A Modular Approach to Microwave Applicator Design
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A MODULAR APPROACH TO MICROWAVE APPLICATOR DESIGN JOS8 T. SENISE, SP., Brazil.
Instituto Maui de Tecnologia,
S.
Caetano do Sul,
ABSTRACT Whenever possible, the modular approach to microwave applicator design presents several advantages, both economical and operational, particularly in countries where high-power microwave generators are not manufactured on a commercial scale. In this paper, examples are shown of industrial applicators of simple, modular design, for the processing of liquid and solid materials, coupled to generators built with domestic microwave oven components. INTRODUCTION The objective of modular design is to subdivide applicators in parts, while obtaining the same end result of a larger, single unit. Each part or modulus should include its own generator(s) and should operate, as much as possible, as an independent unit, although connected to other identical moduli, in order to obtain the total heating effect required by the process. Some of the advantages of a modular design include: 1 - Ease of scaling up results obtained on a small, laboratory scale. 2 - Use of low-power, low-cost generators, unprotected by costly circulators. 3 - Better production continuity resulting from easier maintenance and substitution of generators. These and other possible advantages are not considered when budgets, particularly for experimenting, are generous. This desirable condition is not found in most academic laboratories and small industries, where experimenting with high-power generators and large applicators is not feasible. This is particularly true in countries where high-power generators are not easily available. APPLICATORS FOR BATCH AND CONTINUOUS PROCESSING Microwave processing of materials can occur in batch and continuous operations. For most batch processes, the multimode cavity is a convenient applicator, particularly when only one or a few generators need to be connected to the cavity. Multimode cavities also can be - and are - used for continuous processes, but in many cases continuous processes can utilise cheaper, more efficient applicators. This is particularly true when materials presenting high dielectric losses are processed.
Mat. Res. Soc. Symp. Proc. Vol. 189. 01991 Materials Research Society
118
MODULAR APPLICATORS In the course of several years of applicator development, applicators we have concentrated efforts on designing modular for continuous processing, utilizing cheap materials and cheap ovens. generators, based on components for domestic microwave liquids, process In several applications, we had to in suspensions, or granulate materials [1], which could flow Modular applicators, utilizing cavities or other basic tubes. devices were developed for processing these materials. is required power level In similar cases, when the total small relatively low, it is possible to resort to a number of (made of tube cavities in tandem, crossed by a dielectric Thus, each cavity, glass or other low-loss material) [fig. 1]. modulus, connected to a low-power magnetron, is an independent is
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