2. Models and drying steps

"Usually", whatever the type of drying and the nature of the products, the authors agree in comparing the experimental results obtained in the evolution of moisture content as a function of time, to an "ideal" situation with several drying periods.

In the case of hygroscopic porous media, we can often speak of three drying phases:

• step 1: drying control through the surface water removal process ;

• step 2: control of drying by water diffusion within the hygroscopic porous medium;

• stage 3: considered "paradoxical", involves "progressive front" kinetics.