Large Eddy Simulation of Two-Dimensional Impingement Jet Heat Transfer Enhanced by a Rib Turbulator

Abstract

Large Eddy Simulation (LES) was conducted to investigate two-dimensional impingement jet heat transfer enhanced by a square-rib turbulator placed in the wall jet region, where rapid decay of local heat transfer rate occurs in the case of impinging jet on a flat target wall. The effect of rib height on time-mean local Nusselt number upstream and downstream the square-rib was systematically examined by changing the height from 0.2 to 0.8 mm at an interval of 0.1 mm. In order to validate current LES, predicted time-mean local Nusselt number distribution was compared with the measured data by naphthalene sublimation method and found to be in good agreement with the experimental data except the jet-stagnation and flow-reattachment regions, where over- and under -estimation occurs. LES has successfully reproduced the decaying tendency of local Nusselt number downstream the flow reattachment point, while a RANS model failed to predict it. Concurrently performed LES on each rib-height realized the direct comparison of instantaneous Nusselt number among different ribs, and it was found that turbulent structures around the rib turbulator are not affected by the rib-height in the upstream region, but much affected by the rib-height in the downstream region.