The effects of surface vortex on the drawdown and dispersion of floating particles in stirred tanks were investigated.Particle distribution and power consumption were analyzed by experiments and numerical simulations ...The effects of surface vortex on the drawdown and dispersion of floating particles in stirred tanks were investigated.Particle distribution and power consumption were analyzed by experiments and numerical simulations in both baffled and unbaffled tanks agitated by a Rushton impeller.In unbaffled tanks,a non-aggregation rule was applied and the average dispersion index was found to serve as a reasonable prediction of the full drawdown of floating particles.The critical impeller speeds in an unbaffled tank were higher than those in a tank with vertical baffles.At each immersion depth in a baffled tank,particles distributed more uniformly and more power was consumed.Comparison of snapshots of the baffled and unbaffled tanks shows that the surface vortex increases the drawdown speed while it decreases the particle distribution uniformity and power consumption.Therefore,the use of baffles to suppress the surface vortex provides for a more uniform particle distribution in stirred tanks.展开更多
基金This work was supported by the National Natural Science Foun-dation of China under Project Nos.51474109,51609090,and 51679097.
文摘The effects of surface vortex on the drawdown and dispersion of floating particles in stirred tanks were investigated.Particle distribution and power consumption were analyzed by experiments and numerical simulations in both baffled and unbaffled tanks agitated by a Rushton impeller.In unbaffled tanks,a non-aggregation rule was applied and the average dispersion index was found to serve as a reasonable prediction of the full drawdown of floating particles.The critical impeller speeds in an unbaffled tank were higher than those in a tank with vertical baffles.At each immersion depth in a baffled tank,particles distributed more uniformly and more power was consumed.Comparison of snapshots of the baffled and unbaffled tanks shows that the surface vortex increases the drawdown speed while it decreases the particle distribution uniformity and power consumption.Therefore,the use of baffles to suppress the surface vortex provides for a more uniform particle distribution in stirred tanks.
