Molecular dynamics simulation of effective thermal conductivity of vapor-filled nanogap and nanocavity

Abstract

The effect of adsorption on momentum au and thermal aT accommodation coefficients and effective thermal conductivity ⟨kf⟩ of Ar vapor-filled Pt nanogap and nanocavity is examined using nonequilibrium molecular dynamics (MD) simulations. For the accommodation coefficients, the increase in solid-fluid or fluid-fluid interatomic interactions within adsorbed layer causes transitions in magnitudes of au and aT near Ar triple-point temperature. In the nanogap, ⟨kf⟩ MD results are in close agreement with the available closed-form solution for transition-flow regime, i.e., Knudsen number 0.1<KnL<10, using the MD results of aT. In the nanocavity, the adiabatic sidewalls do not significantly alter the gas mean free path and ⟨kf⟩, and the sparse adsorption coverage on the sidewalls results in a negligibly small fluid circulation by surface diffusion under a temperature gradient.