O presente trabalho apresenta um estudo associado à separação de gás para escoamento gás-líquido em um duto anular inclinado. Esse tipo de escoamento e geometria são encontrados em separadores de gás do tipo shroud invertido na indústria de petróleo quando utilizadas técnicas de bombeamento para a exploração de poços. A presença de gás livre a montante da bomba é uma das maiores limitações dos sistemas de bombeamento, por acarretar cavitação e falhas dinâmicas nos equipamentos. O presente estudo tem por objetivo garantir a separação total de gás livre a montante da bomba através da proposição de um separador do tipo shroud invertido em tubulação inclinada para aplicação na exploração de petróleo em poços direcionais. Um estudo experimental com ar e água como fluidos de trabalho a pressão quase atmosférica foi desenvolvido visando a compreensão da fenomenologia do separador shroud invertido. Foram observados escoamentos em duto anular do tipo: bifásico gás-líquido ascendente, monofásico em canal livre e bifásico gás-líquido descendente devido ao fenômeno de aeração; foram coletados também dados de eficiência de separação em função do ângulo de inclinação, vazão do líquido e queda de pressão entre o shroud e a saída do tubo de produção. Encontrou-se uma variável de extrema importância no fenômeno de separação até agora não reportada na literatura: o nível do anular interno do shroud (NAI). Um modelo fenomenológico que prevê a separação total do gás foi desenvolvido a partir da interpretação dos fenômenos físicos observados experimentalmente. Uma correlação inédita para a modelagem do fenômeno de dissipação de energia cinética turbulenta vinculado à separação do gás é proposta. O modelo foi validado qualitativamente com dados da literatura e ajustado com os dados coletados neste trabalho, mostrando boa concordância. / This paper presents a study associated with gas separation in an inclined gas-liquid annular-duct flow. This type of flow and geometry are found in shroud-inverted gas separators applied to petroleum industries when using pumping technique for oil production. High void fraction at the pump suction of is one of the most important limitations of the SCP technique, causing cavitation and dynamics failures in the equipment. The present study aims to provide a solution for the total gas separation through the use of an innovative inclined inverted-shroud separator for directional wells. An experimental study, where air and water at near atmospheric pressure constituted the working fluids, was carried out to understand the phenomenology of the inclined inverted-shroud separator. Different annular-duct flows were observed: upward gas-liquid flow, single-phase open channel flow, downward gas-liquid flow due to the phenomenon of aeration; also new data of separation efficiency were collected as a function of inclination angle, liquid flow rate and pressure drop between the shroud and production pipe outlet. One of the most significant findings is that the liquid level of the inner annular channel (NAI) of the shroud is a very important variable in the phenomenon of separation; so far this was not reported in the literature. Based on the observations, a phenomenological model that predicts total gas separation is proposed. A new correlation for the modeling of the dissipation of turbulent kinetic energy associated with the gas separation is presented. The model was qualitatively compared with available data from the literature and quantitatively adjusted against the new experimental data obtained in this work, and the agreement was quite good.

Operações de produção de petróleo, que utilizam sistemas de bombeamento centrífugo submerso, constantemente encontram a presença de gás livre nos poços, o que pode gerar ou agravar problemas como cavitação e falhas dinâmicas, quando o gás é succionado pela bomba. O separador gravitacional do tipo shroud invertido é uma solução possível para este problema nos casos de operação em poços direcionais de petróleo. O trabalho tem como objetivo apresentar um estudo do diâmetro das bolhas que ocorrem no interior de um separador gravitacional gás-líquido do tipo shroud invertido. A finalidade é o aprimoramento de um modelo fenomenológico do funcionamento deste tipo de separador, aplicado à indústria petrolífera, sendo que o modelo fenomenológico garante total separação de gás, fornecidas determinadas condições. O modelo prevê, através do cálculo da energia cinética turbulenta, o tamanho médio das bolhas carregadas para o seio do líquido por aeração no duto anular. Partindo de estudos anteriores, uma verificação do modelo fenomenológico foi feita utilizando um aparato experimental com misturas bifásicas ar-água e ar-óleo em três diferentes inclinações. O aparato possui dimensões radiais reais de um poço de petróleo offshore. Foi utilizado um sensor 3D ORM para a medição do tamanho médio (sauter) das bolhas arrastadas pelo líquido até a entrada do tubo de produção, em diversas combinações de vazões da mistura água-ar. Esta medição permite o ajuste das correlações que regem o modelo fenomenológico, no que diz respeito às equações dependentes do diâmetro teórico de bolhas arrastadas pela fase líquida. As descobertas provenientes deste estudo foram implementadas em um código computacional que será utilizado pela PETROBRAS, financiadora do projeto, para suas operações de bombeamento. / Oil mining operations powered by centrifugal submersible pumping systems suffer constant setbacks due to the presence of free gas in wells. Decompression in the reservoir liberates this gas in the form of bubbles that, upon reaching the suction end of the pump, cause cavitation and dynamic failures resulting in production and equipment losses. The Inverted-shroud gravitational separator is a possible solution to this problem. This work presents a study on diameters of bubbles that occur inside this separator. The goal is the improvement of the understanding of this kind of separator as well as the enhancement of a previously reported phenomenological model, which ensures total gas separation when the separator is installed in directional wells and under specific operational conditions. Empirically adjusted correlations are used to ensure that all entrained bubbles do not reach the pump. The model was tested for two-phase flows of water-air and oil-air mixtures using three different inclinations. Tests were performed with an experimental apparatus that simulates a pilot-scale well casing with an inverted-shroud separator installed. A 3D ORM particle-size sensor was employed in order to measure the average (sauter) diameter of entrained bubbles that are dragged by the liquid flow towards the end of the production tube. This investigation will be used to improve the reliability of the phenomenological model and reduce its dependency on a theoretical prediction of the bubble size. The findings were incorporated to the final version of an in-house gas separator design software developed at the request of PETROBRAS, the project funder and Inverted-shroud patent holder, for usage on its oil mining operations.

Actuellement, la production d’énergie est de plus en plus associée à une hausse simultanée d’émissions de Gaz à Effet de Serre (GES). Malgré les inquiétudes concernant les GES dans l’atmosphère, les énergies fossiles resteront probablement longtemps la principale source d’énergie primaire à l’échelle mondiale. Le procédé de captage de CO2, principal gaz à effet de serre, généralement préconisé est un procédé d’absorption chimique avec de la monoéthanolamine (MEA). Ce procédé pose de nombreux problèmes comme le coût de la régénération de l’amine. Cette étude s’intéresse à une alternative consistant à absorber chimiquement le dioxyde de carbone dans une solution aqueuse d’ammoniac. Par ailleurs, dans le but d’améliorer les procédés de captage et d’intensifier le transfert gaz-liquide, des techniques de captage à base de membranes (contacteurs membranaires) ont été développées et couplées à l’absorption chimique. Dans un premier temps des mesures d’absorption du CO2 à partir d’une solution aqueuse d’ammoniac ont été réalisées. Ces mesures ont été effectuées entre 278 et 303 K dans un réacteur fermé de type cellule de Lewis. Le taux de charge maximum, la pression partielle du CO2 à l’équilibre ont été déterminés. Les performances ont été comparées à celles de solvants conventionnels tels que la MEA et la N-méthyldiéthanolamine (MDEA). Dans un second temps, des mesures d’absorption à travers un contacteur membranaire ont été réalisées. L’efficacité de captage est étudiée en fonction de la nature des matériaux constituants la membrane et des paramètres opératoires. Les résultats obtenus montrent qu’il est possible de capter le CO2 par l’ammoniaque à travers une membrane avec une efficacité de captage supérieure à 90 %. La membrane limite les pertes d’ammoniaque mais ne les élimine pas. La simulation du fonctionnement de la centrale thermique alimentée au charbon pulvérisé (CP) intégrant le captage de CO2 a été réalisée à l’aide du logiciel Aspen Plus. Les fumées issues de la post-combustion sont captées par différents solvants. Une étude paramétrique a été conduite afin de préciser les conditions optimales pour capter le CO2 par l’ammoniaque. Des comparaisons de dépense énergétique dans le cas de la régénération pour les solvants NH3, MEA et MDEA ont été réalisées. L’étude comparative suggère que l’absorption chimique utilisant l’ammoniaque comme solvant est un des procédés les plus intéressants pour la centrale CP. / Nowadays rising energy production is associated with increasingly greenhouse gases (GHG) emissions. Despite of concerns about GHG emissions in atmosphere, fossil fuels will probably remain the main source of primary energy for a long time. The process of CO2 (the main greenhouse gas) capture, generally recommended is the chemical absorption with monoethanolamine (MEA). This process has many problems such as the regeneration cost of amine. This study examines an alternative which consists in absorbing carbon dioxide by ammonia aqueous solution. Moreover, membranes have been developed and coupled to chemical absorption to improve the capture processes and to intensify the gas-liquid transfer. Firstly measurements of CO2 absorption from an aqueous ammonia solution have been conducted. These measurements have been made between 278 and 303 K in a closed reactor type Lewis cell. Maximum CO2 loading, CO2 partial pressure at equilibrium have been determined. The solvents performances have been compared with respect to conventional solvents such as MEA and N-methyldiethanolamine (MDEA). Secondly absorption measurements through a membrane contactor have been made. The influence of the material nature constituting the membrane and operating parameters on the capture efficiency has been studied. The results have shown that it is possible to capture CO2 from ammonia through a membrane with a capture efficiency greater than 90 %. The membrane limits ammonia losses but does not eliminate it. Operation simulation of the thermal power plant fed with pulverized coal (CP) including CO2 capture has been performed using the software Aspen Plus. The flue gases containing CO2 from post-combustion have been captured by different solvents. A parametric study has been conducted to clarify the optimal conditions to capture CO2 by ammonia. Comparisons of energy consumption in the case of solvent regeneration for NH3,MEA andMDEA have been performed. The comparative study suggests that the use of ammonia as a solvent in chemical absorption is the most interesting process for the central CP.

A system able to simultaneously separate and pump a gas-liquid mixture was developed.<p>It works efficiently and can be used in many applications (nuclear power plants,<p>pulp and paper processing, petroleum extraction, etc.). However, this pump and separator<p>system (PASS) was especially designed to handle air-oil mixture generated in<p>aero-engine lubrication systems. The PASS combines three important functions of the<p>scavenge part of the lubrication system: the deaeration and deoiling of the air-oil mixture<p>generated in the bearing and gearbox sumps and the pumping of the oil towards<p>the tank. These are critical functions for the engine. Indeed, a poor deoiling efficiency<p>leads to a high oil consumption. This reduces the flight endurance, increases the size<p>and weight of the oil tank and has a negative impact on the environment. Poor deaeration<p>and pumping characteristics lead to problems in the cooling and the lubrication of<p>the engine bearings.<p><p>Integrating a PASS into the lubrication system allows considerable improvements<p>(and simplification) to the lubrication system architecture. An important number of<p>components are suppressed: the vent lines, the deoiler, the cyclone deaerator and the<p>scavenge pumps. This reduces the size and the weight of the lubrication system and<p>increases its reliability. Furthermore, an important part of this PhD thesis focuses on<p>reducing the oil consumption in the PASS. This improves the flight endurance, reduces<p>engine maintenance and working costs and is profitable to the environment.<p><p>In addition to the development of an advanced PASS design system, the objective of<p>this thesis was to obtain a good understanding of the separation processes occurring in<p>the PASS and to develop theoretical models able to predict the separation performance<p>for every working condition encountered in a typical aircraft flight. To achieve this<p>goal, three main tasks were performed: the development of different two-phase measurement<p>systems, the experimental tests of four different PASS architectures and the<p>theoretical development (after an extensive literature review) of correlations predicting<p>the performance of the PASS in function of the working conditions. Five specific aspects<p>of the PASS were studied: the inlet flow, the deoiling efficiency, the deaeration efficiency,<p>the pumping efficiency and the pressure drop. Finally, the models that have been developed<p>with the help of the measurement systems and of the experiments have been<p>integrated in a complete model of the lubrication system (under the EcosimPro modelling<p>environment). This helps to predict real in flight PASS working conditions and<p>performance. Indeed, the PASS is very sensitive to the engine working conditions and<p>an optimisation of the prototype size and performance is only feasible with an accurate<p>knowledge of these working conditions and a complete lubrication system model.<p>Finally, with the results of this PhD thesis, a new PASS design, optimised for different<p>aero-engine lubrication systems, is presented. / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished

Doctor of Philosophy / Department of Grain Science and Industry / Finlay I. MacRitchie / Expansion of dough and hence breadmaking performance is postulated to depend on a dual mechanism for stabilization of inflating gas bubbles. Two flours were used in this study, one from the wheat variety Jagger (Jagger) and the other from a composite of soft wheat varieties (soft). The primary stabilizing mechanism is due to the gluten-starch matrix surrounding the bubble. The secondary mechanism operates when gas bubbles come into close contact during later proofing and early baking. When discontinuities occur in the gluten-starch matrix surrounding gas bubbles, thin liquid lamellae stabilized by adsorbed surface active compounds, provide a secondary stabilization. A key parameter in the primary stabilizing dough film is thought to be the property of strain hardening. Jagger flour gave higher test-bake loaf volume than soft wheat flour and higher strain hardening index for dough. Rheological properties of doughs were varied by addition of protein fractions prepared by pH fractionation. Fractions were characterized by SE-HPLC and MALLS. The molecular weight distribution (MWD) of fractions progressively shifted to higher values as the pH of fractionations decreased. Mixograph peak development time paralleled the MWD. However, the strain hardening index and the test-bake loaf volume increased with increasing MWD up to a point (optimum), after which they declined. At a given strain rate the behavior at the optimum appeared to result from slippage of the maximum number of statistical segments between entanglements, without disrupting the entangled network of polymeric proteins. Shift of MWD to MW higher than the optimum results in a stronger network with reduced slippage through entanglement nodes, whereas a shift to lower MWs will decrease the strength of the network due to less number of entanglements per chain. In order to study the secondary stabilizing mechanism, different lipid fractions were added incrementally to the defatted flours. No effects were observed on the rheological properties of the dough. However, large effects on the loaf volume were measured. The additives used were the total flour lipid and its polar and non polar fractions and the fatty acids palmitic, linoleic and myristic. Polar lipids and palmitic acid had positive or little effect on loaf volume respectively. Non polar lipid, linoleic and myristic acids had negative effects on loaf volume. 1 The different effects of the lipid fractions are thought to be related to the type of monolayer that is formed. Polar lipid and palmitic acid form condensed monolayers at the air/water interface whereas non polar lipid, linoleic and myristic acids form expanded monolayers.

[pt] O deslocamento de um líquido em um tubo capilar pela injeção de um gás ocorre em muitas situações, tais como na recuperação avançada de petróleo, no revestimento de conversores catalíticos e na moldagem assistida por injeção de gás. Geralmente o líquido deslocado é uma solução polimérica ou uma dispersão, que é não Newtoniana. Forças viscoelásticas alteram o balanço de forças em várias partes do escoamento e, conseqüentemente, alteram a eficiência do deslocamento, isto é, mudam a quantidade de líquido deixada na parede do capilar. Modelos de tais escoamentos devem se basear em teorias que levem em consideração o comportamento diferenciado de líquidos com microestrutura complexa, tanto no cisalhamento quanto na extensão. Além do mais, escoamentos de deslocamento envolvem uma superfície livre, e o domínio no qual as equações diferenciais são resolvidas é desconhecido a priori, fazendo parte da solução. Estas duas características tornam o problema extremamente complexo. Este problema foi estudado aqui tanto experimentalmente quanto teoricamente. Os experimentos consistiram da visualização do escoamento e medição da massa deslocada pela passagem de uma bolha de gás através de um tubo capilar preenchido por um líquido viscoelástico. Várias soluções de baixo peso molecular de Polietileno Glicol (PEG) e de alto peso molecular de Óxido de Polietileno (PEO) em água foram usadas a fim de avaliar os efeitos do comportamento viscoelástico no escoamento. As propriedades reológicas das soluções foram avaliadas tanto em cisalhamento quanto em extensão. Na análise teórica, o escoamento com superfície livre bidimensional próximo µa interface gás- líquido foi modelado usando três equações diferenciais constitutivas distintas que aproximam o comportamento viscoelástico de soluções poliméricas diluídas, as quais são os modelos Oldroyd-B, FENE-P e FENE-CR, juntamente com as equações de conservação de massa e de quantidade de movimento linear. O sistema de equações foi resolvido pelo Método dos Elementos Finitos. O sistema de equações algébricas não-lineares resultante foi resolvido pelo método de Newton. Os resultados mostram o efeito do caráter viscoelástico do líquido na forma da superfície livre e a espessura do filme líquido deixado na parede. / [en] Displacement of a liquid in a capillary tube by gas injection occurs in many situations, like enhanced oil recovery, coating of catalytic converters and gas-assisted injection molding. Generally the liquid being displaced is a polymeric solution or dispersion, which is not Newtonian. Viscoelastic forces alter the force balance in various parts of the flow and consequently change the amount of liquid left attached to the capillary wall. Models of such flows must rely on theories that can account for the different behavior of microstructured liquids in simple shear and extensional flow. Moreover, displacement flows involve a free surface, and the domain where the differential equations are posed is unknown a priori being part of the solution. These two characteristics make the problem extremely complex. This problem was analyzed here both by experiments and theory. The experiments consisted of flow visualization and measurement of mass displaced by a gas bubble in a capillary tube filled with a viscoelastic liquid. Various solutions of low molecular weight Polyethylene Glycol (PEG) and high molecular weight Polyethylene Oxide (PEO) in water were used in order to evaluate the effect of viscoelastic behavior on the flow. The rheological properties of the solutions were evaluated both in simple shear and predominantly extensional flows. In the theoretical analysis, the two- dimensional free surface flow near the gas-liquid interface was modelled using three different differential constitutive equations that approximate viscoelastic behavior of dilute polymer solutions, namely Oldroyd-B, FENE-P and FENE-CR, together with momentum and continuity equations. The equation system was solved with the Finite Element Method. The resulting non- linear system of algebraic equations was solved by Newton`s method. The results show the effect of the viscoelastic character of the liquid on the free surface shape and the film thickness attached to the capillary wall.

[pt] Campos de petróleo com gás não associado do tipo gás condensado possuem destaque pelo maior valor econômico agregado associado a seu recurso energético: a expressiva quantidade de condensado produzida, além do próprio gás. Porém, tais reservatórios possuem um comportamento termodinâmico particular, induzindo mudanças de composição e, consequentemente, fase ao longo do processo de produção por depleção. Nas condições de reservatório, por exemplo, pode ocorrer o fenômeno chamado de condensate blockage, em que bancos de condensado se formam, geralmente em regiões próximas aos poços, dificultando assim o escoamento e afetando a produção de gás. A fim de definirmos a melhor estratégia de gerenciamento de um projeto a ser implementado ao longo da explotação desse tipo de reservatório, uma ferramenta importante utilizada pelos engenheiros é a simulação numérica. Especialmente relacionadas à representação do fenômeno físico-químico citado, nas simulações se utilizam as curvas de permeabilidade relativa. Na realidade, porém, existe uma certa limitação de representatividade do fenômeno nos ensaios laboratoriais praticados pela indústria e os melhores insumos poderiam ser fornecidos por simulações em rede de poros, com modelos que representem a sua alteração com função das mudanças na tensão interfacial e na velocidade de escoamento ao longo do reservatório. A reprodução de uma simulação de escoamento em rede de poros para a escala mais próxima possível em uma simulação de simulador comercial de diferenças finitas é validada. Da simulação em rede de poros até a escala de campo praticada nas simulações de reservatórios, uma metodologia de scale-up é proposta, utilizando um processo de otimização, procurando ser fiel à curva de permeabilidade relativa original, em escala de microporo, obtida simulando fenomenologicamente o processo de condensação no reservatório, através de um modelo que reproduza sua dependência com a velocidade desenvolvida pelas fases em meio poroso. A comparação de produtividades na escala de campo e na evolução da saturação de condensado em regiões próximas aos poços foi apresentada para as três curvas de permeabilidade relativa utilizadas. Os resultados mostram que a metodologia proposta consegue ser mais fiel à influência da condensação no reservatório sobre a produtividade dos poços quando comparada ao insumo de curva de permeabilidade relativa de ensaio laboratorial que apresenta o condensado mais móvel. / [en] Oil fields with non-associated gas like gas condensate type stand out due to the higher added economic value associated with their energy resource: the significant amount of condensate produced, in addition to the gas itself. However, such reservoirs have a particular thermodynamic behavior, inducing changes in composition and, consequently, phase throughout the depletion production process. Under reservoir conditions, for example, the phenomenon called condensate blockage may occur, in which bridges of condensate are formed, usually in regions close to the wells, thus hindering flow and affecting gas production. In order to define the best management strategy for a project to be implemented throughout the exploitation of this type of reservoir, an important tool used by engineers is numerical simulation. The relative permeability curves are used in the simulations, especially related to the representation of the mentioned physical phenomenon. In reality, however, there is a specific limitation of representativeness of the phenomenon in the laboratory tests carried out by the industry, and the best inputs could be provided by simulations in a pore network, with models that represent its alteration as a function of changes in interfacial tension and flow velocity along the reservoir. The reproduction of a pore network flow simulation to the closest possible scale in a commercial finite difference simulation is validated. From the pore network simulation to the field scale practiced in reservoir simulations, a scale-up methodology is proposed, using an optimization process, seeking to be faithful to the original relative permeability curve, on a microporous scale, obtained by simulating phenomenologically the condensation process in the reservoir, using a model that reproduces its dependence on the velocity flow developed by the phases in a porous medium. The three relative permeability curves used were presented by comparing productivities at the field scale and the evolution of condensate saturation in regions close to the wells. The results show that the proposed methodology proves to be more faithful to the influence of condensation in the reservoir on the productivity of the wells when compared to the relative permeability curve input from the laboratory test, which presents the condensate with more mobility.

La micro-oxygénation des vins, par la dispersion de bulles d’oxygène, est une pratique de plus en plus utilisée dans le domaine de l’œnologie. Cette technique n’est pas toujours convenablement maitrisée par manque de connaissances scientifiques sur les paramètres régissant le transfert de l’oxygène. La recherche s'est focalisée sur l'étude des coefficients de transfert en fonction des composés du vin (CO2, éthanol, sucrose, consommateurs d’oxygène) et des conditions opératoires (type de diffuseur, température, rapport entre hauteur et diamètre du contenant de liquide). Les résultats montrent que lors de la micro-oxygénation, le dioxyde de carbone dissous et le sucrose ont une incidence négative sur le transfert alors que la présence d’éthanol améliore le transfert. En ce qui concerne les conditions opératoires, l’augmentation de débit de gaz et l’augmentation de rapport entre la hauteur et le diamètre de la cuve de micro-oxygénation joue positivement sur le transfert d’oxygène La surface spécifique des bulles et le coefficient de transfert de matière ont pu être dissociés pour les vins. La nature tensio-active des composés du vin semble être un élément important sur le transfert de matière. Les connaissances acquises ont été appliquées à la micro-oxygénation au cours de deux étapes de l'élaboration des vins : la fermentation alcoolique avec la maitrise de l’apport d’oxygène et la simulation de la technique d’élevage en barrique par micro-oxygénation couplée à l’ajout de copeaux de bois. Une nouvelle approche concerne l'étude d'un contacteur membranaire qui permet le transfert d’oxygène par diffusion. / Micro-oxygenation of the wines, by the dispersion of oxygen bubbles, is a practice increasingly used in oenology. This technique is not always suitably controlled for lack of scientific knowledge on the parameters governing the transfer of oxygen. Research was focused on the study of transfer coefficients in function of wine components (CO2, ethanol, sucrose, consuming oxygen) and of operating conditions (type of diffuser, temperature, relationship between height and diameter of the container of liquid). The results show that during micro-oxygenation, the dissolved carbon dioxide and the sucrose have a negative incidence on the transfer whereas the presence of ethanol improves the transfer. As operating conditions are concerned, the increase in gas output and the increase in micro-oxygenation tank height/diameter ratio positively influence oxygen transfer. For wines, the specific surface of the bubbles and the mass transfer coefficient could be dissociated. The surfactant nature of wine components seems to be the most important factor in mass transfer. The knowledge so acquired was applied to micro-oxygenation during two stages of wine making: alcoholic fermentation with the oxygen yield control and the simulation of ageing technique in barrels coupled with the wood chips addition. A new approach relates to the study of a membrane contactor application allowing the oxygen transfer by diffusion.

L'objectif de cette thèse est de fournir des modèles et des outils de simulation pour décrire les échanges de masse entre les circuits de ventilation (galeries) et les milieux poreux des ouvrages souterrains d'enfouissement des déchets nucléaires. La modélisation prend en compte le couplage à l'interface poreux-galerie entre les écoulements liquide gaz compositionnels dans le milieu poreux constituant le stockage et les écoulements gazeux compositionnels dans le milieu galerie libre. / The objective of this thesis is to develop models and algorithms to simulate efficiently the mass exchanges occurring at the interface between the nuclear waste deep geological repositories and the ventilation excavated galleries. To model such physical processes, one needs to account in the porous medium for the flow of the liquid and gas phases including the vaporization of the water component in the gas phase and the dissolution of the gaseous components in the liquid phase. In the free flow region, a single phase gas free flow is considered assuming that the liquid phase is instantaneously vaporized at the interface. This gas free flow has to be compositional to account for the change of the relative humidity in the free flow region which has a strong feedback on the liquid flow rate at the interface.

The use of hydrophobic porous polymer membranes to vent unwanted gas bubbles from liquid streams is becoming increasingly more common in portable applications such as direct methanol fuel cells (DMFCs) and micro-fluidic cooling of electronic circuits. In order for these portable systems to keep up with the ever increasing demand of the mobile user, it is essential that auxiliary components, like gas-liquid separators (GLS), continue to decrease in weight and size. While there has been significant progress made in the field of membrane-based gas-liquid separation, the ability to miniaturize such devices has not been thoroughly addressed in the available literature. Thus, it was the purpose of this work to shed light on the scope of GLS miniaturization by examining how the amount porous membrane required to completely separate gas bubbles from a liquid stream varies with operating pressure. Two membrane characterization experiments were also employed to determine the permeability, k, and liquid entry pressure (LEP) of the membrane, which provided satisfying results. These parameters were then implemented into a mathematical model for predicting the theoretical membrane area required for a specified two-phase flow, and the results were compared to experimental values. It was shown that the drastically different surface properties of the wetted materials within the GLS device, namely polytetrafluoroethylene (PTFE) and acrylic, caused the actual membrane area requirement to be higher than the theoretical predictions by a constant amount. By analyzing the individual effects of gas and liquid flow, it was also shown that the membrane area requirement increased significantly when the liquid velocity exceeded an amount necessary to cause the flow regime to transition from wedging/slug flow to wavy/semi-annular flow.