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Research Papers: Heat Exchangers

Computational Fluid Dynamics and Heat Transfer Analysis for a Novel Heat Exchanger

[+] Author and Article Information
Haolin Ma

Department of Mechanical Engineering and Mechanics,
Lehigh University,
Packard Lab #356,
Bethlehem, PA 18015
e-mail: ham310@lehigh.edu

Dennis E. Oztekin

Mem. ASME
Department of Mechanical Engineering and Mechanics,
Lehigh University,
Packard Lab #356,
Bethlehem, PA 18015
e-mail: deo308@lehigh.edu

Seyfettin Bayraktar

Department of Naval Architecture
and Marine Engineering,
Yildiz Technical University,
Besiktas-Istanbul 34349, Turkey
e-mail: sbay@yildiz.edu.tr

Sedat Yayla

Department of Mechanical Engineering,
Yuzuncu Yil University,
Van 65080,Turkey
e-mail: syayla@yyu.edu.tr

Alparslan Oztekin

Mem. ASME
Department of Mechanical Engineering and Mechanics,
Lehigh University,
Packard Lab #356,
Bethlehem, PA 18015
e-mail: alo2@lehigh.edu

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received June 19, 2014; final manuscript received February 1, 2015; published online March 3, 2015. Assoc. Editor: Danesh / D. K. Tafti.

J. Heat Transfer 137(5), 051801 (May 01, 2015) (11 pages) Paper No: HT-14-1418; doi: 10.1115/1.4029764 History: Received June 19, 2014; Revised February 01, 2015; Online March 03, 2015

Computational fluid dynamics (CFD) and heat transfer simulations are conducted for a novel heat exchanger. The heat exchanger consists of semi-circle cross-sectioned tubes that create narrow slots oriented in the streamwise direction. Numerical simulations are conducted for Reynolds numbers (Re) ranging from 700 to 30,000. Three-dimensional turbulent flows and heat transfer characteristics in the tube bank region are modeled by the k-ε Reynolds-averaged Navier–Stokes (RANS) method. The flow structure predicted by the two-dimensional and three-dimensional simulations is compared against that observed by the particle image velocimetry (PIV) for Re of 1500 and 4000. The adequate agreement between the predicted and observed flow characteristics validates the numerical method and the turbulent model employed here. The three-dimensional and the two-dimensional steady flow simulations are compared to determine the effects of the wall on the flow structure. The wall influences the spatial structure of the vortices formed in the wake of the tubes and near the exit of the slots. The heat transfer coefficient of the slotted tubes improved by more than 40% compare to the traditional nonslotted tubes.

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References

Figures

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Fig. 1

Schematic of the test section of the slotted tube bank. It consists of seven columns and seven rows in a staggered arrangement.

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Fig. 2

Three-dimensional computational domain. It includes a tube bank of seven rows and five columns in a staggered arrangement. x is measured from the inlet, y is measured from the mid-plane, and z is measured from the front plate.

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Fig. 3

Mesh structure for: (a) a full computational domain, (b) near the tube bank, (c) at the interface, and (d) in the exit region. The mesh includes 4 × 106-elements. The flow is from left to right.

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Fig. 4

Velocity profile in the y-direction at x = 437.6 mm and z = 10 mm for Re = 1500 using three different mesh levels

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Fig. 5

Stream function for Re = 1500 (left column) and 4000 (right column) predicted by: (a) a two-dimensional simulation, (b) by a three-dimensional simulation, and (c) measured by PIV experiments

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Fig. 6

Vorticity contours (first row), normalized streamwise velocity [u/U] (second row), spanwise velocity [v/U] (third row), and normalized TKE (fourth row) for Re = 4000. Contours on the left column denote results predicted by the three-dimensional simulations while the contours on the right column denote results obtained by experiments.

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Fig. 7

Stream function for Re = 1500 at planes: (a) z = 1 mm, (b) z = 8 mm, and (c) z = 10 mm

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Fig. 8

Isotherms (first row), streamlines (second row), and vorticity field (third row) for Re = 4000. Contours at the left column denote results obtained for the nonslotted tube design and the contours at the right denote results for the slotted tube design.

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Fig. 9

Contours of the local heat transfer coefficient for the slotted and the nonslotted tubes at Re = 4000. (a) Upstream view, (b) downstream view, and (c) slot surface of the tube located at the second row and the second column. The bottom surface in (c) is the mid-plane and the top surface is the wall.

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