Effect Of Electrically Conductive Beads On The Electromagnetic Field Distribution In A Microwave Cavity

Microwave drying is different from the traditional drying method, and its volume heating characteristic favors fast-drying, especially during the final drying period when conventional drying takes too long time to reach the final moisture content. Therefore, mi-crowave drying is widely applied in food industry. However, non-uniformity of microwave drying is a major bottleneck in currently microwave drying practice because it leads to the low product quality.In microwave heating process, the temperature profiles inside the material are very complex, depending on the electromagnetic field intensity in the material and the material’s dielectric properties. Because the field intensity distribution is usually uneven in the mi-crowave cavity, which is also affected by the material physical properties, the field intensity distribution in the material is uneven in general. In microwave heating process, absorption of microwave power and microwave penetration depth are dependent on the parameters such as electromagnetic field, material dielectric properties, material temperature and moisture content, which are coupled and cross affected, and thus non-uniformity of micro-wave heating is an intrinsic problem.To solve microwave uneven drying, the objective of this study is to improve the un-iformity of microwave drying by changing the electric field distribution. The proposed me-thod is that electrically conductive beads are placed in the microwave cavity. The electro-magnetic field distribution is improved by the random microwave reflection from electri-cally conductive beads.This study is based on the finite element method. Numerically investigated the effect of the position, size, and numbers of electrically conductive beads put in the cavity on the electric field distribution by using COMSOL-Multiphysics software, and verified the ratio-nality of the model through experiment. It was concluded that the appropriate placement of the electrically conductive beads greatly improved the uniformity of the electric field dis-tribution in the microwave cavity. According to this conclusion, further study the effect of the movement of electrically conductive beads on electromagnetic field distribution in the microwave cavity. The results showed that with the random motion of the electrically con-ductive beads in the microwave cavity, the uniformity of the electromagnetic field distribu-tion has been a significant improved.