Experimental Study on Performance and Energy-Saving Characteristics of Heat Pumps in Winter Multi-Climates

Air-source heat pumps suffer from significant performance degradation under low-temperature and humid-cold conditions, which restricts their adoption for clean heating across various climate zones in China. In this study, an experimental test platform was developed using a conventional single-stage air-source heat pump as a reference. Five representative cities were selected, covering severe-cold, cold, and hot-summer–cold-winter climate zones, and the winter temperature and humidity conditions of each city were simulated to replicate the corresponding ambient operating conditions. The variations in heating capacity, coefficient of performance (COP), and discharge temperature of both single-stage and quasi-two-stage heat pumps were compared and analyzed under diverse winter climatic conditions, and the energy-saving and environmental benefits of the system were evaluated. Compared with its single-stage counterpart, the quasi-two-stage air-source heat pump demonstrates an improvement in heating capacity ranging from 2.8% to 13.7% and an increase in COP between 0.6% and 7.3%. The energy-saving advantages are particularly pronounced in severe-cold regions. In the humid and cold areas of southern China, this technology effectively addresses the challenges of high energy consumption and insufficient heating capacity. Furthermore, the quasi-two-stage air-source heat pump system helps reduce power consumption during the heating season, thereby lowering carbon emissions and pollutant discharges associated with thermal power generation. This study provides experimental evidence to support the optimization and broader implementation of low-temperature heat pumps.