2005 Volume 38 Issue 9 Pages 688-691
An unsteady mixing speed was applied to laminar mixing in a vessel containing a conventional impeller. Three non-circle cams were combined to generate the unsteady speed in an impeller revolution. The mixing performances of the unsteady speed impeller were compared with those of a conventional impeller operated under a steady speed. The mixing time and the flow pattern were measured by flow visualization using the discoloration method in which sodium thiosulfate reacts with an iodine solution. Because the unsteady motion moved the center of the vortices, the doughnut rings above and below the impeller disappeared when unsteady mixing was employed.