Simultaneous liquid and vapour transport in partially saturated porous materials is modelled with two coupled diffusion equations in which a term accounts for the evaporation. The solution of the differential equation for the vapour diffusion is approximated with the quasi steady solution. The differential equation for the liquid diffusion is solved using the numerical Crank-Nicolson method. The predictions of the model are compared with experimental data of drying clay as found in the litera
ture. The influence of sorption isotherms must be included in the model