NUMERICAL MODELING OF MATERIALS PROCESSING IN MICROWAVE FURNACES

A detailed numerical model is presented for predicting electromagnetic fields in microwave waveguides and cavities, and the power deposition and temperature distribution in processed samples. Implementation of explicit finite difference schemes for solving the coupled unsteady Ma xwell and energy equations is discussed. Simulations are performed ill ustrating the influence of working frequency, sample size and dielectr ic properties. The occurrence of resonant conditions, where constructi ve electromagnetic wave interference patterns produce high electric fi eld intensities at discrete locations throughout the cavity, is shown to be the key ingredient for achieving high heating levels. The presen ce of coupled nonlinear processes is significant in materials which ex hibit temperature dependent electromagnetic properties. This is illust rated in the processing of alumina, where local heating produces an ex ponential rise in temperature, once a critical temperature level is ac hieved.