Thin-film phase change driven by disjoining pressure difference

Abstract

The thin liquid film at the contact line is gaining increasing attention due to its importance in phase-change heat transfer and wettability control. The intermolecular effects within the thin film are usually represented by of disjoining pressure. In the present work, molecular dynamics were employed to investigate the influence of disjoining pressure on thin–film evaporation and condensation in a nanoscale triple-phase system. The simulation domain was a cuboid with argon gas sandwiched between the two solid platinum walls. The two solid walls were fixed at the same temperature while the liquid films had different initial thicknesses thus corresponding to different disjoining pressures. Spontaneous evaporation and condensation were observed at the thicker and the thinner film, respectively. Disjoining pressure together with thermodynamics theories were employed to qualitatively and quantitatively explain the phenomenon. The evaporation fluxes were measured and compared to the Hertz-Knudsen-Schrage model which is based on the kinetic theory of gases. The resulting non-evaporating thickness was measured and compared to the models based on disjoining theory.