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RESEARCH PAPERS: Natural and Mixed Convection

Laminar Natural Convection Heat Transfer From a Vertical Baffled Plate Subjected to a Periodic Oscillation

[+] Author and Article Information
Xinrong Zhang, Hiroshi Yamaguchi

Department of Mechanical Engineering, Doshisha University, Kyoto 610-0321, Japan

Shigenao Maruyama

Institute of Fluid Science,  Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan

J. Heat Transfer 127(7), 733-739 (Feb 02, 2005) (7 pages) doi:10.1115/1.1924570 History: Received April 27, 2004; Revised February 02, 2005

The problem of laminar natural convection on a vertical baffled plate subjected to a periodic oscillation is investigated numerically. Of particular interest of this paper is the heat transfer characteristic with the oscillatory velocity being close to the flow velocity in the velocity boundary layer under nonoscillation condition. The results show that a sevenfold increase in space-time averaged Nusselt number is achieved. Three mechanisms that are responsible for the heat transfer enhancement are identified. In addition, the effects of the governing parameters on the heat transfer are studied over a wide range. The heat transfer enhancement is found to be increased with dimensionless oscillation frequency and amplitude, but decreased with the Grashof number. Another interest of this paper is to optimize the geometry of baffle plates and an optimal baffle height-spacing ratio 0.25–0.50 is found for higher heat transfer rate.

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Copyright © 2005 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic diagram of oscillating baffled plate problem

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Figure 2

Comparison of the space-time averaged Nusselt number between a stationary flat plate and an oscillatory baffled plate at a fixed velocity (U=0.95) for St=0.24, Sr=0.32 and Gr=107

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Figure 3

Evolutions of the temperature profile (θ) during one oscillation cycle for Gr=107. (a) A stationary baffle plate; (b) an oscillatory baffled plate at w0=22.0, A0=0.9, St=0.24, and Sr=0.32.

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Figure 4

A time sequence of instantaneous streamlines in the (x,y) plane for one oscillation cycle. The dimensionless oscillation frequency, amplitude, baffle height, spacing and the Grashof number are 22.0, 0.9, 0.24, 0.32 and 107, respectively. (a) t=t0 (an integer), (b) t=t0+0.2, (c) t=t0+0.4, (d) t=t0+0.6, (e) t=t0+0.8, and (f) t=t0+1.0.

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Figure 5

Variations of Nusselt number during one oscillation cycle for w0=22.0, A0=0.9, St=0.24, Sr=0.32 and Gr=107. (a) The time-averaged local Nusselt number N¯ux; (b) the space-averaged instantaneous Nusselt number N¯ut.

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Figure 6

Variations of the local instantaneous Nusselt number along the plate during one oscillation cycle for w0=22.0, A0=0.9, St=0.24, Sr=0.32 and Gr=107

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Figure 7

Variations of the space-time averaged Nusselt number with the dimensionless oscillation velocity (U=u0∕umax) for St=0.24, Sr=0.32 and Gr=107

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Figure 8

Variations of the enhancement ratio with the baffle spacing (Sr=2x0∕ℓ) for different baffle height (St=h∕πx0) for w0=22.0, A0=0.9 and Gr=107

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Figure 9

Effect of the Grashof number on the enhancement ratio for w0=22.0, A0=0.9, St=0.10 and Sr=2.0

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