Long-Term System Performance of a Direct Expansion Solar Assisted Heat Pump

The long-term thermal performance of a direct expansion solar assisted heat pump is determined from the transient system simulation of the system. The system employs a bare collector which also acts as the heat pump evaporator. Of particular interest in this study is the configuration in which the compressor and the collector area are properly matched from the long-term thermal performance viewpoint. This matching is achieved through continuous as well as two step compressor capacity modulation. In addition to examining the effects of compressor capacity modulation, the effects of various system parameters such as collector area„ storage volume, load temperature, load profile, collector inclination, wind speed and refrigerant properties are also studied in some detail. The monthly averaged thermal performance parameters such as the collector efficiency and the heat, pump system coefficient of performance are determined by executing a computer simulation program which uses a typical meteorological year of solar da ta for Norfolk, Virginia. The results indicate that the system performance is governed strongly by collector area, compressor capacity, load temperature, and refrigerant properties. The remaining parameters have only weal& influence on the long-term system performance of the direct expansion solar assisted heat pump system considered in this study.