Effect of rotation on heat transfer in two-pass square channels with five different orientations of 45° angled rib turbulators

The effect of various 45° angled rib turbulator arrangements on the Nusselt number ratio in a rotating, two-pass, square channel is investigated for three Reynolds numbers (5000, 10,000, 25,000), with rotation number up to 0.11, and two channel orientations with respect to the axis of rotation (ß 90° and 135°). Five different arrangements of rib turbulators are placed on the leading and trailing surfaces at an angle of +45° or-45° to the main stream flow. The rib height-to- hydraulic diameter ratio (e=D) is 0.125; the rib pitch-to-height ratio (P/e) is 10; and the inlet coolant-to-wall density ratio (Δρ=ρ) is maintained around 0.11. The results show that the rotating ribbed surface Nusselt number ratios increase by a factor of 2 compared to the rotating smooth surface results. The results also show that the heat transfer enhancement depends on the rib-angle orientation (+45° or-45°)) to the main stream flow in the first or second pass of the channel for both rotating and non-rotating conditions. Overall, the parallel rib cases show better heat transfer enhancement than the crossed rib case for both rotating and non-rotating conditions. The 90° channel orientation with respect to the axis of rotation produces greater rotating effect on heat transfer over the 135° channel orientation.