Numerical investigation of turbulent heat transfer enhancement in a ribbed channel with upper-downstream-shaped deflectors

Enhancement of bottom wall forced convection heat transfer rates in a ribbed cooling channel combined with differently shaped deflectors is investigated numerically. Four deflectors, including the sloping board (Case A), convex curved (Case B), concave curved (Case C), and cylindrical (Case D) deflectors, are mounted on the upper-downstream side of the ribs. The heat transfer and flow features are analyzed and compared based on the validation of the turbulence model and careful study of the grid independence. The results show that the flow structures are deeply affected by the deflectors, accompanied by changes in the heat transfer and friction factor. Compared with the ribbed channel with sloping board deflectors, Case B can guide the mainstream fluid to compress the recirculating flow region located on the lee-side regions downstream from the rib and can enhance the heat transfer of the bottom surface, despite the increasing friction factor. It is noted that the decrement ratio of the friction factor in Case D is 7.0-12.4%. Based on this remarkable expression, Cases B and D contribute to better overall performance. This is due to their prominent performance in the heat transfer enhancement and diminished flow resistance.