A diffusion model with a moisture dependent diffusion coefficient for parboiled rice

A mathematical model describing moisture migration by diffusion in a solid sphere with variable diffusion coefficient is proposed. An analytical expre ssion for dependence of the diffusion coefficient with moisture content was derived based on the assumption that the activation energy for diffusion v aries linearly with the desorption energy. The expression for moisture dependence of diffusion coefficient was used to simulate drying of parboiled rice in the temperature range 50-90 degreesC. The mathematical model shows good agreement between observed and predicted drying rate curves.