Numerical Investigation on Dropwise Condensation on Rough Structures with and without Non-Condensable Gas

The geometrical dimensions of the rough structures as well as the non-condensable gases in the vapor mixture can have the great effect on the nucleation position and the wetting state of the droplet, which further influence the condensation heat flux. In this paper, the multispecies multiphase lattice Boltzmann method together with a thermal phase change model is used to investigate the dropwise condensation on a rough surface enhanced with pillars. The effect of the geometric dimensions including pillar height H, pillar width W and pillar space S is investigated. Then the effect of non-condensable gases on the contact angle of a droplet on textured surface is studied. The results show that the local heat flux and the wetting area are higher while the waiting time is shorter at larger S, W and smaller H on the rough surface. The nucleation position rises from the bottom of grooves to the top with the increase of pillar height and the decrease of pillar space. The contact angle is larger and it is easier to maintain the Cassie state for droplet. When there exists non-condensable gas, the non-condensable gas obviously enhances the hydrophobicity of the rough surfaces compared with pure vapor.