Keywords: critical speed, oxygen transfer, baffled surface aerators, vortex depth, power consumption, surface aeration, mass transfer, process industries, stirred tanks
Vortex in baffled surface aerator
Baffled surface aerator and mixing tanks are different on the basis of the rotor placement. In mixing tanks, rotors are placed very deep in the tank, thus vortex creation can be prevented by placing the baffles. By definition, rotors are placed at or near the surface of water in surface aeration systems; complete prevention of vortex creation cannot be achieved by installing the baffles. Vortex geometry, thus created, imparts a major effect on the system efficiency. How deep a vortex can penetrate into a liquid layer is undoubtedly important in the design as well as the operation of the surface aeration systems. In the present work, empirical correlations have been tried to relate the vortex depth to a number of physical factors. It is found that around critical speed, there is an observable change in mass transfer characteristics, power used for mixing and radius of the forced vortex zone.