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 Maxwell and energy equations is discussed. Simulations are performed illustrating the influence of working frequency, sample size and dielectric properties. The occurrence of resonant conditions, where constructive electromagnetic wave interference patterns produce high electric field intensities at discrete locations throughout the cavity, is shown to be the key ingredient for achieving high heating levels. The presence of coupled nonlinear processes is significant in materials which exhibit temperature dependent electromagnetic properties. This is illustrated in the processing of alumina, where local heating produces an exponential rise in temperature, once a critical temperature level is achieved.