A theoretical model for flow boiling liquid film evaporation of zeotropic mixtures was proposed based on the film theory. Taking into account the mass transfer process in both the liquid and vapor phases, the mass transfer coefficient in the liquid concentration boundary layer was modified in this model. The calculated accuracy of this model was well validated by Takamatsu's experiments. The flow boiling liquid film evaporation process in a single rectangular channel filled with zeotropic mixtures R134a/R245fa was investigated, including the interfacial heat and mass transfer mechanisms and the components change as well as the migration characteristics. The results indicated that the compositions at the interface and in bulk flow in both the liquid and vapor phases all showed the downward trend with increase of the vapor quality. The difference in the composition of the bulk vapor and bulk liquid and the composition in the liquid concentration boundary layer were the representations of mass transfer resistance to the heat transfer degradation in nucleate boiling and convective evaporation. Compared to the liquid film evaporation process, the heat transfer coefficient had the strongest relation with the composition change in the liquid boundary layer.

中文翻译：

---

液膜蒸发过程中R134A / R245FA共沸混合物传热传质的分析研究

基于膜理论，提出了共沸混合物流沸腾液膜蒸发的理论模型。考虑到液相和气相中的传质过程，在该模型中修改了液体浓度边界层中的传质系数。高松的实验很好地验证了该模型的计算准确性。研究了填充有共沸混合物R134a / R245fa的单个矩形通道中的沸腾液膜蒸发过程，包括界面传热和传质机理以及组分变化和迁移特性。结果表明，在液相和气相中，界面处和整体流动中的组成均显示出随着蒸气质量的增加而下降的趋势。大体积蒸气和大体积液体的组成以及液体浓度边界层中的组成的差异是对核沸腾和对流蒸发中传热降解的传质阻力的表示。与液膜蒸发过程相比，传热系数与液界层中组分的变化关系最大。