A Three-dimensional Numerical Simulation of Transient Heat and Mass Transfer inside a Single Rice Kernel during the Drying Process

Abstract

A three-dimensional (3-D) theoretical model describing the coupled heat and mass transfer inside a single rice kernel during drying was established. The 3-D shape of a single kernel was characterised by the body-fitted coordinate system. The finite volume method was applied to solve the governing equations. A Fortran-90 based computer code was developed to simulate the transient moisture content distributions inside a rice kernel. The simulated average kernel moisture contents were compared favourably with the thin-layer drying data collected in this study. Moisture contents at some selected nodes and moisture content gradients inside the rice kernel were predicted under three different drying conditions. It was found that the moisture content gradient along the short axis of a rice kernel in the thickness direction almost doubled that along the short axis in the direction of width for the rice variety and drying conditions used in this study. The maximum moisture content gradient along the short axis in the direction of width was comparable to that predicted by a two-dimensional simulation reported in the literature.