Drying of Porous Material During the Constant and the Falling Rate Period: A Critical Review of Existing Hypotheses

During drying of porous material a so-called “falling rate” period is observed, where the drying rate decreases as the moisture content decreases. This behavior is usually described by the well known “shrinking core model.” This model, however, contradicts experimental findings and violates basic laws of multiphase mass transfer in porous media as well. A new model, named “wet surface model,” is suggested which eliminates those discrepancies.