The study of nucleation site interactions on the mixed wettability rough surface

In order to achieve the best heat transfer performance on a mixed wettability surface, engineering of the wettability pattern is often used as heat transfer performance is significantly dependent on pitch distance between hydrophobic spots, which is maybe linked to the nucleation site interaction effects. In this work, the effects of nucleation site interactions between two hydrophobic cavities on a hydrophilic surface (a mixed wettability rough surface) are investigated, using a two-dimensional pseudopotential phase-change lattice Boltzmann method. The results of the mixed wettability rough surface are compared with completely hydrophilic rough surface and mixed wettability smooth surface to understand the effects of wettability and surface roughness. The focus is placed on the hydrodynamic interaction (which has promotive effect on the bubble formation activity) and thermal interaction (which has inhibitive effect). There exists an optimum pitch distance at which the heat flux and heat transfer coefficient are highest for mixed wettability surface, which are due to larger intensity of hydrodynamic interaction and nearly zero intensity of thermal interaction. Moreover, heat flux is found to be larger for the mixed wettability rough surface than the mixed wettability smooth surface. The bubble nucleation mechanism and time are found to be different for all surfaces.