低温室效应二元混合工质R1234ze/R152a的管内流动相变传热特性研究

基于环保需要，项目组拟以低GWP混合工质R1234ze/R152a替代R22，因此，有必要开展该混合工质热力学性质及其相变传热特性研究。首先，通过实验测出R1234ze/R152a在一定温度范围内的气液相平衡（VLE）数据，建立气液相平衡行为计算模型，并开发该混合工质热力学性质专用计算程序；然后，完成不同工况下沸腾传热与冷凝传热特性实验，分析组分比、质量流速、饱和温度、热流密度以及传热管结构尺寸等参数对传热系数和压降梯度的影响，并基于实验数据得出适合R1234ze/R152a的沸腾、冷凝传热系数预测关联式和压降梯度预测关联式；利用流动传热传质和空泡份额理论，结合热力学性质与管内相变传热实验数据，通过数值模拟构建该混合工质的管内流动相变传热模型，提出强化相变传热的优化方案；最后，结合理论分析、实验研究与数值模拟，总结出R1234ze/R152a在水平管管内的流动相变传热规律。

The project team plans to replace R22 with low-GWP refrigerant mixture R1234ze/R152a based on environmental protection. Therefore, it is necessary to carry out research on the thermodynamic properties and the phase change heat transfer characteristics of the refrigerant mixture. Firstly, the vapor-liquid equilibrium(VLE) of R1234ze/R152a in a desired temperature range will be measured by experiments, the calculation model of vapor-liquid equilibrium behavior will be established, and the special calculation program of thermodynamic properties of the refrigerant mixture will be developed. Then the experiment of boiling, condensation heat transfer and pressure drop characteristics under different conditions will be carried out and the effects of components, mass flux, saturation temperature, heat flux, vapor quality and tube size etc. on the heat transfer coefficient and pressure drop will be analyzed, and the predicted correlations of boiling and condensation heat transfer coefficient as well as pressure drop for R1234ze/R152a will be proposed. Afterward, combined with the thermodynamic properties of the refrigerant mixture and the experimental data of phase change heat transfer in tubes, the phase change heat transfer model of R1234ze/R152a flowing in horizontal tubes will be constructed based on the theory of flow heat and mass transfer and void fraction, the optimization scheme of enhanced heat transfer will be proposed by numerical simulation. Finally, combined with theoretical analysis, experimental research and numerical simulation, the flow and phase change heat transfer law of R1234ze/R152a in horizontal tubes will be summarized.