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1
Awan, Faisal Ur Rahman. "Electrokinetic investigation of coal fines in fractured and porous media". Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2022. https://ro.ecu.edu.au/theses/2523.
Testo completoAbstract (sommario):
Coal seams are unconventional subsurface formations that host methane and are weaker (relative to conventional subsurface) formations. Coal seams are prone to coal fines generation within the fractured porous space throughout the life of the reservoir. These coal fines damage the permeability, deliverability and productivity of coal seams. Furthermore, the coal fines mobility/blockage in the hydraulically induced fractures and proppant packs negatively impacts the proppant conductivity. In this work, a comprehensive study has been conducted to augment the understanding of coal fines and their behaviour within porous and proppant pack systems. Systematic experiments were conducted to address the coal fines by developing various approaches presented in this work. The approaches adopted to achieve the study objectives were: i) streaming zeta potential on coal and sandstone, ii) nano-treated proppant surface modification for coal fines adsorption, and iii) coal fines mobility/attachment in the proppant packs.
One of the electrokinetic parameters that is crucial in releasing/mobilising coal fines is coal’s zeta potential. The coal surface is generally hydrophobic and possesses negative zeta potential. Researchers have used the electrophoretic zeta potential technique to indicate charge identification of coal particles, denoting repulsion or attraction of the particle. In chapter 3, a robust study investigates streaming zeta potential measurements of an in-situ sub-bituminous coal core saturated with saline water of 0.1, 0.3 and 0.6 mol.dm-3 NaCl salinities. Thus, the novel study determines the charge carried by percolating fluid when passing through coal rock. The zeta potential is directly proportional to saline water salinity. The trends found in the research were consistent with reported zeta potential measured using other techniques, while the magnitude varied. The findings reported in the study apply to subsurface coal seams at salinity up to 0.6 mol.dm-3 NaCl.
Coal seams are hydraulically fractured for commercial production, and sand-based proppants occupy the fractured space. Before understanding the electrokinetics of coal fines, the behaviour of these sand-based proppants should be determined. Sand-based proppants are predominantly silica, and so are sandstones. Furthermore, the selection of sandstone was further motivated by two reasons, i) for comparison and benchmarking, and ii) correlation with coals (as sandstone and coal both are negatively charged). The research presented in chapter 4 considered clay-rich (i.e. clay ≥ 5 wt.%) sandstones for the first time (as coal can have clay ingredients). Specifically, streaming potential measurements were conducted on Bandera Grey sandstone (clay-rich and -poor) saturated with saline water in pressurised environments. Additionally, the streaming potential was determined at identical conditions for the effect of two surfactants, sodium dodecylbenzene sulfonate (SDBS) and cetrimonium bromide (CTAB), at concentrations of 0.01 and 0.1 wt. % on the clay-poor sample. Moreover, a comparison of electrophoretic and streaming zeta potentials was conducted. Accordingly, the work analyses the effects of mineralogy and surfactants within this process. Clay-rich sandstone possessed lower zeta-potentials than clay-poor sandstone at the two tested salinities. SDBS reduced zeta-potential and yielded higher repulsive forces rendering the rock more hydrophilic. Additionally, electrophoretic zeta-potentials were higher when compared to streaming zeta-potentials. Mechanisms for the observed phenomena are also provided.
Following the observations from the two studies, proppant column experiments with glass bead proppant and high volatile bituminous were conducted and are presented in chapter 5. One of the approaches to handling coal fines is its dispersal within the aqueous suspension. Proppant column experiments were conducted to test various schemes. It was found that coal zeta potential using SDBS reaches a maximum, and regardless of the pH, it effectively delivers the maximum output of coal fines in the effluent. Thus, a 0.001 wt.% SDBS could effectively disperse coal fines suspension through proppant packs.
Nano-treated proppant surface modification was developed to investigate coal fines mobility/attachment within the proppant packs. Succinctly, four (alumina, magnesia, silica and zirconia) nanoparticles (NPs) were adsorbed onto synthetic porous media (glass bead) using a robust pseudo-continuous fixed-bed (PCFB) adsorption method in work presented in chapter 6. A wide range of salinity (0 to 10.5 wt.% NaCl), temperature (298.15 to 348.15 K), NPs loading (0.01 to 0.2 wt.%), and injection rate (1 to 50 mL.min-1) were tested. Results showed that PCFB adsorption of NPs with higher specific surface area resulted in faster adsorption (adsorbed in ~25 mins) with > 99% immobilisation of NPs on the proppant pack. Adsorption kinetics showed reasonable conformity with the pseudo-first-order model, where isothermal adsorption followed the Sips model. The adsorption capacity of magnesia NPs (specific surface area 50 to 80 m2.g-1, 7 wt.% NaCl) at 298.15 K was higher than silica NPs. Accordingly, the newly developed PCFB method can be used for onsite treatment of proppants with nanoparticles, which can then be injected into a fractured formation to achieve multiple objectives such as fines fixation, wettability alteration and sand control.
In this work, another study explored the application of nano-treated proppant packs on the adsorption of coal fines, presented in chapter 7. In this study, the objective was to identify silica nano-formulations (0 – 0.1 wt.%), and coal fines concentration of 0.1 to 1 wt.% were examined to determine the fixation of coal fines within the glass bead synthetic proppant pack. The quantitative results showed that the proppant pack with nanoparticle treatment strongly affects the fixation ability of coal fines. The non-NP treated pack yielded 30% adsorption, whilst the NP treated pack yielded 74% adsorption. It was noted that greater adsorption is also related to the higher zeta potential of silica NPs (i.e. nearer to iso-electric point).
A set of laboratory experiments on industrial-grade proppants was conducted as the definitive work, presented in chapter 8. The work involved sensitivity experiments as a function of coal rank, pH, salinity, and surfactants. These conductivity results were compared with established analytical models to interpret the mechanistic coal-proppant interaction in the presence of an electrolyte. It was found that fines dispersion and its mobility within the proppant pack is easier at high pH, low salinity, temperature, anionic surfactants, and lower concentration of coal fines. However, fines mobility is reduced at neutral pH, high salinity, temperature, and cationic surfactants.
2
Bahlouli, Mohamed Haythem. "Modélisation couplée des écoulements liquide-gaz et de l'hydro-mécanique dans un stockage géologique de déchets radioactifs". Electronic Thesis or Diss., Université de Toulouse (2023-....), 2025. http://www.theses.fr/2025TLSEP028.
Testo completoAbstract (sommario):
Le stockage géologique profond constitue la solution internationale la plus prometteuse pour la gestion des déchets les plus radioactifs et à durée de vie longue sur de très longues échelles de temps. En France, le projet Cigéo vise à stocker les déchets dits de haute activité (HA), principalement issus des combustibles usés des centrales nucléaires après retraitement et les déchets de moyenne activité à vie longue (MA-VL), qui correspondent aux structures métalliques qui entourent le combustible ou aux résidus liés au fonctionnement et à la maintenance des installations nucléaires. La sûreté du stockage est assurée par un système multi-barrières composé de barrières ouvragées et une roche hôte. Grâce à sa très faible conductivité hydraulique, sa faible diffusion moléculaire et sa capacité significative de rétention des radionucléides, l’argilite du Callovo-Oxfordien (COx) est considérée comme la formation géologique potentielle pour la réalisation du projet. Or, après la fermeture et le scellement de l'installation souterraine, une quantité significative de gaz (principalement de l’hydrogène) peut être générée en raison de plusieurs processus tels que la corrosion anaérobie des métaux, la radiolyse de l'eau et les réactions microbiennes. Si le transitoire hydraulique-gaz des installations souterraines a été très étudié au cours des deux dernières décennies, la représentation de certains processus fortement couplés tels que les écoulements diphasiques multi-composants dans des matériaux poreux très faiblement perméables, à des différentes échelles spatiales et l'hydro-mécanique restent potentiellement complexe. La présente étude a été réalisée à l’Unité d’expertise et de modélisation des installations de stockage, à l'Institut de radioprotection et de sûreté nucléaire. L'objectif était d'améliorer la robustesse des modélisations du comportement hydrodynamique des phases liquide-gaz et traiter la problématique des impacts mécaniques des déformations de la roche et des scellements sur le transport de gaz et vice versa. Seules des simulations numériques sont capables de rendre compte de l’ensemble des phénomènes sur les échelles d’espace et de temps à considérer. Pour cela, deux approches ont été suivies. Une étude analytique de l'écoulement monophasique gaz a été effectuée afin d'évaluer la sensibilité des phénomènes d'écoulement du gaz aux divers paramètres physiques, y compris la compressibilité et l'effet Klinkenberg. Parallèlement, des simulations numériques ont été réalisées sur un modèle d'alvéole de déchets HA. Elles ont permis de mettre en évidence l'évolution de la pression du gaz et la désaturation de la roche hôte et des scellements. Ces simulations prennent en compte la présence de l'air dans la phase gaz, afin d’appréhender le poids d'une atmosphère explosive en lien avec l'inflammabilité de l'hydrogène dans l'air. Ces études étaient aussi le terrain pour introduire des améliorations dans le code TOUGH2 et de développer des outils de pre- et de post- processing qui facilitent l'utilisation de ce code et l'analyse des résultats. Concernant le couplage hydromécanique, une revue bibliographique approfondie est réalisée, et a permis d'isoler les problèmes soulevés par le couplage poro-élastique en présence de gaz. Un modèle d'élasticité linéaire avec un couplage HM basé sur la théorie de Biot est ensuite étudié et implémenté dans le logiciel COMSOL Multiphysics en utilisant la méthode des éléments finis. Des simulations numériques de tests hydro-mécaniques drainés ou non-drainés ont été réalisés. Le couplage a permis de capturer l'interaction entre la variation de pression du fluide et les contraintes et déformations dans la roche poreuse. Un des résultats est la mise en évidence de la production fluideAs a safe long-term management of nuclear waste, deep geological disposal was proposed and is the widely accepted approach to deal with high-level radioactive waste. It is currently being under study in several countries. The long-term safety in a deep geological repository (DGR) is ensured through a multi-barrier system provided by engineered barrier and natural barrier systems. In most multi-barrier system concepts in crystalline and clay rock, argillaceous materials (clay rock or bentonite) are envisaged to use for barrier elements. Due to its very low hydraulic conductivity, low molecular diffusion and significant radionuclide retention capacity, COx claystone is considered as a potential geological host formation for an industrial radioactive waste repository in France. The performance of the host rock and engineered barriers in the construction phase and in a long-term perspective (thousands to million of years) is of primary importance for predicting the risk of dissemination of radioactivity. After the deep geological repository is closed and sealed, significant gas quantity can be generated due to several processes such as the anaerobic metal corrosion, water radiolysis and microbial reactions. Predicting gas flow in low-permeable, saturated materials is a challenging but important task in the risk assessment of a deep geological repository. Pressure build-up and gas migration in host rock and engineered barriers constitute a highly coupled hydro-mechanical (HM) process, and may contribute to the development of preferential gas pathways either by gas-induced micro-fracturing or macro-fracturing. In current numerical studies some behaviors still cannot be well represented, in particular, it is challenging to explain the gas migration behavior in the gas injection tests conducted on the clayey rock and barriers materials. Therefore, to better represent the actual physical process of gas flow, several modeling frameworks are proposed in the present thesis: single-phase gas flow (H2), two-phase water-gas multi-component flow (air, H2), and hydro-mechanical coupling (poro-elasticity). Two-phase gas-water flow in the waste cell model at different scales (a single waste cell contains several High Level Waste containers) is used here to quantitatively study transient hydraulic water-gas phenomena, such as gas pressure evolution and clayey rock desaturation. A wide range of scenarios and hypotheses is tested to assess significant differences between different scenarios in controlling gas migration and the transition from single phase water saturated conditions to two-phase and single phase gas. Although efficient in studying gas migration in presence of hydrogen only, the proposed models has presented a major limitation because of the difficulty in assessing gas phase evolution in presence of air. Multiphase flow of water with a gas phase (hydrogen and air) together with consideration of dissolved hydrogen, air and water vapor diffusion, is studied using equation of state EOS7R (water, brine, RN1, RN2, air) of the TOUGH2 family of codes. We have implemented code enhancements and post-processing scripts, which enhanced our capabilities in analyzing and interpreting results. A separate study of single phase gas flow was developed in order to assess analytically the sensitivity of gas flow phenomena to various rock parameters, including for instance the Klinkenberg effect due to gas slippage at low pressure in tight pores. Concerning the hydromechanical coupling, an extensive review was developed, including poroelastic coupling in the presence of gas. A linear poroelastic model based on Biot theory is studied and implemented in the Finite Elements software COMSOL Multiphysics. The coupling allows us to capture the interaction between fluid pressure variation and the stresses and strains in the porous rock (drained and undrained tests)
3
Kampel, Guido. "Mathematical Modeling of Fines Migration snd Clogging in Porous Media". Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19764.
Testo completoAbstract (sommario):
Mathematical Modeling of Fines Migration and Clogging in Porous Media
Guido Kampel
87 Pages
Directed by Dr. Guillermo H. Goldsztein
A porous medium is a material that contains regions filled with fluid embedded in a solid matrix. These fluid filled regions are called pores or voids. Suspensions are fluids with small particles called fines. As a suspension flows through a porous material, some fines are trapped within the material while others that were trapped may be released.
Filters are an example of porous media. We model filters as networks of channels.
As a suspension flows across the filter, particles clog channels. We assume that there is no flow through clogged channels. In the first part of this thesis, we compute a sharp upper bound on the number of channels that can clog before fluid can no longer flow through the filter.
Soil mass is another example of porous media. Fluid in porous media flows through tortuous paths. This tortuosity and inertial effects cause fines to collide with pore walls.
After each collision, a particle looses momentum and needs to be accelerated again by hydrodynamic forces. As a result, the average velocity of fines is smaller than that of the fluid. This retardation of the fines with respect to the fluid may lead to an increase of the concentration of fines in certain regions which may eventually result in the plugging of the porous medium. This effect is of importance in flows near wells where the flow has circular symmetry and thus, it is not macroscopically homogeneous. In the second part of this thesis we develop and analyze a mathematical model to study the physical effect described above.
In the third and last part of this thesis we study particle migration and clogging as suspension flows through filters by means of numerical simulations and elementary analysis. We explore the effect that network geometry, probability distribution of the width of the channels and probability distribution of the diameter of the particles have on the performance of filters.
4
Kampel, Guido. "Mathematical modeling of fines migration and clogging in porous media". Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19764.
Testo completoAbstract (sommario):
Thesis (Ph.D)--Mathematics, Georgia Institute of Technology, 2008.Committee Chair: Goldsztein, Guillermo; Committee Member: Dieci, Luca; Committee Member: McCuan, John; Committee Member: Santamarina, Juan; Committee Member: Zhou, Haomin.
5
Jamiolahmady, Mahmoud. "Mechanistic modelling of gas-condensate flow in porous media". Thesis, Heriot-Watt University, 2001. http://hdl.handle.net/10399/532.
Testo completo
6
SANTOS, MARCOS PAULO PEREIRA C. DOS. "PORE NETWORK MODEL FOR RETROGRADE GAS FLOW IN POROUS MEDIA". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2017. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=32319@1.
Testo completoAbstract (sommario):
PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE EXCELENCIA ACADEMICA
A produtividade de poços produtores de gás, que operam com pressões de fundo inferiores à pressão de orvalho, é afetada pelo aparecimento da saturação de líquido em seus entornos. Para entender esse fenômeno, conhecido como bloqueio por condensado, os simuladores em escala de poros são ferramentas úteis na investigação dos parâmetros que influenciam na quantidade e na distribuição da saturação de condensado, assim como seus efeitos na redução do fluxo de gás. Esse trabalho apresenta um modelo de rede de capilares composicional e isotérmico para o estudo do escoamento de gás retrógrado em meios porosos. Forças capilares e gravitacionais não foram consideradas. O escoamento monofásico é comutado para bifásico de padrão anular quando a pressão e a composição do fluido atingem um critério de estabilidade. O método de Newton é aplicado para resolver as equações de fluxo e consistência dos volumes e calcular o transporte de cada um dos componentes ao longo da rede. As propriedades do fluido e o comportamento do escoamento foram testadas contra os resultados de um simulador termodinâmico comercial e soluções analíticas, respectivamente. Após validação, o simulador foi utilizado para obter curvas de permeabilidade relativa gás-líquido através da despressurização de uma rede 2D e alguns resultados são discutidos.
Gas well deliverability in retrograde gas reservoirs is affected by the appearance of liquid saturation around the wellbore when the bottom-hole pressure is below the dew point. Pore-scale simulators are used to model this phenomenon, known as condensate blockage, and to investigate parameters that ifluence the amount and the distribution of condensate saturation, as well as how it chokes the gas flow. Here, a fully-implicit isothermal compositional pore-scale network model is presented for retrograde gas flow in porous media. Capillary and gravitational forces are neglected. The model shifts from single-phase flow to annular flow regime when the pressure and the fluid composition reach a stability criteria. Newton s method is applied on flow and volume consistency equations to calculate the transport of each component through the network. Fluid properties and flow behavior were tested against a commercial thermodynamic simulator and analytical solutions respectively. After validation, the simulator was used to predict gas-liquid relative permeability from a depletion process in a 2D network and some results are discussed.
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Boltze, Uta. "Gas emissions relevant to waste management, through watertables in porous media". Thesis, Imperial College London, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307822.
Testo completo
8
Vieira, Rodriguez Cristian. "Calibration of Electrical Methods for Detecting Gas Injection in Porous Media". Paris, Institut de physique du globe, 2013. http://www.theses.fr/2013GLOB1001.
Testo completo
9
Gill, Richard T. "Electrokinetic-enhanced migration of solutes for improved bioremediation in heterogeneous granular porous media". Thesis, University of Sheffield, 2016. http://etheses.whiterose.ac.uk/12712/.
Testo completoAbstract (sommario):
Contaminated land is a global problem. Where it presents an unacceptable risk to receptors such as human health or ecosystems, remediation actions must be taken. Current remediation technologies can be ineffective due to mass transfer limitations. A typical scenario where these limitations control remediation efficacy is a physically heterogeneous aquifer where hydraulic conductivity (K) varies spatially. Under these conditions remediation is limited by solute migration across K boundaries. This thesis couples two remediation technologies, in situ bioremediation and electrokinetics (EK), to overcome the mass transfer limitations presented by physically heterogeneous settings. Bioremediation is the transformation of contaminants into less harmful substances by microorganisms; and EK is the application of a direct current to initiate certain transport processes independent of K. Where bioremediation is limited due to the influence of physical heterogeneity, EK transport processes could be applied to initiate an additional flux of solutes across K boundaries. This thesis investigates the influence of physical heterogeneity on EK migration of an amendment designed to enhance bioremediation. The research presented in this thesis advances the current state of knowledge for EK-BIO applications both at the fundamental level and field-scale using laboratory and desk based studies respectively. Laboratory apparatus was designed and built to accommodate physical heterogeneity, electrokinetic transport of solutes and contaminant biodegradation. Broadly, two types of EK experiment were conducted. Firstly, EK amendment migration under abiotic conditions on different arrangements of physical heterogeneity. Secondly, experiments in the same laboratory setup that introduced contaminant and microbial variables. From these experiments a conceptual framework is developed that describes the influence of physical heterogeneity on the EK transport of an amendment. It relates the spatial change in material properties associated with physical heterogeneity with aspects of EK application, such as the voltage gradient, and observes the implications for amendment transport. For example a layered contrast in material type generated a non-uniform electric field when direct current was applied, this led to non-uniform EK transport of the amendment relative to homogeneous settings. When contaminant and microbial variables were introduced to the experimental setup a greater understanding of EK-BIO applications to physically heterogeneous settings was gained. These experiments highlight and discuss the technical issues applying EK to enhance bioremediation by amendment addition versus contaminant removal by EK induced pore fluid movement. Desk based studies included a review of EK-BIO literature and a sustainability assessment that considered EK-BIO at the field scale. The review summarises the practical aspects of the technology in applications to natural environments. It notes that numerous limitations exist to EK-BIO applications in these settings but that there are many different implementation methods that can mitigate these effects. The sustainability assessment compares EK-BIO with conventional remediation technologies against specific criteria for a complex site contaminated with BTEX and MTBE. EK-BIO compares well to other technologies however characteristics of the site will determine the potential sustainability benefits of applying EK.
10
Shiko, Elenica. "NMR and gas sorption studies of structure-transport relationships in porous media". Thesis, University of Bath, 2013. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.582800.
Testo completoAbstract (sommario):
The work in this thesis is focused on testing the accuracy of the gas sorption and NMR cryoporometry characterization techniques to estimate the key pore descriptors which affect the activity of porous materials used as catalyst supports and drug delivery systems. Both techniques, though, assume independent pores, neglecting advanced adsorption and melting phenomena that can specifically skew the pore size distribution and subsequently lead to inaccurate predictions of catalytic or therapeutic efficiency of the porous system. Firstly, the independent domain theory for both processes was studied by breaking down the pore-filling process of a mesoporous catalyst support, into steps. The system was partially saturated with water or cyclohexane at different pressures, via adsorption and desorption, followed by a cryoporometry experiment at each saturation fraction. Moreover, scanning curves and loops, together with PFG NMR and relaxometry were employed to ascertain the spatial arrangement of the liquid ganglia at each partial saturation and for certain molten fractions. It was shown that the configuration of the liquid condensates varied with position around the hysteresis loop, deviating from the single pore hysteresis mechanism for both adsorbates. Advanced melting of water was associated with a percolation-type transition in the connectivity of the ganglia, which could be curtailed to some extent by sample fragmentation. Also, some pores filled via advanced adsorption at lower pressures. On the contrary, advanced melting of cyclohexane arose from the liquid bridging the pore cross-sections of the partially filled pores. Secondly, an integrated nitrogen-water-nitrogen experiment was employed to test the source of sorption hysteresis and to compare the extent of advanced adsorption phenomena for nitrogen and water sorption, by isolating a subset of pores. It was found that the Kelvin-Cohan equations and the DFT algorithm overestimate the width of the sorption hysteresis in independent pores of the catalyst support studied in this work. Moreover, the adsorption mechanism of nitrogen differs to that of water, and advanced adsorption of nitrogen is less severe than that of water. Thirdly, cryodiffusometry and gas sorption techniques were used to estimate the pore space descriptors (surface area, pore size, tortuosity, porosity) of two different types of mesoporous silicas, candidates for drug delivery. The structure-transport relationships in these materials were investigated to interpret the drug release profiles obtained for release studies carried out in simulated gastrointestinal fluids. It was found that the release rate was mainly controlled by the size of the silica particles and the silica solubility itself in the environment present. Also, different synthesis routes were tested to optimize the drug loaded PLGA nanoparticles, for convection-enhanced drug delivery into the brain. Various model and real hydrophobic and hydrophilic drugs were tested. In-vitro and in-vivo studies showed that the dialysis method led to production of particles with the desirable characteristics, which were successfully distributed in the mice brain. The sensitivity of the cryoporometry melting, gas sorption and imaging techniques was found inadequate to resolve the inner structure of the polymer matrix. Last, the experimental time for the cryodiffusometry experiments in this work was long due to the high recycle delay times required to maximise the signal to noise ratio. It is though found that high delay times are unnecessary when BBP-LED pulse sequence is used, even when the fluid is imbibed in a mesoporous systems.
11
Thatiparti, Deepthi Sharan. "Capillary pressure Measurement in Glass bead porous media and Gas diffusion layers". University of Cincinnati / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1281450979.
Testo completo
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Al-Aabidy, Qahtan. "Modelling of turbulent flow and heat transfer in porous media for gas turbine blade cooling". Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/modelling-of-turbulent-flow-and-heat-transfer-in-porous-media-for-gas-turbine-blade-cooling(f7781d8e-bb1e-4bb7-a57e-4e77875ad6d6).html.
Testo completoAbstract (sommario):
This thesis focuses on the study of flow and heat transfer in porous media in both laminar and turbulent flow regimes, by using Volume Averaged Reynolds Navier Stokes (VARNS) approach. The main concern is to investigate the possibility of using porous media for the gas turbine blade cooling. Very recently, using this technique in blade cooling, particularly with internal cooling, has motivated many researchers due to an effective enhancement in the blade cooling. In this study turbulence is represented by using the Launder-Sharma low-Reynolds-number k-Îμ turbulence model, which is modified via proposals by Nakayama and Kuwahara (2008) and Pedras and de Lemos (2001) for extra source terms in the turbulent transport equations to account for the porous structure, which is treated as rigid and isotropic. Due to the changing of the effective porosity as the clear fluid region is approached, the porosity and additional source term in the macroscopic Reynolds averaged Navier-Stokes equations are relaxed across a thin transitional layer at the edges of the porous media. This is achieved by utilizing exponential damping relations to consider these changes. The Local Thermal Equilibrium (LTE) (one-energy equation) model is used for the thermal analysis in porous media. In order to investigate the validity of the extended model, laminar and turbulent flow in different cases, fully developed and developing flows, have been considered. For laminar flows, fully developed plane channel flows with one and two porous layers, a channel with a single porous block and partially filled porous channel flows have been examined for the purpose of validating the extra drag terms in the momentum equations. For the validation purpose for turbulent flows in porous media, the extended model has been tested in homogeneous porous media, turbulent porous channel flows, turbulent solid/porous rib channel flows, and repeated turbulent porous baffled channel flows. Results of all laminar cases show excellent qualitative agreements with the available numerical calculations and experimental data. Results of all turbulent cases show that the extended model returns generally satisfactory accuracy through the comparisons with the available data, except for some predictive weaknesses in regions of either impingement or adverse pressure gradients, both of which are largely due the underlying eddy-viscosity model formulation employed. Thus, from all results, it can be confirmed that the extended model is promising for engineering applications.
13
Al-Kharusi, Badr Soud. "Relative permeability of gas-condensate near wellbore, and gas-condensate-water in bulk of reservoir". Thesis, Heriot-Watt University, 2000. http://hdl.handle.net/10399/1098.
Testo completo
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Han, Ji-seok. "The role of colloidal particles on the migration of air bubbles in porous media". Thesis, [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-2471.
Testo completo
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Okafor, Emeka Joachin. "Modelling vaporizing fluid flow through porous media with applications to liquefied natural gas". Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/11675.
Testo completoAbstract (sommario):
The problem of vaporizing flow of liquefied natural gas (LNG) through porous or penetrable media has received very little attention despite its importance in assessing the performance and risk-based safety of large membrane tank LNG ships under barrier leakages. In this work, a fluid flow model is proposed and used to analyse the vaporizing flow behaviour of LNG through soil and glass wool porous materials. Furthermore, a modified vaporizing liquid pool model is implemented and used to examine the problem of vaporizing LNG pool on non-penetrable solid substrates. We employed an explicit, finite difference and a fourth-order Runge-Kutta algorithms coded in FORTRAN to respectively solve the flow and pool models. Both models were successfully verified and validated by comparisons to experimental data, analytical solutions, and to predictions of a commercial software (TOUGH2). Results from the vaporizing flow and pool analyses demonstrate that, for some of the applications considered, the liquid is expected to reach considered threshold depths, seep through the porous layer and contact, contaminate and/or embrittle surrounding natural or engineered systems. For the specific application to LNG cargo containment systems (or cargo tanks), this work has shown that there are safety risks associated with LNG leakage, which are ultra-low temperature of the inner hull, cryogenic damage and subsequent failure of the cargo containment system. Thus, for any LNG membrane cargo containment system to continue to be safe and secure, the various structural members of the insulation system should be designed and equipped with new and improved materials that possesses the necessary mechanical and thermophysical properties to maintain and/or improve the critical temperature standard and low-temperature performance of these systems. Further work should consider additional experimental evidence in order to fully validate and establish that solution predictions by the proposed models are describing the actual physical effects.
16
Aguilar, Abraham Rojano 1959. "A theoretical study of gas flow in porous media with a spherical source". Diss., The University of Arizona, 1998. http://hdl.handle.net/10150/288786.
Testo completoAbstract (sommario):
Gas flow behavior from a spherical source is explored by using linear and nonlinear models, not only in terms of pressure but also in terms of flux. The approach considers dimensionless parameters scaling both radius and time. Specific observations are made for large, moderate, and small time conditions. At large time, the nonlinear model becomes a linear ordinary differential equation with pressure solution independent of the material. However, for moderate and small scaled times this is not the case. The nonlinear model must be solved by using either linear approximations, semi-analytical, or numerical procedures. This model is nonlinear in the primary variable (pressure). However, appropriate mathematical manipulations allow one to change the nonlinearity into a single coefficient, depending on pressure. Focusing on the effects of this coefficient, the nonlinear solution can be confined between two linear solutions obtained by using atmospheric and boundary pressures. Appendix A is an exploration of the errors arising between the nonlinear solution and these two solutions. In Appendix B, a nonlinear model is used to find solutions for large, moderate, and small times. For large time, the case corresponds to the steady state case, and coincides with the solution presented in Appendix A. For moderate and small times the quasi-analytical approximation and the asymptotic solutions of linear and quadratic normalizations of pressure are presented. In Appendix C, simulations of gas flows in linear and nonlinear situations are made. The problem is to determine the change of air pressure in a tank when it is connected to a spherical cavity embedded in a porous medium. These changes in pressure occur when the air moves through the porous media, either for gas extraction or air injection. Both linear and nonlinear analyses require calculations of the pressure and the mass in the tank when the initial and boundary conditions change with time. For each case, gas extraction or air injection, the differences between the linear and the nonlinear models are examined to determine the suitability of the linear model.
17
Rasouli, Pejman. "On the role of multicomponent diffusion and electrochemical migration for reactive transport in porous media". Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/59956.
Testo completoAbstract (sommario):
In multicomponent solutions, electrostatic coupling between charged species leads to a process called “electromigration”. Neglecting electromigration results in a charge imbalance and an incomplete and unrealistic description of mass transfer. Although not commonly considered in reactive transport codes, electromigration can strongly affect mass transport processes and can explain unexpected behaviors such as uphill diffusion or isotope fractionation. Including electrostatic coupling in reactive transport codes enables simulation of problems involving mass transport by advection and diffusion, electromigration and geochemical reactions, such as electrokinetic remediation and the geobattery concept associated with buried ore bodies. There are generally two methods for coupling charge and mass continuities. The first method is based on the null-current approach which assumes negligible electric current transmission. The second method considers explicit coupling of mass and electric fluxes. In this study both methods are investigated and their implications for reactive transport are examined.
To this end, MIN3P, a fully coupled 3D reactive transport code, was extended by integrating the Nernst-Planck and Gauss-Ampère equations. The implementation of the Nernst-Planck equations was verified by inter-comparison with other existing reactive transport codes based on a set of benchmark problems. At the same time, these benchmark problems illustrate the effect of electric coupling during multicomponent diffusion and electrochemical migration.
By explicit coupling of the Nernst-Planck and Gauss-Ampère equations, MIN3P was further enhanced to simulate electrokinetic remediation and the resulting code was tested for desalination problems. In addition, scenario and sensitivity analysis were used to investigate the potential for spontaneous exsolution of gases in response to gas generation at the electrodes of electrokinetic remediation systems.
Finally, a process-based model linking surface-measureable self-potential signals to electrochemical transport and geochemical reactions associated with buried metallic bodies was developed. The enhanced code provides a reactive transport modeling framework for process-based forward modeling of self-potential signals and associated geochemical signatures of buried ore bodies and allows a quantitative investigation of the “geobattery concept”. The code was tested based on published data from a laboratory experiment involving a buried iron bar and used to evaluate the geobattery concept based on an illustrative example of a buried ore body.Applied Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
18
Bennet, D. A. "Gas flow in layered porous media with particular reference to the iron blast furnace". Thesis, University of Newcastle Upon Tyne, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233401.
Testo completo
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Raed, Khaled. "Investigation of Knudsen and gas‐atmosphere effects on effective thermal conductivity of porous media". Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2013. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-117386.
Testo completoAbstract (sommario):
Die vorliegende Arbeit befasst sich mit Untersuchung der gekoppelten Einflüsse von Gasart, Porengröße und Porengrößenverteilung auf die effektive Wärmeleitfähigkeit nicht-durchströmter poröser Materialien (Dämmstoffe). Diese Zusammenhänge sind bisher nur ansatzweise bekannt und für eine spätere praktische Anwendung von zunehmend großer Bedeutung. Um dies zu erreichen wurden 12 verschiedene hoch poröse Materialien (Porosität höher als 70 %) ausgewählt, die unterschiedlichen Porengrößenverteilungen im Makro- Mikro- und Nanobereich haben. Die effektive Wärmeleitfähigkeit wurde hauptsachlich in zwei unterschiedlichen Messverfahren untersucht. Die Messungen erfolgt bei normalem Druck in vier Gas Atmosphären (Kr, Ar, N2 and He) bei Temperaturen bis maximal 900 °C. Kritische Analyse zum jeweiligen Messverfahren und Auswertungsalgorithmus wurden durchgeführt. Ein mathematisches Model basiert auf die Porengrößenverteilung mit Berücksichtigung des Knudsen Effekts wurde entwickelt um die Änderung der effektiven Wärmeleitfähigkeit beim Wechsel der Gas Atmosphäre auszuwerten. Diese führt zu besser Ergebnisse als die ausgewertet Ergebnisse von den vorhandenen Modellen aus der Literatur. In the present work, the influences of exchanging the filling gas accompanied with Knudsen effect on effective thermal conductivity were investigated with experiments and physical mathematical modeling. This work is thought to be the first intensive study in this area of the research, which includes twelve different porous insulation materials. Analysis of the huge number of experimental results leaded to new observations regarding various coupling effects. An improved model for predicting the change in effective thermal conductivity due to exchanging the filling gas has been developed with regards to the Knudsen effect based on models for rarefied gases and parallel arrangements models for effective thermal conductivity
20
Noman, Rashed. "High velocity gas flow in porous media : effects of pore structure and liquid saturation". Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/47205.
Testo completo
21
Fu, Xiaojing Ph D. Massachusetts Institute of Technology. "Multiphase flow in porous media with phase transitions : from CO₂ sequestration to gas hydrate systems". Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111445.
Testo completoAbstract (sommario):
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 159-175).
Ongoing efforts to mitigate climate change include the understanding of natural and engineered processes that can impact the global carbon budget and the fate of greenhouse gases (GHG). Among engineered systems, one promising tool to reduce atmospheric emissions of anthropogenic carbon dioxide (CO₂) is geologic sequestration of CO₂ , which entails the injection of CO₂ into deep geologic formations, like saline aquifers, for long-term storage. Among natural contributors, methane hydrates, an ice-like substance commonly found in seafloor sediments and permafrost, hold large amounts of the world's mobile carbon and are subject to an increased risk of dissociation due to rising temperatures. The dissociation of methane hydrates releases methane gas-a more potent GHG than CO₂-and potentially contributes to a positive feedback in terms of climatic change. In this Thesis, we explore fundamental mechanisms controlling the physics of geologic CO₂ sequestration and natural gas hydrate systems, with an emphasis on the interplay between multiphase flow-the simultaneous motion of several fluid phases and phase transitions-the creation or destruction of fluid or solid phases due to thermodynamically driven reactions. We first study the fate of CO₂ in saline aquifers in the presence of CO₂ -brine-carbonate geochemical reactions. We use high-resolution simulations to examine the interplay between the density-driven convective mixing and the rock dissolution reactions. We find that dissolution of carbonate rock initiates in regions of locally high mixing, but that the geochemical reaction shuts down significantly earlier than shutdown of convective mixing. This early shutdown reflects the important role that chemical speciation plays in this hydrodynamics-reaction coupled process. We then study hydrodynamic and thermodynamic processes pertaining to a gas hydrate system under changing temperature and pressure conditions. The framework for our analysis is that of phase-field modeling of binary mixtures far from equilibrium, and show that: (1) the interplay between phase separation and hydrodynamic instability can arrest the Ostwald ripening process characteristic of nonflowing mixtures; (2) partial miscibility exerts a powerful control on the degree of viscous fingering in a gas-liquid system, whereby fluid dissolution hinders fingering while fluid exsolution enhances fingering. We employ this theoretical phase-field modeling approach to explain observations of bubble expansion coupled with gas dissolution and hydrate formation in controlled laboratory experiments. Unraveling this coupling informs our understanding of the fate of hydrate-crusted methane bubbles in the ocean water column and the migration of gas pockets in hydrate-bearing sediments.
by Xiaojing Fu.
Ph. D.
22
Wang, Ruopeng 1972. "Study of gas flow dynamics in porous and granular media with laser-polarized ¹²⁹Xe NMR". Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/34652.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 2005.Includes bibliographical references (p. 173-182).
This thesis presents Nuclear Magnetic Resonance (NMR) studies of gas flow dynamics in porous and granular media by using laser-polarized ¹²⁹Xe . Two different physical processes, the gas transport in porous rock cores and the mass exchanges between different phases in fluidized granular systems, were investigated and new experimental methods were designed to measure several important parameters characterizing the two systems. Methods for measuring the parameters had been either unavailable or significantly limited previously. The research involved modeling the gas flow in porous and granular media by relating the dynamics of spin magnetization to the interesting parameters, as well as correspondingly designing new measurement methods and verifying them on the laboratory test beds. We proposed a simple method to measure two important parameters of reservoir rocks, permeability and effective porosity, by probing the flow front of laser-polarized xenon gas inside the rock cores. The method was thoroughly tested on different categories of rocks with permeability values spanning two orders of magnitude, and the results were in agreement with those from the established techniques.
(cont.) The uniqueness in the work is that the fast method developed is capable of measuring the two parameters simultaneously on the same setup. Bubble-emulsion exchange and emulsion-adsorption exchange in a fluidized bed are two processes crucial to the efficiency of many chemical reactors working in bubbling regime. We used differences in T2 and chemical shift to contrast the three phases in the xenon spectra, and designed methods to measure the inter-phase exchange rates. The measured results of the bubble-emulsion and emulsion-adsorption exchange rates agreed well with predictions based on available theory. Our approach is the first to non-invasively probe natural bubbles in a three-dimensional bed, and to measure the exchange rate between the emulsion phase and multiple bubbles.
by Ruopeng Wang.
Ph.D.
23
Johansson, Martin Viktor. "Gas transport in porous media : an investigation of the hydrodynamic to free molecular flow regime". Thesis, Aix-Marseille, 2019. http://www.theses.fr/2019AIXM0278.
Testo completoAbstract (sommario):
La thèse porte sur le transport de gaz raréfié dans des milieux poreux causé par des gradients de pression ou de température. Un gaz en milieu poreux se raréfie lorsque l'échelle est petite, comme pour les milieux micro et nanoporeux, ou lorsque la pression est faible (conditions de vide). Les méthodes de mesure des gradients respectifs sont élaborées et les résultats sont analysés. Dans le cas d'un écoulement de gaz à gradient de pression, la perméabilité est une propriété intrinsèque et une mesure de la manière avec laquelle le gaz circule dans le milieu poreux. Le comportement du flux de gaz diffère considérablement selon le degré de raréfaction. Pour caractériser le niveau de raréfaction de l'écoulement de gaz à l'intérieur d'un milieu poreux, une propriété intrinsèque supplémentaire est proposée, la dimension caractéristique de l'écoulement. Cette propriété a également une interprétation physique, et sa mesure pour un échantillon poreux peut être utilisée pour caractériser l'échantillon comme une méthode d'analyse non destructive. Lorsque le milieu poreux est soumis à un gradient de température dans des conditions raréfiées, l'effet de transpiration thermique provoque des flux gazeux du côté froid vers le côté chaud. Les propriétés transitoires et stationnaires de la transpiration thermique en milieu poreux sont analysées. Les méthodologies développées sont appliquées pour analyser les membranes céramiques microporeuses et les milieux poreux en acier inoxydable fritté. Le dernier type de milieu poreux est particulièrement adapté à l'étalonnage des jauges à vide poussé. La méthode d'étalonnage présentée est facile à utiliser, fiable et préciseThe thesis investigates the transport of rarefied gas in porous media caused by either pressure or temperature gradients. A gas in porous media becomes rarefied when either the scale is small, as for micro and nanoporous media, or when the pressure is low (vacuum conditions). The measurement methodologies for the respective gradients are developed, and the results are analyzed. For a pressure gradient driven gas flow, the permeability is an intrinsic property and measure of how easily gas flows through the porous media. The gas flow behavior differs significantly depending on the degree of rarefaction. To characterize the rarefaction level of the gas flow inside a porous medium an additional intrinsic property is proposed, the characteristic flow dimension. This property also has a physical interpretation, and its measure for a porous sample can be used to characterize the sample as a non-destructive analysis method. When the porous media is subject to a temperature gradient under rarefied conditions, the thermal transpiration effect, causes gas flows from the cold side toward the hot end. Both the transient and stationary properties of the thermal transpiration in porous media are analyzed. The developed methodologies are applied to analyze the microporous ceramic membranes and sintered stainless steel porous media. The last type of porous media is particularly suitable for high-vacuum gauge calibration. The presented calibration method is easy to use, reliable and accurate
24
Grover, David Klein Weibust. "Surface Gas Permeability of Porous Building Materials: Measurement, Analysis and Applications". ScholarWorks @ UVM, 2014. http://scholarworks.uvm.edu/graddis/266.
Testo completoAbstract (sommario):
In many events affecting our civil infrastructure, such as contamination or weathering, it is likely that only the surfaces of the affected building materials will be available for non-destructive measurements. In this work, we describe and analyze surface gas permeability measurements on a variety of natural and engineered building materials using two types of relatively new, non-destructive surface permeameters. It is shown that the surface gas permeability measurements correlate well with each other and could provide rapid estimates of macroscopic gas permeability and degradation of materials due to weathering. It is hypothesized that surface permeability can be used to predict macroscopic wicking of water. The results indicated that macroscopic wicking correlated reasonably well with surface permeability measurements of uniform materials with low permeabilities such as sandstones and clay brick.
25
Bhandari, Dhaval Ajit. "Hollow fiber sorbents for the desulfurization of pipeline natural gas". Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/42838.
Testo completoAbstract (sommario):
Pipeline natural gas is the primary fuel of choice for distributed fuel cell-based applications. The concentration of sulfur in odorized natural gas is about 30 ppm, with acceptable levels being <1 ppm for catalyst stability in such applications. Packed bed technology for desulfurization suffers from several disadvantages including high pressure drop and slow regeneration rates that require large unit sizes.
We describe a novel Rapid Temperature Swing Adsorption (RTSA) system utilizing hollow fibers with polymer 'binder', impregnated with high loadings of sulfur selective sorbent 'fillers'. Steam and cooling water can be utilized to thermally swing the sorbent during the regeneration cycles. An impermeable, thin polymer barrier layer on the outside of fiber sorbents allows only thermal interactions with the regeneration media, thereby promoting consistent sorption capacity over repeated cycles. A simplified flow pattern minimizes pressure drop, porous core morphology maximizes sorption efficiencies, while small fiber dimensions allows for rapid thermal cycles.
26
Böttcher, Norbert. "Thermodynamics of porous media: non-linear flow processes". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-137894.
Testo completoAbstract (sommario):
Numerical modelling of subsurface processes, such as geotechnical, geohydrological or geothermal applications requires a realistic description of fluid parameters in order to obtain plausible results. Particularly for gases, the properties of a fluid strongly depend on the primary variables of the simulated systems, which lead to non-linerarities in the governing equations. This thesis describes the development, evaluation and application of a numerical model for non-isothermal flow processes based on thermodynamic principles. Governing and constitutive equations of this model have been implemented into the open-source scientific FEM simulator OpenGeoSys. The model has been verified by several well-known benchmark tests for heat transport as well as for single- and multiphase flow. To describe physical fluid behaviour, highly accurate thermophysical property correlations of various fluids and fluid mixtures have been utilized. These correlations are functions of density and temperature. Thus, the accuracy of those correlations is strongly depending on the precision of the chosen equation of state (EOS), which provides a relation between the system state variables pressure, temperature, and composition. Complex multi-parameter EOSs reach a higher level of accuracy than general cubic equations, but lead to very expansive computing times. Therefore, a sensitivity analysis has been conducted to investigate the effects of EOS uncertainties on numerical simulation results. The comparison shows, that small differences in the density function may lead to significant discrepancies in the simulation results. Applying a compromise between precision and computational effort, a cubic EOS has been chosen for the simulation of the continuous injection of carbon dioxide into a depleted natural gas reservoir. In this simulation, real fluid behaviour has been considered. Interpreting the simulation results allows prognoses of CO2 propagation velocities and its distribution within the reservoir. These results are helpful and necessary for scheduling real injection strategiesFür die numerische Modellierung von unterirdischen Prozessen, wie z. B. geotechnische, geohydrologische oder geothermische Anwendungen, ist eine möglichst genaue Beschreibung der Parameter der beteiligten Fluide notwendig, um plausible Ergebnisse zu erhalten. Fluideigenschaften, vor allem die Eigenschaften von Gasen, sind stark abhängig von den jeweiligen Primärvariablen der simulierten Prozesse. Dies führt zu Nicht-linearitäten in den prozessbeschreibenden partiellen Differentialgleichungen. In der vorliegenden Arbeit wird die Entwicklung, die Evaluierung und die Anwendung eines numerischen Modells für nicht-isotherme Strömungsprozesse in porösen Medien beschrieben, das auf thermodynamischen Grundlagen beruht. Strömungs-, Transport- und Materialgleichungen wurden in die open-source-Software-Plattform OpenGeoSys implementiert. Das entwickelte Modell wurde mittels verschiedener, namhafter Benchmark-Tests für Wärmetransport sowie für Ein- und Mehrphasenströmung verifiziert. Um physikalisches Fluidverhalten zu beschreiben, wurden hochgenaue Korrelationsfunktionen für mehrere relevante Fluide und deren Gemische verwendet. Diese Korrelationen sind Funktionen der Dichte und der Temperatur. Daher ist deren Genauigkeit von der Präzision der verwendeten Zustandsgleichungen abhängig, welche die Fluiddichte in Relation zu Druck- und Temperaturbedingungen sowie der Zusammensetzung von Gemischen beschreiben. Komplexe Zustandsgleichungen, die mittels einer Vielzahl von Parametern an Realgasverhalten angepasst wurden, erreichen ein viel höheres Maß an Genauigkeit als die einfacheren, kubischen Gleichungen. Andererseits führt deren Komplexität zu sehr langen Rechenzeiten. Um die Wahl einer geeigneten Zustandsgleichung zu vereinfachen, wurde eine Sensitivitätsanalyse durchgeführt, um die Auswirkungen von Unsicherheiten in der Dichtefunktion auf die numerischen Simulationsergebnisse zu untersuchen. Die Analyse ergibt, dass bereits kleine Unterschiede in der Zustandsgleichung zu erheblichen Abweichungen der Simulationsergebnisse untereinander führen können. Als ein Kompromiss zwischen Einfachheit und Rechenaufwand wurde für die Simulation einer enhanced gas recovery-Anwendung eine kubische Zustandsgleichung gewählt. Die Simulation sieht, unter Berücksichtigung des Realgasverhaltens, die kontinuierliche Injektion von CO2 in ein nahezu erschöpftes Erdgasreservoir vor. Die Interpretation der Ergebnisse erlaubt eine Prognose über die Ausbreitungsgeschwindigkeit des CO2 bzw. über dessen Verteilung im Reservoir. Diese Ergebnisse sind für die Planung von realen Injektionsanwendungen notwendig
27
Lyu, Ying, Mark L. Brusseau, Ouni Asma El, Juliana B. Araujo e Xiaosi Su. "The Gas-Absorption/Chemical-Reaction Method for Measuring Air-Water Interfacial Area in Natural Porous Media". AMER GEOPHYSICAL UNION, 2017. http://hdl.handle.net/10150/626480.
Testo completoAbstract (sommario):
The gas-absorption/chemical-reaction (GACR) method used in chemical engineering to quantify gas-liquid interfacial area in reactor systems is adapted for the first time to measure the effective air-water interfacial area of natural porous media. Experiments were conducted with the GACR method, and two standard methods (X-ray microtomographic imaging and interfacial partitioning tracer tests) for comparison, using model glass beads and a natural sand. The results of a series of experiments conducted under identical conditions demonstrated that the GACR method exhibited excellent repeatability for measurement of interfacial area (A(ia)). Coefficients of variation for A(ia) were 3.5% for the glass beads and 11% for the sand. Extrapolated maximum interfacial areas (A(m)) obtained with the GACR method were statistically identical to independent measures of the specific solid surface areas of the media. For example, the A(m) for the glass beads is 29 (1) cm(-1), compared to 32 (3), 30 (2), and 31 (2) cm(-1) determined from geometric calculation, N2/BET measurement, and microtomographic measurement, respectively. This indicates that the method produced accurate measures of interfacial area. Interfacial areas determined with the GACR method were similar to those obtained with the standard methods. For example, A(ia)s of 47 and 44 cm(-1) were measured with the GACR and XMT methods, respectively, for the sand at a water saturation of 0.57. The results of the study indicate that the GACR method is a viable alternative for measuring air-water interfacial areas. The method is relatively quick, inexpensive, and requires no specialized instrumentation compared to the standard methods.
28
Bagudu, Usman. "Pore network modelling of gas flow processes in porous media with special application to CO2 sequestration". Thesis, Heriot-Watt University, 2015. http://hdl.handle.net/10399/2991.
Testo completoAbstract (sommario):
This thesis describes the development of a pore network model and its application to the analysis of the underlying physical mechanisms governing gas flow behaviour in porous media. The main focus of the study is CO2 and CH4 injection for EOR and storage applications as well as the evolution of solution gas following depressurization of hydrocarbon-saturated porous media. The model incorporates algorithms that dynamically track interface movements during both steady and unsteady-state flow under the coupled influence of capillary, gravity, and viscous forces. The model has been validated against laboratory experiments and the roles played by key system parameters have been identified. For injection processes, simulation results show that gravity-driven regimes fall into two broad categories of quasi-stable and migratory regimes, depending on the governing Bond number. The transition from non-dispersive to dispersive migratory flow was found to be largely independent of injection rate but a strong function of pore size distribution variance and system connectivity. CO2 and CH4 regimes in brine were found to exhibit striking similarities, suggesting that CH4-brine relative permeability curves could be used to accurately parameterize simulation models of CO2 storage in aquifers. Decreasing the interfacial tension was found to dampen viscous fingering but exacerbates gravity override which suggests that standard laboratory methods for analysing CO2 EOR processes are likely to overestimate displacement efficiency. Other sensitivity studies highlight the pore to core scale variables that control caprock sealing mechanisms, and residual and solubility trapping during CO2 injection for storage, and their implications at the reservoir scale. For depressurization, simulations performed on a pore network anchored to measured petrophysical properties of a 0.23mD fractured chalk core from a North Sea reservoir show a very weak correlation between depletion rate and critical gas saturation, contrary to conventional belief. Depressurization oil recovery efficiency was found to increase with increase in initial water saturation but the presence of fractures caused the critical saturation to decrease by approximately 60%.
29
Woods, Charles E. "Examination of the effects of biosurfactant concentration on natural gas hydrate formation in seafloor porous media". Master's thesis, Mississippi State : Mississippi State University, 2004. http://library.msstate.edu/etd/show.asp?etd=etd-07062004-202938.
Testo completo
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Totten, Christian T. "Effect of porous media and fluid properties on dense Non-Aqueous Phase Liquid migration and dilution mass flux". [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0010044.
Testo completo
31
Filippini, Maria <1986>. "Geological and hydrogeological features affecting migration, multi-phase partitioning and degradation of chlorinated hydrocarbons through unconsolidated porous media". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amsdottorato.unibo.it/6812/1/Filippini_Maria_tesi.pdf.
Testo completoAbstract (sommario):
Chlorinated solvents are the most ubiquitous organic contaminants found in groundwater since the last five decades. They generally reach groundwater as Dense Non-Aqueous Phase Liquid (DNAPL). This phase can migrate through aquifers, and also through aquitards, in ways that aqueous contaminants cannot. The complex phase partitioning to which chlorinated solvent DNAPLs can undergo (i.e. to the dissolved, vapor or sorbed phase), as well as their transformations (e.g. degradation), depend on the physico-chemical properties of the contaminants themselves and on features of the hydrogeological system. The main goal of the thesis is to provide new knowledge for the future investigations of sites contaminated by DNAPLs in alluvial settings, proposing innovative investigative approaches and emphasizing some of the key issues and main criticalities of this kind of contaminants in such a setting. To achieve this goal, the hydrogeologic setting below the city of Ferrara (Po plain, northern Italy), which is affected by scattered contamination by chlorinated solvents, has been investigated at different scales (regional and site specific), both from an intrinsic (i.e. groundwater flow systems) and specific (i.e. chlorinated solvent DNAPL behavior) point of view. Detailed investigations were carried out in particular in one selected test-site, known as “Caretti site”, where high-resolution vertical profiling of different kind of data were collected by means of multilevel monitoring systems and other innovative sampling and analytical techniques. This allowed to achieve a deep geological and hydrogeological knowledge of the system and to reconstruct in detail the architecture of contaminants in relationship to the features of the hosting porous medium.
The results achieved in this thesis are useful not only at local scale, e.g. employable to interpret the origin of contamination in other sites of the Ferrara area, but also at global scale, in order to address future remediation and protection actions of similar hydrogeologic settings.
32
Filippini, Maria <1986>. "Geological and hydrogeological features affecting migration, multi-phase partitioning and degradation of chlorinated hydrocarbons through unconsolidated porous media". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amsdottorato.unibo.it/6812/.
Testo completoAbstract (sommario):
Chlorinated solvents are the most ubiquitous organic contaminants found in groundwater since the last five decades. They generally reach groundwater as Dense Non-Aqueous Phase Liquid (DNAPL). This phase can migrate through aquifers, and also through aquitards, in ways that aqueous contaminants cannot. The complex phase partitioning to which chlorinated solvent DNAPLs can undergo (i.e. to the dissolved, vapor or sorbed phase), as well as their transformations (e.g. degradation), depend on the physico-chemical properties of the contaminants themselves and on features of the hydrogeological system. The main goal of the thesis is to provide new knowledge for the future investigations of sites contaminated by DNAPLs in alluvial settings, proposing innovative investigative approaches and emphasizing some of the key issues and main criticalities of this kind of contaminants in such a setting. To achieve this goal, the hydrogeologic setting below the city of Ferrara (Po plain, northern Italy), which is affected by scattered contamination by chlorinated solvents, has been investigated at different scales (regional and site specific), both from an intrinsic (i.e. groundwater flow systems) and specific (i.e. chlorinated solvent DNAPL behavior) point of view. Detailed investigations were carried out in particular in one selected test-site, known as “Caretti site”, where high-resolution vertical profiling of different kind of data were collected by means of multilevel monitoring systems and other innovative sampling and analytical techniques. This allowed to achieve a deep geological and hydrogeological knowledge of the system and to reconstruct in detail the architecture of contaminants in relationship to the features of the hosting porous medium.
The results achieved in this thesis are useful not only at local scale, e.g. employable to interpret the origin of contamination in other sites of the Ferrara area, but also at global scale, in order to address future remediation and protection actions of similar hydrogeologic settings.
33
Ahlinder, Stefan. "On modelling of compact tube bundle heat exchangers as porous media for recuperated gas turbine engine applications". [S.l.] : [s.n.], 2006. http://se6.kobv.de:8000/btu/volltexte/2006/15.
Testo completo
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Irizarry, Julia. "Modeling the Effects of Three-Dimensional Pore Geometry on Gas Hydrate Phase Stability". Thesis, University of Oregon, 2015. http://hdl.handle.net/1794/19304.
Testo completoAbstract (sommario):
Porous media affect hydrate stability by forcing hydrate-liquid interfaces to form high curvature geometries and by forcing the molecules of the hydrate, liquid, and sedimentary particles that compose the medium to interact where they are in close proximity. To evaluate these effects we first create synthetic spherical packings to approximate pore space geometry. We use the synthetic pore space to calculate the perturbation to the chemical potential caused by the geometrical constraints. Our model predictions agree with published data for ice-water and water-vapor systems. When particles are well-approximated as spheres, our model fits the data with R-squared values that range between about 80% to over 99%. However, our model needs to be improved for porous media that contain a significant fraction of non-equant particles such as clay. Lastly, we demonstrate how our model can be used in predictions for the evolution of hydrate saturation.
This thesis includes unpublished co-authored material.
35
Tahseen, Siddiq Husain. "Development of experimental techniques for studying gas diffusion and water transport in the porous media of fuel cells". Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/44250.
Testo completoAbstract (sommario):
Polymer Electrolyte Membrane (PEM) fuel cells, which produces electricity by oxidation of hydrogen and reduction of oxygen with water as the only waste product, have shown great potential as a zero-emission and high-efficiency source of energy. Despite the numerous advantages of the fuel cell, its performance must still be improved significantly. Numerous studies have identified water management as the major problem hindering commercialization of fuel cells. One of the components playing an important role in water management is the porous gas diffusion layer (GDL) across which reactant transport and water removal occur. Due to a long operation or large output current, the water production rate exceeds the water removal rate. As a result, water accumulates in the pores of the GDL and blocks convective and diffusive transport of reactants. This is the origin of the limiting current. To enhance water management, the reactant transport and water removal mechanisms inside the GDL needs to be thoroughly studied. Despite various numerical models developed to illustrate the multiphase flow in the cell, these mechanisms are not well understood due to the structural complexity of the GDL. In this thesis, experimental techniques are developed for the measurement of gas diffusion and water content inside the GDL. For the latter, the fluorescence microscopy technique is used to measure the pressure and time required for water to penetrate and break through the surface of the GDL. The results show that the breakthrough time and pressure are larger for hydrophobic GDLs. However, the effect of the sample thickness is found to be negligible. An innovative experimental technique is developed for the determination of the effective diffusion co-
iii
efficient as a function of the water content in the GDL. The results demonstrate that diffusivity is greater for samples with higher porosity. Also, it is shown that the presence of cracks in the micro-porous layer of the GDL increases water accumulation within the pores, reducing significantly diffusive transport within the GDL. These experimental techniques provide basic insights into the transport properties of the GDL which can lead to the design of new materials that enhance transport inside the porous media.
36
Shahraeeni, Mehdi. "Study of fluid flow in the porous media of gas diffusion layers in proton exchange membrane fuel cells". Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/44443.
Testo completoAbstract (sommario):
A proton exchange membrane (PEM) fuel cell is an energy converting system generating electricity by oxidation of hydrogen and reduction of oxygen with water and heat as the only waste products. Despite the huge market potential of the fuel cell, its performance and cost must be improved significantly before constituting a viable market. One of the major problems
of current fuel cells is water management: at energy demanding conditions where the cell is operating at high current densities, excessive water produced restricts the access of reactant gases and hence reduces the performance of the cell. To improve water management, it is necessary to study water transport mechanisms in the internal network of the cell, especially in the porous gas diffusion layer (GDL) through which transport of electrons, reactant gases, and water occurs. In this thesis, fluid flow through the GDL is studied experimentally and numerically using fluorescence microscopy and a pore network modeling approach, respectively. The images obtained from the microscope are analyzed to find patterns of flow inside the GDL samples with different hydrophobicity. Three different flow patterns are observed: initial invasion, progression, and pore-filling. The observations show that liquid water flows into the majority of available pores on the boundary of the hydrophilic (untreated) GDL and several branches segregate from the initial pathways. For the hydrophobic (treated) GDL, however, a handful of boundary pores are invaded and the original pathways extend toward the other side of the medium with minimum branching. In addition to flow visualization, the experimental setup facilitates the precise measurement of pressure and time of breakthrough which are used as boundary condition and the validation criterion for the numerical simulation, respectively. The numerical model, developed based on an invasion percolation algorithm, is used to study the effects of GDL hydrophobicity and thickness on the flow configuration and breakthrough time as well as to determine the flow rate and saturation in different GDL samples. The developed model can be used to optimize the GDL properties for designing porous medium with an effective transport characteristic.
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Montague, James. "Assessing The Probability Of Fluid Migration Caused By Hydraulic Fracturing; And Investigating Flow And Transport In Porous Media Using Mri". ScholarWorks @ UVM, 2017. http://scholarworks.uvm.edu/graddis/793.
Testo completoAbstract (sommario):
Hydraulic fracturing is used to extract oil and natural gas from low permeability formations. The potential of fluids migrating from depth through adjacent wellbores and through the production wellbore was investigated using statistical modeling and predic-tive classifiers. The probability of a hydraulic fracturing well becoming hydraulically connected to an adjacent well in the Marcellus shale of New York was determined to be between 0.00% and 3.45% at the time of the study. This means that the chance of an in-duced fracture from hydraulic fracturing intersecting an existing well is highly dependent on the area of increased permeability caused by fracturing. The chance of intersecting an existing well does not mean that fluid will flow upwards; for upward migration to occur, a pathway must exist and a pressure gradient is required to drive flow, with the exception of gas flow caused by buoyancy. Predictive classifiers were employed on a dataset of wells in Alberta Canada to identify well characteristics most associated to fluid migration along the production well. The models, specifically a random forest, were able to identify pathways better than random guessing with 78% of wells in the data set identified cor-rectly.
Magnetic resonance imaging (MRI) was used to visualize and quantify contami-nant transport in a soil column using a full body scanner. T1 quantification was used to determine the concentration of a contaminant surrogate in the form of Magnevist, an MRI contrast agent. Imaging showed a strong impact from density driven convection when the density difference between the two fluids was small (0.3%). MRI also identified a buildup of contrast agent concentration at the interface between a low permeability ground silica and higher permeability AFS 50-70 testing sand when density driven con-vection was eliminated.
38
Pham, Van Song. "Application of different model concepts for simulation of two-phase flow processes in porous media with fault zones". Aachen Shaker, 2009. http://d-nb.info/1004204205/04.
Testo completo
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Ahlinder, Stefan [Verfasser]. "On Modelling of Compact Tube Bundle Heat Exchangers as Porous Media for Recuperated Gas Turbine Engine Applications / Stefan Ahlinder". Aachen : Shaker, 2006. http://d-nb.info/1170538037/34.
Testo completo
40
Subhono, Boya. "Deploying nanotechnology for oil and gas flow assurance : understanding the transport and penetration of nano-particles in porous media". Thesis, University of Leeds, 2014. http://etheses.whiterose.ac.uk/9284/.
Testo completoAbstract (sommario):
Scaling problem is one of the common engineering challenges in ‘flow assurance’ in the oil and gas industry. Since mechanical or chemical treatment frequently requires sacrifice in fluid production, it is often preferable to avoid this problem, for example by conducting a scale squeeze treatment. This treatment includes an injection of scale inhibitor to hinder scale formation in the rock. Its effectiveness corresponds to its attachment lifetime in the rock formation. This is where nanotechnology has an important role for its capability to enhance the attachment of the scale inhibitor on the rock surface. The question that arises is how and where the injected nanoparticles are distributed and attached on the walls of the rock pores. It is difficult and costly to perform evaluations in pores of a rock formation in an actual oil field. Therefore developing a computer simulation is necessary. This research has successfully demonstrated a development of simulator to explore the science and engineering of nanoparticle transport in microchannels. The phenomenon in the system are explored using a combination of model experimental systems and novel Finite Element Analysis (FEA) computational simulations of fluid flow in microchannels of porous structures. The effect of the advection, diffusion, microchannel’s surface roughness and curvature variety to the nanoparticle transport in the system are investigated. It is discovered that the adsorption is encouraged by diffusion when the advection is insignificant. When advection is significant, a plenty of injected nanoparticle is needed to achieve similar adsorption in a system with diffusion domination. Nanoparticles are transported less effectively in microchannel with high curvature configuration. The density of the adsorption distribution in this type of microchannel is less uniform than in microchannel with simpler curvature. Rough surface increases the adsorption, where the distribution of nanoparticles into dead-end region in the microchannel system is governed by diffusion. The modelling framework in this thesis is versatile to use for modelling any transport that is coupled with surface phenomenon in microchannel system by changing the utilised governing equations and assumptions.
41
Graf, Tobias. "Multiphasic flow processes in deformable porous media under consideration of fluid phase transitions". Essen VGE-Verl, 2008. http://d-nb.info/990395316/04.
Testo completo
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Wu, Haiyi. "Multiphysics Transport in Heterogeneous Media: from Pore-Scale Modeling to Deep Learning". Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/98520.
Testo completoAbstract (sommario):
Transport phenomena in heterogeneous media play a crucial role in numerous engineering applications such as hydrocarbon recovery from shales and material processing. Understanding and predicting these phenomena is critical for the success of these applications. In this dissertation, nanoscale transport phenomena in porous media are studied through physics-based simulations, and the effective solution of forward and inverse transport phenomena problems in heterogeneous media is tackled using data-driven, deep learning approaches.
For nanoscale transport in porous media, the storage and recovery of gas from ultra-tight shale formations are investigated at the single-pore scale using molecular dynamics simulations. In the single-component gas recovery, a super-diffusive scaling law was found for the gas production due to the strong gas adsorption-desorption effects. For binary gas (methane/ethane) mixtures, surface adsorption contributes greatly to the storage of both gas in nanopores, with ethane enriched compared to methane. Ethane is produced from nanopores as effectively as the lighter methane despite its slower self-diffusion than the methane, and this phenomenon is traced to the strong couplings between the transport of the two species in the nanopore. The dying of solvent-loaded nanoporous filtration cakes by a purge gas flowing through them is next studied. The novelty and challenge of this problem lie in the fact that the drainage and evaporation can occur simultaneously. Using pore-network modeling, three distinct drying stages are identified. While drainage contributes less and less as drying proceeds through the first two stages, it can still contribute considerably to the net drying rate because of the strong coupling between the drainage and evaporation processes in the filtration cake.
For the solution of transport phenomena problems using deep learning, first, convolutional neural networks with various architectures are trained to predict the effective diffusivity of two-dimensional (2D) porous media with complex and realistic structures from their images. Next, the inverse problem of reconstructing the structure of 2D heterogeneous composites featuring high-conductivity, circular fillers from the composites' temperature field is studied. This problem is challenging because of the high dimensionality of the temperature and conductivity fields. A deep-learning model based on convolutional neural networks with a U-shape architecture and the encoding-decoding processes is developed. The trained model can predict the distribution of fillers with good accuracy even when coarse-grained temperature data (less than 1% of the full data) are used as an input. Incorporating the temperature measurements in regions where the deep learning model has low prediction confidence can improve the model's prediction accuracy.Doctor of Philosophy
Multiphysics transport phenomena inside structures with non-uniform pores or properties are common in engineering applications, e.g., gas recovery from shale reservoirs and drying of porous materials. Research on these transport phenomena can help improve related applications. In this dissertation, multiphysics transport in several types of structures is studied using physics-based simulations and data-driven deep learning models. In physics-based simulations, the multicomponent and multiphase transport phenomena in porous media are solved at the pore scale. The recovery of methane and methane-ethane mixtures from nanopores is studied using simulations to track motions and interactions of methane and ethane molecules inside the nanopores. The strong gas-pore wall interactions lead to significant adsorption of gas near the pore wall and contribute greatly to the gas storage in these pores. Because of strong gas adsorption and couplings between the transport of different gas species, several interesting and practically important observations have been found during the gas recovery process. For example, lighter methane and heavier ethane are recovered at similar rates. Pore-scale modeling are applied to study the drying of nanoporous filtration cakes, during which drainage and evaporation can occur concurrently. The drying is found to proceed in three distinct stages and the drainage-evaporation coupling greatly affects the drying rate. In deep learning modeling, convolutional neural networks are trained to predict the diffusivity of two-dimensional porous media by taking the image of their structures as input. The model can predict the diffusivity of the porous media accurately with computational cost orders of magnitude lower than physics-based simulations. A deep learning model is also developed to reconstruct the structure of fillers inside a two-dimensional matrix from its temperature field. The trained model can predict the structure of fillers accurately using full-scale and coarse-grained temperature input data. The predictions of the deep learning model can be improved by adding additional true temperature data in regions where the model has low prediction confidence.
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Didari, Sima. "Virtual modeling of a manufacturing process to construct complex composite materials of tailored properties". Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53410.
Testo completoAbstract (sommario):
Fibrous porous media are widely used in various industries such as biomedical
engineering, textiles, paper, and alternative energy. Often these porous materials are
formed into composite materials, using subsequent manufacturing steps, to improve their
properties. There is a strong correlation between system performance and the transport
and mechanical properties of the porous media, in raw or composite form. However,
these properties depend on the final pore structure of the material. Thus, the ability to
manufacture fibrous porous media, in raw or composite forms, with an engineered
structure with predictable properties is highly desirable for the optimization of the overall
performance of a relevant system. To date, the characterization of the porous media has
been primarily based on reverse design methods i.e., extracting the data from existing
materials with image processing techniques. The objective of this research is to develop
a methodology to enable the virtual generation of complex composite porous media with
tailored properties, from the implementation of a fibrous medium in the design space to
the simulated coating of this media representative of the manufacturing space. To meet
this objective a modified periodic surface model is proposed, which is utilized to
parametrically generate a fibrous domain. The suggested modeling approach allows for a
high-degree of control over the fiber profile, matrix properties, and fiber-binder
composition. Using the domain generated with the suggested geometrical modeling
approach, numerical simulations are executed to simulate transport properties such as
permeability, diffusivity and tortuosity, as well as, to directly coat the microstructure,
thereby forming a complex composite material. To understand the interplay between the
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fiber matrix and the transport properties, the morphology of the virtual microstructure is
characterized based on the pore size, chord length and shortest path length distributions
inside the porous domain. In order to ensure the desired properties of the microstructure,
the fluid penetration, at the micro scale, is analyzed during the direct coating process.
This work presents a framework for feasible and effective generation of complex porous
media in the virtual space, which can be directly manufactured.
44
Howard, Brandon Daniel. "Shear and Composition Effects on Porous Network Properties and the Permeability of Lipid Films". The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1593680466745792.
Testo completo
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Thomas, Lee W. "Three-phase dynamic displacement measurements of relative permeability in porous media using three immiscible liquids : a thesis in Petroleum and Natural Gas Engineering". Thesis, Monterey, California. Naval Postgraduate School, 1991. http://hdl.handle.net/10945/26302.
Testo completo
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Raed, Khaled [Verfasser], Ulrich [Akademischer Betreuer] Gross, Ulrich [Gutachter] Gross e Ulf [Gutachter] Hammerschmidt. "Investigation of Knudsen and gas‐atmosphere effects on effective thermal conductivity of porous media / Khaled Raed ; Gutachter: Ulrich Gross, Ulf Hammerschmidt ; Betreuer: Ulrich Gross". Freiberg : Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2013. http://d-nb.info/122069875X/34.
Testo completo
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Oladyshkin, Sergey. "Découplage de la thermodynamique et hydrodynamique et solutions asymptotiques des problèmes d'écoulement compositionnel gaz-liquide en milieux poreux". Thesis, Vandoeuvre-les-Nancy, INPL, 2006. http://www.theses.fr/2006INPL059N/document.
Testo completoAbstract (sommario):
Le travail actuel traite le problème de l'écoulement gaz-liquide compositionnel pour la représentation d'un puits dans des simulations de réservoir. L'objectif est de développer les rapports analytiques qui pourraient lier la pression de puits, la saturation et les concentrations de composant à leurs valeurs moyennes dans chaque zone de l'influence de puits. Nous avons montre que des N-2 équations décrivant le transport des concentrations de phase peuvent être transformées en équations ordinaires (différentiation en ce qui concerne la pression) indépendantes du temps et de l'espace examinant le long des lignes de courant. Ces équations transformées représentent des relations thermodynamiques additionnelles réduisant le degré de liberté thermodynamique. En raison de ceci le variance thermodynamique du modèle compositionnel limite s'avère égal à 1 pour tout nombre de composants chimiques. Cette transformation assurent se découplage total du modèle compositionnel limite dans le nouveau modèle thermodynamique et le modèle hydrodynamique, qui peut être resoved inedpendently d'un un autre. Le modèle thermodynamique décompose est totalement indépendant sur l'hydrodynamique, et décrit le comportement d'équilibre d'un système gaz-liquide ouvert. Ce modèle contient les équations d'équilibre et la EOS classiques, aussi bien que les N-2 nouvelles équations appelées la "Delta-loi", qui déterminent la variation de composition d'un système ouvert dans lequel la masse de chaque composant n'est pas conservée. Le modèle hydrodynamique décompose a été utiliser pour développer les solutions asymptotiques des problèmes d'écoulement de gaz-condensat. Le problème a été montré perturbé singulièrement avec la formation d'une couche limite à voisinage du puits. Dans cette couche la propriété basique de contraste des mobilities de gaz et de liquide est perturbée. On développe une technique spéciale qui permet de construire des expansions asymptotiques sous forme de deux diverses séries: le primer est valide loin du puits (l'expansion extérieure), alors que le second dans valide à voisinage du puits (la couche limite ou l'expansion intérieure). En appliquant la méthode asymptotique suggérée, nous avons développé les solutions asymptotiques pour le problème de l'écoulement multicompositionnel de gaz-condensat àu puits dans un domaine borné à un débit variable. En plusieurs cas la solution peut être obtenue sous la forme analytique, alors qu'en cas général de l'écoulement la méthode mène à une solution de semi-analytical, présentée comme problème initial pour une équation. Cette solution, même étant présenté en forme non-analytique, est beaucoup plus simple que le modèle compositionnel original, car l'équation pour la saturation ne dépend pas de la pression locale, mais dépend de la pression de bord seulement. Dans le dernier chapitre nous avons prolongé cette approche au cas quand la pression capillaire n'est pas négligée. Nous avons supposé cependant que les forces capillaires sont inférieures à la différence de pression entre le puits et la bord de réservoir, dus à ce que nous avons appliqué la méthode de perturbation pour petit nombre capillaire inverse. On obtient les solutions asymptotiques améliorées qui tiennent compte de l'effet capillaire. Simulations numériques montrées que ces effets sont maximaux àu voisinage du puits. Le cas d'une exploitation à long terme du réservoir. Tout d'abord, la simulation traditionnelle du comportement de réservoir peut être effectuée avec l'ECLIPSE en ajoutant la méthode de Peaceman de représentation bonne, qui est une relation analytique pour la pression de puits par l'intermédiaire du débit de production. Cette relation inclut une saturation condensat qui peut être évaluée comme saturation moyenne de réservoir. Une telle simulation fournit un bon résultat pour la pression de puits (ou le débit de production), et un bon résultat pour la saturation de bord, mais des données faibles pour la saturation de puits. Cette valeur peut être calculée en utilisant les solutions asymptotiques suggérées dans le présent projet. Le cas d'un puits de production à court terme (un essai de puits). Il est suffisant de simuler le comportement de réservoir dans le domaine de l'influence de puits, en supposant que l'état de frontière demeure invariable (et connu a priori). Dans ce cas-ci les solutions asymptotiques suggérées dans le travail de presnet peuvent être directement employées pour simuler le problème (sans employer l'ECLIPSE). Le problème de l'écoulement de gaz-condensat à une fracture. Nous avons construit un champ plutôt arbitraire avec des lignes de courant orientées à la fracture, en supposant que la fracture joue le rôle d'une décharge, et les lignes de courant sont stationnaire. Pour une ligne de courant arbitraire nous avons reformulé le modèle d'écoulement de gaz-condensat dans des coordonnées cartésiennes. Pour ce problème nous avons développé les expansions asymptotiquesThe present work deals with the problem of the compositional gas-liquid flow for the well representation in reservoir simulations. The objective is to develop analytical relationships which would be able to link the wellbore pressure, saturation and component concentrations to their mean values within each zone of the well influence. It is shown that N-2 equations describing the transport of phase concentrations can be transformed into the space- and time-independent ordinary differential equations (differentiation with respect to pressure) when examined along flow streamlines. These transformed equations represent additional thermodynamic relations reducing the thermodynamic degree of freedom. Due to this the thermodynamic variance of the limit compositional model is shown to be equal to 1 for any number of chemical components. This transformation ensure a total splitting of the limit compositional model into the new thermodynamic model and a hydrodynamic model, which may be resoved inedpendently of one another. The split thermodynamic model is totally independent on the hydrodynamic one, and describes the equilibrium behaviour of an open gas-liquid system. This model contains the classic equilibrium equations and EOS, as well as N-2 new differential equations called the "delta-law" which determine the composition variation in an open system, in which the mass of each component is not conserved. The split hydrodynamic model consists of two equations for pressure and saturation. The split hydrodynamic model was used to develop asymptotic solutions of gas-condensate flow problems. The problem was shown to be singularly perturbed with formation of a boundary layer in the vicinity of the well. In this layer the basic contrast property of gas and liquid mobilities is perturbed. A special technique is developed which enables to construct asymptotic expansions in the form of two various series, one of them is valid far from the well (the exterior expansion), while the second one in valid in the vicinity of the well (the boundary-layer or interior expansion). By applying the suggested asymptotic method, we have developed the asymptotic solutions for the problem of multi-component gas-condensate flow to a well in a bounded domain at a variable flow rate. In several cases the solution may be obtained in the analytical form, while in general case of flow the method leads to a semi-analytical solution presented as an initial problem for a differential equation. This solution, even being presented in non-analytical form, is much simpler than the original compositional model, as the equation for saturation does not depend on the local pressure, but on the boundary pressure only. In the last chapter we extended this approach to the case when the capillary pressure is not neglected. We assumed however that the capillary forces are lower than the pressure difference between the wellbore and reservoir boundary, due to which we applied the perturbation method over the small inverse capillary number. The improved asymptotic solutions are obtained which take into account the capillary effect. Numerical simulations shown that these effects are maximal in the vicinity of the well. For the practice, the obtained asymptotic solutions may be used in the following way to resolve the problem of gas-condensate well representation. The case of a long-term exploitation of the reservoir}. First of all, the traditional simulation of the reservoir behaviour can be performed with ECLIPSE by adding the Peaceman method of well representation, which is an analytical relation for the wellbore pressure via the production rate. This relation includes a condensate saturation which can be evaluated as a mean reservoir saturation. Such a simulation provides a good result for the wellbore pressure (or the production rate), and a good result for the boundary saturation, but poor data for the wellbore saturation. This value can be calculated next by using the asymptotic solutions suggested in the presented project. The case of a short-term well production (a well test). It is sufficient to simulate the reservoir behaviour in the domain of the well influence, by assuming that the boundary state remains invariable (and known a priori). In this case the asymptotic solutions suggested in the presnet work can be directly used to simulate the problem (without using ECLIPSE)
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Bullara, Domenico. "Nonlinear reactive processes in constrained media". Doctoral thesis, Universite Libre de Bruxelles, 2015. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209073.
Testo completoAbstract (sommario):
In this thesis we show how reactive processes can be affected by the presence of different types of spatial constraints, so much so that their nonlinear dynamics can be qualitatively altered or that new and unexpected behaviors can be produced. To understand how this interplay can occur in general terms, we theoretically investigate four very different examples of this situation. The first system we study is a reversible trimolecular chemical reaction which is taking place in closed one-dimensional lattices. We show that the low dimensionality may or may not prevent the reaction from reaching its equilibrium state, depending on the microscopic properties of the molecular reactive mechanism.
The second reactive process we consider is a network of biological interactions between pigment cells on the skin of zebrafish. We show that the combination of short-range and long-range contact-mediated feedbacks can promote a Turing instability which gives rise to stationary patterns in space with intrinsic wavelength, without the need of any kind of motion.
Then we investigate the behavior of a typical chemical oscillator (the Brusselator) when it is constrained in a finite space. We show that molecular crowding can in such cases promote new nonlinear dynamical behaviors, affect the usual ones or even destroy them.
Finally we look at the situation where the constraint is given by the presence of a solid porous matrix that can react with a perfect gas in an exothermic way. We show on one hand that the interplay between reaction, heat flux and mass transport can give rise to the propagation of adsorption waves, and on the other hand that the coupling between the chemical reaction and the changes in the structural properties of the matrix can produce sustained chemomechanical oscillations.
These results show that spatial constraints can affect the kinetics of reactions, and are able to produce otherwise absent nonlinear dynamical behaviors. As a consequence of this, the usual understanding of the nonlinear dynamics of reactive systems can be put into question or even disproved. In order to have a better understanding of these systems we must acknowledge that mechanical and structural feedbacks can be important components of many reactive systems, and that they can be the very source of complex and fascinating phenomena.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
49
Gayton, Elisabeth Faye. "Experimental and numerical investigation of the thermal performance of the gas-cooled divertor plate concept". Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26517.
Testo completoAbstract (sommario):
Thesis (M. S.)--Nuclear Engineering, Georgia Institute of Technology, 2009.Committee Chair: Abdel-Khalik, Said; Committee Co-Chair: Yoda, Minami; Committee Member: Ghiaasiaan, S. Mostafa. Part of the SMARTech Electronic Thesis and Dissertation Collection.
50
Khaddour, Fadi. "Amélioration de la production de gaz des « Tight Gas Reservoirs »". Thesis, Pau, 2014. http://www.theses.fr/2014PAUU3005/document.
Testo completoAbstract (sommario):
La valorisation des réservoirs gaziers compacts, dits Tight Gas Reservoirs (TGR), dont les découvertes sont importantes, permettrait d’augmenter significativement les ressources mondiales d’hydrocarbures. Dans l’objectif d’améliorer la production de ces types de réservoirs, nous avons mené une étude ayant pour but de parvenir à une meilleure compréhension de la relation entre l’endommagement et les propriétés de transport des géomatériaux. L’évolution de la microstructure d’éprouvettes qui ont été soumises préalablement à des chargements dynamiques est étudiée. Une estimation de leurs perméabilités avec l’endommagement est tout d’abord présentée à l’aide d’un modèle de pores parallèles couplant un écoulement de Poiseuille avec la diffusion de Knudsen. Nous avons ensuite mené des travaux expérimentaux afin d’estimer l’évolution de la perméabilité avec l’endommagement en relation avec l’évolution de la distribution de tailles de pores. Les mesures de perméabilité sont effectuées sur des cylindres en mortier similaire aux roches tight gas, soumis à une compression uniaxiale. La caractérisation des microstructures des mortiers endommagés est réalisée par porosimétrie par intrusion de mercure. Afin d’estimer l’évolution de la perméabilité, un nouveau modèle hiérarchique aléatoire est présenté. Les comparaisons avec les données expérimentales montrent la capacité de ce modèle à estimer non seulement les perméabilités apparentes et intrinsèques mais aussi leurs évolutions sous l’effet d’un chargement introduisant une évolution de la distribution de taille de pores. Ce modèle, ainsi que le dispositif expérimental employé, ont été étendus afin d’estimer à l’avenir les perméabilités relatives de mélanges gazeux. Le dernier chapitre présente une étude de l’adsorption de méthane dans différents milieux fracturés par chocs électriques. Les résultats, utiles pour l’estimation des ressources en place, ont montré que la fracturation permet de favoriser l’extraction du gaz initialement adsorbéThe valorization of compact gas reservoirs, called tight gas reservoirs (TGR), whose discoveries are important, would significantly increase the global hydrocarbon resources. With the aim of improving the production of these types of gas, we have conducted a study to achieve a better understanding of the relationship between damage and the transport properties of geomaterials. The microstructure evolution of specimens, which were submitted beforehand to dynamic loading, has been investigated. An estimation of their permeability upon damage is first presented with the help of a bundle model of parallel capillaries coupling Poiseuille flow with Knudsen diffusion. Then, we have carried out an experimental work to estimate the permeability evolution upon damage in relation to the evolution of the pore size distribution in uniaxial compression. The measurements of permeability have been performed on mortar cylinders, designed to mimic typical tight rocks that can be found in tight gas reservoirs. Microstructural characterization of damaged mortars has been performed with the help of mercury intrusion porosimetry (MIP). To estimate the permeability evolution, a new random hierarchical model has been devised. The comparisons with the experimental data show the ability of this model to estimate not only the apparent and intrinsic permeabilities but also their evolutions under loading due to a change in the pore size distribution. This model and the experimental set up have been extended to estimate the relative permeabilities of gas mixtures in the future. The final chapter presents a study of the adsorption of methane on different porous media fractured by electrical shocks. The results, concerning the estimation of the in-place resources, have shown that fracturing can enhance the extraction of the initial amount of adsorbed gas