A double diffusive natural convection in an enclosure filled with a porous medium is investigated numerically. To enhance the heat transfer rate of a heat wall, the heat wall is wetted with a thin water film, then sensible and latent heat transfer occur simultaneously. The Darcy‐Brinkman‐Forchheimer model is used and the factors of heat flux, porosity and diameter of bead are taken into consideration. The SIMPLEC method with iterative processes is adopted to solve the governing equations. The results show that the effect of evaporation on the heat transfer rate is apparent, and the latent heat transfer plays an important role in the high Darcy‐Rayleigh number situations. The averaged Nusselt numberNuis approximately 2.5 whenRa*<4. In the range of 4<Ra*<4469, the relationship of the averaged Nusselt number with the Darcy‐Rayleigh number is linear in logarithmic scale.