Abstract
As global regulations on carbon dioxide emissions continue to tighten, the automotive industry is increasingly focused on reducing its carbon footprint. Consequently, electric vehicle (EV) refrigerants are being developed to minimize their environmental impact. In this context, natural refrigerants such as R‐744 and R‐290 have attracted significant interest. However, only a limited number of studies have experimentally compared R‐744 and R‐290 in EV heat pump systems (HPSs). In this study, EV HPSs using R‐744, R‐290, and R‐1234yf were experimentally evaluated under equivalent system‐level boundary conditions. The experimental systems were constructed as vehicle‐scale heat pump benches consisting of scroll compressors, outdoor and indoor heat exchangers, expansion devices, and an accumulator/accumulator heat exchanger, with each system configured according to the operating characteristics of the corresponding refrigerant. In cooling mode, the coefficient of performances (COPs) was highest for R‐744 at 1.65, followed by R‐290 at 1.58 and R‐1234yf at 1.43. In heating mode, the COPs were highest for R‐744 at 2.89, followed by R‐290 at 2.47 and R‐1234yf at 1.99. Overall, R‐744 demonstrated superior performance in both cooling and heating due to reduced exergy destruction under high‐pressure operation, while R‐290 showed strong potential within its optimal revolutions per minute (RPM) range and benefited from a wide two‐phase region. Meanwhile, R‐1234yf serves as a low‐global warming potential (GWP) reference refrigerant widely used in automotive HPSs in the present tests. The flammability of R‐290 and the high operating pressure required for R‐744 indicate that further optimization of refrigerant‐specific components such as the compressor, expansion valve, and pressure‐resistant heat exchangers will be essential for advancing natural refrigerant EV HPSs.
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