Mixing of shear-thinning fluids in a zigzag planar microchannels with baffles

• Main Authors: Yi-TsungYeh, 葉宜璁
• Other Authors: C.Y. Wu
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/59166046862100198896

碩士 === 國立成功大學 === 機械工程學系碩博士班 === 98 === In this work, we investigate the mixing behavior of shear-thinning fluids in a zigzag planar microchannel with baffles. The shear-thinning fluids considered in this work are the aqueous solution of Carboxymethyl Cellulose Sodium. The power-law has been employed for modelling the relation between shear stress and shear rate of the shear-thinning fluid. Then, we apply the commercial package, CFD-ACE+, to simulate the 3-D flow field and mixing behavior in the micromixer. Numerical simulation is performed for various distances between bends, flow rates, fluid properties and the positions of baffles to investigate the effects of these parameters on the mixing behavior in the micromixer. The fabrication process of the micromixer includes applying the photolithography method to fabricate SU-8 mold, replicating PDMS (polydimethysiloxane) mold and bonding the PDMS with a cover glass. Add Rhodamine B to one of the inlet fluids of the micromixer ; the fluid mixing is observed by a laser confocal spectral microscope, Leica TCS SP2. Reasonable agreement of simulation and experiment results is found for the cases considered. From the results of this work the following trends may be observed. (i) Adding buffles to the channel wall before bending enhances the mixing of fluids most significantly. (ii) As the Reynolds number increase, the mixing efficiency increases. (iii) An optimum distance between bends can be found for the mixing of fluids. (iv) The increase of the Reynolds number enlarges the discrepancy between shear-thinning fluid and Newtonian fluid.