چكيده به لاتين
In this research, mass transfer of an analyte through electroosmotic flow of a viscoelastic fluid within a slit microchannel is investigated. The study of mass transfer was performed based on “hydrodynamic dispersion” or “Taylor dispersion” analysis. First, an analytical solution for electrical potential distribution and an analytical solution for velocity distribution were introduced by means of Debye-Hückel linearization. Then by utilizing velocity distribution equation beside few limited simplifying assumptions, the concentration distribution equation was obtained that ultimately led to the calculation of effective diffusion coefficient. Mentioned analytical solution is then compared with numerical solution of above coupled equations and we found that the Debye-Hückel linearization predicts the analytical solution desirably with imposing less than 1% of error. Afterwards, by employing a completely different physics-based point of view and also using Taylor dispersion theory, the details of an analyte dispersion through viscoelastic fluids in a slit microchannel was discussed. Accordingly, a model was developed to predict the behavior of hydrodynamic and consequently the physics of mass transport. In this regard, a band of uncharged solute was injected into the channel and its dispersion was monitored by averaging concentration across any cross section. It was found that, both analytical and numerical approaches were in a good agreement despite their fundamental differences and average error was about 8%. As an example, for Κ=100, ϵWe^2=10 and Pe=10, amounts of the dimensionless effective diffusion coefficient yield from analytical approach and modeling were equal to 1.0337 and 1.0203 respectively. This indicates that the simplifying assumptions to provide analytical solution are physically reliable. Variations of average concentration at different time intervals reveal that the developed model for electroosmotic flow can be used for separation and/or transmit of liquid by multiple injections. It was also observed, the effective diffusion coefficient is a decreasing function of Debye-Hückel parameter and an increasing function of both elasticity level and Péclet number.