Orientadores: Rafael Augustus de Oliveira, Kil Jin Park / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agrícola / Made available in DSpace on 2018-08-25T10:54:18Z (GMT). No. of bitstreams: 1 SanchezSaenz_CarolinaMaria_D.pdf: 5939209 bytes, checksum: 43efccade58fb536d9e9c45782a43cc3 (MD5) Previous issue date: 2014 / Resumo: As pesquisas atuais em secagem de alimentos levam em consideração a qualidade do produto e a eficiência energética do processo, já que este processo consome cerca de 20-25% da energia utilizada pelo processamento na indústria de alimentos. Isto faz com que sejam exploradas novas técnicas e combinações de métodos de secagem e avaliação da intermitência do processo. Assim, realizou-se mais um estudo com o secador agitador/misturador (patente PI 0506639-5), iniciando pela adequação das pás do eixo misturador e adaptação do sistema de controle de velocidade e aquecimento do ar. O tempo de residência foi determinado considerando a rotação do eixo das pás e a rotação do eixo de alimentação do secador. Foi avaliada a influência dos parâmetros de secagem sobre o processo, de modo que foi possível determinar as melhores condições de pré-secagem HTST (High Temperature and Short Time) combinada com a secagem convectiva contínua com aplicação de radiação infravermelha, para obtenção de um produto de qualidade e com baixa demanda de energia elétrica no processo. Foi feito também o estudo da influência desses processos nas propriedades físicas e mecânicas de raízes de chicória. A redução da demanda de energia elétrica foi obtida considerando a intermitência da aplicação de radiação infravermelha. Os testes e análises realizados nestas condições resultaram em uma série de dados que garantem que a combinação de métodos de secagem e de técnicas de intermitência são eficientes energeticamente e resultam em um produto de boa qualidade / Abstract: In recent research works, food drying takes into account product quality and energy efficiency of process, since drying process consumes about 20-25 % of the energy used by the food processing industry. This fact indicates that new techniques combining drying methods and intermittency of the process must be evaluated. Thus, a study with the agitator / mixer dryer (patent PI 0506639-5) was performed, beginning with the mixer blades adequacy and velocity control and air heating systems adaptation. Residence time distribution determination has been conducted, considering rotation of blades and feed rotation of dryer. The influence of dying parameters on the process was evaluated, so that it was possible to determine the best conditions of HTST (High Temperature and Short Time) drying combined with the continuous drying with pulse of infrared radiation application, to obtain a good quality dried product and electric energy efficiency of the process. Study the influence of these processes was also done on the physical and mechanical properties of chicory roots. Finally, the electric energy efficiency was obtained considering the intermittency of pulse infrared radiation application. The experimental runs and analyses under these conditions have generated data which ensure that the combination of drying methods and intermittency techniques are energy efficient and result in a good quality product / Doutorado / Tecnologia Pós-Colheita / Doutora em Engenharia

Made available in DSpace on 2014-08-20T14:25:48Z (GMT). No. of bitstreams: 1 dissertacao_ mirlen_silva.pdf: 5380999 bytes, checksum: 0a2780f3032a4c42e7bb48f0a5402213 (MD5) Previous issue date: 2009-03-10 / In this work it is presented the study of 6 years of detected lightning data in association to the occurrence of mesoscale convective systems in the region located between 15ºS - 27ºS and 35ºW - 55ºW. The Lightning data were provided by FURNAS Centrais Elétricas S.A. for the period 2002-2007. Geostationary satellite images, enhanced in the infrared channel, were used to identify the cases of interest utilizing -50ºC as cloud top level temperature threshold for convective clusters. For these days, lightning detected in the study region should attain a minimum value of 1000 during 1 hour in some moment of occurrence during the identified cases. From the 565 days that satisfied this criterion, it was selected 25 cases occurred in 33 days during the years of 2003, 2005 (from October to December due to satellite images limitations), 2006 and 2007. For the period of occurrence of each one of these 25 cases, the detected lightning were counted during an interval of 15 minutes before and after the time of the satellite images used in each case to put in evidence the lightning associated to the observed convective clusters. The quantity of detected lightning in a convective cluster were related to its evolutive cycle. / Neste trabalho é apresentado o estudo de 6 anos de dados de descargas elétricas atmosféricas (DEA) detectadas em associação com a ocorrência de sistemas convectivos de mesoescala na região compreendida entre 15ºS e 27ºS e 35ºW e 55ºW. Os dados de DEA foram cedidos por FURNAS Centrais Elétricas S.A. para o período de 2002-2007. As imagens de satélite geoestacionário, realçadas no canal infravermelho, foram usadas para a identificação dos casos de estudo utilizando o valor limiar de -50ºC para temperatura dos topos das nuvens convectivas. Para estes dias, as DEA detectadas na região de estudo deveriam atingir o valor mínimo de 1000 no intervalo de 1 hora em algum momento de ocorrência dos casos identificados. Dos 565 dias contabilizados desta forma, foram selecionados 25 casos de estudo, ocorridos em 33 dias dos anos 2003, 2005 (de outubro a dezembro, por limitações nas imagens de satélite), 2006 e 2007. Para o período de ocorrência de cada um destes 25 casos, foram contabilizadas as DEA no intervalo de 15 minutos antes e depois do horário das imagens de satélite utilizadas em cada caso, para colocar em evidência as DEA associadas aos aglomerados convectivos observados. Ficou evidenciado que a quantidade de DEA detectadas em um aglomerado convectivo esteve relacionada diretamente com o ciclo evolutivo do mesmo.

La controverse concernant les mécanismes proposés pour l’intensification de la conductivité thermique et de la forte augmentation de la viscosité suggère que les expériences avec des nanofluides bien dispersés et correctement caractérisés seraient intéressantes. Par conséquent, nous nous sommes fixés comme objectif la caractérisation de la conductivité thermique et la viscosité de deux nanofluides “eau-oxyde de silice“ et “eau-titanium“. Il a été observé que la conductivité thermique des deux nanofluides considérés concorde bien avec la théorie du milieu effectif, à savoir, le modèle de Maxwell, et ne montre aucune amélioration par rapport aux effets associés aux mécanismes proposés de l’intensification du transfert du nanofluide tels que le mouvement brownien ou l’effet de stratification. Pour confirmer ce résultat, nous avons également mesuré la conductivité thermique du nanofluide eau contenant une suspension de nanotubes de carbone NTC. Nous constatons que la conductivité thermique de ce nanofluide NTC est également en bon accord avec le modèle de Maxwell. Les disparités et les incohérences publiées par les différents groupes sur les résultats et modèles de la conductivité thermique ainsi que la viscosité du nanofluide se trouvent être principalement dues à la qualité du nanofluide telles que la stabilité colloïdale, la taille des particules, la formation des agrégats, etc… Par ailleurs, l’influence des incertitudes en raison de l’adoption de différents modèles sur le transfert de chaleur par convection naturelle a été étudiée. Il a été observé que les incertitudes dans les modèles prédictifs peuvent conduire à des évaluations erronées du transfert convectif. / The controversy regarding the proposed mechanisms of the exceptionally enhanced thermal conductivity of nanofluids, as well as sharp increase of nanofluid viscosity suggest that systematic experiment with well dispersed and well characterized nanofluids are highly desired. Therefore, on the basis of this suggestion, thermal conductivity and viscosity of silica-water and titania-water nanofluids were measured. It was observed that the thermal conductivity of both nanofluids agrees well with the effective medium theory, i.e., Maxwell model, and does not show any enhancement due to effects associated with the proposed mechanisms of thermal energy transfer in nanofluids like Brownian motion or liquid layering. To support these results, the thermal conductivity of water based nanofluid containing carbon nanotubes was measured. It was found that that thermal conductivity of CNTs nanofluids agrees well with Maxwell model up to 1 vol.%. The inconsistencies in the reported thermal conductivity and dynamic viscosity from different research groups are found to be mainly due to the characterization of the nanofluid, including determination of colloidal stability and particle size, (i.e, aggregates size) within nanofluid. The influence of uncertainties due to adopting various formulas for the dynamic viscosity on natural convection heat transfer was investigated. It was observed that uncertainties in the predictive models for the effective thermal conductivity and dynamic viscosity of nanofluids, leads to erroneous evaluation of the convective heat transfer with nanofluids, and this acts as a brake on research in the area.

Cette thèse est une contribution à la simulation numérique des transferts de quantité de mouvement et de chaleur dans les écoulements turbulents de fluides non-Newtoniens dans une conduite cylindrique fixe. La viscosité du fluide utilisé est décrite par la loi d'Ostwald de Waele. Deux modèles sous-mailles dans l'approche des simulations des grandes échelles ont été considérés : le modèle dynamique de Germano et al. (1991) et le modèle de Smagorinsky non-Newtonien. Ils sont utilisés pour décrire les mécanismes physiques mis en jeu dans les écoulements isothermes de ces fluides à rhéologie complexe. Les transferts thermiques sont simulés avec le modèle de Smagorinsky non-Newtonien. Ces derniers sont traités en deux parties. La première concerne les échanges de chaleur sans influence sur la distribution des vitesses. Il s'agit des écoulements non-thermo dépendants ou écoulements isothermes. La deuxième partie concerne la résolution des écoulements thermo dépendants qui mettent l'accent sur les modifications induites par le couplage vitesse-température. Les champs turbulents sont analysés statistiquement en moyennant dans le temps et dans l'espace (suivant les directions périodiques) les champs instantanés de vitesse et de température pour établir les profils moyens de vitesse et de température, les rms, la tension de Reynolds, les flux de chaleur, les moments d'ordre plus élevé (coefficients de dissymétrie et d'aplatissement), les pdf (fonction de densité de probabilté), les jpdf (fonction de densité de probabilité jointe), le coefficient de frottement, le nombre de Nusselt... Ces différentes grandeurs sont analysées en fonction des divers paramètres qui gouvernent le problème: les nombres de Reynolds et de Prandtl, l’indice d'écoulement et le nombre de Pearson / This thesis is a numerical contribution of momentum and heat transfer of turbulent pipe flows of non-Newtonian fluids. The apparent viscosity of the fluid is modelled by a power-law (Ostwald de Waele model). Two models subgrid of LES were considered: the dynamic model of Germano et al. (1991) and model Smagorinsky non-Newtonian. They are used to describe the physical mechanisms involved in the isothermal flow of these complex rheology fluids. Heat transfer are simulated with the model of non-Newtonian Smagorinsky. These are processed in two parts. The first concerns the heat exchange without affecting the velocity distribution. This is non-thermo dependent flow or isothermal flow. The second part concerns the resolution of thermo dependent flows that focus on changes induced by the temperature-velocity coupling. The turbulent fields are analyzed statistically by averaging over time and space (according to the periodic directions) the instantaneous field of velocity and temperature to establish the average profiles of velocity and temperature, the root mean square of turbulent fluctuations (rms), Reynolds stress, the heat flow, the moments of higher order (skewness and flatness), the pdf (probability density function), the jpdf (attached probability density function), the coefficient of friction, the number of Nusselt ... These differents variables are analyzed for various parameters governing the problem: the Reynolds and Prandtl flow index and the number of Pearson

La carencia de servicios básicos como agua potable, para zonas como Cajamarquilla, es un problema social que se debe solucionar. Ante esta situación existen proyectos para dotar de servicios de agua a la zona, que por la geografía que presentan se utilizarán reservorios apoyados en los cerros aledaños. El procedimiento de diseño de un reservorio circular de concreto para la zona, servirá como guía para futuros proyectos. Siendo el objetivo de la investigación proponer criterios y un método adecuado para diseñar la estructura de un reservorio de concreto armado que cumplan con los parámetros de la propuesta de norma E030 2014 para la zona de Cajamarquilla, dada la poca información que existe de estos a pesar de ser de uso muy común en nuestro país. El tipo de la investigación es cualitativo, correlacional y de diseño experimental puro, con el fin de obtener resultados certeros para el diseño de reservorio. Finalmente, el método a usar es el que propone la norma del ACI 350-06, basándose en masas impulsivas y convectivas, del modelo de Housner, para el análisis estático mientras que para análisis el dinámico se utilizó el software Sap2000, por el método de elementos finitos y aplicando el espectro de diseño de la norma ACI 350 adecuándose a la norma peruana, como también para el diseño estructural de los elementos del tanque. La distorsión hallada es de 0.001 y que las cortantes basales estáticas y dinámicas son similares estando en un rango de 90%, por lo que se cumplen con los parámetros de la nueva propuesta de norma E030 2014. The lack of basic services such as water, to areas like Cajamarquilla, is a social problem to be solve. In this situation there are plans to provide water services to the area, by geography reservoirs that have supported in the surrounding hills are used. The process of designing a concrete circular reservoir area will serve as a guide for future projects. As the aim of the research propose criteria and an appropriate method to design the structure of a reinforced concrete reservoir that meet the parameters of the proposed rule for the 2014 E030 Cajamarquilla area, given the little information that exists in spite of these It is very commonly used in our country. The type of research is qualitative, pure correlational and experimental design, in order to obtain accurate results reservoir design. Finally, the method used is the standard proposed by the ACI 350-06, based on impulsive and convective mass Housner model for static analysis while for the Sap2000 dynamic analysis software used by the method of and applying the finite element design spectrum ACI 350 standard adapting to the Peruvian standard, as well as for the structural design of the elements of the tank. The distortion founded that the cutting 0.001y static and dynamic baseline are like being in a range of 90%, so that meet the parameters of the new E030 2014 proposed rule.

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

Title: Cloud-top morphology of convective storms as observed by meteorological satellites Author: Michaela Radová Department: Department of Atmospheric Physics Supervisor: RNDr. Martin Setvák, CSc., Czech Hydrometeorological Institute Abstract: This work focuses on study of features occurring at tops of convective storms, namely embedded warm areas, cold rings, cold-U/Vs and overshooting tops (OTs), mainly from the perspective of satellite observations. We have assembled a database of 104 subjectively detected cold rings and cold-U/Vs from the area of Europe. We discuss relationship between satellite- observed brightness temperature and cloud top height determined from radar measurements for storms with distinct cold-rings. Our results support the hypothesis that the warm area is a consequence of presence of central elevated dome reaching warmer lower stratosphere. Moreover, a storm with transformation of cold ring into cold-U is studied and an elevated plume above storm anvil in the warmer lower stratosphere is found to be a likely explanation of the warm area inside the cold-U. Both analyses confirm that thermal inversion above the tropopause is a necessary prerequisite for occurrence of cold rings and cold-U/Vs. We also propose a method for automated objective determination of spatial characteristics of...

Within this Ph.D. thesis, the optical thickness and particle effective radius of cirrus and deep convective clouds (DCCs) are retrieved using passive remote sensing techniques. For this purpose, airborne and satellite measurements of spectral solar radiation combined with extensive radiative transfer simulations have been conducted. Data analyzed in this study were collected during the ML-CIRRUS and the ACRIDICON-CHUVA campaigns, which aimed to study natural and contrail cirrus over Europe and DCCs over the Amazon rainforest using the German High Altitude and Long Range Research Aircraft (HALO), respectively. During the campaigns, HALO was equipped with a comprehensive set of remote sensing and in situ instruments. In particular flights, closely collocated measurements with the overpasses of the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard of the Aqua satellite were carried out. A cirrus located above liquid water clouds and a DCC topped by an anvil cirrus are investigated. In general, the research framework can be divided into four parts. In the first part, the spectral upward radiances measured by the Spectral Modular Airborne Radiation Measurement System (SMART)-Albedometer aboard of HALO are compared with those measured by the MODIS. In the second part, a radiance ratio retrieval assuming a vertically homogeneous cloud is applied to obtain the cloud optical thickness and particle effective radius based on the measurements of SMART-Albedometer and MODIS. Multiple near-infrared wavelengths with different absorption characteristics are utilized in the retrieval in order to study the vertical structure of cloud particle sizes. In the third part, the retrieved cloud properties are compared with those derived from the MODIS cloud products. For the cirrus case, the retrieved values of particle effective radius are further compared to in situ data measured by the Cloud Combination Probe (CCP). To allow this comparison, a vertical weighting method is applied. Although the comparison results in a good agreement, retrievals using this conventional technique only provide information on cloud particle sizes from the upper layers, even if spectral measurements have been employed. The retrieved particle effective radius represents a vertically weighted value, where the upper cloud layers are weighted at most. In the fourth part, an extended technique based on Bayesian optimal estimation has been developed to obtain the full vertical profile of particle effective radius. For this purpose, a parameterization assuming the shape of the vertical profile with respect to a vertical coordinate within the cloud is applied. The information content of SMART-Albedometer measurements is analyzed to identify wavelengths that bring the most information pertaining to each retrieval parameter. The new retrieval technique is applied to the cirrus case to infer the profile of particle effective radius as a function of optical thickness. The comparison between the retrieved and the in situ profiles shows a good agreement with a deviation of about 5 % at the cloud top and increases to values of up to 15 % at the cloud base. The new retrieval technique has shown excellent skill in improving the study of the vertical profile of cloud microphysical properties, which can be applied in the future generation of airborne and satellite retrievals based on the measurements of passive remote sensing.:1. Introduction 2. Definitions 3. Measurements 4. Comparison of upward radiance 5. Retrieval of cloud optical thickness and particle effective radius 6. Comparison of cloud optical thickness and particle effective radius 7. Retrieval of the vertical profile of particle effective radius 8. Summary and conclusion

An extended open system such as traffic flow is said to be convectively unstable if perturbations of the stationary state grow but propagate in only one direction, so they eventually leave the system. By means of data analysis, simulations, and analytical calculations, we give evidence that this concept is relevant for instabilities of congested traffic flow. We analyze detector data from several hundred traffic jams and propose estimates for the linear growth rate, the wavelength, the propagation velocity, and the severity of the associated bottleneck that can be evaluated semi-automatically. Scatter plots of these quantities reveal systematic dependencies. On the theoretical side, we derive, for a wide class of microscopic and macroscopic traffic models, analytical criteria for convective and absolute linear instabilities. Based on the relative positions of the stability limits in the fundamental diagram, we divide these models into five stability classes which uniquely determine the set of possible elementary spatiotemporal patterns in open systems with a bottleneck. Only two classes, both dominated by convective instabilities, are compatible wiqth observations. By means of approximate solutions of convectively unstable systems with sustained localized noise, we show that the observed spatiotemporal phenomena can also be described analytically. The parameters of the analytical expressions can be inferred from observations, and also (analytically) derived from the model equations.

Les étapes de mélange sont souvent délicates à appréhender, car il subsiste encore des lacunes sur les lois dynamiques qui régissent ces opérations. De ce fait, la prédiction de l’homogénéité d’un mélange de poudres nécessite encore de nombreux essais. Dans ce travail de thèse, nous nous attachons à développer une méthodologie qui permet de contribuer au développement de modèles prédictifs dans les mélangeurs de poudres tout en mettant en évidence des invariants possibles pour les changements d’échelle sur ces procédés. Ainsi nous avons étudié l’agitation de poudres, avec différentes résistances à l’écoulement, dans un mélangeur convectif planétaire de type Triaxe® d’une contenance de 48 L. Des mesures de propriétés rhéologiques à l’échelle du laboratoire (rhéomètre FT4, voluménomètre) sont effectuées afin de mieux comprendre le comportement des poudres à l’échelle du mélangeur. Un mélangeur convectif prototype a été conçu dans le cadre de cette thèse. Cet appareil polyvalent constitué d’une cuve cylindrique transparente et agité par un mobile constitué de quatre pales, permet de visualiser les régimes et les mécanismes d’écoulement tout en effectuant des mesures rhéologiques. Deux régimes d’écoulement ont été identifiés (roulement, cataracte), ainsi que trois mécanismes (convection, diffusion et avalanche). Ces mécanismes ont permis d’établir un modèle stochastique, dont les paramètres ont été évalués expérimentalement pour une poudre à écoulement libre et pour une poudre cohésive. / Mixing systems are usually difficult to understand, because there is a lack of knowledge concerning dynamic laws ruling these operations. Thus, nowadays, several tests are needed to predict properly the homogeneity of a powder mix. Throughout this PhD work, a method is developed to build predictive models for powder mixers and to bring out possible invariants for scale switching on these processes. Thus the stirring of powders is studied using different flow resistances within a 48L capacity Triaxe®, a convective planetary mixer. Rheological properties measurements are done at labscale (FT4 rheometer, volumenometer) for a better understanding of powder behavior at a wider mixer scale. A prototype blender has been built for this work. This polyvalent device, made of four blades and of a transparent vessel, allows to observe flow regimes and mechanisms, and to do rheological measurements. Two flow regimes have been identified (rolling, cataracting) and three flow mechanisms (convection, diffusion and avalanching). These mechanisms allowed to do stochastic modelling, for which parameters have been evaluated with experiments for free-flowing and cohesive powders.