Measurement and Analysis of Drop Size in a Batch Rotor-Stator Mixer

Publisher Summary High shear mixers are broadly employed in chemical processes to produce emulsions and liquid–liquid dispersions. Despite their widespread use, there is almost no fundamental basis that could be used to theoretically predict or experimentally assess their performance. In order to evaluate the performance of high shear mixers, this chapter measures drop size in a batch rotor-stator mixer for dilute dispersions of low viscosity organics in water. Data are acquired, in-situ, using a novel video probe and automated image analysis software. Power draw is also measured. A class of mechanistic models, which account for drop interactions with turbulent velocity fluctuations and the shear field at various length scales, are developed to aid in data interpretation and provide a basis for correlation. Analysis of the data reveal that equilibrium drop sizes are of the order of the Kolmogorov microscale and that “mean shear” in the rotor-stator gap is not the predominant breakage mechanism. Furthermore, models that account for inertial drop-eddy interactions and submicroscale shear forces, suggesting a mixed breakage mechanism, equally correlate the data.