Large Eddy Simulation of Flow and Heat Transfer in a Staggered 45° Ribbed Duct

Abstract

Results from large eddy simulation (LES) of fully developed flow in a staggered 45° ribbed duct are presented with rib pitch-to-height ratio P/e = 10 and a rib height to hydraulic diameter ratio e/Dh = 0.1. The nominal Reynolds number based on bulk velocity is 47,300. Mean flow and turbulent quantities, together with heat transfer and friction augmentation results are presented. The flow is characterized by a helical vortex behind each rib and a complementary cross-sectional secondary flow, both of which result from the angle of the rib with respect to the mean flow. Averaged velocity profiles at the duct center show excellent agreement with experiments and heat transfer predictions agree well with experiments. Turbulent kinetic energy, shear stress, and heat transfer augmentation ratios show a strong correlation to the rib vortex and the secondary flow. Overall, heat transfer is augmented by a factor of 2.3 compared with a smooth duct and matches experimental data within 2%.