Transferability of Moisture in Plastic Mass during Drying Process

Abstract

Effects of temperature gradient and particle orientation on moisture transfer coefficients in the earthenware and the kaolinite plastic mass during drying process have been investigated by determining moisture distribution curves under a condition of one dimensional water transfer.
The results are summarized as follows:
(1) During the constant-rate period, the temperature gradient scarcely affects the moisture transfer coefficient, whereas, in the falling rate period, the moisture transfer coefficient increases steeply up to four-fold in comparison with that under no temperature gradient when the interior temperature of specimen is higher than the temperature of drying surface. On the other hand, it decreases to one-half under the inverse temperature gradient.
(2) The moisture transfer coefficients in the direction parallel to the particle orientation for the constant- and for the falling-rate period are several and nearly one hundred-fold larger than those in the direction perpendicular to the particle orientation, respectively. The results could be ascribed to a larger tortuosity in the path of moisture movement and to a smaller number of capillary per unit area in the perpendicular than in the parallel direction to particle orientation.