Abstract: Traditional heat pump air conditioners experience frequent frosting and defrosting in low-temperature environments, leading to a significant decline in continuous heating performance, which restricts the promotion and application of heat pump air conditioners. In response to these issues, conducts theoretical analysis and experimental verification on the impact of system parameters such as compressor frequency, electronic expansion valve opening, and exhaust temperature during low-temperature heating operation, as well as the changes in heat exchanger tube temperature on heating performance and frosting/defrosting conditions. The results show that improving low-temperature heating performance requires a comprehensive consideration of the effects of compressor operating frequency, electronic expansion valve opening, and heat exchanger tube temperature; it is possible to appropriately increase the evaporating pressure and temperature of the air conditioning system to weaken the impact of outdoor heat exchanger frosting and defrosting on low-temperature heating performance; during the operation phase before entering defrosting, it should be avoided to continuously reduce the opening of the electronic expansion valve, which would decrease the circulation flow of the air conditioning system and thus accelerate the rapid decline of the system’s low-temperature heating performance.

Key words: Heat pump air conditioner, Low-temperature heating performance, Theoretical analysis, Experimental verification