of low-GWP hydrofluoroolefin refrigerants—R1234yf, R1234ze(E), and R1336mzz(Z)—as substitutes for the high-GWP R134a, which is used in a 200-liter household refrigerator having a 157 W cooling power. Pressure ratio, volumetric refrigeration capacity, power consumption, and coefficient of performance were studied as energy performance parameters. Exergy destruction rate and total exergy efficiency were studied as exergy performance parameters. Total equivalent warming impact was studied as an environmental performance parameter. All parameters were calculated under a condenser and ambient temperature of 30 and 40 °C, respectively, and a variable evaporator temperature of -5 to -30 °C. The outcomes revealed that R1234yf and R1234ze(E) give thermal performance close to R134a and higher environmental performance, while R1336mzz(Z) did not show thermal performance close to R134, nor did it show a clear improvement in environmental performance. R1234yf can be used as a direct replacement for R134a, but R1234ze(E) is considered a better alternative provided that the R134a compressor is replaced with a compressor with a higher displacement. The pure R1336mzz(Z) cannot be used in a refrigerator.