Wastewater Mixing: A Comparison of Ragless and Hyperboloid Impellers


Claims have been made that hyperboloid impellers are better mixers for wastewater treatment basins than the more conventional ragless impellers. Leading the charge is the company Invent, AG claiming strong flow along the bottom of the tank and creating an “invisible wall” between adjacent impellers in a basin. Both are true, however, when similarly sized, the ragless impeller accomplishes both even better. Using AcuSolve CFD, we analysed the flow velocity along the bottom of the basins and between impellers to test these claims and make a side-to-side comparison putting both designs to the test. We also used the CFD to determine the mixing performance of the two impellers, where the ragless outshines the hyperboloids.

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