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TECHNICAL PAPERS

Heat Transfer on Internal Surfaces of a Duct Subjected to Impingement of a Jet Array with Varying Jet Hole-Size and Spacing

[+] Author and Article Information
U. Uysal

Department of Mechanical Engineering,  Sakarya University, 54187 Sakarya, Turkey

P.-W. Li

Department of Mechanical Engineering,  University of Pittsburgh, Pittsburgh, PA 15261

M. K. Chyu

Department of Mechanical Engineering,  University of Pittsburgh, Pittsburgh, PA 15261mkchyu@engr.pitt.edu

F. J. Cunha

 Pratt and Whitney, United Technologies, East Hartford, CT 06108

J. Turbomach 128(1), 158-165 (Feb 01, 2005) (8 pages) doi:10.1115/1.2101859 History: Received October 01, 2004; Revised February 01, 2005

One significant issue concerning the impingement heat transfer with a jet array is related to the so-called “crossflow,” where a local jet performance is influenced by the convection of the confluence from the impingement of the jet∕jets placed upstream. As a result, the heat transfer coefficient may vary along the streamwise direction and creates more or less nonuniform cooling over the component, which is undesirable from both the performance and durability standpoints. Described in this paper is an experimental investigation of the heat transfer coefficient on surfaces impinged by an array of six inline circular jets with their diameters increased monotically along the streamwise direction. The local heat transfer distributions on both the target surface and jet-issuing plate are measured using a transient liquid crystal technique. By varying the jet hole-size in a systematic manner, the actual distribution of jet flow rate and momentum within a jet array may be optimally metered and controlled against crossflow. The effects on the heat transfer coefficient distribution due to variations of jet-to-target distance and interjet spacing are investigated. The varying-diameter results are compared with those from a corresponding array of uniform jet diameter.

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Copyright © 2005 by American Society of Mechanical Engineers
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Figures

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Figure 2

Experimental setup

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Figure 3

Images of local heat transfer coefficients on target plate (S=6.5Dj‐up, H∕Dh=1.45, H=12.7mm)

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Figure 4

Spanwise-average Nusselt number for target plate (Re=22,000, S=6.5Dj‐up)

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Figure 5

Effect of Reynolds number on target plate heat transfer (S=6.5Dj‐up, H∕Dh=1.45, H=12.7mm)

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Figure 6

Jet-to-crossflow velocity ratio

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Figure 7

Jet-to-crossflow flow rate ratio and individual jet flow rate contribution

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Figure 8

Images of the local heat transfer coefficients on jet plate (S=6.5Dj‐up, H∕Dh=1.45 or H=12.7mm)

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Figure 9

Spanwise-average Nusselt number for jet plate (Re=22,000, S=6.5Dj‐up)

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Figure 10

Effects of Reynolds number effects on jet plate heat transfer (S=6.5Dj‐up, H∕Dh=1.45, or H=12.7mm)

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Figure 11

Span-average Nusselt number on target plate with uniform jet diameter (S=6.5Dh, H∕Dh=1.6, or H=12.7mm)

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Figure 12

Span-average Nusselt number on jet plate with uniform jet diameter (S=6.5Dh, H∕Dh=1.6, or H=12.7mm)

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Figure 13

Area-average heat transfer coefficient and effect of interjet spacing

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