Lattice Boltzmann simulation of dropwise condensation on the microstructured surfaces with different wettability and morphologies

Abstract

Dropwise condensation heat transfer on the different microstructured surfaces is simulated by 2D hybrid thermal lattice Boltzmann method. Dynamic behaviors of condensate droplets on the microstructured surfaces are investigated. Moreover, the influence of surface wettability, surface microstructure and subcooling degree on the condensate dynamics and heat transfer performance is analyzed. Our numerical results demonstrate that condensate microdroplets preferentially appear to form at the valley or side of micropillar arrays. As the condensation progresses, the condensate mass and condensation rate of the superhydrophobic surface eventually exceed those of the hydrophilic and hydrophobic surfaces. The heat flux of superhydrophobic surface with θa = 150.7° is the highest. The local heat flux at the top of micropillars is much higher than that at the bottom of micropillars. The microstructured surface with a smaller spacing is beneficial to increasing the condensate nucleation population, whereas a larger spacing can strengthen the jumping abilities of coalesced droplets. During condensation, the average heat flux fluctuates locally with time caused by the merging and jumping dynamics. Although the superhydrophobic surface with triangle microstructure improves the jumping height of coalesced droplets, the heat flux of triangle microstructured surface is significantly smaller over that of the square and semicircular microstructured surfaces. Despite a greater subcooling degree facilitates the condensation heat transfer, it has a negative influence on the jumping height of droplets. This numerical study illustrates the microscopic mechanism of dropwise condensation heat transfer in detail.