Os óleos essenciais cítricos possuem uma ampla variedade de aplicações em diversos ramos das indústrias químicas, farmacêuticas, de alimentos, entre outras. Na indústria de cosméticos, mais precisamente no ramo de perfumaria, os ativos naturais cítricos (provenientes dos óleos de bergamota, limão, lima, mandarina, laranja, etc) são empregados nas formulações de colônias, cremes hidratantes e loções. Além disso, estes compostos são largamente utilizados como agentes aromatizantes nas indústrias alimentícias e farmacêuticas e empregados como matéria-prima para as indústrias de aromas. Com o objetivo de melhorar a qualidade dos óleos essenciais e sua capacidade aromatizante, alguns processos têm sido desenvolvidos para enriquecer a mistura com compostos oxigenados, os quais são reportados como os principais responsáveis pelo aroma característico da fruta. Tal processo é comumente conhecido como desterpenação e consiste na concentração destes compostos pela retirada de hidrocarbonetos terpênicos do óleo e pode ser realizado por meio da extração líquida ou extração por solvente. Neste contexto, esta dissertação de mestrado teve como finalidade estudar da viabilidade técnica do processo de desterpenação de óleo essencial cítrico modelo composto por limoneno e linalol. Os experimentos foram conduzidos em coluna de discos rotativos perfurados (PRDC) sob condição de temperatura controlada e pressão ambiente local. O equipamento operou de modo contínuo e contracorrente, utilizado como solventes soluções de etanol com teores de água de 30 e 40% (em massa), velocidade de rotação dos discos de 150, 200 e 250 rpm e razão entre a vazão mássica de solvente e alimentação de 0,5; 1,25; 2,5 e 3,0. Avaliou-se, também, o comportamento da densidade e viscosidade das fases extrato e rafinado oriundas da coluna de extração. Através deste estudo foi possível verificar que a tecnologia de desterpenação de óleos essenciais por meio da extração líquido-líquido é viável podendo ser aplicada à processos contínuos utilizando equipamento PRDC, por exemplo, sendo possível a obtenção de frações enriquecidas do composto oxigenado (linalol). / Citrus essential oils are used in a wide variety of applications in various branches of the chemical, pharmaceutical, food and other industries. In the cosmetics industry, specifically in the field of perfumery, natural citrus assets (from the essential oils of bergamot, lemon, lime, mandarin, orange, etc.) are used in the formulations of colonies, moisturizing creams and lotions. Furthermore, these compounds are widely used as flavoring agents in food and pharmaceutical industries and as raw material for the flavor industry. With the aim to improve the quality of essential oils and its flavoring ability, some processes have been developed to enrich the mixture with oxygenated compounds, which are reported as the main responsible for the characteristic aroma of the fruit. Such process is commonly known as deterpenation, and consists in concentration of these compounds by the removal of terpene compounds from the essencial oil and can be performed by liquid or solvent extraction. In this context, the purpose of this dissertation of master\'s degree was to carry out a study of the technical feasibility of deterpenation process of a citrus essential oil model composed by a mixture of limonene and linalool. The experiments of deterpenation were conducted in a perforated rotating discs contactor (PRDC) under controlled conditions of temperature and local environment al pressure. The equipment was operated in continuously and countercurrently mode, using as solvents ethanol solutions with 30 and 40% of water contents (by mass), rotation of discs speed of 150, 200 and 250 rpm and the mass flow rate of the solvent and feed ratio of 0.5, 1.25, 2.5 and 3.0. The behavior of the density and viscosity of the extract and raffinate phases from the extraction column was also evaluated. It was found that the deterpenation of essential oils by liquid-liquid extraction technology is feasible and can be applied to continuous processes using PRDC column extraction type, for instance, being possible to obtain enriched fractions of oxygenated compounds (linalool).

Este trabalho trata de um estudo experimental da transferência de calor e de massa de um condensador evaporativo, bem como, da relação existente entre as grandezas envolvidas durante a sua operação. Para o desenvolvimento da pesquisa foi construído um condensador evaporativo de pequeno porte com dimensões proporcionais a condensadores comercialmente fabricados no Brasil para operar com R-22 como fluido refrigerante. Este condensador tem 35 colunas e 12 fileiras de tubos de cobre de 6,35 mm de externo e opera junto a uma instalação que proporciona o escoamento de R-22 por termossifao. O distribuidor de água também foi construído em cobre e o eliminador de gotas em alumínio, assim como a estrutura do condensador. As laterais e a bandeja de recolhimento de água foram construídas em vidro para permitir a visualização do escoamento da água que e aspergida sobre os tubos. A fim de variar as condições operacionais, este condensador foi acoplado a um ventilador centrifugo acionado por um conversor de freqüência e a um circuito que permitiu a variação da vazão de água aspergida sobre os tubos. Dos ensaios resultaram 79 amostras de medição, que serviram para verificar a relação existente entre grandezas, bem como avaliar os coeficientes de transferência de calor e massa. Foram determinados os coeficientes de transferência de calor médio e local para o R-22. Alem disso, foram verificadas as regiões onde ocorrem o dessuperaquecimento, a mudança de fase e o subresfriamento do fluido refrigerante, e foram confrontados os coeficientes globais de transferência de calor obtidos a partir dos dados experimentais com aqueles obtidos por correlações para as regiões de condensação e subresfriamento. Destas investigações, resultou uma correlação para o coeficiente global de transferência de calor que visa determinar esta grandeza através das condições operacionais e das características geométricas do condensador. O Maximo desvio encontrado entre os valores provenientes dos dados experimentais e aqueles calculados pela correlação foi inferior a 10%. / This work presents an experimental heat and mass transfer study of an evaporative condenser, as well as, the relationship between measured quantities obtained during its operation. A small scale evaporative condenser was built in agreement to the real size equipment geometric similarity. The small scale condenser has a bundle of 210 copper tubes, with the outer diameter equal to ¼ inch, which were arranged in 35 columns and 6 rows and operating connected to the thermosifon facility that promote R-22 flow. The spray water distributor is also built on copper and the drift eliminator on aluminum, as well as the evaporative condenser structure. This condenser bounds were constructed as a glass enclosure to allow for the spray water flow visualization. To evaluate the operational conditions, the equipment was attached to a centrifugal fan controlled by a frequency inverter and a spray water circuit which allows for water quantity changing. From the carried out tests, 79 measuring samples were obtained and used to verify the quantities relationship, as well as, to evaluate the heat and mass transfer coefficients For the R-22 were determined the local and average heat transfer coefficients. Furthermore, the dessuperheating, condensation and subcooling regions were verified and compared both, the experimental overall heat transfer coefficient and those calculated by correlations at condensation and subcooling zones. From these investigations a correlation for the overall heat transfer coefficient is proposed. Its application allows determining the coefficient using the operational conditions and the geometric condenser features. The higher deviation found between the experimental data and the presented correlation is lower to 10%.

Associações entre fungos micorrízicos arbusculares e plantas hospedeiras podem transferir césio (137Cs) para o vegetal. A mobilidade do césio (Cs+) nos solos e sua similaridade química com o potássio (K+) constituem a principal ameaça à contaminação da vegetação pelo radionuclídeo. Foi realizado experimento com plantas de feijão (Phaseolus vulgaris L.) variedade Iapar Tangará, com o objetivo de avaliar o coeficiente de transferência direta do 137Cs do solo para a planta, a absorção, o transporte e o acúmulo do radionuclídeo 137Cs nas folhas, caule e raízes das plantas, a produção de massa seca do feijoeiro, o diâmetro do caule das plantas, a peroxidação lipídica, avaliar as enzimas do sistema antioxidativo (catalase, ascorbato peroxidase, glutationa redutase e superóxido dismutase), o teor de clorofila em unidade SPAD, em função dos efeitos da: (I) inoculação ou não com fungos micorrízicos arbusculares (FMA) e (II) do nível de potássio em quatro tipos de solos: Nitossolo, Chernossolo, Argissolo e Gleissolo. O delineamento experimental foi o de blocos completos ao acaso, utilizando esquema fatorial de quatro tipos de solo x dois níveis de potássio x presença e ausência de micorrizas com três repetições, totalizando 48 unidades experimentais. Foi calculada a atividade específica do 137Cs no solo e na planta e, por fim, a determinação do coeficiente de transferência direta do 137Cs do solo para o vegetal. Nas plantas cultivadas em Argissolo, Chernossolo e Gleissolo, foi observada maior atividade específica de 137Cs nas raízes do feijão em relação às folhas e ao caule, na condição de baixo nível de potássio e ausência de inoculação de FMA. O coeficiente de transferência solo-planta do 137Cs e a atividade na planta foram maiores no Argissolo e Nitossolo, com baixo teor de potássio e sem a presença de FMA. Constatou-se interação entre os tipos de solo, teor de K e presença de FMA quanto à peroxidação de lipídeos, sendo que houve maior dano nas folhas das plantas cultivadas no Chernossolo, principalmente no tratamento sem aplicação de FMA e com baixo teor de K. Não foi observada interação entre os solos e a inoculação com FMA para a quantificação de peróxido de hidrogênio (H2O2) nas folhas, todavia, constatou-se efeito para os teores de K no solo. Quanto ao sistema enzimático antioxidativo, a atividade da catalase, glutationa redutase, ascorbato peroxidase e superóxido dismutase houve interação entre os tipos de solo, níveis de K e presença ou ausência de FMA. Maior atividade da superóxido dismutase (SOD) foi demonstrada nas plantas cultivadas no Argissolo, sem a presença de FMA, também independente dos teores de K. O aumento nos teores de K nos solos não impediu a transferência direta de 137Cs do solo para as plantas, porém, reduziu a absorção do nuclídeo pelo feijoeiro. O tipo de solo influenciou na disponibilidade de 137Cs às plantas de feijão e por sua vez, nas atividades das enzimas do sistema de defesa da planta. A inoculação com os FMA não foi efetiva para evitar a transferência e a absorção de 137Cs pelas plantas / Associations between arbuscular mycorrhizal fungi (AMF) and host plants might transfer cesium (137Cs) for the plant. The mobility of cesium (Cs+) in soils and their chemical similarity to potassium (K+) are the main threat to contamination of vegetation by radionuclide. Experiment with common bean (Phaseolus vulgaris L.) variety Iapar Tangara was conducted with the objective of evaluating the coefficient of direct transfer of 137Cs from soil to the plant, absorption, transport and accumulation of the radionuclide 137Cs in the leaves, stem and plant roots, the dry mass of bean stem diameter of plants, lipid peroxidation, evaluate the antioxidant system enzymes (catalase, ascorbate peroxidase, glutathione reductase and superoxide dismutase), the content of chlorophyll SPAD unit, due to the effects of: (I) or without inoculation with mycorrhizal fungi (AMF) and (II) the level of potassium in four types of soil: Nitosol Chernosol, Alfisol and Ultisol. The experimental design was a randomized complete block, factorial design using four soil types x two levels of potassium x presence and absence of mycorrhizae with three replications, totaling 48 experimental units. The specific activity of 137Cs in soil and plant and finally, the coefficient of 137Cs direct transfer from soil to plant was calculated. In plants grown in Alfisol and Ultisol Chernosol, higher specific activity of 137Cs in bean roots compared to the leaves and the stem was observed under the condition of low potassium and absence of AMF inoculation. The coefficient of soil-plant transfer of 137Cs activity and yield were higher in the Ultisol and Alfisol with low potassium and without the presence of AMF. Found an interaction between soil types, K content and the presence of AMF as to lipid peroxidation, and there was more damage on the leaves of plants grown at Chernosol, primarily in the treatment without application of AMF and low in K. No interaction between soil and AMF inoculation for quantification of hydrogen peroxide (H2O2) in the leaves was observed, however, it was found to effect the K in the soil. As for the antioxidant enzyme system, the activity of catalase, glutathione reductase, ascorbate peroxidase and superoxide dismutase was no interaction between soil types, levels of K and the presence or absence of AMF. Increased activity of superoxide dismutase (SOD) has been demonstrated in plants grown in Ultisol without the presence of AMF, independent of the levels of K. The increase of K in the soil did not prevent the direct transfer of 137Cs from soil to plants, however, reduced the uptake of the nuclide by bean. Soil type influenced the availability of 137Cs to bean plants and in turn, the enzyme activities of the plant defense system. Inoculation with AMF was not effective to prevent the transfer and uptake of 137Cs by plants

Dans les centrales nucléaires à eau sous pression, les Résines Echangeuses d'Ions (REI) sont utilisées dans les circuits d'épuration. Dans le cadre de cette thèse, une étude qualitative a été réalisée afin de prédire les tendances du comportement d'une REI dans le cadre de son utilisation en condition centrale nucléaire. Fort des résultats de cette étude, nous avons cherché à caractériser quantitativement le comportement des REI en colonne. Pour cela, nous avons utilisé des solutions analytiques mais ces dernières se sont révélées valables uniquement dans des cas particuliers. Afin de trouver une solution générale, nous nous sommes donc tournés vers une solution numérique : OPTIPUR. En vue de la valider et aussi de mieux comprendre la cinétique en colonne, nous avons réalisé une étude expérimentale. Cette dernière vise à caractériser la résistance au transfert de masse en colonne et à mener une étude de sensibilité sur les paramètres influençant ce phénomène. Cette étude repose sur la détermination de la fuite ionique cinétique, correspondant à une certaine concentration de polluant présente en sortie de colonne en début d'expérience. Pour cela, nous avons testé l'influence de nombreux paramètres sur la fuite ionique cinétique. Nous avons ainsi vu l'importance de la vitesse de filtre et donc des conditions hydrodynamiques sur la fuite ionique cinétique. Ces nombreux résultats de fuite cinétique, ont été modélisés à l'aide de la corrélation empirique de Dwivedi & Upadhyay afin de tester sa validité. Par la suite, nous avons simulé nos résultats de fuite ionique cinétique avec deux options du logiciel OPTIPUR : option Mass Transfer Coefficient (MTC) et Nernst-Planck (NP). Ces dernières encadrent les résultats expérimentaux. L'option MTC d'OPTIPUR donne des résultats inférieurs alors que ceux obtenus avec l'option NP sont supérieurs aux résultats expérimentaux. Nous avons vu que dans le cadre d'un échange ternaire, seule l'option NP est valide. Nous avons proposé des solutions pour mieux caler les résultats obtenus numériquement. D'autres simulations ont été réalisées afin de vérifier les capacités de prédiction de l'appareil pour des expériences plus longues (allant jusqu'à la saturation de la REI). Les tendances observées étaient celles attendues. L'outil OPTIPUR est un outil précis et robuste pour étudier la cinétique en colonne. / In pressurized water reactor, ion exchange resins (IER) are used in systems purification. In this thesis, a qualitative study has been performed to predict the behavior of IER while used in nuclear plants conditions. Then, we searched to characterize the IER behavior in column through a quantitative study using analytical solutions. But these solutions worked only for particular cases. In order to find a general solution, we used a new numerical solution: OPTIPUR. To validate this general solution and get a better understanding of the kinetic in column, we performed an experimental study to characterize the resistance to mass transfer in column and to study the sensibility on the parameters influencing this phenomenon. This study is based on the characterization of the initial leakage (initial pollutant concentration at the column outlet). We tested numerous parameters on the initial leakage. We understood the importance of the superficial velocity and indeed of the hydrodynamic conditions on the initial leakage. These numerous results about initial leakage were modeled with an empirical correlation of Dwivedi and Upadhyay in order to validate it. Then, we modeled our results with the two options of OPTIPUR software: option Mass Transfer Coefficient (MTC) and Nernst-Planck (NP). These options encircle experimental results. The MTC option of OPTIPUR gives lower results while those obtained with the NP option are higher than the experimental results. We observed also that only the NP option was valid for a ternary exchange. We proposed solutions to get a better fit with the results obtained with OPTIPUR. We performed other simulations to check the prediction abilities of the software for longer experiments (until the IER saturation). The tendencies were those expected. The OPTIPUR software showed is accuracy and robustness to study column kinetic.

Carbon dioxide (CO2) is a natural, low cost refrigerant with good thermo-physical properties. CO2 is a good alternative for replacing HFC refrigerants that possess high global warming potential and reducing the direct impacts of refrigeration systems on the environment. However, CO2 refrigeration systems operate at relatively high condenser/gas cooler pressures and this imposes special design and control considerations. The gas cooler is a very important part of the system and can have significant influence on its performance. In sub-critical operation, good gas cooler/condenser design can reduce the condenser pressure and delay switching to supercritical operation which increases system efficiency. In supercritical operation optimum design and control can enable the system to operate at pressures that maximise system efficiency. In air cooled systems, gas coolers/condensers are of the finned-tube type. This type of heat exchanger is well established in the HVAC and refrigeration industries. The large changes in the CO2 properties in the gas cooler, however, during supercritical operation impose special design and manufacturing considerations. This research project considered the influence of the unique heat transfer characteristics of CO2 on the design and performance of finned tube air cooled condensers/gas coolers for CO2 refrigeration applications. A combined experimental and modelling approach using Computational Fluid Dynamics (CFD) was employed. A CO2 condenser/gas cooler test facility was developed for the experimental investigations. The facility employs a ‘booster’ hot gas bypass CO2 refrigeration system, with associated condenser/gas cooler test rig and evaporator load simulation facility. A series of experimental tests were carried out with two gas coolers which incorporated horizontal and horizontal-vertical slit fins and was obtained adequate experimental data concerning gas cooler performance. CFD modelling was used to study the performance of the gas coolers. The model was validated against test results and was shown to predict the air outlet temperature and heat rejection of the gas cooler with an accuracy of within ±5%. The model was subsequently used to evaluate the effect of a fin slit between the 1st and 2nd row of tubes of the gas cooler as well as a vertical slit on the 1st row before the last tube of the section. The results showed a 6%-8% increase in the heat rejection rate of the gas cooler compared to the performance without the horizontal slit. The vertical slit in the fin of the last tube has resulted in an additional increase in heat rejection over and above that for the horizontal slit of 1%-2%. CFD modelling was also used to investigate the variation of the refrigerant side, air side and overall heat transfer coefficient along the heat exchanger. The results showed that the refrigerant heat transfer coefficient increases with the decreasing of bulk refrigerant temperature and reaches its maximum when the specific heat of the refrigerant is highest. Furthermore, increasing the refrigerant mass flux, increases the refrigerant side heat transfer coefficient and heat rejection. This can reduce the size of the gas cooler for a given capacity at the expense of higher pressure drop and compressor power consumption. Air side and overall heat transfer coefficient correlations were developed for the specific gas cooler designs which were investigated and showed the heat transfer coefficients increase with increasing Reynolds Number.

Orientador: Ana Maria Frattini Fileti / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-27T02:40:23Z (GMT). No. of bitstreams: 1 Camargo_StellaForganesdeGodoy_M.pdf: 2742507 bytes, checksum: a2cd6bf18b9859966ac846d9d5939a21 (MD5) Previous issue date: 2015 / Resumo: O processo de polimerização em emulsão é um processo industrialmente importante para a produção de polímeros com diversos tipos de aplicações. Existe um grande interesse industrial para a obtenção de teor de sólidos mais altos, pois assim otimiza-se o volume do reator para o mesmo tempo de reação, reduz-se espaço de armazenagem do produto acabado bem como custos com transporte ao consumidor final. Porém, para obtenção de polímeros com alta concentração de sólidos, a dificuldade de estabilização da emulsão, viscosidade mais alta e formação de resíduos (coágulos) geram limitações no processo, interferindo na segurança da reação. Para este trabalho foi escolhida a copolimerização em emulsão de estireno-butadieno devido à sua importância industrial bem como às propriedades relevantes para aspectos de segurança industrial. O objetivo foi estudar as influências do aumento de teor de sólidos nas propriedades da emulsão estireno-butadieno em processo semi-contínuo que afetam a segurança da reação. Primeiramente foi encontrado na literatura um modelo já validado para a copolimerização em emulsão estireno-butadieno em processo semi-contínuo como base para realizar as simulações nos software Aspen Polymers® para as análises das propriedades e comportamento exotérmico da emulsão. O teor de sólidos na emulsão estireno-butadieno foi aumentado, reduzindo gradativamente a água da formulação e mantendo a proporcionalidade entre as demais matérias-primas variando dos originais 48,4 % para 65,1 % em que toda a água da pré-emulsão foi eliminada. As propriedades finais da emulsão apresentaram resultados esperados conforme embasamento teórico abordado: a massa específica, a viscosidade, massa molar média e diâmetro de partícula aumentaram com o aumento do teor de sólidos e a polidispersidade, a temperatura de transição vítrea, o calor específico e a condutividade térmica diminuíram. A taxa de remoção de calor da reação e a temperatura da reação sob condições adiabáticas em possíveis cenários de descontrole de reação foram consideradas para a segurança do processo aumentando significativamente com o aumento do teor de sólidos e indicando presença de monômeros não reagidos ao final do tempo de reação de 10 horas. A análise de sensibilidade do modelo foi realizada variando a temperatura do processo em diferentes concentrações de produto final com o intuito de aumentar o rendimento da reação. Para cada alteração realizada, as variações das propriedades do produto foram analisadas em detalhe para verificar modificações no produto final. O melhor ponto de trabalho encontrado no estudo foi à concentração de 60 % à temperatura de reação de 78°C em que os resultados demonstraram que pequenas alterações no processo podem ser suficientes para garantir a segurança do processo, a qualidade do produto final com altos rendimentos / Abstract: The emulsion polymerization process is a very important process to the industry in the production of polymers with a wide range of applications. There is a large industrial interest to obtain higher solid content polymers in order to optimize the reactor capacity with the same time of reaction, reducing the storage area and transportation to the final costumer. However, to obtain polymers with high solid contents, the difficulties with the stabilization of the emulsion, the higher viscosity and formation of residues (clots) generate limitations in the process, interfering in the safety of reaction. To this paperwork was chosen the styrene-butadiene emulsion copolymerization because of their industrial importance as well as the relevant properties for industrial safety aspects. The objective was to study the influences of the increased solids content in the properties of the styrene butadiene emulsion in a semi-continuous process that affect the safety of the emulsion copolymerization reaction. First of all, was found in the literature a model already validated to the styrene butadiene emulsion copolymerization in a semi-continuous process. This model was used as a base to perform simulations in the Aspen Polymers® software in order to examine the exothermic properties and the behavior of the emulsion. The solid content in the styrene-butadiene emulsion was increased gradually reducing the water of the formulation and maintaining proportionality between the other raw materials ranged from the original 48.4 % to 65.1 % where all water from the pre-emulsion was removed. The final properties of the emulsion had expected results as discussed on theoretical basis: the specific mass, viscosity, molecular weight and particle diameter enlarged with the increasing of solid content and polidispersity, the glass transition temperature, the specific heat and the thermal conductivity decreased. The reaction heat removal rate and the reaction temperature under adiabatic conditions in scenarios of possible runaway reaction were considered for the safety of the process, increasing significantly with the rise of solid content and indicating the presence of unreacted monomers at the end of the reaction time of 10 hours. The analysis of the sensitivity of the model was performed by changing the processing temperature of the final product in different concentrations in order to increase the reaction yield. For each change made, variations of product properties were analyzed in detail to verify changes in the final product. The best working point found in this study was 60 % of solids content at 78°C reaction temperature. The results demonstrated that small changes in process may be sufficient to ensure the safety of the process and the quality of the final product with high yields / Mestrado / Sistemas de Processos Quimicos e Informatica / Mestra em Engenharia Química

Orientador: Elaine Maria Cardoso / Resumo: Dissipadores de calor compactos, baseados em microcanais, têm se mostrado um meio eficaz para o resfriamento de dispositivos de alta densidade de energia, tais como microprocessadores, além de proporcionarem redução de material utilizado para a fabri-cação e do inventário de fluido refrigerante necessário. Sistemas bifásicos que operam com fluidos refrigerantes proporcionam coeficientes de transferência de calor elevados para baixos valores de velocidade mássica e uma distribuição de temperatura mais uni-forme na superfície. O presente estudo teve por objetivo avaliar experimentalmente o desempenho de um dissipador de calor baseado em microcanais, em condições de ebuli-ção convectiva saturada do fluido HFE-7100. O dissipador, em cobre eletrolítico, possui 33 microcanais de seção retangular com dimensões de 10 mm de comprimento, 200 μm de largura, 500 μm de altura e espaçados 100 μm entre si. A eficiência térmica do dissi-pador foi avaliada utilizando como fluido de trabalho o HFE-7100 (fluido refrigerante com baixo ozone depleting potencial, ODP, e global warming potential, GWP). Dados experimentais para o coeficiente de transferência de calor (CTC) e perda de pressão fo-ram obtidos em condições de escoamento monofásico e bifásico saturados, para diferen-tes valores de velocidades mássicas. As condições testadas foram de fluxo de calor im-posto (footprint) variando de 50 a 700 kW/m², com velocidades mássicas do fluido entre 392 e 875 kg/m²s, obtendo coeficientes de transferên... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Microchannel-based heat sinks have been shown to be an effective way of cool-ing high-density energy devices such as microprocessors, as well as reducing the material used to manufacture the exchangers and the required refrigerant inventory. Two-phase flow systems that operate with refrigerant fluids provide high heat transfer coefficients with low mass flux values and more uniform temperature distribution on the surface. The present study aimed to evaluate experimentally the performance of a heat sink based on microchannels under saturated conditions of convective boiling of HFE-7100 fluid. The analyzed heat sink has 33 rectangular section microchannels measuring 10 mm length, 200 μm wide, 500 μm high and spaced 100 μm apart. The heat sink was evaluat-ed using HFE-7100 (low ozone-depleting potential, ODP, and global warming potential, GWP) as working fluid. Experimental data for the heat transfer coefficient and pressure drop were obtained under saturated single and two-phase flow conditions for different values of mass velocities. An experimental apparatus was assembled and validated for the accomplishment of testing. As experimental conditions, the heat flux was applied in a range from 50 to 700 kW/m², with mass flux from 392 and 875 kg/m²s, obtaining a heat transfer coefficient of 60 kW/m² and pressure drop up to 12 kPa. By decreasing the mass flux and the input of the subcooling the HTC increases; the pressure drop increases monotonically with the increase in the mass fl... (Complete abstract click electronic access below) / Mestre

The theme of the diploma thesis "Effect of energy care on building prices" is the design and assessment of several measures, two of which generally lead to lower heating costs. The diploma thesis deals with evaluation of the current state of the family house and determination of PENB before the construction modifications and subsequently after the construction modifications, defining subsequent measures for energy saving implementation, both in terms of energy, economic and also environmental.

In the process of hot rolling is roll surface thermo-mechanically stressed. To define lifetime of roll or to increase it by change of thermal mode, temperatures and forces acting on this roll need to be known. For this purpose should be used sensors, that are placed near by surface of roll. Aim of the first part of diploma thesis is to debug 2D computing model (MKP) to achieve the match of temperature graphs with experimentally measured values, which was recorded by temperature sensors in real process of rolling. In the second part the same temperature boundary conditions are applied on 3D model, which is used to solve mechanical strength check of the temperature sensor. The last part of thesis is design and verification of mechanical strength of the designed force sensor. The used boundary conditions were acquired in Laboratory of heat transfer and flow. The computing system ANSYS 11 is used to design a model of geometry and numerical calculation. This diploma thesis will be used as donating solution for the granted project, which started in this year with Laboratory of heat transfer and flow partnership.

This thesis deals with dependence of heat transfer coefficient on rate of air concentration in the water. Main idea appears from gas dissolvability in water depending on pressure, Henry's law and Newton's law of cooling. There had been an experiment made to verify the hypothesis.