Submitted by Dilene Paulo (dilene.fatima@ufcg.edu.br) on 2018-04-13T15:41:27Z No. of bitstreams: 1 RIVANA MABEL LUCENA OLIVEIRA - DISSERTAÇÃO (PPGEQ) 2017.pdf: 1154206 bytes, checksum: 45fbf5b56861974e34403f5a5215119d (MD5) / Made available in DSpace on 2018-04-13T15:41:27Z (GMT). No. of bitstreams: 1 RIVANA MABEL LUCENA OLIVEIRA - DISSERTAÇÃO (PPGEQ) 2017.pdf: 1154206 bytes, checksum: 45fbf5b56861974e34403f5a5215119d (MD5) Previous issue date: 2017 / Capes / Sequências de destilação extrativa têm recebido uma atenção especial dos pesquisadores devido ao alto consumo energético e à baixa eficiência termodinâmica associados a esse processo. A eficiência termodinâmica vem sendo abordada de forma bastante simplificada pela literatura, e neste trabalho, este termo foi abordado intrinsecamente, de modo que o sentido físico dos termos: trabalho mínimo, trabalho equivalente, trabalho perdido e produção de entropia, relacionados à eficiência, foram discutidos do ponto de vista físico e matemático. Técnicas de intensificação vem recebendo destaque no que se refere a redução do consumo energético e custos de processos de destilação, e a integração térmica surge como alternativa para reduzir o consumo energético de processos de destilação. As sequências de destilação extrativa convencional sem e com integração térmica foram abordadas neste trabalho dos pontos de vista ótimo econômico, termodinâmico e energético, utilizando o parâmetro teor de solvente como principal parâmetro de análise. Além do alto consumo energético e baixa eficiência termodinâmica, os processos de destilação extrativa incluem ainda uma fonte de irreversibilidade que é relatado como responsável pela baixa eficiência termodinâmica desses processos, e este foi outro ponto de análise para os fluxogramas abordados. Os estudos de caso foram as misturas azeotrópicas etanol-água e acetona-metanol utilizando etileno glicol e água, como solventes, respectivamente. Usando o procedimento proposto, as sequências com e sem integração térmica foram analisadas considerando o sistema como um todo, para os termos econômicos e termodinâmicos, e, cada coluna (extrativa e de recuperação) em separado para termos termodinâmicos, além da avaliação do efeito remixing. Os resultados mostram que a configuração com integração térmica não só é termodinamicamente mais eficiente quando comparada a configuração sem integração, como também apresentou menores valores de TAC e consumo energético, mesmo quando valores negativos para eficiência termodinâmica são encontrados, e que os termos termodinâmicos devem ser comparados para casos que envolvem a separação da mesma mistura. / Extractive distillation sequences have received special attention from researchers due to the high energy consumption and the low thermodynamic efficiency associated to this process. The thermodynamic efficiency has been simplified in the literature, but in this work it was approached intrinsically, thus the physical meaning of the terms related to efficiency like minimum work, work equivalent, lost work and entropy production were discussed from a physical and mathematical point of view. Process intensification alternatives have been highlighted in the reduction of energy consumption and costs in the distillation processes. Likewise, thermal integration is an alternative to reduce the energy consumption of distillation processes. The conventional extractive distillation sequences with and without thermal integration were approached in this work. They were analyzed from the economic, thermodynamic and energy optimum points of view and the main parameter of analysis was the solvent content. In addition to the high energy consumption and low thermodynamic efficiency, the extractive distillation also include a irreversibility that is reported as responsible for the low thermodynamic efficiency of this process, and this was another point of analysis on the flowcharts studied. The study cases were the azeotropic mixtures formed from ethanol-water and acetone-methanol using ethylene glycol and water as solvents, respectively. The sequences with and without thermal integration were studied considering the proposed procedure and the whole system was analyzed for the economic and thermodynamic terms, also each column (extractive and recovery columns) was separately analyzed for thermodynamic terms, besides the evaluation of the remixing effect. The results show that the configuration with thermal integration is thermodynamically more efficient when compared to the non-integration configuration, moreover the configuration with thermal integration presented lower values of TAC and energy consumption, even when negative values for thermodynamic efficiency are found, and that the thermodynamic terms must be compared to cases involving the separation of the same mixture.

L'objectif de la thèse était d'étudier la faisabilité d'un couplage thermique entre un réservoir d'hydrure métallique et une source externe de chaleur. L'évolution des propriétés de composites à base d'hydrure de magnésium (MgH2) a été étudiée en fonction du nombre de cycles d'hydruration. On observe une très bonne stabilité de la capacité massique d'absorption sur le long terme (600 cycles réalisés). Les premiers cycles sont néanmoins marqués par une évolution importante de la microstructure qui dépend de la proportion et/ou de la nature de l'additif utilisé lors de la mécano-synthèse des poudre d'hydrure. Cette évolution est associée à une augmentation de la conductivité thermique, mais également à une légère dégradation des cinétiques intrinsèques de réaction ainsi qu'à une expansion volumique des composites. Nos mesures montrent que l'amplitude des contraintes mécaniques engendrées sur les parois d'un réservoir se stabilisent après une cinquantaine de cycles. Un réservoir contenant 10 kg de MgH2, et capable de stocker 6500 Nl d'hydrogène en 35 minutes a ensuite été développé au laboratoire. L'énergie des réactions d'absorption et de désorption est échangée avec une source externe de chaleur via un fluide caloporteur. Ce système permet de représenter l'intégration thermique d'un réservoir d'hydrure dans un système de cogénération. Un modèle numérique a été développé afin de mieux appréhender le comportement de ce réservoir. Des essais de couplage entre un réservoir de taille plus modeste et une pile à combustible haute température (SOFC) développant une puissance électrique de 1 kW ont également été réalisés au Politecnico di Torino. / The main target of the thesis was to study the thermal integration of a magnesium hydride (MgH2) tank with an external heat source. At first, the evolution of material properties upon cycling were investigated. A large microstructural evolution was observed during the first cycles which impacts on kinetics of reaction and thermal conductivity. An expansion of the composites is also observed. Quantity and/or nature of the additives used during material preparation was identified as an important parameter controlling this phenomenon. Our measures show that mechanical strains on the tank wall due to this expension are stable after 40 hydrogenation cycles. A large number of cycles was applied to these composites which exhibits a very high stability upon cycling. A large scale magnesium hydride tank (10 kg MgH2) storing 6500 Nl of hydrogen in 35 minutes was developed and tested. The energy of reaction is exchanged with an external heat source by a heat transfer fluid. This installation allows to simulate the integration of a magnesium hydride tank into a co-generation system. A numerical model was developed in order to better understand and predict the behavior of this tank. A thermal integration test of the MgH2 with a high temperature fuel cell (SOFC) was performed at Politecnico di Torino.

Orientadores: Silvia Azucena Nebra de Perez, Luis Maria Serra de Renobales / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-10T13:07:28Z (GMT). No. of bitstreams: 1 Ensinas_AdrianoViana_D.pdf: 2176503 bytes, checksum: 487cb2d8e92c4896c8970468350b80cc (MD5) Previous issue date: 2008 / Resumo: A produção de açúcar e etanol a partir da cana-de-açúcar no Brasil compõe um dos setores mais importantes da economia nacional e tem se caracterizado, ao longo de sua história, pelo alto consumo de energia no processo industrial. O uso do bagaço de cana como combustível para o sistema de cogeração permite que as usinas sejam auto-suficientes em energia térmica e elétrica, ainda que utilizem sistemas de baixa eficiência. Uma nova realidade, que prevê a venda de eletricidade excedente nas usinas e o uso do bagaço como matéria prima para outros processos, tem levado o setor a investir em redução do consumo de energia no processo. Este estudo propõe um método de integração térmica para o produção de açúcar e etanol, visando obter uma redução da demanda de utilidades quentes e frias. Um procedimento de otimização termoeconômica foi também aplicado para avaliar a redução de custo no projeto de integração da planta, que inclui uma rede de trocadores de calor e um sistema de evaporação. As análises mostraram que a integração pode proporcionar aumentos significativos na produção de excedentes de eletricidade e/ou bagaço de cana, além de reduzir a demanda de água da usina. Uma análise exergética foi realizada, avaliando as melhorias obtidas com a integração, mostrando que a geração de irreversibilidade pode ser minimizada com a redução do consumo de energia no processo e aumento da eficiência do sistema de cogeração / Abstract: The sugar and ethanol production from sugarcane in Brazil constitutes one of the most import sectors of the national economy and has been characterized, during its history, by high energy consumption in the industrial process. The use of the bagasse as fuel for the cogeneration system permits mills to be self-sufficient in thermal and electric energy requirements, even using low efficient systems. A new reality, which foreseen sell of surplus electricity by the mills or the use of bagasse as raw material for other processes, has encouraged this sector to invest in process energy consumption reduction. This study proposes a method for thermal integration of sugar and ethanol process, aiming at the reduction of hot and cold utilities requirements. An thermoeconomic optimization procedure was also applied for the evaluation of cost reduction in the plant integration design, which includes the heat exchangers network and the evaporation system. The analysis showed that the process integration may promote a significant increase in the production of surplus of electricity and/or bagasse, reducing also the water demand of the mills. An exergetic analysis was performed, evaluating the improvements obtained with the thermal integration, showing that the irreversibility generation can be minimized with reduction of process energy consumption and increase of the cogeneration systems efficiency / Doutorado / Termica e Fluidos / Doutor em Engenharia Mecânica

Dans l'industrie agroalimentaire, le procédé de blanchiment est un traitement thermique indispensable pour la transformation de légumes en produits conserves et surgelés. L'objectif est de détruire des microorganismes par un chauffage des légumes à 97°C, puis de les refroidir à 5°C. L'enjeu de cette thèse est de proposer une conception énergétiquement efficace de ce procédé. L'analyse énergétique et exergétique, ainsi que le respect de contraintes qualité liées au produit, aboutissent à un nouveau schéma de procédé. L'essentiel de la récupération de chaleur est réalisée grâce à un débit d'eau circulant à contre-courant des légumes au travers de trois échangeurs de chaleur. Le complément de puissance est fourni par une thermo-frigo-pompe (TFP) délivrant les utilités chaude et froide. Le premier enjeu est le bon dimensionnement des échangeurs liquide/solides. Ceux-ci sont modélisés pour deux configurations d'écoulement : courant-croisé et contre-courant. D'autre part, une TFP usuelle n'est pas capable d'avoir la flexibilité nécessaire à son intégration dans un procédé agroalimentaire soumis à des besoins de puissance variables. Deux options de découplage (total et partiel) sont étudiées pour ajouter un degré de liberté à ce cycle thermodynamique. Ces travaux permettent la conception d'un pilote qui est réalisé pour blanchir 1 t/h de légumes. L'équipement a démontré une réduction des besoins de puissance de chauffage de 65 % à 75 %. La consommation exergétique, combinant les besoins de chauffage et de refroidissement, a chuté de 79 % et le débit d'eau consommée est divisé par 5. Si ces travaux posent de nouvelles questions, ils démontrent que la récupération de chaleur sur des solides tels que des légumes est réalisable. / In food industry, the blanching process is essential for transforming vegetables into canned or frozen products. To destroy microorganisms the vegetables are heated to 97 °C and cooled to 5 °C. The aim of this thesis is to propose an energy-efficient design of this process. Energy and exergy analysis, coupled to respect of safety requirements, resulted in a new process flow sheet. The largest part of heat is recovered using an intermediate water flow which circulates in counter-current of the solid flow rate. Remaining cooling and heating needs are provided by a heat pump. Thus, designing the liquid-to-solids heat exchangers is the first challenge. To do this, two mains components are modeled: the countercurrent and the crossflow heat exchangers. On the over hand, a usual heat pump is unable to deliver both heating and cooling with variable capacities. To improve flexibility of this thermodynamic system two different options are analyzed. Theses works lead to a new blanching process design, the pilot was made to operate with a solid mass flow rate of 1 t/h. This equipment demonstrates an energy saving of 65 % to 75 % and an exergy saving of 79 %. Moreover water consumption is divided by 5. If this work leads to new questions, it proves that energy efficiency if feasible on solids like vegetables.

Airbus réalise pour chaque avion et pour chaque équipement de nombreux essais, au sol ou en vol et doit garantir qu'en tout point de vol possible, la température de chacun des équipements reste inférieure à la température limite correspondante. Pour pouvoir valider la température de chaque équipement dans l'enveloppe de vol, il faudrait disposer d'essais réalisés aux frontières. Or, tous les essais en vol sont confrontés aux contraintes climatiques et opérationnelles qui ne permettent pas d'explorer tout le domaine. C'est pourquoi Airbus a besoin d'élaborer des méthodes d'extrapolation de température, de manière à prédire le comportement thermique des matériaux et des équipements dans les pires conditions. Les techniques proposées sont basées sur la théorie de l'identification de systèmes qui consiste à déterminer des modèles de comportement d'un point de vue heuristique à partir de mesures et considérations physiques. Plus précisément, le présent document valide les modèles ARX comme un outil pour l'identification de la température du système. Les modèles et les techniques sont étudiés, tout d'abord, d'un point de vue de la simulation numérique et après, confrontés face à des tests représentatifs au laboratoire. Les techniques proposées permettent prédire la température des composants avion pour des conditions différentes / Airbus must ensure that for all flight conditions that a given aircraft could face, the temperature of each powerplant system must be less than the corresponding critical temperature. In order to validate the temperature of each device in the flight envelope, tests at the border should be done. Airbus produces for each aircraft component many trials, either in flight or ground. However, all flight tests are faced with climatic and operational constraints which do not permit exploring the whole area. That's why Airbus needs to develop methods of extrapolation of temperature in order to predict the thermal behavior of materials and equipments in the worst conditions. The proposed techniques are based on the system identification theory which consists on heuristically determining an analytical model using physical insights and measurements. More precisely, this paper validates ARX models as a tool for the identification of the system's temperature. The models and techniques are studied, first, from a numerical simulation point of view and second, based on laboratory representative tests. The proposed techniques allow predicting the temperature of aircraft components at different conditions