Simulation of Boiling Heat Transfer Characteristics of Pure Refrigerants of R14 and R23 and Their Zeotropic Mixtures Inside Horizontal Tube
In this paper,based on VOF multiphase flow model and Lee phase change model,the numerical simulation method is used to study the flow boiling characteristics of R14 and R23 at evaporation temperature of 208.15 K.In addition,based on the quasi-static theory,an improved heat and mass transfer model is proposed,and the flow boiling of zeotropic mixture R14/R23 is then predicted.The results show that the simulation data obtained by the new mass transfer model based on the concentration difference of components in the liquid phase are in good agreement with the experimental results.At the same evaporation temperature,the saturated gas density of pure refrigerant significantly affects the flow boiling heat transfer characteristics.For R14,R23 and their zeotropic mixture R14/R23,all the heat transfer coefficients increase nearly linearly with the quality.Moreover,the heat transfer coefficient of R14 increased most significantly,followed by R23,and that of R14/R23 mixture is the smallest.Under the same conditions,the heat transfer coefficients of R14/R23(0.5:0.5)mixture is at least 30%and 20%smaller than R14 and R23,respectively,which is due to the mass transfer resistance between components.
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