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Research Papers

Conjugate Thermal Analysis of Air-Cooled Discrete Flush-Mounted Heat Sources in a Horizontal Channel

[+] Author and Article Information
Jing He1

Department of Mechanical Science and Engineering,  University of Illinois, 1206 West Green Street, Urbana, IL 61801 jinghe2@illinois.edu

Liping Liu

Department of Mechanical Engineering,  Lawrence Technological University, 21000 West Ten Mile Road, Southfield, MI 48075

Anthony M. Jacobi

Department of Mechanical Science and Engineering,  University of Illinois, 1206 West Green Street, Urbana, IL 61801

1

Corresponding author.

J. Electron. Packag 133(4), 041001 (Nov 17, 2011) (8 pages) doi:10.1115/1.4005299 History: Received July 11, 2011; Revised September 07, 2011; Published November 17, 2011; Online November 17, 2011

Thermal analysis with comprehensive treatment of conjugate heat transfer is performed in this study for discrete flush-mounted heat sources in a horizontal channel cooled by air. The numerical model accounts for mixed convection, radiative exchange and two-dimensional conduction in the substrate. The model is first used to simulate available experimental work to demonstrate its accuracy and practical utility. A parametric study is then undertaken to assess the effects of Reynolds number, surface emissivity of walls and heat sources, as well as thickness and thermal conductivity of substrate, on flow field and heat transfer characteristics. It is shown that due to radiative heat transfer, the wall temperatures are brought closer, and the trend of temperature variation along the top wall is significantly altered. Such effects are more pronounced for higher surface emissivity and/or lower Reynolds numbers. The influence of substrate conductivity and thickness is related in that a large value of either substrate conductivity or thickness facilitates redistribution of heat and tends to yield a uniform temperature field in the substrate. For highly conductive or thick substrate, the “hot spot” cools down and may occur in upstream sources. Radiation loss to the ambient increases with substrate conductivity and thickness due to the elevated temperature near the openings, yet the total heat transfer over the bottom surface by convection and radiation remains essentially unaltered.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 10

Normalized temperature field, T/T0 , at (a) ks /kf  = 2, (b) ks /kf  = 50, and (c) ks /kf  = 200 (Re = 100, ɛw  = ɛs  = 1 and Hs  = 0.5)

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Figure 11

Distributions of normalized convective, conductive, and radiative fluxes along the bottom surface at Re = 100, Hs  = 0.5, ɛw  = ɛs  = 1 and varying ks /kf

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Figure 12

Relative contributions in heat dissipation from the discrete sources by different transfer modes for ks /kf  = 2 and ks /kf  = 200 (Re = 100, ɛw  = ɛs  = 1 and Hs  = 0.5)

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Figure 13

Normalized temperature distribution along the bottom surface for Re = 100, ks /kf  = 200, ɛw  = ɛs  = 1 and varying Hs /H

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Figure 1

Schematic of a parallel-plate channel

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Figure 2

Comparison of the local Nusselt number distribution at ReDh=1000 for an array of discrete flush-mounted heat sources between the numerical and the experimental results (see Fig. 3 in Ref. [17] for details)

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Figure 3

Observation of the flow field using smoke visualization [12], streamline pattern and temperature field predicted by the current model for (a) Re = 9.48 and (b) Re = 29.7 (see Fig. 4 in Ref. [12] for details)

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Figure 4

Comparison of the surface temperature distribution along the channel floor between the experimental data [12] and the predictions by the model without consideration of radiation effects [12] and the present comprehensive model (see Fig. 8 in Ref. [12] for details)

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Figure 5

Streamline plots at (a) Re = 1000 and (b) Re = 100 for ɛw  = ɛs  = 1 and Hs  = 0 (the line segments on the bottom represent the heat sources)

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Figure 6

Normalized temperature field, T/T0 : (a) with black radiation for Re = 1000 (top) and Re = 100 (bottom) and (b) without radiation for Re = 1000 (top) and Re = 100 (bottom)

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Figure 7

Normalized temperature distribution for Re = 100, Hs  = 0 and varying emissivity along (a) the bottom surface and (b) the top surface

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Figure 8

Relative contributions in heat dissipation from the discrete sources by convection and radiation for Re = 100, Hs  = 0 and varying emissivity

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Figure 9

Normalized temperature distribution along the bottom surface for Re = 100, Hs  = 0.5, ɛw  = ɛs  = 1 and varying ks /kf

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