Made available in DSpace on 2014-10-09T12:32:06Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:57:55Z (GMT). No. of bitstreams: 1 02297.pdf: 1929315 bytes, checksum: 1f3c8c5cb4048eb63b32ec185d9f1b49 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2015-05-08T14:59:53Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 1176098 bytes, checksum: f4af6c1315fb2c04cc38083433e1f89d (MD5) Previous issue date: 2003-02-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In this work we analyze a heat exchanger type cylindrical evaporator usually employed on the domestic refrigerators. The internal flow occurs with a fluid in phase change process. Equations representing the problem under study are the equations of conservation of mass momentum and energy. The tool used to solve these differential equations is the generalized integral transform technique (GITT) produces hybrid solutions for both the hydrodynamic field as for the thermal field. The used model for the evaporator considers it as straight duct and with stratified flow where both phase liquid and vapor can flow with different too. To avoid mathematical complexity of modeling each phase separately is introduced the void fraction concept. The thermal and hydrodynamic fields are studied on the dimensional form and combine as a coupled problem. The thermal field is plotted against enthalpy. / Neste trabalho analisamos um trocador de calor do tipo evaporador cilíndrico, largamente utilizado em refrigeradores domésticos. O escoamento interno ocorre com um fluido em mudança de fase. As equações representativas do problema em estudo são as equações da conservação da massa, da quantidade de movimento e da energia. A ferramenta utilizada para solucionar estas equações diferenciais é a Técnica da Transformada Integral Generalizada (GITT), que produz soluções híbridas tanto para o campo hidrodinâmico como para o campo térmico. O modelo considera que este evaporador é um tubo reto, com escoamento estratificado, onde ambas as fases, líquida e gasosa, podem escoar com velocidades diferentes. Para evitar a complexidade de se modelar cada fase separadamente é introduzido o conceito de fração de vazio. Os campos de velocidade e térmico são estudados na forma adimensional e formam um problema acoplado. O campo térmico é representado em função da entalpia.

Orientador: Luiz Roberto Carrocci / Banca: Maurício Araújo Zanardi / Banca: Marco Aurélio Ferreira / Resumo: O estudo do escoamento bifásico gás-sólido está incluído no assunto referido ao escoamento multifásico. Este tipo de escoamento multifásico é encontrado no transporte pneumático, combustão do carvão, reatores de leito fluidizado e ciclones. O escoamento bifásico gás-sólido é extremamente complicado devido ao grande número de variáveis envolvidas, a interação entre as fases, e a complexa dinâmica que desenvolve durante o processo. Uma das áreas menos entendidas referente ao estudo do escoamento multifásico é a transferência da quantidade de movimento e o acoplamento entre as fases. A proposta desta dissertação é pesquisar aspectos da transferência da quantidade de movimento em um escoamento bifásico gás-sólido vertical descendente sobre a base das equações unidimensionais desenvolvidas para o referido escoamento. Os efeitos dinâmicos entre as fases são analisados considerando um acoplamento unidirecional tendo em conta termos tais como a força de arraste sobre as partículas, a força da gravidade e o atrito partícula-parede. Para a resolução do modelo teórico foi empregado o método Runge-Kutta-Merson. O modelo teórico permite calcular e avaliar a influência das variáveis do escoamento sobre o perfil axial da velocidade média das partículas e também possibilita a determinação de outras variáveis tais como a fração volumétrica de sólidos. Adicionalmente é projetado um sistema de instrumentação para medir a velocidade média das partículas através da medição do tempo médio de trânsito das partículas. Resultado da pesquisa demonstra o complexo comportamento e as dificuldades encontradas no desenvolvimento da instrumentação para esta classe de escoamento. / Abstract: The study of gas-solid two-phase flow is included in a more general subject named as multiphase flow. This kind of multiphase flow is encountered in the pneumatic conveying, combustion of pulverized coal, fluidized bed reactor and cyclones. The gas-solid two-phase flow is extremely complicated because of the large number of variables involved, the interaction between the phases, and complex dynamical developments occurring in the process. One of the least understood areas of multiphase flows is the momentum transfer or the phase coupling. The purpose of this dissertation is to research aspects of momentum exchange on a vertical downward gassolid flow on the basis of one-dimensional equations developed for gas-solid twophase flow. The dynamic effects between the two phases are considered by one way coupling taking into account terms such as the drag force on the particles, gravity and the particle-wall frictions. For the solution of theoretical model the Runge-Kutta- Merson method was employed. The theoretical model allows to calculate and to evaluate the influence of the flow variables on the axial profile for the average velocity of particles and also enables the determination of other variables such as the solid hold-up. Also it is designed an experimental system to measure the average velocity of particles by measuring the average time of transit of them. The results show the complex behavior and the difficulties in developing instrumentation for this class of flow. / Mestre

Made available in DSpace on 2014-06-11T19:30:23Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-09-16Bitstream added on 2014-06-13T20:20:52Z : No. of bitstreams: 1 romeroluna_cm_me_guara.pdf: 1053862 bytes, checksum: 6b390f03c3acc981055903699c40d29a (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O estudo do escoamento bifásico gás-sólido está incluído no assunto referido ao escoamento multifásico. Este tipo de escoamento multifásico é encontrado no transporte pneumático, combustão do carvão, reatores de leito fluidizado e ciclones. O escoamento bifásico gás-sólido é extremamente complicado devido ao grande número de variáveis envolvidas, a interação entre as fases, e a complexa dinâmica que desenvolve durante o processo. Uma das áreas menos entendidas referente ao estudo do escoamento multifásico é a transferência da quantidade de movimento e o acoplamento entre as fases. A proposta desta dissertação é pesquisar aspectos da transferência da quantidade de movimento em um escoamento bifásico gás-sólido vertical descendente sobre a base das equações unidimensionais desenvolvidas para o referido escoamento. Os efeitos dinâmicos entre as fases são analisados considerando um acoplamento unidirecional tendo em conta termos tais como a força de arraste sobre as partículas, a força da gravidade e o atrito partícula-parede. Para a resolução do modelo teórico foi empregado o método Runge-Kutta-Merson. O modelo teórico permite calcular e avaliar a influência das variáveis do escoamento sobre o perfil axial da velocidade média das partículas e também possibilita a determinação de outras variáveis tais como a fração volumétrica de sólidos. Adicionalmente é projetado um sistema de instrumentação para medir a velocidade média das partículas através da medição do tempo médio de trânsito das partículas. Resultado da pesquisa demonstra o complexo comportamento e as dificuldades encontradas no desenvolvimento da instrumentação para esta classe de escoamento. / The study of gas-solid two-phase flow is included in a more general subject named as multiphase flow. This kind of multiphase flow is encountered in the pneumatic conveying, combustion of pulverized coal, fluidized bed reactor and cyclones. The gas-solid two-phase flow is extremely complicated because of the large number of variables involved, the interaction between the phases, and complex dynamical developments occurring in the process. One of the least understood areas of multiphase flows is the momentum transfer or the phase coupling. The purpose of this dissertation is to research aspects of momentum exchange on a vertical downward gassolid flow on the basis of one-dimensional equations developed for gas-solid twophase flow. The dynamic effects between the two phases are considered by one way coupling taking into account terms such as the drag force on the particles, gravity and the particle-wall frictions. For the solution of theoretical model the Runge-Kutta- Merson method was employed. The theoretical model allows to calculate and to evaluate the influence of the flow variables on the axial profile for the average velocity of particles and also enables the determination of other variables such as the solid hold-up. Also it is designed an experimental system to measure the average velocity of particles by measuring the average time of transit of them. The results show the complex behavior and the difficulties in developing instrumentation for this class of flow.

Made available in DSpace on 2014-10-09T12:32:06Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:57:55Z (GMT). No. of bitstreams: 1 02297.pdf: 1929315 bytes, checksum: 1f3c8c5cb4048eb63b32ec185d9f1b49 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Counter current chromatography (CCC) is a form of liquid liquid chromatography, which the Brunel Institute for Bioengineering (BIB) team have developed to process scale. In this thesis, its application has been successfully extended to the rapid, scalable purification of monoclonal antibodies (mAb) from mammalian cell culture, using aqueous two-phase systems (ATPS) of inorganic salts and polymer. A polyethylene glycol (PEG) and sodium citrate system was found to be the most appropriate by robotic phase system selection. The search for an economical alternative to protein A HPLC is a substantial bioprocessing concern; in this work CCC has been investigated. Initial studies showed that unpredictably, despite separation from impurities being achieved, some loss in the IgG‘s ability to bind to Protein A was seen, as confirmed by Protein A BiaCore analysis. CCC machines were seen to adversely affect IgG functionality. This led to a systematic investigation of the effect of CCC phase mixing on IgG functionality in a number of different CCC instruments, allowing direct comparisons of modes of CCC (hydrodynamic and hydrostatic CCC) and their associated mixing (wave-like and cascade, respectively). The varying g forces produced within the CCC column were determined using a recently developed model to calculate g force range. The effect of interfacial tension was also studied using a custom built 'g' shaker. The optimum CCC mode was identified to be the non synchronous CCC, operated in a hydrodynamic mode but allowing bobbin to rotor speed (Pr ratio) to be controlled independently. In a normal synchronous J type centrifuge a Pr of 1 is fixed, this is where the bobbin and rotor speed are identical I.e. one bobbin rotation (where mixing occurs) to one rotor revolution (where settling occurs). Constraints were seen with this 1:1 ratio and the separation of mAb using ATPS. This work has shown with the use of the non synchronous CCC at a Pr of 0.33, mixing is reduced and rotor rotations increased. Consequently the associated g force range is decreased. Furthermore, by the extension of settling time, the clear separation of the mAb from impurities has been achieved with retention of biological activity. This thesis demonstrates the importance of settling time for ATPS in phase separation and documents the fundamental requirements for the successful separation of biologics. Purified non synchronous CCC samples have additionally undergone rigorous quality control testing at Lonza Biologics by their purification scientists. This work has ultimately showed that with optimisation, the non synchronous CCC can be used to produce biological samples that are of industry standard.

Une turbine diphasique est utilisée pour remplacer le détendeur classique des systèmes de réfrigération. Dans la turbine, une tuyère transforme l'enthalpie de l'écoulement en énergie cinétique. Remplacer la détente isenthalpique classique par une détente isentropique augmente le coefficient de performance d'un système de réfrigération d'une valeur qui peut aller jusqu'à 20 %, pour la même consommation électrique du compresseur. Pendant cette transformation, la pression statique de l'écoulement diminue et un changement de phase se produit au col de la tuyère. La détente d'un écoulement diphasique est étudiée analytiquement et simulée avec le logiciel de CFD Fluent 13. Un modèle d'évaporation adapté à la détente diphasique est ajouté à l'algorithme de dynamique de fluide dans Fluent 13, afin de créer et simuler le changement de phase à l'intérieur de la tuyère. Le modèle d'évaporation est basé sur la théorie de la nucléation et sur des résultats expérimentaux. Le modèle calcule le taux de nucléation hétérogène initiée par les cavités de la paroi intérieur de la tuyère, et le taux de nucléation hétérogène initiée par la présence de bulles de vapeur au cœur de l'écoulement. Outre les tuyères, la roue de la turbine est aussi conçue. La roue récupère l'énergie cinétique d'un écoulement diphasique et la transforme en un couple de moment. La géométrie des différents éléments de la roue est définie afin d'assurer l'intégrité mécanique et un bon rendement énergétique. La conception de la roue prend en considération le comportement de l'écoulement en contact avec les paliers de la roue, la perte de puissance due aux frottements aérauliques, ainsi que de nombreux autres facteurs. Fluent 13 est utilisé pour simuler l'écoulement diphasique à l'intérieur des augets de la roue, ainsi que pour calculer les pertes dues aux frottements aérauliques. Le rendement calculé de la turbine est vérifié avec des tests d'une turbine diphasique dans un groupe refroidisseur d'eau ayant une puissance de réfrigération de 700 kW. / A two-phase turbine used to replace the usual expander in a refrigeration system needs a nozzle/expander to transform the flow enthalpy into kinetic energy. Replacing the isenthalpic expansion by the isentropic one, increases the coefficient of performance of refrigeration system up to 20% for the same compressor input power. During this transformation, the static pressure of the flow decreases and a phase change occurs at the nozzle throat. The expanding and flashing flow in the convergent and divergent parts of a nozzle is analytically studied and then simulated using the CFD software Fluent 13. A separate evaporation model is added to the fluid dynamics algorithms in Fluent 13 in order to create the phase change inside the nozzle. The evaporation model is based on the classical theory of nucleation and on experimental results: it calculates the heterogeneous nucleation initiated by the wall cavities and the heterogeneous nucleation initiated by the presence of vapor bubbles in the flow. The turbine is composed of the designed nozzles and a rotor that recovers the kinetic energy of the two-phase flow and transforms it into torque. The geometry of the rotor components is designed to provide mechanical integrity and high efficiency. The design takes into consideration the flow behavior inside the rotor, the power loss due to drag force, and many other factors. Fluent 13 is used to study the flow inside the rotor buckets and to estimate the power loss due to drag force. The turbine calculated efficiency is verified by testing a two-phase turbine in a water chiller having a refrigeration capacity of 700 kW.

Master of Science / Department of Mechanical Engineering / Bruce Babin / Recent world events are motivating the United States Government to invest in the development of Directed Energy Weapons (DEW). One defense contractor developing the technology, Raytheon Missile Systems Company, is addressing the cooling requirements. To this end, Raytheon has proposed some two-phase (liquid and vapor) heat transfer devices capable of dispersing the high energy densities associated with DEW. The Kansas State University Mechanical and Nuclear Engineering Department has been contracted to characterize the performance of the devices using ammonia as the working fluid. To this end, an Ammonia Test Chamber was reconfigured to perform the experiments. The chamber is now configured to deliver liquid ammonia at saturation pressures ranging from 45 to 115 psia, a sub-cooled liquid temperature of -25oC, and mass flow rates ranging from 0.01 to 0.03 kg/s. The Ammonia Test Chamber can absorb heat loads of up to 5000 W. Measurements of the Critical Heat Flux (CHF) of the device ranged from 173 W/cm2 to 488 W/cm2. This data agrees characteristically with published correlations of CHF values, however the correlations predict lower magnitudes.

No description available.

Master of Science / Department of Mechanical and Nuclear Engineering / B. Terry Beck / Mohammad H. Hosni / Cavitation is the formation of vapor phase from the liquid phase by reduction in its absolute pressure below the saturation pressure. Unlike boiling, where the temperature of the liquid is increased to cause vaporization, the reduction in the pressure alone can cause the liquid to turn into vapor. Cavitation is undesirable in many engineering applications as it is associated with reduction in efficiency and is known to cause damage to pump and propeller components. However, the endothermic nature of cavitation could be utilized to create a region of low temperature that could be utilized to develop a new refrigeration cycle. The work presented in this thesis is part of ongoing research into the potential cooling capacity of cavitation phenomena, where the cavitation in a converging-diverging nozzle is being investigated. Due to the constricting nature of the throat of the converging-diverging nozzle, the liquid velocity at the throat is increased, obeying the continuity law. With an increase in velocity, a reduction in absolute pressure is accompanied at the throat of the nozzle according to the Bernoulli’s principle. The local absolute pressure at the throat can go lower than the saturation vapor pressure, thereby causing the fluid to cavitate. The effect of water temperature on the flowrates, the onset of cavitation within the nozzle, and the resulting length of the cavitation region within the nozzle are the subject of this thesis. Experimental results and analysis are presented which also show that near the onset of cavitation, the flowrate can go beyond the choked flowrate, causing the local pressure in the throat to go well below zero for an extended amount of time in the metastable state, before nucleating (cavitating) into a stable state. Flow visualization using a high speed digital camera under different operating conditions was aimed at investigating the region of cavitation onset, which appears to be associated with boundary layer separation just downstream of the nozzle throat. In order to delay the boundary layer separation point in the downstream section of the nozzle, the diffuser region of the nozzle was modified to enable two flow paths, where one path would suck the flow near the inner walls of the nozzle and the other would allow the bulk of the flow to pass through. This was achieved with the use of inserts. Various inserts were tested in an attempt to capture the effect of inserts on the cavitation phenomena. Their effect on the flowrates, length of two phase region, and cavitation onset are presented in this thesis.