Publication Date:
2011-04-03
Description:
The particular benefits of microfluidic systems, in terms of heat and mass transfer enhancement, require conducting local flow diagnostics, especially when unsteady properties of the microflow can play a critical role at the reaction interface, as currently observed in the fields of bioengineering and chemical engineering. The present paper focuses on unsteady confined flows within microsystems characterized by various geometries of crossing channels and exhibiting high surface-to-volume ratios. An experimental analysis of the signal measured at microsensors embedded to the wall of microsystems is discussed. In the objective of performing flow diagnostics, including regime identification and wall flow structure recognition, two methods for electrochemical signal processing are investigated and compared within an experimental network of crossing minichannels. One method is based on the use of a transfer function, while the other, the so-called Sobolik solution (Sobolik et al . in Coll Czech Chem Commun 52:913–928, 1987 ), consists of finding a direct solution to the mass balance equation. Sobolik’s method has been selected given its ability to provide a description, over a wide range of Reynolds numbers (317 〈 Re 〈 3,535), for all wall shear rate fluctuations, as well as for the associated mixing scales in the power spectra density (PSD). This technique is then applied to flow within micromixers composed of two crossing microchannels in order to study highly unsteady and inhomogeneous microflows. The hydraulic diameters of the studied channels are 500 and 833 μm, respectively. Two flow patterns are investigated herein: the crossing-flow type and the impinging flow (or so called co-flow) for a Reynolds number range between 173 and 3,356. The PSD of wall shear rate fluctuations reveals various flow characteristics depending on the microchannel aspect ratio. Content Type Journal Article Pages 1-14 DOI 10.1007/s00348-011-1079-1 Authors F. Huchet, IFSTTAR, Department Materials, Aggregates and Materials Processing, Route de Bouaye, BP 4120, 44341 Bouguenais Cedex, France P. Legentilhomme, GEPEA, Université de Nantes, CNRS, UMR 6144, C.R.T.T, 37 bd de l’Université, BP 406, 44602 Saint-Nazaire Cedex, France J. Legrand, GEPEA, Université de Nantes, CNRS, UMR 6144, C.R.T.T, 37 bd de l’Université, BP 406, 44602 Saint-Nazaire Cedex, France A. Montillet, GEPEA, Université de Nantes, CNRS, UMR 6144, C.R.T.T, 37 bd de l’Université, BP 406, 44602 Saint-Nazaire Cedex, France J. Comiti, GEPEA, Université de Nantes, CNRS, UMR 6144, C.R.T.T, 37 bd de l’Université, BP 406, 44602 Saint-Nazaire Cedex, France Journal Experiments in Fluids Online ISSN 1432-1114 Print ISSN 0723-4864
Print ISSN:
0723-4864
Electronic ISSN:
1432-1114
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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