Formation of Liquid Film in Heterogeneous Condensation of Water Vapor: Effects of Solid-Fluid Interaction and Sulfuric Acid Component

SH Lyu and ZZ Tang and Q Song and Z Yang and YY Duan, LANGMUIR, 38, 7085-7097 (2022).

DOI: 10.1021/acs.langmuir.2c00949

Understanding the phenomenon offilmwise con-densation on solid surfaces is vital for industrial processes such asair pollutant control and desalination. In this work, we study theformation of condensed liquidfilms via molecular dynamicssimulations, and the effects of solid- fluid interactions and thesulfuric acid component are given major attention. Water is chosenas thefluid, while the solid-fluid interaction is modified tocharacterize different solid surfaces. The results show that as thesolid-fluid interaction decreases, the solid surface transforms froma completely wetting surface to a partially wetting surface, and thefilm formation process shows significant differences. The condensed liquid on the completely wetting surface forms small liquidfilms, which merge to form a completefilm covering the surface. With the enhancement of solid-fluid interaction, the condensationrate increasesfirst and then remains virtually invariant, resulting in afilm formation time that decreasesfirst and then maintainsconstant. The condensed liquid on the partially wetting surfaces appears as nanodroplets, and the coalescence between nanodropletsleads to the formation of the liquidfilm. It is found that the stronger the solid- fluid interaction, the more the coalesced dropletstend to be pinned at nucleation sites, the easier it is to form a liquidfilm, and the shorter the time required for droplet merging. Thesulfuric acid component accelerates liquidfilm formation on both completely wetting and partially wetting surfaces, but the effect ofsulfuric acid is more significant on partially wetting surfaces. The 5% molar fraction of sulfuric acid reduces the nucleation time by72% and increases the condensation rate by 137% under partial wetting, while the same amount of sulfuric acid only increases thenucleation rate by 6% on the completely wetting surface.

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