Abstract: The thermal performance of the air source heat pump becomes worse when the outdoor finned tube heat exchanger frosting, it affects the safe and stable operation of the heat pump system at the same time. So delaying the frosting of the outdoor heat exchanger will significantly improve the thermal performance and indoor thermal comfortability of the heat pump system, ensuring the reliable operation of the heat pump unit. Based on the air enthalpy difference test platform, the process of frosting/defrosting for two different finned tube heat exchanger using hydrophilic coating and super-hydrophobic coating was compared under the condition of 2/1℃ dry /wet bulb temperature and with a wind velocity of 1.5m/s in front of the heat exchanger.Results show that, the fin tube heat exchanger using super-hydrophobic coating could effectively inhibit the formation of frost layer and delaying the frosting cycle, improving the performance of the heat exchanger under the low temperature conditions. Comparing with the hydrophilic coating, the frosting cycle of super-hydrophobic coating increased by 87.5%. The heat transfer capacity also raised 8.4%, accordingly. This paper is helpful for the design and operation of the air source heat pump system.

Key words: Air source heat pump, Finned tube heat exchanger, Super-hydrophobic coating