A novel thermal energy storage based reversed-cycle defrosting technology for Air-to-air heat pumps

Frost formed on outdoor unit's coil surface of Air Source Heat Pumps (ASHPs) deteriorates its operational performance. Currently, the most widely used defrosting method for ASHPs is reversed-cycle defrosting.. However, insufficient heat available during defrosting is a fundamental problem for traditional reversed-cycle defrosting, with which a number of operational problems during defrosting for AAHPs are associated. In the paper a novel thermal energy storage (TES) based reversed-cycle defrosting method for Air-to-air heat pump (AAHP) using phase change material (PCM) was presented. When an AAHP. worked at high efficiency, excess energy was stored in the container filled with PCM, and when defrosting was necessary the energy stored previously was released through reversed-cycle of the heat pump. The schematics, operational modes of AAHP using the such defrosting method were introduced in detail, and the experiment were carried out. Experimental results indicated that the novel reverse defrosting method can help increase an AAHP' s energy efficiency and effectively eliminate a series of problems including a longer defrosting time, a reduced indoor thermal comfort for occupants and a poorer system reliability and etc that can't be solved by traditional reversed-cycle defrosting method.