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Kucuk, Sinan. "A Comparative Investigation Of Heat Transfer Capacity Limits Of Heat Pipes." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12609125/index.pdf.
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Heat pipe is a passive two phase device capable of transferring large rates of heat with a minimal temperature drop. It is a sealed tube with a wick structure lined in it and with a working fluid inside the tube. It consists of three parts: an evaporator, a condenser and an adiabatic section. The heat pipes are widely used in electronics cooling and spacecraft applications. Although they can transfer large rate of heat in a short range, they have operating limits, namely: the capillary limit, the viscous limit, the entrainment limit, the sonic limit and the boiling limit. These limits determine the heat transfer capacity of the heat pipe. The properties of the working fluid, the structure of the wick, the orientation of the pipe, the length and the diameter of the tube etc. are the parameters that affect the limits. In this study, an analytical 1-D heat pipe model is formed and a computer code is prepared in order to analyze the effects of the parameters on the heat transfer capacity of a heat pipe. Water, Ammonia and Mercury are investigated as working fluids for different operating temperature ranges. The software is tested for a typical application for each working fluid.
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Gdhaidh, Farouq A. S. "Heat Transfer Characteristics of Natural Convection within an Enclosure Using Liquid Cooling System." Thesis, University of Bradford, 2015. http://hdl.handle.net/10454/7824.
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In this investigation, a single phase fluid is used to study the coupling between natural convection heat transfer within an enclosure and forced convection through computer covering case to cool the electronic chip. Two working fluids are used (water and air) within a rectangular enclosure and the air flow through the computer case is created by an exhaust fan installed at the back of the computer case. The optimum enclosure size configuration that keeps a maximum temperature of the heat source at a safe temperature level (85℃) is determined. The cooling system is tested for varying values of applied power in the range of 15−40𝑊.
The study is based on both numerical models and experimental observations. The numerical work was developed using the commercial software (ANSYS-Icepak) to simulate the flow and temperature fields for the desktop computer and the cooling system. The numerical simulation has the same physical geometry as those used in the experimental investigations. The experimental work was aimed to gather the details for temperature field and use them in the validation of the numerical prediction.
The results showed that, the cavity size variations influence both the heat transfer process and the maximum temperature. Furthermore, the experimental results
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compared favourably with those obtained numerically, where the maximum deviation in terms of the maximum system temperature, is within 3.5%. Moreover, it is seen that using water as the working fluid within the enclosure is capable of keeping the maximum temperature under 77℃ for a heat source of 40𝑊, which is below the recommended electronic chips temperature of not exceeding 85℃. As a result, the noise and vibration level is reduced. In addition, the proposed cooling system saved about 65% of the CPU fan power.
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Gdhaidh, Farouq Ali S. "Heat transfer characteristics of natural convection within an enclosure using liquid cooling system." Thesis, University of Bradford, 2015. http://hdl.handle.net/10454/7824.
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In this investigation, a single phase fluid is used to study the coupling between natural convection heat transfer within an enclosure and forced convection through computer covering case to cool the electronic chip. Two working fluids are used (water and air) within a rectangular enclosure and the air flow through the computer case is created by an exhaust fan installed at the back of the computer case. The optimum enclosure size configuration that keeps a maximum temperature of the heat source at a safe temperature level (85°C) is determined. The cooling system is tested for varying values of applied power in the range of 15-40W. The study is based on both numerical models and experimental observations. The numerical work was developed using the commercial software (ANSYS-Icepak) to simulate the flow and temperature fields for the desktop computer and the cooling system. The numerical simulation has the same physical geometry as those used in the experimental investigations. The experimental work was aimed to gather the details for temperature field and use them in the validation of the numerical prediction. The results showed that, the cavity size variations influence both the heat transfer process and the maximum temperature. Furthermore, the experimental results ii compared favourably with those obtained numerically, where the maximum deviation in terms of the maximum system temperature, is within 3.5%. Moreover, it is seen that using water as the working fluid within the enclosure is capable of keeping the maximum temperature under 77°C for a heat source of 40W, which is below the recommended electronic chips temperature of not exceeding 85°C. As a result, the noise and vibration level is reduced. In addition, the proposed cooling system saved about 65% of the CPU fan power.
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Zhang, Yufang. "Coupled convective heat transfer and radiative energy transfer in turbulent boundary layers." Phd thesis, Ecole Centrale Paris, 2013. http://tel.archives-ouvertes.fr/tel-00969159.
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If radiation plays an important role in many engineering applications, especially in those including combustion systems, influence of radiation on turbulent flows, particularly on the turbulent boundary layers, is still not well known. The objective is here to perform a detailed study of radiation effect on turbulent flows. An optimized emission-based reciprocal (OERM) approach of the Monte-Carlo method is proposed for radiation simulation using the CK model for radiative gas properties. OERM allows the uncertainty of results to be locally controlled while it overcomes the drawback of the original emission-based reciprocity approach by introducing a new frequency distribution function that is based on the maximum temperature of the domain. Direct Numerical Simulation (DNS) has been performed for turbulent channel flows under different pressure, wall temperatures and wall emissivity conditions. Flow field DNS simulations are fully coupled with radiation simulation using the OERM approach. The role of radiation on the mean temperature field and fluctuation field are analyzed in details. Modification of the mean temperature profile leads to changes in wall conductive heat fluxes and new wall laws for temperature when radiation is accounted for. The influence on temperature fluctuations and the turbulent heat flux is investigated through their respective transport equations whose balance is modified by radiation. A new wall-scaling based on the energy balance is proposed to improve collapsing of wall-normal turbulent flux profiles among different channel flows with/without considering radiation transfer. This scaling enables a new turbulent Prandtl number model to be introduced to take into account the effects of radiation. In order to consider the influence of radiation in the near-wall region and predict the modified wall law, a one-dimensional wall model for Large Eddy Simulation (LES) is proposed. The 1D turbulent equilibrium boundary layer equations are solved on an embedded grid in the inner layer. The obtained wall friction stress and wall conductive flux are then fed back to the LES solver. The radiative power term in the energy equation of the 1D wall model is computed from an analytical model. The proposed wall model is validated by a comparison with the former DNS/Monte-Carlo results. Finally, two criteria are proposed and validated. The first one is aimed to predict the importance of wall radiative heat flux while the other one predicts whether a wall model accounting for radiation in the near wall region is necessary. A parametric study is then performed where a k-ǫ model and a turbulent Prandtl number model are applied to simulate the velocity and temperature field of different channel flows under various flow conditions. The obtained criteria values are analyzed and compared.
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Said, Frédérique. "Etude expérimentale de la couche limite marine : structure turbulente et flux de la surface (expérience TOXANE-T)." Toulouse 3, 1988. http://www.theses.fr/1988TOU30022.
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Le travail presente est une etude experimentale des transferts turbulents de chaleur, humidite et quantite de mouvement dans la couche limite marine. La phase experimentale (experience toscane-t) s'est deroulee en mars 1985, au large de la baie d'audierne (finistere). Le principal vecteur utilise pour le travail presente est un avion instrumente pour la physique de l'atmosphere. Ce moyen a permis de determiner une topographie des caracteristiques turbulentes, sur une echelle horizontale de l'ordre de 50km sur 50km, et de calculer les flux par la methode des correlations. Les conditions experimentales rencontrees correspondent a des vents compris enre 3 et 12 metres par seconde et a des conditions d'instabilite caracterisees par des longueurs de monin obukhov negatives comprises entre 50 et 300 metres. La structure turbulente de la couche limite marine est presentee dans le cadre de la theorie de similitude. Les resultats obtenus sont en accord avec les donnees acquises en couche limite dynamique, marine ou continentale. Ils sont egalement compares aux caracteristiques turbulentes des couches limites convectives. La finalisation de cette etude est resumee au moyen d'une parametrisation des flux de surface. Celle-ci est utilisable dans les modeles de grande echelle et consiste a calculer les coefficients aerodynamiques. Dans les conditions experimentales de l'etude les valeurs obtenues sont les suivantes: 1. 8 10**(-3) pour la quantite de mouvement (cd::(10)); 1. 5 10**(-3) pour la chaleur sensible (ct::(10)); et 1. 5 10**(-3) pour la chaleur latente (cq::(10)); ces coefficients sont independants de l'echelle d'integration spatiale a laquelle ils ont ete determines (de 5 km sur 5 km a 50 km sur 50 km).
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Stefanini, Luciano Martinez. "Efeitos da camada limite térmica na formação de gelo em aerofólios de uso aeronáutico." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/3/3150/tde-17082009-165521/.
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O modelo de avaliação da camada limite dinâmica e térmica foi implementado, no presente trabalho, em um código numérico para o cálculo do coeficiente de transferência de calor convectivo sobre aerofólios de uso aeronáutico com formação de gelo. Foram considerados, no modelo da camada limite turbulenta, os efeitos da rugosidade equivalente do grão de areia ks, e transição entre o regime laminar e turbulento foi avaliada por dois modelos, um abrupto e um suave. Para a transição suave foi utilizada uma função intermitência proposta por (ABU-GHANNAM; SHAW, 1980). O código desenvolvido neste trabalho foi acoplado aos módulos do código ONERA com o objetivo de simular as formas de gelo em aerofólios para diversas condições de escoamento do ar com conteúdo de água. As formas de gelo obtidas foram comparadas com dados experimentais de Shine Bond (1994) e com resultados de simulações dos códigos LEWICE, TRAJICE e ONERA (KIND, 2001). Os resultados das simulações do presente trabalho apresentaram boa semelhança com os resultados dos outros códigos. A simulação da previsão de formas de gelo do tipo Glaze, do presente trabalho e dos outros códigos, resultou em formas de gelo de espessura e volume menores que as formas experimentais. Foi verificado que uma previsão adequada do coeficiente de transferência de calor convectivo afeta a simulação das formas deste tipo de gelo. Um caso de Kind (2001) foi utilizado para avaliar os efeitos dos parâmetros da camada limite dinâmica e térmica na formação de gelo em aerofólios. Verificou-se que a posição do início da transição do regime laminar para o turbulento, o comprimento d a transição e o valor da rugosidade afetam a forma, a espessura e o volume do gelo, e que estes parâmetros podem ser utilizados para ajustes dos modelos de camada limite para melhores previsões de formas de gelo do tipo Glaze.The model to evaluate the momentum and thermal boundary layer was implemented, in the present work, in a numerical module to calculate the convective heat transfer coecient over aeronautical airfoils with ice accretion. It was considered, in the turbulent boundary layer model, the eects of the equivalent sand grain roughness ks , and the laminar to turbulent transition was evaluated with two models, the abrupt and the smooth one. The smooth transition model used an intermittency function proposed by (ABU-GHANNAM; SHAW, 1980). The module developed in this work was integrated with the modules of the code ONERA in order to simulate the airfoil icing shapes for several air stream with water droplets condition. The ice shapes obtained was compared with experimental data of Shin e Bond (1994) and with simulation results for the codes LEWICE, TRAJICE e ONERA (KIND, 2001). The results of the simulations for the present work showed a good similarity with the other codes results. The Glaze icing shapes simulation, in the present work and in the other codes, resulted in icing shapes with thickness and volumes lesser than the experimental shapes. It was noted that a reasonable prediction of the convective heat transfer coecient aects the simulation of this type of ice shape. One case of Kind (2001) was used to evaluate the eects of the momentum and thermal boundary layer for the icing accreations in the airfoil. It was noted the onset position, the lenght of the laminar-turbulent transition, and the sand grain roughness value aects the icing shape, thickness and volume and this parameters might be used to adjust the boundary layer models in order to get better predictions of Glaze icing shapes.
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Lambrinos, Grégoire. "Sublimation des milieux disperses congeles soumis a des temperatures negatives." Paris 6, 1988. http://www.theses.fr/1988PA066637.
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Thiagalingam, Ilango. "Modélisation des transferts thermiques convectifs en régime turbulent à l'interface milieu poreux / paroi dans les lits catalytiques." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066126/document.
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Le travail réalisé porte sur la modélisation à l'échelle macroscopique des transferts thermiques dans les lits catalytiques et au voisinage de la paroi. L'objectif principal de ce travail est de comprendre et de modéliser les mécanismes physiques responsables des transferts thermiques dans cette région. La physique proche paroi est capturée à l'échelle macroscopique de façon univoque à l'aide du concept de changement d'échelle et la notion de prise de moyenne volumique est étendue aux types de systèmes que nous considérons. Le coefficient de transfert à la paroi du modèle à deux coefficients λr - hw est premièrement décortiqué afin de mettre en lumière les mécanismes physiques contenus dans cette notion ainsi que le poids de leur contribution respective. Un modèle, basé sur la dynamique de l'écoulement et décrivant le transport de la chaleur dans la direction radiale, est ensuite dérivé à l'échelle macroscopique. Il met notamment en évidence une zone proche paroi particulière, dominée par l'effet de canalisation, qui amortit les transferts diffusifs dans la direction normale à la paroi. On montre ainsi que les transferts thermiques pilotés essentiellement par des mécanismes de dispersion mécanique sont limités dans cette région par des effets de résistance thermique de type convective. Finalement, une loi de paroi décrivant une couche limite perturbée par la matrice solide est utilisée pour faire le raccord à la paroi, ce qui a permis de prédire avec satisfaction la température à la paroiThis work deals with the modeling of near wall heat transfers in catalytic packed beds at the macroscopic scale. The main aims of the present work are the understanding and the modeling of physical mechanisms responsible for the heat transfers in the vicinity of the wall at the observation scale. Volume averaging concept is first extended to systems we consider. Thus, relevant physical mechanisms occurring in the near wall zone are unequivocally up-scaled from pore to bed scale. Then, the detailed analysis of the wall heat transfer coefficient, used in the popular two coefficient model λr - hw, brings to light each physical mechanism and its respective weighted contribution lumped in it. A model, based on the flow dynamic and describing the radial heat transfer, is finally derived at the reactor scale. It highlights that a channel effect occurs in the near wall zone, damping transfers by diffusion in the wall normal direction. It is hence showed that heat transfers mainly driven by mechanical dispersion are facing a convective thermal resistance near the wall. A wall law is also derived to model boundary layer/porous medium interactions, which ultimately connect the porous media model to the wall. Wall temperature is thus recovered with satisfaction
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Gadiraju, Siddhartha. "Study of Lean Blowout Limits and Effects of Near Blowout Oscillations on Flow Field and Heat Transfer on Gas Turbine Combustor." Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/82480.
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Modern gas turbine combustors implement lean premixed (LPM) combustion system to reduce the formation of NOx pollutants. LPM technology has advanced to have the ability to produce extremely low level of NOx emissions. The current focus of research on LPM is focused on reducing the NOx emission to much smaller scales, which is mandated because of the stricter regulations and environmental concerns. However, LPM combustors are susceptible to lean blowout (LBO), and other corresponding instabilities as the combustor is operated lean. Therefore, it is essential to understand the LBO limits and dynamics of flow in lean operating conditions. One of the other primary parameters for the improved combustion chamber designs is an accurate characterization of the heat loads on the liner walls in the wide range of operating conditions. Currently, there are very limited studies on the flame side heat transfer in reacting conditions. Current gas turbine combustion technology primarily focuses on burning natural gas as the gas fuel option for industrial systems. However, interest in utilizing additional options due to environmental regulations as well as concerns about energy security have motivated interest in using fuel gases that have blends of Methane, Propane, H2, CO, CO2, and N2. For example, fuel blends of 35%/60% to 55%/35% of CH4/CO2 are typically seen in Landfill gases. Syngas fuels are typically composed primarily of H2, CO, and N2. Gases from anaerobic digestion of sewage, used commonly in wastewater treatment plants, usually have 65–75% CH4 with the balance being N2.
The objective of this study is to understand the LBO limits and the effects of the instabilities that arise (called near blowout oscillations) as the combustor is operated lean. Near blowout oscillations arise as the equivalence ratio is reduced. These oscillations are characterized by continuous blowout and re-ignition events happening at low frequencies. The low-frequency oscillations have very high-pressure amplitude and can potentially damage the liner wall. The impact of the near blowout oscillations on the flow field and heat transfer on the liner walls are studied. To accomplish this, the experiments were conducted at Advanced Propulsion and Power laboratory located at Virginia Tech. A lean premixed, swirl stabilized fuel nozzle designed with central pilot hub was used for the study. Additionally, this work also studies the lean blowout limits with fuel blends of CH4-C3H8, CH4-CO2, and CH4-N2 and also their effect on the stability limits as the pilot fuel percentage was changed.
Flow field during near blowout oscillations was studied using planar particle image velocimetry (PIV) and flame shapes and locations during these oscillations was studied by using high-speed imaging of the flame. A statistical tool called proper orthogonal decomposition (POD) was utilized to post-process the PIV data and high-speed imaging data. Heat transfer on the liner walls was studied using a transient IR thermography methodology. The heat transfer on the liner wall during the near blowout instabilities was resolved. LBO limits and near blowout oscillations were characterized by studying the pressure measurements in the primary combustor region.
Fluctuating heat loads on the liner walls with the same frequency as that of near blowout instabilities was observed. The magnitude of fluctuation was found to be very high. Phase sorted POD reconstructed flame images demonstrated the location of the flame during near blowout oscillations. Thus, blowout and re-ignition events are resolved from the high-speed flame images. POD reconstructed flow field from the PIV data demonstrated the statistically significant flow structures during near blowout oscillations. A hypothesis for the mechanism of near blowout oscillations was explained based on the measurements and observations made.
Lean Blowout limits (LBO) changed when the percentage of pilot and air flow rates was changed. As the pilot percentage increased, LBO limits improved. Results on the study of fuel mixtures demonstrate that the addition of propane, nitrogen and carbon dioxide has minimal effect on when the flame becomes unstable in lean operating conditions. However, on the other hand, the addition of diluent gas showed a potential blowout at higher operating conditions. It was also observed that Wobbe index might not be a good representation for fuels to study the fuel interchangeability in lean operating conditions.Ph. D.
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Sharma, Sushank. "Transition laminaire turbulent dans les couches limites supersoniques : différents scénarios et contrôle possible Control of oblique-type breakdown in a supersonic boundary layer employing streaks Turbulent flow topology in supersonic boundary layer with wall heat transfer Laminar-to-turbulent transition in supersonic boundary layer : : Effects of initial perturbation and wall heat transfer Effect of thermo-mechanical non-equilibrium on the onset of transition in supersonic boundary layers." Thesis, Normandie, 2019. http://www.theses.fr/2019NORMIR16.
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Les simulations numériques directes (DNS) des couches limites supersoniques adiabatiques et isothermes (chauffées et refroidies) sont effectuées. Deux différents scénarios de transition, à savoir la décomposition de type oblique et la transition de type 'by-pass', sont présentés en détail. Pour le scénario de transition de type oblique, les résultats montrent que les modes contrôles avec un nombre d'onde quatre à cinq fois supérieur au nombre fondamental se révèlent être bénéfiques pour contrôler la transition. Dans la première région après le forçage du mode de contrôle, la distorsion de flux moyenne (MFD) bénéfique générée en induisant le mode de contrôle est uniquement responsable de l'entrave à la croissance du mode fondamental. Globalement, le MFD et la partie tridimensionnelle du contrôle contribuent également à contrôler la rupture oblique. Les effets de paramètres physiques tels que la température de paroi, l'intensité de la perturbation et le 'baseflow' sont étudiés pour la transition de 'By-pass'. Les résultats concernant le scénario de by-pass révèlent que l'augmentation de l'intensité de la perturbation déplace le début de la transition en amont et augmente également la longueur de la région de transition. De plus, en dessous de 1 % des niveaux de perturbation, le refroidissement de la paroi stabilise le flux, tandis que l'inverse se produit à des valeurs plus élevées. L'existence d'un non-équilibre thermomécanique avance le début de la transition pour les cas chauffés alors que la paroi refroidie se comporte dans le sens opposé. Les analyses de la couche limite turbulente montrent que les facteurs thermiques influencent la topologie et l'inclinaison des structures tourbillonnaires. De plus, en ce qui concerne le flux de chaleur, un processus de transfert différent est dominant dans la région proche paroi pour la paroi refroidieDirect numerical simulations (DNS) of both adiabatic and isothermal (heated and cooled) supersonic boundary layers are performed. Two different transition scenarios, namely the Oblique-type breakdown and the By-pass transition are presented in detail. For the oblique-type transition scenario, the results show that the control modes with four to five times the fundamental wavenumber are beneficial for controlling the transition. In the first region, after the control-mode forcing, the beneficial mean-flow distortion (MFD) generated by inducing the control mode is solely responsible for hampering the growth of the fundamental-mode. Globally, the MFD and the three-dimensional part of the control contribute equally towards controlling the oblique breakdown. Effects of physical parameters like wall-temperature, perturbation intensity and baseflow are investigated for the By-pass transition. The results regarding the by-pass scenario reveal that increasing the perturbation intensity moves the transition onset upstream and also increases the length of the transition region. Additionally, below 1% perturbation levels, wall-cooling stabilizes the flow while inverse happens at higher values. The existence of the thermo-mechanical non-equilibrium advances the onset of transition for the heated cases while the cooled wall behaves in the opposite sense. The analyses of the turbulent boundary layer show that the thermal factors influence the topology and inclination of the vortical structures. Moreover, regarding the heat flux, different transfer process is dominant in the near-wall region for the cooled wall
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Bayeux, Charlotte. "Méthode intégrale pour la couche limite tridimensionnelle - Applications au givrage." Thesis, Toulouse, ISAE, 2017. http://www.theses.fr/2017ESAE0047/document.
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Depuis de nombreuses années, le givrage a été identifié comme un danger dans le domaine de l’aéronautique.L’accrétion de givre se produit lorsque des gouttelettes d’eau surfondue se déposent sur une surface, enparticulier le bord d’attaque d’une aile ou la lèvre d’entrée d’air moteur, et gèlent après l’impact. Ceci peutensuite engendrer une dégradation des performances aérodynamiques, un dysfonctionnement des sondes ouencore un endommagement du moteur. C’est pourquoi cette problématique est étudiée avec attention. Lesessais en vol et en soufflerie étant longs et coûteux, la simulation numérique de l’accrétion de givre est devenueun outil nécessaire dans le processus de conception et de certification des avions. Cette thèse s’inscrit dans le contexte de la modélisation 3D de l’accrétion de givre, et plus particulièrement des couches limites dynamique et thermique qui se développent autour du corps givré. Les outils numériques devant être rapides et robustes, l’approche proposée dans cette thèse pour le calcul aérodynamique est une méthode couplée Euler/couche limite intégrale. Ainsi, un modèle intégral est développé pour représenterle développement de la couche limite dynamique. La partie thermique est modélisée soit par une méthodesimplifiée basée sur des approches algébriques, soit par une méthode intégrale. Cette modélisation des coucheslimites dynamique et thermique est valable sur paroi lisse ou rugueuse et permet de fournir notamment lecoefficient de frottement et le coefficient d’échange thermique qui sont nécessaires pour un calcul d’accrétion degivre. Les équations intégrales de couche limite, associées à leurs relations de fermeture, sont ensuite résoluespar une méthode Volumes-Finis sur maillage surfacique non structuré, qui est bien adaptée pour les géométriescomplexes. De plus, des traitements numériques spécifiques sont mis en œuvre pour améliorer la précision dela méthode au voisinage du point d’arrêt et pour rendre le code robuste au passage du décollement.Après la validation de la méthode de couche limite, le code est utilisé dans les chaînes de givrage 2D et 3Dde l’ONERA pour des applications d’accrétion de givre. Ceci permet de montrer l’intérêt de la méthode entermes de robustesse et de précision par rapport aux codes de couche limite habituellement utilisés dans lescodes de givrage actuelsIcing has since long been identified as a serious issue in the aeronautical world. Ice accretion occurs whensupercooled water droplets impinge on a surface, particularly the leading edge of a wing or an engine inlet, andfreeze after the impingement. This can lead to degradation of aerodynamic performances, sensor malfunctionor engine damage. This is why this issue is being carefully studied. The lengthy and costly flight and windtunnel tests have made numerical simulation of ice accretion a necessary tool in the aircraft design andcertification process. The present work deals with the 3D numerical modeling of ice accretion, and more particularly the modeling of the dynamic and thermal boundary layers that develop around an iced body. Since numerical tools must befast and robust, the approach proposed in this thesis for aerodynamic computation is a coupled Euler/integralboundary layer method. Thus, an integral model is developed to represent the development of the dynamicboundary layer. The thermal part is modeled either by a simplified method based on algebraic approaches,or by an integral method. This modeling of the dynamic and thermal boundary layers is valid on smoothor rough walls and provides the friction coefficient and heat exchange coefficient that are necessary for thecalculation of ice accretion. The integral boundary layer equations, associated with their closure relations,are then solved by a Finite-Volume method on unstructured surface mesh, that is well suited for complexgeometries. In addition, specific numerical treatments are implemented to improve the accuracy of the methodin the vicinity of the stagnation point and to make the code robust to separated boundary layers.After validation of the boundary layer method, the code is used in ONERA’s 2D and 3D icing tools foricing applications. This demonstrates the value of the method in terms of robustness and accuracy comparedto the boundary layer codes more commonly used in current icing tools
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Williamson, Alexander James. "Methods, rules and limits of successful self-assembly." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:9eb549f9-3372-4a38-9370-a9b0e58ca26b.
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The self-assembly of structured particles into monodisperse clusters is a challenge on the nano-, micro- and even macro-scale. While biological systems are able to self-assemble with comparative ease, many aspects of this self-assembly are not fully understood. In this thesis, we look at the strategies and rules that can be applied to encourage the formation of monodisperse clusters. Though much of the inspiration is biological in nature, the simulations use a simple minimal patchy particle model and are thus applicable to a wide range of systems. The topics that this thesis addresses include: Encapsulation: We show how clusters can be used to encapsulate objects and demonstrate that such `templates' can be used to control the assembly mechanisms and enhance the formation of more complex objects. Hierarchical self-assembly: We investigate the use of hierarchical mechanisms in enhancing the formation of clusters. We find that, while we are able to extend the ranges where we see successful assembly by using a hierarchical assembly pathway, it does not straightforwardly provide a route to enhance the complexity of structures that can be formed. Pore formation: We use our simple model to investigate a particular biological example, namely the self-assembly and formation of heptameric alpha-haemolysin pores, and show that pore insertion is key to rationalising experimental results on this system. Phase re-entrance: We look at the computation of equilibrium phase diagrams for self-assembling systems, particularly focusing on the possible presence of an unusual liquid-vapour phase re-entrance that has been suggested by dynamical simulations, using a variety of techniques.
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Santos, Thiago Augusto dos. "Desenvolvimento de um código mono canal para análise termo hidráulica de reatores PWR." reponame:Repositório Institucional da UFABC, 2016.
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Orientador: Prof. Dr. José Rubens MaiorinoDissertação (mestrado) - Universidade Federal do ABC. Programa de Pós-Graduação em Energia, 2016.
O presente trabalho desenvolveu um código, intitulado STH-MOX-Th (Simplified Thermal- Hydraulics code-Mixed Oxide Thorium), com o objetivo de calcular os limites térmicos (temperaturas limite do combustível e do revestimento, além do DNBR-"Departure of Nucleate Boiling Ratio"- mínimo) de um reator PWR do tipo vareta para combustíveis de UO2 e óxidos mistos de Urânio-Tório. ((U,Th)O2) utilizando correlações específicas para cada combustível cujo coeficiente de condutividade térmica é uma função dependente da temperatura. Para tal resolução, foi utilizado o método de Runge-kutta de 4ª ordem. O código analisa apenas o canal mais quente do núcleo do reator e, por conta dessa simplificação, possui uma parte hidráulica simples. Além da parte hidráulica, o programa calcula a distribuição axial e radial das temperaturas do refrigerante e vareta, bem como distribuições de entalpia e pressão. Todos esses cálculos foram realizados no início do ciclo do combustível no caso do (U, Th)O2 e para o UO2 e, além disso, o código calcula casos considerando a queima do combustível (meio e final de ciclo) somente para o UO2, uma vez que não foi encontrada nenhuma correlação para o coeficiente de condutividade térmica para o (U,Th)O2 em função da queima. Para validar o programa foram utilizados dados referentes a usina de Angra 2 para a entrada do programa e os resultados comparados com os reportados pelo Relatório Final de Análise de Segurança da Eletronuclear e do reator AP-1000, desenvolvido pela Westinghouse. A grande contribuição do trabalho, é o cálculo dos limites térmicos de um reator utilizando óxidos mistos de urânio e tório no núcleo do reator AP-1000, que é objeto das pesquisas na UFABC. Apesar de não ser original, o trabalho possuí fins didáticos e será extremamente útil no que diz respeito a uma primeira análise dos limites térmicos de um reator nuclear.
The present study developed a code, named STH-MOX-Th (Simplified Thermal-Hydraulics code-Mixed Oxide Thorium), created in order to calculate the thermal limits (limit temperature of the fuel and of the coating, besides the DNBR -"Departure of Nucleate Boiling Ratio"- minimum) of a PWR rod type reactor to UO2 fuel and mixed oxides of Uranium- Thorium. ((U,Th)O2) using specific correlations to each fuel which coefficient of thermal conductivity is a function dependent on temperature. For such a resolution, the method Runge-kutta of 4th order was employed. The code analyses only the hottest channel of the reactor core and, because of this simplification, it has one simple hydraulic part. In addition to the hydraulic part, the program calculates the axial and radial distribution of refrigerant and rod temperatures, as well as the distributions of enthalpy and pressure. All these calculations were done in the beginning of the fuel cycle in the case of (U,Th)O2and, for UO2, the code also calculates cases that consider the fuel burning (beginning, middle and end of the fuel cycle) only for UO2, once it was not found any correlation to the coefficient of thermal conductivity to (U,Th)O2 being dependent on fuel burning.In order to validate the program, data from Angra 2 plant were used to the program input and the results were compared with the ones reported by the Final Report on Security Analysis of Eletronuclear and with the ones of AP-1000 reactor, developed by Westinghouse. As the main contribution, the program made such calculations to the project of the fuel reactor of (U-Th) O2, APTh-1000. Although this study is not original, it has learning purposes and will be extremely useful concerning a very first analysis of the thermal limits of a nuclear reactor.
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Ferragh, Omar. "Etude du transfert de chaleur et de masse dans un écoulement d'air entre deux plaques parallèles en présence d'un ruissellement d'eau : Application aux réfrigérants industriels." Valenciennes, 1995. https://ged.uphf.fr/nuxeo/site/esupversions/4aad8950-0f32-46d7-9276-1f08fd498651.
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L'étude consiste a analyser les échanges thermiques et massiques découlant d'une évaporation par convection forcée, entre deux plaques parallèles en présence d'un ruissellement d'eau. L'étude est entreprise sous ses deux aspects: théorique et expérimental. La modélisation est basée sur les théories des couches limites dynamique et thermique couplées avec les concepts de transport de masse, au sein du fluide en écoulement, pour un régime de couches limites laminaires. Le couplage des deux problèmes thermique et massique est réalisé par l'intermédiaire des conditions à l'interface eau-air. Suite à ce modèle théorique, un programme de calcul et de simulation a été développé. Pour une géométrie de dispositif et une puissance de chauffe donnée, et pour des caractéristiques d'entrée données, le programme de simulation détermine toutes les performances dynamiques et thermiques. Les résultats issus de celui-ci ont été comparés aux mesures expérimentales. Enfin, une étude expérimentale menée sur les réfrigérants industriels, en fonctionnement humide, a permis de montrer une certaine analogie entre les phénomènes mis en évidence par ces essais et par le modèle théorique, qui a été développé, pour le cas du transfert de chaleur et de masse entre deux plaques parallèles. Cette approche a montrée l'importance des phénomènes d'évaporation en convection forcée dans l'industrie.
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Boillot, Benjamin. "Contribution à l'étude des écoulements turbulents en convection mixte." Université Joseph Fourier (Grenoble), 1996. http://www.theses.fr/1996GRE10062.
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Ce travail porte sur l'etude des ecoulements turbulents en convection mixte. La premiere partie de ce travail fut consacree a la comparaison des couches limites de convection forcee et de convection naturelle. Nous avons pu montrer que ces deux ecoulements etaient fort differents, meme en proximite de paroi, tant sur les profils de grandeurs moyennes et les grandeurs fluctuantes que sur les transferts energetiques. Dans un deuxieme temps, nous avons calcule un ecoulement de convection mixte dans un canal vertical avec une paroi chaude et une froide. Pour cela, nous avons developpe un code unidimensionnel qui permet de calculer les profils etabli de cet ecoulement. Pour modeliser la turbulence, nous avons utilise un modele k- bas reynolds developpe par nagano et al. (celui-ci ayant donne les meilleurs resultats en convection forcee). Les resultats obtenus confirment ceux experimentaux de nakajima et al. . On observe une augmentation de l'intensite de la turbulence du cote de la paroi froide et inversement du cote de la paroi chaude. La principale conclusion porte sur les lois de paroi generalement utilisee en ecoulements turbulents. Ces lois de paroi de convection forcee paraissent inadequates pour resoudre des ecoulements avec forces de volume. En consequence, une etude experimentale sur l'etude de la turbulence en convection mixte semble necessaire afin d'obtenir une base de donnees detaillee pour developper des nouveaux modeles
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Ben, Nasr Ouissem. "Numerical simulations of supersonic turbulent wall-bounded flows." Phd thesis, INSA de Rouen, 2012. http://tel.archives-ouvertes.fr/tel-01059805.
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This work deals with spatially-evolving supersonic turbulent boundary layers over adiabatic and cold walls at M∞ = 2 and up to Re0 ≈ 2600 using 3 different SGS models. The numerical methodology is based on high-order split-centered scheme to discretize the convective fluxes of the Navier-Stokes equations . For the adiabatic case, it is demonstrated that all SGS models require a comparable minimum grid-refinement in order to capture accurately the near-wall-turbulence. Overall, the models exhibit correct behavior when predictiong the dynamic properties, but show different performances for the temperature distribution in the near-wall region. For the isothermal case, it is found that the compressibility effects are not enhanced due to the wall cooling. As expected, the total temperature fluctuations are not negligible in the near-wall region. The study shows that the anti-correlation linking both velocity and temperature fields, derived from the Morkovin's hypothesis, is not satisfied.
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Leduc, Christian. "Modélisation de la condensation en film sur les parois d'une enceinte de réacteurs." Université Joseph Fourier (Grenoble ; 1971-2015), 1995. http://www.theses.fr/1995GRE10157.
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Un code enceinte, utilise dans les analyses de surete des centrales nucleaires, doit pouvoir predire les evolutions de la pression et des concentrations en vapeur, air et hydrogene dans l'enceinte de confinement d'un reacteur a eau pressurisee en situation accidentelle. La condensation de la vapeur sur les parois froides est un facteur essentiel de ces evolutions. Nous proposons un modele de condensation en film en presence de gaz incondensables. L'ecoulement du film est considere laminaire. Trois approches differentes sont abordees pour modeliser les transferts dans les couches limites: utilisation de correlations globales dans lesquelles nous avons employe un nombre de grashof hybride exprimant que la convection est a la fois de nature thermique et massique. Calcul de la couche limite avec utilisation de lois de paroi pour un regime de convection forcee. Nous proposons des lois prenant en compte la vitesse d'aspiration de la couche limite due a la condensation, et l'influence de l'etat de surface du film (lisse ou ridee). Calcul de la couche limite avec un modele k-epsilon a bas nombre de reynolds pour un regime de convection naturelle. Ces modeles ont ete implantes dans le code de thermohydraulique 3d-trio-vf. Les coefficients de transfert de chaleur theoriques obtenus sont compares a ceux des resultats experimentaux
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Mahfouf, Jean-François. "Contribution a la definition d'une parametrisation des transferts entre le sol, la vegetation et l'atmosphere : analyse de sensibilite et insertion dans un modele mesoechelle." Clermont-Ferrand 2, 1986. http://www.theses.fr/1986CLF21010.
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Un modele numerique a mesoechelle (nickerson et al, 1986) comportant un ensemble detaille de parametrisations pour la couche limite planetaire (therry et lacarrere, 1983), la vegetation (deardorff, 1978) et les transferts thermo-hydriques dans le sol (mclumber et pielke, 1981) a ete developpe. Tout d'abord, une version unidimensionnelle nous a permis de realiser un ensemble complet de tests de sensibilite sur l'influence de l'evolution diurne de la basse atmosphere vis a vis de l'etat hydrique du sol, de l'albedo de surface et du type de couvert vegetal notamment. Une comparaison a ete effectuee avec les donnees de l'experience de couche limite "wangara", indiquant un bon accord entre les resultats du modele et l'observation
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Silva, Guilherme Araújo Lima da. "Modelagem e simulação da operação de sistema antigelo eletrotérmico de um aerofólio." Universidade de São Paulo, 2002. http://www.teses.usp.br/teses/disponiveis/3/3132/tde-19092007-000212/.
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No presente trabalho foi implementado um modelo matemático para simular o sistema antigelo eletrotérmico de um aerofólio. Por meio do programa ONERA2D simulou-se o escoamento potencial completo com velocidade 44,7 m/s (100 mph) e 89,4 m/s (200 mph) em torno de um aerofólio perfil NACA0012 de corda 0,914 m (3 pés) com ângulo de ataque de 0°, e calculou-se a eficiência de coleta local de gotículas de água com diâmetro mediano volumétrico de 20 μm. Foram simuladas quatro condições de teste com diferentes distribuições de fluxo de calor nos aquecedores elétricos do sistema antigelo. O modelo previu a distribuição de temperaturas na superfície sólida do aerofólio e no filme de água líquida, e as distribuições de fluxo de água líquida sobre a superfície do aerofólio (\"runback water\") e de coeficiente de transferência de calor por convecção de calor entre a superfície do aerofólio e o escoamento gasoso. Os resultados da simulação obtidos com o modelo foram comparados com resultados experimentais da NASA e os resultados numéricos dos programas LEWICE/ANTICE (EUA) e CANICE (Canada). Para as regiões molhadas pelo filme de água líquida, obteve-se um desvio máximo de temperatura de 2,6°C entre os resultados do presente modelo e o resultados experimentais. Para as regiões secas, onde não existe o filme de água líquida sobre a superfície do aerofólio, obteve-se um desvio de máximo de temperatura de 8°C. As previsões para distribuição de vazão de \"runback\", posição do término do filme de água líquida foram comparadas com os resultados do programa LEWICE/ANTICE. O modelo desenvolvido simula com adequada aproximação os efeitos da transferência de calor e de massa por convecção entre a superfície não-isotérmica do aerofólio ou do filme de água líquida e o escoamento gasoso, bem como os efeitos da transição entre o escoamento laminar e o turbulento na camada limite dinâmica e térmica e ainda a influência do escoamento do filme de água líquida sobre o desempenho do sistema de antigelo do aerofólio.An electro-thermal anti-ice system was simulated with a mathematical model developed in the present work. A 44.7 m/s (100 mph) and 89.4 m/s (200 mph) full potential flow around a 0.914 m (3 ft) chord NACA0012 airfoil with 0° angle of attack and the local water catch efficiency of 20 μm median volumetric diameter droplets impingement were calculated by the numerical code ONERA2D. Four test conditions were simulated with four different heat flux distributions of the anti-ice system according to the experimental work developed at NASA. The model predicted distributions of solid surface and liquid water film temperatures, runback water flow and convection heat transfer coefficient between airfoil or water surface and gaseous flow. The simulated results obtained by the mathematical model developed were compared to NASA experimental results and the ones predicted by the numerical codes LEWICE/ANTICE (US) and CANICE (Canada). For the regions wetted by the water film, the present model provided 2.6°C maximum temperature deviations between the predicted results and experimental data. For the dry regions, where there is no liquid water on the airfoil surface, an 8°C maximum temperature deviation was obtained. The runback flow and water film ending point position were compared to LEWICE/ANTICE numerical results. The developed model predicts adequately the convection heat and mass transfer effects between the non-isothermal airfoil or liquid water film surface and the gaseous flow, as well the effects of laminar to turbulent flow transition within dynamic and thermal boundary layer and the influence of the liquid water film flow on the anti-ice system performance.
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El, Kabiri Mohamed. "Transport et diffusion turbulente de la chaleur en aval d'une source linéaire placée au-dessus d'une paroi adiabatique." Rouen, 1996. http://www.theses.fr/1996ROUES040.
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L'étude expérimentale du transfert de chaleur en aval d'une source linéaire placée successivement à différentes hauteurs dans une couche limite turbulente a été réalisée. L'ensemble des moments des champs de vitesse et de température jusqu'à l'ordre 3 sont présentés et analysés à partir des modélisations usuelles. Les équations de bilan de l'enthalpie, de la variance des fluctuations de température, des flux de chaleur turbulents verticaux et horizontaux ont été évaluées. Un schéma de normation basé sur l'évolution géométrique du champ de température moyenne a permis de rassembler l'ensemble des résultats
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Méndez, Margio González. "Simulations numériques de la transition de la couche limite sur une surface concave : application à la conception des éoliennes à axe vertical de type Savonius Heat-transfer analysis of a transitional boundary layer over a concave surface with Görtler vortices by means of direct numerical simulations Boundary layer transition over a concave surface caused by centrifugal instabilities." Thesis, Normandie, 2020. http://www.theses.fr/2020NORMIR05.
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Des simulations numériques directes (DNS) sont calculées afin d’étudier le processus complet de transition laminaire-turbulent d’une couche limite qui se développe sur une surface concave. On constate que l’écoulement traversant une telle géométrie est susceptible de développer des instabilités centrifuges sous forme de tourbillons de Görtler. La transition est déclenchée au moyen d’éléments de rugosité de paroi qui sont également utilisés pour prédéfinir la longueur d’onde transversale des tourbillons de Görtler. Les différentes régions rencontrées dans le processus de transition, c’est-à-dire linéaire, non-linéaire, transition et complètement turbulente, sont identifiées et caractérisées. Les instabilités primaires et secondaires (sinueux et variqueux) sont également identifiées et analysées. Des études paramétriques montrant l’effet de plusieurs paramètres physiques (le rayon de courbure, la longueur d’onde des tourbillons, l’amplitude et la localisation de la perturbation, et la géométrie des éléments de rugosité de paroi) sur le point de départ de la transition sont présentées. De plus, des analyses thermiques sont menées afin d’étudier la modification de la couche limite thermique produite par le mouvement rotatif des tourbillons de Görtler. L’évolution du transfert thermique de la surface est étudiée et on constate qu’il est considérablement augmenté dans la région non-linéaire dépassant les valeurs de la région turbulente. On constate également que l’analogie de Reynolds entre la quantité de mouvement dans le sens de l’écoulement et le transfert de chaleur est suivie tout au long du processus de transitionDirect numerical simulations (DNS) are computed in order to study the complete laminar-to-turbulent transition process of a boundary layer developing over a concave surface. It is found that the flow passing through such geometry is prone to develop centrifugal instabilities in the form of Görtler vortices. Transition is triggered by means of wall-roughness elements that are also utilized to preset the spanwise wavelength of the Görtler vortices. The different regions encountered in the transition process, i.e. linear, nonlinear, transition, and fully turbulent, are identified and characterized. Primary and secondary (varicose and sinuous) instabilities are identified and analyzed as well. Parametric studies showing the effect of several physical parameters (radius of curvature, the vortices wave-length, the perturbation amplitude and streamwise location, and the wall-roughness perturbation geometry) on the transition starting point are presented. Furthermore, thermal analyses are conducted in order to study the modification of the thermal boundary layer due to the Görtler vortices swirl motion. The streamwise evolution of the surface heat transfer is investigated finding that it is considerably enhanced in the non-linear region surpassing the turbulence-region values. It is also found that the Reynolds analogy between streamwise-momentum and heat transfer is followed throughout the whole transition process
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Brejaud, Pascal. "Etude théorique et expérimentale d'un nouveau concept de moteur hybride thermique-pneumatique." Phd thesis, Université d'Orléans, 2011. http://tel.archives-ouvertes.fr/tel-00831692.
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Ce travail présente une étude théorique et expérimentale portant sur le concept de Moteur Hybride Pneumatique ( MHP). En première approche, un modèle 0D d'un MHP monocylindre, incluant un sous-modèle cinématique original pour l'actuateur entièrement variable muant la soupape de charge, est présenté puis exploité. La modélisation 1D de la dynamique des gaz dans chaque tubulure est traitée, incluant différents modèles de Condition Limite de Soupape (CLS), basées sur la méthode des caractéristiques et issues de la littérature. Il est montré que ces CLS ne sont pas adaptées à la modélisation d'un MHP : existence de chocs numériques, problème de non-convergence et mise en défaut face à des relevés expérimentaux. Un modèle original de CLS, évitant ces problèmes et demeurant basé sur la méthode des caractéristiques, est alors développé puis validé expérimentalement à la foi sur bancs d'essais moteurs et de dynamique des gaz à la soupape. Une étude expérimentale des échanges de chaleur convectifs, en mode pneumatique et sans combustion, est conduite et débouche alors sur une modification nécessaire de la corrélation standard de Woschni, afin de correctement décrire l'extinction du mouvement de tumble en fin de course de compression. Une exploitation de la plate-forme de simulation 1D de MHP monocylindre, incluant l'ensemble des éléments développés, est finalement conduite afin de déterminer les phasages optimums d'ouverture et de fermeture de la soupape de charge, pour différents mode et conditions opératoires. Cette étude, nécessaire à de futures simulations de cycles routier, confirme d'une part, la viabilité du concept et d'autre part, montre l'importance que revêt la prise en compte de la cinématique de l'actuateur soupape et de la dynamique des gaz dans la tubulure de charge.
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"AFM Bi-material Cantilever Based Near-field Radiation Heat Transfer Measurement." Master's thesis, 2019. http://hdl.handle.net/2286/R.I.54941.
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abstract: Near-field thermal radiation occurs when the distance between two surfaces at different temperatures is less than the characteristic wavelength of thermal radiation. While theoretical studies predict that the near-field radiative heat transfer could exceed Planck’s blackbody limit in the far-field by orders of magnitudes depending on the materials and gap distance, experimental measurement of super-Planckian near-field radiative heat flux is extremely challenging in particular at sub-100-nm vacuum gaps and few has been demonstrated. The objective of this thesis is to develop a novel thermal metrology based on AFM bi-material cantilever and experimentally measure near-field thermal radiation.
The experiment setup is completed and validated by measuring the near-field radiative heat transfer between a silica microsphere and a silica substrate and comparing with theoretical calculations. The bi-material AFM cantilever made of SiNi and Au bends with temperature changes, whose deflection is monitored by the position-sensitive diode. After careful calibration, the bi-material cantilever works as a thermal sensor, from which the near-field radiative conductance and tip temperature can be deduced when the silica substrate approaches the silica sphere attached to the cantilever by a piezo stage with a resolution of 1 nm from a few micrometers away till physical contact. The developed novel near-field thermal metrology will be used to measure the near-field radiative heat transfer between the silica microsphere and planar SiC surface as well as nanostructured SiC metasurface. This research aims to enhance the fundamental understandings of radiative heat transfer in the near-field which could lead to advances in microelectronics, optical data storage and thermal systems for energy conversion and thermal management.Dissertation/Thesis
Masters Thesis Mechanical Engineering 2019
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Gdhaidh, Farouq A. S., Khalid Hussain, and Hong Sheng Qi. "Enhancement of Natural Convection Heat Transfer within Closed Enclosure Using Parallel Fins." 2015. http://hdl.handle.net/10454/7920.
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yesA numerical study of natural convection heat transfer in water filled cavity has been examined in 3-D for single phase liquid cooling system by using an array of parallel plate fins mounted to one wall of a cavity. The heat generated by a heat source represents a computer CPU with dimensions of 37.5∗37.5mm mounted on substrate. A cold plate is used as a heat sink installed on the opposite vertical end of the enclosure. The air flow inside the computer case is created by an exhaust fan. A turbulent air flow is assumed and k-ε model is applied. The fins are installed on the substrate to enhance the heat transfer. The applied power energy range used is between 15 - 40W. In order to determine the thermal behaviour of the cooling system, the effect of the heat input and the number of the parallel plate fins are investigated. The results illustrate that as the fin number increases the maximum heat source temperature decreases. However, when the fin number increases to critical value the temperature start to increase due to the fins are too closely spaced and that cause the obstruction of water flow. The introduction of parallel plate fins reduces the maximum heat source temperature by 10% compared to the case without fins. The cooling system maintains the maximum chip temperature at 64.68°C when the heat input was at 40W that is much lower than the recommended computer chips limit temperature of no more than 85°C and hence the performance of the CPU is enhanced.
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Lee, Victor, and 李宣衡. "Probing the Limits of One-Dimensional Heat Transfer Phenomena." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/22650191438567386179.
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碩士國立臺灣大學
物理研究所
100
Experimental investigations of thermal conductivities of individual nanotube are challenging. In the introductory part of my thesis, I describe several attempts and methods to overcome the difficulties in thermodevice fabrications, sample preparations, and manipulations. Overcoming these challenges thus allows me to experimentally investigate the limits of heat transport in one-dimensional (1D) systems in three different aspects. (1) The limit of 1D heat transfer under extreme bending strain. (2) The lowest limit of thermal conductivity. (3) The highest limit of thermal conductivity. Single-wall carbon nanotubes (SWCNTs) as typical 1D materials have been shown to exhibit excellent mechanical properties and very long phonon mean free paths. In the second part of my thesis, I report in situ measurements of individual SWCNTs under cyclic mechanical bending. Surprisingly, we find that the thermal conductivity of the SWCNT remains intact even the characteristic phonon mean free path beyond the theoretical limit set by the radius of curvature. Our results strongly challenge the traditional theory of heat transfer. In the third part of the thesis, we demonstrate the lowest thermal conductivity of matters can be obtained in the weakest chemical bond of nature, in which the heat conduction displays unusual phonon tunneling behavior unfound before. Giant stepwise reductions of electrical/thermal conductivity are observed when the layers of high quality multiwall carbon nanotubes are removed one by one. We find that electrical and thermal anisotropy is more than 106. Correspondingly, the interlayer thermal conductivity of a nanotube is less than 2×10-3 W/m-K at room temperature, which is at least 25 times lower than that of the best thermal insulator known so far. In the last part of the thesis, we investigate the highest limit of thermal conductivity. The non-Fourier, divergent thermal conductivity is found in ultralong SWCNTs, leading to thermal conductivities as high as 8396 W/m-K in a 1.039 mm long SWCNT. The thermal conductivity is found to diverge with lengths to the power of 0.25 for SWCNTs. Moreover, the thermal conductivity shows no sign of saturation for sample lengths up to 1.039 mm. On the other hand, asymmetric thermal conductance is also observed in some of the SWCNT samples.