Date of Award

Fall 1997

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Mechanical Engineering - (Ph.D.)

Department

Mechanical Engineering

First Advisor

Pasquale J. Florio

Second Advisor

Rong-Yaw Chen

Third Advisor

Robert P. Kirchner

Fourth Advisor

E. S. Geskin

Fifth Advisor

Manuel Perez

Abstract

Three-dimensional natural convection from three-by-three array of isoflux heat sources mounted on one vertical wall of semi-enclosed region has been numerically investigated. Detailed thermal information of this important engineering configuration is currently not available. The major objective of this study was to obtain this needed thermal and velocity information.

The semi-enclosed geometry can be viewed as a thin rectangular region with four closed and two open sides. The open surfaces are located at the top and adjacent side. For the fluid air, Pr = 0.71, the study covered a heat flux based Rayleigh number (Ra) range of (102 ≤ R ≤ 105). Uniform and non-uniform distribution of the sources were investigated as well as the effect of varying the depth of the sources protrusions (aspect ratio varied from 0 to 0.5).The numerical simulation was carried out using the finite element program FIDAP (Fluid Dynamics International).

The results show the strong three-dimensionality of this flow. For large Ra numbers 105, the possibility of recirculating flow exists at the top and side surfaces. For some non-uniform distributed arrays, instability were found to occur. For the Ra number and parameters ranges studied, a detailed analysis and discussion of the thermal and flow fields are presented. Nusselt number(Nu) variation, location and magnitudes of surface temperature extremes and variations are presented.

It is shown that for the given geometry and parametric range, the overall average Nu number can be approximated by the simple relation Nu = 1.167 Ra0.1443.

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