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Research Papers: Forced Convection

Heat Transfer Characteristics of an Inclined Impinging Jet on a Curved Surface in Crossflow

[+] Author and Article Information
X. L. Wang

State Key Laboratory for Mechanical Structure
Strength and Vibration,
Xi'an Jiaotong University,
Xi'an 710049, China
e-mail: wanglong12346@163.com

H. B. Yan

School of Energy and Power Engineering,
Xi'an Jiaotong University,
Xi'an 710049, China
e-mail: hongbin.1988@stu.xjtu.edu.cn

T. J. Lu

State Key Laboratory for Mechanical Structure
Strength and Vibration,
Xi'an Jiaotong University,
Xi'an 710049, China
e-mail: tjlu@mail.xjtu.edu.cn

S. J. Song

School of Mechanical
and Aerospace Engineering,
Seoul National University,
Seoul 151-742, South Korea
e-mail: sjsong@snu.ac.kr

T. Kim

School of Mechanical Engineering,
University of the Witwatersrand,
Johannesburg 2050, South Africa
e-mail: tong.kim@wits.ac.za

1Corresponding authors.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received October 3, 2013; final manuscript received April 2, 2014; published online April 23, 2014. Assoc. Editor: Giulio Lorenzini.

J. Heat Transfer 136(8), 081702 (Apr 23, 2014) (10 pages) Paper No: HT-13-1526; doi: 10.1115/1.4027389 History: Received October 03, 2013; Revised April 02, 2014

This study reports on heat transfer characteristics on a curved surface subject to an inclined circular impinging jet whose impinging angle varies from a normal position θ = 0 deg to θ = 45 deg at a fixed jet Reynolds number of Rej = 20,000. Three curved surfaces having a diameter ratio (D/Dj) of 5.0, 10.0, and infinity (i.e., a flat plate) were selected, each positioned systematically inside and outside the potential core of jet flow where Dj is the circular jet diameter. Present results clarify similar and dissimilar local heat transfer characteristics on a target surface due to the convexity. The role of the potential core is identified to cause the transitional response of the stagnation heat transfer to the inclination of the circular jet. The inclination and convexity are demonstrated to thicken the boundary layer, reducing the local heat transfer (second peaks) as opposed to the enhanced local heat transfer on a flat plate resulting from the increased local Reynolds number.

Copyright © 2014 by ASME
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References

Figures

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Fig. 1

Schematic summary illustrating how the inclination of a single jet affects lateral heat transfer distribution on a flat plate [6-11]; (a) for a “small” impinging distance; (b) for a “large” impinging distance

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Fig. 2

Schematic of an inclined circular jet impinging on curved surfaces e.g., circular cylinders where a flat plate has an infinite radius

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Fig. 3

Schematics of (a) test setup for measuring heat transfer distribution along the circumference of a heated circular cylinder cooled by an inclined jet; (b) a crossflow plane

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Fig. 4

Free jet characteristics of a circular jet at Rej = 20,000; (a) radial profiles of axial velocity at selected downstream transverse planes; (b) variation of normalized centerline velocity along the jet axis (i.e., the z-axis), indicating a potential core persisting up to z/Dj = 4.0

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Fig. 5

Comparison of lateral heat transfer distributions on a flat plate subject to a normal impinging jet to the data reported by Goldstein and Franchett [16] and Lee et al. [35]

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Fig. 6

Lateral heat transfer distribution on a flat plate subject to an inclined jet at Rej = 20,000 with four selected inclination angles with the potential core persisting up to z/Dj = 4.0; (a) z/Dj = 2.0 (inside potential core); (b) z/Dj = 4.0 (at potential core tip); (c) z/Dj = 5.0 (slightly outside potential core; (d) z/Dj = 8.0 (outside potential core)

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Fig. 7

Velocity profiles measured at selected lateral locations on the downhill side positioned at z/Dj = 2.0

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Fig. 8

Circumferential distribution of (a) heat transfer and (b) static pressure on a target cylinder (D/Dj = 5.0) positioned inside the potential core at Rej = 20,000

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Fig. 9

Velocity profiles measured at selected azimuth angles in the downhill side at z/Dj = 2.0

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Fig. 10

Circumferential distribution of heat transfer on a target cylinder (D/Dj = 5.0) positioned outside the potential core at Rej = 20,000

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Fig. 11

Lateral heat transfer distribution on curved surfaces subject to an inclined impinging jet at z/Dj = 2.0 and Rej = 20,000: (a) θ = 0 deg and (b) θ = 45 deg

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Fig. 12

Velocity profiles measured at s/Dj = 4.0 (denoted as (III) in Fig. 10(b)) on two cylinders and a flat plate positioned at z/Dj = 2.0 (denoted as (III) in Fig. 10(b))

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Fig. 13

Lateral heat transfer distribution on curved surfaces subject to an inclined impinging jet at z/Dj = 8.0 and Rej = 20,000; (a) θ = 0 deg; (b) θ = 45 deg (location (IV) in Fig. 12)

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Fig. 14

Velocity profiles measured at s/Dj = 4.0 (denoted as (IV) in Fig. 12(b)) on two cylinders and a flat plate positioned at z/Dj = 8.0 (outside potential core)

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Fig. 15

Schematic summary illustrating how the inclination of a single circular jet affects azimuthal heat transfer distributions on a curved surface: (a) inside the potential core; (b) outside the potential core

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