Non-isothermal separation of ferrofluid particles through grids: Abnormal magnetic Soret effect
Abstract Nanoparticle transport through thin non-isothermal ferrofluid layer between permeable walls is investigated. The transient mass flux is determined from measurements of particle concentration changes in two fluid chambers of different temperatures which are attached on both sides of the layer. Experiments are performed employing fluid samples of small ordinary magnetic Soret effect, which is detected by thermal grating technique. The separation measurements say that a magnetic field, aligned along a temperature gradient, causes a remarkable increase in the mass diffusion coefficient and a simultaneous decrease in particle thermodiffusion mobility. It is proposed that the observed ef…
Experimental research of surfaced nanoparticle thermal transport in a porous medium
Abstract Experimental research on thermally induced nanocolloid transport in a porous environment is presented. Addition of excess surfactant to a colloid with dispersed phase made of surfaced nanoparticles results in a decrease of effective Soret coefficient in a porous environment. It is shown that with sufficient amounts of surfactant added, this effect extends to a reversal of nanoparticle thermophoretic transport direction, and that the effect shows a tendency of saturation. A mechanism of thermal transport that involves slip velocity of surfactant molecules appearing near pore walls is evaluated as a possible cause of the decrease of Soret coefficient. Effects of temperature on partic…
Non-isothermal mass transfer of ferrocolloids through porous membrane
Abstract The present paper deals with transport properties of ferrofluid nanoparticles in non-isothermal capillary-porous layer. Experiment establishes that the temperature difference, which is applied across the layer, induces a thermoosmotic pressure gradient directed toward increasing temperature. The measurement results are interpreted in a frame of phenomenology of linear irreversible thermodynamics. The transport coefficients are evaluated comparing the measured separation curves with approximate solution of the corresponding mass transfer problem.