Modeling Moisture Diffusivity and Activation Energy of High Moisture Black Gram in An in-bin Deep Bed Dryer

The drying characteristics of black gram during in-bin deep bed drying with high initial moisture content (20% w.b.) was studied at drying air temperature of 40, 50 and 60°C; at inlet air velocities of 1.5 and 3 ms⁻¹. The drying bed was divided into three thin layers: bottom, middle and top each of 0.2 m thickness. In order to find a suitable drying curve, seven thin layer-drying models were fitted to the experimental data of moisture ratio. Among the applied mathematical models, Midilli model was the best for prediction drying behavior of black gram. This model presented high values of correlation coefficient (R²). Fick´s second law was used to compute moisture diffusivity. Computed values of moisture diffusivity varied from 0.44to 0.64 ×10⁻⁹ at the bottom and top layers, respectively. The values of effective moisture diffusivity for black gram also increased as input air temperature was increased. Value of activation energy varied from a minimum of 93.76 to a maximum of 129.50 kJ mol^–1 with increasing temperature from 40 to 60°C. These properties of black gram would be necessary to determine the best point of drying process.