Moisture profiles during intermittent soaking of an oblate spheroid

•Model of Fickian diffusion in an oblate spheroid during intermittent soaking.•Constant diffusivity and geometry were used.•Moisture profiles can be more uniform using a flood-drain process.•The free surface boundary condition only slightly affects the results.

Oblate spheroidal geometry and Fickian diffusion with constant diffusivity are used to model moisture absorption in a sorghum kernel with an aspect ratio of 1.48 during intermittent soaking. During the soaking phases the surface is assumed to be saturated while during the drain phases convective transport between the surroundings and the surface is assumed. An explicit finite difference scheme is used to solve the dimensionless form of the diffusion equation. For a three-cycle scenario with a 30-min soak, 2-h drain, 30-min soak, 5-h drain, and a 64-h soak, it is shown that the moisture distribution in the kernel is more uniform (as measured by the standard deviation of the moisture profile) than during a constant soaking scenario regardless of the assumed values of the Biot modulus and the equilibrium surface moisture concentration during the drain phases.