Transport of Aqueous and Organic Fluids through Micro- and Nanoporous Media
Creators: Islam, Md Minhajul
Publisher: name: University of Alberta Library
Year: 2022

<p>In predicting oil and gas recovery, researchers develop models primarily focusing on macro- or milli-scale flows by applying Navier-Stokes types solutions and no-slip boundary conditions. They compare or cross-check their models to known experimental results available in the literature for larger pore scales. In contrast, much less experimental data is available to use in modelling nanoscale flows, which is very important in oil and gas recovery applications. Moreover, porous media flow in smaller scales is also important in other fields of science, for example, in chromatography (with smaller packing particles), nanofluidic diode, fuel cells and other devices. Few theoretical and experimental studies are found in the literature on fluid flow in nanofluidic structures. However, a wide range of flow enhancement results with up to several orders of magnitude discrepancies is present between theoretical and experimental works. Therefore, realizing the need for more experimental data in the case of smaller-scale flows, we focused on studying the flow behaviour of aqueous and organic viscous liquids through silica-based micro and nanoporous structures with the fundamental concern of whether the no-slip boundary condition, a macroscale assumption, can correctly describe the micro and nanoscale flow properties for various combinations of fluid-solid surface interaction. The effect of pore sizes in porous media and the surface interaction between a viscous liquid and porous bed material on micro- and nanofluidic flow phenomena is reported here. We develop micro and nanoporous media by packing nonporous silica microspheres (300-2000 nm particle diameter) inside fused silica microcapillary tubes. The interconnected pores among the silica particles form the micro- or nanofluidic channels for fluid flow. A time-of-flight, photobleaching velocity measurement technique is employed to determine the linear flow velocity of a viscous liquid flowing through a porous media. Throughout the applied pressure range (100-6000 psi), the Newtonian fluids, irrespective of their wetting property, exhibit a laminar flow pattern (Re &lt;&lt;1), which validates the applicability of porous media flow equations (Darcy and Kozeny-Carman equations) for our porous systems (39.5 to 340 nm pore radius). The pressure-driven flow experiments for a non-wetting liquid (n-octane) through silica micro- or nano-porous media confirm the existence of slip flow. The more viscous 1-octanol, which has both wetting (polar hydroxyl group) and non-wetting (non-polar octyl group) parts in its structure, also experiences slip flow in the silica micro- and nanoporous beds. However, the extent of slip flow with 1-octanol is less pronounced than n-octane, though both molecules have the same length of hydrophobic alkyl chain in their structures. For both liquids, the flow enhancement is more noticeable in the nanoporous beds than the microporous ones. Slip length increases with the decreasing pore diameter of the porous media. The silica porous bed with the smallest pore radius gives the maximum flow rate enhancement, where the slip lengths for the n-octane and 1-octanol are 18.1 ± 1.0 and 7.4 ± 0.3 nm, respectively. This research fills a large gap in the literature involved for the flow of organic fluids through hydrophilic nanoporous media, and it will be useful for the future refinement of theoretical models of micro and nanoscale porous media flow.</p>