Drying model for porous material based on the dynamics of the   evaporation front
  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. 
Reza Torabi, Mohammad Mehrafarin