Resonance-Driven Microwave Heating of Low-Loss Cylindrical Substances in Waveguide Systems

As a clean and efficient energy, microwaves have been widely used in chemical engineering and ceramic sintering. However, the direct heating efficiency for materials with low dielectric loss is always inconspicuous. In this article, a direct heating model of multilayer low-loss dielectric cylindrical posts in rectangular waveguide is proposed based on the Mie theory. First, the electric field in multilayer dielectric cylindrical posts is derived in free space, and the model of parallel plate waveguide is given to show the electric field distribution in rectangular waveguide can be equivalent to the combination of two plane waves. Then, the condition for the maximum electric field is discussed, and the simulated electric field in single-layer and double-layer cylindrical posts in waveguide is compared with the derived electric field in single-layer and double-layer cylindrical posts in free space. The results show that the trend of the simulated maximum electric field with different radii of dielectric post in waveguide is basically in agreement with the derived maximum electric field. Furthermore, experiments are carried out to verify the proposed model, and the results show that the proposed model can initially determine the dimension of the dielectric cylindrical post to achieve high heating effect.