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Research Papers

# Numerical Simulation of the Effect of Rib Orientation on Fluid Flow and Heat Transfer in Rotating Serpentine Passages

[+] Author and Article Information
Berrabah Brahim

Department of Mechanical Engineering,
Materials and Reactive Systems Laboratory,
Faculty of Technology,
Djillali Liabes University,
Sidi bel-abbes 22000, Algeria
e-mail: Berrabah_brahim@yahoo.fr

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF THERMAL SCIENCE AND ENGINEERING APPLICATIONS. Manuscript received December 12, 2015; final manuscript received August 3, 2016; published online October 18, 2016. Assoc. Editor: Wei Li.

J. Thermal Sci. Eng. Appl 9(1), 011008 (Oct 18, 2016) (14 pages) Paper No: TSEA-15-1352; doi: 10.1115/1.4034597 History: Received December 12, 2015; Revised August 03, 2016

## Abstract

The effect of rib orientation on flow and heat transfer in a four-pass square channel with skewed ribs in nonorthogonal-mode rotation was numerically studied by using omega-based Reynolds stress model ($SMC−ω$). Two cases are examined: in first case, the ribs are oriented with respect to the main flow direction at an angle of $−45 deg$ in the first and third passage and at an angle of in the second passage. The second case is identical to the first case with the ribs oriented at angle of $+45 deg$ in the three passages. The calculations are carried out for a Reynolds number of 25,000, a rotation number of 0.24, and a density ratio of 0.13. The results show that the secondary flows induced by $−45 deg$ ribs and by rotation combine partially destructively in the first and third passage of first case. In contrast, for second case, the secondary flows induced by $+45 deg$ ribs and by rotation combine constructively in the first passage, while the flow is dominated by the vortices induced by $+45 deg$ ribs in the third passage. In first case, a significant degradation of the heat transfer rate is observed on the coleading side of the first passage and on both cotrailing and coleading sides of the third as compared to second case. Consequently, the rib orientations at $+45 deg$ are preferred in the radial outward flowing passage with an acceptable pressure drop. The numerical results are in agreement with the available experimental data.

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## Figures

Fig. 1

Geometrical configurations studied and rib orientation used

Fig. 2

45 deg channel orientation and rib configuration used. Cross sections of blade and channel viewed from axis of rotation.

Fig. 3

Numerical grid used and view of grid near the ribs. Locations of several planes (arrows indicate how the secondary flow patterns are viewed).

Fig. 6

Secondary flow streamlines and temperature contours in second passage for case 1 and case 2

Fig. 7

Secondary flow streamlines and temperature contours in third passage for case 1 and case 2

Fig. 8

Secondary flow streamlines and temperature contours in the three bends for case 1 and case 2 (the figures in the bends were pivoted of 45 deg)

Fig. 9

Secondary flow streamlines and temperature contours at the exit of the third bend (left) and the secondary flow contours (right) in fourth passage for case 1 and case 2

Fig. 10

Velocity vectors (u2+w2)0.5/Ub at 1/10 rib height from the cotrailing side for case 1 and case 2

Fig. 12

Distributions of local Nusselt number ratio for case 1 and case 2

Fig. 11

Effect of rib orientation on turbulent kinetic energy and Reynolds stress uv

Fig. 13

Distributions of local Nusselt number ratio on the others sides in case 1 and case 2 (the same Fig. 12 was pivoted of 180 deg)

Fig. 14

Effect of rib orientation on Nusset number ratio

Fig. 5

Secondary flow streamlines and temperature contours in first passage for case 1 and case 2

Fig. 4

Grid refinement study

Fig. 15

Effect of rib orientation on pressure drop

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