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Research Papers: Jets, Wakes, and Impingment Cooling

Impingement Heat Transfer on a Cylindrical, Concave Surface With Varying Jet Geometries

[+] Author and Article Information
C. Neil Jordan

Department of Mechanical Engineering,
Baylor University,
Waco, TX 76798-7356

Lesley M. Wright

Department of Mechanical Engineering,
Baylor University,
Waco, TX 76798-7356
e-mail: Lesley_Wright@Baylor.edu

Daniel C. Crites

Honeywell Aerospace,
Phoenix, AZ 85034

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received March 11, 2016; final manuscript received July 13, 2016; published online August 23, 2016. Assoc. Editor: Amy Fleischer.

J. Heat Transfer 138(12), 122202 (Aug 23, 2016) (10 pages) Paper No: HT-16-1127; doi: 10.1115/1.4034180 History: Received March 11, 2016; Revised July 13, 2016

Jet impingement is often employed within the leading edge of turbine airfoils to combat the heat loads incurred within this region. This experimental investigation employs a transient liquid crystal technique to obtain detailed Nusselt number distributions on a concave, cylindrical surface that models the leading edge of a turbine airfoil. The effect of hole shape and differing hole inlet and exit conditions are investigated. Two hole shapes are studied: cylindrical and racetrack-shaped holes; for each hole shape, the hydraulic diameter and mass flow rate into the array of jets is conserved. As a result, the jet's Reynolds number varies between the two jet arrays. Reynolds numbers of 13,600, 27,200, and 40,700 are investigated for the cylindrical holes, and Reynolds numbers of 11,500, 23,000, and 34,600 are investigated for the racetrack holes. Three inlet and exit conditions are investigated for each hole shape: a square edged, a partially filleted, and a fully filleted hole. The ratio of the fillet radius to hole hydraulic diameter is set at 0.25 and 0.667 for the partially and fully filleted holes, respectively, while all other geometrical features remain constant. Results show the Nusselt number is directly related to the Reynolds number for both cylindrical and racetrack-shaped holes. The racetrack holes are shown to provide enhanced heat transfer compared to the cylindrical holes. The degree of filleting at the inlet and outlet of the holes affects whether the heat transfer on the leading edge model is further enhanced or degraded.

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References

Figures

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Fig. 1

Layout of the experimental facility

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Fig. 2

Leading edge test section (a) overview and (b) cross-sectional view (all dimensions in cm)

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Fig. 3

Geometrical details of jet plates with (a) cylindrical holes and (b) racetrack-shaped holes

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Fig. 4

Detailed Nusselt number distributions for cylindrical jets—square edge (top), partially filleted edge (center), and fully filleted edge (bottom)

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Fig. 5

Conceptual view of flow conditions for varying jet edges

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Fig. 6

Detailed Nusselt number distributions for racetrack jets—square edge (top), partially filleted edge (center), and fully filleted edge (bottom)

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Fig. 7

Centerline Nusselt number distributions

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Fig. 8

Laterally averaged Nusselt number distributions

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Fig. 9

Area averaged Nusselt number comparisons: (a) comparison to Chupp et al. [4] correlation (Eq. (1)); (b) overall averaged Nusselt number.

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Fig. 10

Discharge coefficients for center jet

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