Assessing the impact of disjoining pressure on thin-film evaporation with atomistic simulation and kinetic theory
Xiaoman Wang, Li Yang, Jonathan A. Malen, Alan J. H. McGaughey
Abstract
Molecular dynamics (MD) simulations are applied to validate the Hertz–Knudsen–Schrage (HKS) relation for the evaporation mass flux in the presence of disjoining pressure. A non-equilibrium MD simulation system is designed to directly extract the evaporation mass flux for a Lennard-Jones fluid. The temperatures, pressures, properties, and disjoining pressure required to evaluate the HKS relation are obtained from the non-equilibrium MD simulation and complementary equilibrium MD simulations. The direct MD evaporation mass flux and that from the HKS relation agree within 10%. We define an evaporation Kapitza length that estimates where the liquid conduction and evaporation thermal resistances are equal. We propose that surface structures that promote film thicknesses comparable to or smaller than the evaporation Kapitza length, but larger than the adsorbed film thickness, will maximize the evaporation rate.