Experimental and theoretical study of frost melting water retention on fin surfaces with different surface characteristics

• The effects of fin surface characteristics on frost melt water retention were studied.
• The effect of frosting time on retained water mass was investigated.
• A mathematical model was developed for predicting the maximum retained droplet radius and retained water mass.
• The model was verify to be accurate when the contact angle lied in the range of 110–150°.

There is some frost melting water retention on the surface of fin-tube heat exchanger during defrosting process. It takes much time and energy to evaporate the retained water. In this paper, the effect of fin surface characteristic on frost melting water retention is investigated experimentally. Visualization experiment shows that fin surface characteristic has a significant influence on water retention. The retained water forms a thin water film on the hydrophilic fin, while only a few small spherical droplets stay on the superhydrophobic fin. The retained water mass of the superhydrophobic fin decreases by 79.82%, 75.82% and 66.15% compared with that of the hydrophilic, bare and hydrophobic fins, respectively. The frosting time over 30 min has a subtle effect on retained water mass of the hydrophobic and superhydrophobic fins. A mathematical model, which considers the surface contact angle and contact angle hysteresis, is further developed to predict the maximum retained droplet radius and retained water mass. The model is verified to be accurate when the contact angle lied in the range of 110–150°.