(74c) Theoretical and Experimental Studies of Mixing Enhancement in Micromixers

Mixing in microchannel mixers/reactors, most especially for liquid phase reactions, is a relevant technical issue critical to the development and application of integrated microchemical processing systems. The objective of this work is to investigate mixing enhancement in microchannel mixers, through a theoretical as well as an experimental mixing study of currently utilized and three proposed micromixing configurations. The proposed micromixers are passive mixers uniquely designed to effect mixing using static or passive mixing structures by creating folding as well as local and global re-orientation of fluid interfaces. Using Computational Fluid Dynamics (CFD) approach and suitable mixing characterization techniques, one of the proposed mixing configurations herein referred to as multilaminated/elongational flow micromixer-4 (MEFM-4) was selected based on the set criteria of minimum pressure drop and high mixing performance. The selected MEFM-4 was then employed along with the standard T-junction micromixer (TjM) for our experimental mixing study. In order to experimentally characterize mixing in the micromixers, residence time distribution (RTD) measure in conjunction with UV-vis absorption spectroscopy detection technique was used. Using the so-called convolution-deconvolution technique based on Levenspiel's Convolution Integral Theorem, some of the challenges associated with the use of time-dependent concentration data of a dye tracer for RTD determination in micromixers were overcome. With the application of this technique and suitable programming scheme, the experimental data obtained for the T-junction micromixer and MEFM-4 were analyzed while dispersion model and other suitable models were used to fit the data. The model parameters obtained were then used to indirectly evaluate mixing quality in the micromixers at different flow conditions. The validation of our prior theoretical results and comparison of the mixing performance of the standard TjM with the proposed MEFM-4 will also be presented.