Mathematical Modeling of Green Pepper Drying in Microwave-convective Dryer

In this study, green pepper was dried by a laboratory scale microwave-convective dryer. The effects of microwave power on drying rate, effective moisture diffusivity, and energy consumption of green pepper were studied at four different microwave powers of ۱۸۰, ۳۶۰, ۵۴۰, and ۷۲۰W. The drying data were fitted to the four thin-layer drying models. The moisture reduction of the green pepper samples, from ۲.۸۹۴ to ۰.۱ kg water kg-۱ dry matter, lasted ۱۲۰ and ۴۹۵ seconds at microwave power of ۷۲۰ and ۱۸۰W, respectively. The drying model assessment revealed that the Midilli model exhibited the best performance in fitting the experimental data, providing the highest R۲ (۰.۹۲۷), and the lowest RMSE (۰.۲۰۶۵) and χ۲ (۰.۰۵۵۵). With increase in microwave (drying) power from ۱۸۰ to ۷۲۰W, moisture diffusivity increased from ۶.۲۴۹×۱۰-۹ to ۳.۴۴۵×۱۰-۸ m۲ s-۱. Results also indicated that drying rate increased by increasing the microwave power and decreased continuously with passing of drying time and decreasing moisture content. The least specific energy consumption (۷.۲ MJ kg-۱ water) was at microwave power of ۳۶۰ W and the highest (۹.۲۶ MJ kg-۱ water) was at ۵۴۰W.