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Drying Technology
An International Journal
Volume 19, 2001 - Issue 8
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Original Articles

MOISTURE DIFFUSIVITY BEHAVIOR DURING FREEZE DRYING UNDER MICROWAVE HEATING POWER APPLICATION

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Pages 1613-1627 | Published online: 06 Feb 2007
 

Abstract

The necessary criteria for the design of a freeze-drying operation, where radiant and microwave heating are combined, are analyzed in this work. Microwave heating presents indubitable advantages for enhancing drying kinetics. Modifications of different value characteristics must be also considered. Different freeze-drying strategies using MW heating are analyzed taking into account kinetics and diffusivity behavior compared to a constant diffusivity model. A microwave on-off cycled strategy with simultaneous up-down modification of pressure was found an acceptable power regulation system when magnetrons, whose field strength exceeds the breakdown voltage of gas, are used. In this case, chamber pressure becomes a convenient control parameter to avoid plasma discharge and subsequent melting of product. Different evolutions of specific power inputs per gram were proposed depending on the size and disposition of the product.

ACKNOWLEDGMENTS

This work corresponds to the first experimental part of the project 2FD1997-0524-C02-01, that is being developed with economical support of CICYT (Spain) and FEDER funds of the EU.

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