A receding evaporative front model for the drying characteristics of a flat plate I: theory

Abstract

A theoretical background study is presented for the pressure and moisture distributions, stress and strain produced during the drying process of an elastic flat plate with a receding evaporative front. A three-stage drying process is proposed. In the first stage (saturated stage), the body is fully saturated and pressure-driven flow prevails. During the second stage (partially saturated stage), the evaporative front recedes through the material and divides the material into saturated and unsaturated zones. During the third stage (fully unsaturated stage), the body is entirely unsaturated and moisture is lost by diffusion only. An exact model for the falling-rate period of drying of solids, during which a body may be partially saturated or fully unsaturated, is also presented based on Sherwood\'s diffusion theory. The exact model is compared with Sherwood\'s approximate models for the falling-rate period, and with experimental data. The agreement between the exact model and the experimental data is shown to be better than that between the experimental data and Sherwood\'s models for the given drying rate.

Keywords: drying, flat plate, solid; receding, evaporative front

Global Journal of Engineering Research Vol.4 (1&2) 2005: 31-38