Characterising the Drying Behaviour of Microwave Assisted Drying of Coconut Chips

Drying is the most critical unit operation in coconut oil and desiccated coconut industry. Different technologies are used for drying coconut chips and hot air drying is the most popular method. Microwave (MW) drying has gained attention in many process industries due to its faceted benefits. This study examines the critical parameters governing the microwave drying of coconut chips. Sliced coconut chips of $1 \text{cm}\times 1\text{cm}\times 1\text{cm}$ were used. The effect of the two independent variables MW Power (100 W, 180 W, 300 W) and Mass Loading rate (20 g, 40 g, 60 g, 80 g, 100 g) on three response variables, moisture content, drying time and drying rate was examined. Air velocity of 0.6 m/s was circulated in the drying chamber to ensure convective mass transfer. The ratio of Microwave Power to the Mass Loading was found to define two distinct regions for selecting the mass loading for a given microwave power. At high MW power to mass loadings, the total drying time was found to be constant against the mass loading while at low MW power to mass loadings, the total drying time was found to increase with the mass loading for a given MW power. Considering both statistical conformity ($R^{2} > 0.995$, SSE and RMSE close to zero) and the simplicity together, Page model was identified as the best thin layer drying model for describing the Microwave Assisted Air Drying of coconut chips.