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Heat Transfer Enhancement

Effect of Rib Spacing on Heat Transfer in a Two Pass Rectangular Channel (AR = 2:1) at High Rotation Numbers

[+] Author and Article Information
Jiang Lei, Je-Chin Han

 Department of Mechanical Engineering, Texas A&M University, College Station, TX 77843-3123jc-han@tamu.edu

Michael Huh

 Schlumberger, Rosharon, TXmhuh@slb.com

J. Heat Transfer 134(9), 091901 (Jul 09, 2012) (9 pages) doi:10.1115/1.4006298 History: Received February 19, 2012; Revised February 20, 2012; Published July 09, 2012; Online July 09, 2012

In this paper, the effect of rib spacing on heat transfer in a rotating two-passage channel (aspect ratio, AR = 2:1) at orientation angle of 135 deg was studied. Parallel ribs were applied’ on leading and trailing walls of the rotating channel at the flow angle of 45 deg. The rib-height-to-hydraulic diameter ratio (e/Dh ) was 0.098. The rib-pitch-to-rib-height (P/e) ratios studied were 5, 7.5, and 10. For each rib spacing, tests were taken at five Reynolds numbers from 10,000 to 40,000, and for each Reynolds number, experiments were conducted at four rotational speeds up to 400 rpm. Results show that the heat transfer enhancement increases with decreasing P/e from 10 to 5 under nonrotation conditions. However, the effect of rotation on the heat transfer enhancement remains about the same for varying P/e from 10 to 5. Correlations of Nusselt number ratio (Nu/Nus ) to rotation number (Ro) or local buoyancy parameter (Box ) are existent on all surfaces (leading, trailing, inner and outer walls, and tip cap region) in the two-passage 2:1 aspect ratio channel.

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

Gas turbine internal cooling passages

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Figure 2

(a) 3D view of the 2X1 aspect ratio test section. (b) Top view of the test section showing names of walls and corresponding heaters. (c) Section view of the test section showing copper plate numbering.

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Figure 3

Conceptual flow patterns around ribs and turn

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Figure 4

Conceptual secondary vortices induced by (a) rotation and (b) angled ribs

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Figure 5

(a) Rotation number and (b) buoyancy parameter at different Reynolds numbers and rotational speeds

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Figure 6

Stationary streamwise Nu ratio (Nus /Nuo ) distribution at (a) Re = 20,000 and (b) Re = 40,000

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Figure 7

Streamwise Nu ratio (Nu/Nuo ) distribution at Re = 20,000 on (a) trailing and leading walls and (b) outer and inner walls

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Figure 8

Nu/Nus distribution versus rotation number on all surfaces at regions #4 and #9

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Figure 9

Nu/Nus distribution versus local buoyancy parameter in the 180 deg turn portion at regions #6 and #7

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