Molecular Dynamics Study on Interphase Mass Transfer between Liquid and Vapor Phases. Effects of Translational Energy on Condensation and Evaporation Coefficients.

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Molecular dynamics simulations have been conducted for a monatomic-molecule system in order to understand the effects of translational motion on condensation and evaporation. The condensation probability of an argon molecule was examined by injecting a test molecule into the liquid system with a different translational energy. For evaporated and reflected molecules, velocity distributions in the vicinity of the liquid surface were measured and compared with the Maxwellian distribution. The results show that both condensation and evaporation coefficients depend on the normal component of translational energy. The condensation coefficient increases with an increase in incident energy because it can penetrate the liquid surface. Likewise, the evaporation coefficient increases with translational energy because of its increasing ability to escape from the liquid surface. It was also found that the velocity distributions of evaporated and reflected molecules should be expressed using the condensation/evaporation coefficient.