Numerical Investigation of Vapor Condensation on a Hierarchical Microstructured Surface with a Phase-Change LB Method

Nucleation and growth of condensation droplets on a hierarchical microstructured surface are studied by using a two-dimensional phase-change lattice Boltzmann method. The parametric effects of orientation, height, and spacing of secondary pillars located on the primary pillars as well as the effects of wettability and subcooling on condensation heat transfer are discussed comprehensively. The results show that secondary pillars play a significant role in vapor condensation. Compared with the single microstructured surface, the heat transfer ability of the hierarchical microstructured surface can be enhanced by 15.2%. With the increase in the height of secondary pillars on the top of primary pillars, the condensation mode changes from filmwise to dropwise condensation. The secondary pillars on the groove base of primary pillars can change the sites of nucleation, and the nucleation time decreases with the increase in pillar height. Cavitation phenomena take place within gaps between microstructures when the distance between structures is small. In addition, the increase in surface subcooling or the decrease in the contact angle can lead to filmwise condensation, and the heat transfer performance increases in accordance. This study provides a fundamental understanding of condensation on a hierarchical microstructured surface through a numerical view.