Research Papers: Heat Transfer Enhancement

Numerical Analysis of Flow Structure and Heat Transfer Characteristics in Dimpled Channels With Secondary Protrusions

[+] Author and Article Information
Yonghui Xie

School of Energy and Power Engineering,
Xi’an Jiaotong University,
Xi’an, Shaanxi 710049, China
e-mail: yhxie@mail.xjtu.edu.cn

Zhongyang Shen

School of Energy and Power Engineering,
Xi’an Jiaotong University,
Xi’an, Shaanxi 710049, China
e-mail: szy_xjtu@163.com

Di Zhang

Key Laboratory of Thermo-Fluid
Science and Engineering,
Ministry of Education,
School of Energy and Power Engineering,
Xi’an Jiaotong University,
Xi’an, Shaanxi 710049, China
e-mail: zhang_di@mail.xjtu.edu.cn

Phillip Ligrani

Department of Mechanical
and Aerospace Engineering,
University of Alabama in Huntsville,
Huntsville, AL 35899
e-mail: phillip.ligrani@uah.edu

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received January 10, 2014; final manuscript received October 12, 2015; published online November 11, 2015. Assoc. Editor: Keith Hollingsworth.

J. Heat Transfer 138(3), 031901 (Nov 11, 2015) (6 pages) Paper No: HT-14-1014; doi: 10.1115/1.4031787 History: Received January 10, 2014; Revised October 12, 2015

Dimple structure is an effective heat transfer augmentation approach on coolant channel due to its advantage on pressure penalty. The implication of secondary protrusion, which indicates protrusion with smaller dimension than dimple, will intensify the Nusselt number Nu inside dimple cavity without obvious extra pressure penalty. The objective of this study is to numerically analyze the combination effect of dimples and secondary protrusion. Different protrusion–dimple configurations including protrusion print-diameter Dp, protrusion–dimple gap P, and staggered angle α are investigated. From the results, it is concluded that the implication of secondary protrusion will considerably increase the heat transfer rates inside dimple cavity. Cases 4 and 6 possess the highest Nusselt number enhancement ratio Nu/Nu0 reaching up to 2.1–2.2. The additional pressure penalty brought by the protrusion is within 15% resulting in total friction ratio f/f0 among the range of 1.9–2.1. Dimpled channels with secondary protrusions possess higher thermal performance factor TP, defined as (Nu/Nu0)/(f/f0)1/3, among which cases 4 and 6 are the optimal structures. Besides this, the TP of protrusion–dimple channels are comparable to the other typical heat transfer devices, and higher TP can be speculated after a more optimal dimple shape or combination with ribs and fins.

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Fig. 5

Typical flow patterns of protrusion–dimpled channel: (a) flow insight and special region, (b) streamlines in zone 1, and (c) streamlines in zone 2

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Fig. 4

Comparison of the calculated results with different turbulence model: (a) Nu versus Re and (b) f/f0 versus Re

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Fig. 3

Schematics of mesh details: (a) inline arrangement and (b) staggered arrangement

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Fig. 2

Detailed descriptions of channel dimensions

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Fig. 1

A schematic diagram of the investigated rectangular channel

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Fig. 6

Streamlines and velocity contours above the protrusion and dimple surfaces: (a) case 1, (b) case 3, (c) case 4, and (d)case 8

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Fig. 7

Local Nusselt number ratio for (a) case 1, (b) case 4, (c) case 3, and (d) case 8

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Fig. 8

Average Nu/Nu0 profiles for all cases (Nu0 indicates the baseline Nusselt number by the equation)

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Fig. 9

Average f/f0 profiles for all cases (f0 indicates the baseline friction coefficient by the equation)

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Fig. 10

Thermal performances of representative cases in the present study and other typical heat transfer devices




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