R1234yf/R134a Based Refrigerant Mixture for Automobile Air Conditioning Systems: A Thermodynamic Approach

Abstract

The environmental protocols lead to analysing various refrigerants minimum global warming potential (GWP) to substitute high GWP R134a in an automobile air conditioning (AAC) system. The present study deals with the thermodynamic analysis of the AAC unit using R1234yf/R134a refrigerant mixtures under three-vehicle speed conditions such as idling (L-900 rpm), city limit (M-1800 rpm), and high speed (H-2700 rpm). The mass fractions of R1234yf/R134a such as 0:1, 1:0, 0.9:0.1, 0.8:0.2, 0.7:0.3, 0.6:0.4 and 0.5:0.5 were considered in this analysis. The cooling capacity and coefficient of performance (COP) of R1234yf were observed to be poorer than that of the existing R134a by up to 10.4% and 8.3%. The addition of R134a in R1234yf reduced the performance gap between the existing R134a system under all the speed conditions. There was an increase cooling capacity and COP of the AAC by up to 6.4% and 4.9% was found with the addition of 0.5 mass fraction of R134a in R1234yf. However, the GWP of the refrigerant mixture was increased with rise in R134a mass fraction of which causes more direct CO2 emission from the AAC system. This study prevailed that the use of R1234yf/R134a mixture (0.5:0.5 by a mass fraction) performed very much similar to that of R134a in the AAC unit. Further, the R1234yf/R134a mixture (0.9:0.1 by a mass fraction) is suggested to use in the AAC system to satisfy the environmental protocols (GWP < 150).