A transmission-line-matrix model for microwave heating problems

The use of microwaves to melt, dry sinter or join materials is gaining acceptance in many industrial applications, extending to the field of biomedical engineering. Such technology, however, is characterized by thermal runaway and the formation of localized areas of high temperature or hot spots that develop as the material is being irradiated. Hot spots can be utilized in smelting or joining since they enhance the process but avoided in sintering or drying since they can lead to damage. In any case, it is important to predict the conditions of their occurrence and how to control them. Microwave heating is a highly coupled nonlinear problem and the purpose of the paper is to show how the transmission-line-matrix (TLM) technique can be used to model this complex physical process. The numerical solutions are compared with some analytical and other numerical results. Our preliminary results show that the TLM method is well suited to microwave heat modelling and that the conditions under which hot spots develop can be predicted