(71m) Comparative Investigations of Dispersion Formation in Different Types of Micromixers

Different types of micromixers have been applied for l/l-dispersion and their potential for this purpose have been demonstrated in recent years. As advantages have been addressed e.g. a narrower droplet size distribution compared to conventional process (e.g. A. Kawai et al. [1]), numbering-up as scale-up concept while keeping product quality (e.g. A. Kawai et al. [1]), predictability of droplet size (e.g. S. Hardt et al. [2]), higher energy efficiency compared to conventional process (e.g. T. Bayer et al. [3]), high absolute energy efficiency (e.g. S. Sugiura et al. [4-5]) and production on demand (e.g. Schwesinger et al. [6]). Certainly, not all these potentials can be exploited by now for selected applications at one time especially when higher flow rates have to be considered. Beside the in literature documented experience, it is difficult at the moment to select the best suited mixer for a specific application. Mainly this is due to the fact that performance data of different mixers are often not comparable and that performance data are often incomplete. Comparability would require information on aspects like mean droplet size, width of droplet size distribution, throughput per unit, numbering-up concept, flow rate ratio necessary to obtain required droplet size, specific energy input and predictability of droplet size and mechanism of dispersion formation. Based on this background we performed comparative studies using different types of micromixers out of the range of IMMxs micromixers (Slit Interdigital Micro Mixer Version 2, Caterpillar Micro Mixer and Starlaminator Micro Mixer) representing different functional principles with heptane/water (SDS) as model system. The covered mixer types are parallel lamination micromixers, serial lamination (split-and-recombine) micromixers and injection micromixers (see the recent reviews by N.-T. Nguyen [7] and V. Hessel [8] for the classification of micromixers). Mean droplet size, coefficient of variation and energy input as function of flow rate were determined for all the mixers and compared. Furthermore, new investigations were performed to determine the influence of number of mixing steps and channel dimension in the case of the Caterpillar Micro Mixer on mean droplet size. Together with former experiments dealing with the Slit Interdigital Micro Mixer [9-11], this will allow a comparison of mixer performance on a broad basis and facilitate future equipment selection.

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