Icing and deicing of a sessile droplet on superhydrophobic surfaces

Icing exist widely in nature and in industry, causing numerous problems such as imperiling the flight safety of an aircraft, deteriorating the heat transfer of a heat exchanger, and reducing the power generation efficiency of a wind turbine. When the exposed temperature is too low, icing is inevitable even on a superhydrophobic surface. So deicing is essential. In this work, we investigate the icing and deicing characteristics of a sessile droplet on an Al-based superhydrophobic surface and aim to understand the surface and interface phenomena occurred during icing and deicing. During icing, ice front always propagates from the bottom of the droplet, finally forming a singular tip at the droplet top, while the nucleation position is various under different conditions. When the surround air is very humid, the nucleation tends to appear at the solid-liquid interface of the droplet; otherwise, the nucleation appears at the liquid-air interface of the droplet. During deicing, melting also first occurs at the bottom of the freezing droplet, but the ice-water interface is more flexible compared with that during icing with obvious swaying and rotating behavior of the unmelted ice cover. The possible Marangoni effect occurred during deicing may be the reason for these behavior.