Inertial migration based concentration factors for suspensions of Chlorella microalgae in branched tubes.

When a dilute suspension flows in the laminar regime through a tube, under certain conditions the suspended particles migrate radially to an equilibrium radial position. Branched tubes can use this radial concentration distribution to concentrate dilute suspensions. Suspensions of microalgae, Chlorella vulgaris, were pumped through tubes of various diameters for tube Reynolds number ranging from 47-1839 and photographed. Upstream particle concentration profiles were obtained by image analysis of the photographs. The dividing stream surfaces in branched tubes were obtained from the three-dimensional numerical solutions of the Navier-Stokes equations for steady, laminar, and homogeneous flow through tubes having one and two orthogonal branches. Concentration factors for Chlorella suspensions in branched tubes, predicted by a general method, fall in the range of 1.0-1.3.