Heat transfer process and anti-frost performance of finned evaporator with air-water dual heat source for building heat supply

In this research, a dual heat source heat pump evaporator (AWSHP) with low-temperature hot water and air energy as the heat source is presented for the frosting problem of an air-source heat pump (ASHP) in low-temperature operating conditions. The critical frost region of the AWSHP system was also mapped using air temperature and water spray temperature as variables. The heat transfer characteristics as well as the anti-frost performance of AWSHP under different operating conditions were analyzed through experiments and simulations. According to the study's findings, the AWSHP system's refrigerant evaporation temperature was higher at the same ambient temperature than that of the ASHP. With AWSHP spray water volume of 8L/min and heat pump condenser circulating water volume of 15L/min, the average refrigerant heat exchanger and COP of AWSHP increased by 14.8% and 11.1%, respectively, compared with the ASHP system. At the same time, the AWSHP anti-frost operation strategy is proposed for low-temperature operating conditions. When the water spray volume was adjusted to 0.25 and 1.75 m(3)/h, respectively, under varying hourly meteorological conditions, the frost-free operation time was 61.21% and 89.24%, respectively. This was an improvement of 18.17% and 46.20%, respectively, compared to the ASHP.