Coupled Electromagnetic–Thermal Modeling of Rice Bran Heating in Microwave Oven

ABSTRACT This study focused on the microwave heating of rice bran to enhance its stabilization and improve oil recovery. The main objective was to develop a three‐dimensional numerical simulation model for microwave heating of rice bran on a rotating turntable in a domestic microwave oven. Additionally, the dielectric properties of rice bran were determined based on varying moisture content (10%–30%) and compressibility ratio (1–1.4). The model was constructed using the radio frequency and heat transfer module in the COMSOL Multiphysics 4.4 software, which employs finite element analysis. A novel approach of simulating microwave heating with rotation without using MATLAB was attempted by dividing the rotating domain into smaller subdomains. This approach showed good agreement with the experimental values. The simulated and experimental absorbed power density and temperature of the bran during microwave heating were evaluated and compared using different power levels (150, 225, 375, and 450 W) at a fixed frequency of 2450 MHz. The results showed good agreement between the simulated and experimental values, as indicated by the low root mean square error (RMSE) values for absorbed power density (0.16–1.28 W/g) and temperature (4°C–8°C). Furthermore, the study investigated the effect of the on–off duty cycle at maximum microwave power on bran heating. It was found that the temperature profiles obtained were similar to those obtained at equivalent power levels. The developed model could be utilized to analyze the impact of sample size, position, and dielectric properties of bran on heating uniformity in a domestic microwave oven.