直膨式太阳能热泵热水器热力性能分析及优化设计

EXPERIMENTAL PERFORMANCE ANALYSIS AND OPTIMIZATION OF A DIRECT EXPANSION SOLAR ASSISTED HEAT PUMP WATER HEATER

针对"直膨式太阳能热泵热水器"750W实验样机(系统A)进行了过渡季节运行工况下的实验研究,根据实验数据计算出系统供热性能系数、太阳集热效率和各主要部件的有效能损失系数以及系统的有效能效率等热力学指标,对各部件可加以完善的潜力做了量化分析,为整套系统的进一步优化设计提供参考。根据分析结果,研制了小型化400W实验样机(系统B)并加以实验验证。通过对比分析发现,两套系统各主要部件的有效能损失以压缩机(其有效能损失系数,系统A为40%,系统B为34%)和太阳集热/蒸发器(其有效能损失系数,系统A为21%,系统B为37%)为最大,然后依次是冷凝器(其有效能损失系数,系统A为11%,系统B为8%)和热力膨胀阀(其有效能损失系数,系统A和系统B均为5%)。因此,压缩机的合理选配、集热器的优化设计是提高太阳能热泵热水器性能的关键。

A direct expansion solar assisted heat pump water heater （DX-SAHPWH） with 750W rated input power （i. e. DX-SAHPWH （A）） was tested and analyzed. Through experimental research in spring and thermodynamics analysis about the system performance, some suggestions for the system optimization were proposed. Then, a small type DX-SAH- PWH with 400W rated input power （i. e. DX-SAHPWH （B）） was built, tested and analyzed. Through exergy analysis for each component of DX-SAHPWH （A） and （B）, it can be seen that the highest exergy loss occurs in the compressor （ Xccmp is 40% in the DX-SAHPWH （A） and 34% in the DX-SAHPWH （B）） and collector/evaporator （ Xeva is 21% in the DX-SAHPWH （A） and 37% in the DX-SAHPWH （B））, followed by the condenser （Xcend is 11% in the DX-SAHP- WH （A） and 8% in the DX-SAHPWH （B）） and expansion valve （Xv is both 5% in the DX-SAHPWH （A） and in the DX-SAHPWH （B））, respectively. Further more, some methods were suggested to improve the performance of each component. In order to maintain an all-year proper matching between the heat pumping capacity of the compressor and the evaporative capacity of the collector/evaporator under widely varying ambient conditions, the variable frequency compressor and electronic expansion valve were suggested to be utilized for the DX-SAHPWH.