Engineering design of high-power microwave applicators for stored product protection
Abstract:
The hypothesis, that excitation of an infested product at frequencies within the free water relaxation band above 18GHz would enhance selective heating of insects, has been tested at a frequency of 28GHz with load energies ranging from 20 to 62 J per gram of infested product.
Both dynamic (flowing) and static samples of soft white wheat (Triticum aestivum) infested with adults and larvae
of the maize weevil, Sitophilus zeamais Motschulasky were exposed in a detuned resonant cavity applicator.
A mortality of approximately 100% for adults and older larvae (and pupae) and >94% for the younger larvae (and eggs) was achieved in both cases.
However, the efficiency of the energy coupling in the dynamic case was nearly twice as great as for the static.
Maximum product temperatures ranged from 35 to 52 degrees Celsius. Subsequent measurements of penetration depth of a singly traveling plane wave in a flowing grain-air mixture, including wheat and rice, indicated penetration depths of 30 to 38 cm.
The design principles learned in constructing the dynamic applicator will be used to develop a prototype unit capable of processing the infested product at rates of 27 metric tons/h.
Co-collaborators of this paper are:
Steven L. Halverson, Timothy S. Bigelow, Rudy Plarre, and Thomas W. Philips |
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the complete paper in .pdf format HERE
The applicator (patent number 6,073,365) is similiar in design to a grain storage silo.
A microwave guide (patent number 6,192,598 B1), not shown, is connected onto the side of the applicator. |
