A Moisture Transfer Model for Drying of Grain

K. Lund[1]
[1]Kurt Lund Consulting, Del Mar, California, USA

A kernel of grain is modeled as an isothermal sphere, with descriptive differential equations scaled or rendered into non-dimensional form, where moisture transfer is governed by internal diffusivity, not by surface conditions. The time dependent problem is solved with COMSOL and the average non-dimensional moisture content and its time-rate of change are obtained; by regression, these numerical data yield a new kernel-average moisture model that is extended to volumetric mass transfer for a bed or column of kernels. One-dimensional, time-dependent equations are derived for a "drying column" with axially flowing air, and with a stationary and flowing bed of kernels; these coupled equations are solved with the Diffusion and Convection tool in COMSOL.