Heat transfer and flow friction performance of rotating rectangular channels with different dimple/protrusion structures

A numerical simulation was performed to investigate the heat transfer and flow friction performance of rotating rectangular channels assigned with dimples and protrusions on each side. The viscous Navier-Stokes equations were solved using the shear-stress transport (SST) turbulence model. Three dimple/protrusion structures were discussed including circled dimple/protrusion, horizontal oval dimple/protrusion, and vertical dimple/protrusion. The results indicate that the heat transfer increases significantly near the windward side of the protrusion, and there is flow separation and the heat transfer near the leeward rim and in the wake region falls. On the dimple side, a higher heat transfer rate is observed in the region of shear layer reattachment on the second half of the dimple cavity while the first half of the cavity has the lower heat transfer rate because of flow separation. The channel rotation has great effect on heat transfer and friction performance because the rotation will affect the place where separation and reattachment occur and energize the flow near trailing surface. The comparison shows that the average Nu number and the friction ratio of the vertical dimple/protrusion channel are almost the same as those of the circular dimple/protrusion channel while the horizontal dimple/protrusion channel has larger average Nu and the friction ratio than the others.