The effect of turbulence on the efficiency of the rotational phase separator

The rotational phase separator (RPS) is a device to separate liquid or solid particles from a lighter or heavier fluid by centrifugation in a bundle of channels which rotate around a common axis. Originally, the RPS was designed in such a way that the flow through the channels is laminar in order to avoid eddies in which the particles keep circulating and do not reach the walls. However, in some applications the required volume flow of fluid is so large, that turbulent flow can no longer be avoided. Direct numerical simulation of the flow in a single rotating pipe and particle tracking in this flow are applied to study the influence of turbulence on the collection efficiency of the RPS. The results show that the collection efficiency for larger particles decreases by up to 25% due to the turbulence, whereas the collection efficiency for smaller particles is unaffected. The adverse effect of the resulting swirling flow is partly counteracted by turbulent dispersion. For high rotational speeds the efficiency decreases further as the particles are trapped in a counter-rotating vortex.