Single impeller higher viscosity fluid mixing above 50,000cps with axial turbines is difficult as the flow becomes laminar or radial. The downward thrust of axial turbines leaves static zones near the vessel walls and increasing the impeller diameter further just delivers more down thrust – but without actual ‘mixing’ as product or materials are not draw up and around the vessel walls effectively.
Contraflow impellers resolve this issue by the twist across the central section of the impeller, offering up thrust to the outer section of fluid. Due to the kinetic energy delivered by down thrusting the core and up thrusting the outer section of the mixing chamber, a flow pattern evolves to offer good fluid mixing, once more.
These mixer types are generally used for the mixing of miscible fluids and re-agitation or suspension of viscous fluids and require a low energy input and speed – so very cost effective to run in the long term.