Results And Discussion

Figure 1.3 shows the 45° angled ribs that were divided at the centerline to make the 45° V-shaped ribs. There are two different orientations of the V-shaped rib. The first orientation is called the 45° V-shaped rib and the second orientation is called the inverted 45° V-shaped rib. Figure 1.3 also shows the conceptual view of secondary flows that induced by the 45° angled rib, 45° V-shaped rib, and inverted V-shaped rib. The 45° angled rib induces secondary flow that moves parallel to the rib from the left side to the right side and return back to the left side making a counter rotating vortex (see Al-Qahtaini et al.21).

It is conjectured that the 45° V-shaped rib creates two counter rotating vortices. As the fluid approaching the V-shaped rib, it splits into two streams. Each one moves parallel to the rib from the centerline to the either left side or right side and returns back to the centerline making a counter rotating vortex. Another observation can be drawn that as the 45° V-shaped rib is half the 45° angled rib then the boundary layer thickness for the fluid that moves parallel to one side of the 45° V-shaped rib is thinner than that produced by the 45° angled rib. Therefore, as the 45° V-shaped rib produces two counter rotating vortices that promoting more mixing in the bulk main stream and at the same time produces thinner boundary layer near the heated surface, higher heat transfer rate is expected compared to 45° angled rib. However, different situation can be observed in the inverted 45° V-shaped rib. As the fluid approaching the inverted 45° V-shaped rib the near surface fluid starts moving simultaneously from the left side and right side to the centerline creating a stagnation region and then returns back to the starting positions creating two counter rotating vortices. This stagnation region may weak the two counter rotating vortices. Thus, 45° V-shaped rib is expected to perform better than the inverted 45° V-shaped rib in non-rotating condition since there is no such stagnation region that reduces the counter rotating vortices effect.

Case (a)
P=90 deg

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