Document Type

Thesis - University Access Only

Award Date

1994

Degree Name

Master of Science (MS)

Department / School

Mechanical Engineering

First Advisor

Kurt D. Bassett

Abstract

The phenomenon of fluid flow through porous media is of significant interest in various disciplines of engineering sciences. The Newton's law of friction together with the classical Navier-Stokes equation of hydrodynamics, provide a basis for studying the behavior of fluids under motion through porous media. However, in many systems of interest, the resulting equations become so complex that their solutions are impracticable. Recognizing this, several empirical relations relating head loss and velocity have been proposed for different media. This study examines the case of air flow through the agricultural commodity, hay. This valuable crop is exposed to severe losses in terms of both quantity and quality, as a result of the present harvesting, curing, and storage systems. To reduce the losses it is necessary to design an efficient drying system, in which the air distribution will be more even and rapid throughout the media. Such a design can only be possible by knowing the air distribution in the entire domain. But most of these drying installations are such that the air paths may diverge or converge and air velocities may vary along flow lines, thus making non-linear flow of special interest. In the process of investigating this concept in a full scale application, an experimental system was constructed, to measure the flow parameters at various locations in the media. The proposed approach to calculate the flow parameters of air in the entire media is by numerically solving the governing partial differential equation modeling the air flow, together with the existing empirical relation. This empirical relation was suggested in several grain drying systems. The finite element method was adopted to solve the above equations and to estimate the flow and pressure distributions throughout the media. In order to justify the applicability of the above empirical relation, statistical methods were adopted to compare the measured and the calculated values of static pressures at various locations. From the results it can be concluded that the adopted empirical relation can only give poor flow predictions in the hay drying systems. Further hypothesis test results indicate that these predictions are better in the low pressure regions and are worse in high pressure regions. Also the plots of velocity vectors and iso-pressure lines were generated in the entire media, to better visualize the flow distribution. Finally, suggestions for achieving better flow predictions have been included in the study.

Library of Congress Subject Headings

Hay -- Drying
Porous materials
Air flow
Finite element method

Format

application/pdf

Publisher

South Dakota State University

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Rights Statement

In Copyright