Operating performance of a solar/air-dual source heat pump system under various refrigerant flow rates and distributions

Rational utilization of renewable energy is widely used to reduce building energy consumption and save energy. To promote the utilization efficiency of renewable energy in cold climate regions especially plateau area, a novel solar/air-dual source heat pump system used for space heating was proposed and investigated in this paper.

Based on a demonstration building in Qinghai-Tibetan Plateau, a dynamic simulation model was initially established by TRNSYS and validated by the experimental data. An idea of controlling refrigerant flow distribution was adopted in the coupling heat pump. Subsequently, the performance of the dual-source heat pump under various refrigerant flow rates and various ratios of refrigerant flowing into solar collector and evaporator was investigated and optimized.

Results show that the optimal indoor temperature and coefficient of performance could be achieved when the refrigerant flow is 16 g/s. And when the ratio of the refrigerant entering into solar collector ranges 0.6–0.7, the result is the best. Simultaneously, the monthly average coefficient of performance of the dual-source heat pump could reach 3.6 generally, and the annual average indoor temperature of the building would be over 20 °C.

The research suggests that the refrigerant flow rate has a significant effect on the performance of the dual-source heat pump, and appropriate ratio of refrigerant flowing into solar collector and evaporator can improve the performance. This paper could be as a reliable reference for an application of the solar/air-dual source heat pump system in severe cold region.