MIXING EFFICIENCIES AND ENERGY REQUIREMENTS OF VARIOUS MOTIONLESS MIXER DESIGNS FOR LAMINAR MIXING APPLICATIONS

The effectiveness of five designs of motionless mixer for laminar mixing has been assessed using an autocorrelation technique for mixture quality assessment based on colour development of two streams of epoxy resin, one coloured black, the other white. The performance of the mixers was assessed by referring improvement in mixture quality to the power consumption required by each mixer design, and the results compared with the recent studies of Allocca (1) and of Pahl and Muschelknautz (4). The five mixer designs studied were the Kenics 'Static Mixer', the Ross 'ISG' and 'LPD' designs and the Sulzer Brothers* 'SMX' and 'SMV' mixers. Pressure drop data for laminar flow in these mixers were obtained for two fluids, one Newtonian and the other slightly shear-thinning, over the approximate Reynolds number range of 10–5 to 3. The results show that although the Ross 'ISG' unit gave the most rapid mixing in terms of the number of elements required, or the length of mixer, to give a specified improvement in mixture quality, the power requirement incurred was extremely high. The largest improvements in mixing quality per unit power consumption were obtained using the Kenics 'Static Mixer' and the Ross 'LPD' design, with the Sulzer Brothers' 'SMX' and 'SMV' designs ranked between the Ross 'LPD* and 'ISG' mixers.