Improving heating uniformity of microwave multimode cavities by using a moving metal wall

Microwave heating has been widely applied to both domestic usage and industrial production. Numerous microwave heating systems have been design and certain achievements have been obtained. However, there are still drawbacks limiting the large-scale industrial applications of microwave heating. The non-uniform temperature distribution caused by the inhomogeneous electromagnetic field distribution is one of the major barriers. Specifically, hot spots and thermal runaway are two of the most serious problems caused by microwave non-uniform heating. They will not only reduce the quality of microwave processed products, but also pose potential safety hazards. In this work, we propose a microwave multimode cavity with moving metal walls to improve the heating uniformity. By moving the metal wall of the cavity during heating, the distribution of electromagnetic field in the cavity will change constantly. Therefore, the position of a strong electric field at a certain moment is likely to shift largely at the very next moment. The variation of the electric field will be helpful to the improvement of heating. Moreover, by analyzing the hotspots and the time-dependent coefficient of variation (COV) of temperaure, we can optimize the moving mode of the metal wall to obtain better heating effect. The work will be helpful to optimize the heating status of the microwave cavities for processing materials.