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Figure 2.3 Detailed Nusselt number distributions on trailing and leading surfaces;

Figure 2.4. Detailed Nusselt number distributions on trailing and leading surfaces;

Figure 2.4. Detailed Nusselt number distributions on trailing and leading surfaces;

Figures 2.5 and 2.6 show the spanwise-averaged Nusselt number ratios (Nu/Nuo) for the non-rotating and rotating cases, respectively. The inlet coolant-to-wall density ratio was held constant at 0.122. The spanwise-averaged Nusselt number distributions on the leading and trailing surfaces show periodic spikes. The higher spikes which occur on the ribs tops are caused by the flow impingement on the ribs, and the lower spikes (which occur right before and after the ribs) are caused by the flow reattachment between the ribs. The Nusselt number ratios are high in the regions between the ribs. The Nusselt number ratios reached a peak value around the eighth rib. This phenomenon is caused by the rib-induced secondary flow becoming stronger along the duct. As noted earlier, the channel rotation leads to an increase of Nusselt number on the trailing surface and a decrease of Nusselt number on the leading surface. However, the rotation effects are quite small at Ro = 0.14 when comparing to the heat transfer enhancement caused by the rib-induced flows. Additional computations will be performed in the near future for higher rotation number and higher density ratio cases to provide more detailed assessment on the effectiveness of the V-shaped ribs.

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