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Research Papers: Heat Transfer Enhancement

Laminar Flow Heat Transfer and Pressure Drop in a Circular Tube Having Wire-Coil and Helical Screw-Tape Inserts

[+] Author and Article Information
Sujoy Kumar Saha

e-mail: sujoy_k_saha@hotmail.com
Mechanical Engineering Department,
Bengal Engineering and Science University,
Shibpur, Howrah 711 103, India

Contributed by the Heat Transfer Division of ASME for publication in the Journal of Heat Transfer. Manuscript received February 1, 2012; final manuscript received August 12, 2012; published online January 3, 2013. Assoc. Editor: William P. Klinzing.

J. Heat Transfer 135(2), 021901 (Jan 03, 2013) (8 pages) Paper No: HT-12-1039; doi: 10.1115/1.4007415 History: Received February 01, 2012; Revised August 12, 2012

The experimental friction factor and Nusselt number data for laminar flow through a circular duct having wire-coil and helical screw-tape inserts have been presented. Peripherally and axially local temperatures on the duct outside wall have been measured. The temperature drop across the duct wall has been calculated to obtain the duct inside wall temperatures. Peripherally averaged and axially local temperatures have been used to get axially local Nusselt numbers. These axially local Nusselt numbers have been averaged over the whole length of the duct to get the mean Nusselt number. Predictive friction factor and Nusselt number correlations developed by log-regression analysis have also been presented. Nusselt number correlation takes care of the thermal development length represented by the Graetz number, swirl and inertia force due to forced convection at large Reynolds number, buoyancy force due to natural convection at low Reynolds number represented by Rayleigh number and the geometrical parameters of wire-coil and helical screw-tape inserts. The thermohydraulic performance has been evaluated. The helical screw-tape inserts in combination with wire-coil inserts perform better than the individual enhancement technique acting alone for laminar flow through a circular tube up to a certain value of fin parameter.

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Figures

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Fig. 1

Circular duct having wire coil insert

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Fig. 2

Layout of a circular duct with full-length fin insert (a) helical screw-tape and (b) twisted-tape

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Fig. 3

Schematic diagram of the experimental rig

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Fig. 4

Validation of the experimental setup: comparison of present experimental plain circular tube friction factor data with plain circular tube correlation

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Fig. 5

Validation of the experimental setup: comparison of present experimental plain circular tube Nusselt number data with plain circular tube correlation

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Fig. 6

Effect of helical screw-tape parameter on friction factor—coil helix angle = 60 deg, d/Dh = 0.07692

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Fig. 7

Effect of coil helix angle on friction factor p = 0.31, d/Dh = 0.1026

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Fig. 8

Effect of coil wire diameter on friction factor—coil helix angle = 30 deg, p = 0.25

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Fig. 9

Comparison of present experimental friction factor data with the experimental friction factor data, Eq. (4), d/Dh = 0.07692 [4]

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Fig. 10

Effect of helical screw-tape parameter on Nusselt number—coil helix angle = 60 deg, d/Dh = 0.1026

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Fig. 11

Effect of coil helix angle on Nusselt number p = 0.31, d/Dh = 0.07692

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Fig. 12

Effect of coil wire diameter on Nusselt number—coil helix angle = 60 deg, p = 0.25

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Fig. 13

Comparison of present experimental Nusselt number data with the experimental Nusselt number data, Eq. (3), d/Dh = 0.07692 [4]

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