MODELLING A MICROWAVE/CONVECTION DRYER FOR DRYING OF POTATO SLICES

Abstract

The aim of the present study is modeling a developed microwave/convection dryer using similitude analysis for drying a thin layer of potato slices (Solanum Tuberosum), which can be helpful in design and operation criterion of this developed thin layer dryer type for drying other agricultural products. Drying time as affected by microwave power and drying air temperature, effective diffusivity Deff, compatibility of experimental data to Lewis Newton's thin layer drying model and rehydration and color as quality indicators were also studied. Four different levels of microwave power, namely: 85, 175, 250 and 320W, three different drying air temperatures of drying air are 40, 50 and 60oC with air velocity of 1.5 m/s were studied. The results show that the drying time was decreased by increasing microwave power and air temperature. The effective moisture diffusivity Deff increased with decreasing moisture content, maximum values of Deff were recorded at highest microwave power of 320 W. Lewis Newton's thin layer drying model was highly compatible to experimental data with R2 ranging between 0.754 to 1.00. The rehydration ratios ranged between 2.19 to 3.41 under various drying conditions. There is no significant change in color of the dried potato compared to fresh potato slices