Experimental study on effect of surface characteristic of fin on frost formation

In order to study the effect of the surface characteristic of fin on frost formation of an air source heat pump, a frosting experimental system for fin was developed. The microscopic characteristics of frost formation of four different fin surfaces with different contact angles were investigated visually. The effect laws of the surface characteristic of fin on the microscopic characteristics of frost formation and the thermal performances of frost layer were obtained. The experimental results show that the sizes of condensate water droplets are smaller, the distribution is sparser and the freezing time of water droplets is longer on the fin surface with bigger contact angle during the initial period of frost crystals growth. During the process of frost layer growth, frost crystals are relatively small, loose and unevenly distributed on the fin surface with big contact angle, while they are long, dense and evenly distributed on the fin surface with small contact angle. The height, surface temperature and thermal conductivity of the frost layer all decrease with the increase of the contact angle. The height of the frost layer of the superhydrophobic surface decreases by 45% compared with that of the hydrophilic surface. The anti-frosting performance is better when the contact angle of the fin surface is bigger.