Retrofitting hydrocarbon refrigerants in automobile air conditioning systems

This study investigated the feasibility of retrofitting propane (R290) and isobutane (R600a) into R134a-automotive air conditioners (AACs) equipped with an electronic expansion valve. First, the optimal charging weight (CW) of R290 and R600a was determined. Next, the R134a-AAC was retrofitted with R290 and R600a at the optimal CWs, and air conditioning performance was evaluated under varying compressor speeds and outdoor ambient temperatures (T_OA). The results indicate that the optimal CWs for R290 and R600a in R134a-AACs are 30 % (180 g) and 45 % (270 g) of the R134a refrigerant charge, respectively. R290 achieved optimal air conditioning performance at a T_OA of 30 °C, but its performance decreased significantly as the T_OA increased. R600a achieved the highest energy efficiency ratio (EER), but its cooling capacity was lower than that of R134a. These performance limitations can be further verified through subsequent experiments by modifying the evaporator piping configuration, increasing the volumetric displacement of compressor, and improving the condenser’s heat dissipation performance to enhance the feasibility of HC as a replacement for R134a-AAC.