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Modeling and Optimization of a Three-Stage Conveyor Type Dryer for the Dehydration of Onion Slices

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  023147,  2002 ASAE Annual Meeting . (doi: 10.13031/2013.11233) @2002
Authors:   R. S. RAPUSAS, R. H. DRISCOLL
Keywords:   Modeling; optimization; onion dryer; mathematical model; optical index; parameters

A heat and mass balance model of the drying process in a three-stage conveyor type dryer based on a finite difference approach was developed as a tool for optimizing such a drying system. The thermo-physical properties of onion slices (Allium cepa L.) required by the model were represented by empirical equations. A quality model describing the changes in optical index of the onion slices during drying was incorporated in the drying model. In order to solve the drying model a computer program was developed and validated using experimental data from pilot-scale tests in a computer-aided experimental onion dryer simulating the commercial three-stage onion drying process. The product temperature and moisture content predictions of the computerized drying simulation model showed good agreement with the results of the thick-bed onion drying experiments. With the validated model and given a specific drying capacity requirement, the drying of onion slices in a three-stage conveyor dryer was optimized in terms of specific energy consumption within specified quality limits for product moisture content and optical index.

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