A molecular dynamics investigation on the effects of electrostatic forces on nanoscale thin film evaporation

U Gonzalez-Valle and B Ramos-Alvarado, INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, 182, 121981 (2022).

DOI: 10.1016/j.ijheatmasstransfer.2021.121981

Thin-film evaporation is relevant for electronics cooling, water desalination, and some energy conversion processes, and the overall performance of such applications relies on the adequate understanding of heating-induced phase-change mechanisms. Given the importance of polar compounds, such as alumina, for nanoporous membranes in water desalination, the effects of electrostatic forces on thin-film evaporation were investigated in this paper by means of molecular dynamics simulations. The influence of the electrostatic interactions was assessed by modelling the alumina-water interactions using two approaches: i) accounting for electrostatic and dispersive van der Waals (vdWs) forces between the solid and liquid atoms (LJ + Coulombic model), and ii) considering only dispersive vdWs interactions (LJ model). Additionally, a theoretical model based on the Schrage relationships was developed to compare theory and simulations. The results showed considerable differences in the evaporation rates obtained from the two interfacial models. For the LJ + Coulombic model, the liquid films were 40% thicker, and the maximum evaporation mass flux was lower than the LJ model by a factor of two. The theoretical Schrage relationships deviated from the simulation evaporation fluxes with errors of 2.2-18.1% and 24.0-57.9% for the LJ + Coulombic and LJ models, respectively. These observations suggest that the partial charges in the solid affect the evaporation behavior of water if the films are similar to 5 nm or thinner. Moreover, the significant deviations in the evaporation behavior demonstrated the importance of a robust interfacial modelling approach to investigate thin-film evaporation in polar interfaces. (c) 2021 Elsevier Ltd. All rights reserved.

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