Measurement and analysis of drop size in a batch rotor-stator mixer

In order to evaluate the performance of high shear mixers, drop size has been measured in a batch rotor-stator mixer for dilute dispersions of low viscosity organics in water. Data were acquired, in-situ, using a novel video probe and automated image analysis software. Power draw was also measured. A class of mechanistic models, which account for drop interactions with turbulent velocity fluctuations and the shear field at various length scales, were developed to aid in data interpretation and provide a basis for correlation. Analysis of the data revealed that equilibrium drop sizes were of the order of the Kolmogorov microscale and that "mean shear" in the rotor-stator gap was not the predominant breakage mechanism. Furthermore, models that account for inertial drop-eddy interactions and sub-microscale shear forces, suggesting a mixed breakage mechanism, equally correlated the data.