Sublimation and deposition at a solid sphere in the presence of a non-condensable gas

Abstract

The sublimation/deposition process at a solid sphere of argon into its vapor in the presence of helium as a background gas is modeled applying the linearized Boltzmann equation, in which the McCormack model is employed for the collisional term. The Onsager coefficients determining the mass and energy flow rates at the interface are calculated over a wide range of rarefaction parameter and for some values of molar fraction of the background gas in the mixture. Moreover, two values for the temperature of the mixture are considered on the basis of the sublimation curves of argon and krypton. To assess the influence of the interatomic interaction potential on the numerical results, the calculations are carried out for both the hard-spheres and \textit{ab-initio} potentials. The kinetic coefficients are presented as well as the flow fields around the sphere. The effect of a small temperature difference between the spherical surface and the gas mixture is analyzed.