Heat Transfer Enhancement of Separated Convection Flow Adjacent to Backward-Facing Step With Baffle

Abstract

Simulations of three-dimensional laminar forced convection adjacent to inclined backward-facing step in rectangular duct are presented to examine effects of the baffle on flow and heat transfer distributions. The step height is maintained as constant. A baffle is mounted onto the upper wall and its distance from the backward-facing step is varied. The inlet flow is hydrodynamically steady and fully developed with uniform temperature. The bottom wall is heated with constant heat flux, while other walls are maintained as being thermally adiabatic. Velocity, temperature, Nusselt number, and friction coefficient distributions are presented. A baffle mounted onto the upper wall increases the magnitude of maximum Nuselt number at the stepped wall. One segment of the xu-line developing close to the backward-facing step becomes shorter with the decrease of the distance of the baffle from the backward-facing step. It becomes more relatively uniform in the spanwise direction as the distance decreases. The other segment developing adjacent to the sidewall moves further downstream as the baffle moves in the streamwise direction. The maximum Nusselt number does not appear at the center of the duct, as one may expect. It develops near the sidewall, and it moves further downstream as the location of the baffle moves in the streamwise direction. The friction coefficient at the stepped wall decreases as the distance of the baffle from the inlet increases.