THE INFLUENCE OF THE TYPE OF FLOW ON THE ORTHOKINETIC COAGULATION RATE

The flow-induced behavior and Brownian coagulation behavior of a polys tyrene latex were studied using a Coulter counter. The coagulation rat es in Couette flow (either laminar or Taylor vortex flow), laminar pip e flow, and isotropic turbulent flow were compared with theoretical mo dels. It was shown that the orthokinetic coagulation rate in laminar C ouette flow, pipe flow, and isotropic turbulent flow can be described on the basis of existing theory but only when using a lower effective Hamaker constant than predicted from experiments on perikinetic coagul ation. This means that the orthokinetic coagulation rate is lower than that predicted by theory. This agrees with measurements performed by other investigators. For Taylor vortex flow, however, the experimental dependence of the stability ratio on the parameter N-SA = 6 pi eta a( 3) gamma/A, where a is the particle radius, gamma is the shear rate, a nd A is a Hamaker constant, is different from that predicted by theory . From experiment and theory it is clear that at equal energy dissipat ion the coagulation rate is highest for the isotropic turbulent flow. (C) 1995 Academic Press, Inc.