Mathematical Modeling of Green Pepper Drying in Microwave-convective Dryer

Authors
H. Darvishi 1
M. H. Khoshtaghaza 1
G. Najafi 1
F. Nargesi 2
1 Department of Agricultural Machinery Engineering, Faculty of Agriculture, Tarbiat Modares University, Tehran, Islamic Republic of Iran.
2 Department of Agricultural Machinery Engineering, Faculty of Agriculture, Ilam University, Islamic Republic of Iran.
Abstract
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 180, 360, 540, and 720W. The drying data were fitted to the four thin-layer drying models. The moisture reduction of the green pepper samples, from 2.894 to 0.1 kg water kg-1 dry matter, lasted 120 and 495 seconds at microwave power of 720 and 180W, respectively. The drying model assessment revealed that the Midilli model exhibited the best performance in fitting the experimental data, providing the highest R2 (0.927), and the lowest RMSE (0.2065) and χ2 (0.0555). With increase in microwave (drying) power from 180 to 720W, moisture diffusivity increased from 6.249×10-9 to 3.445×10-8 m2 s-1. 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 (7.2 MJ kg-1 water) was at microwave power of 360 W and the highest (9.26 MJ kg-1 water) was at 540W.

Keywords

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Journal of Agricultural Science and Technology
Volume 15, Issue 3
May and June 2013
Pages 457-465