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Research Papers

Numerical Investigation of Heat Transfer Enhancement Using Hybrid Vortex Generator Arrays in Fin-and-Tube Heat Exchangers

[+] Author and Article Information
Shubham Agarwal

Department of Mechanical Engineering,
Birla Institute of Technology,
Mesra,
Ranchi 835215, India
e-mail: Shubham10507.12@bitmesra.ac.in

R. P. Sharma

Professor
Department of Mechanical Engineering,
Birla Institute of Technology,
Mesra,
Ranchi 835215, India

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF THERMAL SCIENCE AND ENGINEERING APPLICATIONS. Manuscript received October 22, 2015; final manuscript received February 28, 2016; published online April 19, 2016. Assoc. Editor: Amir Jokar.

J. Thermal Sci. Eng. Appl 8(3), 031007 (Apr 19, 2016) (9 pages) Paper No: TSEA-15-1302; doi: 10.1115/1.4033213 History: Received October 22, 2015; Revised February 28, 2016

This is a novel study for assessing the heat transfer enhancement in a multi-row inline-tube heat exchanger using hybrid vortex generator (VG) arrays, i.e., rectangular winglet pairs (RWPs) with different geometrical configurations installed in coherence for enhanced heat transfer. The three-dimensional numerical study uses a full scale seven-tube inline heat exchanger model. The effect of roll of rectangular winglet VG on heat transfer enhancement is analyzed and optimized roll angle is determined for maximum heat transfer enhancement. Four different configurations are analyzed and compared in this regard: (a) single RWP (no roll); (b) 3RWP-inline array(alternating tube row with no roll of VGs); (c) single RWP (with optimized roll angle VGs); and (d) 3RWP-inline array(alternating tube row with all VGs having optimized roll angle). It was found that the inward roll of VGs increased the heat transfer from the immediately downstream tube but reduced heat transfer enhancement capability of other VG pairs downstream. Further, four different hybrid configurations of VGs were analyzed and the optimum configuration was obtained. For the optimized hybrid configuration at Re = 670, RWP with optimized roll angle increased heat transfer by 17.5% from the tube it was installed on and by 42% from the immediately downstream tube. Increase in j/ƒ of 36.7% is obtained by use of hybrid VGs in the optimized hybrid configuration. The deductions from the current study are supposed to well enhance the performance of heat exchangers with different design configurations.

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References

Figures

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Fig. 1

Schematic of core region of seven-tube inline heat exchanger model with 3RWPs

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Fig. 2

(a) Computational domain with 1RWP at leading tube, (b) and (c) VG placement with respect to the tube, and (d) effect of roll angle on VG orientation

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Fig. 3

Numerical and experimental comparison of (a) pressure drop and (b) overall heat transfer coefficient

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Fig. 4

Baseline and RWP enhanced configurations (with and without roll): (a) baseline, (b) 1RWP pair leading edge, and (c) 3RWP on alternate tube

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Fig. 5

Area-averaged heat flux with varying VG roll angle for (a) tube1 and (b) tube2

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Fig. 6

Area-averaged total tube surface heat flux for baseline and VG enhanced configurations with and without VG roll at inlet face velocity of 1.4 ms−1

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Fig. 7

Pressure drop across the heat exchanger in baseline and VG enhanced configurations

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Fig. 8

Numerically generated pathlines for winglet enhanced configurations: (a) 3RWP (without roll), (b) 3RWP (with roll), and (c) zoom in view to visualize the flow swirl

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Fig. 9

Local velocity distributions on midplane for (a) 3RWP (without roll) and (b) 3RWP (with roll) configurations

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Fig. 10

Local temperature distributions on midplane for (a) baseline, (b) 3RWP (without roll), and (c) 3RWP (with roll) configurations

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Fig. 11

Various hybrid configurations with ORWP and BRWP pairs

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Fig. 12

Area-averaged tube surface heat flux in hybrid and baseline configurations

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Fig. 13

Span-averaged tube surface heat flux along tube circumference in baseline and VG enhanced configurations

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Fig. 14

(a) Variation in overall heat transfer coefficient in various configurations versus Re and (b) overall performance j/ƒ versus Re

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