Computer Modeling and Numerical Simulation of Microwave Heating Systems
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• Design, characterization, and optimization of the various microwave processing systems. Several microwave processing systems—including single-mode and multimode cavities, traveling-wave applicators, and a wide variety of radiofrequency (RF) and induction heating systems— are presently available, and the selection of the most suitable one for a specific application presents one of the challenges. Furthermore, characterization and evaluation of the performance of a specific design are crucial in performing controlled and reproducible heating experiments. • Development of effective training and continued education in this highly interdisciplinary area. It is broadly accepted that visualization and animations based on computer simulation are important in providing effective training procedures. In spite of these significant advantages, examination of available literature reveals that reported activities in this area are rather limited.1"7 It may be noted that for accurate and, in particular, experimentally relevant computer simulation, not only are adequate computer model and simulation analysis capabilities required, but also knowledge of the thermophysical properties of materials (including dielectric properties) and their variation with temperature and frequency is needed. With the availability of high-performance computers and three-dimensional modeling software, however, required materials properties should be measured, and more efforts need to be focused on the simulation, design, and optimization of microwave and
RF processing systems. This article describes the role of numerical simulation in modeling the aspects of microwave heating of materials. Examples illustrate results from simulation of various heating systems, including single-mode and multimode cavities and traveling-wave applications. Research and development opportunities are suggested. Finite-Difference Time-Domain Method and Examples Several analytical and numerical solutions are available and can be used to model microwave processing systems.257 Our efforts at the University of Utah, however, focused on using the finitedifference time-domain (FDTD) method. An iterative solution of Maxwell's curl equations in both time and space, FDTD can be used to determine both the dynamic behavior of the heating process and also the steady-state values of the electromagnetic power deposition pattern in the sample and in the surrounding insulation. FDTD has also been shown to provide a suitable, accurate procedure for modeling inhomogeneous and electrically large objects of complex geometries.8 These features are certainly important in simulating realistic heating experiments and may help in investigating the possible scale-up of laboratory microwave processing systems. The following will describe examples of applying FDTD to the modeling of some microwave and RF heating systems.
Simulation of Microwave Sintering in Single-Mode Cavities In single-mode cavities, the electromagnetic field configuration is determined by the selected mode of operation and is t
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