Effects of surface characteristic on frosting and defrosting behaviors of fin-tube heat exchangers

Surface characteristic is one of the most important factors that affect the frosting and defrosting behaviors of a fin-tube heat exchanger in an air source heat pump. In this paper, three types of fin-tube heat exchangers with different surface characteristics were prepared and the effects of the surface characteristic on the frosting and defrosting behaviors of the heat exchangers were investigated experimentally. It was found that the surface characteristic had an obvious effect on the frost layer growth. The frost thickness and mass of the superhydrophobic heat exchanger were 17.1% and 28.8% less than those of the bare heat exchanger. What is more, the superhydrophobic heat exchanger showed the lowest air-side pressure drop and the best heat transfer during the frosting process. The effects of the surface characteristic on the energy consumption and time for frost melting were significant. When the frost layer melted completely, the retained water formed a thin water film on the surfaces of the hydrophilic fins while only some small spherical droplets stayed on the surfaces of the superhydrophobic fins. The least retained water on the superhydrophobic heat exchanger can reduce the energy consumption for evaporation and improve the defrosting efficiency.