Effects of Lubricant on Evaporation and Boiling Processes of R1234yf: a Molecular Dynamics Study

The mutual solubility of the lubricant and the refrigerant will impact the heat transfer performance and the reliability of the heat exchange system. If refrigerant and lubricant cannot dissolve adequately, phase separation will occur in the cycle, which leads to the formation of oil film on the heat transfer surface of the condenser and evaporator. Therefore, molecular dynamics simulations are employed to investigate the effects of lubricant PEC4 on the evaporation and boiling processes of R1234yf in this paper. The results indicate that the bubble nuclei are formed from R1234yf molecules. Then they coalesce and grow up to form steam film during the evaporation and boiling processes. Additionally, PEC4 molecules will gradually replace R1234yf molecules to absorb on Cu surface with the increase of PEC4 mass fraction. Next, an oil film will be formed on Cu surface and weaken the heat transfer capacity at fluid-solid interface. The R1234yf molecules in the liquid layer are nonuniformly distributed, and the distribution of particle number density fluctuates. The evaporation of 15.4wt% PEC4 mixtures system need to obtain more heat energy than other systems, which will increase the boiling point of the working medium and affect the heat transfer efficiency. © 2021, Science Press. All right reserved.