Microwave heating is an important process for many commercial, industrial, and household applications. Industrial microwave ovens are widely used for chemical processing, agri-food, medical products, and consumer products applications. Resonant cavities are often used to speed up chemical reactions, and have the advantages of being small and producing efficient distributions of microwave energy. These multimode cavities can be considered as batch ovens where products can be treated; alternatively, microwave tunnels with multiple waveguides can be used to provide continuous production.

Figure 1: Transverse Electric Field developed in waveguide.
In microwave heating applications, the energy is introduced directly into the volume of the material and, as a consequence, the quality of the process is highly dependent on the uniformity of the electromagnetic field distribution. Thus, developing a uniform electromagnetic field inside the cavities represents a crucial challenge to avoid localized overheating. Due to the difficulties associated with measuring electromagnetic fields, optimization of cavity design and selection of appropriate process conditions through experimental iteration is impossible.

To better understand the complexity of the problem and enhance the design of microwave processing technology, AltaSim Technologies analyzes microwave processing using COMSOL Multiphysics. In this approach, the Maxwell’s equations are reduced to a system of simultaneous algebraic equations that model an arbitrarily shaped geometry of heterogeneous and anisotropic materials. The depth to which microwaves penetrate material depends on their electrical properties. The interaction of the oscillating electric field of the microwave produces dielectric heating, thus giving rise to a heat source.

Figure 2: Magnetic and Electric Fields in microwave cavity with polarized source.
The electric field distribution represents the key factor that influences how materials heat in a microwave oven. Therefore, to optimize design and operational parameters, it is necessary to calculate how the electric field varies with factors such as cavity shape, microwave power, waveguide design, and waveguide location. Examples of how the electromagnetic field is generated in the waveguide are shown in Figure 1, and the resulting distribution of electric and magnetic field produced in the microwave cavity is shown in Figure 2.

This work was performed by S.P. Yushanov, L.T. Gritter, J.S. Crompton, and K.C. Koppenhoefer of AltaSim Technologies using COMSOL Multiphysics. For more information, contact: J. Crompton at This email address is being protected from spambots. You need JavaScript enabled to view it., or visit http://info.hotims.com/34458-131 .