In this paper, a numerical analysis of the coupled heat and mass transfer is proposed for a rectangular cell of form factor equal to 10. In particular, the heat and mass transfer are considered in the solid medium of the heated wall, in the liquid medium of the falling film and in the gaseous medium inside the cell. The solution of the transfer equations together with the appropriate boundary conditions allowed us to study in detail the evaporation and condensation mechanisms inside the cell. The study of the influence of the heated wall conductivity and of the heat distribution on the transfer phenomena allowed us to propose recommendations in order to improve the production of the cell.