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Research Papers: Heat Transfer Enhancement

Three-Dimensional Numerical Study of Flow and Heat Transfer Enhancement Using Vortex Generators in Fin-and-Tube Heat Exchangers

[+] Author and Article Information
P. Chu, W. Q. Tao

State Key Laboratory of Multiphase Flow in Power Engineering, School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an, Shaan xi 710049, China

Y. L. He

State Key Laboratory of Multiphase Flow in Power Engineering, School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an, Shaan xi 710049, Chinayalinghe@mail.xjtu.edu.cn

J. Heat Transfer 131(9), 091903 (Jun 25, 2009) (9 pages) doi:10.1115/1.3139185 History: Received September 09, 2008; Revised March 02, 2009; Published June 25, 2009

In this paper, a three-dimensional numerical investigation was performed for heat transfer characteristics and flow structure of full scale fin-and-tube heat exchangers with rectangular winglet pair (RWP). For the Reynolds number ranging from 500 to 880, the baseline configuration (without RWP) is compared with three enhanced configurations (with RWP): inline-1RWP case, inline-3RWP case, and inline-7RWP case. It was found that the air-side heat transfer coefficient improved by 28.1–43.9%, 71.3–87.6%, and 98.9–131% for the three enhanced configurations, with an associated pressure drop penalty increase of 11.3–25.1%, 54.4–72%, and 88.8–121.4%, respectively. An overall performance comparison was conducted by using the London area goodness factor. It is revealed that among the three enhanced configurations, the inline-1RWP case obtains the best overall performance, and the inline-3RWP case is better than the inline-7RWP case. The numerical results were also analyzed on the basis of the field synergy principle to provide fundamental understanding of the relation between local flow structure and heat transfer augmentation. It was confirmed that the reduction in the average intersection angle between the velocity vector and the temperature gradient was one of the essential factors influencing heat transfer enhancement. The analysis also provides guidelines for where the enhancement technique is highly needed.

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Copyright © 2009 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Schematic of the core region of a fin-and-tube heat exchanger with RWPs

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Figure 2

Four basic vortex generator forms

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Figure 3

Winglet type vortex generator dimensions and the placement with respect to the tube

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Figure 4

Coordinate system and computational domain

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Figure 5

Experimental numerical comparison of hair and ΔP for model validation

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Figure 6

Different configurations for fin-and-tube heat exchangers with and without RWPs

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Figure 7

Local velocity distributions on the middle cross section for the baseline case and the inline-3RWP case at Re=850

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Figure 8

Local temperature distributions on the middle cross section for the baseline case and the inline-3RWP case at Re=850

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Figure 9

Longitudinal distributions of line-weighted average Nusselt number on the RWP-mounted fins for the baseline case and three enhanced cases at Re=850

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Figure 10

Variations in the air-side heat transfer coefficient hair and the pressure drop ΔP versus the Re number

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Figure 11

Different configurations for fin-and-tube heat exchangers with staggered arrangement

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Figure 12

Variations in the air-side heat transfer coefficient hair, the pressure drop ΔP, and the overall performance j/f versus the Re number

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Figure 13

The average intersection angles for baseline configuration and enhanced configurations

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Figure 14

Distributions of isothermals and streamlines for baseline case and enhanced cases

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