SCALAR MIXING MEASUREMENTS IN BATCH OPERATED STIRRED TANKS

An LIF technique was used to obtain unobtrusive measurements of scalar concentration as a function of time and mixing times in a fully baffl ed batch operated mixing vessel agitated by five forms of impeller (Ru shton, 'bucket', six bladed 45 degrees- and 60 degrees-pitched blade, hyperboloid). The mixing time was comparable to the time required for the dye/scalar to be transported from the top of the vessel to the bot tom part plus the time required for a further two rotations of the bul k flow in the circumferential direction. At constant power input the m ixing times for similar impellers were similar, although different for different types.