The purpose of this paper is to numerically investigate fluid dynamics and heat transfer in a double forward-facing step (DFFS) channel with elliptic obstacles upstream of the steps. Obstacles with varying axis ratios (AR) are used to enhance heat transfer and reduce corner vortices, effectively eliminating hot spots.
An in-house solver using the Streamline Upwind/Petrov-Galerkin finite element method was used to analyze fluid flow. The study examined the effects of AR (0.25–1), vertical obstacle locations (0.2, 0.3, 0.4) and Reynolds numbers (Re) (300–1000) on flow and heat transfer, compared to a no-obstacle case.
The obstacles reduced the recirculation length upstream of the steps, affecting both flow behavior and the thermal characteristics of the heated bottom wall. The obstacles increased fluid mixing, enhancing the local heat transfer and reducing corner vortices. The maximum local heat transfer occurred at a vertical location of 0.4 and AR of 1, while the lowest pressure drop was observed at AR of 0.25 and a vertical location of 0.2. The local Nusselt number upstream of first and second step increased with obstacle vertical location. The space-averaged Nusselt number increased with higher Re. The thermal performance factor suggested that an AR of 0.25 and a vertical location of 0.2 provided the most favorable configuration for any specific engineering applications.
Fluid flow and heat transfer characteristics with elliptic-shaped obstacles at various vertical locations from the bottom wall in a double FFS are analyzed.
