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Research Papers

Comparison of Pin Surface Heat Transfer in Arrays of Oblong and Cylindrical Pin Fins

[+] Author and Article Information
Kathryn L. Kirsch

e-mail: kathryn.kirsch@psu.edu

Jason K. Ostanek

e-mail: jason.ostanek@navy.mil

Karen A. Thole

e-mail: kthole@engr.psu.edu
Mechanical and Nuclear Engineering Department,
The Pennsylvania State University,
University Park, PA 16802

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received July 1, 2013; final manuscript received July 5, 2013; published online October 23, 2013. Editor: Ronald Bunker.

J. Turbomach 136(4), 041015 (Oct 23, 2013) (10 pages) Paper No: TURBO-13-1123; doi: 10.1115/1.4025213 History: Received July 01, 2013; Revised July 05, 2013

Pin fin arrays are most commonly used to promote convective cooling within the internal passages of gas turbine airfoils. Contributing to the heat transfer are the surfaces of the channel walls as well as the pin itself. Generally the pin fin cross section is circular; however, certain applications benefit from using other shapes such as oblong pin fins. The current study focuses on characterizing the heat transfer distribution on the surface of oblong pin fins with a particular focus on pin spacing effects. Comparisons were made with circular cylindrical pin fins, where both oblong and circular cylindrical pins had a height-to-diameter ratio of unity, with both streamwise and spanwise spacing varying between two and three diameters. To determine the effect of relative pin placement, measurements were taken in the first of a single row and in the third row of a multirow array. Results showed that area-averaged heat transfer on the pin surface was between 30 and 35% lower for oblong pins in comparison to cylindrical. While heat transfer on the circular cylindrical pin experienced one minimum prior to boundary layer separation, heat transfer on the oblong pin fins experienced two minimums, where one is located before the boundary layer transitions to a turbulent boundary layer and the other prior to separation at the trailing edge.

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Figures

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Fig. 1

Schematic of recirculating test facility used for both cylindrical and oblong pin fin testing [18]

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Fig. 2

Diagram used to describe streamwise and spanwise spacing definitions for oblong pin fin array

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Fig. 3

Schematic of oblong size and locations of thermocouples used in instrumentation

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Fig. 4

(a)–(c) Effect of ReD on the first row of both cylindrical and oblong pins at different spanwise spacings

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Fig. 5

(a)–(c) Effect of ReD on the third row of both cylindrical and oblong pins at different spanwise spacings

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Fig. 6

Direct comparison of the difference between the first and third row of the oblong pin fin array at ReD = 1.0 × 104 and S/D = 2.5

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Fig. 7

(a)–(c) Effect of spanwise spacing on heat transfer for the first row of oblong pins at three ReD

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Fig. 8

Effect of spanwise spacing on heat transfer for the first row of cylindrical pin fins at one ReD

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Fig. 9

(a)–(c) Effect of spanwise spacing on heat transfer for the third row of oblong pin fins at three ReD

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Fig. 10

Effect of spanwise spacing on heat transfer for the third row of cylindrical pin fins at one ReD

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Fig. 11

(a)–(c) Effect of streamwise spacing on heat transfer for the third row of oblong pin fins at one ReD

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Fig. 12

Effect of streamwise spacing on heat transfer for the third row of cylindrical pin fins at one ReD

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Fig. 13

Comparison of overall heat transfer in the first row of cylindrical and oblong pin fins at all spanwise and streamwise spacings

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Fig. 14

Comparison of overall heat transfer in the third row of cylindrical and oblong pin fins at all spanwise and streamwise spacings

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Fig. 15

Comparison of friction factor in arrays of cylindrical and oblong pins fins at all spanwise and streamwise spacings

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