A Study of Some Inherent Causes for Non-Uniform Microwave Heating
Journal
IEEE International Conference on Plasma Science
Journal Volume
2018-June
ISBN
9781538645895
Date Issued
2018-06-24
Author(s)
Abstract
Radio frequency (RF) and microwave heating of dielectric objects is often susceptible to an excessive temperature spread due to uneven energy deposition. The exposure to a nonuniform field is a well-studied cause for this difficulty encountered in numerous applications. There are, however, some less-understood causes, which are inherent in nature in that they persist even in a perfectly uniform field. We present an experimental study on three main inherent causes with rice grains as samples. Of these cause, somewhat less obvious is the polarization charge shielding effect1 2. Exposed to the wave electric field, electrical charges in the dielectric object react in a way to partially shield the wave electric field. As a result, the dielectric object's interior electric field can be significantly smaller than the incident electric field, resulting in a much reduced power deposition. Experiments are conducted in an applicator, in which samples are irradiated by a 24 GHz microwave. High radiation uniformity (99%) and polarization control allow a quantitative examination of each cause. Their individual and collective effects are found to be highly significant. In particular, polarization-charge shielding alone can result in a temperature spread of 18.2% for the samples examined. Physical interpretations are given and an effective method for its mitigation is demonstrated.
Type
conference paper