|
چکیده
|
In this study, the effect of microwave power and shape of samples on moisture ratio, drying rate, effective moisture diffusivity, energy efficiency and energy consumption of potato were investigated. The drying experiments were carried out at 200, 300 and 400 W, and rectangular (S2) and cylindrical (S1) shapes with dimensions of 1×1×0.5 mm, 5×0.5 mm, respectively. Moisture loss values were compared with predicted values obtained from Page’s thin layer drying semi-empirical equation. The results showed that power and shape samples significantly influenced the total drying time, effective diffusivity, energy efficiency and energy requirement for drying. As the drying progressed, the loss of moisture in the product caused a decrease in the absorption of microwave power and resulted in a fall in the drying rate. The effective moisture diffusivity increased with decrease in moisture content of potato samples. A third order polynomial relationship existed between effective moisture diffusivity and the moisture content of potato samples. The average effective diffusivity varied from 2.33×10−8 to 7.60×10−8 m2/s for S2 and from 1.39×10−8 to 3.17×10−8 m2/s for S1 in the microwave power range from 200 to 400 W. The activation energy was calculated using an exponential expression based on Arrhenius equation and it was determined to be 31.50 and 16.44 W/g for S1 and S2, respectively. Energy efficiency increased with increase in microwave power and moisture content. The minimum specific energy requirement for drying of potatoes was determined as 4.24 and 5.70 MJ/kg water for S1 and S2, respectively, at power of 400 W.
|