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Modeling Cereal Grain Drying with Variable Diffusivity

¹Departamento de Industrias, Facultad de Ciencias Exactas y Naturales, Ciudad Universitaria, 1428 - Buenos Aires, Argentina. ²Departamento de Tecnología, Universidad Nacional de Luján, Cruce Rutas 5 y 7, C.C. 221, (6700) Luján, Provincia de Buenos Aires, Argentina.

The thin-layer drying or rough rice, maize and sorghum at several temperatures was investigated. Simulation of the experimental data was performed by solving numerically the diffusion equation with variable diffusion coefficient for spherical-shaped grain. To account for this variation, an analytical expression for the dependence of the diffusion coefficient with moisture content was obtained based on considerations of the energy needed to dissociate water molecules from their sites and of resistance to diffusion. When the expression for diffusivity was used for predicting drying behavior of the grains, a good agreement was obtained between experimental data and the theoretical prediction.