Molecular and Thermal Diffusion Coefficients Of n-Dodecane, Isobutylbenzene and Tetrahydronaphtalene Hydrocarbon Mixtures in Porous Media

Mustafa Khawaja

doi:10.32920/ryerson.14647677

Abstract

The thermal diffusion phenomenon was studied in detail by utilizing mixtures consisting of normal alkenes and two aromatics (n-Dodecane, Isobutylbenzene and 1,2,3,4-Tetrahydronaphtalene) based on comparison with available experimental data. This study presents the first report of a comparison of thermal diffusion coefficients of a ternary hydrocarbon mixture with experimental data in the literature. In addition to thermal diffusion coefficients, molecular diffusion coefficients are also measured and compared with Benchmark experimental values for three binary mixtures. Furthermore, molecular and thermal diffusion coefficients for three binary mixtures are used to correlate and estimate the thermal diffusion coefficients in the ternary hydrocarbon mixture. The thermo-solutal convection in porous media was simulated numerically using the Firoozabadi model in order to investigate the composition variation due to the processes of thermal diffusion and convection. Finally, a multi-porosity/multi-permeability model was utilized to further analyze the processes of thermal diffusion and convection in fractured porous media.

Highlights

Fig u r e 3 : D e n s it yvariat io nasfunct io n o f THN percentagefor THN-IBB m ix t u r e
It was found that, when the thermal conductivities of the fluid and solid matrix are of the same magnitude, the Soret coefficients do not differ significantly from the case of the porous medium to that o f the free fluid. These findings indicate that the contribution of the solid matrix in a porous medium on the two mass fluxes— namely the isothermal mass flux caused by the gradient o f chemical potential, and the thermodiffusive mass flux caused by the temperature gradient is the same as those in the free fluid
The results showed that when pressure was equal, there was very little flow interaction between the fracture and the rest of the porous medium

Summary

Introduction

Firoozabadi’s model is based on the thermodynamics theory o f an irreversible process. It develops analytical relations between the thermal, molecular and pressure diffusion coefficients, and the fluid properties including temperature, pressure, density, fiigacity, and viscosity. Firoozabadi's model has been widely applied in hydrocarbon mixtures, as well as polar mixtures such as water-ethanol and water-methanol. In doing so, it has shown success in predicting the thermal and molecular diffusion coefficients. For the case of hydrocarbon mixtures, the properties of the fluid mixture at equilibrium states are evaluated using the Peng-Robinson (PR) equation of state. The Cubic Plus Association (CPA) equation o f state is used

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Conclusion