Channel Averaged Nusselt Number Ratio

Figure 1.8 presents the averaged Nusselt number ratio distribution for smooth, 45° angled rib, parallel and crossed 45° V-shaped ribs. The results show that the ribs surfaces provide higher Nusselt number ratios than smooth surfaces in both passes. This is because ribs trip the boundary layer and induce secondary flows that enhance the heat transfer rate. In stationary case, Parallel 45° V-shaped ribs show higher Nusselt number ratio distribution than crossed 45° V-shaped ribs because they generate two pair of counter rotating vortices, while crossed case produces one pair of counter rotating vortices. In case of rotation, trailing surfaces in the first pass are higher than the leading surface and leading surfaces in the second pass are higher than trailing surfaces due to Coriolis effects for both cases parallel and f crossed. Also, crossed case shows less rotation effects. This is because the ribs induced secondary flows move against the rotational secondary flows.

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