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Research Papers: Jets, Wakes, and Impingement Cooling

Mixed Convection in an Impinging Laminar Single Square Jet

[+] Author and Article Information
L. B. Y. Aldabbagh1

Department of Mechanical Engineering, Eastern Mediterranean University, Magosa, Mersin 10, Turkeyloay.aldabagh@emu.edu.tr

Department of Mechanical Engineering, Schulich School of Engineering, The University of Calgary, Calgary, AB, T2N 1N4, Canada

1

Corresponding author.

J. Heat Transfer 131(2), 022201 (Dec 29, 2008) (7 pages) doi:10.1115/1.3000970 History: Received April 04, 2008; Revised July 24, 2008; Published December 29, 2008

Abstract

The effect of Richardson number $(Ri=Gr/Re2=Ra/Pr Re2)$ in a confined impinging laminar square jet was investigated numerically through the solution of Navier–Stokes and energy equations. The simulations were carried out for Richardson number between 0.05 and 8 and for jet Reynolds number between 50 and 300. The jet-to-target spacings were fixed to $0.25B$, $0.5B$, and $1.0B$, respectively, where $B$ is the jet width. The calculation results show that for the jet-to-target spacing of $0.25B$, the flow structure of a square single jet impinging on a heated plate is not affected by the Richardson number. For such very small jet-to-target distances the jet is merely diverted in the transverse direction. The wall jet fills the whole gap between the plates with a very small vortex motion formed near the corners of the jet cross section close to the upper plate. In addition, the effect of the Richardson number on the variation in the local Nusselt number is found to be not significant. For higher jet-to-target spacing, the Nusselt number increased as the Richardson number increased for the same Re. In addition, the heat transfer rate increased as the jet Reynolds number increased for the same Richardson number.

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Figures

Figure 1

Definition of geometric parameters and the coordinate system

Figure 2

Projection of flow lines on the mid-x-z plane for Re=200 and Az=1.0 and for Richardson numbers of (a) Ri=0.05, (b) Ri=1.0, and (c) Ri=1.5

Figure 3

Projection of flow lines for Re=200, Az=1.0, and Ri=0.05 on the horizontal cross section at (a) Z=0.9 and (b) Z=0.3

Figure 4

Projection of flow lines on the mid-x-z plane for Az=1.0, Ri=1.0, and (a) Re=100, (b) Re=150, and (c) Re=300

Figure 5

Projection of flow lines on the mid-x-z plane for Re=200 and Az=0.5 and for Richardson numbers of (a) Ri=0.05, (b) Ri=1.0, and (c) Ri=8.0

Figure 6

Projection of flow lines for Re=200 and Ri=0.05 on the horizontal cross section at (a) Z=0.225 and (b) Z=0.175

Figure 7

Projection of flow lines on the x-z plane for (a) Re=200 and Ri=0.05 at Y=18, (b) Re=200 and Ri=0.05 at Y=17.5, (c) Re=200 and Ri=8.0 at Y=17.5, and (d) Re=50 and Ri=1 at Y=17.5

Figure 8

Variation in the W-velocity with X at Y=17.5 for Re=200 and at jet-to-target spacings of (a) Az=0.25 and Z=0.075, (b) Az=0.5 and Z=0.15, and (c) Az=1.0 and Z=0.3

Figure 9

Effect of Ri on the variation in the local Nusselt number for Re=200 at jet-to-target spacings of (a) Az=0.25, (b) Az=0.5, and (c) Az=1.0

Figure 10

Effect of Re on the variation in the local Nusselt number for Ri=1 at jet-to-target spacings of (a) Az=0.25, (b) Az=0.5, and (c) Az=1.0

Figure 11

Effect of jet-to-target spacing on the variation in the local Nusselt number for Richardson numbers of (a) Ri=0.05, (b) Ri=1.0, and (c) Ri=1.5

Figure 12

The three-dimensional plot of the Nusselt number for Re=200, Az=0.5, and Ri=8

Figure 13

The contour plots of the temperature distribution for Re=200, Az=0.5, and Ri=8 on horizontal cross section Z=0.15

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