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Dissertations / Theses on the topic 'Air - Temperature - Numerical Simulation'

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Published: 4 June 2021
Last updated: 6 September 2023

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1

Guilbaud, Claude. "Étude des inversions thermiques : application aux écoulements atmospghériques dans des vallées encaissées." Université Joseph Fourier (Grenoble), 1996. http://www.theses.fr/1996GRE10068.

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Le code Submeso est développé dans le but de comprendre et d'analyser les phénomènes d'inversion thermique dans les vallées encaissées. Les grandes échelles de l'écoulement (LES) sont obtenues par la résolution des équations tridimensionnelles du mouvement écrites sous leur forme compressible et non-hydrostatique en coordonnées dites gal-chen. Un modèle sous-maillé basé sur une équation de transport de l'énergie cinétique turbulente permet de transférer la production d'énergie turbulente générée au sol vers les couches supérieures de l'atmosphère. Les échanges entre le sol et l'atmosphère sont décrits par un modèle de sol (sm2-isba), couplé à un modèle de paroi performant. Le modèle de sol est validé sur deux campagnes de mesures sur site efeda et hapex - mobilhy. La prise en compte de l'interaction sol-atmosphère a été validée par deux études de la couche limite planétaire: une couche limite atmosphérique pleinement convective et l'évolution d'une couche limite planétaire correspondant à l'expérience de Wangara. Une étude complète de la structure des écoulements atmosphériques dans des vallées encaissées est réalisée. Dans un premier temps, on étudie l'évolution temporelle d'un scalaire passif émis dans un relief complexe 3D avec des échanges sol-atmosphère simplifiés. Puis, les phénomènes d'inversions thermiques sont étudiés dans une vallée stylisée, pour deux saisons. Le modèle réaliste des échanges sol-atmosphère a permis de simuler le cycle diurne complet. On met en évidence une variabilité saisonnière du comportement de l'inversion. L'été, les phénomènes ont une durée de vie et des périodes de transition plus longue qu'en hiver. Contrairement au cas hivernal, la structure spatiale de la couche convective estivale est symétrique par rapport à l'axe médian de la vallée.
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2

Wang, Xiaodong. "Modélisation et simulation numérique de la combustion en présence d’interactions flammes/auto-inflammation Interactions between mixing, flame propagation, and ignition in non-premixed turbulent flames normalised residence time transportequation for the numerical simulation of combustion with high-temperature air." Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2020. http://www.theses.fr/2020ESMA0002.

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Cette thèse de doctorat est consacrée à la modélisation des écoulements turbulents réactifs dans des cas où les niveaux de température peuvent conduire à l'auto-allumage du mélange. La stratégie de modélisation proposée consiste à traiter séparément les différents mécanismes physiques les plus importants : mélange des espèces chimiques, propagation de fronts de flammes et auto-inflammation. Ainsi, des méthodes simples, dérivées de modèles connus en combustion turbulente non-prémélangée et prémélangée (méthodes de tabulation, PDF présumée) sont utilisées pour représenter les mécanismes de mélange des espèces et de propagation des fronts. Des développements spécifiques sont apportés pour que ces modèles soient toujours valides en présence d'auto-allumage. Les paramètres de modélisation introduits sont clairement identifiés et la sensibilité des résultats numériques à leurs valeurs est étudiée en détail. Le développement le plus important de ce travail concerne la méthode basée sur l'utilisation d'un temps de résidence pour modéliser l'auto-allumage du mélange. Comme la comparaison directe du temps de résidence au délai d'auto-allumage n'a plus de signification physique dès lors que la composition et la température évoluent avant l'auto-inflammation, un temps de résidence normalisé est introduit. Cette quantité peut aussi être présentée comme l'âge relatif des particules qui vieillissent différemment selon les caractéristiques du mélange local. L'équation bilan correspondante est dérivée soit de celle pour le temps de résidence soit par analogie avec l'équation G décrivant la propagation d'un front de flamme. Dans ce dernier cas, le temps de résidence est considéré comme une fonction "level-set" adaptée au suivi de fronts d'auto-inflammation. L'utilisation de ce temps normalisé permet aussi de traiter la difficulté liée aux conditions limites de temps de résidence. Le modèle proposé est d'abord utilisé pour simuler une flamme turbulente non-prémélangée de type JHC (Jet-in-Hot-Coflow) en RANS avec le logiciel de calcul numérique Code-Saturne (Bas Mach). Les résultats numériques sont validés pour deux conditions expérimentales différentes. Le modèle est ensuite validé par des calculs DNS de couche de mélange 1D soumise à l'auto-inflammation. Enfin, des simulations numériques préliminaires d'une configuration expérimentale récente disponible au laboratoire (Constant Volume Vessel) sont réalisées pour évaluer la faisabilité de l'extension du modèle en LES compressible avec OpenFOAM
The present study is devoted to the modelling of turbulent reactive flows in cases where the temperature levels can lead to the self-ignition of the mixture. The proposed modelling strategy consists of treating separately the most important physical mechanisms : scalar mixing, flame propagation and self-ignition. Thus, simple methods derived from known models in non-premixed and premixed turbulent combustion(tabulation methods, presumed PDF) are used to represent the mixing mechanism of species and flame propagation. The most important development of this work concerns the method based on the use of a residence time to model the self-ignitionof the mixture. Since the direct comparison of the residence time with the self-ignition delay has no physical meaning as long as the composition and the temperature change before the self-ignition, a normalised residence time is introduced. This quantity can also be presented as the relative age of particles that age differently depending on the characteristics of the local mixture. The use of this normalised time also makes it possible to deal with the difficulty related to the boundary conditions of residence time. The proposed model is first used to simulate a non-premixed JHC(Jet-in-Hot-Coflow) turbulent flame in RANS with numerical computation softwareCode-Saturne(low Mach). This model is then validated by DNS calculations of 1D mixing layer subjected to self-ignition. Finally, preliminary numerical simulations of a recent experimental configuration available in the laboratory(Constant Volume Vessel) are carried out to evaluate the feasibility of extending the compressible LES model by using OpenFOAM
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3

Vaz, Joaquim. "Estudo experimental e numérico sobre o uso do solo como reservatório de energia para o aquecimento e resfriamento de ambientes edificados." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2011. http://hdl.handle.net/10183/28814.

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Objetivos: Este trabalho, abrangendo a área da transferência de calor e da mecânica dos fluidos, em seu desenvolvimento envolveu métodos analíticos, numéricos computacionais e experimentais (em ambiente de campo), com a finalidade de analisar o uso de trocadores de calor solo-ar, como estratégia para diminuir o consumo de energia convencional, no aquecimento ou resfriamento de ambientes construídos. Assim, um dos objetivos do estudo foi avaliar, com base em resultados experimentais, a performance do solo como um reservatório de energia, derivada da radiação solar. Buscou-se, pois, identificar parâmetros, procedimentos e condições favoráveis envolvendo esta estratégia. O outro objetivo do estudo foi, usando os softwares GAMBIT e FLUENT, modelar computacionalmente o escoamento do ar no trocador de calor solo-ar. Método: O estudo experimental e numérico foi precedido pela construção de uma edificação, especificamente concebida para a pesquisa, identificada como Casa Ventura. Em continuidade, foram enterrados dutos no solo, que conduziriam ar exterior e água (esta última por um período limitado) ao ambiente interno. No caso da condução de ar, o solo funcionaria como um reservatório de energia, aquecendo ou resfriando a ar. Já, no caso da condução de água, prevista com duto de baixa condutividade térmica, o solo funcionaria apenas como um protetor à radiação solar, para preservar as características térmicas da água, desde um reservatório, de onde a mesma era bombeada, até o interior da casa. Na Casa Ventura foram construídos dois ambientes centrais com características dimensionais e de envolvente equivalentes, constituindo os ambientes monitorados no processo, sendo um, na condição natural, referencial, sem renovação de ar, e o outro, com renovação de ar. Na parte experimental, o ar foi captado do ambiente externo e insuflado por um ventilador nos dutos enterrados, renovou o ar no interior deste último ambiente. Com ajuda de um fan-coil, colocado neste ambiente, o ar renovado trocou calor com a água. Por questões de dificuldades operacionais, o bombeamento de água funcionou por um período muito curto. Durante o experimento, que se desenvolveu por todo o ano de 2007, foram monitoradas e registradas, além da temperatura do solo e da água, a temperatura e a umidade: do ar externo, do ar nos ambientes internos e do ar em escoamento nos dutos enterrados, bem como a velocidade de escoamento nos mesmos. Resultados: De forma geral, o potencial do solo para aquecer foi maior do que o de resfriamento do ar injetado nos dutos enterrados. O potencial de aquecimento foi mais destacado nos meses de maio, junho, julho e agosto, e se mostrou maior que 3K. Para profundidades entre 2 e 3m, estima-se que o potencial possa ser superior a 8K. Por outro lado, o potencial de resfriamento foi maior nos meses de janeiro, fevereiro e dezembro, mas foi baixo para pequenas profundidades (menos de um metro). Para resfriamento, este potencial pode chegar a 4K. Contribuições da pesquisa: Face aos resultados da pesquisa, diversas foram as suas contribuições, dentre as quais se destacam: a construção de um banco de dados experimentais sobre as propriedades e características do solo (índices físicos, difusividade térmica, capacidade térmica volumétrica, condutividade térmica, temperatura e umidade) e do ar ambiente (temperatura e umidade) para o município de Viamão, localizado na região sul do Brasil, e que pode ser usado para a continuidade desta pesquisa ou para a elaboração de novas pesquisas e projetos; e o desenvolvimento de uma metodologia para a modelagem computacional de trocadores de calor solo-ar, validada através dos dados experimentais citados acima, possibilitando, assim, o emprego deste procedimento numérico, para a elaboração de projetos ou novas pesquisas nesta área.
Purpose: The development of the present work, comprising the area of heat transfer and fluids mechanics involved analytical, numerical computational and experimental (in field environment) methods, with the purpose of analyzing the use of earth-to-air heat exchanger, as a strategy to reduce conventional energy consumption, for the heating or cooling of built environments. Thus, one of the study purposes was to evaluate, based on experimental results, the earth performance as an energy reservoir, derived from solar radiation incidence on the surface of the ground. We aimed, then, at identifying favorable parameters, procedures and conditions involving this strategy. The other study purpose was, using the GAMBIT and FLUENT softwares, computationally modeling the air flow in the earth-to-air heat exchanger. Method: The experimental and numerical study was preceded by the construction of a building, specially planned for the research, called Casa Ventura. As a follow-up, ducts were buried on the ground, to conduct external air and water (the latter one for a limited period) to the internal environment of the house. In terms of air conduction, the earth would work as an energy reservoir, heating or cooling the air. Concerning the water conduction, planned to use a duct of low thermal conductivity, the earth would only work as a protector from solar radiation, to preserve the water thermal characteristics, when flowing from the water reservoir, where it would be taken from, to the inside of the house. At Casa Ventura two central environments were built with similar dimensional and envelope characteristics, constituting the environments monitored in the process, in which, one in the natural and referential condition, without air renovation, and the other, with air renovation. In the experimental part, the air was captured from the external environment and inflated by a fan in the buried ducts, and it renovated the air inside this latter environment. With the help of a fan-coil, placed in this environment, the renovated air exchanged heat with the water flowing through the ducts. Due to some operational difficulties, the pumping of water lasted for a very short period. During the experiment, which lasted through the whole year of 2007, besides the water and earth temperature, the temperature and humidity of the following were also monitored and registered: the external air, the air in the internal environments and the air flowing in the buried ducts, as well as the flowing speed of the different fluids. Results: In a general way, the earth potential to heat was higher than the cooling of air injected in the buried ducts. The heating potential was higher in the months of May, June, July and August, doing so by more 3K. For depths between 2 and 3m, it is estimated that the potential might be over 8K. On the other hand, the potential for cooling was higher in the months of January, February and December, but it was low for low depths (less than a meter). For cooling, this potential may reach 4K. Research contributions: Considering the research results, several were the contributions, among which we highlight: the construction of an experimental database on the earth properties and characteristics (physical indexes, thermal diffusivity, volumetric heat capacity, thermal conductivity, temperature and humidity) and the environmental characteristics of the air (temperature and humidity) for the city of Viamão, located in Southern Brazil, and that may be used for the continuation of this research or for the elaboration of new researches and projects; and the development of a methodology for computational modeling of earth-to-air heat exchangers, validated through the experimental data mentioned before, enabling, therefore, the use of this numerical procedure for the elaboration of projects or new researches in this area.
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4

Soultogiannis, A. Alexios Carleton University Dissertation Engineering Mechanical. "Numerical simulation of ventilation air movement in offices." Ottawa, 1990.

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5

Barimani, Mohammad. "Numerical simulation of particle separation in centrifugal air classifiers." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/56718.

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The demand for fine mineral powder in various industries has stimulated creative methods for separating the fine portion of particles from a mixture. Among the many different types of classifiers invented, centrifugal rotor air classifiers are characterized by their capability in producing ultra-fine products with a cut-size as low as 3um. Classification occurs due to the size-dependence of aerodynamic and inertial forces acting on particles: coarse particles have a higher ratio of centrifugal force to aerodynamic drag than do fine particles, and therefore are preferentially ejected to the classifier perimeter. Therefore, the high speed rotor located inside the classifier is key to classification. Computational fluid dynamics (CFD) is utilized in this study to investigate the motion of calcium carbonate particles in a rotor classifier. The single phase flow in two- and three-dimensional models of the rotor is computed. Two turbulence models, namely K-Omega and RSM, are applied to close the Reynolds-averaged Navier-Stokes equations. Once the single phase flow has been computed the motion of solid particles is simulated using the Discrete Phase Model. This model ignores particle-particle interactions and the influence of the particles on the air flow. The motion of the particles is coupled to a statistical model of the turbulent velocity fluctuations. By tracking hundreds of particles, the efficiency for a variety of hypothetical classifiers is estimated. Though the CFD models, in comparison with experiments, cannot accurately predict the absolute cut-size values, they have proved effective in predicting cut-size shifts as a result of rotor geometry modification or alternative operating conditions. Based on these simulations two new rotors were built and the change in cut-size was predicted within 30% accuracy. Based on the paths of a large number of particles tracked in various operating conditions, regions in the rotor with very high particulate concentrations are identified. We speculate that this elevated concentration makes particle-particle interactions much more important than would be expected based on the feed concentration, which could in turn reduce the acceptance of the smallest particles.
Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate
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6

Wang, Kezhou Denney Thomas Stewart. "Numerical modeling of nasal cavities and air flow simulation." Auburn, Ala., 2006. http://repo.lib.auburn.edu/2006%20Spring/doctoral/WANG_KEZHOU_24.pdf.

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7

Ranjan, Arun Koushik Becker Bryan R. "Numerical simulation of genetically modified air-borne corn pollen flow." Diss., UMK access, 2004.

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Thesis (M.S.)--School Computing and Engineering. University of Missouri--Kansas City, 2004.
"A thesis in mechanical engineering." Typescript. Advisor: Bryan R. Becker. Vita. Title from "catalog record" of the print edition Description based on contents viewed Feb. 28, 2006. Includes bibliographical references (leaves 71-73). Online version of the print edition.
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8

Huang, Jian-Ping. "Numerical simulation study of ozone episodes in complex terrain and coastal region /." View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?MATH%202005%20HUANG.

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9

Donnelly, David Johnson. "Numerical Simulation of Surface Effect Ship Air Cushion and Free Surface Interaction." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/35326.

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This thesis presents the results from the computational fluid dynamics simulations of surface effect ship model tests. The model tests being simulated are of a generic T-Craft model running in calm seas through a range of Froude numbers and in two head seas cases with regular waves. Simulations were created using CD-adapcoâ s STAR-CCM+ and feature incompressible water, compressible air, pitch and heave degrees of freedom, and the volume of fluid interface-capturing scheme. The seals are represented with rigid approximations and the air cushion fans are modeled using constant momentum sources. Drag data, cushion pressure data, and free surface elevation contours are presented for the calm seas cases while drag, pressure, heave, and roll data are presented for the head seas cases. The calm seas cases are modeled both with no viscosity and with viscosity and turbulence. All simulations returned rather accurate estimations of the free surface response, ship motions, and body forces. The largest source of error is believed to be due to the rigid seal approximations. While the wakeâ s amplitude is smaller when viscosity is neglected, both viscous and inviscid simulationsâ estimations of the free surface qualitatively match video footage from the model tests. It was found that shear drag accounts for about a quarter of the total drag in the model test simulations with viscosity, which is a large source of error in inviscid simulations. Adding the shear drag calculated using the ITTC-1957 friction coefficient line to the total drag from the inviscid simulation gives the total drag from the viscous simulations within a 6% difference.
Master of Science
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10

Ho, Son Hong. "Numerical simulation of thermal comfort and contaminant transport in air conditioned rooms." [Tampa, Fla.] : University of South Florida, 2004. http://purl.fcla.edu/fcla/etd/SFE0000548.

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11

Randell, Per. "Numerical Simulation of Temperature and Velocity Profiles in a Horizontal CVD-reactor." Thesis, Linköpings universitet, Mekanisk värmeteori och strömningslära, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-117942.

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Silicon Carbide (SiC) has the potential to significantly improve electronics. As a material, it can conduct heat better, carry larger currents and can give faster responses compared to today’s technologies. One way to produce SiC for use in electronics is by growing a thin layer in a CVD-reactor (chemical vapour deposition). A CVD-reactor leads a carrier gas with small parts of active gas into a heated chamber (susceptor). The gas is then rapidly heated to high temperatures and chemical reactions occur. These new chemical substances can then deposit on the substrate surface and grow a SiC layer. This thesis investigates the effect of different opening angles on a susceptor inlet in a SiC horizontal hot-walled CVD-reactor at Linköping University. The susceptor inlet affects both the flow and heat transfer and therefore has an impact on the conditions over the substrate. A fast temperature rise in the gas as close to the substrate as possible is desired. Even temperaturegradients vertically over the substrate and laminar flow is desired. The CVD-reactor is modeled with conjugate heat transfer using CFD simulations for three different angles of the inlet. The results show that the opening angle mainly affects the temperature gradient over the substrate and that a wider opening angle will cause a greater gradient. The opening angle will have little effect on the temperature of the satellite and substrate.
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12

Dutta, Amitvikram. "Numerical simulation of the air flow and particulate deposition in emphysematous human acini." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/60170.

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Emphysema, is a destructive process that leads to the permanent enlargement of air spaces within the parenchyma of the lung. Along with chronic bronchitis, emphysema forms one of the two components of Chronic Obstructive Pulmonary Disease (COPD), a serious condition that is responsible for severe limitation of expiratory airflow in its victims. The early stages of emphysema are charecterized by the destruction of tissue in the pulmonary acinus - the part of the lung airway tree responsible of gas exchange with the bloodstream. Little is known how emphysema affects airflow within the acinus especially in the early stages of the disease. In this thesis computational fluid dynamics simulations are performed of airflow in a mathematically-derived model of a section of the pulmonary acinus. The computational domain consists of two generations of the acinus with alveolar geometries approximated as closely-packed, fourteen-sided polygons. Emphysema, is a destructive process that leads to the permanent enlargement of air spaces within the parenchyma of the lung. Along with chronic bronchitis, emphysema forms one of the two components of Chronic Obstructive Pulmonary Disease (COPD), a serious condition that is responsible for severe limitation of expiratory airflow in its victims. The early stages of emphysema are charecterized by the destruction of tissue in the pulmonary acinus - the part of the lung airway tree responsible of gas exchange with the bloodstream. Little is known how emphysema affects airflow within the acinus especially in the early stages of the disease. In this thesis computational fluid dynamics simulations are performed of airflow in a mathematically-derived model of a section of the pulmonary acinus. The computational domain consists of two generations of the acinus with alveolar geometries approximated as closely-packed, fourteen-sided polygons. Physiologically realistic flow rates and wall motions are used to capture the acinar flow during the inspiratory and expiratory phases of the breathing cycle. The effects of emphysema on the airway wall motion, flow rates, and septal destruction are simulated at various stages of the disease's progression to identify the effect on the flow in the acinar region. Parametric studies are presented to independently assess the relative influence of septal destruction and the emphysematous degradation of airway motion and flow rates. The results illustrate that septal destruction lowers the flow resistance through the alveolar ducts but has little influence on the mass transport of oxygen into the alveoli. Septal destruction has a net effect on the flow field by favouring the development of recirculatory flow patterns in individual alveoli. The effects of the gradually advancing emphysema on the deposition of micron-sized particles in the acinus are also studied. The simulations are categorized according to particle size and the relative orientation of the gravitational vector to the incoming flow. Emphysematous destruction increases the deposition of particles in affected ducts, with the greatest increase occurring for the larger particle size when the gravity vector is oriented tangential to the incoming flow.
Applied Science, Faculty of
Graduate
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13

Hess, Victor George. "Three-dimensional mathematical model of a high temperature polymer electrolyte membrane fuel cell." Doctoral thesis, University of Cape Town, 2016. http://hdl.handle.net/11427/24481.

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Polymer electrolyte fuel cells are regarded as one of the most promising alternatives to the depleting and high pollutant fossil fuel energy sources. High temperature Polymer electrolyte fuel cells are especially suitable for stationary power applications. However, the length scale of a PEM fuel cells main components range from the micro over the meso to the macro level, and the time scales of various transport processes range from milliseconds up to a few hours. This combination of various spatial and temporal scales makes it extremely challenging to conduct in-situ measurements or other observations through experimental means. Thus, numerical simulation becomes a very important tool to help understand the underlying electrochemical dynamics and transient transport phenomena within PEM fuel cells. In this thesis research a comprehensive, three- dimensional mathematical model is developed which accounts for the convective and diffusive gas flow in the gas channel, multi-component diffusion in the porous backing layer, electrochemical reactions in the catalyst layers, as well as flow of charge and heat through the solid media. The governing equations which mathematically describe these transport processes, are discretized and solved using the finite-volume based software, Ansys FLUENT, with its in-built CFD-solvers. To handle the significant non-linearity stemming from these transport phenomena, a set of numerical under-relaxation schemes are developed using the programming language C++. Good convergence is achieved with these schemes, though the model is based on a serpentine single-channel flow approach. The model results are validated against experimental results and good agreement is achieved. The result shows that the activation overpotential is the greatest cause of voltage loss in a high temperature PEM fuel cell. The degree of oxygen depletion in the catalyst layer, under the ribs, is identified and quantified for a given set of input parameters. This factor is followed by membrane resistance to protonic migration. The model can thus be suitable applied as a tool to predict cell performance. The results also show that performance is influenced by not just one, but a combination of inter-related factors, thus temperature increases, and flow rate changes will only be effective if simultaneously, the concentration of inlet oxygen, and the mobility of proton-ions in the membrane is increased. Not only does the model results verify these phenomena, but provide a quantitative output for any given set of input parameters. It can therefore be suitably applied as an optimisation tool in high temperature PEM fuel cell design.
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14

Kumar, Deepak. "Numerical simulation of flows in an active air intake device of internal combustion engine with pulsated air flow." Thesis, Ecole centrale de Nantes, 2018. http://www.theses.fr/2018ECDN0004/document.

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Les émissions polluantes à l’échappement des véhicules automobiles sont l'une des principales sources de pollution de l'air dans le monde d'aujourd'hui. Par conséquent, la législation a évolué afin de limiter ces émissions. L'un des aspects clés pour répondre consiste à bien maîtriser les échanges gazeux au sein du moteur à combustion interne. Cette amélioration est possible par l'optimisation de répartiteurs d'admission d'air. Dans ces répartiteurs d'admission d'air, la maitrise de l’écoulement de type tumble est une piste de progrès. Des volets sont installés à la sortie du répartiteur afin d'améliorer le rapport de tumble et donc le mélange air-carburant (VTS-Variable Tumble System). Une autre caractéristique de l'écoulement à l'intérieur des répartiteurs est l'effet des écoulements pulsés qui engendrent des fluctuations de pression assez importante. Par conséquent, le but de cette étude consiste à simuler le flux d'air pulsé à l'intérieur des répartiteurs d'admission et à identifier l'effet des pulsations de pression sur les composants actifs tels que les volets. Le travail de simulation dans la présente thèse a été effectué à partir du code open source CFD OpenFOAM. Dans un premier temps, l'effet des pulsations de pression est simulé à l'intérieur d'un tube d'acier et une méthodologie de simulation est développée. Les résultats de la simulation sont validés à partir de résultats expérimentaux obtenus sur un dispositif spécifique, le banc dynamique. Ensuite, des simulations ont été effectuées sur le répartiteur d'admission principal avec des volets. Tout d’abord, les simulations sont effectuées en régime permanent avec cinq positions d'ouverture différentes du clapet. Les forces et les moments agissant sur le volet en régime permanent sont obtenus et analysés. Puis, des simulations en régime transitoire avec des effets de pulsation de pression sont effectuées. Les résultats de la simulation instationnaire sont comparés aux résultats expérimentaux en termes de fluctuations de pression relative. Les effets des pulsations de pression sur les forces aérodynamiques et les moments agissant sur les volets sont analysés et commentés
The exhaust emissions from automobiles are one of the major sources of air pollution in today’s world. Thence,research and development is the key feature of the modern automotive industries to meet strict emission legislation. One of the key aspects to meet these requirements is to improve the gas exchange process within internal combustion engines. It is possible by the design optimization of the air intake manifolds for internal combustion engines. One of such advancement in air intake manifolds is variable tumble systems (VTS). In VTS system, tumble flaps are installed at the exit of the manifold runner in order to improve tumble ratio and hence air-fuel mixing. Another feature of the flow inside the intake manifolds is pressure pulsation effect. Therefore, the aim of the Ph.D. work is to simulate the pulsating air flow inside the air intake manifolds and to identify the effect of the pressure pulsations on the active components like tumble flaps. The simulation work in the present thesis has been carried out on open source CFD code OpenFOAM. In a first step, the effect of pressure pulsations is simulated inside a steel tube and a simulation methodology is developed. The results of the simulation are validated on a specific experimental device, the dynamic flow bench. Then,simulations have been carried out on the main intake manifold with tumble flaps. Firstly, the simulations are performed with five different opening positions of the tumble flap in a steady state configuration. The forces and moments acting on the flap in steady state are obtained and analyzed. Then, unsteady simulations with pressure pulsation effects are performed. The results of obtained from unsteady simulation are compared with the experimental results in terms of relative pressure fluctuations. The effect of the pressure pulsation on the aerodynamic forces and moments acting on the tumble flaps are analyzed and explained
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15

Yesilyurt, Gokhan. "Numerical simulation of flow distribution for pebble bed high temperature gas cooled reactors." Texas A&M University, 2004. http://hdl.handle.net/1969.1/372.

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The premise of the work presented here is to use a common analytical tool, Computational Fluid dynamics (CFD), along with a difference turbulence models. Eddy viscosity models as well as state-of-the-art Large Eddy Simulation (LES) were used to study the flow past bluff bodies. A suitable CFD code (CFX5.6b) was selected and implemented. Simulation of turbulent transport for the gas through the gaps of the randomly distributed spherical fuel elements (pebbles) was performed. Although there are a number of numerical studies () on flows around spherical bodies, none of them use the necessary turbulence models that are required to simulate flow where strong separation exists. With the development of high performance computers built for applications that require high CPU time and memory; numerical simulation becomes one of the more effective approaches for such investigations and LES type of turbulence models can be used more effectively. Since there are objects that are touching each other in the present study, a special approach was applied at the stage of building computational domain. This is supposed to be a considerable improvement for CFD applications. Zero thickness was achieved between the pebbles in which fission reaction takes place. Since there is a strong pressure gradient as a result of high Reynolds Number on the computational domain, which strongly affects the boundary layer behavior, heat transfer in both laminar and turbulent flows varies noticeably. Therefore, noncircular curved flows as in the pebble-bed situatio n, in detailed local sense, is interesting to be investigated. Since a compromise is needed between accuracy of results and time/cost of effort in acquiring the results numerically, selection of turbulence model should be done carefully. Resolving all the scales of a turbulent flow is too costly, while employing highly empirical turbulence models to complex problems could give inaccurate simulation results. The Large Eddy Simulation (LES) method would achieve the requirements to obtain a reasonable result. In LES, the large scales in the flow are solved and the small scales are modeled. Eddy viscosity and Reynolds stress models were also be used to investigate the applicability of these models for this kind of flow past bluff bodies at high Re numbers.
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Karanja, Bethuel, and Parsa Broukhiyan. "Commercial Vehicle Air Consumption: Simulation, Validation and Recommendation." Thesis, KTH, Maskinkonstruktion (Inst.), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-209657.

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This report details the work done in a master thesis project. The project was conducted at the Brake Performance Department at Scania CV AB. The project involves the development of a numerical model (in Matlab) that calculates and predicts air consumption in a truck under different drive cycles. The report first details tests and experiments done so as to acquire the necessary information for the development of the model. The report then presents the model that was created and delves into tests that were conducted for its validation. A model is created that allows the user to select different component combinations on the trucks along with different loading scenarios and drive cycles. Finally the model is used to evaluate air consumption in trucks during particularly strenuous cycles. The model developed is found to be reliable and accurate to with 7% with regard to amount of air consumed. With its help, several recommendations on how air consumption in commercial vehicles can be improved are made. The best components’ combination is also found and presented.
I denna rapport beskrivs ett examensarbete som genomfördes på bromsavdelningen på Scania CV AB. Projektet innefattar utveckling av en numerisk modell (i Matlab) som beräknar och förutspår luftförbrukningen i en lastbil under olika körcykler. I rapporten beskrivs det tester och experiment som gjordes för att ta fram nödvändiga uppgifter för utvecklingen av modellen. Sedan presenteras modellen som skapades och alla valideringstester som genomfördes. Modellen är gjord så att användaren kan kombinera olika komponentkombinationer för lastbilar med olika lastningskonfigurationer och körcykler. Slutligen används modellen för att utvärdera luftförbrukningen i lastbilar under särskilt ansträngande körcykler. Den utvecklade modellen visade sig vara pålitlig och korrekt med en felmarginal på 7% med avseende på mängden luft som konsumeras. Med dess hjälp kunde flera rekommendationer ges om hur luftförbrukningen i kommersiella fordon kan förbättras. De bästa komponentkombinationerna hittades också och presenteras i denna rapport
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17

Schumacher, Jurgen. "Numerical simulation of cantilevered ramp injector flow fields for hypervelocity fuel/air mixing enhancement." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0021/NQ53652.pdf.

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18

Tingas, John. "Numerical simulation of air injection processes in high pressure light & medium oil reservoirs." Thesis, University of Bath, 2000. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343763.

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Research, pilot scale and field developments of In-Situ Combustion (ISC) for enhanced oil recovery (EOR) in shallow, low pressure, heavy oil reservoirs intensified between the first and the second oil crisis from 1973 to 1981. A decline of interest in EOR followed the collapse of the oil prices in 1986. Renewed interest on in-situ combustion EOR research in the late 1980’s and beginning of the 1990’s was expanded and focused on high pressure medium and light oil reservoirs. The applicability of air injection in deep high pressure light petroleum reservoirs was established by research work of Greaves et al. in 1987 & 1988, Yannimaras et al. in 1991 and Ramey et a l in 1992. Accelerating rate calorimeter (ARC) tests were used to screen the applicability of various types of light oil reservoirs for in-situ combustion EOR by Yannimaras and Tiffin in 1994. The most successful light oil air injection project in the 1990s in the Medicine Pole Hills Unit, Williston Basin, N. Dakota started in 1987 and was reported by Kumar, Fassihi & Yannimaras, in 1994. Low temperature oxidation of light North Sea petroleum was studied at the University of Bath. A high-pressure combustion tube laboratory system was built at Bath University to evaluate performance of medium and light petroleum in-situ combustion processes. Gravity effects and the impact of horizontal wells in Forced Flow In-Situ Combustion Drainage Assisted by Gravity (FFISCDAG) were studied with three-dimensional combustion experiments. In this study, the university of Bath combustion tube experiments have been simulated and history matched. The tube experiments were up-scaled and field simulation studies were performed. A generic PVT characterization scheme based on 5 hydrocarbon pseudo-components was used, which was validated for light Australian and medium ‘Clair’ oil. A generic chemical reaction characterization scheme was used, which was validated for light Australian and medium ‘Clair’ oil. Advanced PVT and chemical reaction characterizations have been recommended for future work with more powerful hardware platforms. Extensive front track and flame extinction studies were performed to evaluate the performance of currently available non-iso-thermal simulators and to appraise their necessity in air injection processes. Comparative ISC field scale numerical simulation studies of Clair medium oil and light Australian petroleum were based on up-scaled combustion tube experimental results. These studies showed higher than expected hydrocarbon recovery in alternative EOR processes for both pre and post water flood implementation of ISC. Further in this study field scale numerical simulation studies revealed high incremental hydrocarbon recovery was possible by gravity assisted forced flow. The applicability of light oil ISC to gas condensate and sour petroleum reservoirs has been examined in this study with promising results. Light petroleum ISC implemented by a modified water flood including oxidants such as H2O2 and NH4NO3 are expected to widen the applicability of ISC processes in medium and light petroleum reservoirs, especially water flooded North Sea reservoirs.
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19

Lim, Rattanak. "Numerical and experimental study of creep of Grade 91 steel at high temperature." Paris, ENMP, 2011. https://pastel.hal.science/pastel-00687235.

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L'acier grade 91 serait un candidat approprié pour des éléments de structures du circuit secondaire et du générateur de vapeur des réacteurs nucléaires de génération IV. Leur durée de vie sera prolongée jusqu'à 60 ans. Cela nécessite de considérer les mécanismes actifs durant de très longs temps de fluage afin de proposer des prédictions de durées de vie plus fiable que de simples extrapolations. La striction est le mécanisme de ruine principal pour des durées de vie jusqu'à 160 kh à 500°C et 94 kh à 600°C. Une simulation de la striction tenant compte de l'adoucissement du matériau conduit à deux lois de bornes qui encadrent les durées de vie expérimentales d'un grand nombre d'aciers martensitiques revenus jusqu'à 200 kh à température 500-700°C. Des cavités intergranulaires observées en FEG-SEM à deux durées de vie longues affectent faiblement la vitesse de déformation. Une prédiction du développement des cavités permettrait d'extrapoler les durées de vie hors du domaine expérimental. Leur germination et croissance, supposées associées à la diffusion des lacunes, sont modélisées grâce à deux modèles classiques. Le premier tient compte d'une germination instantanée (Raj et Ashby) et le second d'une germination continue - Dyson. Le second, plus stable par rapport à ses paramètres que le premier, conduit à des prédictions des tailles finales de cavités en accord raisonnable avec les mesures en FEG-SEM. La vitesse de germination identifiée expérimentalement est requise dans ce modèle. La germination continue des cavités par diffusion est modélisée grâce au modèle classique de Raj. Ce modèle ne permet pas des prédictions de densité de cavités en accord avec les mesures, même en tenant compte de la germination aux interfaces matrice / précipités, observée au MEB-FEG et d'un facteur maximal de concentration de contrainte locale de 2. Ce dernier a été obtenu grâce à des calculs par éléments finis en déformations planes du fluage de microstructures simulées ou réelles, comprenant des points triples ou des précipités/phases de Laves. L'utilisation de la loi de germination de Dyson permet de proposer des prédictions au-delà de 200kh. La durée de vie prédite par le modèle de Riedel d'un essai à basse contrainte semble être en accord avec la durée expérimentale estimée de l'essai (toujours en cours) et actuellement en stade tertiaire, basée sur la fraction de la durée de vie habituellement consommée par le stade tertiaire
Grade 91 steel is a suitable candidate for structural components of the secondary and the vapour of generation IV nuclear reactors. Their in-service lifetime will last for 60 years. It is necessary to consider the mechanisms involved during long-term creep to propose reliable predictions of creep lifetimes. Necking is the main failure mode for creep lifetimes up to 160 kh at 500°C and 94 kh at 600°C. Necking modelling including the material creep softening leads to two bound equations including experimental lifetimes of a large number of tempered martensitic steels loaded up to 200 kh at temperature 500-700°C. The observed creep intergranular cavities are shown to affect very weekly creep strain rate. The prediction of the cavity evolution will allow estimating creep lifetimes out of experimental data domain. Their nucleation and growth, supposed to be associated to vacancy diffusion, are modelled using two classical models. The first one considers instantaneous nucleation (Raj and Ashby) and the second one continuous nucleation obeying the Dyson law (Riedel). The second one leads to two bound equations, more stable with respect to the parameter values. It allows predicting final size of cavities in reasonable agreement with measured ones. Yet, the nucleation rate should still be estimated from measured cavity densities. Nucleation of cavities by diffusion is simulated using the Raj model. This model does not allow predicted final cavity densities in agreement with the measured ones, even by considering cavity nucleation at precipitates/ Laves interfaces experimentally observed and the maximum local stress concentration of a factor 2 computed using finite element calculation in a 2D plane strain hypothesis based on either simulated or real microstructures containing triple points or precipitates/Laves phases. The use of the Dyson model allows us to propose predictions of long-term creep lifetimes. Lifetime predicted using the diffusion-induced growth model of one creep test under low stress still in progress is approximately in agreement with the experimental lifetime estimated based on the fraction of tertiary stage
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Sukdeo, Preeyanand. "CFD simulation of nuclear graphite oxidation / P. Sukdeo." Thesis, North-West University, 2010. http://hdl.handle.net/10394/4231.

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This study investigates the development of a strategy to simulate nuclear graphite oxidation with Computational Fluid Dynamics (CFD) to determine an estimate of graphite lost. The task was achieved by comparing the results of the CFD approach with a number of different experiments. For molecular diffusion, simulated results were compared to analytical solutions. Mass flow rates under conditions of natural convection were sourced from the 2002 NACOK experiment. Experimental data from the KAIST facility were sourced for the basic oxidation of graphite in a controlled environment. Tests included the reactions of carbon with oxygen and with carbon dioxide. Finally, the tests at NACOK from 2004 and 2005 were chosen for comparison for the simulation of oxidation. The 2005 test considered two reacting pebble bed regions at different temperatures. The 2004 test included multiple detailed structural graphite. Comparison of results indicated that the phenomenon of diffusion can be correctly simulated. The general trends of the mass flow rates under conditions of natural convection were obtained. Surface reaction rates were defined with user functions in Fluent. Good comparisons of the simulated and the KAIST experimental results were obtained. For the 2005 NACOK comparison, the pebble bed regions were simulated with a porous medium approach. Results showed that correct trends and areas of oxidation were estimated. The 2004 tests were with a combination of a porous medium and surface reaction approaches. More detailed oxidation experimental data would possibly improve the accuracy of the results. This research has shown that the CFD approach developed in the present study can identify areas of maximum oxidation although the accuracy needs to be improved. Both the porous and detailed surface reaction approaches produced consistent results. The limitations of the approach were discussed. These included transient phenomena which were estimated with steady state simulations, and the effects of change in geometry were not considered.
Thesis (M.Ing. (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2010.
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21

Specian, Valdir. "Clima e ambiente construído: análise da \"Predicting indoor air temperature formula\"." Universidade de São Paulo, 2003. http://www.teses.usp.br/teses/disponiveis/18/18139/tde-17112016-122244/.

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A previsão das condições térmicas de duas casas populares (ocupadas) na cidade de Descalvado-SP é tema deste trabalho. A pesquisa envolve o registro contínuo da variação das temperaturas interna e externa. A fórmula experimental, \"Predicting Indoor Air Temperature Formula\", proposta por Givoni (1999), está sendo aplicada e analisada para a previsão das temperaturas internas, máximas e mínimas. Para o registro contínuo das temperaturas, foi instalada no local uma estação meteorológica automática- CR10X- Campbell Scientific Inc., equipada com vários sensores para registro dos elementos do clima, e, também, por meio de multiplexador - AM416, de 32 canais, para conectar termopares - tipo T (cobre/constantan), que registram as temperaturas no interior das casas (ocupadas). Dos dados coletados, foram escolhidos 2 (dois) episódios representativos do clima, o primeiro representando a situação de primavera/verão (12 a 15/10/2000), e segundo, outono/inverno (14 a 20/05/2001), sendo analisados conforme a abordagem de análise dinâmica do clima, de acordo com a proposta de Vecchia (1997), adaptada de Monteiro (1967).
The forecast of the thermal conditions of two popular houses (busy) in the city of Descalvado - SP is therme of this work. The research involves the continuous registration of the variation of the internal temperatures and it expresses. The experimental formula \"Predicting Indoor Air Temperature Formulates\", proposed by Givoni (1999), it is being applied and analysed for the forecast of the internal temperatures, maxims and low. It goes the continuous registration of the temperatures it was installed un the place an automatic meteorological station - CR10X - Campbell Scientific Inc, equipped with sensor several, goes registration of the elements of the climate and also, through multiplexer - AM416, of 32 channels, to connect thermoocouples - type T(copper/constantan) that register the temperatures inside the houses (busy). Of the collected data they were chosen 2 (two) representative episodes of the climate, the first representing the spring/summer situation (12 to 15/10/2000) and second autumn/winter (14 to 20/05/2001), being analyzed according to the approach of dynamic analysis of the climate, in agreement with the proposal of Vecchia (1997) adapted of Monteiro (1967).
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22

Hwessa, Mahmod Mjahead. "Numerical Simulation Study: Air Injection Technique for Improved Oil Recovery (IOR) from Light Oil Reservoirs." Thesis, University of Bath, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.508714.

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23

Karaeren, Cenker. "Numerical Simulation Of Non-reacting Turbulent Flows Over A Constant Temperature Solid Surface In Regression." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609111/index.pdf.

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In this study, an attempt is made to obtain convergent and stable solutions of the K-E turbulence model equations for non-reacting turbulent flows over an isothermal solid surface in regression. A physics based mathematical model is used to describe the flow and temperature field over the moving surface. The flow is assumed to be two-dimensional, unsteady, incompressible with boundary layer approximations. Parabolized form of the standard K-E equations is adopted to simulate turbulence in the flow. Regression of the solid surface causes the bounds of the solution domain to change with time, therefore a coordinate transformation is used in the vertical direction. The computational domain with fixed boundaries is discretized using an orthogonal grid system where a coordinate stretching is used in the vertical direction. A second order accurate, explicit finite difference technique is used for discretization of the governing equations. The final set of discretized equations is then solved using a solution algorithm specifically developed for this study. The verification of the solution algorithm includes a grid independence study, time increment study, and a comparison of the steady state results for the laminar and the turbulent flow cases. Finally, a parametric study is conducted using the proposed solution algorithm to test the stability of the numerical results for different Reynolds numbers, regression rates, and surface temperatures. It is concluded that the proposed numerical solution algorithm is capable of providing convergent and stable solutions of the two-equation turbulence model.
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24

Wang, Luxin. "Simulation of pollutant transport in an urban area." Master's thesis, Mississippi State : Mississippi State University, 2002. http://library.msstate.edu/etd/show.asp?etd=etd-03292002-170455.

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25

Kerestes, Jared N. "Numerical Investigation of Flow Around a Deformed Vacuum Lighter-Than-Air Vehicle." Wright State University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=wright1622235951947085.

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26

Sohrabinia, Mohammad. "Estimation of the near-surface air temperature and soil moisture from satellites and numerical modelling in New Zealand." Thesis, University of Canterbury. Geography, 2013. http://hdl.handle.net/10092/8707.

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Satellite observations provide information on land surface processes over a large spatial extent with a frequency dependent on the satellite revisit time. These observations are not subject to the spatial limitations of the traditional point measurements and are usually collected in a global scale. With a reasonable spatial resolution and temporal frequency, the Moderate Resolution Imaging Spectroradiometer (MODIS) is one of these satellite sensors which enables the study of land-atmospheric interactions and estimation of climate variables for over a decade from remotely sensed data. This research investigated the potential of remotely sensed land surface temperature (LST) data from MODIS for air temperature (Ta) and soil moisture (SM) estimation in New Zealand and how the satellite derived parameters relate to the numerical model simulations and the in-situ ground measurements. Additionally, passive microwave SM product from the Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) was applied in this research. As the first step, the MODIS LST product was validated using ground measurements at two test-sites as reference. Quality of the MODIS LST product was compared with the numerical simulations from the Weather Research and Forecasting (WRF) model. Results from the first validation site, which was located in the alpine areas of the South Island, showed that the MODIS LST has less agreement with the in-situ measurements than the WRF model simulations. It turned out that the MODIS LST is subject to sources of error, such as the effects of topography and variability in atmospheric effects over alpine areas and needs a careful pre-processing for cloud effects and outliers. On the other hand, results from the second validation site, which was located on the flat lands of the Canterbury Plains, showed significantly higher agreement with the ground truth data. Therefore, ground measurements at this site were used as the main reference data for the accuracy assessment of Ta and SM estimates. Using the MODIS LST product, Ta was estimated over a period of 10 years at several sites across New Zealand. The main question in this part of the thesis was whether to use LST series from a single MODIS pixel or the series of a spatially averaged value from multiple pixels for Ta estimation. It was found that the LST series from a single pixel can be used to model Ta with an accuracy of about ±1 ºC. The modelled Ta in this way showed r ≈ 0.80 correlation with the in-situ measurements. The Ta estimation accuracy improved to about ±0.5 ºC and the correlation to r ≈ 0.85 when LST series from spatially averaged values over a window of 9x9 to 25x25 pixels were applied. It was discussed that these improvements are due to noise reduction in the spatially averaged LST series. By comparison of LST diurnal trends from MODIS with Ta diurnal trends from hourly measurements in a weather station, it was shown that the MODIS LST has a better agreement with Ta measurements at certain times of the day with changes over day and night. After estimation of Ta, the MODIS LST was applied to derive the near-surface SM using two Apparent Thermal Inertia (ATI) functions. The objective was to find out if more daily LST observations can provide a better SM derivation. It was also aimed to identify the potential of a land-atmospheric coupled model for filling the gaps in derived SM, which were due to cloud cover. The in-situ SM measurements and rainfall data from six stations were used for validation of SM derived from the two ATI functions and simulated by the WRF model. It was shown that the ATI function based on four LST observations has a better ability to derive SM temporal profiles and is better able to detect rainfall effects. Finally, the MODIS LST was applied for spatial and temporal adjustment of the near-surface SM product from AMSR-E passive microwave observations over the South Island of New Zealand. It was shown that the adjustment technique improves AMSR-E seasonal trends and leads to a better matching with rainfall events. Additionally, a clear seasonal variability was observed in the adjusted AMSR-E SM in the spatial domain. Findings of this thesis showed that the satellite observed LST has the potential for the estimation of the land surface variables, such as the near-surface Ta and SM. This potential is greatly important on remote and alpine areas where regular measurements from weather stations are not often available. According to the results from the first validation site, however, the MODIS LST needs a careful pre-processing on those areas. The concluding chapter included a discussion of the limitations of remotely sensed data due to cloud cover, dense vegetation and rugged topography. It was concluded that the satellite observed LST has the potential for SM and Ta estimations in New Zealand. It was also found that a land-atmospheric model (such as the WRF coupled with the Noah and surface model) can be applied for filling the gaps due to cloud cover in remotely sensed variables.
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Martínez, Ballester Santiago. "NUMERICAL MODEL FOR MICROCHANNEL CONDENSERS AND GAS COOLERS WITH AN IMPROVED AIR-SIDE APPROACH." Doctoral thesis, Universitat Politècnica de València, 2012. http://hdl.handle.net/10251/17453.

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La presente tesis se ha llevado a cabo en el Instituto de Ingeniería Energética de la Universitat Politècnica de València y durante una estancia en el National Institute of Standards and Technology (NIST). El objetivo principal de la tesis es desarrollar un modelo de alta precisión para intercambiadores de calor de microcanales (MCHX), que tiene que ser útil, en términos de coste computacional, para tareas de diseño. En la opinión del autor, existen algunos inconvenientes cuando los modelos existentes se aplican a algunos diseños recientes de intercambiador de calor, tales como MCHXs, bien de tubos en serpentín o en paralelo. Por lo tanto, la primera etapa de la tesis identifica los fenómenos que tienen el mayor impacto en la precisión de un modelo para MCHX. Adicionalmente, se evaluó el grado de cumplimiento de varias simplificaciones y enfoques clásicos. Con este fin, se desarrolló el modelo de alta precisión Fin2D como una herramienta para llevar a cabo la investigación mencionada. El modelo Fin2D es una herramienta útil para analizar los fenómenos que tienen lugar, sin embargo requiere un gran coste computacional, y por tanto no es útil para trabajos de diseño. Es por ello que en base a los conocimientos adquiridos con el modelo Fin2D, se ha desarrollado un nuevo modelo, el Fin1Dx3. Este modelo tan sólo tiene en cuenta los fenómenos más importantes, reteniendo casi la misma precisión que Fin2D, pero con una reducción en el tiempo de cálculo de un orden de magnitud. Se introduce una novedosa discretización y un esquema numérico único para el modelado de la transferencia de calor del lado del aire. Este nuevo enfoque permite modelar los fenómenos existentes de forma consistente con mayor precisión y con mucho menos simplificaciones que los modelos actuales de la literatura. Por otra parte, se logra un coste razonable de cálculo para el objetivo fijado. La tesis incluye la validación experimental de este modelo tanto para un condensador y un enfriador de gas. Con e
Martínez Ballester, S. (2012). NUMERICAL MODEL FOR MICROCHANNEL CONDENSERS AND GAS COOLERS WITH AN IMPROVED AIR-SIDE APPROACH [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/17453
Palancia
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Radosavljevic, Dejan. "The numerical simulation of direct-contact natural-draught cooling tower performance under the influence of cross-wind." Thesis, Imperial College London, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261786.

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29

Lebbin, Paul A. "Experimental and numerical analysis of air, tracer gas, and particulate movement in a large Eddy simulation chamber /." Search for this dissertation online, 2006. http://www.lib.umi.com/cr/ksu/main.

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30

Tholin, Fabien. "Numerical simulation of nanosecond repetitively pulsed discharges in air at atmospheric pressure : Application to plasma-assisted combustion." Phd thesis, Ecole Centrale Paris, 2012. http://tel.archives-ouvertes.fr/tel-00879856.

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In this Ph.D. thesis, we have carried out numerical simulations to study nanosecond repetitively pulsed discharges (NRPD) in a point-to-point geometry at atmospheric pressure in air and in H2-air mixtures. Experimentally, three discharge regimes have been observed for NRPD in air at atmospheric pressure for the temperature range Tg = 300 to 1000 K: corona, glow and spark. To study these regimes, first, we have considered a discharge occurring during one of the nanosecond voltage pulses. We have shown that a key parameter for the transition between the discharge regimes is the ratio between the connection-time of positive and negative discharges initiated at point electrodes and the pulse duration. In a second step, we have studied the dynamics of charged species during the interpulse at Tg = 300 and 1000 K and we have shown that the discharge characteristics during a given voltage pulse remain rather close whatever the preionization level (in the range 109-1011 cm��3) left by previous discharges. Then, we have simulated several consecutive nanosecond voltage pulses at Tg = 1000 K at a repetition frequency of 10 kHz. We have shown that in a few voltage pulses, the discharge reaches a stable quasi-periodic glow regime observed in the experiments. We have studied the nanosecond spark discharge regime. We have shown that the fraction of the discharge energy going to fast heating is in the range 20%- 30%. Due to this fast heating, we have observed the propagation of a cylindrical shockwave followed by the formation of a hot channel in the path of the discharge that expands radially on short timescales (t < 1 _s), as observed in experiments. Then we have taken into account an external circuit model to limit the current and then, we have simulated several consecutive pulses to study the transition from multipulse nanosecond glow to spark discharges. Finally the results of this Ph.D. have been used to find conditions to obtain a stable glow regime in air at 300 K and atmospheric pressure. Second we have studied on short time-scales (t_ 100_s) the ignition by a nanosecond spark discharge of a lean H2-air mixture at 1000 K and atmospheric pressure with an equivalence ratio of _ = 0:3. We have compared the relative importance for ignition of the fast-heating of the discharge and of the production of atomic oxygen. We have shown that the ignition with atomic oxygen seems to be slightly more efficient and has a completely different dynamics.
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31

Kubrak, Boris. "Direct numerical simulation of gas transfer at the air-water interface in a buoyant-convective flow environment." Thesis, Brunel University, 2014. http://bura.brunel.ac.uk/handle/2438/10196.

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The gas transfer process across the air-water interface in a buoyant-convective environment has been investigated by Direct Numerical Simulation (DNS) to gain improved understanding of the mechanisms that control the process. The process is controlled by a combination of molecular diffusion and turbulent transport by natural convection. The convection when a water surface is cooled is combination of the Rayleigh-B´enard convection and the Rayleigh-Taylor instability. It is therefore necessary to accurately resolve the flow field as well as the molecular diffusion and the turbulent transport which contribute to the total flux. One of the challenges from a numerical point of view is to handle the very different levels of diffusion when solving the convection-diffusion equation. The temperature diffusion in water is relatively high whereas the molecular diffusion for most environmentally important gases is very low. This low molecular diffusion leads to steep gradients in the gas concentration, especially near the interface. Resolving the steep gradients is the limiting factor for an accurate resolution of the gas concentration field. Therefore a detailed study has been carried out to find the limits of an accurate resolution of the transport for a low diffusivity scalar. This problem of diffusive scalar transport was studied in numerous 1D, 2D and 3D numerical simulations. A fifth-order weighted non-oscillatory scheme (WENO) was deployed to solve the convection of the scalars, in this case gas concentration and temperature. The WENO-scheme was modified and tested in 1D scalar transport to work on non-uniform meshes. To solve the 2D and 3D velocity field the incompressible Navier-Stokes equations were solved on a staggered mesh. The convective terms were solved using a fourth-order accurate kinetic energy conserving discretization while the diffusive terms were solved using a fourth-order central method. The diffusive terms were discretized using a fourth-order central finite difference method for the second derivative. For the time-integration of the velocity field a second-order Adams-Bashworth method was employed. The Boussinesq approximation was employed to model the buoyancy due to temperature differences in the water. A linear relationship between temperature and density was assumed. A mesh sensitivity study found that the velocity field is fully resolved on a relatively coarse mesh as the level of turbulence is relatively low. However a finer mesh for the gas concentration field is required to fully capture the steep gradients that occur because of its low diffusivity. A combined dual meshing approach was used where the velocity field was solved on a coarser mesh and the scalar field (gas concentration and temperature) was solved on an overlaying finer submesh. The velocities were interpolated by a second-order method onto the finer sub-mesh. A mesh sensitivity study identified a minimum mesh size required for an accurate solution of the scalar field for a range of Schmidt numbers from Sc = 20 to Sc = 500. Initially the Rayleigh-B´enard convection leads to very fine plumes of cold liquid of high gas concentration that penetrate the deeper regions. High concentration areas remain in fine tubes that are fed from the surface. The temperature however diffuses much stronger and faster over time and the results show that temperature alone is not a good identifier for detailed high concentration areas when the gas transfer is investigated experimentally. For large timescales the temperature field becomes much more homogeneous whereas the concentration field stays more heterogeneous. However, the temperature can be used to estimate the overall transfer velocity KL. If the temperature behaves like a passive scalar a relation between Schmidt or Prandtl number and KL is evident. A qualitative comparison of the numerical results from this work to existing experiments was also carried out. Laser Induced Fluorescence (LIF) images of the oxygen concentration field and Schlieren photography has been compared to the results from the 3D simulations, which were found to be in good agreement. A detailed quantitative analysis of the process was carried out. A study of the horizontally averaged convective and diffusive mass flux enabled the calculation of transfer velocity KL at the interface. With KL known the renewal rate r for the so called surface renewal model could be determined. It was found that the renewal rates are higher than in experiments in a grid stirred tank. The horizontally averaged mean and fluctuating concentration profiles were analysed and from that the boundary layer thickness could be accurately monitored over time. A lot of this new DNS data obtained in this research might be inaccessible in experiments and reveal previously unknown details of the gas transfer at the air water interface.
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32

Kullab, Alaa. "Desalination using Membrane Distillation : Experimental and Numerical Study." Doctoral thesis, KTH, Kraft- och värmeteknologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-44405.

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Desalination has been increasingly adopted over the last decades as an option, and sometimes as a necessity to overcome water shortages in many areas around the world. Today, several thermal and physical separation technologies are well established in large scale production for domestic and industrial purposes.  Membrane distillation is a novel thermally-driven process that can be adapted effectively for water desalination or water treatment in industrial applications, due to its potential lower energy consumption and simplicity. The general objective of this thesis is to contribute to the technical understanding of membrane distillation as a new technology in water treatment for both industrial and drinking water purposes, as a starting point for further improvement. The thesis includes experimental and numerical investigations that highlight some aspects of the technology application and fundamental aspects. In the field of industrial application, an experimental and numerical assessment has been carried out on an Air Gap Membrane Distillation (AGMD) prototype to assess the utilization of the technology in thermal cogeneration plants; in particular, demineralization of water boiler feed water and treating flue gas condensate. The main assessment parameters were water quality and energy consumption. The results from full-scale simulations of a system of 10 m3/hr production capacity,  connected to the district heating network were as follows: 5 to 12 kWh/m3 specific thermal energy consumption, and  0,6 to 1,5 kWh/m3 specific electricity consumption, depending upon the heat source (district heat supply line or low-grade steam). For desalination applications, experimental and simulation work was conducted on an AGMD semi-commercial system as part of the EU MEDESOL project. The aim was to evaluate AGMD performance with saline water of 35 g/l NaCl in order to establish an operation data base for simulation of a three-stage AGMD desalination system. Specific thermal energy consumption was calculated as 950 kWht/m3 for a layout without heat recovery, and 850 kWht/m3 for a layout with one stage heat recovery.  The lack of internal heat recovery in the current MD module means that most of the heat supplied to MD system was not utilized efficiently, so the thermal energy consumption is high. This would mean that a large solar field is needed. In order to analyze the flow conditions in feed flow and cooling channels, CFD was used as tool to analyze a spacer-obstructed flow channel for different types of spacer geometrical characteristics: flow of attack angle, spacer to channel thickness ratio, and void ratio. Velocity profiles, shear stress, and pressure drop were the main assessment criteria. Results show the flow of attack angle has a very minimum effect on the performance of spacers. The effect of spacer to channel thickness ratio was significant in all assessment parameters. Higher void ratios were found advantageous in promoting flow mixing, but resulted in lower sheer stress and hence reduced heat transfer. Physical modifications were implemented on a semi-commercial AGMD prototype to assess experimentally any improvement in its performance. These modifications were mainly focused on reducing the conductive heat transfer losses by modifying the physical support in the air gap that separates the membrane from the condensation surface. In addition, several feed channel spacers were tested and assessed based on their effect in increasing the mass transfer while maintaining or reducing pressure drop. The modifications yielded a two-fold augmentation: slight increase in the distillate mass flow rate (9-11%), and increased thermal efficiency (6%). The pressure drop in the module was reduced by 50% through selecting the appropriate spacer that would achieve the above mass flow rate increase.
QC 20111021
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33

Malizia, Fabio. "A numerical study of temperature effects on hot wire measurements inside turbulent channel flows." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amslaurea.unibo.it/5221/.

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A way to investigate turbulence is through experiments where hot wire measurements are performed. Analysis of the in turbulence of a temperature gradient on hot wire measurements is the aim of this thesis work. Actually - to author's knowledge - this investigation is the first attempt to document, understand and ultimately correct the effect of temperature gradients on turbulence statistics. However a numerical approach is used since instantaneous temperature and streamwise velocity fields are required to evaluate this effect. A channel flow simulation at Re_tau = 180 is analyzed to make a first evaluation of the amount of error introduced by temperature gradient inside the domain. Hot wire data field is obtained processing the numerical flow field through the application of a proper version of the King's law, which connect voltage, velocity and temperature. A drift in mean streamwise velocity profile and rms is observed when temperature correction is performed by means of centerline temperature. A correct mean velocity pro�le is achieved correcting temperature through its mean value at each wall normal position, but a not negligible error is still present into rms. The key point to correct properly the sensed velocity from the hot wire is the knowledge of the instantaneous temperature field. For this purpose three correction methods are proposed. At the end a numerical simulation at Re_tau =590 is also evaluated in order to confirm the results discussed earlier.
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34

Dib, Ghady. "Thermodynamic simulation of compressed air energy storage systems." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI092.

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Le développement des énergies renouvelables pose la question du stockage de l’énergie électrique. L’utilisation du stockage par air comprimé semble une solution prometteuse dans le domaine du stockage d'énergie : elle se caractérise par une grande fiabilité, un faible impact environnemental et une remarquable densité énergétique stockée (kWh/m3). Jusqu’à présent, l'air comprimé a été utilisé dans de nombreux domaines comme vecteur d’énergie pour stocker différentes formes d'énergies (transport routier, poste pneumatique, plongée sous-marine). Néanmoins, actuellement de nombreux chercheurs se concentrent sur le développement de stockage d'énergie par air comprimé (CAES) à petite échelle couplé à une application de bâtiment en se basant sur les travaux développés pour les multiples systèmes de CAES à grande échelle installés dans le monde. Un modèle numérique global du système de stockage par air comprimé à petite échelle, couplé à un modèle de bâtiment et à des modules d’énergie renouvelable a été développé dans le but de modéliser différents compresseurs/détendeurs et structures d’installation développés par plusieurs startups (LightSail Energy et Enairys Powertech) et chercheurs. Les compresseurs et détendeurs adiabatiques ont d’abord été sélectionnés pour étudier le système de trigénération de stockage d'énergie par air comprimé adiabatique avancé (AA-CAES) couplé au bâtiment et aux réseaux avec les différents scénarios décrits ci-dessus. Les compresseurs et détendeurs quasi-isothermes développés par LightSail Energy et Enairys Powertech ont été modélisés pour chaque phase de la compression et de la détente. Ces modèles analytiques ont permis une meilleure compréhension du fonctionnement principal de ces technologies et d'avoir l’ordre de grandeur de différents paramètres physiques. Les systèmes I-CAES et AA-CAES sont comparés d'un point de vue financier en se référant à une analyse du marché des systèmes de production/utilisation de l'air comprimé. Trois prototypes différents ont été étudiés: deux systèmes AA-CAES (idéal et virtuel (basés sur des unités commerciales trouvées sur le marché de l'air comprimé)) et un système I-CAES (basé sur le prototype LightSail Energy CAES)
In the context of developing renewable energies, storing energy improves energy efficiency and promotes the insertion of intermittent renewable energies. It consists of accumulating energy for later use in a place that may be the same or different from the place of production. Converting electrical energy to high-pressure air seems a promising solution in the energy storage field: it is characterized by a high reliability, low environmental impact and a remarkable stored energy density (kWh/m3). Currently, many researchers are focusing on developing small scale of the compressed air energy storage system (CAES) coupled to a building applications based on the work done for multiple large scale CAES systems installed in the world. A global numerical model of trigeneration CAES system coupled to a building model and renewable energy modules was developed in order to analyze the CAES system behavior responding to electrical, hot and cold energy building demand. Different energy scenarios (autonomous and connected to the grid modes), geographical locations and building typologies were proposed and analyzed. The CAES numerical model development is based on solving energy and heat transfer equations for each system component (compressor/expander, heat exchanger, high pressure air reservoir, thermal water storage tank). Adiabatic compressor and expander were firstly selected to investigate the trigeneration advanced adiabatic compressed air energy system (AA-CAES) coupled to the building and to grids with the different scenarios described above. Similar to adiabatic components, quasi-isothermal compressor and expander developed by LightSail Energy and Enairys Powertech were also analyzed by solving the energy and heat transfer equations for each phase of the compression and expansion processes. These analytical models allowed us to have a better understanding of these technologies operations and to have several orders of magnitudes of different physical parameters. I-CAES and AA-CAES were also compared from a financial point of view based on compressed air market analysis. Three different prototypes were studied: Two AA-CAES systems (ideal and virtual (some of which are based on commercial units found in the compressed air market)) and one I-CAES system (based on LightSail Energy CAES prototype)
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35

Ragothaman, S. "Numerical Simulation Of Nocturnal Temperature Profiles." Thesis, 1996. https://etd.iisc.ac.in/handle/2005/1579.

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36

Ragothaman, S. "Numerical Simulation Of Nocturnal Temperature Profiles." Thesis, 1996. http://etd.iisc.ernet.in/handle/2005/1579.

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37

Manna, Vivek. "Numerical Simulation of Air-Lift Pump." Thesis, 2015. http://ethesis.nitrkl.ac.in/7941/1/2015_BT_Numerical_Manna.pdf.

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Now a days, it is a basic necessity to have a very highly reliable pump with low maintenance. Moreover, for pumping of various kind of fluid like corrosive, abrasive, or even radioactive, an air-lift pump is very much useful. The only negative point of the ALP is that it has very low efficiency. Therefore, the goal is to perform an exhaustive research to increase the performance of the air-lift pump. The purpose of the present effort is to capture the performance of air lift pump when it is operated in different flow regimes. To fulfill this objective, an air-lift pump is designed and numerically simulated using commercial software ANSYS. The results produced have been validated with the experimental data and have found to be in accordance with it. The pump works under two-phase flow condition with air and water as the two phases. Simulations were performed by varying the air mass flow rates. It is inferred that AMFR played a dominant role in improving the pump’s performance and efficiency. It is concluded that for obtaining a good efficiency in an ALP, it should be operated either in slug or slug-churn flow regime.
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38

Tasi, Cheng-Zhi, and 蔡承志. "Numerical Simulation of the air intake system." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/62271458030773937475.

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碩士
國立交通大學
機械工程系所
101
Originally designed are simple outside air into the air-conditioned units to make adjustments in the system design of the air-conditioned units. This method because of they are usually a large gap between the outside air conditions and indoor conditions, it often takes a lot of energy to achieve the required conditions. Changes designed using the circulating air and the outside air mixed before entering the adjustment of air-conditioned units, you can save equipment space and the state of the circulating air is almost the same as the indoor state, so be able to use the thermal energy of the circulating air with fresh air mixed, significantly reducing the heater power. In this study, the mixed air conditioning units use adjust the amount of fresh air and circulating air configuration, and in maintaining air quality, the required minimum amount of ventilation, the analysis of the ice-water coil cooling and dehumidifying of the air-conditioned units, heated by a heater and fan use energy consumption. The final objective is to monitor the outdoor ambient temperature, humidity and set indoor environmental conditions can quickly calculate the optimal design of energy - saving configuration to achieve practical results.
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39

Tsao, Shu-Ming, and 曹書銘. "Numerical Simulation of Air Sparging with TMVOC." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/73497458995895914224.

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碩士
國立交通大學
土木工程系所
102
The number of gas stations in Taiwan increased dramatically after the government lifted the ban on private ownership. However, the gas stations account for a large proportion of the soil and groundwater pollution sites. Leakage from storage tanks and pipelines accounts for the two major sources from which petroleum releases into the subsurface. Air sparging is one of the most commonly adopted in-situ remediation technology to clean up polluted groundwater in gas station sites. Its mechanism is to inject air into underground water where the dissolved constituents partition to vapor phase as they come into contact with the injected air. However, many pollution remediation technologies are difficult to be applied in cases of complicated soil structure. For example, it’s difficult for contaminants to transport within fine-grained soils. This research focuses on two-layered strata, with shallow layer of fined grained soil on top of groundwater table and a layer of sandy soil beneath. A numerical model software called TMVOC is used to simulate air sparging in a model site with the above mentioned geological condition. Four independent variables which controlled the effect of remediation are discussed separately. These variables include, the air injection rate, the vapor extraction rate, the distance between spill point and extraction wells, and the different AS well layout schemes. In addition, the remediation at a model site with homogeneous sandy soil was also as simulated for comparison. The results show that greater air injection rate contributes significantly to efficiency of remediation of aqueous benzene, but increasing air injection rate or vapor extraction rate are less beneficial to removing residual petroleum products in the vadose zone. As SVE well gets closer to the spilling point, the pressure gradient around the contaminants increases, which helps remediate dissolved benzene and total petroleum hydrocarbon (TPH) in practice. The plume expands in the beginning of the air sparging because dissolved constituents are unable to partition to vapor phase in a short time, which happens in all cases. It’s necessary to consider the risk of migrating of contamination during remediation. In all the cases with heterogeneous soil, the vadose zone cannot be cleaned up successfully within reasonable time.
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40

Machuca, Carlos Rodrigo Basagoitia, and 羅宇. "Numerical Simulation for Ejector Type Air Conditioner System." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/66758006700370890259.

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碩士
崑山科技大學
機械工程研究所
98
Air conditioners are widely used around the world, and it’s also a contributor to environmental problems as the well known global warming due to its high energy consumption. For this reason this paper is dedicated to the study of an alternative for the compressor based air conditioner, which is the ejector based air conditioner; which has been previously studied only with one-dimensional numerical analyses. This paper presents numerical analyses for the study of the ejector nozzle of a solar aided ejector-based air conditioner system which uses water as working fluid. Analyses of steady-state computational fluid dynamics (CFD) were conducted in order to corroborate and optimize the results of previous one dimensional studies in a three dimensional simulation. This enables a more realistic approach by taking into consideration a parametric study of different geometries and non-linear water properties. Several valuable discoveries were found through the simulation, ‧ Optimal conditions of geometry for known mass flow rates and temperatures were found. ‧ Different dimensions of the nozzle were found as optimal for the same conditions proposed in previous literature. ‧ It was also proven that geometries and initial conditions, proposed in other literature, don’t always yield physically reasonable results. This work can serve as guidelines for future designs of ejector nozzles for use in air conditioner systems that employ water as working fluid.
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41

Liao, Chun-Yi, and 廖純宜. "Numerical Simulation for Temperature Effect on Cardiac Electrophysiological." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/71902662229739431878.

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碩士
靜宜大學
應用數學研究所
98
At low temperature, the human cardiac ionic mechanism will be affected, and may produce arrhythmia and atrial fibrillation under certain condition. In our study, we used the rabbit atrial cell model developed by D.S.LindBlad (1996) to proceed numerical simulation. The main advantage for numerical simulation is that we can modify the time constant and conductance of ion channels corresponding to temperature changes to investigate the resulting physiological phenomenon. The numerical results for single cell are discussed.
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42

Chang, Shu-Kang, and 張書綱. "Numerical Simulation of Microtube Flows with Temperature Effect." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/67550538256608708504.

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碩士
淡江大學
航空太空工程學系碩士班
94
The objective of this research is to use numerical simulation program to analyze fluid mechanics and heat transfer characteristics in three dimensional micro-tubes of incompressible water-liquid. Three dimensional micro-tubes simplified into two dimensional axis-symmetric of x-r plane field is to facilitate the computing process of the program, and then only the boundary-layer equation needs estimating. Because this equation has the character of parabolic type in mathematics, it could provide a very accurate and powerful tool for computing fluid mechanics and heat transfer characteristics in micro-tubes after fully developed region. At the time being, comparing with the general computer devices, simulating the program is much faster than the traditional Navier-Stokes equation hundreds of times. The scholars in the references said that there are usually some differences in measurement and analysis between different experiments and numerical analysis. All of these main influences are due to temperature effects, compressibility effects, rarefaction effects, viscous dissipation effects, Electro-osmotic effects, channel surface conditions, experiment errors and so on. Therefore, temperature effects are considered the main point in the research. Because of the change of temperature, the basic physical properties in fluid, such as density, conductivity and viscosity, will be affected. If temperature changes, they change, and even directly affect the differences of pressure, velocity and temperature in the flow field by considering temperature effects or not. For thermal boundary condition, it divides into isothermal wall temperature and constant heat flux on the wall in micro-tubes. Under discussing two parts of thermal boundary condition, to investigate Nusselt number and the relationship between friction factor and Reynolds number first, and then verify with heat transfer characteristics of traditional size. According to the values of Nusselt number and f*Re from the program, the contracting error is very small with experimental formula of traditional size. This verification means that the research in using boundary-layer equation with micro-tubes simulating analysis, is truly an accurate numerical simulation equation. Without temperature effects, all the values of Nusselt number and f*Re would conform to fluid mechanics and heat transfer characteristics in traditional size; but if considering temperature effects, Nusselt number would be higher than traditional heat transfer characteristics, and f*Re would raise following to the increasing diameter. Besides, this research also discusses the fluid mechanics and heat transfer characteristics in different diameter and Reynolds number in micro-tubes without considering temperature effects.
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43

ChingDianTzeng and 曾慶典. "Numerical Simulation of Temperature Rise for Electrical Motor." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/45247543349598280734.

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碩士
淡江大學
航空太空工程學系
90
The title of this thesis is simulate temperature rise for electrical motor by numerical methods.First we simulate component of electrical moter separately,containing outer fan,cover and fin.Then we combine three components simulating electrical motor working under standard condition. The reason of this research is saving time and money.Flow rate and temperature rise for electrical motor usually defined by measuring motor directly.When changing motors dimensions,it needs to open mold and manufacture again,wasting time and money.We can save time and money by changing component''s dimension and computing flow rate and temperature rise using numerical methods. In this thesis we use STAR-CD to analyze motor.The numerical methods of this software is finite volume method(F.V.M), computing points of fluid in flow field are at centers of cell,every cell performing computation repeatedly until all cells arrive convergence criteria. Individually analyzing,for outer fan we remove cover and giving an inlet region and outlet region to test two items:(1)Giving pressure difference to compute flow rate;(2)Giving flow rate to compute pressure difference. In this section we select two type of outer fan to perform analysis.We discuss relations between different porosity area ratio and local drag coeffic- ient(pressure drop coefficient),and using porous media replace baffle plate.We analyzing cold flow field of fin,computing velocity drop of fluid passing gap of fin.We select two type of fin to perform analysis,comparing them with different dimensions but similar geometries,whom have better performance.At last,we combine outer fan,cover replace with porous media and fin,computing flow rate and pressure drop across fin under given rotating velocity and boundary conditions. Results shows that,computation of outer fan at different boundary conditions to get flow rate or pressure difference,whose error can decrease in a tolerance range;porous media can create a pressure drop which we want by giving proper porous coefficients,so we can replace actual cover by porous media;fin has better performance which has longer length and shorter fin height.When using combined model’s simulating mass flow,which error also in a tolerance range.
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44

LIN, CHIEN-CHOU, and 林建州. "Development and numerical simulation of personal mini air cooler." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/96479392055443630653.

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碩士
國立臺南大學
綠色能源學科技學系碩士在職專班
105
Due to global climate change and the problem of global warming is getting worse, cause the environment which we live come to hot more and more. With the gradual reduction of the Earth's energy, we are faced with hot and energy shortages. Even the traditional air-conditioning system can bring us cool and comfortable, but it cost a lot of electricity .In this year, mini air cooler is gradually welcomed in the market. Its small size and low power consumption, suitable for use in small areas and the open space which the air conditioner can’t be installed. In this study, the heat pipes were used to combine with the aluminum fins module, with the Thermoelectric Cooling Module (TEC) to design a mini air cooler. The target is to design the effect that the air outlet temperature is 5°C lower than the ambient temperature. COMSOL Multiphysics was used to simulate the cooling effect and the flow field first. Then through the actual production of experimental model and test its performance. The simulation and experimental results were verified. The simulation results show that the average temperature of the air outlet of is 24.2°C and the average wind speed of the outlet is 2.9 m/s at an ambient temperature of 30.0°C. The experimental results show that the average temperature of the outlet is 24.8°C, and the average wind speed of the outlet is 2.47 m/s .The outlet temperature can be reduced to the steady state 24.8 ± 0.1 ° C within 4.5 minutes after the start-up operation.
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45

Hsu, Wei-Chieh, and 許威傑. "Numerical Simulation Analysis of High Temperature Heat Exchange Module." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/x8wcg4.

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碩士
國立屏東科技大學
車輛工程系所
105
In this study,CFD (Computational Fluid Dynamics) ANSYS / FLUENT software is used to establish a high temperature regenerative combustion system of the regenerator heat flow simulation analysis module and gradually accumulate the design parameters of the regenerator database to provide domestic industry process regenerative combustion system custom design capabilities. It is accurate method to simulate and design a regenerator module with CFD. However, due to the large number of meshes, it is impossible to simulate the full-size regenerator module. The solution of this study use the porous medium model instead of the regenerator, not only building is simple, but also can significantly reduce the calculation time, and porous medium coefficient (convection coefficient and friction coefficient )can be obtained by CFD numerical experiments. Results of the study, porous medium model can replace the real model, and the maximum error is within 7%. When the high temperature exhaust gas and fresh air enter the heat storage tank, the flow field is not uniform. As the gap increases, the temperature efficiency and waste heat recovery rate are lower.
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46

Huang, Chung-Sheng, and 黃鈞聖. "Numerical Simulation on Temperature Unifomity of Large-Scale High-Temperature Chamber Flow Field." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/43680160705607481435.

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碩士
中華大學
機械工程學系碩士班
97
Large-Scale High-Temperature Chamber applies in the industrial field more 20 years , having been existing temperature Uniformity will effect good yield argue of process on maximum space to use effectively of equipment inside cabinet.Particularly the industrial production line guide in more vendor of high-temperature chamber for mass-produce , even appear 4%~ 20% loss-yield and defect loss of high ratio difference in the same work order of product.Thereupon ,how to improve the design of flow field on Temperature uniformity of Large-Scale high-temperature chamber to be very important. This thesis use as experiment measurement and 5 simulation steps of transient numerical analyze mode,inquiring into a discrepancy on difference part-assembly design in temperature uniformity of large-scale high-temperatrue chamber ( V=23.2 m3 ),equipment temperature rise capability and econom-izes on energy. Consequently Discover (1) the A fan-way design of the experiment equipment matching digital program controller,temperature unifomity could control in ± 2℃of GB national standard and can obtain to conform the High definition control of sequentias. (2) Fan-way design pattern of equipment is biggest item to effect equipment temperature rise capability, sequence item is change design on fan-box size and location place.(3) Compare E fan-way of equipment vender, A fan-way design could save 80% consume quantity of electricity.(4) wrong design and application of resistance on supply-way tuyere and return-way tuyere of Fan-box will reduce the equipment temperature rise capability. The thesis have succeed to crating application technology of Numerical Simulation with Flovent software, in Temperature Uniformity of Large-Scale high-temperature chamber field. The Numerical Simulation mode and study result, can be used as the equipment vendor to apply Numerical Simulation technological development new equipment( or improve previously design) and apply the reference of the best manufacturing process equipment application of industrial user. Keywords: Large-Scale High-Temperatue Chamber, Temperature Uniformity, Numerical Simulation of Flow Field
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47

Chen, Liang-Ming, and 陳良銘. "Numerical Simulation of Air Knife Chamber for LCD Glass Subtrate." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/93998476128769271178.

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碩士
國立彰化師範大學
機電工程學系
97
In the TFT-LCD process, the cleaning process possesses a large proportion to the yield rate on account of the exterior cleanliness of the substrate will affect the result of coating or the coating thickness and thickness uniformity. The topic of this research is the air-knife module, the following portion of the wet cleaner to glass substrate. Applying the numerical simulation based on the object of the original scheme, with the accomplishment of the design, exploits computational clinical software to build numerical model entities and discusses the glass substrates under different internal flow fields in the air knife module in order to identify any need for design alteration. Enabling to predict the dynamic direction of the internal fluid in the system is far considerable towards the air knife of glass substrate layout. The air knife module of the glass substrate is mainly composed of two units air knifes, and removes the thin water film to dry on the plate surface. Synchronously, several air inlets and outlets are on the top and down position in this air-dry structure to keep the fluent inner flow field, sweep the particles smoothly in order to maintain the cleanness of the glass substrate after drying. By the simulation analysis before manufacturing the 7.5 generation equipment and the numerical simulated experience of the air knife chamber, the numerical results demonstrates the reference to the machine production and the basis to adjust and trial. These sequential parameters will offer to retrench the cost of developing large-sized dryer, repeated trial and reduplicative error on time and man power in order to elevate the competitiveness of domestic industries.
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48

Ma, Rong-Hua, and 馬榮華. "Numerical Simulation and Performance Study of Positive Displacement Air Boosters." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/79937144159766067270.

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博士
國立臺灣大學
機械工程學研究所
88
This thesis develops a comprehensive theoretical analysis for predicting the performance of positive displacement boosters. First, the numerical results show good agreements compared with experimental data from the manufacturer. Second, the influences of design parameters on positive displacement booster's performance are theoretically investigated. Based on thermal fluid theory, a physical model considering the effects of suction, discharge, dynamic loss, heat transfer, and leakage is described. By control volume concept, a set of differential equations was derived to the specific compressed chamber. The temperature and pressure of working fluid in the chamber could be simplified into one-dimensional equations depending on rotational angle only. The conservation equations for working gas, oil (or water) were solved by using a Runge-Kutta integration algorithm. Through the numerical results, the simulation program can further be used to discuss the compression work, compression efficiency and other parameters such as oil(or water)-injection temperature、oil (or water)-injection quantity, and etc. The numerical results in the present study show good reliability compared with those in the literature, and the results also agree well with experimental data. The theoretical model can be served as a powerful tool in estimating the performance when the new type of booster designing in future studies.
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49

Chih-ChiehKu and 古智杰. "Numerical Simulation of Flow Field in Air Leakage Test Furnace." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/82696825836115735130.

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碩士
國立成功大學
航空太空工程學系
102
The goal of paper uses ANSYS CFX to investigate the fluid fields in air leakage test furnace. We investigate the relationship among temperature trends and the turbine rotational speed, electric heating pipe temperature. In the simulation, we use high resolution scheme and K-Epsilon turbulence model to solve the incompressible Navier-Stokes equations. The mixed grid system which combines Hexahedral and prism meshes is used. First, several test problems, 3-D cavity flow; natural convection; and air leakage test for a plate with a hole, are simulated to understand the capability of the commercial program about the air leakage test. The numerical results are compared well with the experimental data performed by NCKU Fire Safety Research Center. Finally, the flow field and temperature in the furnace are investigated in detailed. We find out that the design angle and rotation speed of wind turbine are very important parameter to elevate temperature in the furnace. INTRODUCTION Fires often cause casualties due to smoke and heat. Heat is the most frightening factors. How to effectively control the proliferation of fire and smoke is very important issue. Fire doors are used to prevent the spread of smoke within a certain time. Basically a fire door testing may spend hundreds of thousands. Using ANSYS CFX can predict the performance of door and save. The goal of paper is to simulate the fluid field in air leakage test furnace by using ANSYS CFX. We investigate the temperature trends by changing the turbine rotational speed and electric heating pipe temperature. RESULTS AND DISCUSSION In the simulation, we use high resolution scheme and K-Epsilon turbulence model to solve the incompressible Navier-Stokes equations. The mixed grid system which combines Hexahedral and prism meshes is used. First, several test problems, 3-D cavity flow; natural convection; and air leakage test for a plate with a hole, are simulated to understand the capability of the commercial program. About the air leakage test, the numerical results are compared well with the experimental data performed by NCKU Fire Safety Research Center. Finally, the flow field and temperature distribution in the furnace are investigated in detailed. CONCLUSION The gas flow is roughly trend by buoyancy and wind turbine design. Heat will accumulate at the right part and are mainly affected by the wind turbine position. We find out that the design angle and rotation speed of wind turbine are very important parameter to elevate temperature in the furnace. In the furnace, temperature trends by wind turbine and heating pipes. Some lower temperature gas was caused by the door and the gas flowing through the electro-thermal tube. The air flow speed is so fast that heating electro-thermal tube can not effectively heating.
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50

Ghobadi, Bigvand Arian. "Numerical simulation of transient liquid phase bonding under temperature gradient." 2013. http://hdl.handle.net/1993/21969.

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Transient Liquid Phase bonding under Temperature Gradient (TG-TLP bonding) is a relatively new process of TLP diffusion bonding family for joining difficult-to-weld aerospace materials. Earlier studies have suggested that in contrast to the conventional TLP bonding process, liquid state diffusion drives joint solidification in TG-TLP bonding process. In the present work, a mass conservative numerical model that considers asymmetry in joint solidification is developed using finite element method to properly study the TG-TLP bonding process. The numerical results, which are experimentally verified, show that unlike what has been previously reported, solid state diffusion plays a major role in controlling the solidification behavior during TG-TLP bonding process. The newly developed model provides a vital tool for further elucidation of the TG-TLP bonding process.
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