Numerical investigation of turbulent flow and heat transfer in two-pass ribbed channels

In this study, the heat transfer and friction characteristics of four different rib geometries- 45° angled, V-shaped, W-shaped and M-shaped ribs in a two-pass stationary channel have been numerically investigated. The aspect ratio (Height to Width) of the cooling channel was 1:1 (square). The rib pitch-to-rib height ratio (p/e) and the rib-height-to-channel hydraulic diameter ratio (e/Dh) were 16 and 0.125 respectively. The Reynolds number was varied from 20,000 to 70,000. For the computations, the Reynolds averaged Navier-Stokes (RANS) equations were solved with the commercial software ANSYS Fluent using the realizable version of k-ε (RKE) model. The heat transfer results were benchmarked with experiments on a test rig with similar geometries and flow conditions. Detailed analysis of the flow characteristics in the two-pass channel was carried out so as to understand the interaction of the rib-induced secondary flows and the bend-induced secondary flows and their contribution to heat transfer enhancement. The heat transfer enhancement provided by V-shaped ribs was 7% higher than 45° ribs, 28% higher than W-shaped ribs and 35% higher than M-shaped ribs. However, the pressure penalty for V-shaped ribs was 19% higher than 45° ribs, 24% higher than W-shaped ribs and 28% higher than M-shaped ribs. On comparing the overall thermal hydraulic performance, V-shaped and 45° ribs were observed to perform significantly better than W-shaped and M-shaped ribs.