A coupled mathematical model for simultaneous microwave and convective drying of wheat seeds

Faster drying techniques are preferred to prevent spoilage of harvested wheat seeds. Microwave (MW) drying may be used as an alternate technique for faster drying of crops with efficient utilisation of time and energy. The objective of this study was to develop a mathematical model to simulate the drying condition of wheat seeds during drying in a MW oven. A coupled mathematical model was developed for simultaneous MW and convective drying of wheat seeds in a domestic MW oven, resulting in a system of non-linear equations. Wheat samples with initial moisture levels of 15–25% wet basis were dried under MW power ranging from 245 to 910 W for 3 min. The temperature and the relative humidity of drying air was 23 °C and 27%, respectively. The results revealed that the rate of drying increased with increase in the initial moisture content of wheat seeds. The germination percentage of wheat seeds decreased with the increase of the MW power at each initial moisture content. The predicted temperature of grain during drying with the MW power at 910 W was within the range of 65–70 °C. The experimental results of moisture content of wheat seeds undergoing MW drying were in good agreement with the moisture content of wheat seeds predicted by the coupled mathematical model.

► A coupled model of drying was developed using microwave and convective drying models. ► US soft red winter wheat was dried in a microwave oven with continuous monitoring of weight. ► 3 microwave power levels and 3 initial moisture contents of wheat seeds were used. ► The coupled model described the drying characteristics very well with R2 > 0.90.