New coupling model of microwave assisted hot-air drying of a capillary porous agricultural product: Application on soybeans and canola seeds

Abstract The distributed parameter model was coupled to the microwave model to study the drying process of two oilseeds (canola seeds and soybeans) under a process involving a combined microwave-assisted hot-air dryer. The various drying conditions of low microwave densities in the range of 0.25–0.3 W g −1 and at three air temperatures of 35, 50 and 65 °C were employed. The coupled partial differential equations governing the mass and heat transfer were solved using finite differences method. The predicted results were tested with the experimental data and good agreement was found proving the validity of the coupling model. It was observed from the predicted results that the drying rate of soybeans varied from 2.18 × 10 −5 to 5.039 × 10 −5 (kg [water] kg −1 [grain w.b.] s −1 ) when drying by hot-air in the range of 35–65 °C. For canola seeds, the drying rate varied between 5.12 × 10 −5 and 1.34 × 10 −4 (kg [water] kg −1  [grain w.b.] s −1 ), under the same drying conditions. It was also observed that there was no effect of the exposure time on the germination rate of canola and soybeans treated under low microwave density.