Abstract:Background. The study considers the thermoelectrokinetic effect, which belongs to a specific class of cross transport phenomena occurring under the simultaneous influence of three thermodynamic forces. The influence of natural convection on the steady-state fluid temperature and velocity fields formed in the presence of the thermoelectrokinetic effect is evaluated. The method of suppression of natural convection in the measurement of thermoelectrokinetic EMF is developed and the corresponding study in aqueous solution of tannin is carried out. Materials and methods. Assessment of the influence of natural convection on the temperature and velocity distributions of the liquid is carried out on the basis of experimental measurements of its temperature field using a laboratory thermal imager and calculations of the corresponding fields on the basis of numerical solution of the Navier-Stokes, heat conduction, and continuity equations by the finite element method. Measurement of thermoelectrokinetic EMF in colloidal tannin solution with suppression of free convection is carried out using a modified experimental setup in which the direction of the temperature gradient is reversed. Results. On the basis of numerical modeling and experimental measurements, the temperature and velocity distributions of the liquid in the U-shaped tube are obtained. The results of numerical calculations agree with the results of in-situ experiment. It is shown that in the classical formulation of the experiment to measure thermoelectrokinetic EMF when heating the liquid in a U-shaped tube from below, it is not possible to create a significant temperature drop, on which the value of thermoelectrokinetic EMF depends. The thermoelectrokinetic EDS of colloidal tannin solution was measured under conditions of suppressed convection. Under these conditions, the EMF reaches a significant value. Conclusions. Thus, natural convection significantly affects the manifestation of the thermoelectrokinetic effect in liquid electrically conducting media, and its suppression contributes to the formation of higher temperature gradients. Due to this, the value of thermoelectrokinetic EMF increases.
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