Evaporation characteristics of R32/R134a binary refrigerant mixture films at low pressures: A molecular dynamics study

HY Fu and SC Wang and LP Zhou and XZ Du, INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER, 163, 108784 (2025).

DOI: 10.1016/j.icheatmasstransfer.2025.108784

This work studies the evaporation characteristics of R32/R134a binary refrigerant mixture nanofilms on copper surface at low pressures using molecular dynamics method. With the piston method of pressure control, the evaporation characteristics are analyzed based on mixture composition, ambient pressure, and thickness. Key factors such as number of liquid molecules, evaporation rate, energy change, and surface tension are considered. The evaporation rate increases with the R32 mass fraction due to the differences in the interaction energy between R32 and R134a molecules. However, for mixtures with 60 % R32, the evaporation rate is higher than that of mixtures with 80 % R32 during the first 2 ns, due to the influence of R134a molecules. The surface tension decreases while the corresponding heat flux gradually increases as the R32 mass fraction increases. Reducing the ambient pressure accelerates the evaporation rate compared to atmospheric pressure, but R32 is less sensitive to pressure than R134a. A size effect is observed in the film evaporation, with a critical thickness influencing the behavior. When the film thickness exceeds the critical value, the evaporation is more intense; however, below this threshold, the evaporation remains relatively stable. This provides valuable insights for the applications of environmentally friendly and cost-effective refrigerants.

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