MODELING OF ROUGH RICE DRYING IN THIN VERTICAL COLUMNS

The solution of classical diffusion equation based on the assumption o f average moisture diffusion coefficient did not adequately represent natural convection drying of rough rice in thin vertical columns expos ed on both sides to hot air. Instantaneous moisture diffusivity coeffi cients determined from experimental drying curves decreased continuous ly with an increase in exposure duration and were linearly related to moisture ratio. The proportionality constant which was called apparent moisture diffusion coefficient was distinctly related to air temperat ure, relative humidity, and initial moisture content of rough rice. Th e modified moisture diffusion model using the instantaneous moisture d iffusion coefficient was found to best represent the moisture removal from bulk rough rice.