Molecular dynamics study of the evaporation of R1233zd(E) and its isomers on Cu surface

Abstract

As a new alternative working fluid of heat pump, HFO-1233 has excellent environmental performance and theoretical cycle characteristics. However, the differences in physicochemical properties between its isomers can affect the interfacial evaporation characteristics, which is of great significance for further screening of the working fluid. In this paper, the evaporation behavior of liquid films of R1233zd(E), R1233zd(Z) and R1233xf on Cu surface at 335 K was simulated by molecular dynamics method. The results show that among the three working fluids, R1233xf has the smallest Kapitza thermal resistance at the vapor-liquid interface, which is only 0.38 × 10⁻⁷ m²⋅K⋅W⁻¹. Moreover, the surface tension and liquid interaction energy of R1233xf are the smallest, and the self-diffusion coefficient is the largest, which will accelerate the escape of R1233xf at the vapor-liquid interface. The resulting evaporation rate and heat flux are R1233xf > R1233zd(E) > R1233zd(Z). At steady state, the evaporation rate of R1233xf reaches 1240 kg⋅m⁻²⋅s⁻¹, which is 1.38 times that of R1233zd(Z). Finally, the solid-liquid interaction strength of the three working fluids in the solid-like layer was studied by the solid-liquid interaction model, and it was found that R1233xf still had the smallest solid-liquid interaction force. The results explain the interfacial phase change mechanism of working fluids from the molecular-scale, providing insights for the selection of working fluids and the design of heat exchangers in high-temperature heat pumps.