3D simulation of momentum, heat and mass transfer in potato cubes during intermittent microwave-convective hot air drying

Simultaneous use of convective hot air and continuous microwave is a new method for drying of agricultural products. This study indicated the effect of different drying methods (Convective Hot Air 45 °C at a speed of 1 m/s (CHA), Microwave 540 W (MIC), simultaneous Convective Hot Air and continuous Microwave (HA-MIC)) on the drying kinetics of potato cubes (moisture ratio, effective moisture diffusion coefficient and energy consumption). In addition, modeling of momentum, heat and mass transfer, along with changes in chemical composition and thermophysical properties of potato (at the same time with temperature change and moisture exit) during HA-MIC drying method was performed. Considering to results, the lowest energy consumption was related to the MIC method. The results of the modeling section showed that, by reducing the mass and volume fraction of water, the ratio of other components (carbohydrates, proteins, fats, ash, and fibre) increases in the total solid. In addition, with decreasing the mass fraction of water along with increasing temperature, total density (kg/m3) and the density of potato constituents increased and decreased, respectively. Total specific heat (J/kg.K) and total heat conductivity (W/m.K) of potato also decreased with decreasing the mass and volume fraction of water; while in specific heat and thermal conductivity of potato constituents, an increasing trend was observed. Finally, a high correlation was obtained between the results of experimental data and numerical modeling for moisture distribution (R2 = 0.9589) and temperature distribution (R2 = 0.9961).