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Research Papers

Heat Transfer Measurements of Oblong Pins

[+] Author and Article Information
Kathryn L. Kirsch

Mechanical and Nuclear Engineering Department,
Penn State University,
University Park, PA 16802
e-mail: kathryn.kirsch@psu.edu

Karen A. Thole

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

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received July 14, 2014; final manuscript received October 28, 2014; published online December 23, 2014. Editor: Ronald S. Bunker.

J. Turbomach 137(7), 071004 (Jul 01, 2015) (9 pages) Paper No: TURBO-14-1143; doi: 10.1115/1.4029124 History: Received July 14, 2014; Revised October 28, 2014; Online December 23, 2014

Pin fin arrays are employed as an effective means for heat transfer enhancement in the internal passages of a gas turbine blade, specifically in the blade's trailing edge. Various shapes of the pin itself have been used in such arrays. In this study, oblong pin fins are investigated whereby their long axis is perpendicular to the flow direction. Heat transfer measurements were taken at the pin midspan with unheated endwalls to isolate the pin heat transfer. Results show important differences in the heat transfer patterns between a pin in the first row and a pin in the third row. In the third row, wider spanwise spacing allows for two peaks in heat transfer over the pin surface. Additionally, closer streamwise spacing leads to consistently higher heat transfer for the same spanwise spacing. Due to the blunt orientation of the pins, the peak in heat transfer occurs off the stagnation point.

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References

Figures

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Fig. 1

Schematic of the recirculating test facility [18]

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Fig. 2

Orientation and dimensions of oblong pins 90 deg to the flow. The spacing definitions were normalized by “d” while the Reynolds number and Nusselt number length scales were “D.”

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Fig. 3

Location of thermocouples placed around the perimeter of the oblong with key s/d locations. 0 ≤ s/d ≤ 0.54 will be referred to as the upstream side of the oblong and 2.04 ≤ s/d ≤ 2.57 will be referred to as the downstream side of the oblong. The maximum width of the oblong is located at s/d = 1.28. The side of the oblong fully instrumented with thermocouples is the positive flow side that is marked with the s/d locations, while the opposite side is the negative flow side.

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Fig. 4

Reynolds number effects on the first row of oblong pins at the middle spanwise spacing tested, S/d = 3.5 (all pin surface data on the positive flow side, 0 ≤ s/D ≤ 2.57, were mirrored)

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Fig. 5

(a)–(c) Reynolds number effects on the third row of pins at the three spanwise spacings tested

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Fig. 6

(a) and (b) Spanwise spacing effects on the first row of oblong pins at two ReD

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Fig. 7

(a) and (b) Spanwise spacing effects on the third row of oblong pins at two ReD

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Fig. 8

(a)–(c) Streamwise spacing effects on the third row of pins at the highest ReD

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Fig. 9

Direct comparison of 90 oblong pin, 0 deg oblong pin and circular cylindrical pin in the first row with matched ReDh

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Fig. 10

Direct comparison of 90 oblong pin, 0 oblong pin, and circular cylindrical pin in the third row with matched ReDh

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Fig. 11

Stagnation point heat transfer in the first and third rows of an array versus ReD

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Fig. 12

Average heat transfer in the third row of an array versus ReD compared with correlations found in literature

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