L'opération de précipitation oxalique du plutonium dans les usines de retraitement du combustible nucléaire est délicate à mettre en œuvre en raison de la nature collante du précipité. Dans l'idée de pallier ce problème gênant vis à vis d'une production industrielle, le Laboratoire de génie chimique et d'instrumentation du CEA Marcoule propose de réaliser cette opération en colonne pulsée à garnissage. Le précipité est alors confiné à l’intérieur des gouttes de l’émulsion et suffisamment loin des surfaces de l'appareil.Cependant si les surfaces en contact son en acier inoxydable, l'appareil s'encrasse invariablement. La thèse s'insère alors dans une démarche de compréhension fine de ces mécanismes d'encrassement. Bien que les travaux réalisés balayent l'ensemble du problème posé, la thèse est essentiellement centrée sur l’analyse du rebond des gouttes de l’émulsion avec les parois de l'appareil. Les résultats acquis permettent d’enrichir la base de données de la littérature dans une configuration peu usitée tout en ciblant les paramètres clés de ce type d'interaction. Les résultats montrent qu'utiliser en première approche, une colonne pulsée non optimisée et conçue intégralement en acier inox ne peut convenir pour réaliser l'opération de précipitation de radionucléides. Cette précipitation peut cependant être menée en s'orientant vers une technologie différente et brevetée à l'issue de cette thèse. Ce dernier point doit cependant être nuancé car l'exploration à des débits industriels de production n'est pas encore acquise. D'un autre coté, cela peut constituer un enjeu intéressant de génie des procédés. / The process dedicated to the oxalic precipitation of plutonium is very sensitive to the high sticking behavior of the produced precipitates. Therefore, the laboratory of génie chimique et instrumentation based in Marcoule in France puts forward the idea of carrying out the process in a pulsed column. In this way, the precipitates is confined inside in the droplets of the emulsion, far from the surfaces of the apparatus. Nevertheless if those surfaces are made of stainless steal the fouling of the column is inevitably observed. The thesis also introduces the concept and tools dedicated to a fine understanding of the fouling issue. Though the work carried out scans the whole issue, the thesis mainly focuses on drop bouncing. the results provide experimental data in a low-studied configuration and target the key parameters driving th bounce. The application of the these results point out that using an unoptimized stainless steal pulsed column for the precipitation of radionucleides does not prevent from the fouling. The process could still be carried out using another technology patented during the PhD. This last poitn needs more investigations. Especially, the CEA has work on the scale-up steps to design an apparatus wich could be able to porcess industrial flow rates. Bsides ths might be an interessing issue in process engineering.

The load wetting is a widely practice used in poultry production during the pre-slaughter loading and carrying operations. According to most producers, the practice of wetting is a way to release the stress of the chickens and minimize production losses. Several studies developed in the ambience of the area have focused their attention on pre-slaughter fasting operations, capture, loading, transportation and waiting. The wetting, however, is only mentioned as a widespread practice and it was not found, however, any analysis that proves its benefit. Thus, the aim of this study was to evaluate the efficiency of cargo wetting to reduce thermal stress. For this aim, they were measured the temperature and the relative humidity, with the help of meteorological mini-stations (Data Logger), and it was calculated the enthalpy of Comfort Index (IEC), to characterize the environments where there were pre-slaughter operations. For the bioclimatic characterization (microclimate) of the load, it was carried out the analysis of the temperature distribution of the boxes located in the outer parts (right, left, top and back) by thermography (thermal imagers). Concerning the boxes located in the center of the load, where it was not possible to use the Imager, they were used eighteen data loggers, thus distributed in strategic boxes, as a record, at every minute, of the temperature and relative humidity for subsequent calculation of the IEC. It as also performed, with the help of geostatistical techniques (kriging maps), the spatial determination of temperature, relative humidity and IEC during observations with and without load wetting. There was also an attempt to determine the thermal sensation of the load during the trip of the chickens located on the right side, on the left side and on the top of the load, with the help of three thermoanemometers to record, at every minute, the temperature and wind speed and, to calculate the real comfort sensation, we used the equation of equivalent temperature Wind Chill. The approach of this work emphasizes the use of IEC and enthalpy tables, and the use of the t hypothesis testing to verify the claim that there would be no difference between the means of the IEC load of wet and dry cargo in the region with the worst heat dissipation situation (central row) during transport. The results have shown that the load wetting was not effective in alleviating the thermal stress during transportation. It can also be perceived that the use of thermography as a thermal diagnostic tool, as well as studies for modeling an equation that might represent the wind chill of the chickens, depending on the temperature and wind speed, is of great importance for the design of vehicles to transport live load. / O molhamento da carga à uma prÃtica muito utilizada na avicultura de corte, durante as operaÃÃes prÃ-abate de carregamento e transporte. Segundo a maioria dos produtores, a prÃtica do molhamento à uma forma de amenizar o estresse das aves e minimizar as perdas produtivas. VÃrios trabalhos desenvolvidos na Ãrea de ambiÃncia focaram suas atenÃÃes nas operaÃÃes prÃ-abate de jejum, captura, carregamento, transporte e espera. O molhamento, porÃm, à apenas citado como uma prÃtica muito difundida, nÃo constando, no entanto, nenhuma anÃlise que comprove o seu benefÃcio. Sendo assim, o objetivo deste trabalho foi avaliar a eficiÃncia do molhamento da carga na reduÃÃo do estresse tÃrmico. Para isso, foram medidas a temperatura e a umidade relativa, com o auxÃlio de miniestaÃÃes meteorolÃgicas (Data Logger), e calculado o Ãndice Entalpia de Conforto (IEC), para a caracterizaÃÃo dos ambientes onde ocorreram as operaÃÃes prÃ-abate. Para a caracterizaÃÃo bioclimÃtica (microclima) da carga, foi realizada a anÃlise da distribuiÃÃo da temperatura das caixas localizadas nas partes externas (lateral direita, esquerda, topo e traseira) atravÃs da termografia (termovisores). As caixas localizadas no centro da carga, onde nÃo foi possÃvel o usar o termovisor, foram utilizados dezoito Data Loggers, distribuÃdos em caixas estratÃgicas para o registro, a cada minuto, da temperatura e umidade relativa, para posterior cÃlculo do IEC. Procedeu-se, ainda, com a ajuda de tÃcnicas de geoestatÃstica (mapas de Krigagem), a determinaÃÃo espacial da temperatura, umidade relativa e IEC durante as observaÃÃes com e sem o molhamento da carga. TambÃm se tentou determinar a sensaÃÃo tÃrmica durante a viagem dos frangos localizados nas laterais direita, esquerda e topo da carga, com a ajuda de trÃs termoanemÃmetros para registro, a cada minuto, da temperatura e velocidade do vento e, para o cÃlculo da real sensaÃÃo de conforto, foi utilizada a equaÃÃo da temperatura equivalente de Wind Chill. A abordagem deste trabalho dà Ãnfase ao uso do IEC e das tabelas de Entalpia, alÃm do uso do teste de hipÃteses t para verificar a afirmaÃÃo de que nÃo haveria diferenÃa entre as mÃdias do IEC da carga molhada e da carga seca, na regiÃo que apresenta a pior situaÃÃo de dissipaÃÃo do calor (fileira central) durante o transporte. Os resultados mostraram que o molhamento da carga nÃo se mostrou eficiente em amenizar o estresse tÃrmico durante o transporte. Pode-se ainda constatar que o uso da termografia como ferramenta de diagnÃstico tÃrmico, assim como estudos para a modelagem de uma equaÃÃo que retrate a sensaÃÃo tÃrmica da ave em funÃÃo da temperatura e velocidade do vento, à de suma importÃncia para o projeto de veÃculos de transporte de carga viva.

Abstract This thesis presents an effective optical method for measuring liquid sorption into paper. From the two tested methods, based on a streak-camera and optical coherence tomography (OCT), the last-mentioned proved very promising for investigating dynamical paper-liquid interactions as spatially and temporally dependent processes. The streak-camera measurements were performed to explore the relationship between paper properties and light migration in dry and refractive index matched paper in general. Based on streak-camera measurements, a novel procedure for determining the average refractive index of cellulose fibre tissue was also presented here. In addition, the streak camera method lent itself to paper porosity determination. Results of the performed OCT measurements proved that liquids cannot penetrate into paper before filling the pores and pits of the paper surface. As a liquid penetrated into paper, the border between the wetted and dry area could be investigated in the depth direction. The liquid penetration velocity seemed to be slower at the beginning and end of the process. Liquid absorption into paper fibres could be investigated concurrently. For the first time, the location and moment of structural changes in paper could be determined during wetting, and the effect of three different coexistent subprocesses related to paper wetting could be detected. OCT only fell short of detecting the effect of liquid migration along fibres. Despite the limitations of the utilized method (resolution, probing depth and depth scanning rate), the obtained OCT measurement results are very promising for the development of an effective paper wetting measurement device for industrial applications. Even if this thesis focused on paper wetting, it is reasonable to assert that the presented ideas and obtained results have more general value in terms of explaining liquid penetration into porous structures and offer an alternative method of evaluating that process.

This thesis investigates the wetting of simple liquids using two density functional theory (DFT) models. The first model is a discrete lattice-gas model and the second a continuum DFT model of a hard-sphere reference system with an additional attractive perturbation. The wetting properties of liquids are principally investigated by studying the binding, or interface, potential of the fluid and this thesis presents a method by which a binding potential can be fully calculated from the microscopic DFT. The binding potentials are used to investigate the behaviour of the model fluid depending on the range to which particle interactions are truncated. Long ranged particle interactions are commonly truncated to increase computational efficiency but the work in this thesis shows that in making this truncation some important aspects of the interfacial phase behaviour are changed. It is demonstrated that in some instances by reducing the interaction range of fluid particles a shift in phase behaviour from wetting to non wetting occurs. The binding potential is an input to larger scale coarse grained models and this is traditionally given as an asymptotic approximation of the binding potential. By using the full binding potential, calculated from the DFT model, as an input, excellent agreement can be found between the results from the microscopic DFT model and the larger scale models. This is first verified with the discrete lattice-gas model where the discrete nature of the model causes some non-physical behaviour in the binding potentials. The continuum DFT model is then applied which corrects this behaviour. An adaptation to this continuum model is used to study short ranged systems at high liquid densities at state points below the `Fisher-Widom' line. The form of the decay of the density profiles and binding potentials now switches from monotonic to oscillatory. This model leads to highly structured liquid droplets exhibiting a step-like structure.

Este trabalho tem por objetivo estudar a molhabilidade e a permeabilidade para quatro espécies de madeiras tropicais (Pinus elliottii, Araucaria angustifolia, Eucalyptus grandis e Eucalyptus citriodora). A molhabilidade é um parâmetro importante para a caracterização de diferentes espécies de madeira e, portanto, depende de fatores como o estado de limpeza da superfície da madeira, orientação das fibras, tipo de amostra (alburno ou cerne), secagem, tratamentos térmicos e químicos, rugosidade superficial, etc. Primeiramente, investigamos a molhabilidade para as quatro espécies tropicais por medida de ângulo de contato aparente para diferentes solventes na superfície da madeira As amostras foram tratadas termicamente no intervalo 100 200º C, por 8h e foi utilizado o método da gota séssil e um goniômeto. Os valores dos ângulos de contato foram maiores para as amostras submetidas aos tratamentos térmicos, indicando um aumento no caráter hidrofóbico da madeira. A técnica de ângulo de contato não foi eficiente para tratamentos térmicos superiores a 200º C, devido a sua degradação. No experimento de permeabilidade foi utilizado um fluxo de ar através das amostras com poros fechados e abertos. Foi verificado um acréscimo de 82 % na vazão para as situações de poros abertos no Eucalyptus citriodora. Nossos resultados permitem detectar mudanças consideráveis na molhabilidade e permeabilidade da madeira, sendo informações valiosas para a conservação e utilização destas madeiras. / This work aims to study wettability and permeability for tropical wood species (Pinus elliotti, Araucaria angustifolia, Eucalyptus grandis and Eucalyptus citriodora).The adhesive wettability is an important parameter for characterizing different wood species and depends on factors such as cleaning state of the wood surface, orientation of the wood fibers, type of sample (sapwood or heartwood), drying, thermal and chemical treatments, surface roughness, etc. First, we investigated the wettability of the four tropical wood species by measuring the apparent contact angles of different solvents on the wood surfaces. The samples were heat treated from 100 to 200 °C for 8 h, and the contact angles measured by the sessile drop method with a home-made goniometer. For samples heat-treated below 200 °C, higher values of contact angles were obtained, indicating a hydrophobic character for thermal treated woods. After this temperature, the wood degradation took place. For permeability experiments, a flow of air was used for wood samples with closed and open pores. An increase of 82% in flow was verified for open pores woods such as Eucalyptus citriodora. Our results allowed us to detect considerable changes on wood wettability and permeability and that are powerful information for conservation and use of these woods.

Avec une population toujours croissante et la pénurie de plus en plus importante des ressources en eau douce, l’humanité s’est tournée vers les océans pour ses besoins en eau potable. Afin de faire face aux limites des procédés conventionnels de dessalement d’eau de mer, la distillation membranaire (DM) connaît un intérêt croissant. Même si l’intérêt envers la DM pour le dessalement d’eau de mer est apparu au cours des dernières décennies, aujourd’hui le risque de mouillage des membranes est l’un des obstacles majeurs à son développement industriel. Dans le cadre du projet ANR « WETMEM», l’objectif de cette thèse est de développer des outils de compréhension des mécanismes de mouillage en distillation membranaire sous vide. Plusieurs membranes, fabriquées par des partenaires du projet WETMEM, et commerciales ont été étudiées afin de comprendre l’influence des propriétés des membranes sur les indicateurs de mouillabilité. De plus, une définition et une classification des mécanismes de mouillage ont été proposées. Par la suite, deux indicateurs de mouillage ont été développés à l'aide de la microscopie électronique à balayage et de la spectroscopie de dispersion de rayons X selon une méthode appelée « Détection d'intrusion de traceur dissous ». Une preuve de concept a été fournie, dans laquelle différents mécanismes de mouillage ont pu être visualisés et interprétés. Ces indicateurs ex situ ont alors été utilisés avec des indicateurs de mouillabilité (Angle de contact, Pression d’intrusion de liquide) afin de comprendre l’influence de la température (35-50 ° C), de la salinité (22-310 g / L de NaCl sol.) et du débit (400 - 4000 Re) sur le mouillage et la mouillabilité d'une membrane de PVDF en distillation membranaire sous vide. Il a alors été constaté que la salinité a l’impact le plus important sur le mouillage par rapport aux autres paramètres de fonctionnement. En outre, un outil optique in-situ non invasif a été développé. Il permet de visualiser le mouillage in-situ en distillation membranaire. La progression du mouillage in situ a été observée à différentes échelles et pour différentes solutions salines et eaux de mer. / With an ever-increasing population and the growing disparity in potable water resource, humanity has turned its attention to the oceans for its potable water needs. To overcome the current limitations in current desalination technologies, membrane distillation (MD) is actively being developed. The interest of MD for seawater desalination was established in the last decades but today the risk of membrane wetting is one of the major barrier for industrial implementation of MD. Under the framework of the ANR project “WETMEM”, the issue of this thesis was to develop tools for better understanding wetting mechanisms in vacuum membrane distillation. Several fabricated (WETMEM partners) and commercial membranes were studied to understand the influences of membrane properties on wettability. Therefore, a definition and classification on wetting were formulated. After that two wetting indicators were developed using scanning electron microscopy and X-ray dispersion spectroscopy under a method called “Detection of Dissolved Tracer Intrusion”. A proof of concept was provided with various wetting mechanisms visualized and interpreted. These ex-situ indicators were used with wettability tools (Contact Angle, Liquid Entry Pressure) to understand the influence of temperature (35-50°C), salinity (22-310 g/L NaCl sol.) and flow rate (400 – 4000 Re) on wetting and wettability of a PVDF membrane under vacuum membrane distillation. Indeed, it was found that salinity has a greater impact on wetting than the other operating parameters. Additionally, a proof of concept was provided for non-invasive in-situ optical method for visualizing wetting in membrane distillation. Progression of in-situ wetting visualization was validated at different scales for various saline solutions and seawaters.

This thesis deals with the methodology of testing the wetting characteristics for different material and process effects in the double-plated base material. Testing is performed by wetting balance method. There is designed procedure to calculate the angles on each side of the non-homogeneous material. The Design of Experiments method is used to interpret the results, by using this method are also interpreted electrical and mechanical properties of solder joints. The correlation with wetting characteristics is discussed.

Usually one distinguishes partial and complete wetting of surfaces or interfaces. In case of partial wetting contact angle θ > 0 and the liquid droplet is surrounded by “dry” surface or interface. In the majority of cases the direct transition occurs from partial wetting into complete wetting, for example by increasing temperature or decreasing pressure. However, in some cases the state of pseudopartial wetting occurs between partial and complete wetting. In this case the contact angle θ > 0, the liquid droplet does not spread over the substrate, but the thin (few nm) precursor film exists around the droplet and separates substrate and gas. Such precursor film is very similar for the liquid “pancake” in case of complete wetting and deficit of the liquid phase. The pseudopartial wetting has been observed before only for liquid/liquid mixtures (alcanes/water solution of salt or glucose) or Pb and Bi on the Cu surface. We observed the pseudopartial wetting of Al/Al grain boundaries (GBs) by solid Zn in the Al – 10 wt.% Zn ultra-fine grained polycrystals. The solid Zn partially wets Al/Al GBs (with non-zero contact angle). Nevertheless, the Al/Al GBs contain the 2 nm thin uniform Zn-rich layer connected with Zn grains. Such thin layers are the reason of high ductility of ultra-fine grained Al–Zn alloys at room temperature. This phenomenon opens the way for development of novel light-weight alloys. The pseudopartieal GB wetting by a liquid phase exists also in the WC–Co hard alloys. The pseudopartieal GB wetting by various liquid and solid phases also controls the properties of Nd–Fe–B-based hard magnetic alloys.

No description available.

A moving contact line is the idealized line of intersection between two immiscible fluids as one displaces the other along a solid boundary. The displacement process has been the subject of a large amount of theoretical and experimental research; however, the fundamental processes that govern contact line motion are still unknown. The challenge from an experimental perspective is to make measurements with high enough resolution to validate competing theories. An experimental method has been developed to simultaneously measure interface motion, dynamic contact angles, and local fluid velocity fields using micron-resolution Particle Image Velocimetry (µPIV). Capillary numbers range from 1.7 x 10^(⁻⁴) to 6.2 x 10^(⁻⁴). Interface velocities were measured between 1.7 µm/s and 33 µm/s. Dynamic contact angles were manually measured between 1.1 µm and 120 µm from the contact line, and calculated from µPIV data to within several hundred nanometers from the contact line. Fluid velocities were measured over two orders of magnitude closer to the contact line than published values with an increase in resolution of over 3400%. The appearance of a recirculation zone similar to controversial prediction below previously published limits demonstrates the power and significance of the method.