Retrofit assessment of automobile air conditioners using hydrocarbon refrigerants

In this study, hydrocarbons (R600a and HR12) were selected as alternative refrigerants to evaluate their performance and feasibility as direct replacements for the R134a used in automobile air conditioners (MACs). The MAC performance tests were performed under fixed indoor conditions (27 °C, 50% RH) and outdoor ambient temperatures (T_oa, 35 °C) to determine the optimum charging amount and availability of hydrocarbons. The results showed that the optimal charging amount of HR12 (247.5 g) was 45% of that for R134a, and its cooling capacity (Q_c), dehumidification capacity (DH), and energy efficiency ratio (EER) were significantly better than those of R134a and R600a. Therefore, HR12 was more suitable for replacing R134a than R600a. In terms of the influence of T_oa changes on MAC performance, the Q_c, DH, and EER of HR12 used in MACs at a T_oa of 30 °C were 5.96%, 6.62%, and 81.02% higher than those of R134a, respectively. The differences of the Q_c, DH, and EER between the HR12 and R134a used in the MAC at a T_oa of 40 °C were 1.02%, 7.59%, and −9.79%, respectively. The results showed that a T_oa of 40 °C could cause a substantial decrease in the EER of HR12, mainly due to the increase in power consumption of MACs. However, in the T_oa range (30–40 °C) of this study, the Q_c and DH of HR12 were still higher than those of R134a, indicating that HR12 was suitable as a direct replacement for R134a in MACs.