(36c) Investigation of Mixing in Micro- and Minichannels with Reactive Fluorescent Dyes

Efficient mixing on microscales is a difficult unit operation due to the small dimensions and mostly laminar flow conditions. Even in simple and often used T-shaped geometries it has to be assured that a multi-lamellar flow structure is achieved by engulfment flow. For the investigation of the critical operation conditions experimental analysis have been performed with the optical measurement methods of Micro Particle Image Velocimetry and Confocal Laser Scanning Microscopy (Hoffmann et al., 2009). It has been shown by means of reacting fluorescent dyes with known reaction rates that the visualisation and quantitative analyses of chemical reactions in micro- and minichannels are possible. A regime transition to engulfment flow occurs at a certain Reynolds number dependent on the reactor dimensions that can be predicted by a modified model of Soleymani et al. (2008). This transition leads to different efficiency of micromixing measurable by the fluorescence intensity of the reaction product. The experimental results are in good agreement with numerical simulations performed by our cooperation partners (Bothe et al., 2008).

Hoffmann, M., Schlüter, M., Räbiger, N. (2009) Microscale Flow Visualization. In: Hessel V, Renken A, Schouten J C, Yoshida J (eds.) Micro Process Engineering, 1st edn. Wiley-VCH, Weinheim

Soleymani, A., Kolehmainen, E., Turunen, I.: Numerical and experimental investigations of liquid mixing in t-type micromixers. Chem. Eng. J. 135 (2008), p. 219 ? 228.

Bothe, D.; Stemich, C.; Warnecke, H.-J.: Computation of scales and quality of mixing in a T-shaped microreactor. Computers and Chemical Engineering 32 (2008) 108?114.

This work is supported by the German Research Foundation (DFG), priority program ''Analysis, Modeling and Calculation of Mixing Processes with and without Chemical Reaction'', grant RA 574/17.