There are many natural cold sources in the northern China in winter

and thermodynamic analysis shows that the heat released by the working medium subcooling can be compensated in the isothermal heat absorption process of the evaporator. To determine the influence of a natural cold source on the heating performance of a heat pump

an outdoor sub-cooler was added

and an air source heat pump experimental device using a natural cold source was built. The influence of subcooling on the heating performance of the air source heat pump was experimentally investigated. The experimental results show that subcooling has minimal influence on the heating capacity and heating coefficient of performance (COP) of the heat pump when the outdoor temperature is above 0 °C and the condensing temperature is less than 45 °C. The heating capacity of the system is maintained between 6.22and 6.70kW

the heating COP is maintained at approximately 3.03

and the discharge temperature of the compressor does not exceed 103 °C. However

when the outdoor and condensing temperatures are ?10 °C and 50 °C

respectively

as the subcooling increases

the compressor power and its discharge temperature increase significantly

the heating capacity of the system increases slightly at first and then decreases

and the heating COP decreases to 2.3. The results show the feasibility of the proposed air source heat pump system

which uses subcooling for defrosting and can achieve defrosting without stopping heating.