Numerical simulation and optimization of microwave drying process of wheat bran

Abstract

The unclear aspects of the continuous microwave drying process for wheat bran were addressed, aiming to improve uniformity and enhance the efficiency of microwave energy absorption during the drying process. A mathematical model for the dielectric properties, temperature, and moisture content of wheat bran was established. Subsequently, a multi-physics coupling model integrating the electromagnetic field, heat transfer, and mass transfer was developed. A moving simulation strategy was implemented to achieve continuous microwave drying. This study identified the waveguide arrangement, layer thickness, and conveyor belt height as key factors influencing drying uniformity. Through single-factor and orthogonal experiments, the optimal parameters for the drying equipment were determined, yielding a waveguide arrangement (b), material thickness of 20 mm, and conveyor height of 135 mm. The electric field uniformity coefficient was 0.25, and the microwave energy absorption efficiency reached 87.4 %. The bench experiment results showed that, under the optimal conditions, the temperature and moisture content trends aligned well with simulations. The root mean square errors were 3.44°C for temperature and 1.75 % for moisture content, affirming the model’s accuracy and reliability. This study provides valuable insights for analyzing microwave drying processes and supports the development of effective drying equipment.