Numerical analysis of microwave heating applied to solids and particles

The finite element method has been applied to study problems associated with the microwave heating of both solids and particles. Developing an accurate model for microwave heating is a multifaceted challenge. In industrial applications, the material is frequently composite mixtures. Incorporating these materials into the wave equation requires an estimate of the composite complex dielectric, specifically the loss tangent which determines power absorption. The utility of using the finite element mesh to approximate these particles is evaluated.; The microwave heating process represents a nonlinear system. The absorption rate and field distribution in the material are functions of the evolving electric and thermal properties. By selecting time steps during which little change in the electric field distribution occurs, it is possible to determine steady state frequency domain solutions to the wave equation. The inhomogeneous differential equation for heat diffusion can then be modelled in the time domain. A time stepping algorithm modelling these two equations with appropriate stepsize is applied to the microwave heating of a large dielectric cylinder with temperature dependent complex permittivity.; More efficient heating processes utilize cavities to manipulate field distributions. These cavities will resonate at select frequencies, equivalent to the eigenvalue solutions of the wave equation with appropriate boundary conditions. Loading the cavity will shift these resonant frequencies. The finite element method was applied to investigate the resonant frequencies and field distributions in both a loaded and an unloaded rectangular chamber.; An iterative solution for multiple domain problems was also developed. The method applies superposition in each domain, adding successive local near field solutions that are determined from the scattered field of external geometries. By discretizing regions local to each object, the total number of calculations is reduced significantly, saving memory and computational time. Additionally, local errors can be minimized by constructing domain boundaries that reduce reflections from the absorbing boundary condition approximation.; A configurable plasma antenna has been designed for selective operation of both frequency and beam direction. The antenna can also be made invisible to avoid unwanted detection or interference. The FEM method was applied to analyze the behavior of a circular plasma array comparable to an cavity backed aperture antenna.