Model-Based Estimate for Time-Dependent Apparent Diffusivity

This article presents a method allowing the effective diffusion coefficient to be determined from experimental drying kinetics as a time-dependent parameter. The method combines an analytical solution of Fick's equation in which the Fourier number is raised to the empirical power (a), with a semi-theoretical equation derived for quasi-stationary conditions. The method has been validated by applying the resulting equation to literature data on drying kinetics for parboiled rice and cut tobacco leaves as they approach a sphere and a slab, considered to be standard geometries in diffusion problems.