Visualization study of the effect of surface contact angle on frost melting process under different frosting conditions

• The effect of surface contact angle on frost melting is studied.
• The effect of frosting time on frost melting is studied.
• The frost melting behavior in multiple frosting cycles is studied.

Frost melting is closely related to solid surface characteristics and initial frost layer. In this paper, visualization study of frost melting processes on different surfaces, from hydrophilic to superhydrophobic, was carried out under different frosting conditions. On the hydrophilic and hydrophobic surfaces, the whole frost layer is divided into several blocks accompanying with melting, and the frost-water mixed blocks finally shrink into water droplets because of the surface tension and surface free energy. However, frost layer directly sheds from the superhydrophobic surface and only several spherical water droplets remain on the surface. The surface coverage ratio and frost-melting water mass all decrease with the increase in surface contact angle, which are smallest on the superhydrophobic surface. The frosting time and multiple frosting cycles show significant effects on frost melting of the hydrophilic and hydrophobic surfaces while frosting time and multiple frosting cycles have no influence on that of the superhydrophobic surface.