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Research Papers: Heat Transfer Enhancement

Heat Transfer Characteristics of Baffled Channel Flow

[+] Author and Article Information
Changwoo Kang

Department of Mechanical Engineering,  Inha University, Incheon 402-751, Koreaksyang@inha.ac.kr

Kyung-Soo Yang1

Department of Mechanical Engineering,  Inha University, Incheon 402-751, Koreaksyang@inha.ac.kr

1

Corresponding author.

J. Heat Transfer 133(9), 091901 (Jul 07, 2011) (6 pages) doi:10.1115/1.4003829 History: Revised March 10, 2010; Received November 06, 2010; Published July 07, 2011; Online July 07, 2011

Heat transfer characteristics of baffled channel flow, where thin baffles are mounted on both channel walls periodically in the direction of the main flow, have been numerically investigated in a laminar range. The main objectives of the present study are to find the physical reason responsible for the heat transfer enhancement in finned heat exchangers, and to identify the optimal configurations of the baffles to achieve the most efficient heat removal from the channel walls. Two key parameters are considered, namely ratio of baffle interval to channel height (RB ) and Reynolds number (Re). We performed a parametric study and found that the large-scale vortices travelling along the channel walls between the neighboring baffles, which are generated by flow separation at the tips of the baffles and become unsteady due to a Hopf bifurcation from steady to a time-periodic flow, play the key role in the heat transfer enhancement by inducing strong vertical velocity fluctuation in the vicinity of the channel walls. We also propose a contour diagram (“map”) of averaged Nusselt number on the channel walls as a function of the two parameters. The results shed light on understanding and controlling heat transfer mechanism in a finned heat exchanger, being quite beneficial to its design.

Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Flow configuration

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Figure 2

Grid system; thin baffles of zero thickness are mounted on both walls in the middle of the computational domain

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Figure 3

Streamlines of steady flow for RB  = 1.456

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Figure 4

Vcl versus time for RB  = 1.456, Re = 130

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Figure 5

Instability growth rate versus Re for RB  = 1.456

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Figure 6

Temperature distribution for Re = 100, Pr = 0.71

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Figure 7

Streamlines during one period for RB  = 1.0, Re = 280

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Figure 8

Temperature contours during one period for RB  = 1.0, Re = 280, Pr = 0.71

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Figure 9

Streamlines during one period for RB  = 3.0, Re = 130

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Figure 10

Temperature contours during one period for RB  = 3.0, Re = 130, Pr = 0.71

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Figure 11

Average Nusselt number and critical Reynolds number versus RB , Re = 130

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Figure 12

Distribution of v'rms along the channel wall; Re = 130, y/H = 0.1

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Figure 13

Average Nusselt number versus Re

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Figure 14

Contours of 〈Nu−〉. The actual cases computed are represented by the dots.

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Figure 15

Contours of 〈Nu−〉-Nuo. The actual cases computed are represented by the dots.

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