Effects of contact angle hysteresis on frosting and defrosting characteristics on vertical superhydrophobic surfaces

Abstract

Contact angle hysteresis has a significant influence on dynamic frosting and defrosting of vertical superhydrophobic surface, however, the characteristics under the effect of contact angle hysteresis have not been clarified. Therefore, superhydrophobic surfaces with similar contact angles but different contact angle hysteresis were prepared in this paper, and visualization experiment was carried out to discover the effects of contact angle hysteresis on frosting and defrosting characteristics of vertical superhydrophobic surface. Experimental results show that the bounce behavior, size, distribution density and freezing time of condensate droplets are obviously different in the early stage of frosting, and reducing the hysteresis of superhydrophobic surface reduces the distribution of condensate droplets and effectively delay droplet freezing. The anti-frosting performance of the superhydrophobic surface is improved with the decrease of contact angle hysteresis. The frost layer thickness of the surface with the smallest contact angle hysteresis is 50% lower than that of the surface with the smallest. The frost layer peels off from the superhydrophobic surface with smallest contact angle hysteresis at the beginning of defrosting and falls away under the action of gravity. This can effectively improve the defrosting efficiency by reducing defrosting time and retained defrosting water.