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Journal of Heat Transfer | Volume 133 | Issue 5 | Research Paper
Research Papers: Forced Convection

Validation and Analysis of Numerical Results for a Varying Aspect Ratio Two-Pass Internal Cooling Channel

[+] Author and Article Information
Igor V. Shevchuk

Institute of Aerospace Thermodynamics (ITLR), University of Stuttgart, Pfaffenwaldring 31, 70569 Stuttgart, Germanyitlr@itlr.uni-stuttgart.de

Sean C. Jenkins, Bernhard Weigand, Jens von Wolfersdorf, Sven Olaf Neumann

Institute of Aerospace Thermodynamics (ITLR), University of Stuttgart, Pfaffenwaldring 31, 70569 Stuttgart, Germany

Martin Schnieder

 ALSTOM Power, Brown Boveri Strasse 7, 5401 Baden, Switzerland

J. Heat Transfer 133(5), 051701 (Jan 31, 2011) (8 pages) doi:10.1115/1.4003080 History: Received June 07, 2010; Revised November 13, 2010; Published January 31, 2011; Online January 31, 2011
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Numerical results for an internal ribbed cooling channel including a 180 deg bend with a 2:1 inlet and a 1:1 aspect ratio outlet channel were validated against experimental results in terms of spatially resolved heat transfer distributions, pressure losses, and velocity distributions. The numerical domain consisted of one rib segment in the inlet channel and three ribs segments in the outlet channel to reduce the overall numerical effort and allow for an extensive parametric study. The results showed good agreement for both heat transfer magnitudes and spatial distributions, and the numerical results captured the predominate flow physics resulting from the 180 deg bend. The production of Dean vortices and acceleration of the flow in the bend produced strongly increased heat transfer on both the ribbed and unribbed walls in the outlet channel in addition to increases due to the ribs. Numerical simulations were performed for a wide range of divider wall-to-tip wall distances, which influenced the position of the highest heat transfer levels on the outlet walls and changed the shape of the heat transfer distribution on the tip wall. Analysis of section averages of heat transfer in the bend and outlet channel showed a strong influence of the tip wall distance, while no effect was seen upstream of the bend. A similarly large effect on pressure losses in the bend was observed with varying tip wall position. Trends in averaged heat transfer varied linearly with tip wall distance, while pressure losses followed a nonlinear trend, resulting in an optimum tip wall distance with respect to heat transfer efficiency.
Copyright © 2011 by American Society of Mechanical Engineers
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References

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Tsang, C. L. P., Gillespie, D. R. H., Ireland, P. T., and Dailey, G. M., 2001, “Detailed Performance Assessment of 16% Blockage Interrupted Ribs at 60 degree Inclination in a Square Section Turbine Blade Cooling Passage,” NATO RTA/AVT Symposium on Advanced Flow Management , Norway, May 7–11.
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20
Jenkins, S. C., Zehnder, F., Shevchuk, I. V., von Wolfersdorf, J., Weigand, B., and Schnieder, M., 2008, “The Effect of Ribs and Tip Wall Distance on Heat Transfer for a Varying Aspect Ratio Two-Pass Ribbed Internal Cooling Channel,” Berlin, June 9–13, ASME , New York, Vol. 4 , Parts A and B, pp. 1051–1061.
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Figures

Grahic Jump Location
+Schematic view of the channel configuration used in the simulations: half-height of the channel of Jenkins (20), symmetry boundary condition on the upper surface
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Schematic view of the channel configuration used in the simulations: half-height of the channel of Jenkins (20), symmetry boundary condition on the upper surface
Figure 1

Schematic view of the channel configuration used in the simulations: half-height of the channel of Jenkins (20), symmetry boundary condition on the upper surface

Grahic Jump Location
+Heat transfer distribution over the bottom, tip, external, and internal (smaller sketch) side walls of the smooth channel with constant H/W=2:1 (simulations)
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Heat transfer distribution over the bottom, tip, external, and internal (smaller sketch) side walls of the smooth channel with constant H/W=2:1 (simulations)
Figure 2

Heat transfer distribution over the bottom, tip, external, and internal (smaller sketch) side walls of the smooth channel with constant H/W=2:1 (simulations)

Grahic Jump Location
+Heat transfer distribution over the bottom, tip, external, and internal (smaller sketch) side walls of the smooth channel with varying aspect ratio of H/W=2:1 (inlet) and H/W=1:1 (outlet), Wel=112.5 mm (simulations)
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Heat transfer distribution over the bottom, tip, external, and internal (smaller sketch) side walls of the smooth channel with varying aspect ratio of H/W=2:1 (inlet) and H/W=1:1 (outlet), Wel=112.5 mm (simulations)
Figure 3

Heat transfer distribution over the bottom, tip, external, and internal (smaller sketch) side walls of the smooth channel with varying aspect ratio of H/W=2:1 (inlet) and H/W=1:1 (outlet), Wel=112.5 mm (simulations)

Grahic Jump Location
+Effect of the Wel on average heat transfer in the inlet pass (faces 1a and 2), bend (faces 3 and 4), and outlet pass (faces 6a and 5), varying H/W=2:1 to H/W=1:1
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Effect of the Wel on average heat transfer in the inlet pass (faces 1a and 2), bend (faces 3 and 4), and outlet pass (faces 6a and 5), varying H/W=2:1 to H/W=1:1
Figure 4

Effect of the Wel on average heat transfer in the inlet pass (faces 1a and 2), bend (faces 3 and 4), and outlet pass (faces 6a and 5), varying H/W=2:1 to H/W=1:1

Grahic Jump Location
+Comparisons of the simulated and measured velocity vector fields in the symmetry plane at Wel=150 mm
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Comparisons of the simulated and measured velocity vector fields in the symmetry plane at Wel=150 mm
Figure 5

Comparisons of the simulated and measured velocity vector fields in the symmetry plane at Wel=150 mm

Grahic Jump Location
+Dean vortices in the bend region for different tip wall distances Wel=75 mm (upper) and Wel=150 mm (lower, both simulations, and PIV)
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Dean vortices in the bend region for different tip wall distances Wel=75 mm (upper) and Wel=150 mm (lower, both simulations, and PIV)
Figure 6

Dean vortices in the bend region for different tip wall distances Wel=75 mm (upper) and Wel=150 mm (lower, both simulations, and PIV)

Grahic Jump Location
+Effect of the Wel on the velocity vector field in the symmetry plane (simulations)
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Effect of the Wel on the velocity vector field in the symmetry plane (simulations)
Figure 7

Effect of the Wel on the velocity vector field in the symmetry plane (simulations)

Grahic Jump Location
+Effect of the Wel on the relative pressure drop ΔP∗
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Effect of the Wel on the relative pressure drop ΔP∗
Figure 8

Effect of the Wel on the relative pressure drop ΔP∗

Grahic Jump Location
+Heat transfer coefficient distribution over the bottom, tip, external, and internal (smaller sketch) side walls in the ribbed channel with varying aspect ratio of H/W=2:1 in the inlet and H/W=1:1 in the outlet, Wel=112.5 mm (simulations)
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Heat transfer coefficient distribution over the bottom, tip, external, and internal (smaller sketch) side walls in the ribbed channel with varying aspect ratio of H/W=2:1 in the inlet and H/W=1:1 in the outlet, Wel=112.5 mm (simulations)
Figure 9

Heat transfer coefficient distribution over the bottom, tip, external, and internal (smaller sketch) side walls in the ribbed channel with varying aspect ratio of H/W=2:1 in the inlet and H/W=1:1 in the outlet, Wel=112.5 mm (simulations)

Grahic Jump Location
+Heat transfer distribution over the bottom, tip, and external side walls of the ribbed channel with varying aspect ratio of H/W=2:1 in the inlet and H/W=1:1 in the outlet, Wel=112.5 mm (TLC experiments for Nu/Nu0)
View Large  |  Save Figure  |  Download Slide (.ppt)
Heat transfer distribution over the bottom, tip, and external side walls of the ribbed channel with varying aspect ratio of H/W=2:1 in the inlet and H/W=1:1 in the outlet, Wel=112.5 mm (TLC experiments for Nu/Nu0)
Figure 10

Heat transfer distribution over the bottom, tip, and external side walls of the ribbed channel with varying aspect ratio of H/W=2:1 in the inlet and H/W=1:1 in the outlet, Wel=112.5 mm (TLC experiments for Nu/Nu0)

Grahic Jump Location
+Effect of the Wel on average heat transfer on the tip wall (face 4) in the ribbed channel, varying H/W=2:1 to H/W=1:1
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Effect of the Wel on average heat transfer on the tip wall (face 4) in the ribbed channel, varying H/W=2:1 to H/W=1:1
Figure 11

Effect of the Wel on average heat transfer on the tip wall (face 4) in the ribbed channel, varying H/W=2:1 to H/W=1:1

Grahic Jump Location
+Effect of the Wel on average heat transfer on the bend bottom (face 3) in the ribbed channel, varying H/W=2:1 to H/W=1:1
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Effect of the Wel on average heat transfer on the bend bottom (face 3) in the ribbed channel, varying H/W=2:1 to H/W=1:1
Figure 12

Effect of the Wel on average heat transfer on the bend bottom (face 3) in the ribbed channel, varying H/W=2:1 to H/W=1:1

Grahic Jump Location
+Effect of the Wel on average heat transfer on the upstream bottom (face 2), bend bottom (face 3), and tip wall (face 4) in the ribbed channel, varying H/W=2:1 to H/W=1:1 (simulations)
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Effect of the Wel on average heat transfer on the upstream bottom (face 2), bend bottom (face 3), and tip wall (face 4) in the ribbed channel, varying H/W=2:1 to H/W=1:1 (simulations)
Figure 13

Effect of the Wel on average heat transfer on the upstream bottom (face 2), bend bottom (face 3), and tip wall (face 4) in the ribbed channel, varying H/W=2:1 to H/W=1:1 (simulations)

Grahic Jump Location
+Effect of the Wel on average heat transfer on the inlet pass side wall (face 1), bottom between ribs 1 and 2, outlet pass (face 5), bottom between ribs 2 and 3, outlet pass (face 6), and outlet pass side wall (face 7) in the ribbed channel, varying H/W=2:1 to H/W=1:1
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Effect of the Wel on average heat transfer on the inlet pass side wall (face 1), bottom between ribs 1 and 2, outlet pass (face 5), bottom between ribs 2 and 3, outlet pass (face 6), and outlet pass side wall (face 7) in the ribbed channel, varying H/W=2:1 to H/W=1:1
Figure 14

Effect of the Wel on average heat transfer on the inlet pass side wall (face 1), bottom between ribs 1 and 2, outlet pass (face 5), bottom between ribs 2 and 3, outlet pass (face 6), and outlet pass side wall (face 7) in the ribbed channel, varying H/W=2:1 to H/W=1:1

Grahic Jump Location
+Effect of the Wel on average heat transfer in the outlet pass over the bottom between ribs 1 and 2, (face 5), rib 1, and total of face 5 and rib 1 in the ribbed channel, varying H/W=2:1 to H/W=1:1 (simulations)
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Effect of the Wel on average heat transfer in the outlet pass over the bottom between ribs 1 and 2, (face 5), rib 1, and total of face 5 and rib 1 in the ribbed channel, varying H/W=2:1 to H/W=1:1 (simulations)
Figure 15

Effect of the Wel on average heat transfer in the outlet pass over the bottom between ribs 1 and 2, (face 5), rib 1, and total of face 5 and rib 1 in the ribbed channel, varying H/W=2:1 to H/W=1:1 (simulations)

Grahic Jump Location
+Effect of the Wel on aerothermal efficiency η (simulations)
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Effect of the Wel on aerothermal efficiency η (simulations)
Figure 16

Effect of the Wel on aerothermal efficiency η (simulations)

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