Port Positions on the Mixing Efficiency of a Rotor-Type Mixer – A Numerical Study

The purpose of this study was to explore the complex flow structure a novel active-type micromixer that based on concept of Wankle-type rotor. The characteristics of this micromixer are two folds; a rapid mixing of reagents in a limited space due to the generation of multiple vortices and a graduate increment in dynamic pressure as the mixed reagents is delivered to the output ports. Present micro-mixer is consisted of a rotor with shape of triangle column, a blending chamber and several inlet and outlet ports. The geometry of blending chamber is designed to make the rotor can be freely internal rotated with a constant eccentricity ratio. When the shape of the blending chamber and the rotor are fixed, the effects of rotating speed of rotor and the relative locations of ports on the mixing efficiency are numerical studied. The governing equations are unsteady, two-dimensional incompressible Navier-Stokes equation and the working fluid is the water. The species concentration equation is also solved to reveal the mass transfer process of reagents in various regions then to evaluate the mixing efficiency. The dynamic mesh technique was implemented to model the dynamic volume shrinkage and expansion of three individual sub-regions of blending chamber when the rotor conducted a complete rotating cycle. Six types of ports configuration on the mixing efficiency are considered in a range of Reynolds number from 10 to 300. The rapid mixing process was accomplished with the multiple vortex structures within a tiny space due to the equilibrium of shear force, viscous force and inertial force. Results showed that the highest mixing efficiency could be attained in the following conditions: two inlet and two outlet ports configuration, that is an included angle of 60 degrees between two inlets and an included angle of 120 degrees between inlet and outlet ports when Re=10.

Authors:

• Y. C. Liou
• J. M. Miao
• T. L. Liu
• M. H. Ho

Keywords:

• active micro-mixer
• CFD
• mixing efficiency
• ports configuration
• Reynolds number
• Wankle-type rotor

References:

[1] Yongdae Kim, Jongkwang Lee and Sejin Kwon, "A novel micro-mixer
with a quasi-active rotor: fabrication and design improvement," Journal
of Micromechanics and Microengineering, Vol. 19, No. 10, 105028, pp.
1-9, 2009
[2] Liu R. H., Stremler M.A., Sharp K. V., Olsen M. G., Santiago J. G.,
Adrian R. J., Aref H., and Beebe D. J., "Passive mixing in a
three-dimensional serpentine microchannel," J. Microelectromech. Sys.,
vol. 9, pp. 190-197, 2000
[3] N. T. Nguyen., and Z. Wu., "Micromixers: a Review," Journal of
Micromechanics and Microengineering, Vol. 15, pp.1-16, 2005.
[4] Miyake R., Lammerink T. S. J., Elwenspoek M., and Fluitman J. H. J.,
"Micro mixer with fast diffusion," Proc. MEMS-93, 6th IEEE Int.
Workshop Micro Electromechanical System (San Diego, CA), pp. 248-53,
1993
[5] Stroock, A. D., Dertinger, S. K., Ajdari, A., Stone, H. A., and Whitesides,
G. M., "Chaotic mixer of microchannels," Science, 2002. 295: pp.
647-651
[6] Kim, D. S., Lee, S. W., Kwon, T. H., and Lee, S. S., "A barrier embedded
chaotic mixer," Journal of Micromech. Microeng., 2004. 14: pp.
798-805
[7] C. A. Cortes-Quiroz., A. Azarbadegan., and E. Moeendarbary., "An
efficient passive planar micromixer with finshaped baffles in the tee
channel for wide Reynolds number flow range,"World Academy of
Science, Engineering and Technology, vol.61, pp. 170-175, 2010
[8] Mubashshir Ahmad Ansari., Kwang-Yong Kim., Khalid Anwar., and Sun
Min Kim., "A novel passive micromixer based on unbalanced splits and
collisions of fluid streams," Journal of Micromechanics and
Microengineering, Vol. 20, No.5, 005007, pp. 1-10, 2010.
[9] Ying Lin., Xinhai Yu., Zhenyu Wang., Shan-Tung Tu., and Zhengdong
Wang., "Design and evaluation of an easily fabricated micromixer with
three-dimensional periodic perturbation,"Chemical Engineering Journal,
Vol. 171, Issue 1, pp. 291-300, 2011
[10] Han E. H. Meijer, Mrityunjay K. Singh, Tae Gong Kang., Jaap M. J.
Toonder., and Patrick D. Anderson., "Passive and Active Mixing in
Microfludic device," Macromolecular. Symposia., No. 279, pp. 201-209,
2009.
[11] Yang, Z., Goto, H., Matsumoto, M., and Yada, T., "Micromixer
incorporated with piezoelectrially driven valveless micropump," Micro
Total Analysis Systems-98, pp. 177-180, 1998.
[12] Yang, Z., Goto, H., Matsumoto, M., and Maeda, R., "Ultrasonic
Micromixer for Microfluidic Systems," MEMS 2000, The 13th Annual
International Conference, 2000.
[13] Li Kang-Hsis, "A Study of Active Micro-mixer Based on Pulsating Inlet
Flows" Master-s thesis, Tainan, Taiwan (2006).
[14] Shu Hao-Chieh, "Numerical Study of Mixing Enhancement with
Time-Dependent Flowrate Modulation in Micromixers", Master-s thesis,
Taichung, Taiwan (2006)
[15] Chang Chih-Hsiang, Liu Da-Sheng, Kuo Lung-sheng, Chen Bing-hui,
"The Improvement of the Mixing Efficiency of Semi-active
Micro-mixers by Nano-magnetic Fluids", the 24th National Colloquium
held by Chinese Mechanical Engineering Association, Chungli, Taoyuan,
Taiwan, pp. 5148 - 5153.
[16] Wu Tzung-Hsin, Shao Yun-Lung, Huang Po-Cheng, Cheng Tsung-Chieh,
"The Manufacture and Research of Micro-mixers", Journal of
Nano-communication, Vol. 12, Issue 1, pp. 21-27.
[17] Jongkwnag Lee and Sejin Kwon., "Mixing efficiency of a
multilamination micromixer with consecutive recirculation zones,"
Journal of Chemical Engneering Science, vol. 64, pp. 1223-1231, 2009
[18] Lee, S. W., Kim, D. S., Lee, S. S., Kwon, T. H., "A split and
recombination micromixer fabricated in a PDMS three-dimensional
structure," Journal of Micromechanics and Microengineering, vol. 16, pp.
1067-1072, 2006
[19] Hardt, S., Schönfeld, F., "Laminar mixing in different interdigital
micromixers: II, Numerical simulation," A.I.Ch.E. Journal, vol. 49, pp.
578-584, 2003.
[20] Engler M., Kockmann N., Kiefer T., and Woias P., "Numerical and
experimental investigations on liquid mixing in static micromixers,"
Chemical Engineering Journal, vol. 101, pp.315-322, 2004