Tolaba, Aguerre, and Sua´rez (1997) performed drying of
cereal grain and solved diffusion equation with variable diffusivity.
In that study the thin layer drying of rough rice,
maize and sorghum at several temperatures was investigated.
They numerically solved diffusion equation for
spherical shape of grain. 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.