Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
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Item An experimental study of drying in porous media in novel 2D micromodels with dual porosity(Montana State University - Bozeman, College of Engineering, 2024) Habib, Md Ahsan; Chairperson, Graduate Committee: Yaofa LiDrying of porous media is pervasive in numerous natural and engineering processes, such as oil recovery, CO 2 storage, and critical zone science. Drying is essentially a multiphase flow process, where the liquid phase evaporates and is displaced/replaced by the gaseous phases, as vapor diffuses out of the porous structure. In terms of pore structure and other physical characteristics like porosity and permeability, many porous matrices exhibit multi-scale heterogeneity. For instance, in critical zone, soil is often viewed as a hierarchical organization: primary particles form aggregates, which in turn form macroaggregates, effectively leading to a dual-porosity medium. Numerous activities, including gases and water transport, are known to be controlled by the resultant multiscale flow dynamics and inter-/intra-aggregate interaction during drying. However, the fundamental physics underlying drying of porous media with dual porosity is not well understood from a fluid mechanics perspective. In this work, a novel 2D microfluidic device fabrication technique has been developed. To study the multi-phase flow of air and water, emphasizing the multi-scale interaction, pore structure, and role of film flows, three distinct types of microfluidic devices have been fabricated, which bear the innovative three-layer glass-silicon- glass architecture, providing precise structural control and excellent optical access from both top and bottom. An innovative dual-magnification imaging technique has been introduced adapted for micro-PIV and epi-fluorescent microscopy which offers insightful information about the flow dynamics at both the micro- and macro-scales concurrently. In this thesis, two distinct types of experiments are outlined, focusing on diffusion-driven drying and flow-through drying, utilizing three diverse micromodels characterized by varying porous structures and distributions. The experimental results have presented the overall drying dynamics observed in different micromodels, each featuring unique porous configurations. The impact of porous geometry and external flow conditions on drying rate and associated pore-scale physics is thoroughly examined. The findings encompass a comprehensive overview of micro-macro pore interactions, as evidenced by separated saturation distribution, displacement rates, and other pertinent flow parameters. The findings have reflected the influence of pore geometry, distribution, hydraulic connectivity, and film flow on the observed effects.Item NMR characterization of unfrozen brine vein distribution and structure in frozen systems(Montana State University - Bozeman, College of Engineering, 2022) Lei, Peng; Chairperson, Graduate Committee: Sarah L. Codd; This is a manuscript style paper that includes co-authored chapters.The liquid vein network (LVN) that forms in the interface of ice crystals or particles exists in frozen porous media due to the freezing point depression. The distribution and structure of the LVNs are dynamic due to the ice recrystallization phenomenon. In ice alone, the LVNs formed by the ice crystal interfaces can be characterized as a porous medium in terms of surface to volume ratio (SV /) and the tortuosity (alpha).The presence of solid particles or ice-binding proteins (IBPs) make the frozen system much more complex. The research presented uses nuclear magnetic resonance (NMR) experimental techniques, including magnetic resonance imaging (MRI), relaxation and self-diffusion measurements, to study the development of the LVNs in complex frozen systems containing solid particles or IBPs. Poly-methyl methacrylate (PMMA) particles of diameters 0.4, 9.9, and 102.2 microns are used with brine solution concentrations of 15, 30, and 60 mM Magnesium chloride (MgCl 2) to simulate complex frozen systems. The dynamic rearrangement with time of LVNs can be studied as a function of temperature, MgCl 2 concentration, and PMMA particle size. The results indicate that small solid particles dominate the structure dynamics while in larger solid particle packed beds the solute effect dominates. This behavior is quantified by determination of SV / and alpha from NMR relaxation and diffusion data. Additionally, IBP produced from the V3519-10 organism isolated from the Vostok ice core in Antarctica is added to ice samples frozen from 30, 60 and 120 mM MgCl 2 solution to investigate its influence on LVNs over months of aging. The interplay of the solute and biological effects is complicated but it appears the biological effect is more pronounced at lower salt concentrations. The data provide a basis for eventual combination of salt, IBP and solid particulate studies. The result of MRI, relaxation and self-diffusion measurements indicate the inhibition of ice recrystallization as a function of particle size, MgCl 2 concentration and the presence of IBP. The non-invasive data presented along with calibration of the relaxation experiments with self-diffusion experiments, demonstrate the continued extension of NMR techniques developed from porous media to frozen porous media and ice LVN structure.Item Experimental characterization of pore-scale capillary pressure and corner film flow in 2D porous micromodels(Montana State University - Bozeman, College of Engineering, 2023) Molla, Razin Sazzad; Chairperson, Graduate Committee: Yaofa LiMultiphase flow in porous media is ubiquitous in natural and engineering processes. A better understanding of the underlying pore-scale physics is crucial to effectively guiding, predicting and improving these applications. Traditional models describe multiphase flows in porous media based on empirical constitutive relations (e.g., capillary pressure vs. saturation), which, however, are known to be hysteretic. It has been theoretically shown that the hysteresis can be mitigated by adding new variables in the functional form. However, experiments are still needed to validate and further develop the theories. In particular, our understanding of capillary pressure characterization and numerous pore-scale mechanisms is still limited. For instance, during capillary pressure measurement, fluid phases become disconnected, making the bulk pressure an inaccurate measure for the actual capillary pressure. In a strongly wetting medium, wetting phase always remains connected by corner films, through which trapped water continues to drain until a capillary equilibrium is reached, but the effects of corner film flow are minimally characterized. In this thesis, two different experiments are presented. In the first experiment, we focused on the capillary pressure characterization and the effect of measurement resolution. Microscopic capillary pressure along with other geometric measures are characterized during drainage and imbibition. By strategically varying the pressure at the boundary, different equilibrium states were achieved and imaged at four different magnifications (i.e., 2, 1.25, 0.5, 0.25 micron/pixel). In the second experiment, we for the first time characterized the corner film flow again during drainage and imbibition condition employing particle image velocimetry. Overall, our results suggest that the calculated macroscale pressure P c and the bulk pressure drop agree reasonably well when only interfaces associated with the connected phases are considered. A spatial resolution of 2 micron/pixel seems to sufficiently resolve the interface, and further increasing the resolution does not have a significant impact on the results. Additionally, corner film flow was found to be an active transport mechanism. During drainage, trapped water is continuously drained over time via thin film, whereas during imbibition snap-off events are enhanced by wetting films. These observations call for future studies to carefully treat corner film flows when developing new predictive models.Item A structural analysis of zeolite-templated carbons(Montana State University - Bozeman, College of Letters & Science, 2022) Taylor, Erin Elizabeth; Chairperson, Graduate Committee: Nicholas P. StadieZeolite-templated carbons (ZTCs) are a distinct class of porous framework materials comprised of a three-dimensional pore network contained between atomically thin, polycyclic hydrocarbon walls. This class of materials arose from the goal to develop carbon- based frameworks with ordered, homogeneous microporosity (see Chapter 1), as opposed to activated carbons where the pore network is random. It has more recently been suggested that zeolite-templating may be a viable synthetic route to carbon schwarzites, an elusive class of theoretical materials, which follow triply periodic minimal surfaces and are predicted to have many fundamentally interesting properties. Herein we show that while experimentally synthesized ZTCs (see Chapters 2 and 3) are too amorphous to be considered schwarzites, understanding the current structural features of ZTCs may be the key to finally isolating a schwarzite via zeolite-templating. The experimentally relevant open- blade model developed in our work predicts paramagnetism of ZTC materials (see Chapter 5); superconducting quantum interference device measurements on archetypical ZTC materials confirms this prediction, highlighting the unique nature of spin polarization in porous carbon materials. While the current ZTC structure resembles an open-blade, generating a closed- tube schwarzite-like ZTC variant may be accessible by tuning the catalytic activity of the zeolite template pore walls. In Chapter 6, alkali metal exchange is explored as a route to strengthen cation-? interactions between the growing ZTC framework and zeolite template in an attempt to achieve a more schwarzite-like ZTC. LiY-templated ZTCs show beginning signs of conversion to a closed-tube structure. Lastly, recent benchmark computational studies suggest that nitrogen-doping of open-blade porous carbon surfaces has a significant, beneficial effect on the binding energy toward methane: a strengthening by up to 3 kJ mol -1 over pure carbon. The work presented in Chapter 7 identifies optimal conditions to achieve nitrogen-doped ZTCs with N-contents ranging from 0-9 at%. Therein, we show that indeed high-pressure (100 bar) methane adsorption characterization of nitrogen-doped ZTCs exhibit an increased methane binding energy of 1.3 kJ mol -1, validating the theoretical predictions.Item Design and fabrication of membrane-based pressure sensor for capillary pressure measurement in micromodels(Montana State University - Bozeman, College of Engineering, 2021) Raventhiran, Nishagar; Chairperson, Graduate Committee: Yaofa LiPressure is a fundamental quantity in virtually all problems in fluid dynamics from macro-scale to micro/nano scale flows. Although technologies are well developed for its measurement at the macro-scale, pressure quantification at the microscale is still not trivial. Yet, precise pressure mapping at microscale such as in microfluidics is imperative in a variety of applications, including porous media flows and biomedical engineering. In particular, pore-scale capillary pressure is a defining variable in multiphase flow in porous media and has rarely been directly measured. To that end, this study aims to design and fabricate an on-chip sensor that enables quantification of capillary pressure in microfluidic porous media, called micromodels. The micromodel is fabricated in polydimethylsiloxane (PDMS) using soft lithography with a thin membrane incorporated that deflects with pressure variations in the fluid flow. Employing a microscope coupled with a high-speed camera and the astigmatism particle tracking principle, precise pressure measurement is achieved with an accuracy of ~ 60Pa. This sensor is then applied to characterize the viscous pressure drop in single phase flows, and the capillary pressure in a water-air multiphase in microchannels, and good agreement is obtained between the sensor measurement, theoretical values and measurements employing a commercial pressure transducer. This thesis provides a novel method for in-situ quantification of local pressure and potentially 2D pressure field in microfluidics and thus opens the door to a renewed understanding of pore-scale physics of multiphase flow in porous media.