Heat transfer and flow behavior around four staggered elliptic cylinders in cross flow |
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Authors: | Nabil S Berbish |
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Institution: | (1) Mechanical Engineering Department, Shoubra Faculty of Engineering, Benha University, Benha, Egypt |
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Abstract: | Experimental and numerical studies were carried out to investigate forced convection heat transfer and flow features around
the downstream elliptic cylinder in four staggered cylinders in cross flow. The elliptic cylinders examined had an axis ratio
(b/c) of 1:2, and they were arranged with zero angle of attack to the upstream flow. The present heat transfer measurements
were obtained by heating only the downstream elliptic cylinder (test cylinder) under the condition of constant heat flux.
The testing fluid was air and the Reynolds number based on the major axis length (c) was ranged from 4,000 to 45,570. The
tested longitudinal spacing ratio (Sx/c) and the transversal spacing ratio (Sy/b) were in the ranges of 1.5 ≤ Sx/c ≤ 4.0 and 1.5 ≤ Sy/b ≤ 4.0, respectively. The air flow pattern and temperature fields around the four staggered elliptic cylinders were predicted
by using CFD software package. Also, a flow visualization study was made to show the flow features around the elliptic cylinders.
It was observed that Num of the downstream elliptic cylinder in four staggered cylinders was higher than that of three in-line cylinders for all tested
spacing ratios and Reynolds numbers except for Re = 4,000. It was clear that, at lower Reynolds number values (Re < 14,100),
the average Nusselt number of the downstream elliptic cylinder in three staggered arrangement was higher than that of the
downstream cylinder in four staggered arrangement for all tested spacing ratios. On the other hand, at Re > 14,100, the tested
elliptic cylinder in four staggered arrangement had the higher values of the average Nusselt number. Moreover, in four staggered
arrangement, the maximum average Nusselt number enhancement ratio (average Nusselt number of the tested downstream cylinder/average
Nusselt number of a single elliptic cylinder) was found to be about 2.0, and was obtained for spacing ratios of Sx/c = 2.5, Sy/b = 2.5 and at Re = 32,000. Finally, the average Nusselt number of the tested cylinder in four staggered arrangement was
correlated in terms of Reynolds number and cylinder spacing ratios. |
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