Experimental research on a novel cold storage defrost method based on air bypass circulation and electric heater

Frost accumulation on evaporator decreased cooling capacity and COP (coefficient of performance) of cold storage refrigeration system, so timely and effective defrost was significant to cold storage energy-saving operation. The EHD (electric heat defrosting) method was commonly used in cold storages, however, defrost efficiency of the traditional EHD is rather low, and defrost operation usually caused an unfavorable storage temperature fluctuation, which is harmful to storage quality and shelf-life of stored products. In order to solve the problems existing in the traditional EHD method, a novel defrost method with air bypass circulation and electric heater was proposed for the first time in this paper. Five practical cases of this new method with different defrost heaters and air circulation modes were comparatively studied. The results showed that the case with heater embedded in evaporator fins and air circulating through bypass channel was the optimum implementation way of the new method. Compared with the traditional EHD method, the defrost time of this new method was shortened by 62.1%, defrost energy consumption was reduced by 61.0%, and storage temperature fluctuation was decreased by 70.1%. In addition, the defrost efficiency was up to 77.6%, which was 2.93 times of the traditional EHD method.