Author
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Nelson, Stuart |
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Submitted to: World Congress on Microwave and Radio Frequency Processing
Publication Type: Book / Chapter Publication Acceptance Date: 11/11/2004 Publication Date: 11/1/2005 Citation: Nelson, S.O. 2005. Useful relationships between dielectric properties and bulk density of granular and powdered materials. Proceedings of the 4th World Congress on Microwave and Radio Frequency Applications. R. L. Schultz and D. C. Folz, Editors. Arnold, MD: The Microwave Working Group, Ltd., pp. 407-416. Interpretive Summary: Technical Abstract: The dielectric properties of cereal grains and oilseeds are used in the determination of moisture content by electrical and electronic moisture meters. The dielectric properties of materials are those electrical characteristics that determine the interaction of the material and electric fields in microwave or dielectric heating and that can be used to sense moisture content instantaneously in properly designed moisture meters. However, the packing, or bulk density, of such granular materials interferes with accurate moisture measurement if differences in packing are not taken into account. This paper provides a discussion of the influence of bulk density on the dielectric properties of granular and powdered materials. It also summarizes results of research to define the relationships between the dielectric properties and the bulk density of such materials as wheat, wheat flour, and pulverized coal, limestone, and some plastics. A recommended equation for correcting the dielectric properties for changes in the bulk density of such materials is presented. This information will be useful to those designing microwave and dielectric heating equipment. It will also be useful to those developing moisture meters for grain and seed and other granular or pulverized materials to provide more reliable moisture information for the management of grain and seed harvesting, storage, marketing and processing operations. Consequently, maintenance of better quality in agricultural grain and oilseed crops will benefit both producers and consumers. |
