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Research Papers

The Effect of Element Thermal Conductivity on Turbulent Convective Heat Transfer From Rough Surfaces

[+] Author and Article Information
Stephen T. McClain

Department of Mechanical Engineering, Baylor University, One Bear Place #97356, Waco, TX 76798

B. Keith Hodge

Department of Mechanical Engineering, Mississippi State University, P.O. Box ME, Mississippi State, MS 39762

Jeffrey P. Bons

Department of Aerospace Engineering, Ohio State University, 2300 West Case Road, Columbus, OH 43210

J. Turbomach 133(2), 021024 (Oct 26, 2010) (10 pages) doi:10.1115/1.4001191 History: Received July 28, 2009; Revised October 08, 2009; Published October 26, 2010; Online October 26, 2010

The discrete-element model for flows over rough surfaces considers the heat transferred from a rough surface to be the sum of the heat convected from the flat surface and the heat convected from the individual roughness elements to the fluid. In previous discrete-element model developments, heat transfer experiments were performed using metallic or high-thermal conductivity roughness elements. Many engineering applications, however, exhibit roughness with low thermal conductivities. In the present study, the discrete-element model is adapted to consider the effects of finite thermal conductivity of roughness elements on turbulent convective heat transfer. Initially, the boundary-layer equations are solved while the fin equation is simultaneously integrated so that the full conjugate heat transfer problem is solved. However, a simpler approach using a fin efficiency is also investigated. The results of the conjugate analysis and the simpler fin efficiency analysis are compared to experimental measurements for turbulent flows over ordered cone surfaces. Possibilities for extending the fin efficiency method to randomly rough surfaces and the experimental measurements required are discussed.

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References

Figures

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Figure 1

Control volume for discrete-element roughness model development

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Figure 2

ks/keff versus Λs evaluated using the characteristics of the roughness elements above the mean elevation (reprinted from Ref. 25)

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Figure 3

Mean elevation of the cone surfaces

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Figure 4

Temperature profiles for Surface 1 at the roughness panel midpoint and Rex¯=901,000 using the mean elevation as a datum

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Figure 5

Temperature profiles for Surface 2 at the roughness panel midpoint and Rex¯=876,000 using the mean elevation as a datum

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