Heat and mass transfer for liquid film evaporation along a vertical plate covered with a thin porous layer

The purpose of this work is to evaluate the heat and mass enhancement of liquid film evaporation by covering a porous layer on the plate. Liquid and gas streams are approached by two coupled laminar boundary layers incorporated with non-Darcian modes. The numerical solution is obtained by utilizing a fully implicit finite difference method and examined in detail for the effects of porosity ε, porous layer thickness δ, ambient relative humidity ϕ and Lewis number Le on the average heat and mass transfer performance. It is shown that the heat and mass transfer performance may be enhanced by the presence of a porous layer. Both the average Nusselt and Sherwood numbers are increased with the decrease of ε, δ and ϕ. In addition, the influence of ε on the heat and mass transfer is significantly increased as δ is increased.