Effect of dilutant concentration on the performance of environment-friendly mixed refrigerants used in domestic refrigerators.

Abstract

This paper presents the environment-friendly mixture compositions of hydrocarbons (HC)- and hydrofluorocarbon (HFC)-based ternary mixtures that can be better alternatives for R134a in domestic refrigeration units. Combustible refrigerant HCs (R290, R600, R600a) and HFCs (R152a and R161) are used along with the dilutants R13I1, R245fa, R134a, R227ea, and R125 and their flammability studies were carried out theoretically. Minimum inerting concentration (MIC) is used to classify the flammable and non-flammable zones of the ternary mixtures. MIC points estimated with modified thermal balance method (MTBM) are compared with 62 experimental data points available in the literature. It was calculated that MTBM predicted the MIC values with in ±9%, for most of the working fluids selected in this study. R13I1 is used along with all the refrigerant (HC and HFC) combinations (as the first dilutant) while the effect of other dilutants on the system performance is carried out theoretically. It is predicted from the flammability diagram (developed in this study) that the inert effect of R227ea is higher than of R245fa, R134a, and R125. It is also observed that the drop in coefficient of performance (COP) is significant with R290/R13I1/R245fa (with increase in R245fa) mixture when compared to other combinations. Finally, mixtures R600a/R13I1/R245fa, R600a/R13I1/R227ea, R600a/R13I1/R134a, R600a/R13I1/R125, R161/R13I1/R134a, R290/R13I1/R125, R161/R13I1/R227ea, and R161/R13I1/R125 are identified as the best environment-friendly mixture compositions as alternatives to R134a. It is also calculated that the mixture R600a/R13I1/R125 possesses COP greater than 10% to R134a at the same working conditions.