Evaluating retrofitting and operational efficiency of automobile air conditioners using environmentally-friendly refrigerants

This study evaluated two low global warming potential (GWP) refrigerants as direct replacements for R134a in automotive air conditioners (AACs) to meet international environmental protection standards. R152a and R1234yf were substituted with 75 % (300 g) and 110 % (440 g) of the R134a filling capacity (400 g) for AACs, respectively. Additionally, operating efficiency tests of AACs with various refrigerants were conducted under different outdoor ambient temperatures (T_{oa, DB}: 30, 35, and 40°C) and compressor speeds (1000 and 1800 rpm) while maintaining fixed indoor conditions. The results indicated that the performance metrics, including compression ratio, cooling capacity, electrical power consumption (P_c), and energy efficiency ratio (EER), were superior for AACs using R152a compared to those using R134a across all experimental conditions. When performing performance tests at T_{oa, DB} of 35 °C, and a compressor speed of 1800 rpm, the P_c for R152a and R1234yf were 5.96 % and 5.04 % lower than those of the original AAC. The EER values were 11.26 % and 1.45 % higher than those of the original AAC. Furthermore, the total equivalent warming impact (TEWI) of R152a is better than that of R1234yf when the daily driving duration exceeds 4.9 h. This suggests that R152a offers both energy-saving and environmental protection effects when used in AACs for extended driving periods.