Visualization of Patterned Modified Surfaces in Condensation and Frosting States

In this study, a novel, thorn-shaped, containing, hydrophilic, and hydrophobic surface is proposed to have a better condensate drainage characteristic and to delay the required time for frosting. By using a hydrophilic and hydrophobic mixed thorn-shaped surface created by screen printing, the design makes use of the differences in the wettability gradient to achieve rapid condensate drainage and to lengthen the time for frosting. The results of a frosting experiment indicated that the droplet adsorption and combination and discharge effect in the thorn sample were substantial. The drainage effect increased the surface renewal rate and inhibited ice layer growth on the thorn sample by 52.4% compared with that on pure copper surface. The heat transfer coefficient of the thorn sample during frosting was approximately 16.2% higher than that of pure copper surface. In addition, the defrosting results indicated that the defrosting time of the thorn sample was almost equal to that of the pure copper sample. However, large droplets were easily stagnated at the structural junction due to contact angle hysteresis after defrosting.