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Technical Briefs

Effect of Absorptive Coating of the Hot Fluid Passage of a Heat Exchanger Employing Exergy-Optimized Pin Fins in High Temperature Applications

[+] Author and Article Information
Nwosu P. Nwachukwu1

Department of Mechanical Engineering, National Center for Energy Research and Development (NCERD), University of Nigeria, Nsukka, Nigeriapn_nwosu@yahoo.com, ebere_ay@yahoo.com

Samuel O. Onyegegbu

Department of Mechanical Engineering, National Center for Energy Research and Development (NCERD), University of Nigeria, Nsukka, Nigeria

1

Corresponding author.

J. Heat Transfer 131(5), 054503 (Mar 17, 2009) (4 pages) doi:10.1115/1.3013827 History: Received November 10, 2007; Revised September 09, 2008; Published March 17, 2009

An expression for the optimum pin fin dimension is derived on exergy basis for a high temperature exchanger employing pin fins. The present result differs from that obtained by Poulikakos and Bejan (1982, “Fin Geometry for Minimum Entropy Generation in Forced Convection  ,” ASME J. Heat Transfer, 104, pp. 616–623) for a low temperature heat recovery application. Also, a simple relation is established between the amounts the base temperature of the optimized pin fin is raised for a range of absorptive coating values. Employing this relation, if the absorptivity of the coating, the plate emissivity, the number of protruding fins, and some area and fluid parameters are known, the corresponding value for the base temperature of the fin is immediately obtained. The analysis shows that the thermal performance of the exchanger improves substantially with a high absorptivity coating hence can be seen as a heat transfer enhancement feature of the exchanger operating with radiation dominance.

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Copyright © 2009 by American Society of Mechanical Engineers
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References

Figures

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Figure 5

Evolution of Ns with αc/ε and parameter ζ

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Figure 4

Effect of αc/ε and parameter ζ on the dimensionless fin base temperature θz

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Figure 3

Comparison of ReLopt results in laminar flow for various Nu values

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Figure 2

Schematic of a pin fin attached to a plate with prescribed heat duty

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Figure 1

Pin fin nomenclature

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