Finite Elements in the Simulation of Dielectric Heating Systems

Probing multimode applicator of microwave heating system for E‐field distribution using a silicon carbide sensor and a shielded thermocouple

“…A figure of merit of uniformity or smoothness S of the field in that particular volume (or over the area) can be estimated by using elemental polygons (or grid) to fill the volume (area), say g polygons, and taking the Q MW measured at a chosen point, say the center of the polygon, to be same everywhere in the polygon volume, $$\begin{equation} {P}_{\textit{avg}}=\left(\sum _{i=1}^{i=\beta}{Q}_{\textit{MW}}{\left(\mathrm{x},\mathrm{y},\mathrm{z}\right)}_{\textit{cent}\textit{re}-i}\right)\ensuremath{\times{}}\frac{1}{\beta} \end{equation}$$ The figure of merit of uniformity S in the volume (made up of β polygons) may be obtained using $$\begin{equation} S=\left(\sum _{i=1}^{i=\beta}|{\mathrm{P}}_{\mathrm{i}}-{\mathrm{P}}_{\mathrm{avg}}|\right)\ensuremath{\times{}}\frac{1}{\beta}\ensuremath{\times{}}\frac{1}{{P}_{\textit{avg}}} \end{equation}$$where P i = Q MW (x,y,z) Centre i is the absorbed microwave power at (x, y, z) Centre i, i.e., the one measured at the center of the i th polygon. This is on the lines of using mode stirrer simulation results for checking the field uniformity 53 over a certain surface area in the applicator.…”

“…It is suggested here that monitoring of the local average field distributions E 0 (x, y, z) │ P or position-wise distribution of the absorbed microwave power Q MW (x, y, z) │ P such as presented in Figures 4C,D and 5A,B could be useful in the area of microwave applicator design. The current general framework for understanding the working of the applicator part of a microwave heating system (whether of the single-mode-type or the multimode-type) and its design optimization is based on modeling with analytical or numerical calculations [43][44][45][46][47][48][49][50] or multi-physicsbased simulations 25,[51][52][53] or using certain experimental techniques. [54][55][56][57][58] The applicator optimization is in terms of the best coupling of the magnetron output power to the applicator cavity via a short waveguide (and an isolator coupler) or for a given dielectric 'load', or the applicator dimensions being such that the reflection coefficient of the applicator is minimum at the input frequency 56,60 , or in terms of development of strategies for uniform heating of the 'load'.…”

“…where P i = Q MW (x,y,z) Centre i is the absorbed microwave power at (x, y, z) Centre i, i.e., the one measured at the center of the i th polygon. This is on the lines of using mode stirrer simulation results for checking the field uniformity 53 over a certain surface area in the applicator.…”