Longitudinal Vortices Mixing in Three-Stream Micromixers with Two Inlets

Authors: Yi-Tun Huang, Chih-Yang Wu, Shu-Wei Huang

Abstract:

In this work, we examine fluid mixing in a full three-stream mixing channel with longitudinal vortex generators (LVGs) built on the channel bottom by numerical simulation and experiment. The effects of the asymmetrical arrangement and the attack angle of the LVGs on fluid mixing are investigated. The results show that the micromixer with LVGs at a small asymmetry index (defined by the ratio of the distance from the center plane of the gap between the winglets to the center plane of the main channel to the width of the main channel) is superior to the micromixer with symmetric LVGs and that with LVGs at a large asymmetry index. The micromixer using five mixing modules of the LVGs with an attack angle between 16.5 degrees and 22.5 degrees can achieve excellent mixing over a wide range of Reynolds numbers. Here, we call a section of channel with two pairs of staggered asymmetrical LVGs a mixing module. Besides, the micromixer with LVGs at a small attack angle is more efficient than that with a larger attack angle when pressure losses are taken into account.

Keywords: Microfluidics, Mixing, Longitudinal vortex generators, Two stream interfaces.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1093538

References:

[1] V. Hessel, H. Löwe, and F. Schönfeld, "Micromixers—a review on passive and active mixing principles," Chem. Eng. Sci., vol. 60, pp. 2479-2501, 2005.
[2] N. T. Nguyen and Z. Wu, "Micromixers—a review," J. Micromech. Microeng., vol. 15, pp. R1-R16, 2005.
[3] G. S. Jeong, S. Chung, C. B. Kim, and S. H. Lee, "Applications of micromixing technology," Analyst, vol. 135, pp. 460-473, 2010.
[4] A. D. Stroock, S. K. W. Dertinger, A. Ajdari, I. Mezic, H. A. Stone, and G. M. Whitesides, "Chaotic mixer for microchannels," Science, vol. 295, pp. 647-651, 2002.
[5] S. W. Lee, D. S. Kim, S. S. Lee, and T. H. Kwon, "A split and recombination micromixer fabricated in a PDMS three-dimensional structure," J. Micromech. Microeng., vol. 16, pp. 1067-1072, 2006.
[6] R. Yang, J. D. Williams, and W. J. Wang, "A rapid micro-mixer/reactor based on arrays of spatially impinging micro-jets," J. Micromech. Microeng., vol. 14, pp. 1345-1351, 2004.
[7] N. Aoki, R. Umei, A. Yoshida, and K. Mae, "Design method for micromixers considering influence of channel confluence and bend on diffusion length," Chem. Eng. J., vol. 167, pp. 643-650, 2011.
[8] M. Engler, N. Kockmann, T. Kiefer, and P. Woias, "Numerical and experimental investigations on liquid mixing in static micromixers," Chem. Eng. J., vol. 101, pp. 315-322, 2004.
[9] V. Hessel, S. Hardt, H. Löwe, and F. Schönfeld, "Laminar mixing in different interdigital micromixers: I. Experimental characterization," AIChE J., vol. 49, pp. 566-577, 2003.
[10] K. S. Drese, "Optimization of interdigital micromixers via analytical modeling - exemplified with the SuperFocus mixer," Chem. Eng. J., vol. 101, pp. 403-407, 2004.
[11] M. Q. Yi and H. H. Bau, "The kinematics of bend-induced mixing in micro-conduits," Int. J. Heat Fluid Flow., vol. 24, pp. 645-656, 2003.
[12] F. Jiang, K. S. Drese, S. Hardt, M. Küpper, and F. Schönfeld, "Helical flows and chaotic mixing in curved micro channels," AIChE J., vol. 50, pp. 2297-2305, 2004.
[13] R.-T. Tsai and C.-Y. Wu, "An efficient micromixer based on multidirectional vortices due to baffles and channel curvature," Biomicrofluidics, vol. 5, 2011.
[14] C.-Y. Wu and R.-T. Tsai, "Fluid mixing via multidirectional vortices in converging-diverging meandering microchannels with semi-elliptical side walls," Chem. Eng. J., vol. 217, pp. 320-328, 2013.
[15] A. Bertsch, S. Heimgartner, P. Cousseau, and P. Renaud, "Static micromixers based on large-scale industrial mixer geometry," Lab Chip, vol. 1, pp. 56-60, 2001.
[16] Y.-L. He and Y. Zhang, "Advances and outlooks of heat transfer enhancement by longitudinal vortex generators," in: Advances in Heat Transfer, vol. 44, E. M. Sparrow, Y. I. Cho, J. P. Abraham and J. M. Gorman, Eds. Amsterdam: Elsevier, 2012, pp. 119-185.
[17] M. Kaniewski, H. W. Hahne, and N. K. Mitra, "Mass transfer enhancement by longitudinal vortices," Heat and Mass Transf., vol. 32, pp. 163-166, 1997.
[18] C. Liu, J.-T. Teng, J.-C. Chu, Y.-L. Chiu, S. Y. Huang, S. P. Jin, T. T. Dang, R. Greif, and H. H. Pan., "Experimental investigations on liquid flow and heat transfer in rectangular microchannel with longitudinal vortex generators," Int. J. Heat Mass Transf., vol. 54, pp. 3069-3080, 2011.
[19] K.-Y. Hsiao, C.-Y. Wu, and Y.-T. Huang, "Fluid mixing in a microchannel with longitudinal vortex generators," Chem. Eng. J., vol. 235, pp. 27-36, 2014.
[20] R.-T. Tsai and C.-Y. Wu, "Multidirectional vortices mixing in three-stream micromixers with two inlets," Microsyst. Technol., vol. 18, pp. 779-786, 2012.
[21] S. A. Rani, B. Pitts, and P. S. Stewart, "Rapid diffusion of fluorescent tracers into Staphylococcus epidermidis biofilms visualized by time lapse microscopy," Antimicrob. Agents Chemother., vol. 49, pp. 728-732, 2005.
[22] J. Boss, "Evaluation of the homogeneity degree of mixture," Bulk Solids Handl., vol. 6, pp. 1207-1215, 1986.