Development of a High Performance Heat Pump System Using Refrigerant Mixtures as Working Fluids

本项目旨在开发使用共沸制冷剂混合物作为工作流体的高性能蒸汽压缩热泵/制冷系统。本课题采用由密闭式压缩机、立式板翅式冷凝器、膨胀阀和降膜式板翅式蒸发器组成的蒸汽压缩热泵系统，对HFC134a/HCFC123和HCFC22/CFC114两种混合物的循环性能进行了实验研究。在较宽的热流密度和质量速度范围内，对板翅式换热器中制冷剂冷凝和蒸发的传热特性和流态进行了测试。结果如下：(1)循环性能研究了制冷剂组成、热源和散热器条件对循环性能系数的影响，明确了采用共沸制冷剂混合物改善COP的必要条件；最佳的c…More条件是由共沸制冷剂混合物的热力学性质和传热性能决定的。(2)降膜式板式翅片蒸发器内共沸制冷剂混合物的传热在进行蒸发传热实验之前，对几种试验液体分布器进行了试验，建立了降膜式蒸发器内制冷剂液体均匀分布的方法。制作试验蒸发器，在质量速度G=28 ~ 70 kg/(m2 s)范围内进行试验。通过观察，将液膜的流动形态划分为平面液膜、波浪状液膜、干斑液膜、滴状液膜和雾状液膜五种典型类型。在此基础上，阐明了传热与流型之间的关系。提出了预测纯制冷剂和混合制冷剂传热特性的方法。(3)共沸制冷剂混合在板翅式冷凝器中的换热研究发现，在板翅式冷凝器中，纯制冷剂的换热系数比纯制冷剂液膜在光滑表面下降的半经验方程所预测的换热系数高10倍左右，并且混合制冷剂的换热系数随质量分数和质量速度的不同而低于纯制冷剂。提出了预测纯制冷剂和混合制冷剂传热特性的方法。少

This project aims to contribute the development of high-performance vapor compression heat pump/ refrigeration systems using zeotropic refrigerant mixtures as working fluids. In this project the cycle performance was investigated experimentally for two kinds of mixtures of HFC134a/HCFC123 and HCFC22/CFC114 using a vapor compression heat pump system, which consisted of a hermetic type compressor, a vertical plate-fin condenser, an expansion value and a falling-film type plate-fin evaporator. The characteristics of heat transfer and flow pattern of refrigerant condensing and evaporating in plate-fin heat exchangers were also tested in wide ranges of heat flux and mass velocity. The results obtained are as follows :(1) Cycle PerformanceThe effect of the refrigerant composition, heat source and heat sink conditions on the coefficient of performance was investigated, and the necessary conditions for improvement in the COP by using zeotropic refrigerant mixtures was clarified ; the optimum c … More ondition is determined by the thermodynamic properties and the heat transfer performance of zeotropic refrigerant mixtures.(2) Heat Transfer of Zeotropic Refrigerant Mixture in A Falling-film-type Plate-fin EvaporatorPrior to the experiment on the evaporation heat transfer, several kinds of trial liquid distributors were tested, and the method to distribute the refrigerant liquid uniformly in an falling-film type evaporator was founded. The test evaporator was manufactured and tested in the range of mass velocity G=28-70 kg/(m2 s). From the observation, the flow patterns were classified into five typical types : plane liquid film, wavy liquid film, liquid film with dry patch, liquid film with dripping and liquid film with mists. Then, the relation between the heat transfer and the flow pattern was clarified. The method to predict the heat transfer characteristics of pure and mixed refrigerants was also developed.(3) Heat Transfer of Zeotropic Refrigerant Mixture in A Plate-fin CondenserIt was founded that the heat transfer coefficients of pure refrigerants in a plate-fin condenser were about 10 times higher than the values predicted by a semi-empirical equation for falling liquid film of a pure refrigerant on a smooth surface, and the heat transfer coefficients of mixed refrigerants were lower than those of pure refrigerants depending on the mass fraction and the mass velocity. The method to predict the heat transfer characteristics of pure and mixed refrigerants was also developed. Less