Numerical modeling of heterogeneous moisture diffusion in milled rice grains: Diffusion coefficient as a function of moisture, temperature and time

The heterogeneous moisture diffusion of milled rice grains at 25, 35 and 45°C was simulated in 3D using the finite element method. The objectives of the study were to investigate the effects of temperature on moisture absorption and to predict the heterogeneous moisture diffusion in milled rice grains. Major routes and cracks channeled and facilitated rapid moisture movement in the grain. High temperature increased the rate of moisture movement. The moisture diffusion coefficient expressed as a function of moisture, temperature and time adequately described the heterogeneous moisture diffusion characteristics in milled rice. The integration of the logistic function of time reduced the root mean square error (RMSE) values between the experimental data and the numerical solution. Moreover, the RMSE values were much lower than the values modeled with moisture and temperature only. Modeling moisture transfer using the major routes of moisture revealed an increase in the modified frequency factor of the moisture diffusion coefficient.