Gas flow towards an adsorbing planar wall subject to partial gas-surface thermal accommodation

The steady half-space single gas flow driven by an adsorbing planar wall is investigated based on the solution of the BGK kinetic model. The mass and heat transfer between the gas and the plate are characterized by the sticking and thermal accommodation coefficients, the surface temperature and the far upstream velocity and temperature. The work is focused on the influence of partial thermal gas-surface interaction on all flow quantities including the sticking coefficient. It has been found that as the gas thermal accommodation on the surface is reduced, for prescribed adsorbing flux and temperature difference, the sticking coefficient must be increased to sustain the prescribed flux or otherwise for the same sticking coefficient the adsorbing flux is reduced. This behavior is enhanced as the difference, between the surface and the far upstream temperatures, is increased. Overall, the effect of the thermal accommodation coefficient is significant in all flow quantities and must be accordingly taken into consideration. The present theoretical/computational investigation of partial thermal accommodation effect may provide a more clear interpretation of measurements of sticking coefficients, and conversely, improve performance calculations for cryopumps.