Thesis (M.S.)--Ohio University, November, 2004. / Title from PDF t.p. Includes bibliographical references (p. 11-113)

ANP; PETROBRAS, FINEP / Escoamentos multifásicos estão presentes não somente em diversos processos da natureza, mas também são muito comuns em diversas atividades industriais, como na exploração, produção e transporte de petróleo e gás. Na produção de petróleo, a mistura multifásica de gás, petróleo e água é frequentemente encontrada fluindo através de colunas e risers de produção. Nos últimos anos muito progresso no desenvolvimento e aplicação de técnicas de medição em escoamentos multifásicos foi realizado cujo intuito é quantificar com exatidão, prever e/ou controlar o fluxo de misturas multifásicas. Em especial técnicas de imageamento do escoamento multifásico estão em foco atualmente. Sensores de malha de eletrodos (wire-mesh sensors) são dispositivos que produzem imagens da distribuição das fases na seção transversal de uma tubulação com alta resolução espacial e temporal. Em estudos anteriores a utilização desse sensor é explorada em diversas aplicações em escoamentos bifásicos (predominantemente do tipo gás-líquido). O princípio de funcionamento do sensor é baseado na medição de uma única propriedade elétrica (condutividade ou permissividade) da mistura multifásica. Portanto, o objetivo deste trabalho é a aplicação da técnica wire-mesh para visualização de escoamentos multifásicos em alta velocidade para condições de escoamentos diferentes daquelas utilizados até o momento, bem como prover a técnica com melhorias, adicionando a capacidade de operar em dupla modalidade (medição simultânea condutiva/capacitiva). Assim, novos algoritmos e rotinas de processamento de dados para a investigação de escoamentos gás-líquido e sólido-líquido (suspensão) foram desenvolvidos e testados. A fim de continuar com o aprimoramento da técnica xiii de medição, uma nova eletrônica capaz de medir simultaneamente a permissividade e condutividade através da medição (vetorial) de amplitude e fase é introduzido. Além disso, um algoritmo baseado em um modelo da permissividade elétrica complexa realiza a fusão dos dados de condutividade e permissividade gerados pela técnica desenvolvida. Assim, esta fusão permite obter distribuições individuais das frações de fase de misturas de óleo-água-gás. A principal contribuição deste trabalho no campo de medição e investigação de escoamentos multifásicos é, por conseguinte, o desenvolvimento e aplicação soluções em software e processamento de dados para extração de parâmetros do fluxo multifasico a partir de dados do sensor wire-mesh, bem como a melhoria no sistema de medição com adoção de medidas vetoriais. Desta forma, a gama de aplicação do sensor wire-mesh é ampliada, permitindo a investigação de escoamentos gás-líquido e gás-sólido, assim como escoamentos trifásicos gás-líquido-líquido através de visualização em alta velocidade da distribuição de fases em escoamentos. / Multiphase flows are present not only in nature but also are very common in industrial activities such as in exploration, production and transport of oil and gas. In oil production, the mixture of gas, oil and water is often found streaming through production columns and flow risers. A lot of progress has been made in recent years in the development and application of measurement techniques applied to multiphase flow measurement in order to accurately quantify, predict and control the flow of multiphase mixtures. Especially, high-speed imaging of multiphase flows has received much attention in recent years. Wire-mesh sensors are flow-imaging devices and allow the investigation of multiphase flows with high spatial and temporal resolution. In the past, such sensors have found widespread application in gas-liquid flows. Its operating principle is based on measurement of a single electrical property (conductivity or permittivity) of flowing mixture. The objective of this work is the application of the wire-mesh technique for high-speed multiphase flow imaging in different flow conditions as applied so far, as well as the further development of this technique by adding the capability of dual-modality (simultaneous conductive/capacitive) operation. Hence, novel routines and data processing algorithms for the investigation of two-phase flows of the type gas-liquid and solid-liquid (slurry) were developed and tested. As a step towards the further development of the wire-mesh sensor technique, a novel dual- modality electronics being able to simultaneously evaluate the conductivity and permittivity component of a fluid through vector measurements (amplitude and phase) is introduced. Further, a model-based algorithm to fuse the data of dual-modality wire xi mesh sensor is developed to obtain individual phase fraction distributions in gas-oil- water three-phase flows. Hence, this thesis’ main contribution to the field of flow measurement and investigation is the development and application of software solutions for extracting flow parameters from wire-mesh sensor data, as well as the improvement in the hardware of measuring electronics. As a result, the range of application of wire-mesh sensors is enhanced being capable to investigate two-phase gas-liquid and slurry flows as well as gas-liquid-liquid three-phase flow problems through high-speed flow imaging.

ANP; PETROBRAS, FINEP / Escoamentos multifásicos estão presentes não somente em diversos processos da natureza, mas também são muito comuns em diversas atividades industriais, como na exploração, produção e transporte de petróleo e gás. Na produção de petróleo, a mistura multifásica de gás, petróleo e água é frequentemente encontrada fluindo através de colunas e risers de produção. Nos últimos anos muito progresso no desenvolvimento e aplicação de técnicas de medição em escoamentos multifásicos foi realizado cujo intuito é quantificar com exatidão, prever e/ou controlar o fluxo de misturas multifásicas. Em especial técnicas de imageamento do escoamento multifásico estão em foco atualmente. Sensores de malha de eletrodos (wire-mesh sensors) são dispositivos que produzem imagens da distribuição das fases na seção transversal de uma tubulação com alta resolução espacial e temporal. Em estudos anteriores a utilização desse sensor é explorada em diversas aplicações em escoamentos bifásicos (predominantemente do tipo gás-líquido). O princípio de funcionamento do sensor é baseado na medição de uma única propriedade elétrica (condutividade ou permissividade) da mistura multifásica. Portanto, o objetivo deste trabalho é a aplicação da técnica wire-mesh para visualização de escoamentos multifásicos em alta velocidade para condições de escoamentos diferentes daquelas utilizados até o momento, bem como prover a técnica com melhorias, adicionando a capacidade de operar em dupla modalidade (medição simultânea condutiva/capacitiva). Assim, novos algoritmos e rotinas de processamento de dados para a investigação de escoamentos gás-líquido e sólido-líquido (suspensão) foram desenvolvidos e testados. A fim de continuar com o aprimoramento da técnica xiii de medição, uma nova eletrônica capaz de medir simultaneamente a permissividade e condutividade através da medição (vetorial) de amplitude e fase é introduzido. Além disso, um algoritmo baseado em um modelo da permissividade elétrica complexa realiza a fusão dos dados de condutividade e permissividade gerados pela técnica desenvolvida. Assim, esta fusão permite obter distribuições individuais das frações de fase de misturas de óleo-água-gás. A principal contribuição deste trabalho no campo de medição e investigação de escoamentos multifásicos é, por conseguinte, o desenvolvimento e aplicação soluções em software e processamento de dados para extração de parâmetros do fluxo multifasico a partir de dados do sensor wire-mesh, bem como a melhoria no sistema de medição com adoção de medidas vetoriais. Desta forma, a gama de aplicação do sensor wire-mesh é ampliada, permitindo a investigação de escoamentos gás-líquido e gás-sólido, assim como escoamentos trifásicos gás-líquido-líquido através de visualização em alta velocidade da distribuição de fases em escoamentos. / Multiphase flows are present not only in nature but also are very common in industrial activities such as in exploration, production and transport of oil and gas. In oil production, the mixture of gas, oil and water is often found streaming through production columns and flow risers. A lot of progress has been made in recent years in the development and application of measurement techniques applied to multiphase flow measurement in order to accurately quantify, predict and control the flow of multiphase mixtures. Especially, high-speed imaging of multiphase flows has received much attention in recent years. Wire-mesh sensors are flow-imaging devices and allow the investigation of multiphase flows with high spatial and temporal resolution. In the past, such sensors have found widespread application in gas-liquid flows. Its operating principle is based on measurement of a single electrical property (conductivity or permittivity) of flowing mixture. The objective of this work is the application of the wire-mesh technique for high-speed multiphase flow imaging in different flow conditions as applied so far, as well as the further development of this technique by adding the capability of dual-modality (simultaneous conductive/capacitive) operation. Hence, novel routines and data processing algorithms for the investigation of two-phase flows of the type gas-liquid and solid-liquid (slurry) were developed and tested. As a step towards the further development of the wire-mesh sensor technique, a novel dual- modality electronics being able to simultaneously evaluate the conductivity and permittivity component of a fluid through vector measurements (amplitude and phase) is introduced. Further, a model-based algorithm to fuse the data of dual-modality wire xi mesh sensor is developed to obtain individual phase fraction distributions in gas-oil- water three-phase flows. Hence, this thesis’ main contribution to the field of flow measurement and investigation is the development and application of software solutions for extracting flow parameters from wire-mesh sensor data, as well as the improvement in the hardware of measuring electronics. As a result, the range of application of wire-mesh sensors is enhanced being capable to investigate two-phase gas-liquid and slurry flows as well as gas-liquid-liquid three-phase flow problems through high-speed flow imaging.

This thesis describes the first application of ultra-fast magnetic resonance imaging (MRI) towards the characterisation of bubbly flow systems. The principle goal of this study is to provide a hydrodynamic characterisation of a model bubble column using drift-flux analysis by supplying experimental closure for those parameters which are considered difficult to measure by conventional means. The system studied consisted of a 31 mm diameter semi-batch bubble column, with 16.68 mM dysprosium chloride solution as the continuous phase. This dopant served the dual purpose of stabilising the system at higher voidages, and enabling the use of ultra-fast MRI by rendering the magnetic susceptibilities of the two phases equivalent. Spiral imaging was selected as the optimal MRI scan protocol for application to bubbly flow on the basis of its high temporal resolution, and robustness to fluid flow and shear. A velocimetric variant of this technique was developed, and demonstrated in application to unsteady, single-phase pipe flow up to a Reynolds number of 12,000. By employing a compressed sensing reconstruction, images were acquired at a rate of 188 fps. Images were then acquired of bubbly flow for the entire range of voidages for which bubbly flow was possible (up to 40.8%). Measurements of bubble size distribution and interfacial area were extracted from these data. Single component velocity fields were also acquired for the entire range of voidages examined. The terminal velocity of single bubbles in the present system was explored in detail with the goal of validating a bubble rise model for use in drift-flux analysis. In order to provide closure to the most sophisticated bubble rise models, a new experimental methodology for quantifying the 3D shape of rising single bubbles was described. When closed using shape information produced using this technique, the theory predicted bubble terminal velocities within 9% error for all bubble sizes examined. Drift-flux analysis was then used to provide a hydrodynamic model for the present system. Good predictions were produced for the voidage at all examined superficial gas velocities (within 5% error), however the transition of the system to slug flow was dramatically overpredicted. This is due to the stabilising influence of the paramagnetic dopant, and reflects that while drift-flux analysis is suitable for predicting liquid holdup in electrolyte stabilised systems, it does not provide an accurate representation of hydrodynamic stability. Finally, velocity encoded spiral imaging was applied to study the dynamics of single bubble wakes. Both freely rising bubbles and bubbles held static in a contraction were examined. Unstable transverse plane vortices were evident in the wake of the static bubble, which were seen to be coupled with both the path deviations and wake shedding of the bubble. These measurements demonstrate the great usefulness for spiral imaging in the study of transient multiphase flow phenomena.

Orientador: Luiz Felipe Mendes de Moura / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-07-21T14:04:09Z (GMT). No. of bitstreams: 1 Belo_FranciscoAntonio_D.pdf: 47396549 bytes, checksum: f9c5db83bcca1df5d676d8d6f0063095 (MD5) Previous issue date: 1995 / Resumo: Apresentam-se modelagem e métodos experimentais para validação da análise eletrônica aplicada à escoamentos multifásicos. Baseia-se no comportamento da amostra em relação ao campo eletromagnético e de sua identificação através de uma trandução eletrônica. Organiza-se os fundamentos da resposta da matéria com o campo eletromagnético e, a partir destas, os princípios das células transdutoras. A eletrônica de transdução consiste de uma técnica de processamento eletrônico analógico bem integrada a unidade sensora de modo a permitir a obtenção de resultados experimentais próximos dos valores calculados, até freqüências razoavelmente altas, comparadas às utilizadas em trabalhos similares. Uma técnica de guarda permite uma boa localização do campo de medidas da amostra. Foram desenvolvidos protótipos de laboratórios, propostos métodos de aferição e analisados as respostas simuladas e reais de diversos tipos de escoamento bifásico gás-líquido. Os resultados obtidos apontam para a viabilidade da utilização do método experimental proposto para a aplicação em um sistema de tomografia com processamento tipo paralelo / Abstract: Modeling and experimental method to validation of the electronic analyses by conduction and polarization applied to multiphase flow are presented. It is based on the behavior of the sample with electromagnetic waves and it identification by electronic transducer. An overview of answer of sample with the field is implemented, following the principie of the transducer cell. The electronic transducer consists in an analog electronic processing integrated to unit sensor in order to approximate the calculated and experimental data until high frequency, comparative with similar application. A guard technique permit a good localization of the sample. Laboratory prototype was developed, calibration method was proposed and simulated and real two-phase flows were analyzed. The obtained results show the capability of the proposed measurement system to be applied to the two-phase tomography with parallel processing / Doutorado / Termica e Fluidos / Doutor em Engenharia Mecânica

This work investigates the effects of long range hydrodynamic fibre-fibre interactions on the orientation state of a semi-dilute, rigid fibre suspension flowing through a linear contracting channel under laminar flow conditions. The effects of fibre-fibre interactions are modeled mathematically, the governing equations solved numerically and the predicted results compared with experimental observations. The theoretical model is based on the assumption that the orientation state of the suspension can be completely described by a probability distribution function and that fibre-fibre interactions are random in nature, thus giving rise to a diffusion-type process. The orientation distribution evolves spatially according to a Fokker-Plank type equation using closure equations for the rotary diffusion coefficient advanced by either (i) Folgar and Tucker (J. Reinforced Plast. Comp. 3 98–119 1984) or (ii) Koch (Phys. Fluids 7(8) 2086–2088 1995). Each of these two closure models for the rotary diffusion coefficient contains an unknown empirical constant that must be determined from experiments. These were fit to experimental data along the central streamline of the contraction as a function of fibre concentration. The diffusion coefficient was found to first increase with increasing suspension concentration up to a maximum, and then decrease with concentration above this point. This non-monotonic behavior was attributed to fibre flocculation, a mechanism not considered in the relationships for the rotary diffusion coefficient. The theoretical model is then extended to predict fibre orientation over the entire plane of the contraction and the two-way momentum coupling between the fluid and fibre phases were investigated numerically. The results show that the structure of the flow field within the contraction is significantly altered when the fibre phase is considered, demonstrating the non-negligible effect of the momentum exchange between the two phases. Comparison is made between the predicted orientation state of the suspension with experimental observations over the contraction plane. Good agreement was found between the model predictions and the experimental observations except in a small region near the solid boundaries. These near wall discrepancies were attributed to an inability to correctly handle the wall boundary conditions in the fibre orientation model. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

Orientador: Milton Mori / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-18T19:12:31Z (GMT). No. of bitstreams: 1 PrietoJimenez_Natalia_M.pdf: 6938239 bytes, checksum: 6c44d3053179a676042ac55971eeb06b (MD5) Previous issue date: 2011 / Resumo: Craqueamento Catalítico Fluidizado (FCC) é um processo amplamente utilizado para converter frações de hidrocarbonetos de óleos brutos de petróleo com elevado ponto de ebulição, a produtos mais valiosos tais como gasolina e gases olefínicos (alcenos). Durante as reações de craqueamento, o catalisador é desativado rapidamente devido à deposição de coque na sua superfície. Em unidades industriais de FCC, o catalisador desativado é continuamente regenerado utilizando um regenerador, conectado ao reator riser. Além da regeneração do catalisador (combustão de coque pelo contato com o ar), o regenerador FCC fornece também a energia necessária para as reações de craqueamento endotérmicas. O objetivo deste trabalho de pesquisa é simular a combustão de coque em um regenerador tridimensional, analisado variáveis de saída como concentração de carbono, temperatura, velocidade axial e radial das fases sólida e gasosa, e fração volumétrica de sólidos, mediante a técnica de Fluidodinâmica Computacional (CFD). Para isto, são utilizadas duas configurações de regenerador com dimensões e condições de contorno tomadas da literatura. Para a modelagem matemática e numérica utilizaram-se os softwares comerciais ANSYS-CFX V11 e FLUENT V12, junto com sub-rotinas desenvolvidas durante a pesquisa. Foram comparados sistemas de reação homogênea e heterogênea utilizando o modelo cinético Finite-Rate laminar, no qual as taxas de reação são determinadas pelas expressões cinéticas de Arrhenius. Do desenvolvimento das simulações obtiveram-se resultados satisfatórios que serão úteis no entendimento do complexo processo da regeneração de catalisadores para processos de FCC / Abstract: Fluidized Catalytic Cracking (FCC) is a widely used process to convert hydrocarbon fractions of crude petroleum oils with high boiling point to more valuable products such as gasoline and olefin gases (alkenes). During the cracking reactions, the catalyst is quickly deactivated due to coke deposition on its surface. In FCC industrial units, deactivated catalyst is continuously regenerated using a regenerator, connected to the riser reactor. In addition to catalyst regeneration (coke combustion by contact with air), FCC regenerator also provides the necessary energy for endothermic cracking reactions. The aim of this research was to simulate the coke combustion in a three-dimensional regenerator, analyzing output variables as coke concentration, temperature, axial and radial velocity of solid and gaseous phases, and solid volume fraction through the technique of Computational Fluid Dynamics (CFD). For this purpose two configurations of regenerator were used with dimensions and boundary conditions taken from the literature. For mathematical and numerical modeling, the commercial software ANSYS-CFX V11 and FLUENT V12 were used, with subroutines developed during the research. Homogeneous and heterogeneous reaction systems were compared using the laminar Finite-Rate kinetic model, in which the reaction rates are determined by Arrhenius kinetic expressions. The simulation of this system produced satisfactory results that will be useful in understanding the complex process of catalyst regeneration for FCC processes / Mestrado / Desenvolvimento de Processos Químicos / Mestre em Engenharia Química

No description available.

No description available.

Multiphase flow in porous media is important in a wide range of industrial and environmental processes. It is well-known that the fluids’ relative affinity to the porous media (i.e., wettability) is a crucial factor controlling multiphase flow in porous media. Despite having a good understanding of multiphase flow in porous media under uniform wettability conditions, our knowledge of how fluids flow in mixed-wet porous media is more limited. Mixed-wet porous media (i.e., porous media with spatially heterogeneous wettability) is prevalent in nature, from groundwater aquifers to oil-bearing rocks. This Thesis aims to better understand the complexities of multiphase flow in mixed-wet porous media. The study begins with investigating fluid-fluid displacement in mixed-wet microfluidic flow cells. We performed experiments over a range of capillary numbers and mixed-wettability conditions, and our results show that the fluid-fluid interface in mixed-wet pores resembles an S shaped saddle with very low capillary pressure. In the next step, we derive analytical expressions for fluid-fluid interface evolution through mixed-wet pore throats. These analytical expressions are incorporated into a dynamic pore network model, which enables us to develop a numerical framework capable of simulating fluid-fluid displacement in mixed-wet porous media. Next, we leverage our model to simulate multiphase flow in simple mixed-wet porous micro-models consisting of distinct water-wet and oil-wet regions whose fractions are systematically varied to yield a variety of displacement patterns over a wide range of capillary numbers. Our simulations reveal that mixed-wettability impacts are most prominent at low capillary numbers, and it depends on the complex interplay between the wettability fraction and the intrinsic contact angle of the water-wet regions. We also investigate the dynamics of multiphase flow in mixed-wet porous media under quasi-static conditions and discover that it exhibits self-organized criticality (SOC). Finally, we determine the correlation between spatial and temporal aspects of this dynamical system. / Thesis / Doctor of Science (PhD)