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TECHNICAL PAPERS: Forced Convection

Variable Property and Temperature Ratio Effects on Nusselt Numbers in a Rectangular Channel With 45 Deg Angled Rib Turbulators

[+] Author and Article Information
G. I. Mahmood, P. M. Ligrani, K. Chen

Convective Heat Transfer Laboratory, Department of Mechanical Engineering, University of Utah, Salt Lake City, UT 84112

J. Heat Transfer 125(5), 769-778 (Sep 23, 2003) (10 pages) doi:10.1115/1.1589503 History: Received March 26, 2002; Revised March 20, 2003; Online September 23, 2003
Copyright © 2003 by ASME
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References

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Parsons,  J. A., Han,  J. C., and Zhang,  Y., 1995, “Effects of Model Orientation and Wall Heating Condition on Local Heat Transfer in a Rotating Two-pass Square Channel With Rib Turbulators,” Int. J. Heat Mass Transfer, 38, pp. 1151–1159.
Taslim,  M. E., and Lengkong,  A., 1998, “45 deg Staggered Rib Heat Transfer Coefficient Measurements in a Square Channel,” ASME J. Turbomach., 120, pp. 571–580.
Ligrani, P. M., and Mahmood, G. I., 2003, “Spatially-Resolved Heat Transfer and Friction Factors in a Rectangular Channel with 45 Deg Angled Crossed-Rib Turbulators,” ASME J. Turbomach., to appear.
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Cho, H. H., Lee, S. Y., and Wu, S. J., 2001, “The Combined Effects of Rib Arrangement and Discrete Ribs on Local Heat/Mass Transfer in a Square Duct,” Paper No. 2001-GT-175, International Gas Turbine and Aeroengine Congress and Exhibition, New Orleans, Louisiana, pp. 1–11.
Mahmood,  G. I., and Ligrani,  P. M., 2002, “Heat Transfer in a Dimpled Channel: Combined Influences of Aspect Ratio, Temperature Ratio, Reynolds Number, and Flow Structure,” Int. J. Heat Mass Transfer, 45(10), pp. 2011–2020.
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Figures

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Schematic diagram of experimental apparatus used for heat transfer measurements.
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Schematic diagram of the rib turbulator test surface, including the dimensions and coordinate system.
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Baseline, constant property Nusselt numbers, measured with smooth channel surfaces and constant heat flux boundary condition on all channel surfaces for Toi/Tw=0.92–0.94, as dependent upon Reynolds number ReDh based on hydraulic diameter.
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Baseline, variable property Nusselt number ratios in a smooth channel, measured with a constant heat flux boundary condition on all channel surfaces, as dependent upon temperature ratio Toi/Tw.
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Time-averaged local Nusselt number ratio Nu/Nuo,cp distribution along the rib turbulator test surface for ReH=18,300 and Toi/Tw=0.93.
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Time-averaged local Nusselt number ratio Nu/Nuo,cp distribution along the rib turbulator test surface for ReH=22,100 and Toi/Tw=0.82.Nu/Nuo,cp scale is same as one shown in Figure 5.
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Time-averaged local Nusselt number ratio Nu/Nuo,cp distribution along the rib turbulator test surface for ReH=27,400 and Toi/Tw=0.74.Nu/Nuo,cp scale is same as one shown in Figure 5.
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Local Nusselt number ratios Nu/Nuo,cp as they vary in the normalized streamwise direction at Z/Dh=0.00 for different temperature ratios Toi/Tw.
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Local Nusselt number ratios Nu/Nuo,cp as they vary in the normalized spanwise direction at X/Dh=6.90 for different temperature ratios Toi/Tw. Symbols are defined in Figure 8.
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Schematic diagram of a portion of the bottom rib turbulator test surface showing the layout of three ribs and the local coordinates W/Dh and L/Dh, which are oriented perpendicular and parallel to the ribs, respectively.
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Spatially-averaged Nusselt number ratios Nu/Nuo,cp determined from averages in the W/Dh direction, as dependent upon the normalized L/Dh coordinate, for different values of Toi/Tw.
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Spatially-averaged Nusselt number ratios Nu/Nuo,cp determined from averages in the L/Dh direction, as dependent upon the normalized W/Dh coordinate, for different values of Toi/Tw. Symbols are defined in Figure 11.
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Globally-averaged Nusselt number ratios Nu̿/Nuo,cp for fully developed flow conditions as dependent upon Toi/Tw for different ReH.
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Globally-averaged friction factor ratios f/fo,cp for fully developed flow conditions as dependent upon Toi/Tw for different ranges of the Reynolds number, ReH.
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Ratios of variable-property (globally-averaged) rib-turbulator Nusselt numbers to constant-property (globally-averaged) rib turbulator Nusselt numbers Nu̿/Nu̿cp as dependent upon the temperature ratio Toi/Tw, for the present rib turbulator channel, and other heat transfer augmentation devices 918.
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Ratios of variable-property, rib turbulator friction factors to constant-property, rib turbulator friction factors f/fcp as dependent upon temperature ratio Toi/Tw, for the present rib turbulator channel.
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Rib turbulator channel thermal performance parameters as dependent upon Toi/Tw for ReH from 10,000 to 83,700, including comparisons with thermal performance parameter magnitudes produced by other heat transfer augmentation devices 918.

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