Numerical simulation of the Rayleigh convection in nonsteady evaporation process

Numerical simulation of unsteady evaporation in closed system is conducted. The critical conditions of the transition from the diffusion mode to the convective mode are obtained. The flow pattern and the mass transfer properties are considered for all stages of the process. It is shown that the critical Rayleigh number based on the depth of the diffusion layer differs significantly from the threshold value found for the steady problem. Numerical solution is compared with the experimental data for the evaporation of water into argon.