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Research Papers: Heat Transfer Enhancement

Tapered Twisted Tape Inserts for Enhanced Heat Transfer

[+] Author and Article Information
B. V. N. Ramakumar

Honeywell Technology Solutions,
Bangalore 560103, India
e-mail: Ramakumar.bommisetty@honeywell.com

J. D. Arsha

Honeywell Technology Solutions,
Bangalore 560103, India
e-mail: Arsha.JD@honeywell.com

Praveen Tayal

Honeywell Technology Solutions,
Hyderabad 500032, India
e-mail: Praveen.Tayal@Honeywell.com

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received August 21, 2014; final manuscript received July 28, 2015; published online August 25, 2015. Assoc. Editor: Sujoy Kumar Saha.

J. Heat Transfer 138(1), 011901 (Aug 25, 2015) (9 pages) Paper No: HT-14-1554; doi: 10.1115/1.4031207 History: Received August 21, 2014; Revised July 28, 2015

Insertion of twisted tapes in smooth channels is one of the passive methods used for enhancing heat transfer. Flow and associated heat transfer characteristics of these channels are very complex. Understanding this complex flow is helpful while designing new passive methods. Numerical methods like computational fluid dynamics (CFD) are gaining much popularity for analyzing and designing these heat transfer enhancement techniques. This paper focuses on such a numerical study. The preliminary study is focused on development of numerical methodology through validation. Successive studies are aimed at development of an innovative design for twisted tape. Twisted tapes with taper angle (tapered twisted tapes, i.e., tape width decreases along the flow direction) are developed and evaluated on the basis of the performance of these tapes with those of conventional tapes. A circular tube with tapered twisted tape with a twist ratio of 3 and taper angles of 0.3, 0.4, 0.5, 0.6, and 0.7 is considered for this study along with a plain tube. Three Reynolds numbers (Re) of 8545, 11393, and 13333 are considered to examine the sensitivity of the performance. Simulations are performed with a commercially available CFD tool, ansys fluent (v14.0). Heat transfer and pressure drop results are presented in the form of Nusselt number (Nu), friction factor (f), and overall enhancement ratio (η). An increase of 17% in overall enhancement is predicted with taper angle of 0.5.

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Figures

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Fig. 1

Computational model: (a) 3D view of classic twisted tape, (b) twisted tape terminology, and (c) meshed geometry

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Fig. 2

Details of configurations: (a) tapered twisted tape inserts and (b) taper angle

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Fig. 3

Variation of velocity along the flow direction

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Fig. 4

Velocity contour at different vertical planes

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Fig. 5

Variation of pressure along the flow direction

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Fig. 6

Variation of turbulent intensity along the flow direction

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Fig. 7

Effect of Reynolds number on the friction factor

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Fig. 8

Effect of taper angle on the friction factor

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Fig. 9

Effect of Reynolds number on the Nusselt number

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Fig. 10

Effect of taper angle on the Nusselt number

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Fig. 11

Effect of Reynolds number on the overall performance ratio

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Fig. 12

Effect of taper angle on the overall performance ratio

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