Numerical Investigation of the Flow and Heat Transfer in Convergent Swirl Chambers

Abstract

Confined swirling flows are a promising technique for cooling applications since they achieve high heat transfer rates. In such systems, however, an axial flow reversal can occur, which corresponds to the axisymmetric vortex breakdown phenomenon.

This report presents a numerical study using Delayed Detached Eddy Simulations (DDES) in order to analyze the impact of convergent tube geometries on the flow field and the heat transfer in cyclone cooling systems. For this purpose, a comparison is drawn for a Reynolds number of 10, 000 and a swirl number of 5.3 between a constantdiameter tube and four convergent tubes. The latter comprise three geometries with linearly decreasing diameters yielding convergence angles of 0.42 deg, 0.61 deg and 0.72 deg, respectively. Additionally, a single tube with a hyperbolic diameter decrease was analyzed.

The results demonstrate that converging tubes enforce an axial and circumferential flow acceleration. The axial flow acceleration counteracts the flow reversal and thus was proved capable of suppressing the vortex breakdown phenomenon. Further, the heat transfer in terms of Nusselt numbers shows a strong dependency on the tube geometry.