Computational investigation of low-Reynolds-number flow vortices in coiled tubes

Coiled tubes are deployed in polymerisation, production of nanoparticles, extraction, and retrofits to heat-exchanger systems, where plug flow is a desirable characteristic. In this study, we superimpose oscillatory fluid motion at a low flow rate (with a Reynolds number, Re = 50) to characterise the vortex structures affecting plug flow. We apply a transient computational fluid dynamics analysis with a scalar transport technique, and tracer injection into the water working fluid. Oscillation amplitudes are varied for a set of coil geometries in order to understand the effect of vortices on residence time distribution and tracer mixing concentration. For optimal oscillation amplitudes, enhanced plug-flow performance is achieved due to the formation of Dean vortex structures. Existing processes with coiled tubes can be improved by easily implementing an oscillating motion.