Microwave heating of foodstuffs

The temperature distribution in a product submitted to microwave radiation is governed by the interaction and absorption of radiation by the medium and the accompanying transport processes due to the dissipation of electromagnetic energy into heat. Thus, modeling of microwave heating involves coupling the models for microwave power absorption and temperature distribution inside the product. In this study, a model was presented, for which the absorbed microwave power was obtained by solving Maxwell's equations and then incorporated as a source term in the transient heat equation. The finite element method was used for discretization of the governing equations. The proposed methodology was then applied to simulate microwave heating of foodstuffs. A comparison of the power distribution obtained by solving Maxwell's equation to that by using Lambert's indicated the sample size above which the Lambert's law limit is valid is higher for cylinders compared to slabs. The simulation results showed that microwave heating is significantly dependent on sample size and shape. It was also observed that heating is quite dependent on radiation frequency, and that power absorption and radiation penetration are more effective at lower frequencies than at higher ones. An on/ off operating system was simulated and coupled with sample rotation, resulting in more uniform temperature profiles compared to each technique applied separately. Simulation runs were also performed for different materials, resulting in quite different power distributions. (C) 2002 Elsevier Science Ltd. All rights reserved.