Effects of impeller and baffle conditions on mixing time in turbulent agitated vessels

摘要

Effects of impeller and baffle conditions on mxiing time was discussed for baffled and non-baffled agitated vessels with paddle,pitched-balde paddle and turbine impellers.First,the effects of tracer injection position and baffle condition on mixing time were examined experimentally.At the baffle condition of n_b~(0.8) (B-w/D)>=0.1 the mixing time measured was almost uniform independently of the tracer injection position.Second,the effect of impeller conditions on mixing time was examined experimentally.The mixing time in a baffled agitated vessel with a paddle impeller was well correlated using the impeller condition parameter n_p~(0.7)(b/d),and a mixing time correlation was proposed.The mixing time in a baffled vessel with a pitched-blade paddle impeller was correlated in the same manner as for the paddle impeller,by modifying the impeller condition parameter as n_p~(0.7) (b sin~(0.16)#theta#/d).For a small paddle impeller(d/D<=0.3) and small pitched-blade paddle impeller(d/D<=0.4),the mixing time in a non-baffled agitated vessel coincided with that in a baffled vessel.