ChBE Seminar Series: Richard Calabrese
Tuesday, October 23, 2007
11:00 a.m.-12:00 p.m.
Room 2110 Chemical & Nuclear Engineering Bldg.
Professor Nam Sun Wang
Prediction of Drop Size and Effect of Surfactant Concentration in Agitated, non-Coalescing Liquid-Liquid Dispersions
Presented by Professor Richard Calabrese
Department of Chemical and Biomolecular Engineering
University of Maryland
This talk will consist of two parts. In the first, we will discuss the development and validation of mechanistic theories to predict equilibrium drop size in turbulent liquid-liquid systems that are dilute or otherwise stabilized against coalescence. It will be argued that breakage phenomena depend upon microscopic flow details that also determine the ultimate drop size. As a result, correlation methods are independent of device geometry and a common basis exists to assess device performance. Special consideration will be given to high shear mixers to demonstrate that dispersion mechanisms are similar to those for more conventional contactors and to lay the foundation for interpretation of surfactant studies.
In the second part we will focus in more detail on a recent study to understand the effect of surfactant concentration on drop breakup and the ultimate drop size. We will report the results of carefully controlled experiments in a batch rotor-stator mixer to demonstrate that surfactants play a very different role in breakage than in coalescence phenomena. We will present our attempts to quantify the role of the surfactant via measurement and analysis of interfacial properties. This allows us to modify existing mechanistic correlations for mean drop size to include interfacial resistance to drop deformation. Limitations of the study and directions for future work will also be discussed.