A Numerical Study on Microwave Heating Effect of Paddy Based on Five Equivalent Dielectric Models

The paddy particle randomly filling in a glass container is simulated by using EDEM software (a particle simulation software based on discrete element method), and its volume fraction of two-phase medium (paddy & air) is calculated. Then, substituting the volume fraction into five equivalent dielectric models (Model, Li, CRI, Measure, LLL), we can obtain five equivalent dielectric constants of randomly stacked paddy particles. It allows us to instead the paddy particle by uniform dielectric in the modeling. A household microwave oven model is built in COMSOL Multiphysics software, and the paddy models with five dielectric constants are placed in it for microwave drying simulation. The drying process includes both static and rotary heating. The results show that: (i)The COV (Temperature coefficient of variation) of the Li equivalent model is worse while the CRI is better under static heating, and the center point temperature rise rates of the five equivalent models are in the order of: CRI, Measure, LLL, Model, Li. (ii)In the case of rotational heating, the COV decrease rates for the five equivalent models compared to static heating are 48.25% (CRI), 49.73% (Li), 49.49% (LLL), 49.20% (Measure), and 48.86% (Model), respectively, and the heating rate at the center of the equivalent model is lower than that of static heating.