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

该项目旨在促进以共沸制冷剂混合物为工质的高性能蒸汽压缩热泵/制冷系统的开发。本项目采用蒸汽压缩热泵系统对HFC134a/HCFC123和HCFC22/CFC114两种混合工质的循环性能进行了实验研究，该系统由密封式压缩机、立式板翅式冷凝器、膨胀阀和降膜式板翅式蒸发器组成。在较宽的热流密度和质量流速范围内，对板翅式换热器内制冷剂冷凝和蒸发的换热和流态进行了实验研究。(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，明确了采用共沸混合工质提高COP的必要条件；确定了最佳的c…。共沸混合工质在降膜式板翅式蒸发器中的传热性能。(2)共沸混合工质在降膜式板翅式蒸发器中的传热实验在进行蒸发换热实验之前，对几种液体分布器进行了测试，建立了降膜式蒸发器中制冷剂液体均匀分布的方法。实验蒸发器是在质量流速G=28-70 kg/(m2·S)的范围内制造和测试的。通过观察，将流型划分为平面液膜、波状液膜、干斑液膜、滴状液膜和雾状液膜五种典型流型。阐明了换热与流型之间的关系。(3)共沸混合工质在板翅式冷凝器中的换热研究发现，纯制冷剂在板翅式冷凝器中的换热系数约为纯制冷剂在光滑表面下降液膜的半经验公式预测值的10倍，混合工质的换热系数随质量分数和质量速度的变化而降低。建立了预测纯工质和混合工质换热特性的方法。较少

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