Dynamics of thermodiffusive separation of ferrocolloids in vertical columns: the effect of solute buoyancy

E. Blums¹ - S. Odenbach²

¹ Institute of Physics, University of Latvia, Salaspils-1, LV-2169, Latvia
² ZARM, University of Bremen, Am Fallturm, D-28359 Bremen, FRG

Abstract
The paper deals with an approximate analysis of separation dynamics in thermodiffusion column for liquids of high Soret coefficients and of different densities of the solute components. The analytical problem consists of the quasi-steady one-dimensional equation of mixed thermal and Soret driven MHD convection and the unsteady two-dimensional convective mass transfer equation. Under the assumption of independence of the vertical concentration gradient on vertical coordinate the problem is solved analytically. For initial regime the separation curves agree well with the dependence calculated in a boundary layer approximation of the unsteady concentration profile across the channel. The solute buoyancy causes a significant increase in the relaxation time of reaching the steady state of separation process. The obtained analytical dependencies allow the evaluating of Soret coefficients from the measured separation curves. Figs 5, Refs 9.