Modeling the heating uniformity contributed by a rotating turntable in microwave ovens

Microwave heating is caused by the ability of the materials to absorb microwave energy and convert it to heat. This article represents a review on fundamentals of microwave heating and their interaction with materials for various applications in a comprehensive manner. Experimental studies of single, multimode, and variable frequency microwave processing were reviewed along with their applications. Modeling of microwave heating based on Lambert's law and Maxwell's electromagnetic field equations have also been reviewed along with their applications. Modeling approaches were used to predict the effect of resonances on microwave power absorption, the role of supports for microwave heating, and to determine the nonuniformity on heating rates. Various industrial applications on thermal processing have been reviewed. There is tremendous scope for theoretical and experimental studies on the athermal effects of microwaves. Some of the unresolved problems are identified and directions for further research are also suggested. © 2011 American Institute of Chemical Engineers AIChE J, 2012

Microwave material processing—a review

Microwave drying is an advanced drying technique in which heat is generated inside the material due to transformation of high-frequency electromagnetic energy so the liquid moisture is intensively evaporated and transported toward the material surface However, an inherent problem in microwave drying is nonuniform heat generation, which leads to uneven drying In this article, the factors causing nonuniform microwave heating were identified, and feasible approaches to solving the nonuniformity problem were analyzed in terms of improving the uniformity of the electromagnetic field distribution and random or organized dislocation of the processed material in virtually nonuniform microwave field The R&D trends in microwave drying toward reducing uneven heating were pointed out and discussed

Uniformity Issue in Microwave Drying

https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1135&context=foodsciefacpub

Coupled electromagnetic and heat transfer model for microwave heating in domestic ovens

A fully coupled electromagnetic, heat transfer and multiphase porous media model for microwave heating of coal

Non-uniformity of temperatures in thawing of food and biological materials inside a microwave oven is affected by size, shape, and dielectric properties of the load (food) The objective of this study was to relate the time to thaw and the non-uniformity of heating to the shape, size, and the dielectric properties of the load The details of the heat transfer analysis, experimental measurement of thermal and dielectric properties, and temperature measurements are described in a companion paper Results show that both the aspect ratio and the volume have a significant effect on the heating rates, time to thaw and the non-uniformity of temperatures during thawing A "shield" develops from surface thawing and leads to reduced microwave penetration This "shield" develops more readily at higher dielectric loss, thereby effectively increasing the thawing time even more for a lossy material at higher power levels Thawing time increases linearly with volume As the load aspect ratio decreases (it is made flatter), it thaws faster since the energy decays relatively less in a thinner material These new results could provide a more rational and quantitative approach to development of frozen food products to be heated in a microwave oven

M Chamchong

Papers

Thawing of foods in a microwave oven: II. Effect of load geometry and dielectric properties.