Measurement of the Soret and diffusion coefficients for benchmark binary mixtures by means of digital interferometry

Abstract

We report on the development of the optical digital interferometry (ODI) technique for measuring diffusion and Soret coefficients. The unique feature of this method is that it traces the transient path of the system in the entire two-dimensional cross section of a cell. In this way, it is applicable not only for measurements of Soret coefficients, but also for studying diffusive transport mechanism and convection. Presently, this method is not widely used and, in our view, not because of fundamental limitations but rather due to a lack of properly developed postexperimental procedures of the raw data analysis. Thus, in this paper our attention is focused on the successive analysis of different steps: the fringe analysis, the choice of reference images, the thermal design of the cell, and multiparameter fitting procedure. Using the ODI technique, we have measured the diffusion and the Soret coefficients for three binary mixtures composed of dodecane (C 12 H 26 ), isobutylbenzene, and 1,2,3,4-tetrahydronaphtalene at a mean temperature of 25 • C and 50 wt. % in each component. These measurements were compared with their benchmark values and show an agreement within less than 3%.

Non-equilibrium molecular dynamics simulations of the transient Ludwig-Soret effect in a binary Lennard-Jones/spline mixture

“…al. [32], and Mialdun and Shevtsova [17] The analysis shown here is based on measuring the composition and temperature as function of distance from the heat source for fixed time. In an experimental setup, it may be more convenient to measure the composition as function of time for a fixed distance from the heat source.…”

“…Other excellent reviews were written by Srinivasan and Saghir [11], Platten [12], and Wiegand [13]. The methods that are of most interest in the context of the present paper are fast methods that work at very small length scale, such as optical beam deflection [14], thermal diffusion forced Rayleigh scattering [15,16], and optical digital interferometry [17].…”

Mass transport properties of the tetrahydronaphthalene/n-dodecane mixture measured by investigating non-equilibrium fluctuations

“…the so-called contrast factors of the analyzed mixture [27,28]. An alternative method that is not based on an optical analysis is the thermo-gravitational column technique [29], in which the sample is let evolve to the steady state of the separation, after which small volumes of the fluid mixture at different heights are physically picked-up and analyzed in order to directly measure the value of the concentration as a function of the vertical coordinate, thus leading to a measurement of the thermodiffusion coefficient D T , but without any information about the mass diffusion coefficient D. Other interesting techniques from the optical domain include optical digital interferometry (ODI) [30], thermal diffusion-forced Rayleigh scattering (TDFRS) [31], thermal lens [32] and other techniques that have been reported in the literature [17,28,[33][34][35].…”

Thermodiffusion of the tetrahydronaphthalene and dodecane mixture under high pressure and in porous medium

“…On the contrary, in a second stage the concentration kinetics becomes dominant in generating phase difference change. Hence, the two effects are decoupled enough to clearly distinguish the solutal contribution from the temporal point of view [17][18][19][20][21].…”

“…During the second stage, when the concentration variation becomes dominant, assuming no convection perturbs the process, the concentration difference of the densest component as a function of time is [20,21]:…”