Molecular transport across a steady-state net condensing surface

Abstract

This study investigates interfacial mass and thermal transport across a steady-state flat condensing interface under non-equilibrium thermodynamic conditions. A phase-change driven nanopump, comprising liquid argon placed between parallel platinum plates, has been studied using non-equilibrium molecular dynamics simulations. This setup allows for a continuous examination of steady-state evaporation and condensation phenomena as the system achieves a statistically steady transport. We examined temperature profiles and the associated temperature jumps that occur within the finite interfacial region under various heat fluxes. We explored the correlation between these temperature jumps and the energetics of atoms crossing the interface. Hertz-Knudsen & Schrage models, widely used by many to calculate interfacial mass transport, use the mass accommodation coefficient(s) to compute mass flux. This research utilizes a Lagrangian framework to decompose the total mass flux into its constituent evaporation and condensation components. The study further calculates the evaporation and condensation coefficients using both the models and measured probabilistic values from the Lagrangian framework, providing a comparative analysis of the two approaches. This study presents a comprehensive analysis of net condensation at the liquid-vapor interface using a Lagrangian framework, challenging the applicability of classical kinetic theory models. Notably, the Schrage model exhibits a strong agreement with the Lagrangian framework, reinforcing its relevance in modeling interfacial mass transport.