Effects of Roughness of Solid Surface With Nano-Relief on Liquid-Wall Contact Angle

The liquid-wall contact angle reflects the liquid wettability, the front size of thin liquid film, it is important for micro space phase change heat transfer. The smooth solid wall is supposed to have a periodic nano-relief, which has a roughness height and a roughness angle microscopically. The analytical contact angles are derived by the adsorptive potential and the disjoining pressure of adsorbed thin liquid film, depends on the scales of nano-relief and outside applying conditions. The results show that the adsorptive potential and the disjoining pressure of adsorbed thin liquid film will be affected by the nano-relief significantly when the roughness height is closer to the thickness of adsorbed thin liquid film. For apolar working fluids, if the roughness is medium, the analytical liquid contact angles are of the order of 0.01⁰∼0.1⁰ degree; if the roughness is extremely, then nano-relief of surface will exert stronger influences on the contact angles, the contact angle is nearly 90 degrees.