Abstract: In terms of theory, the contact between the microchannel flat tube and the water tank is surface contact, the traditional copper tube outer-coil contact area with the out wall of the tank is line contact, it is obvious that the contact area of the microchannel is larger, which is beneficial to the heat exchange between the water and the water tank, and also enhances the energy efficiency. At present, in the market of heat pump water heaters, it is concluded that most manufacturers are using microchannel enamel outer-coil water tank, and most are high energy-efficient products, only a few manufacturers are using copper outer-coil water tank. By testing and comparing the copper tube outer-coil water tank and the microchannel enamel outer-coil water tank, it is concluded that the microchannel enamel outer-coil water tank is better than the copper tube outer-coil water tank in terms of energy efficiency and heating capacity, and reduces a certain amount of refrigerant charge. It helps to improve the heating capacity and the energy efficiency, so that finally improve the production of hot water effectively.

Key words: Heat pump water heater, Microchannel heat exchanger, Enamel outer-coil water tanky