Turbulent free convection in a vertical converging channel
By:Badr, HM (Badr, H. M.)[ 1 ]; Habib, MA (Habib, M. A.)[ 1 ]; Ben-Mansour, R (Ben-Mansour,
R.)[ 1 ]; Said, SAM (Said, S. A. M.)[ 1 ]; Ayinde, TF (Ayinde, T. F.)[ 1 ]; Anwar, S (Anwar, S.)[ 1 ]
HEAT AND MASS TRANSFER
Volume: 47
Issue: 11
Pages: 1427-1443
DOI: 10.1007/s00231-011-0809-5
Published: NOV 2011
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Abstract
This paper presents the results of experimental and numerical investigations of the
problem of turbulent natural convection in a converging-plate vertical channel. The
channel has two isothermally heated inclined walls and two adiabatic vertical side walls.
The parameters involved in this study are the channel geometry represented by the
channel width at exit, the inclination of the heated walls and the temperature difference
between the heated walls and the ambient. The investigation covered modified Rayleigh
numbers up to 10(8) in the computational study and up to 9.3 x 10(6) in the experimental
work. The experimental measurements focused on the velocity field and were carried out
using a PIV system and included measurements of the mean velocity profiles as well as the
root-mean-square velocity and shear stress profiles. The experiments were conducted for
an inclination angle of 30 degrees, a gap width of 10 mm and two temperature differences
(Delta T = 25.4 degrees C and 49.8 degrees C). The velocity profiles in the lower part of the
channel indicated the presence of two distinct layers. The first layer is adjacent to the
heated plate and driven by buoyancy forces while the second layer extends from the point
of maximum velocity to the channel center plane and driven mainly by shear forces. The
velocity profile at the upper portion of the channel has shown the merging of the two
boundary layers growing over the two heated walls. The measured values of the Reynolds
shear stress and root mean square of the horizontal and vertical velocity fluctuation
components have reached their maximum near the wall while having smaller values in the
core region. The computational results have shown that the average Nusselt number
increases approximately linearly with the increase of the modified Rayleigh number when
plotted on log-log scale. The variation of the local Nusselt number indicated infinite values
at the channel inlet (leading edge effect) and high values at the channel exit (trailing edge
effect). For a fixed value of the top channel opening, the increase of the inclination angle
tended to reduce flow velocity at the inlet section while changing the flow structure near
the heated plates in such a way to create boundary-layer type flow. The maximum value of
the average Nusselt number occurs when h = 0 and decreases with the increase of the
inclination angle. On the other hand, the increase of the channel width at exit for the same
inclination angle caused a monotonic increase in the flow velocity at the channel inlet.
Keywords
KeyWords Plus:PARALLEL-PLATE CHANNEL; NATURAL-CONVECTION; HEAT-TRANSFER;
AIR
Author Information
Reprint Address: Badr, HM (reprint author)
King Fahd Univ Petr & Minerals, Dept Mech Engn, Dhahran 31261, Saudi Arabia.
Organization-Enhanced Name(s)
King Fahd University of Petroleum & Minerals
Addresses:
[ 1 ] King Fahd Univ Petr & Minerals, Dept Mech Engn, Dhahran 31261, Saudi Arabia
Organization-Enhanced Name(s)
King Fahd University of Petroleum & Minerals
E-mail Addresses:badrhm@kfupm.edu.sa
Document Information
Document Type:Article
Language:English
Accession Number: WOS:000296665200011
ISSN: 0947-7411