Distribution of pure vapor between two parallel plates under the influence of strong evaporation and condensation

The distribution of pure vapor between two plane parallel surfaces under the influence of strong evaporation and recondensation is treated by the nonlinear BGK kinetic equation. The boundary conditions allow for evaporation, condensation, and diffuse reflection. The corresponding system of integral equations is brought into a form that allows numerical treatment down to a Knudsen number of 0.1. For two special cases the flux rates as well as the density and temperature profiles are given. In the case of evaporation into an infinite half-space at the maximum attainable flow rate about 15% of the particles leaving the surface are backscattered.