DRYING OF SHRINKING BODIES

It is shown that if experimental drying runs are performed at different temperatures in order to obtain the activation energy of the diffusion process, false results are obtained when the experimental runs are conducted with different initial moisture contents. This fact provides an explanation for the considerable standard deviation in the calculation of the activation energies. The authors also show that the kinetic curves for absorption are different from those of desorption. This explains the different diffusion coefficients for absorption and desorption pointed out by King. Finally, at low moisture contents the solid can become a rigid instead of a shrinking body, and a change in the drying kinetics might be expected. This hypothesis, if experimentally verified, would provide an alternative explanation for the appearance of the second falling drying rate period.