Feasibility study on concentration of slurry and classification of contained particles by microchannel

The feasibility Of a newly developed micro-separator/classifier is examined numerically and experimentally. The main section of the device is a curved channel with a rectangular cross-section, which has a bifurcation at one end. The width, depth and curvature radius of the channel are 200 mum, 170 mum and 20 mm, respectively. This geometry creates secondary flow patterns called Dean vortices. The concentration and classification are thought to be caused by the balance of high centrifugal acceleration that traps particles near outer wall and the intensity of Dean vortices that enhance mixing and re-dispersion of particles in the secondary flow field. Although the residence time is extremely short because of the channel size, it is confirmed by numerical simulations that secondary flow patters are established immediately after entering the curved section and that the channel is long enough that several circulations are expected for re-dispersion. Suspensions, whose weight concentration is 0.06 wt.%, are prepared as test fluids using ion-exchanged water and acrylic polydisperse particles whose average diameters are 7, 10 and 20 mum, respectively. It is experimentally confirmed that the structure results in concentration and classification for the all particles in the Re range of 150-600 (the De range of 10-40). It is also verified that the efficiencies increase with the particle size. (C) 2003 Elsevier B.V. All rights reserved.