Surrounding Dielectrics for Reducing Heating Concentrations of Spheres in Microwave Applicators With Moving Elements

Heating concentrations widely exist in microwave heating, which may destroy heated samples. In this article, we report that with spheres being surrounded in dielectrics, the heating concentration of spheres can be reduced in microwave applicators with moving elements. First, electric field properties in electrically large cavities with moving elements are analyzed by the statistical approach. It reveals that the heating concentration can be studied under exposure to plane waves. Second, based on the Mie theory and the quasi-physical optics, the method for controlling the concentration locations of spheres is discussed. Then, the theoretical model utilizing dielectrics is presented to reduce the concentration of spheres in microwave applicators with moving elements. The results show that when the concentration location is far from the sphere center, the concentration can be reduced in the motion of moving elements. Finally, the heating process of a potato sphere with a radius of 3.0 cm is studied in a practical microwave applicator with the alumina ceramics (AC). Experiments show that both the heating efficiency and heating uniformity can be improved significantly by the proposed method.