  A receding-front model for drying of porous material is proposed that
explains their drying-rate curves based on the dynamics of the evaporation
front. The falling-rate regime is attributed to the slowing down of the front's
propagation inside the medium due to the resistance offered by the disorder
generated by porosity. The model is solved numerically and the resulting
drying-rate curve is obtained for the falling-rate period. The curve shows a
linear behavior at early times in conformance with experiment.
