Performance investigation on a novel air-source heat pump using CO2/HC for recirculated water heater in cold regions

Heat pump becomes attractive for recirculated hot water heating in cold regions, whereas conventional configurations face difficulties in operation at low ambient temperatures. A novel single-stage air-source heat pump using eco-friendly CO2/HC is proposed in this paper. The novel heat pump is featured by independent regulation of operating parameters according to the change of ambient condition. Through parametric analyses, the positive effects of the design of branches in the novel heat pump are demonstrated for reducing irreversible losses. The underlying mechanism of the superiority of the novel heat pump is revealed that, the application of suitable eco-friendly CO2/HC and the optimization of operating parameters result in lower compression ratio and optimized irreversible loss in recuperator. Under supply/return water temperatures of 75 °C/50 °C and ambient temperatures ranging from −30 °C to 10 °C, better heating seasonal performance factor and higher volumetric heating capacity of the novel heat pump are obtained, compared with conventional heat pumps. With the application of low-GWP refrigerant and the achievement of high seasonal performance during wintertime, the novel heat pump in this paper exhibits great potential in sustainable development for heating technology in regards of reduction of energy consumption and pollutant emission.