A microfluídica juntamente com a intensificação de processos são duas áreas de pesquisa interessadas no estudo e desenvolvimento de processos em escala micrométrica capazes de manipular diminutas quantidades de reagentes. Para tanto, estes devem contar com dispositivos de pequena escala de tamanho e ao mesmo tempo serem tão confiáveis e eficientes quanto os de escala industrial. Uma das operações unitárias envolvidas nesses processos é a agitação. Em função da ordem de grandeza dos equipamentos e dos materiais em que são fabricados, grandes diferenciais de pressão não podem ser aplicados nos mesmos e como conseqüência no interior dos micromisturadores, como são conhecidos tais equipamentos, o escoamento se dá em regime laminar, sob está condição o processo de mistura é controlado pela difusão entre os componentes. Uma maneira de superar esta dificuldade é gerar no interior do micromisturador o aparecimento de um escoamento caótico. Para tal, podem-se utilizar fontes de energia externa (micromisturadores ativos) ou a própria energia do escoamento (micromisturadores passivos) através da construção de geometrias especiais. O desenvolvimento em laboratório destes equipamentos demanda tempo e geralmente é oneroso. A principal alternativa para este trabalho é a dinâmica dos fluidos computacional (CFD), ferramenta aplicada no presente estudo para analisar três geometrias diferentes propostas e analisadas experimentalmente no trabalho de Cunha (2007). Para caracterizar o funcionamento dos mesmos foram testadas quatro vazões distintas, com as quais foi possível levantar os perfis de pressão, velocidade e fração mássica de dois componentes que eram misturados. Com o intuito de demonstrar a eficiência dos equipamentos dois parâmetros foram analisados: o avanço da qualidade da mistura e a perda de carga para as diferentes condições operacionais. Apesar da limitação da malha e de não ter-se obtido resultados independentes da malha, foi possível se fazer uma comparação entre as três geometrias e identificouse que os micromisturadores M2 e M3 são os que apresentam o melhor desempenho para a faixa de vazão simulada (120 < Re < 1200). / Microfluidics and process intensification are two research areas interested in the study and development of new micrometric-scale devices capable of manipulating and processing small quantities of reagents. These processes have to deal with small scale equipment and at the same time be as reliable and efficient as the large-scale one. Because of the scale of this equipment and the material it is made of, large pressure differential is not possible, as a consequence in the interior of the micromixers, as they are known; a laminar flow develops, under those circumstances the mixing process is controlled by the diffusion mechanism between the two components. One way to suppress this deficiency is to generate a chaotic flow on the micromixer, which can be done by using external energy (active micromixer) or its own flow energy (passive micromixer) through special geometry construction. The experimental development of such microdevices demands time and, generally, is very expensive. The main alternative for this activity is the use of computational fluid dynamics; this tool was employed on this work with the aim of studying three geometries proposed by Cunha (2007). To characterize their working process, four different volumetric flows were simulated and analyzed the pressure, velocity and mass fraction profiles. Two parameters were calculated in order to characterize their efficiency: the mixture quality along the micromixers cross sections and the pressure drop for different operational conditions. Although we have mesh size limitations and a mesh independent results were not obtained it was possible to compare the three micromixers geometries and it was found out that both M2 and M3 micromixers had the best performance under operational conditions tested (120 < Re < 1200).

A microfluídica juntamente com a intensificação de processos são duas áreas de pesquisa interessadas no estudo e desenvolvimento de processos em escala micrométrica capazes de manipular diminutas quantidades de reagentes. Para tanto, estes devem contar com dispositivos de pequena escala de tamanho e ao mesmo tempo serem tão confiáveis e eficientes quanto os de escala industrial. Uma das operações unitárias envolvidas nesses processos é a agitação. Em função da ordem de grandeza dos equipamentos e dos materiais em que são fabricados, grandes diferenciais de pressão não podem ser aplicados nos mesmos e como conseqüência no interior dos micromisturadores, como são conhecidos tais equipamentos, o escoamento se dá em regime laminar, sob está condição o processo de mistura é controlado pela difusão entre os componentes. Uma maneira de superar esta dificuldade é gerar no interior do micromisturador o aparecimento de um escoamento caótico. Para tal, podem-se utilizar fontes de energia externa (micromisturadores ativos) ou a própria energia do escoamento (micromisturadores passivos) através da construção de geometrias especiais. O desenvolvimento em laboratório destes equipamentos demanda tempo e geralmente é oneroso. A principal alternativa para este trabalho é a dinâmica dos fluidos computacional (CFD), ferramenta aplicada no presente estudo para analisar três geometrias diferentes propostas e analisadas experimentalmente no trabalho de Cunha (2007). Para caracterizar o funcionamento dos mesmos foram testadas quatro vazões distintas, com as quais foi possível levantar os perfis de pressão, velocidade e fração mássica de dois componentes que eram misturados. Com o intuito de demonstrar a eficiência dos equipamentos dois parâmetros foram analisados: o avanço da qualidade da mistura e a perda de carga para as diferentes condições operacionais. Apesar da limitação da malha e de não ter-se obtido resultados independentes da malha, foi possível se fazer uma comparação entre as três geometrias e identificouse que os micromisturadores M2 e M3 são os que apresentam o melhor desempenho para a faixa de vazão simulada (120 < Re < 1200). / Microfluidics and process intensification are two research areas interested in the study and development of new micrometric-scale devices capable of manipulating and processing small quantities of reagents. These processes have to deal with small scale equipment and at the same time be as reliable and efficient as the large-scale one. Because of the scale of this equipment and the material it is made of, large pressure differential is not possible, as a consequence in the interior of the micromixers, as they are known; a laminar flow develops, under those circumstances the mixing process is controlled by the diffusion mechanism between the two components. One way to suppress this deficiency is to generate a chaotic flow on the micromixer, which can be done by using external energy (active micromixer) or its own flow energy (passive micromixer) through special geometry construction. The experimental development of such microdevices demands time and, generally, is very expensive. The main alternative for this activity is the use of computational fluid dynamics; this tool was employed on this work with the aim of studying three geometries proposed by Cunha (2007). To characterize their working process, four different volumetric flows were simulated and analyzed the pressure, velocity and mass fraction profiles. Two parameters were calculated in order to characterize their efficiency: the mixture quality along the micromixers cross sections and the pressure drop for different operational conditions. Although we have mesh size limitations and a mesh independent results were not obtained it was possible to compare the three micromixers geometries and it was found out that both M2 and M3 micromixers had the best performance under operational conditions tested (120 < Re < 1200).

The aim of this thesis is to introduce the reader into theory, which is needed to make an aerodynamic calculation of flue gas part of steam boiler. On the back of the knowledge, project documentation and other entry parameters calculate sectional losses for each component and design a ventilator, that is suitable for our requirements.

Turbine blade cooling techniques have been around for many years, and the addition of coolant into the turbine blade section will remain to be a viable cooling option for many years to come. Film cooling, which will be the main subject of this research, is a form of convection cooling where holes are placed through the surface of the metal components. With the addition of this film coolant into the main flow, an increased amount of total pressure loss will be found downstream. This is caused by the difference of flow momentum of the coolant and main flow when the two fluids are mixed. The test rig used for the upcoming research will be the NASA-designed E3 rig. E3, standing for Energy Efficient Engine, was established to develop technology for improving the energy efficiency of future commercial transport aircraft engines. These engines were designed to provide real-world, actual test configurations in order to produce more efficient turbine engines, mainly to be used for propulsion. Tests were not focused just on heat transfer as its use will be, but with all aspects of the engine's components, especially aero. The annular cascade with 3-dimensional blade profiles as well as high Reynolds numbers make this setup an accurate test bed in which actual turbine conditions can be compared to. The focus of this research is on the increased amount of total pressure loss seen downstream in an annular cascade with 3D blade profiles with the addition of inner endwall film cooling in a high-speed setting. Also, the rig setup of closed vs. open-loop and its effect on the inlet conditions as well as total pressure loss will be investigated.

Pumping is the most efficient transportation and placing method for concrete. Despite the immense progress in the field of concrete technology in the last years, so far there are still neither official regulations nor verified theoretical foundations to be used for the assessment and accurate prediction pumping behaviour of ordinary and high performance concretes. This thesis aims at purposefully investigating pumping of modern concretes and bridging the existing knowledge gap. The main achievement of the present research is the development and verification of a sitecompliant and scientifically based methodology for characterisation and prediction of fresh concrete pumping behaviour. The research focus is set on the importance of the forming lubricating layer (LL) during pumping. Within an extended experimental program, the properties of the LL are captured and quantified. They determine the reduction of friction at the pipe wallconcrete interface and thereby govern the concrete flow. It is proven that the composition and the rheological properties of the forming LL exert an enormous impact on pumping since most of the induced shear stress by pumping pressure is concentrated in this layer. In a further step, the flow pattern of concrete is analytically and numerically determined. The concrete exhibits various principal flow types which are already defined at low flow rates: plug flow in case of strainhardening cementbased composite (SHCC), partial concrete bulk shear in ordinary concretes and pronounced bulk shear for selfcompacting concrete (SCC). The results from the fullscale pumping campaign are confronted with the existing pressure performance nomogram on the determination of pumping parameters. The nomogram’s prediction capacity is extended and verified for highly flowable concretes by replacing the slump and flow table results with the viscosity parameter of the LL. Furthermore, the challenges during pumping of concrete, inter alia, priming of the pipeline, blockage formation and final cleaning, are exemplified, and recommendations for the practitioners are provided. Finally, the transfer of the developed scientifically based and ready to use methodology on site is strongly advocated as a part of the future in situ rheology monitoring concept towards envisaged full automation of concrete production and casting processes. / Das Pumpen stellt die effektivste Methode für das Fördern und Einbringen von Frischbeton auf der Baustelle dar. Trotz der in den letzten Jahren erreichten deutlichen Fortschritte auf betontechnologischem Gebiet existieren für die Beurteilung der Pumpbarkeit von Beton bisher weder offiziell gültige Vorschriften noch abgesicherte theoretische Grundlagen, die eine zielsichere Vorhersage des Pumpverhaltens von Normal- als auch Hochleistungsbetonen ermöglichen. Die vorliegende Arbeit schließt entsprechende Wissenslücken und befasst sich gezielt mit dem Pumpen moderner Betone. Grundlegenden Erkenntnisgewinn stellt die Entwicklung einer wissenschaftlich fundierten, baustellengerechten Prüfmethodik zur Charakterisierung und Vorhersage des Pumpverhaltens von Frischbeton dar. Der Untersuchungsfokus richtet sich auf die Wirkung der sich beim Pumpvorgang ausbildenden Gleitschicht. Ein umfangreiches Untersuchungsprogramm gestattet die Erfassung und Quantifizierung der Eigenschaften dieser Schicht. Sie bestimmen infolge deutlicher Reduzierung der Reibung an der Grenzfläche zwischen Rohrwandung und Beton die Betonströmung entscheidend. Bewiesen wird, dass Betonzusammensetzung und rheologische Eigenschaften der Gleitschicht maßgebende Auswirkungen auf den Pumpvorgang haben, da sich die pumpdruckinduzierte Scherspannung in dieser Schicht konzentriert. Weiterhin erfolgt sowohl eine analytische als auch numerische Charakterisierung der Betonströmung im Rohr. Nachgewiesen wird, dass sich beim Pumpvorgang betonspezifisch unterschiedliche Strömungsarten einstellen, die bereits bei niedrigen Durchflussmengen definiert sind: Pfropfenströmung in hochduktilen Betonen, partielle Scherung des Kernbetons in Normalbetonen und signifikante Scherung in selbstverdichtenden Betonen. Aus großtechnisch durchgeführten Pumpversuchen gewonnene Ergebnisse werden dem derzeit vorhandenen, verbesserungsbedürftigen Betondruck-Leistungs-Nomogramm zur Einstellung von Parametern an der Betonpumpe gegenübergestellt. Die Vorhersagekapazität des Nomogramms kann durch den Ersatz der Ausbreit- bzw. Setzfließmaßangaben mit Viskositätsangaben der Gleitschicht erweitert und verifiziert werden. Des Weiteren werden baustellenbezogene Herausforderungen im Gesamtprozess des Betonpumpvorgangs, u. a. Vorbereitung der Rohrleitung vor dem Pumpen, Auftreten von Stopfern und Endreinigung exemplarisch dargestellt sowie Empfehlungen für die Praktiker erarbeitet. Schließlich wird der Transfer der in dieser Arbeit entwickelten wissenschaftlich basierten und anwendungsbereiten Methodik als Teil des zukünftigen Konzeptes für die in-situ Rheologie-Überwachung hinsichtlich einer angestrebten vollständigen Automatisierung von Fertigungs- und Einbringprozessen von Beton mit Nachdruck empfohlen.

[pt] Experiências foram realizadas para se determinar coeficientes de transferência de calor e fatores de atrito para escoamento em dutos cujas seções transversais têm a forma de triângulos isósceles. Dois dutos foram usados; um tinha um ângulo de vértice igual a 120 graus e o outro 60 graus. As experiências foram realizadas utilizando-se trocadores de calor de dutos triangulares. Os fluidos foram ar e água. Coeficientes médios de transferência de calor foram determinados através da medida dis coeficientes globais de transferência de calor dos trocadores. No caso do duto de 120 graus, as paredes dos triângulos isósceles eram lisas. Foram estudados escoamentos laminares e turbulentos. Para o duto de 60 graus, duas paredes pinadas. A finalidade dos pinos foi aumentar a área de troca de calor. Nesse caso (60 graus) apenas escoamento turbulento foi estudado. Para os dutos com paredes lisas, foi possível se obter a dependência dos coeficientes de troca de calor dos dutos com o número de Prandtl. Para se atingir condições totalmente desenvolvidas, os trocadores de calor, tinham um comprimento de entrada de aproximadamente 35 diâmetros hidráulicos. As condições de contorno térmicas consistiram de temperatura uniforme nas paredes iguais dos dutos, sendo a terceira parede isolada. Os dutos triangulares dos trocadores de calor consistiram de duas paredes metálicas e uma parede de material menos condutor. Os resultados são apresentados sob formas adimensionais. Números de Nusselt e fatores de atrito como funções dos números de Reynolds. / [en] Experiments were performed to determine heat transfer coefficients and friction factors for flows in ducts whose cross sections have the shape of isosceles triangles. Two ducts were used; one with an apex angle equal to 120 degrees and the other 60 degrees. The experiments were performed by utilizing triangular duct heat exchangers. The fluids were air and water. Average heat transfer coefficients of the heat exchangers. In the case of the 120 degrees duct, the walls of the isosceles triangles were smooth. Laminar and turbulent flows were studied. For the 60 degrees duct, two situations were considered; one with smooth walls and the other with two pinned walls. The purpose of the pins was to increase the heat transfer area. In this case (60 degrees) only turbulent flow was studied. For the ducts with smooth walls, it was possible to obtain the dependence of the duct heat transfer coefficients with prandtl number. To attain the duct heat transfer coefficients with Prandtl number. To attain fully developed conditions, the heat exchangers had a starting length of approximately 35 hydraulic diameters. The thermal boundary conditions consisted of uniform temperature on the two equal walls of the duct, the third wall being insulated. The triangular ducts of the heat exchangers consisted of two metallic walls and of lesser conduction material. The results are presented in dimensionless forms. Nusselt numbers and friction factors as functions of Reynolds Numbers.

[pt] Este trabalho apresenta um método geral e prático, baseado em técnicas de convolução discreta, para avaliar o valor esperado e a variância dos índices de freqüência e duração (FeD) da perda de carga de um sistema de geração. O método proposto modela sem qualquer restrição unidades geradoras com estados operativos de capacidade reduzida simultaneamente com todos possíveis estados de carga. O valor esperado e a variância dos índices de freqüência e duração da perda de carga são calculados, tratando as taxas de transição entre estados de geração e os picos de carga previstos como variáveis aleatórias. Técnicas de agregação são utilizadas para modelar as incertezas das disponibilidades da capacidade de geração das unidades hidráulicas. Sob este aspecto, os índices de confiabilidade são também variáveis aleatórias. A determinação da expansão da capacidade de geração na presença de incertezas é a proposta sob um novo enfoque. Este método avalia limites de confiança ( ou percentis) não só para os índices de perda de carga, mas também para os índices de Freqüência e Duração da falha. Assim, a expansão da capacidade de geração é reutilizada utilizando os percentis dos índices de risco em vez de se utilizar apenas seus valores médios. O método FeD proposto é utilizado para avaliar o impacto das incertezas nos parâmetros dos geradores e da carga, em sistemas típicos da geração, incluindo o Sistema Teste da confiabilidade do IEEE e uma configuração planejada para 1991 do Sistema Sul-Sudeste Brasileiro. / [en] This work presents a practical and general method base on discrete convolution techniques for evaluating the expectation and variance of the frequency and duration (FeD) reliability indices, for a single area system. The proposed method models simultaneously and without any restriction, derated generating capacity generation units with all possible load levels. The expectation and variance of Frequency and duration reability indices are evaluated based on discrete convolution, treating the the generating unit transition rates and forecast peak loads as random variables. Clustering techniques are used to model the incertainties in the output capacities of hydraulic units. Under this interpretation, the reliability indices are also random variables. The generation capacity expansion problem under uncertainties, for a single-area system, is addressed from a new point of view. This method determines confidence limits (or percenties) not only for the loss of load indices but also for the frequency and duration failure indices. The generating capacity expansion is then calculated through risk indices percenties instead of the usual expected values. The proposed FeD method is then used for evaluating the impact of load and generating parameter uncertainties on typical systems including the IEEE Reliability Test System, and the Brazlian South/Southeastern Generating System.

Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2011. / Despite the extensive research work carried out on flow through short square-edged orifice plates over the last century (e.g. Johansen, 1930; Benedict, 1977; Alvi et al., 1978; Swamee, 2005; ESDU, 2007), gaps in the engineering data still exist for certain ranges of flow conditions and geometries. The majority of data available in the literature are for Newtonian fluids in the turbulent flow regime (ESDU, 2007). Insufficient data have been observed for the orifice with pipe diameter ratio, β = 0.2, in the laminar flow regime. There are no experimental data for β = 0.3 and 0.57. The objective of this thesis was to conduct wide-ranging experimental studies of the flow in orifice plates, which included those geometrical configurations, by measuring pressure loss coefficients and discharge coefficients across the orifice plates using both Newtonian fluids and non-Newtonian fluids in both laminar and turbulent flow regimes. The test work was conducted on the valve test rig at the Cape Peninsula University of Technology. Four classical circular short square-edged orifice plates having, β = 0.2, 0.3, 0.57 and 0.7, were tested. In addition, two generation 0 Von Koch orifice plates (Von Koch, 1904), with equivalent cross sectional area were also tested for β = 0.57. Water was used as Newtonian fluid to obtain turbulent regime data and also for calibration purposes to ensure measurement accuracy and carboxymethyl cellulose, bentonite and kaolin slurries were used at different concentrations to obtain laminar and transitional loss coefficient data. The hydraulic grade line method was used to evaluate pressure loss coefficients (Edwards et al., 1985), while the flange tap arrangement method was used to determine the discharge coefficients (ESDU, 2007). A tube viscometer with three different pipe diameters was used to obtain the rheological properties of the fluids. The results for each test are presented in the form of pressure loss coefficient (kor) and discharge coefficient (Cd) against pipe Reynolds number (Re)

[pt] Os coeficientes de transferência de calor e os dados de perda de carga foram determinados experimentalmente, para o escoamento turbulento, em dutos circulares providos internamente de anéis transversais. Os resultados foram obtidos tanto para a região de entrada como na região totalmente desenvolvida. Foram investigados os efeitos da altura do anel, do espaçamento entre os anéis e do número de Reynolds. Variou-se o número de Reynolds de 5.000 a 75.000, enquanto que a faixa de passo p/H foi de 4 a 15. Duas alturas do anel foram estudadas, a saber, 0,05 e 0,10 vezes o diâmetro interno do tubo. O fator de atrito para as geometrias periódicas mostrou ser sempre bem superior ao fator de atrito para o tubo liso, crescendo rapidamente com H/D. Para os tubos com anéis de pequena altura, o fator de atrito decresce com o aumento do passo, enquanto o oposto é observado para os tubos com anéis maiores, na faixa pesquisada. Para H/D = 0,05, o coeficiente de transferência de calor é máximo para valores de p/H em torno de 10 e para baixos números de Reynolds. Para H/D e 0,10, o maior coeficiente de transferência de calor medido foi para p/H = 10, que mostrou ser praticamente independente do número de Reynolds. Uma comparação de desempenho entre os tubos anelados e liso foi realizada sob dois tipos de restrições, a saber, a iguais vazões mássicas e iguais potências de bombeamento. Os tubos anelados mostraram um melhor desempenho em todos os casos pesquisados, exceto para H/D = 0,10 com Re > 60.000. / [en] Heat transfer coefficients and pressure drop data were determine experimentally for turbulent flow in circular ducts equipped with internal transverse ribs. Both fully developed and entrance region results were obtained. The effects of the rib height, rib spacing, and Reynolds number were investigated. The Reynolds number ranged from 5,000 to 75,000, whereas the pitch p/H was varied in the range 4 to 15. Two rib heights were investigated, namely, 0.05 e 0,10 times the tube inside diameter. The friction factor for the periodic geometric was found to be always much larger than the smooth tube friction factor, increasing rapidly with H/D. For the tubes with short ribs, the friction factor decreases with increasing pitch, but the opposite is true for the tall ribbed tubes in the range investigated. For H/D = 0.05, tha heat transfer coefficient is highest for values of p/H around 10 and low Reynolds number. For H/D = 0,10, the highest heat transfer coefficients measured were for p/H = 10, where it was found to be nearly independent of the Reynolds number. Performance comparisons between the ribbed and smooth tubes were made under two types of constraints, namely, equal mass flow rate and equal pump power. It was found that the ribbed tubes have higher heat transfer perFormance for all cases investigated, except for H/D = 0.10 with Re > 60,000.

[pt] O presente trabalho descreve os experimentos realizados para estudar os efeitos da adição de polímeros sobre os perfis de velocidade de um escoamento turbulento desenvolvido. O objetivo é estudar os mecanismos de redução de arraste observando os efeitos causados nos perfis de velocidade e intensidade de turbulência utilizando a velocimetria por imagem de partículas (PIV) na sua forma estereoscópica como técnica experimental para medição do campo completo de velocidade tri-dimensional. Para a realização dos experimentos foi especialmente projetada e construída uma seção de testes que permitisse a realização de medidas de queda de pressão, além da medição de velocidades utilizando a técnica óptica SPIV. Conseguiu-se uma redução no atrito da ordem de 50% antes da degradação do polímero. Foi possível mostrar que o efeito da redução de arraste pela adição de polímeros depende diretamente do número de Reynolds do escoamento. Para Reynolds baixo (< 10(3)) não foi observada redução na perda de carga. No campo médio de velocidades foi observado um alargamento da camada de transição para o escoamento com a adição de polímeros, gerando um deslocamento do perfil de velocidades na região logarítmica. / [en] The present work is an experimental study of the characteristics of a drag reduced turbulent pipe flow. The main goal of the study is to measure the differences in the mean velocity and turbulence profiles between the Newtonian flow and the drag reduced flow using the stereoscopic particle image velocimetry (SPIV). It has been designed and built a loop test to perform the experiments. The loop test should allow the measurement of the pressure drop and the velocity field with the SPIV. It has been achieved a drag reduction of 50% before the polymer degradation. It was shown that drag reduction strongly depends on the Reynolds number. For low Reynolds number (< 10(3)) there was no drag reduction. In the mean velocity field it has been seen that the buffer layer is thickened, with causes an upward shift of the logarithmic profile for the drag reduced flow.