Desenvolvimento de um modelo computacional para análise do aquecimento por micro-ondas em uma cavidade monomodo

Abstract

This thesis presents novel contributions for microwave heating simulations, inside a single mode rectangular cavity, via numerical solvers. Although, the thermalelectromagnetic problem is weakly coupled, in many situations, the loss factor of the load is strongly dependent on the temperature. Therefore, at each moment in time, onemust ensure that the electric field distribution corresponds to the correct permittivity. Also, to keep the system tuned the iris opening and the short must be allowed to vary during the heating. All these issues impose challenges on the numerical model in order to obtain efficient solvers.In this work, a hybrid method, which combines PDE solvers with analytical expressions, is used to determine the electromagnetic field inside the cavity. In the literature, the hybrid method was originally proposed with the FDTD in a two dimensional rectangular grid. In this research, the hybrid method was implemented with FEM using tetrahedral vector elements. It is shown that the FEM extends and improves the applicability of the method, for instance, allowing simulation of volumetric inhomogeneous loads. The main contribution of this research is a novel decision criterion, which provides the moment that the electric field must be recalculated. In most cases, the decision criteria found in the literature, are empirically based on the variation of the lossfactor. In this work, it is shown that they may introduce significant errors in the results and/or increase the simulation time. The proposed decision criterion is based on sensitivity analysis techniques. It is shown that it works well for different load conditions and can be easily implemented with the hybrid method.