Mass accommodation and uptake coefficients — a quantitative comparison

Abstract

An analytical formula, where the uptake coefficient is given as a function of mass accommodation coefficient, has been derived. The uptake coefficient is seen always to be smaller than or equal to the mass accommodation coefficient. The independence of the uptake coefficient on mass accommodation coefficient for small Knudsen number is demonstrated. If the boundary conditions, particularly the vapour pressure at the droplet surface, are not well defined, significant errors in the value of the mass accommodation coefficient can be expected. Values obtained in not well-defined conditions are typically smaller than the real value.