Term of Award

Spring 2012

Degree Name

Master of Science in Applied Engineering (M.S.A.E.)

Document Type and Release Option

Thesis (open access)

Department

Department of Mechanical Engineering

Committee Chair

Mosfequr Rahman

Committee Member 1

David Williams

Committee Member 2

Gustavo Molina

Abstract

Author's abstract: Numerical simulation was used to investigate natural convection in horizontal and vertical enclosures with and without an internal heat source. Natural convection in rectangular enclosures is found in many real-world applications. Included in these applications are the energy efficient design of buildings, operation and safety of nuclear reactors, solar collector design, passive energy storage, heat transfer across multi-pane windows, thermo-electric refrigeration and heating devices, and the design-for-mitigation of optical distortion in large-scale laser systems. Considering all these applications, especially controlling heat transfer in nuclear power plants, knowledge and research results of natural convection in enclosure play a vital role in environmental impact management studies. This study simulated horizontal enclosures heated from below (configuration 1) and vertical enclosures heated from the side (configuration 2) with a variety of different aspect ratios (AR) and Rayleigh numbers (Ra). Each aspect ratio (1, 2, 4, 6, 8, and 10) was examined using different sets of Rayleigh numbers. The first numerical experiment used only external Rayleigh number (RaE = 2x104, 2x105, and 2x106) which simulated natural convection in enclosures for outside temperature gradient only. The second case used a constant external Rayleigh number (RaE = 2x105) with a changing internal Rayleigh number (Ral = 2x104,2x105, and 2x106). The third simulation used a constant internal Rayleigh number (Ra l = 2x105) and a changing external Raleigh number (RaE = 2x104, 2x105, and 2x106). All three cases were simulated for each configuration and at each aspect ratio. The streamline and isotherm flow patterns were created to reflect each case. The average heat flux ratio and convection strength were also calculated. Tests with the external temperature gradient only confirmed previous studies. There were many notable outcomes in this study which are discussed in the main body of this thesis work. When RaE > Ral, the results were similar to the study with a varying external Rayleigh number (RaE) and no internal heat source.

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