In order to increase the efficiency of an adsorption heat pump system, a stratified thermal heat storage can be used to enable regeneration of heat between the different phases of the process. It’s crucial to avoid mixing and to keep layers intact inside the storage tank. As mixing generally occurs during charging and discharging, the aim of this project is minimizing these effects by introducing porous media into the region of the inlet ports. The impact of porous media on laminar and turbulent flow inside stratified thermal storage tanks is qualitatively and quantitatively investigated. Two thermal storage tanks are examined in which polyurethane foam is used as porous medium. Numerical results are compared with experimental results in order to study the effects of the porous medium and validating numerical models. For the quantitative investigation, equations describing flow in porous media are obtained and implemented into computational fluid dynamics (CFD) models. Simulations of storage tanks are performed by means of 2D-axisymmetric domain models. Tanks are investigated qualitatively using two methods; background oriented schlieren (BOS) and ink colored inlet water, in order to visualize flow and mixing inside tanks. Thermo elements are also used to measure temperatures at given locations. Results from experimental- and numerical cases show how porous media influence stratification in a positive way. Flow visualizing experiments (using ink and BOS) showed decrease in thermocline thickness when using polyurethane foam. This could also be seen for the numerical cases. Experimental- and numerical investigations of the ability of porous media to damp turbulence intensity and kinetic energy, showed a positive effect. Further improvements have to be done, adjusting numerical models to experimental results. Comparison between the numerical- and experimental results showed differences both in flow fields and temperature distributions. Results indicate however, that porous media could play an increasing role in the development of stratified heat storages. / Stratifierade värmelagringstankar kan användas för att öka effektiviteten hos adsorptionsvärmepumpsprocesser genom att möjliggöra regeneration av värme mellan faserna. För att dessa effektivt ska kunna användas är det viktigt att temperaturskikt hålls intakta inuti lagringstankarna och att omröring undviks. Då omröring oftast uppstår vid laddning och tömning av lagringstankarna är målet för det här projektet att minska denna effekt genom att använda porösa medier vid deras inlopp. Porösa mediers inverkan på flöden och temperaturskikt inuti värmelagringstankar undersöks både kvalitativt och kvantitativt i det här projektet. Två tankar undersöks där polyuretanskum används som poröst medium. Numeriska resultat jämförs med experimentella för att undersöka effekterna av de porösa medierna, samt för att validera de numeriska modeller som används. Ekvationer som beskriver flödet genom porösa medier implementeras i CFD (computational fluid dynamics) modeller och lagringstankarna modelleras som 2D-axelsymmetriska domäner. Bakgrundsorienterad schlierenteknik (BOS) och färgning av inloppsvatten används för den kvalitativa undersökningen och termoelement används för att mäta temperaturer vid olika positioner. Numeriska och experimentella resultat visar hur porösa medier har en positiv inverkan på temperaturskiktningen. Resultat från experiment då BOS teknik och färgning av vatten används visar en minskning av det termoklina skiktets tjocklek med en ökad polyuretanskumtjocklek. Detta kunde också ses för de numeriska fallen. Numeriska och experimentella resultat visar även att porösa medier har en positiv inverkan på dämpningen av turbulens och kinetisk energi. Fortsatt arbete krävs för att anpassa numeriska modeller till experimentella data. Jämförelser mellan numeriska och experimentella resultat uppvisar skillnader både hos flödesfält samt hos temperaturfördelningar inuti tankarna. Resultaten visar dock att porösa medier skulle kunna spela en betydande roll för utvecklingen av stratifierade värmelagringstankar.

Nuclear Magnetic Resonance is used for the determination of the properties of porous media in Geophysics and oil exploration. As it stands, there is a challenge in understanding the connection between the times measured in Free Induction Decay Nuclear Magnetic Resonance experiments and the shape of samples. In this work, suspensions and watersaturated densely-packed porous media with the volume fraction of the glass solid phase in the range from 10–4 to ∼1 are found to exhibit FID decay rates proportional to the square root of the volume fraction of the solid phase of the samples. A model of spheres in liquid is proposed for the description of such behavior.

Although the global energy demand is shifting towards a well-balanced energy mix, fossil fuels will continue to have a significant role in this transition and will maintain a big share in the energy mix portfolio. The production of oil and gas has already reached the apex in the time that most of the conventional giant reservoirs are depleting, and discoveries for new reserves have shrunk down. In conventional reservoirs, it is estimated that about two-thirds of the Original Oil in Place (OOIP) will not be produced within the field lifecycle, corresponding to an average Recovery Factor (RF) between 20% and 40%. This low recovery factors from traditional methods trigger more investments in the Enhanced Oil Recovery (EOR) techniques. Waterflooding is one of the most commonly used technique to increase RF by raising or maintaining reservoir pressure. Lack of comprehending the driving forces in Naturally Fractured Reservoirs and reservoir heterogeneity may lead to serious conformance problems in which dealing with excessive undesirable water production becomes very challenging. Chemical EOR through an injection of a polymer solution is amongst the tested options that can be used to improve sweep efficiency. Ultimately, understanding the reservoir characteristics and having the know-how to implement the best recovery option will help to maximize the field’s lifecycle and increase the RF. Therefore, this study investigates some key elements that have a significant influence on the overall fluid flow behavior. The work reveals insights on the impact of capillarity and wettability in heterogeneous porous media. An experimental lab-scale consisting of a 2D sandbox model, which mimics a water-wet fractured system with injection and production ports, was designed, fabricated, and tested in single-phase and two-phase flow scenarios including the injection of water and polymer solutions. In the case of single-phase flow, a waterflood baseline scenario was studied with controlled variables, which helped to distinguish the contrast with the polymer flood case. Implementing water injection in a fractured water-wet reservoir showed that water prefers to channel through high permeable streaks, which consequently leads to poor volumetric sweep leading to significant bypassed zones. Investigating the two-phase flow was the essence of this research. Thus, the same procedures were repeated where water and polymer were used to displace oil. During waterflooding, due to strong capillarity contrast between the matrix and fracture media, flow divergence was found to be faster towards the matrix medium where the matrix gets saturated faster than that the fracture, overriding the high permeability of the fracture. Whereas, polymer flooding exhibited better volumetric sweep in all scenarios. Numerical simulations were used to replicate the experiments. This work can give new visual insights about key recovery mechanisms in heterogeneous reservoirs using polymers.

abstract: Developing countries suffer from various health challenges due to inaccessible medical diagnostic laboratories and lack of resources to establish new laboratories. One way to address these issues is to develop diagnostic systems that are suitable for the low-resource setting. In addition to this, applications requiring rapid analyses further motivates the development of portable, easy-to-use, and accurate Point of Care (POC) diagnostics. Lateral Flow Immunoassays (LFIAs) are among the most successful POC tests as they satisfy most of the ASSURED criteria. However, factors like reagent stability, reaction rates limit the performance and robustness of LFIAs. The fluid flow rate in LFIA significantly affect the factors mentioned above, and hence, it is desirable to maintain an optimal fluid velocity in porous media. The main objective of this study is to build a statistical model that enables us to determine the optimal design parameters and ambient conditions for achieving a desired fluid velocity in porous media. This study mainly focuses on the effects of relative humidity and temperature on evaporation in porous media and the impact of geometry on fluid velocity in LFIAs. A set of finite element analyses were performed, and the obtained simulation results were then experimentally verified using Whatman filter paper with different geometry under varying ambient conditions. Design of experiments was conducted to estimate the significant factors affecting the fluid flow rate. Literature suggests that liquid evaporation is one of the major factors that inhibit fluid penetration and capillary flow in lateral flow Immunoassays. The obtained results closely align with the existing literature and conclude that a desired fluid flow rate can be achieved by tuning the geometry of the porous media. The derived statistical model suggests that a dry and warm atmosphere is expected to inhibit the fluid flow rate the most and vice-versa. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2019

Indiana University-Purdue University Indianapolis (IUPUI) / The interplay between biomechanics and blood perfusion in the optic nerve head (ONH) has a critical role in ocular pathologies, especially glaucomatous optic neuropathy. Elucidating the complex interactions of ONH perfusion and tissue structure in health and disease using current imaging methodologies is difficult, and mathematical modeling provides an approach to address these limitations. The biophysical phenomena governing the ONH physiology occur at different scales in time and space and porous media theory provides an ideal framework to model them. We critically review fundamentals of porous media theory, paying particular attention to the assumptions leading to a continuum biphasic model for the phenomenological description of fluid flow through biological tissues exhibiting viscoelastic behavior. The resulting system of equations is solved via a numerical method based on a novel hybridizable discontinuous Galerkin finite element discretization that allows accurate approximations of stresses and discharge velocities, in addition to solid displacement and fluid pressure. The model is used to theoretically investigate the influence of tissue viscoelasticity on the blood perfusion of the lamina cribrosa in the ONH. Our results suggest that changes in viscoelastic properties of the lamina may compromise tissue perfusion in response to sudden variations of intraocular pressure, possibly leading to optic disc hemorrhages.

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A combustion chamber incorporating a high temperature porous matrix was design and tested. The effects and merits of combining combustion on porous media and catalytic enhancement were explored, in addition to the proof of concept of integrating these technologies with simple heat engines, such as thermoelectric generators, to generate efficient and reliable power. The direct observation of the flame during the combustion becomes possible due to a specially designed stainless steel chamber incorporating a quartz window where the initiation and propagation of the combustion reaction/flame was directly visible. The simple design of the combustion chamber allowed for a series of thermocouples to be arranged on the central axis of the porous media. With the thermocouples as output and two flow controllers controlling the volumetric flow of fuel and air as input, it was possible to explore the behavior of the flame at different volumetric flow ranges and fuel to air ratios. Additionally the design allowed for thermoelectric modules to be placed in the walls of the combustion chamber. Using combustion as a heat source and passive fins for cooling, the device was able to generate enough power to power a small portable electronic device. The effects of La-Sr-Fe-Cr-Ru based perovskite catalysts, on matrix stabilized combustion in a porous ceramic media were also explored. Highly porous silicon carbide ceramics are used as a porous media for a catalytically enhanced superadiabatic combustion of a lean mixture of methane and air. Perovskite catalytic enhancement of SiC porous matrix with La0.75Sr0.25Fe0.6Cr0.35Ru0.05O3, La0.75Sr0.25Fe0.6Cr0.4O3, La0.75Sr0.25Fe0.95Ru0.05O3, La0.75Sr0.05Cr0.95Ru0.05O3, and LaFe0.95Ru0.05O3 were used to enhance combustion. The flammability limits of the combustion of methane and air were explored using both inert and catalytically enhanced surfaces of the porous ceramic media. By coating the SiC porous media with perovskite catalysts it was possible to lower the minimum stable equivalence ratio and achieve more efficient combustion.

Effective solvent extraction incorporating electromagnetic heating is a relatively new concept that relies on Radio Frequency heating and solvents to replace steam in current thermal processes for the purpose of extracting bitumen from oil rich sands. The work presented here will further the understanding of the near wellbore flow of this two phase system in order to better predict solvent vaporization dynamics and heat rates delivered to the pay zone. This numerical study details the aspects of phase change of immiscible, two component, liquid/vapor systems confined in porous media heated by electromagnetic radiation, approximated by a spatially dependent volumetric heat source term in the energy equation. The objective of this work is to utilize the numerical methodology presented herein to predict maximum solvent delivery rates to a heated isotropic porous matrix to avoid the over-saturation of the heated pay zone. The total liquid mass content and mean temperature in the domain are monitored to assess whether the liquid phase is fully vaporized prior to flowing across the numerical domain boundary. The distribution of the volumetric heat generation rate used to emulate the physics of electromagnetic heating in the domain decays away from the well bore. Some of the heat generated acts to superheat the already vaporized solvent away from the interface, requiring heat delivery rates that are many times greater than the energy required to turn the liquid solvent to vapor determined by an energy balance. Results of the parametric study from the pay zone simulations demonstrate the importance of the Darcian flow resistance forces added by the porous media to stabilize the flow being pulled away from the wellbore in the presence of gravity. For all cases involving an increase in solvent delivery rate with a constant heat rate, the permeability range required for full vaporization must decrease in order to balance the gravitational forces pulling the solvent from the heated region. For all conditions of permeability and solvent delivery rates, sufficiently increasing the heat rate results in complete vaporization of the liquid solvent. For the case of decreasing solvent delivery rate, a wider range of higher permeabilities for a given heat rate can be utilized while achieving full vaporization. A three dimensional surface outlining the transition from partially vaporized to fully vaporized regimes is constructed relating the solvent delivery rate, the permeability of the porous near wellbore zone and the heat rate supplied to the domain. For the range of permeabilities ~3000mD observed in these types of well bores, low solvent delivery rates and high heat rates must be utilized in order to achieve full vaporization.