Contribution of the Thermal and Molecular Diffusion to Convection in a Vertical Porous Cavity

Abstract

In a uniform mixed binary mixture, when a temperature gradient is applied there appears a composition gradient. This thermal diffusion effect is named the Soret effect, and the ratio of the thermal diffusion coefficient to the molecular diffusion coefficient is known as the Soret coefficient, see Soret [20]. Usually, in a binary mixture, the lighter component migrates to the hot side. Theoretical developments related to the calculation of the molecular, thermal and pressure diffusion coefficients have received much attention by different researchers [2, 4, [5, 8–10, 16,17,19] in this field. Among these, Riley and Firoozabadi [16], Shukla and Firoozabadi [19] and Ghorayeb and Firoozabadi [8–10] using the irreversible thermodynamic theory, were able to extend the work of de Groot [4]. De Groot developed an analytical relation between the thermal, molecular and pressure diffusion coefficients and the properties of the fluid mixture, such as the temperature, pressure and composition. The advantage of this approach is that the Soret coefficient is calculated at each point of the cavity grid and all diffusion coefficients are completely defined. Compared with other approaches, such as Rutherfood and Roof [17], the theoretical prediction of this approach is much closer to experimental data, especially for non-ideal mixtures, such as hydrocarbon mixtures.