Performance investigation of a transcritical CO2 heat pump combined with the terminal of radiator and floor radiant coil for space heating in different climates, China

CO2 air-source heat pump is regarded as a promising technology for domestic hot water and automotive air-conditioning system. However, its coefficient of performance is not very satisfactory when it is used for space heating in winter, while this phenomenon is more obvious at the condition of taking conventional radiator as a heating terminal unit. To cope with this issue, a transcritical CO2 air-source heat pump system combined with the terminal of radiator and floor radiant coil for space heating was developed in this paper, for fulfilling the energy cascade utilization. The performance and feasibility of the studied system were investigated using Transient System Simulation Program and compared with a benchmark system in five locations with different climate zones, China. The results showed that, taken Shenyang as an example, the inlet water temperature of heat pump unit of the studied system and the benchmark system were 36 degrees C and 50 degrees C respectively. Also the average co-efficient of performance and heating seasonal performance factor of CO2 air-source heat pump unit were 17%- 28% and 9%-22% higher, respectively, compared with the benchmark system during the entire heating period. This study is helpful to improve the application of transcritical CO2 air-source heat pump for space heating in severe and cold zones in China.