In einem Verbundprojekt im Rahmen des Programms „Energie 2020+“ gefördert durch das BMBF koordiniert durch das HZDR arbeiteten 4 Universitäten, 2 Forschungszentren und ANSYS zusammen. Der vorliegende Bericht beschreibt die Arbeiten des HZDR, die im Zeitraum September 2009 bis Januar 2013 durchgeführt wurden. Das Vorhaben war auf die Entwicklung und Validierung von CFD-Modellen von unterkühltem Sieden bis zu Filmsieden gerichtet. Im Bericht werden die entwickelten und verwendeten Modelle dargestellt. Anhand der Nachanalyse von Experimenten wird auf die vorgeschlagene Kalibrierung der Modelle eingegangen. Wichtig ist hierbei eine genauere Beschreibung der Zwischenphasengrenzfläche, die durch Kopplung des Wandsiedemodells mit einem Populationsmodell erreicht werden kann. Anhand der Analyse von Bündelexperimenten konnte gezeigt werden, dass die gemessenen querschnittsgemittelten Messwerte mit einem Satz im Rahmen der Modellunsicherheiten kalibrierter Modellparameter reproduziert werden kann. Für die Berechnung der Verteilungsmuster des Dampfgehaltes im Kanalquerschnitt muss die Modellierung der Turbulenz beachtet werden. Die experimentellen Arbeiten waren auf die Untersuchung eines Brennelementbündels gerichtet. An einer Versuchsanordnung zu einem Brennelementbündel werden die turbulente einphasige Geschwindigkeit (PIV), der mittlere Gasgehalt (Gamma-Densitometrie) sowie der zeitlich und räumlich aufgelöste Gasgehalt (Hochgeschwindigkeits-Röntgentomographie) gemessen. Letztere Methode wurde in Rossendorf entwickelt.

Le château fort imprègne profondément dès l'enfance l'imaginaire de nos contemporains. Le phénomène est massif et déjà ancien comme l'attestent les 418 images de châteaux forts proposées de 1882 à 1960, dans les publications pour la jeunesse, destinées à l'usage scolaire ou dans le cadre familial et qui servent de base à cette étude. L'activité éditoriale reflétant les choix de société, il s'agit alors de comprendre comment s'élaborent, durant l'enfance, la connaissance et le mythe du château fort au travers de ses diverses représentations iconiques, textuelles ou par le jouet-château.A partir de l'exploitation de ce vaste corpus, la thèse met en exergue les fondements de la connaissance du château fort qui prédominent en tous supports scolaires ou de loisirs : les références scientifiques aux travaux de Viollet-le-Duc, omniprésentes jusqu'en 1960. Ce souci d'appui sur les valeurs scientifiques reconnues nourrit les objectifs de la société de la fin du XIXe et du XXe s. qui, par ce choix déterminé, souhaite donner le meilleur à la formation de la jeunesse.Par ailleurs, l'étude des images en interaction avec l'écrit montre que les idées reçues, telle que l'huile bouillante et les oubliettes, font partie à la fois des connaissances acquises et des micro-mythes. Ces stéréotypes stimulant l'imaginaire de toutes générations, l'étude suivante analyse les émotions qui surgissent dans l'activité de réception des représentations mais aussi celles que l'enfant traduit dans le jeu symbolique. Pas à pas sont mises en évidence les peurs originelles que suscite le château fort chez l’enfant lecteur ou joueur : peur de la privation de liberté ou de lumière, peur de l'enfermement, en somme peur de la mort, cette inconnue. On rejoint là les mythes fondateurs de l'humanité.Grâce à l'analyse des manuels et des ouvrages de jeunesse, il apparaît que le château fort est aussi une construction politique instrumentalisée pour l'éducation morale et religieuse de la jeunesse, voire celle différenciée des garçons et des filles. Mais c'est le recours aux neurosciences qui permet de comprendre les processus neuronaux mis en jeu à propos du château fort, dans l'activité perceptive et sensible du jeune lecteur ou joueur mais aussi dans son activité motrice engageant la corporalité.Dans cette perspective, quel est le véritable enjeu de la restauration des châteaux forts ou même de la construction à l'identique du château du XIIIe siècle, Guédelon : préservation du passé ou plongée concrète dans l'imaginaire du château fort à l'échelle réelle ? / The fortified castle deeply pervades the imaginary world in the childhood of our contemporaries. The phenomenon is massive and already ancient, as the 418 pictures of the fortified castles proposed from 1882 to 1960 in youth publications dedicated to school or family use and which are the basis of this study can testify. Insofar as the editorial activity reflects social choices, it therefore deals with understanding how the knowledge and the myth of the fortified castle is building itself during childhood through its various iconic representations, textual or thanks to the toy-castle.Starting from the exploitation of this vast corpus, this thesis underlines the founding principles of the knowledge of the fortified castle which predominate in all supports, for education or for leisure : the scientific references to Viollet le Duc’s works, omnipresent until 1960. This will to be based on recognized scientific values feeds the goals of the society of the late 19th and 20th century, which, through this determined choice, wishes to give the best for the education of their youth.Moreover, the study of the pictures interacting with written expressions shows that the preconceived ideas, such as boiling oil or the dungeon, are part of acquired knowledge as much as of the micro-myth. These stereotypes stimulating the imaginary world of all generations, the following study gives an analysis of the emotions that emerge in the reception activity of the representations but also of the ones that the child translates in the symbolical game. Step by step, the original fears aroused by the fortified castle in the games of the reading or playing child are highlighted : fear of freedom or light deprivation, fear of imprisonment, in other words the fear of death, this unknown. Here we are in accordance with the founding myth of humanity.Thanks to the analysis of the school books and youth publications, it appears that the fortified castle is also a political construction used for moral and religious education, even the one that distinguishes boys from girls. But this is the resorting to neurosciences that enable to understand the neuronal process at stake as far as the fortified castle is concerned, in the young reader’s or player’s perceptive and sensitive activity, but also in his motor activity which implies his body awareness.With this purpose, what is really at stake in the restoration of the fortified castle or even in the identical building of the 13th century castle, Guédelon : preservation of the past, or a concrete immersion in the imaginary world of the fortified castle on a real scale ?

La compréhension des phénomènes se déroulant lors de l’impact d’une goutte sur une paroi chaude est essentielle à l’optimisation des systèmes de refroidissement par sprays. Lorsque la température de paroi est élevée, un film de vapeur se forme quasi-instantanément entre la goutte et la paroi chaude. Ce film modifie le comportement hydrodynamique des gouttes et réduit considérablement les échanges de chaleur et de masse par rapport à un impact mouillant. La modélisation de ces phénomènes est complexe en raison des nombreux couplages entre les transferts de chaleur et de masse et la dynamique d’impact de la goutte. Pour aborder ce sujet, des techniques de mesure optiques ont été développées spécifiquement. L’imagerie de fluorescence induite par plan laser à deux couleurs permet de caractériser la distribution de la température à l’intérieur des gouttes. Des images du champ de température, résolues à la fois spatialement et temporellement, sont rendues possible grâce à l’utilisation d’un nouveau couple de colorants fluorescents conservant une grande sensibilité à la température quand ils sont excités par un laser pulsé nanoseconde d’une énergie de plusieurs centaines de mJ. En parallèle, la thermographie infrarouge a été utilisée pour déterminer la température de la surface d’impact en saphir. Pour cela, cette dernière est recouverte d’une couche de quelques centaines de nanomètres de TiAlN, émissif dans l’IR alors que le saphir est transparent. Les images haute cadence sont analysées par un modèle d’inversion, prenant en compte la conduction thermique dans le saphir, afin d’estimer la densité de flux thermique au niveau de la surface d’impact. L’épaisseur du film de vapeur est également déduite de ces mesures sous l’hypothèse, justifiée a posteriori, d’une conduction thermique prépondérante dans le film de vapeur. Une étude de l’impact de gouttes d’eau est réalisée en faisant varier la vitesse d’impact et la température des gouttes avant impact, ainsi que la température de paroi. Dans la plupart des cas, la chaleur extraite à la paroi est comparable à celle transférée au liquide pour l’échauffer. Lorsque la température de paroi se rapproche et dépasse la température de Leidenfrost, les transferts de chaleur deviennent de plus en plus sensibles au nombre de Weber, et de moins en moins dépendant de la température de paroi. L’épaisseur du film de vapeur est affectée par des instabilités, dont les caractéristiques (longueur d’onde, amplitude) sont étudiées à partir des images IR. Finalement, un modèle 1D semi empirique est proposé pour décrire l’échauffement des gouttes et la croissance du film de vapeur. La pression exercée par la goutte sur le film de vapeur se dissipe très vite à l’impact, si bien que la croissance du film de vapeur est gouvernée par la conduction de la chaleur vers la goutte et non par la dynamique de l’impact / The understanding of phenomena occurring at the impact of a droplet onto a hot wall is crucial for the optimization of spray cooling systems. When the temperature of the wall is high, a vapor layer appears quasi-instantaneously between the droplet and le wall. This film of vapor modifies the hydrodynamic behavior of the droplet and highly reduce the heat and mass transfers in comparison with a wetting impact. Modelling these phenomena is complex because of the numerous coupling between the heat and mass transfers and the fluids dynamic. To get some insights into this phenomenon, optical diagnostic techniques have been developed. Two color planar laser induced fluorescence imaging allows characterizing the distribution of the temperature inside the droplet. Images of the temperature fields, resolved both spatially and temporally, are recorded thanks to the use of a couple of fluorescent dyes keeping a high temperature sensitivity even when they are excited by a nanosecond pulsed laser with and an energy of hundreds m J. In parallel, the infrared thermography is used to determine the temperature of the impinged surface made of sapphire. For that, this surface is coated with a thin film (about 300 nanometers) of TiAlN, highly emissive in the IR domain as opposed to the sapphire which is transparent in it. High frame rate image sequences are analyzed thanks to an analytical inversion model, taking into account the thermal conduction in the sapphire, in order to estimate the heat flux density at the impact surface. The thickness of the vapor layer was also deduced from this measurements thanks to the hypothesis of a dominant thermal conduction in the vapor layer. A study of water drop impact was performed with different impact speeds, wall temperatures and different drop injection temperatures. In most of the cases, the heat flux extracted from the wall in close to the flux transferred to the liquid phase of the droplet. When the wall temperature approaches or exceeds the Leidenfrost temperature, the transfers become more sensitive to the Weber number and less sensitive to the wall temperature. The vapor layer thickness is affected by instabilities whose caracteristics (wavelengths, amplitude) were investigated from the IR images. Eventually, a 1-Dsemi-empirical model is given for describing the heating of the liquid part of the droplet and the growth of vapor layer. The effect of the pressure exerted by the droplet onto the vapor film rapidly decreases during the impact process, so that the growth of the vapor film is only driven by the heat transferred by conduction to the droplet and not by dynamical parameters such as the impact velocity

Afin d’optimiser la taille et le coût des évaporateurs basse pression utilisés dans les systèmes de climatisation à sorption, une bonne connaissance des phénomènes de vaporisation du fluide frigorigène tels qu’ils pourraient se produire dans ces évaporateurs est nécessaire. Cependant très peu d’études portent sur ce sujet et il y a un sérieux manque de données concernant les phénomènes de vaporisation (ébullition et évaporation) qui pourraient se produire dans des évaporateurs compacts basse pression. Le but de cette étude est donc d’aller plus loin dans la compréhension de ces phénomènes aussi bien d’un point de vue très fondamental que d’un point de vue applicatif. Dans cette optique, deux bancs d’essais ont été réalisés. Le premier banc d’essais permet d’étudier le comportement de l’eau dans une configuration d’ébullition en vase à une pression pouvant atteindre 0.8 kPa. À ces basses pressions, l’influence de la hauteur hydrostatique ne peut être négligée. Cette spécificité du milieu d’ébullition a une influence non négligeable sur la taille et la forme des bulles : cette influence est analysée. Les courbes d’ébullition pour des pressions allant de 0.8 kPa à 100 kPa sont tracées. L’ébullition en vase de l’eau dans un premier temps sans puis avec confinement est également étudiée. Des courbes d’ébullition sont tracées pour différentes pressions de vapeur et différentes hauteur de la colonne d’eau. Puis, six différents espaces de confinement sont testés pour des pressions allant de 1.2 kPa à 5 kPa. Un régime d’ébullition spécifique à la basse pression est observé. L’influence de l’apparition de ce régime sur le transfert de chaleur est montrée. Le deuxième banc expérimental permet d’observer la vaporisation de l’eau dans un canal d’évaporateur à plaques de dimension standard (0.2 m de large x 0.5 m de haut) dans des conditions similaires à celles obtenues dans une climatisation à absorption (pressions de travail variant de 16 kPa à 0.85 kPa, remplissage de la plaque variant de 1/2 à1/10 de la hauteur totale de la plaque). Un plan d’expérience est réalisé pour un espacement entre deux plaques de 2 mm et 4 mm. Trois principaux régimes d’ébullition ont été identifiés ainsi que trois différentes zones de travail: une zone d’ébullition en vase, une zone d’évaporation en film et une zone de vapeur. Il a été mis en évidence que la majorité du transfert de chaleur a lieu dans la zone d’évaporation en film. Le film observé dans cette partie est créé suite à la rupture de la membrane d’une bulle de plusieurs centimètres ayant pris naissance dans la partie d’ébullition en vase. Des puissances frigorifiques allant de 0 à 503 W ont été mesurées. Les conditions pour obtenir la meilleure puissance frigorifique possible sont déterminées. Enfin, dans une première tentative vers un dimensionnement des échangeurs compacts basse pression, des premières réflexions basées sur des nombres adimensionnels ont été proposés. / In order to be able to design properly low pressure evaporators for sorption chillers, knowledge on vaporization of the refrigerant under conditions that might occur in these evaporators is fundamental. However, few studies focus on this subject and there is a lack of knowledge about vaporization (boiling or evaporation) phenomena occurring in compact evaporator at low pressure. The aim of the present thesis is thus to go further into the understanding of these phenomena both from a fundamental point of view and from an applicative point of view. In that goal, two experimental test setups were designed and built. The first experimental setup allows the observation of the water behavior at a pressure down to 0.8 kPa in pool boiling configuration. As the hydrostatic pressure is of the same order of magnitude as the vapor pressure, the boiling environment is highly subcooled. This unusual environment has an influence on the bubble size and on the bubble growth: its influence is analyzed. Boiling curves for pressures ranging from 0.8 kPa to 100 kPa were also plotted. Then, in order to be closer to a plate-type heat exchanger configuration, water pool-boiling in vertical configuration first without and then with confinement was studied. Boiling curves for a pressure ranging from 1.2 kPa to 5 kPa, different heights of the liquid level and for different channel thicknesses were plotted and analyzed. The occurrence of a specific boiling regime is observed. The influence of the onset of this specific regime on the heat transfer is shown. The significance of the Bond number, often used in study of boiling in confined space, is also discussed. The second experimental setup allows the observation of the water vaporization inside a channel of a smooth plate-type heat exchanger (0.2 m width x 0.5 m height) in conditions that might occur in sorption chillers (working pressure ranging from 16 kPa to 0.85 kPa, secondary fluid temperature ranging from 10.9 to 23.1 °C, filling ratio ranging from 1/2 to 1/10 of the whole channel height). The methodology of the design of experiments was followed for a thickness of the channel equal to 2 mm and 4 mm. Three mains flow regimes were observed and three different working areas were identified: a pool boiling area, a film evaporation area and a vapor area. The major part of the cooling capacity achieved is obtained in the film evaporation area. In this part, the creation of a liquid film due to the splashing of droplets is observed. These droplets come from the breaks of the membrane of a previously formed large bubble of several centimeters in the pool boiling area, few centimeters above the free surface. Cooling capacities ranging from 0 to 503 W were measured and conditions to obtain the best cooling capacity were determined. Finally, in order to provide some first guidelines for the design of low pressure evaporators, reflexions based on dimensionless numbers are proposed.

Solid-phase microextraction (SPME) coupled with gas chromatography/mass spectrometry (GC/MS) is routinely used to analyze polycyclic aromatic hydrocarbons (PAHs) in water. A common SPME-GC/MS approach quantifies target analytes using isotopically labeled standards (IISs); one IIS is needed for each target analyte. This approach is challenging, even prohibitive since IISs are often expensive; moreover, they are generally not available for each analyte of interest. This study developed a novel SPME-GC/MS approach for the quantification of PAHs in water. The new method, which employs only a small number of IISs, uses relative response factor (RRF) (i.e., analyte corresponding to IIS) to quantify PAHs in water. Possible matrix dependency of RRFs values was examined using water that was modified concerning different physical-chemical characteristics (i.e., ionic strength, pH, suspended solids, humic acid, and biological organic carbon represented by hemoglobin). The results revealed that RRFs are not noticeably affected by changing ionic strength and pH; the other three parameters did affect the RRFs. However, the results also showed that the effect is minimal when the solution is dilute (i.e., low concentrations of suspended solids, humic acid or hemoglobin). Relatively stable RRFs for dilute water solutions indicates that this approach can be used for routine quantification of water that does not contain prohibitive amounts of suspended solids, humic acid, and biological organic matter. The developed method was employed to quantify trace levels of PAHs in three different types of water, namely river water, well water, and bottled water. PAH levels in every kind of water were less than 100 ng/L level (i.e., 0.1 ppb). Analyses of spiked water samples containing 2 ng PAHs revealed correlations between calculated RRFs and the physical-chemical properties of the PAHs investigated (i.e., vapor pressure, boiling point, octanol/water partition coefficient, octanol/air partition coefficient, GC retention time). This implies that RRFs for PAHs not examined in this study can be predicted. Overall, the results presented herein constitute a meaningful contribution to the development of SPME-GC/MS methods for quantitative analysis of PAHs and other chemicals in dilute aqueous solutions. Moreover, the development of methods that alleviate the need for IISs corresponding to each target analyte.

La vaporisation explosive, ou flashing, par dépressurisation rapide du C6F14 au travers d'une vanne à boisseau sphérique est analysée expérimentalement sur une grande plage de surchauffe. Les visualisations rapides montrent un jet s’ouvrant très largement en aval, preuve de l'existence d'un fort gradient de pression. Des mesures locales par sonde optique et par vélocimétrie phase Doppler ont permis de caractériser tailles, vitesses, concentration et flux numérique des gouttes en fonction de la surchauffe. La faible influence du degré de surchauffe sur la remontée en pression et sur les tailles et flux de gouttes suggère que le champ de pression s’adapte, et que par conséquent le liquide est soumis à une surchauffe locale bien plus faible que la surchauffe globale imposée. Différents scenarii sont discutés pour expliquer les observations, dont le fait que les tailles de gouttes sont peu sensibles à la surchauffe. Celui basé sur l’existence d’un front d’ébullition est le plus probable. / Depressurization (flashing) experiments through a ball valve were conducted with C6F14 for a large range of superheat. High-speed imaging shows a rapid and wide expansion of the jet, which evidences strong pressure gradients. Local measurements with phase detection optical probes and phase Doppler velocimetry were used to characterize size, speed, concentration and volumetric flux of drops as a function of superheat. The level of superheat has little influence on the vaporized fraction and on drop size and flux: this suggests that due to strong pressure gradients the liquid sees a much weaker level of superheat than the global superheat imposed on the system. Different scenarii are discussed to explain observations, in particular the fact that drop size remains approximately constant independent of the superheat. A scenario based on the existence of a boiling front seems to be the most consistent.

Made available in DSpace on 2014-12-17T14:09:17Z (GMT). No. of bitstreams: 1 MarcilioPR_TESE.pdf: 2753388 bytes, checksum: 58b3cf541e2ed39d0ec5675d37151b31 (MD5) Previous issue date: 2014-02-27 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Petroleum evaluation is analyze it using different methodologies, following international standards to know their chemical and physicochemical properties, contaminant levels, composition and especially their ability to generate derivatives. Many of these analyzes consuming a lot of time, large amount of samples , supplies and need an organized transportation logistics, schedule and professionals involved. Looking for alternatives that optimize the evaluation and enable the use of new technologies, seven samples of different centrifuged Brazilian oils previously characterized by Petrobras were analyzed by thermogravimetry in 25-900? C range using heating rates of 05, 10 and 20?C per minute. With experimental data obtained, characterizations correlations were performed and provided: generation of true boiling point curves (TBP) simulated; comparing fractions generated with appropriate cut standard in temperature ranges; an approach to obtain Watson characterization factor; and compare micro carbon residue formed. The results showed a good chance of reproducing simulated TBP curve from thermogravimetry taking into account the composition, density and other oil properties. Proposed correlations for experimental characterization factor and carbon residue followed Petrobras characterizations, showing that thermogravimetry can be used as a tool on oil evaluation, because your quick analysis, accuracy, and requires a minimum number of samples and consumables / A avalia??o de petr?leo consiste em analis?-lo por diferentes metodologias, seguindo normas internacionais para conhecer suas propriedades qu?micas, f?sico-qu?micas, teor de contaminantes, composi??o e principalmente sua capacidade em gerar derivados. Muitas dessas an?lises s?o demoradas, consomem uma grande quantidade de amostras, insumos e precisam de uma organizada log?stica de transporte, cronograma de realiza??o e profissionais envolvidos. Para buscar alternativas que otimizem essa avalia??o e permitam a utiliza??o de novas tecnologias, sete amostras de diferentes petr?leos brasileiros centrifugados e caracterizados previamente pela Petrobr?s foram analisadas por termogravim?trica numa faixa de temperatura de 25 a 900?C utilizando raz?es de aquecimento de 05, 10 e 20?C por minuto. Com os dados obtidos experimentalmente, foram realizadas correla??es com as caracteriza??es disponibilizadas que permitiram: a gera??o de curvas de pontos de ebuli??o verdadeiros (Curva PEV) simulada; a compara??o entre as fra??es geradas com as devidas faixas de temperaturas de corte padr?o; uma aproxima??o para obter o fator de caracteriza??o de Watson; e comparar os res?duos de carbono micro. Os resultados mostraram uma boa possibilidade de reproduzir uma curva PEV simulada a partir da termogravimetria levando em considera??o a composi??o, densidade e outras propriedades do petr?leo; as correla??es propostas experimentalmente para o fator de caracteriza??o e res?duo de carbono acompanharam as caracteriza??es informadas pela Petrobr?s, mostrando que a termogravimetria pode ser utilizada como ferramenta na avalia??o de petr?leos, apresentando rapidez na an?lise, precis?o, al?m de necessitar de uma quantidade m?nima de amostras e insumos

A contínua mudança na qualidade da carga de alimentação das unidades de destilação atmosférica introduz incertezas na operação do processo de refino. A caracterização precisa do petróleo bruto, cuja composição varia devido à sua natureza intrínseca e às condições de transporte e armazenamento nas refinarias, poderia auxiliar na redução destas incertezas. O processo clássico de caracterização, baseado nas curvas de destilação TBP (True Boiling Point, Ponto de Ebulição Verdadeiro), ainda não permite detectar essas mudanças de modo mais dinâmico, o que reduz a precisão da simulação do processo e, portanto, uma menor confiabilidade nas condições de operação determinadas a partir dela. No Brasil, petróleo pesado é produzido de forma predominante, que é misturado freqüentemente com petróleo leve importado antes do refino. Como conseqüência, nas refinarias brasileiras as características do petróleo mudam em média, a cada três dias, sendo esta taxa de variação incompatível com a determinação das curvas de destilação TBP. A análise SimDis (Simulated Distillation, Destilação Simulada) é atualmente a técnica de laboratório alternativa para aproximar as curvas de destilação. Porém, ainda apresenta algumas características que a tornam tão limitantes quanto a análise TBP. A espectroscopia NIR (Near InfraRed, Infravermelho Próximo), tem se consagrado como uma técnica analítica rápida e viável em inúmeras aplicações industriais na determinação de diversos parâmetros qualitativos. Neste trabalho, metodologias inovadoras de caracterização são desenvolvidas visando reproduzir com maior dinamismo o processo de refino. A reprodução das curvas de destilação das cargas ao processo de destilação atmosférica da Refinaria de Capuava (RECAP ? Petrobras S.A.) através do seu espectro NIR tem sido o ponto de partida no desenvolvimento do trabalho. Métodos de calibração multivariada e redes neurais foram utilizados na construção de algoritmos computacionais que permitem a previsão dos perfis de destilação do petróleo processado, os quais foram utilizados na simulação do processo para avaliar o impacto da aplicação desta metodologia. A boa qualidade da reprodução das propriedades físico-químicas do petróleo através do NIR foi comprovada, uma vez que os modelos construídos foram condicionados às características da matéria analisada. Quanto à reprodução do cenário real do processo através da simulação, os resultados obtidos são promissores, mostrando que a caracterização da carga é útil para reproduzir mudanças no processamento. Porém, alguns aspectos precisam ainda ser aprofundados visando o melhor desempenho das metodologias. Contudo, os resultados desta pesquisa reforçam a relevância do papel da espectroscopia NIR, juntamente com técnicas clássicas de laboratório utilizadas, numa nova concepção de caracterização, que tem na rapidez e confiabilidade os seus principais aliados e pode ser aplicada na simulação de um processo visando uma melhor qualidade de operação. / The continuous variation in the quality of the feed petroleum to atmospheric distillation unities brings uncertainty to the operation of the refining process. The characterization of the crude oil, whose composition varies due to its intrinsic nature and the transport conditions and storage in refineries, could be useful in reducing the uncertainty. The classic process of characterization, based on TBP distillation curves (True Boiling Point), still does not permit to detect these changes in a more dynamic manner, which reduces the precision of the process simulation and, consequently, less confidence in the operation conditions determined from it. In Brazil, heavy petroleum is produced predominantly, which is typically blended with light imported petroleum before refining. As a consequence, in Brazilian refineries the characteristics of the petroleum change, on the average, about every three days. This rate of the petroleum change is incompatible with the determination of TBP curves. Nowadays, SimDis analysis (Simulated Distillation) is an alternative laboratory technique able to approximate the distillation curves. However, it still presents some limiting characteristics like those of TBP analysis. In the last decades, the NIR spectroscopy (Near InfraRed) has showed to be a both fast and feasible analytical technique for innumerous industrial applications in the determination of various qualitative parameters. In the present work, an innovative characterization methodology is developed aiming to reproduce more dynamically the refining process. The reproduction of distillation curves of the feed to the atmospheric distillation process of the Refinery of Capuava (RECAP ? Petrobras S.A.) from its NIR spectral determination has been the initial point for the development. Multivariate calibration methods and neural networks have been used in the construction of computational algorithms that allow the prediction of distillation profiles of the petroleum processed. These profiles were applied in process simulation in order to evaluate the impact of the application of this methodology. The good quality of the physicochemical properties of petroleum reproduction using NIR was confirmed, it is due to the fact that constructed models were conditioned to the characteristics of the samples analyzed. With respect to the reproduction of the real process behavior through simulation, the results obtained are promising, which show that the feed characterization is useful in order to reproduce process variations. However, some aspects need to be analyzed deeply in order to improve the performance of the methodologies. Finally, the results of this research strengthen the role of NIR spectroscopy together with classic laboratory techniques used in a new characterization concept, whose major advantages are the rapidity and the trustworthiness of its predictions, that can be applied in order to improve the quality of the simulation of a process.

A presente tese trata da análise experimental do efeito da geometria da seção transversal do canal e do desempenho de refrigerantes de reduzido GWP (Global Warming Potential) durante a ebulição convectiva em canais de reduzidas dimensões. A tese inclui ainda um estudo extenso e crítico da literatura sobre métodos de previsão da perda de pressão e do coeficiente de transferência de calor, e sobre estudos experimentais em canais não-circulares e de refrigerantes com reduzido GWP na ebulição convectiva em canais de dimensões reduzidas. Resultados para o coeficiente de transferência de calor e perda de pressão durante a ebulição convectiva foram obtidos para canais com geometrias de seção circular, quadrada e triangular para o refrigerante R134a. Nos testes utilizou-se canais com perímetros internos similares obtidos a partir da conformação de um tubo com diâmetro interno igual a 1,1 mm. No caso do canal circular, dados foram também levantados para os HFOs R1234ze(E) e R1234yf e o hidrocarboneto R600a, fluidos com reduzido GWP. Ensaios foram executados para amplas faixas de fluxos de calor e velocidades mássicas, temperaturas de saturação de 31 e 41°C e títulos de vapor entre 0 e 0,95. Aspectos relacionados aos efeitos da geometria e do fluido refrigerante foram minuciosamente investigados através da análise paramétrica dos resultados. Com base na comparação do banco de dados coletado com os métodos de previsão disponíveis na literatura, constatou-se que estes proporcionam previsões satisfatórias apenas para condições experimentais especificas. Portanto, novos métodos de previsão da perda de pressão e do coeficiente de transferência de calor foram desenvolvidos com base nos dados levantados no presente estudo. Os métodos propostos preveem satisfatoriamente o banco de dados do presente estudo e resultados independentes disponíveis na literatura. Adicionalmente, com base nos resultados levantados, verificou-se que dissipadores de calor baseados em multi-microcanais com canais de seção triangular apresentam desempenho superior comparados a dissipadores com canais quadrados e circulares. / The present thesis concerns an experimental study on the effects of cross-sectional geometry and low GWP refrigerants on the thermal-hydraulic performance for convective boiling inside micro-scale channels. Experimental results for heat transfer coefficient and pressure drop gradient during convective boiling were obtained for circular, square and triangular channels for the fluid R134a. The evaluated channels present the same external perimeter and equivalent diameters of 1.1, 0.977 and 0.835 mm, respectively. In the case of the circular geometry, experimental results were also acquired for the HFOs R1234ze(E) and R1234yf and the hydrocarbon R600a (isobutane), which are fluids with low GWP and null ODP. Experiments were performed for a wide range of heat fluxes and mass velocities, saturation temperatures of 31 and 41°C and vapor qualities up to 0.95. The experimental data were carefully analyzed and discussed based on a parametrical analysis focusing on the effect of the cross-sectional geometry and the working fluid. Subsequently, the experimental data were compared against the most quoted predictive methods from literature. In general, it was verified that none of the predictive methods were able to accurately capture the experimental trends of the overall database. So, new predictive methods for the pressure drop and heat transfer coefficient were developed based on the broad database obtained in the present study. The proposed methods provided satisfactory results not only for the experimental database used for its development, but also for independent databases collected in the literature. Additionally, based on the data obtained in the present study and a performance analysis taken into account pressure drop, heat transfer coefficient and the channel packing factor, triangular cross sectional geometry is recommended for heat sinks.

Submitted by NILTON ALBINO FILHO (nilton.albino@uol.com.br) on 2012-07-12T00:13:30Z No. of bitstreams: 1 Dissertação_final_NiltonAlbino.pdf: 1758566 bytes, checksum: 55bd26c77bdc345efaa5c4c3b7a23fa0 (MD5) / Approved for entry into archive by Suzinei Teles Garcia Garcia (suzinei.garcia@fgv.br) on 2012-07-12T16:00:24Z (GMT) No. of bitstreams: 1 Dissertação_final_NiltonAlbino.pdf: 1758566 bytes, checksum: 55bd26c77bdc345efaa5c4c3b7a23fa0 (MD5) / Made available in DSpace on 2012-07-12T16:44:13Z (GMT). No. of bitstreams: 1 Dissertação_final_NiltonAlbino.pdf: 1758566 bytes, checksum: 55bd26c77bdc345efaa5c4c3b7a23fa0 (MD5) Previous issue date: 2012-06-15 / Os mercados dos produtos oriundos da cana-de-açúcar no mundo vêm sofrendo nos últimos anos mudanças estruturais significativas. No cenário brasileiro, houve grande expansão da produção de cana-de-açúcar, impulsionados pela demanda dos carros flex –fuel, além da oportunidade de suprir o volume de açúcar que a União Europeia deixara de colocar no mercado mundial pela eliminação da subvenção aos exportadores de açúcar do bloco. As incertezas dos mercados exigem mudanças de estratégias de negócio, usinas projetadas para produção exclusiva de etanol, alteram sua estratégia para produção conjunta etanol e açúcar. Apesar dos processos comuns para produção de açúcar e etanol, não significa que essa mudança de estratégia seja fácil de ser efetivada, principalmente pelo aspecto energético. Estudos de processo de produção de açúcar mais eficientes energeticamente, com custos menores tem ganhado força na União Europeia, dentre elas a cristalização do açúcar por resfriamento. Vários cenários produtivos inclusive integrados a produção de etanol tem sido desenvolvidos ao longo dos anos. O objetivo do trabalho foi verificar por comparação de cenários, duas tecnologias de cristalização do açúcar (cozimento e resfriamento), em relação ao impacto nos excedentes de energia elétrica quando a produção de açúcar é adicionada a unidades que produzem somente etanol e energia elétrica. Por meio de simulações dos balanços térmicos dos cenários, observou-se uma restrição importante quando adotado a cristalização por cozimento, no que se refere aos volumes de excedentes de energia elétrica, e que pode ser minimizado se adotado o processo de cristalização por resfriamento, podendo assim ser uma alternativa quando se deseja mudar a estratégia do negócio, de produção exclusiva de etanol e energia elétrica para etanol, açúcar e energia elétrica. / Significant structural changes have been occurred in the markets of sugarcane derived products in the world in recent years. Regarding Brazilian scenario, there was a great expansion of sugarcane production due the high demand by flex-fuel cars. In addition the opportunity to meet the volume of sugar that the European Union had failed to put on the world market by eliminating the subvention to sugar exporters in the block. The uncertainties of the markets requires changes in the previus business strategies. Those mills designed for the exclusive production of ethanol, change your strategy to produce both ethanol and sugar. Despite the common processes for the production of sugar and ethanol, it does not mean that this change in strategy is easy to be effected mainly by the energy consumption. New developments in more energy efficient sugar production process, with lower costs have gained strength in the European Union, among them a sugar crystallization by cooling. Many scenarios production and integrated ethanol production have been developed over the past years. The objective of this study was to compare two technologies of sugar production such as boiling and cooling crystallization. The impact on electricity surplus when the production of sugar is added to units that produce only ethanol and electricity is discussed. By simulating the thermal balance of the scenarios, we observed an important restriction adopted when the crystallization by boiling, in terms of electricity surplus amount, which can be minimized by adopting the process of crystallization by cooling. It may therefore be an alternative when a change in the business strategy is desired from an exclusive production of ethanol and electricity to sugar, ethanol and electricity production.