Figure shows how the feed point's position along the working height of the tank affects macromixing according to the dispersion model. As was anticipated in analyzing eqs 3 and 6, placing the feed point in the middle divides the mixing time-scale (standard deviation 5 % of mean) by 4. Similar results have been presented previously: injecting the tracer in the middle of a multi-impeller tank minimized mixing times in experiments as well as in compartment model simulations . The compartment model predictions were also partly verified with experiments . Even though the observed mixing time reductions by a factor of approximately 2 were smaller than the model proposes, it is worth noting that mixing in real vessels stirred with multiple impellers behaved in accordance with the dispersion model's prediction.