The power dissipated by one-, two-, or three-disk turbines (Rushton type) in stirred vessels was experimentally determined under turbulent conditions. The power dissipated by each individual impeller (in single- or multiple-impeller configurations) and the total power consumption were measured by means of strain gauges mounted on the shaft and were reported as individual or total power numbers. Results were obtained for different combinations of number of impellers, off-bottom clearance of the lowest impeller, and spacing among impellers. These variables were found to play a very important role in the power drawn by individual impellers and, hence, the total power consumption. The impeller closest to the vessel bottom generally consumed significantly less power than the other impeller(s). This was especially true for combinations of low impeller clearances and small impeller spacing. Proximity of two impellers also lowered their power consumption. Only when the impellers were significantly spaced apart and the lowest impeller sufficiently distant from the vessel bottom did each individual impeller draw a power approaching that of a single-impeller configuration. The results of this work can be used to predict the power consumed by individual impellers in multiple-impeller systems and therefore to help scale-up processes (such as those dominated by different local mass-transfer coefficients in different parts of the vessel) in which knowledge of the local power dissipation may be critical.
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)
- Industrial and Manufacturing Engineering