Numerical Simulation of a Vapor Flow with Evaporation and Condensation in the Presence of a Small Amount of a Noncondensable Gas

Abstract

A steady flow of a vapor evaporating from a plane condensed phase and condensing onto a corrugated condensed phase of sinusoidal shape is considered in the case where another gas that neither evaporates nor condenses (noncondensable gas) is contained in the gap between the condensed phases. The flow is investigated numerically on the basis of kinetic theory for small Knudsen numbers, with special interest in the continuum limit (i.e., the limit where the Knudsen number vanishes), in the case where the average concentration of the noncondensable gas is small, more specifically, it is of the order of the Knudsen number. The direct simulation Monte Carlo method is employed as the solution technique. The obtained flow properties, such as the stream lines, at small Knudsen numbers demonstrate a decisive difference from the corresponding flow properties in the pure‐vapor case where the noncondensable gas is absent, in spite of the fact that the average concentration of the noncondensable gas is as small as the Knudsen number. In the present parameter setting, the average concentration of the noncondensable gas vanishes in the continuum limit. The numerical result nevertheless indicates that the decisive difference is likely to remain even in this limit. This is consistent with the recent theoretical investigation by Aoki, Takata, and Taguchi.