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Research Papers: Forced Convection

Enhancement of Thermohydraulic Performance of Turbulent Flow in Rectangular and Square Ribbed Ducts With Twisted-Tape Inserts

[+] Author and Article Information
Ashis K. Mazumder

Department of Applied Mechanics and Drawing, Bengal Engineering and Science University, Shibpur, Howrah 711 103, West Bengal, Indiaashis.mazumadar@rediffmail.com

Sujoy K. Saha1

Mechanical Engineering Department, Bengal Engineering and Science University, Shibpur, Howrah 711 103, West Bengal, Indiasujoy̱ḵsaha@hotmail.com

1

Corresponding author.

J. Heat Transfer 130(8), 081702 (Jun 03, 2008) (10 pages) doi:10.1115/1.2909611 History: Received May 15, 2007; Revised August 18, 2007; Published June 03, 2008

The thermohydraulic performance of turbulent flow of air through rectangular and square ribbed ducts with twisted-tape inserts has been experimentally studied. The performance is influenced by the twisted-tape-generated swirl flow and the boundary layer separation, reattachment, and flow recirculation due to the ribs. Correlations developed for friction factor and Nusselt number satisfactorily predict the experimental data. The performance of the ribbed ducts with full-length twisted-tape inserts is found to be better than only ribbed ducts and ducts with only twisted-tape inserts. The regularly spaced twisted-tape elements in specific cases significantly perform better than their full-length counterparts. However, the short-length twisted-tape performance is worse than the full-length twisted tapes.

Copyright © 2008 by American Society of Mechanical Engineers
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Figures

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Figure 1

(a) Layout of a duct containing a full-length twisted-tape; (b) layout of a duct containing regularly spaced twisted-tape elements; (c) duct cross sections showing rib and twisted-tape inside the ducts

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Figure 2

(a) Sketch of the test channels and plenums; (b) test channel cross section; (c) distributions of electrical foil heaters

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Figure 3

Comparison of present friction factor data with other data, AR=0.333; only twisted tape (full-length twisted tape); only ribs, e∕Dh=0.0735, P∕e=10; ribs and short-length twisted tape; l=0.9, e∕Dh=0.0735, P∕e=10; for all cases, Y=2.5

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Figure 4

Comparison of present friction factor data with other data, AR=0.333; only regularly spaced twisted-tape elements, s=2.5; only ribs, e∕Dh=0.0735, P∕e=10; ribs and regularly spaced twisted-tape elements; s=2.5, e∕Dh=0.0735, P∕e=10; for all cases, Y=2.5

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Figure 5

Comparison of present Nusselt number data with other data, AR=0.333; only twisted tape (full-length twisted tape); only ribs, e∕Dh=0.0735, P∕e=10; ribs and short-length twisted tape; l=0.9, e∕Dh=0.0735, P∕e=10; for all cases, Y=2.5

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Figure 6

Comparison of present Nusselt number data with other data, AR=0.333; only regularly spaced twisted-tape elements, s=2.5; only ribs, e∕Dh=0.0735, P∕e=10; ribs and regularly spaced twisted-tape elements; s=2.5, e∕Dh=0.0735, P∕e=10; for all cases, Y=2.5

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Figure 7

Effect of twisted-tape length (TTP)—friction versus Reynolds number—AR=1, e∕Dh=0.0441, P∕e=10; for all cases, Y=2.5

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Figure 8

Effect of duct aspect ratio (DP)—friction versus Reynolds number—l=0.7, e∕Dh=0.0441, P∕e=20; for all cases, Y=2.5

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Figure 9

Effect of rib height (RP)—friction versus Reynolds number—l=0.9, AR=0.333, P∕e=10; for all cases, Y=2.5

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Figure 10

Effect of rib pitch (RP)—friction versus Reynolds number—l=0.9, AR=0.5, e∕Dh=0.0441; for all cases, Y=2.5

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Figure 11

Effect of twisted-tape length (TTP)—Nusselt number versus Reynolds number—AR=1, e∕Dh=0.0441, P∕e=10; for all cases, Y=2.5

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Figure 12

Effect of duct aspect ratio (DP)—Nusselt number versus Reynolds number—l=0.7, e∕Dh=0.0441, P∕e=20; for all cases, Y=2.5

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Figure 13

Effect of rib height (RP)—Nusselt number versus Reynolds number—l=0.9, AR=0.333, P∕e=10; for all cases, Y=2.5

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Figure 14

Effect of rib pitch (RP)—Nusselt number versus Reynolds number—l=0.9, AR=0.5, e∕Dh=0.0441; for all cases, Y=2.5

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Figure 15

Effect of space ratio (TTP)—friction versus Reynolds number—AR=1, e∕Dh=0.0441, P∕e=10; for all cases, Y=2.5

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