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RESEARCH PAPERS: Forced Convection

Heat Transfer and Pressure Drop Characteristics of Laminar Flow in Rectangular and Square Plain Ducts and Ducts With Twisted-Tape Inserts

[+] Author and Article Information
S. K. Saha1

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

D. N. Mallick

Applied Mechanics and Drawing Department,  Bengal Engineering and Science University, Shibpur Howrah 711 103, West Bengal, Indiadnmbec@mailcity.com

1

Corresponding author.

J. Heat Transfer 127(9), 966-977 (Nov 21, 2004) (12 pages) doi:10.1115/1.2010493 History: Received June 11, 2004; Revised November 21, 2004

The present paper reports the results of an experimental investigation of the heat transfer and pressure drop characteristics of laminar flow of viscous oil through horizontal rectangular and square plain ducts and ducts inserted with full-length twisted tapes, short-length twisted tapes, and regularly spaced twisted-tape elements. Isothermal pressure drop measurements were taken in acrylic ducts. Heat transfer measurements were taken in electrically heated stainless-steel ducts imposing uniform wall heat flux boundary conditions. The duct aspect ratios AR were 1, 0.5, and 0.333. The twist ratios of the twisted tapes were y=2.692, 5.385, 2.597, 5.193, 2.308, and 4.615. Short-length tapes were 0.9, 0.7, and 0.5 times the duct length. The space ratios were s=2.692, 5.385, 2.597, 5.193, 2.308, and 4.615. Both friction factor and Nusselt number increase with decreasing y and AR for AR1 and increasing Re, Sw, and Pr. As the tape-length decreases, both friction factor and Nusselt number decrease. Friction factor increases as s decreases, and Nusselt number increases as s increases. Isothermal friction factor correlation and comprehensive Nusselt number correlation have been developed to predict data reasonably well in the entire range of parameters. Performance evaluation says that short-length twisted tapes are worse and regularly spaced twisted-tape elements are better than the full-length twisted tapes.

Copyright © 2005 by American Society of Mechanical Engineers
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Figures

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Figure 1

(a) Full-length twisted-tape insert inside a duct and (b) regularly spaced twisted-tape elements

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Figure 2

Schematic diagram of the experimental setup

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Figure 3

Heat transfer test section

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Figure 4

Comparison of present experimental plain circular duct data with Bandyopadhyay (5)

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Figure 5

(fRe)sw versus Sw—l=1, AR=1

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Figure 6

(fRe)sw versus Sw—l=0.5, AR=0.333

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Figure 7

(fRe)sw versus Sw—AR=1, y=2.692

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Figure 8

(fRe)sw versus Sw—AR=0.333, y=4.615

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Figure 9

(fRe)sw versus Sw—y=2.532, l=1

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Figure 10

(fRe)sw versus Sw—y=5.064, l=0.5

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Figure 11

Num[(μb∕μw)−0.14]∕5.172 versus (Sw.Pr)0.565, l=1, AR=1

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Figure 12

Num[(μb∕μw)−0.14]∕5.172 versus (Sw.Pr)0.565, l=0.5, AR=0.333

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Figure 13

Num[(μb∕μw)−0.14]∕5.172 versus (Sw.Pr)0.565, AR=1, y=2.692

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Figure 14

Num[(μb∕μw)−0.14]∕5.172 versus (Sw.Pr)0.565), AR=0.333, y=4.615

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Figure 15

Num[(μb∕μw)−0.14]∕5.172 versus (Sw.Pr)0.565, y=2.532, l=1

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Figure 16

Num[(μb∕μw)−0.14]∕5.172 versus (Sw.Pr)0.565, y=5.064, l=0.5

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Figure 17

(fRe)sw versus Sw—y=2.532, s=2.532

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Figure 18

(fRe)sw versus Sw—s=4.615, AR=0.333

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Figure 19

(fRe)sw versus Sw—y=4.615, AR=0.333

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Figure 20

Num[(μb∕μw)−0.14]∕5.172 versus (Sw.Pr)0.565, y=2.532, s=2.532

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Figure 21

Num[(μb∕μw)−0.14]∕5.172 versus (Sw.Pr)0.565, s=4.615, AR=0.333

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Figure 22

Num[(μb∕μw)−0.14]∕5.172 versus (Sw.Pr)0.565, y=4.615, AR=0.333

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Figure 23

Comparison of present experimental data with the predictions of Eq. 2 for short-length twisted tape

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Figure 24

Comparison of present experimental data with the predictions of Eq. 5 for short-length twisted tape

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Figure 25

Comparison of present experimental data with the predictions of Eq. 3 for regularly spaced twisted-tape elements

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Figure 26

Comparison of present experimental data with the predictions of Eq. 6 for regularly spaced twisted-tape elements

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