Experimental study on characteristic of thermal energy storage defrosting for air source heat pump using sub-cooling energy of refrigerant

This study is concerned with a thermal energy storage defrosting (TESD) based on reverse cycle defrosting method for air source heat pump (ASHP) using sub-cooling energy of refrigerant to eliminate frost on surface of outdoor coil. The feasibility of thermal energy storage using sub-cooling energy of refrigerant and defrosting were investigated experimentally. The defrosting performances were compared with a normal 850 W capacity ASHP system standard reverse cycle defrosting (SRCD) method. The results indicate that by the TESD for ASHP using sub-cooling energy of refrigerant method, the system coefficient of performance in heating can be improved due to the sub-cooling of refrigerant outlet of indoor coil, defrosting duration and re-heating time can be shortened, and the indoor thermal comfort can be improved when defrosting and re-heating. During defrosting duration, TESD for ASHP using sub-cooling energy of refrigerant method improves discharge and suction pressures by 0.57 MPa and 0.11 MPa, respectively, also shortens defrosting duration and re-heating time by 30.8% and 25% in the tested environment, and reduces defrosting power consumption by 22.8kJ, relative to the SRCD method.