Thermal Diffusion and Particle Separation in Ferrocolloids

Abstract

Results of experiments on thermal diffusion in ferrocolloids are discussed in the paper. The Soret coefficient is evaluated from measurements of particle separation in thermodiffusion column. To interpret the separation curves measured in the presence of a magnetic field, the column theory is modified taking into account for MHD effects of free convection. It is shown that the Hartmann effect in hydrocarbon based colloids as well in ionic magnetic fluids does not influence significantly the particle separation dynamics. From unsteady separation curves positive values of the Soret coefficient of surfacted particles in tetradecane based colloids are calculated. Such direction of particle transfer toward decreasing temperatures agrees with the slip-velocity theory of thermophoresis of lyophilized particles. An uniform magnetic field oriented normally to the temperature gradient causes an increase in thermal diffusion coefficient. The results agree qualitatively well with hydrodynamic theory of particle thermo magnetophoresis.KeywordsThermal DiffusionMagnetic FluidTransversal Magnetic FieldUniform Magnetic FieldHartmann NumberThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.