Heat Transfer Enhancement of a Backward-Facing Step Flow in a Duct by Static and Dynamic Devices

Flow modification downstream of a backward-facing step has been tried in order to achieve heat transfer enhancement by introducing two kinds of devices, a triangle prism rib and electromagnetic actuators, on the step edge. The triangle rib attached to the side-wall corner makes the downward flow inclined and generates a circulation-like fluid motion behind it. Because both flows work effective in reducing the flow re-circulation caused behind the step, large heat transfer recovery is obtained near the side-wall. This advantage of the triangle rib remains effective when the flap actuations are imposed. Thus, the large-scale unsteady vortex intensively reduces the flow recirculation, the triangle rib with flap actuations attains the largest heat transfer recovery behind the step.