La majorité des bâtiments existant aujourd'hui ne respectent pas les réglementations thermiques actuelles. Pour répondre aux exigences environnementales il est impossible, dans ce contexte, d'envisager une politique globale de démolition-reconstruction. Des campagnes de réhabilitation doivent être mises en place. Une solution innovante de réhabilitation énergétique est proposée permettant d'exploiter les ressources énergétiques urbaines, peu utilisées actuellement. Elle consiste à rajouter autour du bâtiment une enveloppe extérieure qui aurait pour fonction principale le captage d'énergie solaire. Un outil d'optimisation de la géométrie de l'enveloppe et de la distribution spatiale de panneaux capteurs à sa surface est développé. Sa validation est effectuée sur des cas simples, puis il est appliqué aux situations présentant de forts contrastes : optimisation pendant la période d'hiver ou d'été, à Oslo ou à Tunis, avec des obstacles proches masquant le Soleil. Afin de réaliser les formes complexes obtenues, il est proposé d'utiliser les gridshells comme système constructif. Ces structures obtenues par déformation élastique d'une grille de poutres en matériau composite initialement planes posent la question de la durabilité de ces matériaux soumis au chargement permanent. Pour étudier le comportement à long terme (fluage et rupture différée) de ces matériaux composés de fibres de renfort et matrice polymère viscoélastique, un modèle micro-mécanique est développé. Ce modèle de type shear-lag permet d'étudier l'influence des propriétés mécaniques des constituants sur la durée de vie du composite soumis à un chargement en traction et traction-cisaillement combinés / The majority of existing buildings does not follow present energy efficiency regulations. In order to fulfill environmental requirements it seems impossible, in this context, to consider a global demolition-reconstruction policy. Renovation programmes need to be implemented. An innovative energy efficiency improvement solution is proposed, enabling to explore urbain energy ressources presently underexploited. The concept is to add, around the building, an external envelope whose main function would be to collect energy. An optimization tool aiming at finding the optimal geometry and collectors' spatial distribution on the envelope's surface, is developed. Its validation is carried out on simple cases, it is then applied in situations showing strong contrasts: optimization during summer and winter, in Oslo and in Tunis, with close obstacles partially masking the Sun. In order to build the emerging complex geometries, the use of gridshell structures is proposed. These structures are obtained through elastic deformation of an initially plane grid made of composite material slender beams. This raises the problem of composite materials durability under sustained loading. In order to study the long-term behavior (creep and creep rupture) of these materials composed of reinforcing fibres and a polymeric viscoelastic matrix, a micromechanical model is developed. This shear-lag type model allows studying the influence of the constituents' mechanical properties on the lifespan of the composite under permanent pure traction or combined shear and traction loadings

A pressão positiva contínua nas vias aéreas (CPAP) é a forma mais simples de ventilação não invasiva e pode ser oferecida por gerador de fluxo, ventiladores mecânicos para ventilação não invasiva ou ventiladores específicos, contudo seu uso tem sido limitado devido a algumas desvantagens encontradas nos sistemas existentes, como tamanho e custo elevado. Um novo e compacto sistema para CPAP foi recentemente introduzido, denominado Sistema de CPAP Boussignac (Vygon, Ecouen, France). Esse sistema fornece pressão positiva contínua por meio da injeção de altos fluxos de gás (ar comprimido/oxigênio), em um cilindro ligado a canais laterais angulados. Este estudo tem por objetivo avaliar laboratorialmente a eficiência do desempenho do Sistema de CPAP Boussignac alimentado por fluxômetro de oxigênio, por meio de um modelo mecânico de pulmão. O estudo foi experimental utilizandose um modelo mecânico de pulmão ASL5000 (IngMar Medical, Pittsburg, PA, USA). Para tal, o equipamento foi testado em CPAP de 5, 10, 15 cmH2O na simulação de três condições clínicas, a saber: normal (Rrs = 3,5 cmH2O/L/s, Crs = 80 mL/cm H2O), DPOC (Rrs inspiratória = 10 cmH2O/L/s, Rrs expiratória = 20 cmH2O/L/s e Crs = 60 mL/cmH2O) e EAP Rrs = 10 cmH2O/L/s, Crs = 30mL/cmH2O), em que se procurou: verificar a diferença na manutenção de pressão, em cada condição clínica, considerando submissão a altos e baixos esforços; verificar o comportamento do sistema em relação à área da curva de inspiração abaixo do nível do CPAP para checar a capacidade do equipamento em manter nível pressórico constante na via aérea; avaliar seu comportamento quanto à oferta suficiente ou insuficiente de fluxo observando e registrando valores de fluxo de alimentação e saída ofertados por distintas fontes de alimentação para gerar níveis de CPAP de 5, 10 e 15cmH2O para o Sistema Boussignac. Os resultados indicaram que o Sistema Boussignac é eficiente em manter nível pressórico pré-ajustado em diferentes condições clínicas e esforços respiratórios, mantendo diferenças menores que 8,7% entre o CPAP medido e o predeterminado em todas as condições simuladas. As médias dos valores de ÁREACPAP foram próximas a zero, e a média do maior valor atingido foi 1,3 cmH2O para a condição clínica normal em CPAP de 15 cmH2O e alto esforço respiratório. O equipamento apresentou oferta suficiente de fluxo de saída, mantendo estabilidade do sistema em altos e baixos esforços respiratórios, tendendo a um menor consumo de oxigênio em relação a outros geradores de fluxo. A relação entre as distintas fontes de alimentação mostrou que elas podem ser alteradas sem implicação no fornecimento do nível de CPAP desejado, porém deve ser aberta cada uma em seu correspondente valor. Em conclusão, observou-se que o Sistema de CPAP Boussignac é um equipamento eficiente e econômico que pode ser muito útil na prática clínica, com contribuições específicas às técnicas de pressão positiva não invasiva nas vias aéreas. Por ser um sistema pequeno, facilita a aplicação, o manuseio e a instalação. / Continuous positive airway pressure (CPAP) is the simplest form of noninvasive ventilation and it can be applied through flow generator, mechanical ventilators for noninvasive ventilation or specific ventilators. However, its use has shown to be limited because of a few disadvantages found in the existing systems, such as size and high cost. A novel compact CPAP system was recently been introduced, and is called Boussignac CPAP System (Vygon, Ecouen, France). This system provides continuous positive pressure by injecting high gas flows (air/oxygen) through a cylinder connected to angulated lateral channels This study aims at assessing the laboratorial performance efficiency of the Boussignac CPAP System fed by an oxygen flow meter, using a mechanical lung model. It was an experimental study using a mechanical lung model ASL5000 (IngMar Medical, Pittsburg, PA, USA). The equipment was tested under continuous positive airway pressure (CPAP) of 5, 10, and 15 cmH2O simulating three clinical conditions: normal (Rrs = 3.5 cmH2O/L/s, Crs = 80 mL/cm H2O), DPOC (Inspiratory Rrs = 10 cmH2O/L/s, expiratory Rrs = 20 cmH2O/L/s and Crs = 60 mL/cmH2O) and EAP (Rrs = 10 cmH2O/L/s, Crs = 30mL/cmH2O), in which we attempted to verify the difference in pressure maintenance in each clinical condition, considering submission to high and low efforts; verify system behavior regarding the area of the inspiration curve below CPAP level so as to check equipment capacity of keeping continuous pressure level in the airway; assess equipment behavior regarding provision of sufficient or insufficient flow, observing and recording in and output flow values provided by different sources so as to generate CPAP levels of 5, 10, 15 cmH2O for the Boussignac system. The results showed that the Boussignac system is efficient to maintain preset pressure levels in different clinical conditions and respiratory efforts, keeping the differences lower than 8.7% between measured and preset CPAP in all the conditions simulated. The average AREACPAP values were close to zero, and the peak value average was 1.3 cmH2O for normal clinical condition under CPAP of 15 cmH2O and high respiratory effort. The equipment provided sufficient output flow, keeping system stability during high and low respiratory efforts. It also tended to consume less oxygen compared to other flow generators. The relation between the different feed sources showed that they can be altered without compromising the desired CPAP level. However, each source should be opened at its corresponding value. In conclusion, the Boussignac CPAP System was deemed efficient and economic, and it can be very useful in clinical practice, with specific contributions to noninvasive positive airway pressure techniques. Since it is a small system, its application, handling, and installation are facilitated.

Processos colisionais envolvendo transferência de energia têm sido intensivamente investigados em amostras de átomos de Rydberg frios nos últimos anos. Alguns grupos de pesquisa têm interpretado tais processos utilizando um modelo de muitos corpos; nosso grupo tem explicado tais processos, considerando a interação de dois corpos em um potencial de ultralongo alcance e o movimento sob a ação de um potencial. Nesta tese nós investigamos tais processos de colisão envolvendo átomos de Rydberg frios, produzidos em uma armadilha magneto-óptica. A investigação da evolução temporal de estados de Rydberg produzidos por colisões para diferentes densidades atômicas nos permite demonstrar que o processo binário é dominante. Além disso, mostramos que a radiação de corpo negro não pode ser desprezada nestes experimentos. Finalmente, sugerimos melhorias para um modelo semi-clássico de dinâmica colisional proposto por nosso grupo. / Collisional processes involving energy transfer have been intensively investigated in samples of cold Rydberg atoms in the last years. Some research groups have interpreted such processes using a many body model; on the other hand our group has explained such processes considering a two body interaction in an ultralong range potential and the atomic motion under the influence of such potential. In this work, we have investigated such atomic collisions involving cold Rydberg atoms, produced in a magneto-optical trap. The time evolution study of the Rydberg states produced by collisions for different atomic densities has shown us that the binary process is dominant in such system. Beyond that, we have shown that the radiation of black body cannot be neglected in these experiments. Finally, we suggest improvements for the semi-classical collissional dynamic model proposed by our group.

O tratamento anti-HIV conhecido como HAART (Highly Active Antiretroviral Therapy) se tornou comum por volta de 1996, e utiliza 3 ou 4 diferentes medicamentos em combinação - geralmente dois inibidores de transcriptase reversa + 1 ou 2 inibidores de protease. A introdução desse tipo de tratamento trouxe um grande impacto na morbidade e mortalidade de indivíduos infectados pelo HIV. Os inibidores de protease (PIs) são uma boa alternativa às falhas terapêuticas observadas com o uso dos inibidores de transcriptase reversa, no entanto também são associados a vários efeitos tóxicos, como desconforto abdominal, vômito, diarréia, dor de cabeça, tontura, lipodistrofia, hipercolesterolemia, hipertrigliceridemia e hiperglicemia. Em função da existência de efeitos adversos e da condição do ritonavir como protótipo desse tipo de medicação, nosso objetivo é avaliar o efeito desse medicamento sobre os epitélios de revestimento e glandular relacionados à cavidade bucal, de forma a identificar a possibilidade da existência de complicações bucais relacionadas ao uso de inibidores de protease. Ratos albinos (Wistar) foram tratados com Ritonavir (10mg/Kg) por períodos de 4 e 8 semanas. Foram avaliadas as taxas séricas de triglicérides e colesterol (total, HDL, LDL, VLDL). Ao final dos períodos de tratamentos propostos, os animais foram sacrificados, e as peças utilizadas no estudo foram colhidas, (sangue, pele, língua, palatos e glândulas salivares). O sangue coletado foi imediatamente centrifugado sendo o plasma foi utilizado para avaliação das lipoproteínas. Os tecidos colhidos foram fixados, descalcificados quando necessário, processados para inclusão em parafina, cortados com 6µm de espessura, montados em slides e corados com hematoxilina e eosina, para avaliação histopatológica, morfométrica e estereológica. Os dados colhidos foram apresentados em valores médios, e as diferenças analisadas por testes estatísticos adequados para a comparação entre as amostras. Nossos resultados mostram pequenas variações nas características morfológicas de epitélios de revestimento e glandulares, variações essas que poderiam deixar esses tecidos mais propensos a sofrer alterações significativas com traumas ou injúrias, comuns nos tecidos bucais. Embora observadas com pequeno grau de expressão, essas variações, parecem ser progressivas, ou seja, mais expressivas com o uso continuado do medicamento. Mais estudos devem ser realizados, principalmente voltados para avaliações histoquímicas, bioquímicas e moleculares, no entanto nosso estudo é um alerta inicial para a avaliação dos tecidos bucais de pacientes que utilizam inibidores de protease. / HAART had a dramatic impact on the HIV infection, however, protease inhibitor exhibit significant drug-drug interactions, and side effects. There are only few data on effects of protease inhibitors on oral tissues. We propose to observe experimental effects of ritonavir on oral epithelial tissues, covering and glandular. Wistar rats received Ritonavir twice a week for 4-8 weeks. Controls received no treatment. At the time for sacrifice, plasma were collected for evaluation of triglycerides, total cholesterol, HDL, LDL and VLDL. Were also collected skin, tongue, palate and glandular tissues Lipoproteins were evaluated and histological examination of skin, mucosal epithelium on tongue, palate and salivar submandibular glandula were made under light microscope. Morphometric methods (cariometry and stereology) were used. Data were statistically analysed by Kruskal Wallis test for multiple samples, since our data were considered not-normal. P[U] 0.05 were considered statistically significant. Our results show that protease inhibitor may be associated with small alterations in epithelial tissues, significant mostly when on longer times using the medication. The complete significance of this data has to be better understood, and other studies has to be done to define these points.

Bei Patienten, die auf Grund einer schweren Beckenverletzung hämodynamisch instabil sind, ist die primäre Stabilisierung des Beckens und damit die Reduktion des intrapelvinen Volumens entscheidend für den Erfolg der weiteren Therapie. Die Beckenzwinge hat sich als Notfallmaßnahme bewährt, erfordert jedoch in den meisten Fällen eine weitere operative Versorgung. Dieser Sekundäreingriff bedingt in vielen Fällen bei traumatisch geschädigten Weichteilen zusätzliche Wundheilungsstörungen. Ein weiteres Verfahren, der ventrale Fixateur externe, zeichnet sich durch einfache und schnelle Montage bei nur geringem Weichteilschaden aus. In vielen Fällen ist jedoch keine für die Mobilisierung ausreichende biomechanische Stabilisierung des vertikal instabilen dorsalen Beckenringes zu erreichen. Anhand biomechanischer Überlegungen wurde ein neuer schräg dorsaler Beckenfixateur für Becken- C-Verletzungen entwickelt, der die Vorteile des supraacetabulären Fixateur externe nutzt und dabei den hinteren Beckenring von ventral mit einer der Beckenzwinge nahe kommenden Effektivität stabilisieren kann. Er ermöglicht bereits initial eine minimal invasive sowie definitive Stabilisierung des dorsalen Beckenrings. Mehrere Variationen mit zwei unterschiedlichen Pin- Applikationsformen dieses asymmetrischen Fixateurs wurden getestet. In einer zweiten Testreihe wurde die in der ersten Testreihe favorisierte Version des neuen schräg dorsalen Fixateurs mit dem Supraacetabulärem Fixateur externe und der Beckenzwinge (ACE) verglichen. Beide Testreihen erfolgten an Kunststoff-Beckenmodellen im Einbeinstand in einer Materialprüfmaschine. Als Instabilitätsmodell dienten Verletzungen vom Typ C1.2 sowie C1.3 entsprechend der AO Klassifikation. In den Testreihen wurde kein signifikanter Unterschied des neuen verspannten schräg dorsalen Fixateurs zur Beckenzwinge gefunden. Er war jedoch deutlich stabiler als das unverspannte Modell oder der supraacetabuläre Fixateur allein. / In haemodynamically unstable patients with an unstable pelvic ring injury the primary stabilisation of the pelvis and thus reduction of pelvic volume is important for the success of the treatment. The pelvic C-clamp is an approved emergency device for these unstable pelvic ring injuries. A secondary procedure though is necessary in most of the cases with a big rate of wound problems in already traumatized soft tissue areas. The ventrally placed external fixator is a simple and quick procedure with little soft tissue damage. Though primary stability is sufficient even for C-type injuries, biomechanic stability of the posterior pelvic ring is often insufficient for mobilization. Based on biomechanic considerations, a new dorsal oblique pelvic external fixator was developed for pelvic C-type injuries. With the advantages of the supraacetabular fixator and two additional Schanz screws the ventral fixator should stabilize the posterior pelvic ring with comparable stability to the pelvic C-clamp. A primary and already definitive minimal invasive stabilization of the posterior pelvic ring was the aim. In the first series several variations of this asymmetric fixator with two different Schanz screw applications were tested biomechanically. In a second series the favourite version was tested versus the supraacetabular fixator and the pelvic C-clamp. Both of the biomechanic test series were performed with artificial pelves in the one leg stance model in the material testing machine. SI disruption and sacral fracture were the posterior instability types in 6 pelves each. There was no statistically significant difference between the dorsal oblique fixator and the pelvic C-clamp. But the new fixator was significantly more stable than the supraacetabular fixator or the new fixator without pretension.

Esta dissertação é resultado de uma pesquisa que investigou o comportamento linguístico de crianças falantes nativas de português brasileiro com relação a sentenças absolutas, que consistem em uma alternância na valência de verbos transitivos encontrada especificamente no PB, tal como Eu aperto esse botão [do videogame] e, olha lá, a bola chutou. Segundo Negrão & Viotti (2010), nas absolutas o argumento que representaria a energia responsável pela causa do evento não está presente e nem chega a ser conceitualizado. Não há, portanto, a presença de uma força indutora (Negrão & Viotti, 2010). Desenvolvemos dois experimentos: um de tarefa de produção eliciada e outro de julgamento de aceitabilidade. Nossas previsões são: (a) as absolutas serão mais produzidas com a ausência da força indutora, que seria o argumento agente; (b) alguns verbos proporcionarão mais a produção de absolutas que outros, por estarem mais propensos à supressão da força indutora; e (c) crianças produzirão mais absolutas do que passivas visto que as absolutas são menos complexas estruturalmente. As condições testadas foram: presença/ausência de um agente e tipo de verbo (mais ou menos propenso à supressão do agente). Os resultados sugerem que ambas as condições influenciaram nas respostas dos participantes, de modo que os contextos sem agente e os contextos com verbos mais propensos à supressão do agente se mostraram mais propícios às sentenças absolutas. Por fim, as crianças mais novas testadas produziram mais absolutas do que passivas, o que indica que a absoluta, por ser menos complexa, é uma estrutura mais acessível às crianças. / This dissertation is the result of a research that has investigated the linguistic behavior of Brazilian Portuguese speaking children in relation to absolutive sentences, which consist of a verb valency alternation found specifically in BP, such as Eu aperto esse botão [do videogame] e, olha lá, a bola chutou (I press this button [in the videogame] and, look, the ball kicked [in the sense that the ball was kicked]). According to Negrão & Viotti (2010), in the absolutive constructions, the argument that would represent the energy responsible for the cause of the event is not present. Actually, it is not even conceptualized. Therefore, there is no driving force (Negrão & Viotti, 2010). We developed two experiments: an elicited production task and an acceptability judgment task. Our predictions are: (a) the absolutive sentences will be produced more often in contexts without a driving force, which would be, in this case, the agent; (b) more absolutive sentences will be produced with some verbs than others, because they are more likely to suppress the driving force; and (c) children will produce more absolutive constructions than passives since the absolutive construction is structurally simpler. The tested conditions were: presence/absence of an agent and verb type (more or less likely to suppress the agent). The results suggest that both conditions influenced participants answers, so that the contexts without an agent and the contexts with verbs more likely to suppress the agent were more supportive environments for the absolutive constructions. Finally, the younger children we tested produced more absolutive constructions than passives, which indicates that, as a less complex structure, the absolutive is more accessible to children.

L'utilisation massive des énergies fossiles est en grande partie responsable des émissions de gaz à effet de serre. De plus, la croissance de la demande énergétique et la raréfaction des ressources fossiles conduisent à l'accroissement du coût de l'énergie. La réponse à cette problématique passe par deux moyens d'action indissociables : la réduction des consommations énergétiques et le recours aux énergies renouvelables. La fenêtre pariétodynamique permet d’agir sur les deux postes principaux de déperdition thermique d’un bâtiment que sont les baies et la ventilation. Le principe de la fenêtre pariétodynamique étudiée est de faire circuler de l’air en convection forcée entre trois verres avant d’être restitué à l’ambiance intérieure du bâtiment. Cela permet à l’air de récupérer à la fois une partie des déperditions thermiques à travers la fenêtre et une partie de l’énergie solaire absorbée par les verres. Afin d’étudier le comportement thermo-aéraulique et les performances de la fenêtre, nous avons développé un modèle numérique de cette dernière. Un dispositif expérimental a été mis en place et utilisé afin de valider le modèle numérique et de comparer en conditions réelles les performances de la fenêtre étudiée à celles d’une fenêtre à double vitrage classique. Ces résultats expérimentaux ont été complétés par une étude paramétrique numérique réalisée pour différentes conditions climatiques et de fonctionnement. Les principaux enseignements issus de ces études expérimentales et numériques sont que le préchauffage de l’air se fait essentiellement dans la lame d’air intérieure, la température de la première lame d’air restant proche de celle de l’air extérieur. De plus, et contrairement aux températures de la face intérieure et de l’air soufflé, celle de la face externe de la fenêtre est peu impactée par les paramètres étudiés. Concernant le cadre de la fenêtre, nous avons observé que celui-ci bénéficie aussi des échanges thermiques avec l’air circulant, mais dans une moindre mesure. Cela contribue à rendre la fenêtre peu déperditive. Enfin, en couplant le modèle développé à un logiciel de simulation thermique dynamique, nous avons évalué le potentiel d’intégration de fenêtres pariétodynamiques dans une maison individuelle. Nous mettons ainsi en évidence que le besoin de chauffage est réduit d'environ 20 à 30 % par l’utilisation de fenêtres pariétodynamiques à la place de fenêtres à double vitrage classique. En été, si l’ambiance intérieure du bâtiment est plus fraîche que l’environnement extérieur, la fenêtre pré-rafraîchit l’air neuf entrant. / The massive use of fossil energies is largely responsible for greenhouse gas emissions. Moreover, the growth in energy demand and the depletion of fossil resources lead to an increase in energy costs. The response to this challenge requires two means of action which are linked : the reduction of energy consumption and the use of renewable energy. The airflow window acts on the two main ways of building heat losses that are windows and the ventilation. The principle of the studied airflow window is based on the circulation of fresh air, by forced convection, between the three glasses of the window before entering the building. This allows air to recover both a part of heat losses through the window and part of the solar energy absorbed by the glasses. To study the thermo-aeraulic behavior and thermal performances of the window, we have developed a numerical model of the studied airflow window. An experimental set up was used to validate the numerical model and compare, in real conditions, the studied window performances to the ones of a conventional double-glazed window. These experimental results were complemented by a numerical parametric study for different climatic and operating conditions.The main information from these experimental and numerical studies are that the preheating of the air takes place essentially in the inner air gap, temperature in the first air layer remaining close to the outdoor one. In addition, unlike the temperatures of the inside face and of the blown air, the outer face temperature of the window is not greatly affected by the studied parameters. On the window frame, we found that it also benefits of heat exchanges with the circulating air, but to a lesser extent. This makes the window energy efficient. Finally, by coupling the developed model to a thermal building simulation software, we evaluated the airflow windows integration potential in a house. We thus demonstrated that the heat load is reduced by about 20 to 30% by the use of airflow windows instead of conventional double-glazed windows. Moreover, in summer, when indoor is cooler than outdoor, we pointed out that the airflow window cools the incoming fresh air.

Magister Commercii (Industrial Psychology) - MCom (IPS) / The construction industry plays a crucial role in the South African economy. In this high-risk industry, a lack of engagement by employees can have serious and costly health and safety consequences. Because construction companies work under conditions of tight deadlines and stringent requirements, executives and managers are often unable to reduce the demands on their employees. Hence, if employees are to increase their own levels of work engagement (and so improve health, promote safety, and guard against burnout), they need to exert personal agency by recrafting their own jobs. The term job crafting refers to proactive employee behaviours that seek to optimise the work environment, frequently by addressing the balance between job demands and job resource. Previous literature suggests that employees who use job crafting behaviours show higher work engagement, lower disengagement, more positive emotions, and better adaptive performance.

Les fluides naturels employés en réfrigération et en conditionnement d’air possèdent de faibles PRG et sont de ce fait une véritable alternative aux HFC. Cependant, leur généralisation se heurte à des limites provenant de leur caractère toxique (NH3), inflammable (hydrocarbures, NH3) ou de leurs caractéristiques thermodynamiques défavorables (CO2). Leur utilisation accrue nécessite la mise en œuvre de composants spécifiques (échangeurs de chaleur intermédiaire, éjecteur) qui sans qui les performances seraient inférieures à celles obtenues avec les HFC (COPCO2 = 55 % du COPHFC-134a pour des températures de sources de 0 °C et 40 °C). L’utilisation d’un éjecteur comme organe de détente est une solution envisagée pour réduire les irréversibilités. Les éjecteurs diphasiques constituent une alternative intéressante pour les dispositifs de détente classiques utilisés depuis plusieurs décennies. Le principal avantage de l’éjecteur est de récupérer une partie de l’énergie cinétique du processus de détente de la haute pression à la basse pression pour augmenter la pression d’aspiration du compresseur. Ceci entraîne une diminution du travail consommé par ce dernier et, par suite, une augmentation du coefficient de performance du système. Néanmoins, une bonne conception d’un éjecteur diphasique nécessite une analyse détaillée en termes de simulations numériques et travaux expérimentaux. Ainsi, l’objectif de ce travail est d’apporter une contribution expérimentale à l’étude des machines frigorifiques au CO2 transcritique équipées d’éjecteur diphasique. Des efforts importants ont été investis dans la conception d’un éjecteur diphasique avec diverses géométries pour évaluer les principales caractéristiques à savoir le facteur d’entraînement et le rapport de compression. Les essais effectués ont permis de mettre en évidence l’influence des différents paramètres géométriques sur les performances de la machine (différents diamètres au col des tuyères primaires, différents diamètres de mélangeurs, longueurs de mélangeurs, distance entre le plan de sortie de la tuyère primaire et l’entrée du mélangeur, l’angle de divergent des tuyères primaires…) ainsi que les paramètres thermodynamiques (température d’évaporation, température à l’entrée de la tuyère primaire). / Natural refrigerants used in refrigeration and air conditioning have low GWP and are therefore a real alternative to HFCs. However, their generalization comes up against limits due to their toxic (NH3), flammable (hydrocarbons, NH3) or their unfavorable thermodynamic characteristics (CO2). Their increased use requires the implementation of specific components (intermediate heat exchangers, ejector) which without performance would be lower than those obtained with HFCs (COPCO2 = 55% of COPHFC-134a for temperatures source of 0 °C and 40 °C). The use of an ejector as an expansion device is a solution considered to reduce irreversibility. Two-phase ejector has been an interesting alternative for conventional expansion devices for several decades. The main advantage of the ejector is to recover some of the kinetic energy of the process of expansion from high pressure to low pressure to increase the suction pressure of the compressor. This results in a reduction of the work consumed by the latter and, consequently, an increase in the coefficient of performance of the system. Nevertheless, a good design of a two-phase ejector requires a detailed analysis in terms of numerical simulations and experimental work. Thus, the objective of this work is to make an experimental contribution to the study of transcritical CO2refrigeration machines equipped with two-phase ejector. Significant efforts have been invested in the design of a two-phase ejector with various geometries to evaluate the main characteristics namely the entrainment ratio and the compression ratio. The tests carried out made it possible to highlight the influence of the various geometrical parameters on the performances of the machine (different diameters of the throat of the primary nozzle, different mixers diameters and lengths, distance between the exit of the primary nozzle and the inlet of the mixer, the divergence angle of the primary nozzles ...) as well as the thermodynamic parameters (evaporation temperature, temperature at the inlet of the primary nozzle).

Cette thèse est dédiée à l'étude expérimentale et numérique des phénomènes de condensation dans un pressuriseur de chaufferie nucléaire embarquée conçu par l'entreprise DCNS. Au sein du système est observé un écoulement diphasique avec changement d'état, descendant dans un tube vertical partiellement immergé dans du liquide. Le liquide sous-refroidi s'écoule dans le tube sous l'effet de la gravité en entrainant de la vapeur saturée qui se condense à son contact. Dans un premier temps, l'étude des phénomènes de condensation est réalisée sur un banc expérimental dont la conception, le dimensionnement, la réalisation et l'exploitation ont été effectués au cours de cette thèse. Le dispositif est une version simplifiée à l'échelle 1 du système réel. Cette étude expérimentale a permis d'identifier les régimes d'écoulements diphasiques présents dans le système et d'analyser l'impact de trois paramètres : le débit de liquide injecté, le sous-refroidissement de ce liquide à l'entrée du tube et la pression en sortie de tube. Par ailleurs, l'étude propose un modèle déterminant les conditions pour laquelle le tube d'essais est complètement noyé, ce qui minimise les phénomènes de condensation. Dans un second temps, une simulation numérique de l'écoulement diphasique est réalisée par CFD sur ANSYS Fluent à l'aide du modèle " Volume Of Fluid ". La prise en compte de la condensation de la vapeur au contact du liquide sous-refroidi a nécessité le développement, grâce aux fonctions utilisateur du logiciel, d'un modèle spécifique s'appuyant sur un modèle de la littérature. Les résultats obtenus ont permis de reproduire qualitativement le déversement du liquide observé expérimentalement en entrée de tube ainsi que la condensation de la phase vapeur au contact de la phase liquide. / This thesis focuses on condensation phenomena occurring in a patented system designed by DCNS Company. The system ensures pressure regulation of nuclear boiler rooms embarked in naval vessels. Within the system occurs a downward liquid/vapor flow with phase change in a partially submerged vertical pipe. Subcooled liquid flows into the pipe and induce a suction of saturated vapor which condense in contact with liquid phase. This study aim to understand the physical phenomena occurring in the system and to simulate these phenomena. First, the condensation phenomena are studied with a test loop which conception, dimensioning, realization and exploitation were realized during this study. The experimental study identified the flow regimes occurring in the system and analyzed the impact of three parameters: the liquid flow rate, the liquid subcooling and the pressure at the system outlet. This study also proposed a simple model which determine the necessary conditions to completely drown the pipe, which minimize condensation phenomena. Thereafter, the numerical simulation of the two-phase flow was realized by CFD on ANSYS Fluent with the "Volume of Fluid" model. The condensation simulation was achieved by applying a condensation model used in literature. This model was added to the numerical code with User-Defined Functions (UDF). The simulation reproduced the weir regime flow at the pipe entrance and the vapor condensation inside the pipe.