On the mixing enhancement in concentrated non-colloidal neutrally buoyant suspensions of rigid particles using helical coiled and chaotic twisted pipes: A numerical investigation

Abstract

Abstract Nevertheless the huge amount of numerical and experimental works on non-colloidal suspension flows, most studies in the literature were limited to the dynamics in different geometries like in channels and pipes. To author s knowledge, mixing enhancement quantification and suspension mixing behavior in static mixers has been rarely studied before. In the present contribution, the mixing enhancement in isothermal monodisperse neutrally buoyant non-Brownian suspensions is investigated through transient 3D CFD simulations. It is quantified for suspension Reynolds (ReS) numbers varying between 50 and 150, for spheres’ diameters (dp) between 25 and 400\u202fμm and for initial volume fractions of particles (ϕ) between 0.25 and 0.45. The influences of dp, ReS and ϕ on the overall mixing enhancement and on pressure drop are quantified for a suspension flow in a chaotic and helical separate pipes (static mixers of equal lengths). It is found that for all cases, the chaotic flow configuration has better mixing performances than the helical pipe flow with almost no significant increase in pressure losses. Moreover, good mixing quality is observed in both static mixers (better at larger particles) where the mixing index ranges between 10 and 75% relative to the initial unmixed particles leaving the straight pipe.