润滑油对R1234yf蒸发沸腾影响的分子动力学研究  

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

作　　者：蔡守银 李期斌[1] 刘朝[1] 徐肖肖[1] 张路[1] CAI Shou-Yin;LI Qi-Bin;LIU Chao;XU Xiao-Xiao;ZHANG Lu(Key Laboratory of Low-grade Energy Utilization Technologies&Systems,Ministry of Education,College of Energy and Power Engineering,Chongqing University,Chongqing 400044,China)

机构地区：[1]重庆大学能源与动力工程学院,低品位能源利用技术及系统教育部重点实验室,重庆400044

出　　处：《工程热物理学报》2021年第11期2796-2803,共8页Journal of Engineering Thermophysics

基　　金：国家自然科学基金资助项目(No.51876015)。

摘　　要：制冷工质溶油性较差时,热力循环中会发生相分离,导致换热减少,并且在换热表面上形成油膜抑制传热。研究润滑油对制冷工质在表面相变换热的影响及其内在作用机理具有重要意义。本文采用分子动力学模拟方法研究了润滑油PEC4对制冷工质R1234yf蒸发沸腾的影响。结果表明,在蒸发沸腾过程中,汽核由R1234yf分子形成,直至聚并长大、形成汽膜。随着PEC4质量分数的增加,Cu表面上PEC4的吸附量逐渐增加,R1234yf分子的吸附量逐渐减小。Cu表面吸附的PEC4会在表面形成一层油膜,影响基底传热,抑制蒸发沸腾。液体层中R1234yf分子非均匀分布,粒子数密度分布出现了波动现象。PEC4质量分数为15.4%的混合物比其他体系需要获得更多的热能,这将提高工质的沸点进而影响传热效率。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.

关 键 词：润滑油 R1234yf 蒸发沸腾 分子动力学模拟 

分 类 号：TK211[动力工程及工程热物理—动力机械及工程]