Effect of the rotating metal patch on microwave heating uniformity

Microwave heating is well known for its efficiency and instantaneity. However, the non-uniformity results of the microwave heating have limited the development of its large-scale industrial application. In order to solve this problem, a metal patch placed on a rotating turntable is proposed as a mode stirrer in this paper. A commercial finite element software, COMSOL Multiphysics, is used to build the proposed model based on a BJ-22 rectangular waveguide and a microwave oven. Maxwell's equations, heat conduction equation, implicit function and level set methods, which are used to realize the rotation of metal patch, are coupled to describe the microwave heating process. The electric field intensity, the temperature, the coefficient of variation and the mean temperature rise in different cases are compared to optimize the parameters of mode stirrer. The point temperatures are measured by optical fibre to verify the simulated results. The results show that the rotation of metal patch has a huge influence on improving the heating uniformity and heating efficiency, but the rotating speed has little influence if the heating time is larger than a rotating period.