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Technical Brief

Analysis of Flow and Heat Transfer Characteristics Around an Oval-Shaped Cylinder

[+] Author and Article Information
Guan-Min Zhang, Mao-Cheng Tian

School of Energy Source and Power Engineering,
Shandong University,
17923 Jingshi Road,
Jinan 250061, China

Nai-Xiang Zhou

Shandong Urban and Rural Planning and Design Institute,
9 Jiefang Road,
Jinan 250013, China

Wei Li

Department of Energy Engineering,
Zhejiang University,
866 Yuhangtang Road,
Hangzhou 310027, China
e-mail: weili96@zju.edu.cn

David Kukulka

Department of Mechanical Engineering Technology,
State University of New York College at Buffalo,
1300 Elmwood Avenue,
Buffalo, NY 14222

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received January 11, 2013; final manuscript received November 2, 2013; published online February 12, 2014. Assoc. Editor: Ali Khounsary.

J. Heat Transfer 136(4), 044502 (Feb 12, 2014) (4 pages) Paper No: HT-13-1033; doi: 10.1115/1.4026006 History: Received January 11, 2013; Revised November 02, 2013

Numerical simulations and experimental study were carried out to investigate the flow and heat transfer characteristics of air flowing across different types of oval-shaped cylinders, for Reynolds numbers varying from 4000 to 50,000. These cylinders have axis ratios, ε, of 1, 1.5, 2, 3, 4, and 5 with the major axis parallel to the free-stream. Numerical results show the closer the distance to mainstream, the smaller the local velocity gradient is. The angular position of the minimum value of Cp decreases as ε decreases and the maximum value of Cf gradually increases with ε increasing. Oval-shaped cylinders have a higher favorable pressure gradient at the front of the cylinder and a lower adverse pressure gradient at the back of the cylinder for flows in inhibiting separation. Empirical correlations for each tube have been obtained by numerical simulation relating the dimensionless heat transfer coefficient with the Reynolds Number and Prandtl Number. Based on the presented results, it can be emphasized that the average heat transfer coefficient firstly increases and then decreases by increasing the axis ratio of the tube, implying that the elliptical tubes with a suitable axis ratio possess more advantages over circular tubes. Comparisons of the numerical results with the existing data verify the validation of the present study.

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References

Figures

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Fig. 1

Cross-sections for the oval-shaped tube

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Fig. 2

Wind tunnel system: 1, air inlet; 2, pre-steady flow section; 3, anemometer; 4, test section; 5, test cylinder; 6, post-steady flow section; 7, rectangle-circular transition; 8, flexible tube; 9, draft fan; 10, micromanometer

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Fig. 3

Pressure coefficient and skin friction coefficient distribution: (a) pressure coefficient distribution; (b) Skin friction coefficient distribution

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Fig. 4

Local Nusselt number distribution for different cylinders

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Fig. 5

Variation of average Nusselt number with Reynolds number

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Fig. 6

Comparison of experimental and numerical results

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