R1234yf and R744 as alternatives to R134a at mobile air conditioners

: R1234yf is a synthetic HFO refrigerant co-developed as a replacement refrigerant for R134a in automotive air conditioning applications. Thus, in this study, alternatives to the R134a refrigerant that were removed from the newly produced devices were examined. The performance of the cooling processes of R1234yf and R744 refrigerant gases was compared with that of R134a. A simulation model was first developed. This simulation model was validated with experimental results. Analysis was conducted for both cooling and heating modes. In the case of cooling, evaporation temperature was 5 °C–7.5 °C, condenser, or gas cooler outlet temperature was 35 °C– 50 °C and the cooling load was 10 kW. In heating mode, evaporation temperature was −4 °C–12 °C, condenser, or gas cooler outlet temperature was 45 °C–50 °C and the heating load was 13.5 kW. The results were analyzed in terms of the coefficient of performance (COP), compressor power consumption, and compressor discharge temperature. In terms of COP and compressor power consumption, R134a gave the best results in all cases. R1234yf gave the closest results to R134a. In terms of compressor discharge temperature, which affects the lifetime and lubrication quality of the compressor, R1234yf gave the lowest temperatures in all cases.