R14和R23及其非共沸混合物在水平管内沸腾换热特性的模拟研究

Simulation of Boiling Heat Transfer Characteristics of Pure Refrigerants of R14 and R23 and Their Zeotropic Mixtures Inside Horizontal Tube

本文采用数值模拟方法,应用VOF多相流模型及Lee相变模型,研究了R14和R23工质在蒸发温度为208.15K时的管内流动沸腾特性。同时,基于准静态理论提出了一种改进的传热传质模型,并利用该模型预测了非共沸工质R14/R23的流动沸腾特性。结果表明,基于液相组分浓度差的组分相间传质模型获得的模拟数据与实验结果具有较好的一致性。在相同蒸发温度下,纯工质的饱和气相密度对其在管内的流动沸腾换热具有显著影响。对于R14、R23及其非共沸混合物R14/R23,其流动沸腾传热系数随干度的增加均呈近线性增大趋势,且低沸点纯R14工质换热系数的增大趋势最显著,R23次之,R14/R23混合物最小。在相同工况下,混合工质R14/R23(0.5:0.5)的传热系数均小于其纯组分的对流传热系数,分别比R14、R23小30%和20%以上,其根本原因在于混合工质存在组分间传质阻力。

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.