Dissertations / Theses on the topic 'Simulations thermiques dynamiques'
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Gribaa, Karim. "Simulation des effets thermiques et dynamiques dans le caoutchouc." Paris 6, 1993. http://www.theses.fr/1993PA066109.
Akkouche, Nour El Houda Rabab. "Approche comportementale pour le pilotage des consommations énergétiques dans le bâtiment." Electronic Thesis or Diss., Université Paris sciences et lettres, 2023. http://www.theses.fr/2023UPSLM081.
In the current context, efforts to reduce energy consumption in buildings must take into consideration a wide range of parameters, the building, its environment, its equipment and, above all, the behavior of its users. Nudges, which emerged from behavioral economics and find applications in various fields (finance, food, health, etc.), have been explored in the environmental context in general, and specifically in that of energy consumption in buildings.The aim of our work is to implement energy-saving behaviors through nudges in a building and to measure their impact using smart meters. Our approach involves dynamic thermal simulations, the use of connected sensors, and the creation of occupant profiles through questionnaires. These elements are typically addressed individually and isolated in the literature.We start with a theoretical assessment of the energy-saving actions that have the most significant impact in reducing energy consumption in a public tertiary building located in France. We create a framework based on psychological theories and previous works to define concepts that we use to define different energy consumers profiles. We conduct an experimentation using smart meters to measure the impact of nudges on behavioral change among occupants of an office building. To do this, we implement a platform for delivering various types of nudges to different profiles that we have established from a classification based on behavioral theories. In this way, we have combined the technological and behavioral aspects, which are often dealt with separately, and for which research often requires a multidisciplinary approach.Simulating different types of energy use scenarios in the same building is also interesting for studying the impact of occupants' behavior on energy consumption, and how the use of tailored incentives to raise awareness and encourage the larger adoption of energy savings measures can lead to a significant reduction in energy consumption in the building.The results obtained are positive in terms of energy savings, provided that prior knowledge of occupants is established
Lemay, Patrick. "Simulation dynamique des échanges thermiques à l'intérieur d'une serre." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1996. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/mq21791.pdf.
Fan, Yilin. "Distribution des fluides et intensification des transferts thermiques dans un échangeur thermique par l'intégration des distributeurs constructals." Chambéry, 2008. http://www.theses.fr/2008CHAMS040.
This thesis contributes to the advances in the conception, fabrication, modeling, experiment, and optimization of multi-scale fluid distributors. The function of such fluid distributors is to deliver a controlled amount or rate of fluid to an array of distributing ports, in order for example to feed uniformly the channels of a multi-channel heat exchanger and consequently intensify the heat transfer with the least increase of pressure drop. Their multi-scale internal channel structures are optimized by minimizing the viscous dissipation and the residence time simultaneously according to the "constructal theory". Polymer and metallic prototypes of the constructal components were fabricated using Stereolithography. Constructal distributor prototypes were assembled with a mini crossflow heat- exchanger to evaluate the effects of flow distribution on its thermal and hydraulic performances by experiments and by Computational Fluid Dynamics (CFD) simulations. The enhancement of heat transfer realized by flow uniform distribution and the thermal- hydraulic balance are discussed. The results indicate that the integration of one constructal collector at the outlet of the heat exchanger can approach the uniform flow distribution and consequently better intensify the heat transfer. It is also the most advantageous configuration based on a balanced consideration of heat transfer intensification and pump power consumption under the investigation conditions. The results may provide some original information and thoughts to the design and optimization of heat exchangers and flow distribution/collection systems
Moujalled, Bassam. "Modélisation dynamique du confort thermique dans les bâtiments naturellement ventilés." Lyon, INSA, 2007. http://theses.insa-lyon.fr/publication/2007ISAL0005/these.pdf.
N this work we focus on the adaptive approach of thermal comfort by combining features of both the static and adaptive theories. In the first step we have conducted a bibliographical study on the existing theories and approaches and which has led us to carry a field study on thermal comfort in eight office buildings. Afterwards we have adopted the systemic approach to develop a dynamic model on thermal comfort by integrating the dynamic mechanisms identified in the bibliography and the field study. This model, named AdOCC, determines the dynamic thermal state of the occupant from which the model can determine the adaptive behaviour of the occupant. AdOCC has been integrated in the dynamic simulation tool ‘TRNSYS’ and has been evaluated by comparing the results of the simulations with measurements. By applying this model to the case of a naturally ventilated office building we have found the conditions where thermal comfort can be achieved with limited energy consumptions
Moujalled, Bassam Guarracino Gérard Cantin Richard. "Modélisation dynamique du confort thermique dans les bâtiments naturellement ventilés." Villeurbanne : Doc'INSA, 2007. http://docinsa.insa-lyon.fr/these/pont.php?id=moujalled.
Zaoui, Hayat. "Conduction thermique à la nanoéchelle dans le silicium : simulations par dynamique moléculaire d’approche à l’équilibre." Thesis, Lille 1, 2017. http://www.theses.fr/2017LIL10081/document.
The thermal conductivity of nanostructures varies on a large scale compared to bulk materials. Sometimes the thermal transfer is worse due to the reduction of thermal conductivity, at the origin of self-heating in electronic devices, but valuable for thermoelectric devices. In other cases, the thermal conductivity reaches impressive levels compared to bulk materials. The origin of these behaviors is at the atomic level, and the in the propagation of the heat carriers, the phonons. In this thesis, we study heat transport in silicon nanostructures by atomic scale simulations. Molecular dynamics is used here in the framework of a methodology we recently developed, the approach-to-equilibrium molecular dynamics (AEMD). This methodology relies on the creation and exploitation of temperature transients. First we present the principles of AEMD in the case of bulk silicon. Then we determine the thermal conductivity of smooth nanowires versus diameter and length. We show that the temperature profiles do comply with the heat equation, and that the thermal conductivity saturates at long length. Afterwards we study nanostructuring effects by hollowing, and nanowires with rough surfaces. In this last case, we compare our results with an alternative simulation approach and investigate the relative importance of intrinsic and surface phonon scattering. Finally, we calculate the thermal conductivity of nanopatterned silicon membranes for thermoelectric devices. We show that to further decrease the thermal conductivity, it will be necessary to introduce other sources reduction than cylidrincal hole etching, and AEMD will be the appropriate tool for an optimisation
Vatteville, Judith. "Dynamique des panaches thermiques laminaires : application aux panaches mantelliques." Paris, Institut de physique du globe, 2009. http://www.theses.fr/2009GLOB0006.
In Earth Sciences, hot upwelling plumes are thought to develop from the base of the 2900 kmthick solid mantle of our planet and to generate hotspots, i. E. Intraplate volcanic islands such as Hawaii and La Reunion. Although generated through chaotic Rayleigh-B´enard instabilities at a Prandtl number (Pr) around 1023, they can be modelled with the simpler case of starting plumes out of a finite-size heater, either numerically for infinite Prandtl number, or in the laboratory with fluids with Pr ~ 103 - 106. Hence, the question is to find simple scaling laws for isolated rising plumes and apply them to the Earth’s mantle case. In this thesis we study the characteristics of an isolated plume growing in a viscous fluid with constant viscosity. We use both laboratory experiments and numerical models : the visualization techniques give us access to the growing plume temperature and velocity fields, on a 2-D section of the tank, whereas the numerical simulations are axisymmetric finite element simulations that attempt to reproduce the laboratory conditions as closely as possible. We find excellent quantitative agreement between the two fully independent approaches. This is used to derive scaling laws for the dynamics of the plume head and stem, and apply them to the Earth’s case. We further show that for Pr larger than 1000, confinement effects are more important than inertial effects and that plumes dynamics are well described by the approximation if infinite Prandlt number. This is especially true for planetary mantles
Fèvre, Mathieu. "Etudes microstructurales d'oxydes désordonnés et modélisation de leurs propriétés thermiques." Paris 11, 2003. http://www.theses.fr/2003PA112252.
This thesis is devoted to the modelling of disordered oxides by Monte Carlo and Molecular Dynamics simulations, in relation with short-range order investigations by neutrons and X-rays diffuse scattering measurements. In zirconia based oxides the kinetics of cations is very slow, whereas it is very fast for anions. These materials are ionic systems. Thus, the largest contribution to the energy of the system is given by long-range electrostatic interactions (1/r). Local order measurements have shown that chemical species are not randomly placed in the crystal structure. Due to the presence of structural vacancies, created by a charge compensation mechanism, lattice distortions are also important. Thus, the chemical ordering is strongly correlated to the atomic displacements. The Non Equilibrium Molecular Dynamics technique has been used to compute the thermal conductivity from atomic configurations. However, this method can only reproduce the movement of particles during several nanoseconds. Therefore, in order to ameliorate the description of micro structural properties and to analyze the influence on the conductivity of the local order, we developed a code based on a Monte Carlo approach, which is adapted to ionic systems and which can describe the strong elastic effects as well as the chemical effects. The short-range order reproduced in the Monte Carlo simulations is very closed to the one measured. We also show that Molecular Dynamics simulations cannot reproduce the correct local order between defects, observed at high doping concentrations. Moreover, the thermal conductivity computations have shown a good agreement with the experimental data. Indeed, the error between simulations and measurements are below 20%. Finally, this study also discusses the influence of the short-range order on the conductivity behaviour using numerical results, diffuse scattering investigations and thermal conductivity measurements
Dallaire, Jonathan. "Thermal conductivity of carbon nanotubes from equilibrium molecular dynamics simulations : sensitivity to modeling and simulation parameters." Thesis, Université Laval, 2012. http://www.theses.ulaval.ca/2012/29017/29017.pdf.
Scolan, Simon. "Développement d'un outil de simulation et d'optimisation dynamique d'une centrale solaire thermique." Thesis, Pau, 2020. http://www.theses.fr/2020PAUU3007.
In the current climate and energy context, solutions must be found to gradually replace the use of fossil fuels. Solar thermal energy is a resource with great potential that is still insufficiently exploited in France on an industrial scale. In this context, large solar thermal installations are increasingly studied. Currently, a majority of studies focus on optimizing the sizing of the plants based on standard operating strategies. This manuscript offers a mathematical resolution methodology for the simulation and dynamic optimization of a solar thermal plant. This type of optimization makes it possible to take into account the dynamics of this system and in particular the slow dynamics of a thermal energy storage. It is carried out by exploiting the degrees of freedom of the problem. By leaving certain design parameters free, dynamic optimization makes it possible to optimize the operation and sizing of the plant simultaneously.The different elements of a solar thermal plant (solar field, heat exchanger, thermal energy storage, pumps, pipes) are modeled and form a Differential Algebraic Equation system. We have described the orthogonal collocation method which allows to discretize these equations and thus, to obtain a system comprising only algebraic equations. Different models are confronted with experimental data from a plant located in Condat-sur-Vézère (France). Their precision is quantified. The development of a method by successive simulations and initializations allowed us to carry out the dynamic simulation of a solar thermal plant. However, certain operating constraints (control rules necessary to saturate the degrees of freedom) are difficult to formulate in a coherent and implementable way in the GAMS software used in this work. The interest of using dynamic optimization is to take advantage of the degrees of freedom of the problem in order to minimize / maximize an objective function (while respecting the constraints of the problem) without having to formulate constraints to saturate them.A first dynamic optimization problem was formulated and then solved, using an equation-oriented strategy. Over a five-day time horizon and with a fixed plant sizing, we have maximized the benefits from the sale of solar heat to a consumer by optimizing the operation of the plant. This notably brought to light counter-intuitive operating strategies allowing a significant improvement of the objective function compared to more standard strategies. In particular, the use of a dynamic inclination of the flat-plate collectors (as with a solar tracking device) has proved effective, on the one hand, to increase the energy captured by the solar field and, on the other hand, to handle possible overheating by defocusing the collectors from the maximum energy capture trajectory. The use of a thermal energy storage was also useful to allow the phase difference between production and demand.The formulation of a second optimization problem, over a time horizon of one year, made it possible to minimize the average cost of solar heat sold to the consumer (over the duration of the project) by determining the optimal sizing of the plant and the optimal time profiles of the operating variables as a function of the load curve. Difficulties have been encountered, in particular to maintain consistent operation over the optimization period. Finally, we listed a number of leads that could potentially improve the results obtained
Rabouille, Mickael. "Recherche de la performance en simulation thermique dynamique : application à la réhabilitation des bâtiments." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENA024/document.
The building sector is evolving and has to meet the current environmental issues in both new construction and rehabilitation. The thermal simulation provides the mean to address this problem, but the estimated performance is limited to a specific set of parameters that have been defined. This thesis proposes a methodology based on the increased computing power to assess the building behaviour on different ranges of the inputs variation. Depending on the properties allocated to them, the changes of the variations will allow to seek solutions to restore or to assess the uncertainty in the outputs of the thermal model. To achieve this, effective sensitivity analysis methods are used across an analysis tool specifically developed for the simulation software EnergyPlus. This tool allows an almost automatic evaluation of the energy model building thanks to the proven sampling techniques such as LHS and LP-Tau; the efficient analysis techniques like RBD-FAST and RBD-SOBOL in order to reduce the number of simulations; an advanced management of the inputs and the outputs for a detailed assessment of the building regardless of its geometry. The sensitivity analysis techniques are used to provide an accurate picture of these key relationships within the model. To meet the constraints of the computational cost, the search for a solution is achieved through a metamodel from a Polynomial Chaos Expansion PCE. A GUI uses the approximation of the complex model of the building to provide instantly a clear vision of the behaviour of each entry on the outputs, their trends and their ideal ranges of variation to choose solutions. It is possible to couple the search for a solution to the uncertainty analysis to provide robust solutions and identify the main reason for the gap between simulation and reality. The methodology of the PhD work promotes the optimization of the model understanding more than looking for a specific solution. The purpose of the approach is to provide analytical tools to assist the expert in the search for a solution and so, develop graphical representations that facilitate the understanding of the building system for a gain in transparency and integration of many design constraints
Person, Véronique. "Contribution à l'étude du comportement dynamique et thermique des garnitures mécaniques d'étanchéité." Poitiers, 1997. http://www.theses.fr/1997POIT2300.
Lory, Pierre-François. "Dynamique de réseau et conductivité thermique dans les alliages métalliques complexes." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAY042/document.
Complex metallic alloys are long range ordered materials, characterized by large cells, comprising several hundreds of atoms and cluster building blocks. A key property of CMAs is the low lattice thermal conductivity (1.3 W/m. K), which suggests a potential application for CMAs for thermoelectricity. Despite recent advances structure determination, the nature of the phonons modes remains an open question: do the clusters playing a role? Are there critical modes? To tackle this problem, my PhD project aims to understand the vibrational modes at atomic scale and the relation to lattice thermal conductivity in o-Al13Co4 which is an approximant of the quasicrystal, decagonal phase AlNiCo and the clathrate Ba8Ge40.3Au5.25. In this worked we have used Inelastic Neutron and X-ray Scattering experiments and atomic scale simulations, based on density functional theory and empirical pair potentials.A detailed analysis of the results of inelastic scattering experiments on monocrystals for the acoustic branches have shown, for the first time, a finite lifetime for acoustic phonons when they interact with the low-lying dispersion-less excitations due to atoms in the cluster. In both systems, we observe that when an acoustic branch flattens near the zone boundary, the phonon lifetime is a few picoseconds. The phonon lifetime is approximately independent of temperature like the lattice thermal conductivity. Lattice and molecular dynamics simulations with DFT and empirical, oscillating pair potentials show that the finite phonon lifetime is an anharmonic effect, due to structural disorder, explaining the weak temperature of the phonon lifetime. For o-Al13Co4, we have calculated the thermal conductivity with the Green-Kubo method based on equilibrium MD simulations. For Ba8Ge40.3Au5.25 we have developed a phenomenological model based on individual phonon modes. In conclusion, we have demonstrated how structural complexity affects thermal conductivity through the lattice dynamics
Ellouze, Abderrahmen. "Simulation numérique de la dynamique d'un écoulement en canal ondulé, étude du transfert thermique convectif associé." Pau, 1993. http://www.theses.fr/1993PAUU3026.
Rodler, Auline. "Modélisation dynamique tridimensionnelle avec tache solaire pour la simulation du comportement thermique d’un bâtiment basse consommation." Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0106/document.
Low energy building constructions become sensitive to internal gains : any internal heating source has an impact on the envelope. Therefore, it is important to evaluate the performance of current transient thermal models when adapted to low energy buildings. This work describes a numerical model to simulate a single room, using a refined spatial three-dimensional description of heat conduction in the envelope but a single air node is considered. The model has been developed for environmental conditions that vary over short time-steps and has integrated the projection of solar radiation through a window onto interior walls : the sun patch. The validation of the model has been done through a detailed comparison between model and measurements. The in situ experiment has been carried out in one of the BESTlab cells (EDF R&D). The sun patch has been followed by a camera to validate its calculated position and surface. Temperature measurements by thermocouples and by thermal cameras have been compared to the models outputs. Differences between air and surface temperatures measured and simulated were never above 1.5 ˚C and mean errors reached 0.5 ˚C. The two innovations of the model have then be proven. Using minute wise weather data and inputs associated to an adaptative solver, enabled to pull down simulation errors : in May maximal differences rised from 1 ˚C to 2 ˚C for respectivelly one minute and hourly wise inputs. More important errors are seen in summer whereas in winter, air temperatures simulated tend to more fluctuate around the set up temperature when the sampling step gets longer. Two one dimensional models, close to traditional taken simulation tools, were used. Model M 1D,sol supposed the incoming radiation to reach only the floor. A 1D model with sun patch movement, called 1D,parois , was also used. These two models evaluated the air temperature with an acceptable error. However, their surface temperatures were still subject to important errors. Thus, for temperature surfaces evaluation, both 1D model presented differences up to 20 ˚C for surfaces touched by the sun patch. In winter, the 3D model can predict heating energy consumptions overestimated by 6.5 % when M 1D,parois overestimated them by 11 % and M1D,sol by 22 %. The improvements brought by our model have been proven also for other cells with different thermal masses. For these cells, differences between M1D,sol and the 3D model could reach 4.5 ˚C. Differences seemed to be more important for low thermal mass cells, and the orientation of the building had a strong impact. This work has confirmed the necessity of representing more accuratelly the descriptions of the enveloppe for strongly insulated rooms. To improve the model, the anisothermal hypotheses of the air should be considered
Pham, Minh-Vuong. "Analyse expérimentale : simulation directe et des grandes échelles d'un panache thermique tridimensionnel en rotation." Poitiers, 2005. http://www.theses.fr/2005POIT2287.
Analysis of the thermal plume flows, with or without rotation of its source, constitutes the principal objective of this present report based either on experimental investigations or on direct (DNS) and large-eddy simulations (LES). Under static condition, it was shown that the movement is driven by expulsion and contraction phases in the lateral direction. These mechanisms are directly generated by convection of coherent original thermal structures which develops vicinity of the thermal plume. Several subgrid models were proposed in the LES and a lagrangian "thermal" model was proposed and the whole of the principal characteristics of a turbulent thermal plume was perfectly described. The rotation of the heated source generates a shear layer which accelerates the breaking down of coherent structures. The classical laws are still valid under rotating conditions however their characteristics are modified when the rotating velocities are above a critical value. Entrainment mechanisms, through contraction and expulsion phases, are also amplified under the influence of rotation
Launay, Stephen. "Performances thermiques de microcaloducs usinés dans le silicium : modélisation et étude expérimentale." Lyon, INSA, 2002. http://www.theses.fr/2002ISAL0004.
Thermal performance of silicon micro heat pipe (MHP) arrays have been studied experimentally and numerically in the present work. A numerical model has been developed in order to simulate the hydrodynamic and thermal behaviour of a water MHP array, whose cross sectional area is triangular. Capillary limit, optimal fluid charge and temperature profiles can be determined according to the geometry. Several silicon MHP arrays have been designed and realised (with the collaboration of LPM and LPCS). The MHP array is made of two silicon wafers of 350 µm thick. V-grooves have been micromachined in the first one using an anisotropic wet-chemical etching (KOH). On the second wafer, used to close the MHP (by fusion bonding with the first wafer), polysilicon thermistors are deposited on the external side. Two experimental set up have been realised for the experimental study. The first one permits to degass the fluid, to charge the MHP array and to measure the charge ; the other one is used to determine the thermal performances of several MHP arrays. For a MHP array made of three wafers and filled with methanol, the temperature profiles and the heat load allow to determine, using a 3D-model, the effective thermal conductivity. Comparing with a silicon wafer (with a same thickness), a noticeable increase in the effective thermal conductivity (about 300 %) is obtained
Lahbib, Dorian. "Modélisation aérodynamique et thermique des multiperforations en LES." Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTS287.
Effusion cooling is frequently used to lower the thermal constraints of the combustion chambers in aeronautical gas turbines. It consists of injecting a cold air flow through submillimetric holes drilled in the combustor liners. The resolution of the flow in the near-wall regions in 3-D combustion chamber calculations is out of reach in terms of computational cost due to the presence of small scales. Models were proposed to reduce the computational cost in previous works. An adiabatic homogeneous model, to represent the aerodynamics around the plate, based on the resolved Large Eddy Simulation of an infinite perforated plate was proposed. It was later extended to model the aerothermal behavior of the flow, based on spatially resolved RANS calculations. The objectives of this work are to evaluate the homogeneous aerothermal predictions regarding the flux reparation and to propose a model to account for effusion cooling in industrial computations of the flow around the perforated plate. Large Eddy Simulations coupled with a thermal solver have been performed in order to get insight of the flow organization and the heat flux repartition around the plate. Two configurations at a representative aero engine operating point are studied: two channels separated by 12 converging rows with either perforations oriented in the main flow direction or with an angle of deviation. The data from the Large Eddy Simulations have been compared with the homogeneous model and a methodology is proposed to tackle the heat flux miscalculation due to the numerical implementation. This methodology is not limited to the homogeneous approach, it extends to other approaches such as an hybrid model presented in this work which represents enlarged holes based on the size of the cell relative to the hole diameter. The hybrid model switches from a homogeneous representation of the perforations to a heterogeneous representation and encouraging results are obtained for both configurations
Fargère, Romain. "Simulation du comportement dynamique des transmissions par engrenages sur paliers hydrodynamiques." Phd thesis, INSA de Lyon, 2012. http://tel.archives-ouvertes.fr/tel-00833202.
Mouawad, Grace. "Modélisation et méthodologie de conception d'un four de traitement thermique rapide." Thesis, Paris, ENMP, 2012. http://www.theses.fr/2012ENMP0110.
During the rapid thermal processing (RTP) of thin film photovoltaic cells, the temperature of the latter has to follow a preset time evolution profile, while keeping spatial uniformity of the wafer. The aim of this study is to propose a design methodology of RTP furnace in order to obtain the quality of the required heating cycle.A thermal modeling is performed based on the component interaction network approach to predict the thermal behavior of the furnace. Flux plane approximation and semi-transparent thin layer approximation are used to calculate the direct exchange factor. The plating algorithm is then applied to calculate the transfer factor. The thermal model developed is validated experimentally on a furnace of small dimensions. A methodology to design a RTP furnace is proposed taking into account the dynamic aspect of the thermal conditions of the furnace. An optimization using the genetic algorithm is performed in order to find emitter dispositions. For each tested configuration, the optimal input power distribution over the emitters at each time step is found by using real time dynamic programming. Finally, the methodology is applied for the design of RTP furnace for the heat treatment of thin film photovoltaic cells of 30 × 60 cm2. Test results confirm the validity of the methodology proposed
Chahwane, Layal. "Valorisation de l'inertie thermique pour la performance énergétique des bâtiments." Phd thesis, Université de Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00701170.
Rishmany, Jihad. "Comportement statique et dynamique d'une structure périodique 3d d'un échangeur aéronautique : étude expérimentale, modélisation et simulations numériques." Toulouse 3, 2007. http://www.theses.fr/2007TOU30032.
Aeronautical heat exchangers are subjected to a complex environment combining pressure, temperature and vibrations. The objective of this thesis is the analysis of the static and dynamic behavior of the core of an exchanger. The core is a 3D-periodic complex structure composed of an alternate stacking of fins where passes the hot and cold air respectively. Various analytical and numerical approaches based on the study of a basic cell of the structure are employed to model the global static behavior of the core at 20 and 350°C. Static results are validated by experimental tests on various types of specimens. At the end of this part, two models are proposed to replace the real structure of the core : a «homogeneous» model and a «laminated» model. The dynamic study, experimental and numerical, shows that these two models are capable of predicting satisfactorily the dynamic behavior of the core
Bizzari, Romain. "Modélisation aérodynamique et thermique des plaques multiperforées en LES." Thesis, Toulouse, INPT, 2018. http://www.theses.fr/2018INPT0101/document.
Numerical simulation is progressively taking importance in the design of an aero- nautical engine. However, concerning the particular case of cooling devices, the high number of sub-millimetric cooling holes is an obstacle for computational sim- ulations. A classical approach goes through the modelling of the effusion cooling by homogenisation. It allows to simulate a full combustor but failsin representing the jet penetration and mixing. A new approach named thickened-hole model was developed during this thesis to overcome this issue. A work on improving the mesh resolution onkey areas thanks to an automatic adaptive method is also presented, leading to a clear breakthrough. In parallel, as the flame tube temperature is a cornerstone for the combustor durability,a low-cost approach is proposed to predict it. To meet the time-constraints of design, it is based on thermal modelling instead of a direct thermal resolution
Ali, Samer. "Concept innovant d'échangeur/réacteur multifonctionnel par contrôle dynamique passif par générateurs de vorticité flexibles." Thesis, Valenciennes, 2015. http://www.theses.fr/2015VALE0034/document.
The aim of this study is to investigate the use of fluid-structure interaction (FSI) to improve heat transfer and mixing performances in multi-functional heat exchangers/reactors, and to evaluate configuration designs where the main target is to produce and maintain self-sustained oscillations of flexible vortex generators. At first, two dimensional laminar flow studies are numerically investigated. The results show that a minimum of three alternating flaps is needed to produce an instability that leads to large displacement oscillations. However, the introduction of two co-planar flaps upstream destabilizes the flow by creating periodic forces that act on the alternating downstream flaps. Hence, this results in artificially increasing the reduced velocity that will induce the alternating flaps to be in a lock-in state. Thus in this case, large displacement amplitudes are created with two alternating flaps only. The free flaps oscillations produce vortices of higher strength which have a positive impact on heat transfer and mixing. Secondly, a three dimensional HEV configuration with flexible trapezoidal vortex generators inclined with an angle of 45◦ with respect to the wall and reversed opposite to the flow direction is numerically investigated. Fast Fourier Transformation is applied on the temporal variation of the Proper Orthogonal Decomposition (POD) coefficientswhich displays a dominant peak in the flow and corresponds to the vortices periodic formation and detachment. This dominant frequency synchronizes well with the structural oscillation frequency and the fundamental frequency of the tabs reaching a lock-in state and leading to large oscillation amplitudes
Mathelin, Lionel Lallemand André Daumas-Bataille Françoise. "Etude numérique, expérimentale et théorique de l'influence de l'effusion sur la dynamique et la thermique de l'écoulement autour d'un cylindre circulaire poreux." Villeurbanne : Doc'INSA, 2006. http://docinsa.insa-lyon.fr/these/pont.php?id=mathelin.
Fargere, Romain. "Simulation du comportement dynamique des transmissions par engrenages sur paliers hydrodynamiques." Thesis, Lyon, INSA, 2012. http://www.theses.fr/2012ISAL0130/document.
The present work is aimed at predicting the dynamic behaviour of geared transmissions supported by hydrodynamic journal bearings, similar to those used in naval propulsion. A global model of mechanical transmissions is introduced which deals with most of the possible interactions between gears, shafts and hydrodynamic journal bearings. A specific element for wide-faced gears with non linear time-varying mesh stiffness and tooth shape deviations is combined with shaft finite elements whereas the bearing contributions are introduced based on the direct solution of REYNOLDS’ equation and a simple thermal model. Because of the large bearing clearances, particular attention has been paid to the definition of the degrees-of-freedom and their datum. Solutions are derived by combining a time-step integration scheme, a NEWTON-RAPHSON method and a normal contact algorithm in such a way that the contact conditions in the bearings and on the gear teeth are simultaneously dealt with. The simulation results are compared with the measurement obtained on a high-precision test rig with single stage spur and helical gears supported by hydrodynamic journal bearings. The experimental and simulation results compare well thus validating the simulation strategy both at the global and local scales. A number of results are presented which show that parameters often discarded in global models such as the location of the oil inlet area, the oil temperature in the bearings and external couplings with mechanical parts can be influential on the static and dynamic behaviour of the system
Gloriant, François. "Caractérisation et modélisation d'une fenêtre parieto-dynamique à trois vitrages." Thesis, Artois, 2014. http://www.theses.fr/2014ARTO0205/document.
The ventilated window is a passive system of heat recovery. It draws fresh air circulating between window’s glasses from the outside to the inside. A part of the heat which crosses the glasses is then recovered by the air flow. The Paziaud® window is composed of three glasses separated by ventilated air spaces in U-shape. While the implementation of a double-flow ventilation system for the housing retrofitting is complex, this Paziaud® window costs only 20% more than a conventional double-glazed window but improves significantly the heat recovery.In order to study the performance of the Paziaud® window, numerical and experimental works have been undertaken and have confirmed the potentiality of such windows. However, a thermal code able to take into account the heat exchange is not available for such system. Considering this lack of simulations, several simplified models based on electrical analogy have been developed. Particular attention is paid to the convective exchange process in the ventilated air spaces. The numerical results could validate a simplified thermal model which can be integrated to the building codes
Mathelin, Lionel. "Etude numérique, expérimentale et théorique de l'influence de l'effusion sur la dynamique et la thermique de l'écoulement autour d'un cylindre circulaire poreux." Lyon, INSA, 2001. http://theses.insa-lyon.fr/publication/2001ISAL0028/these.pdf.
This work is concerned about the numerical and experimental study of the flow and heat transfer over a porous circular cylinder in cross-flow submitted to non-isothermal blowing (internal flow). Flow regimes are steady and unsteady, laminar and turbulent. Two blowing models are proposed. The experiments allow for numerical simulation and blowing models validation. In particular, using hot- and cold-wire anemometry, velocity and temperature profiles are compared with numerical simulations. A coupling between internal flow within the porous matrix and external flow over the cylinder is achieved, in the form of an user defined function of the code accounting for radiative heat transfer, to determine the equilibrium wall temperature. Performances of liquid injection (transpiration cooling) are experimentally evaluated with water and ethanol and prove excellent thermal protection effectiveness of the process. Moreover, the blowing influence on instabilities influence on instabilities is studied. It is seen that the blowing lowers the primary and secondary vortex shedding frequency and modifies the shear layer structure. In case of blowing, a series of peaks appears. Using the linear stability theory, it is shown that growth rates are significantly affected by blowing and that the near wake structure, and the absolutely convective zone in particular, is modified. Finally, performed 3-D numerical simulations lead to the conclusion that blowing reduces tri-dimensional effects
Gueye, Abdoulaye. "Modélisation et simulations numériques des écoulements et instabilités thermiques de fluides non-Newtonien en milieu poreux." Thesis, Lille 1, 2015. http://www.theses.fr/2015LIL10154/document.
The present thesis on porous media concentrates in two parts. The first concerns the numerical study of the flow of a Newtonian or a non-Newtonian fluid within a fluid/porous system. The approach of a single domain, which consists of/in writing the Navier-Stokes equation including the Darcy-Brinkham-Forchheimer term, is chosen in this study. The linear relation between the pressure gradient and the bulk velocity in the Darcy case, for which the fluid is Newtonian, is obtained. This relation is extended to the non-Darcy case, for which the fluid is non-Newtonian. The influence of Darcy and Forchheimer numbers on the structure of the flow is presented. In the second part, linear stability and numerical analysis of the natural convection of viscoelastic fluids saturating a horizontal porous layer heated by a constant flux is performed. A primary and secondary instability study allowed to show that, for a Newtonian fluid, the unicellular convection loses its stability to the benefit of longitudinal rolls. In the case of viscoelastic fluids, the elasticity of the fluid leads to the selection of propagation transverse rolls. A numerical solution based on a finite difference scheme has reinforced these analytical results
Batier, Cécile. "Confort thermique et énergie dans l’habitat social en milieu méditerranéen : d'un modèle comportemental de l’occupant vers des stratégies architecturales." Thesis, Montpellier, 2016. http://www.theses.fr/2016MONTS019/document.
The current design of energy-efficient buildings used to be performed by dynamic thermal simulations using conventional hypotheses like those of the 2012 French thermal regulations (weather reports, occupancy, temperature set, operations of windows and shutters by occupants, etc...). However, feedback highlights a great difference in energy consumption between forecasts on the one hand and in situ measurements in winter as well as overheating in summer on the other hand. According to the scientific community, even if many factors can account for this gap, the inhabitants seem to play a major role in it as well. Indeed, by acting on their windows and shutters, they modify the renewal rate of fresh air and the management of solar contributions. As the matter of fact, the use and the type of windows and shutters affect the energy consumptions and the comfort. The aim of this study is to analyse the thermal evolution of occupied apartments in order to establish a behavioral model of the occupants. This will allow us to quantify the impact of architectural modifications on the thermal comfort and the energy performances of buildings.Two residential buildings are investigated in Vauvert (a city in southern of France). Both of them were built in 1969 using the same constructive techniques and have lately been renovated in a similar way (CMV, boilers, windows). The only difference is that on the facade of one of them an external thermal insulation has recently been installed. The analysis of the real thermal conditions, of the actual human behavior and of the amount of energy consumed is built on surveys and on an extensive year-round in situ instrumentation in the living rooms of 13 apartments. It allows us to define a behavioral model of occupants based on 32 different combinations in the operations of windows and shutters. We can divide them into three occupants' profiles (the “expert” occupant, the “active” occupant and the “counterproductive” occupant). Digital Pléiades+COMFIE simulations are made in order to validate this model. The refined modeling of the dynamic thermal simulation parameters helps to understand the impact on the thermal comfort and the energy consumption of different architectural strategies in the Mediterranean area.In winter the thermal analysis of the two residential buildings (insulated and non insulated) shows similar levels of consumption, but a lower level of thermal comfort in the non insulated case. However during temperature peaks in summer, overheating appears in the insulated dwellings, but human behavior is the key to limit occupants’ discomfort. The analysis of in situ measurements shows that strategies to cool down the apartments are not always implemented by occupants. Architectural solutions mitigating “counterproductive” occupants’ behavior are finally examined
Guyot, Dimitri. "Evaluation sur modèle de simulation thermique dynamique calibré des performances d’un contrôleur prédictif basé sur l’utilisation de réseaux de neurones." Thesis, Paris, HESAM, 2020. http://www.theses.fr/2020HESAC022.
The development of machine learning techniques, particularly neural networks, combined with the development of new information and communication technologies, is shaking up our societies through technological advances in a variety of sectors. The building sector is not spared, so these techniques may represent an interesting opportunity in a context where greenhouse gas emissions must be drastically reduced. The objective of this work is to assess the interest of these techniques in the field of building energy, with the aim of reducing energy consumption and improving thermal comfort. In addition, we ensure that this evaluation is carried out with a global vision, by placing the possible advantages in front of the different needs relating to the development of these technologies. This thesis work is organized in three parts preceded by a detailed introduction intended to give the reader an overview of the various contextual elements, thus allowing the thesis work to be placed in perspective. We then give in the first part the theoretical framework needed to understand the problems encountered during the elaboration and creation of neural networks for building energy applications. Then, a bibliographical study giving the reader a broad overview of the various applications of neural networks in the field of building energy is presented. The second part is devoted to the calibration of the building model that is then used to test and evaluate a predictive controller implementing neural networks. After an explanation of the method used and a detailed presentation of the model, a complete analysis of the calibration results is carried out. We conclude this part with observations and recommendations regarding the standard calibration guidelines recommended by three international organizations. Finally, a practical application using neural networks for the predictive control of indoor temperature is presented in the third part. After a theoretical introduction concerning predictive control, we detail the method employed to train the neural networks used. The results obtained in simulation with a predictive controller are then analyzed and compared with those obtained with two reference controllers for various simulation hypothesis. The predictive controller is thus tested in several scenarios, ranging from an ideal situation to more realistic operating conditions, including two different types of heat emitters, namely radiant ceilings and underfloor heating
Salmon, Élodie. "Étude des mécanismes du craquage thermique par simulation dynamique moléculaire de géopolymères organiques avec un champ de force réactif (ReaxFF)." Thesis, Vandoeuvre-les-Nancy, INPL, 2008. http://www.theses.fr/2008INPL003N/document.
Kerogen, the insoluble fraction of sedimentary organic matter, is a complex mixing of organic macromolecules, the structure of which evolves during geological times as a function of temperature mainly. The thermal evolution of kerogen is at the origin of hydrocarbon deposits in sedimentary basins. Understanding and quantifying the physicochemical processes associated to this transformation is therefore important to improve the evaluation of petroleum systems. During this study, two geopolymers were selected in order to represent the thermal decomposition of typical structures in natural kerogen. Firstly, an experimental protocol was set up (1) to define molecular structures of the geopolymers, and (2) to describe primary mechanisms of decomposition of both geopolymers. The two samples were analysed using off-line pyrolysis experiments, at five reference temperatures comprised between 200 to 300°C. A kinetic scheme accounting for early decomposition processes was derived from these experimental observations for each geopolymer. Secondly, molecular models were submitted to molecular dynamic simulations using a reactive force field (ReaxFF). ReaxFF simulations provided theoretical supports to the key-processes derived from laboratory experiments. On the overall, results of this study suggested that kinetic models in one step (= parallels reactions implemented in standard (commercial) basin simulators do not adequately reproduce the physicochemistry of organic matter decomposition processes in natural source rocks
Salmon, Élodie Marquaire Paul-Marie. "Étude des mécanismes du craquage thermique par simulation dynamique moléculaire de géopolymères organiques avec un champ de force réactif (ReaxFF)." S. l. : INPL, 2008. http://www.scd.inpl-nancy.fr/theses/2008_SALMON_E.pdf.
Rishmany, Jihad. "COMPORTEMENT STATIQUE ET DYNAMIQUE D'UNE STRUCTURE PERIODIQUE 3D D'UN ECHANGEUR AERONAUTIQUE : ÉTUDE EXPERIMENTALE, MODELISATION ET SIMULATIONS NUMERIQUES." Phd thesis, Université Paul Sabatier - Toulouse III, 2007. http://tel.archives-ouvertes.fr/tel-00175832.
Vu, Van Huyen. "Modélisation hybride et multi-échelle pour la simulation des écoulements et des transferts thermiques dans les micro-canaux." Thesis, Paris Est, 2016. http://www.theses.fr/2016PESC1163/document.
The main objective of this thesis is to model the multi-scale heat and fluid flows in micro-/nano channels. This method must be able of capturing at the same time the fluid/solid interaction at the small scale but also the flows induced by the inlet/outlet boundary conditions at the large scale. To this aim, we have adopted an approach coupling the continuum model in the bulks of the channel and the discrete model at the vicinity of the wall, based on an atomistic representation of the fluid and the solid.The Navier-Stokes and energy equations, coupled with an equation of state, are approximated by a finite volume method and the molecular dynamics simulations are used to finely represent the interaction between the fluid and the solid. This hybrid method requires information transmission between the former two regions: averaged quantity in molecular dynamics simulations are imposed as boundary conditions for the continuous model and constrained dynamics, coupled with a thermostat Langevin, is used to control in the molecular level. A set of small molecular dynamics blocks, smartly distributed all along the wall/fluid interface, allows to treat flow and heat transfers in a long micro/nano-channel with a reasonable computational cost.After a validation step, the hybrid multi-scale simulations of complex fluid flows in the channel composed of the platinum wall have been conducted for argon in incompressible liquid or compressible gaseous phase with and without phase change in the vicinity of the wall
Marcault, Emmanuel. "Contribution à l'intégration d'un indicateur de vieillissement lié à l'état mécanique de composants électroniques de puissance." Phd thesis, INSA de Toulouse, 2012. http://tel.archives-ouvertes.fr/tel-00728764.
Lemerini, Mostefa. "Modelisation et simulation numerique de l'empreinte thermique d'une decharge pointe-plan dans l'air. Application a l'etude de la dynamique des neutres." Université Louis Pasteur (Strasbourg) (1971-2008), 1993. http://www.theses.fr/1993STR13157.
Peter, Simone. "Structure and relaxation of thin glass forming polymer films." Université Louis Pasteur (Strasbourg) (1971-2008), 2007. https://publication-theses.unistra.fr/public/theses_doctorat/2007/PETER_Simone_2007.pdf.
Francioso, Pierre-Arnaud. "Détermination de la résistance thermique d'une interface cristal/amorphe à l'aide de la dynamique moléculaire classique." Thesis, Lille 1, 2014. http://www.theses.fr/2014LIL10210/document.
Since the 60s, the history of crystalline silicon cSi and its oxyde (silica, aSiO2) is driven by the emergence of the new transistors. The miniaturization of these technologies, which enabled an increase in computers performances closely related to the Moore law, implies nowadays a nanometric scale comprehension of the physics in these systems. Because of the important costs of nanoscale experiments, numerical simulations and especially molecular dynamics (MD) are often used as a first-choice tool to investigate this kind of problems. In this thesis, we also apply classical MD to the case of silicon-on-insulator (SOI) transistors in order to determine the Kapitza resistance of a cSi-aSiO2 interface, which could be a source of slowdown for the thermal dissipation in ultra thin body and box (UTB²) transistors. We first expose the principle of classical MD (chapter 1) and show some ideas to optimize the neighbour search algorithms (chapter 2). In chapter 3 we explain the steps to form our silicon-silica systems and propose a way to characterize the interface. Finally, in chapter 4 we develop a method – called approach-to-equilibrium molecular dynamics (AEMD) – which allows us to estimate the value of the interfacial resistance interface to be 3.6*10-10 m2.K.W-1
Courbon, Cédric. "Vers une modélisation physique de la coupe des aciers spéciaux : intégration du comportement métallurgique et des phénomènes tribologiques et thermiques aux interfaces." Phd thesis, Ecole Centrale de Lyon, 2011. http://tel.archives-ouvertes.fr/tel-00713527.
Lin, Qinglong. "Etude, modélisation dynamique et développement d'un capteur solaire thermique à concentration de nouvelle génération." Thesis, Aix-Marseille 1, 2011. http://www.theses.fr/2011AIX10099.
This work is for the purpose to develop a new solar concentrating technology. It covers the presentation of the concept, the prototype realization and the optical and energy study of a new solar concentrator QingSun™. This concentrator has a shape of rectangular parallelepiped and includes linear Fresnel lenses, mirror-lined walls and a mobile solar receptor controlled by a tracking system inside the casing. An optical model and an energy model were developed and validated with a series of experiments. The both models permitted us to examine the function and the energy performance of the concentrator. A parametric study of the influence of the tilt and the orientation was performed and showed that the tilt had more influence than the orientation. Finally, the optimal energy performance of this concentrator was estimated
Elia, Marc. "Etude de la stabilité thermique dans les réacteurs chimiques." Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4707/document.
In refining and petrochemistry process safety is a major issue. For highly exothermic processes it is necessary to ensure in a rigorous way the safe that the process operates in safe conditions, hence avoiding thermal runaway. The objective of this thesis was to develop a methodology to determine the operating conditions of reliable operation of chemical reactors. The methodology relies on stationary and dynamic analysis. The stationary stability analysis based on the Van Heerden criterion was generalized to complex chemical systems. The dynamic analysis applies the perturbation theory to definitely determine if a stationary point is stable according to eigenvalue analysis.The methodology was applied to ebullated-bed technology for residue hydroconversion at pilot and industrial scale. Two comprehensive dynamic models that accurately represent the ebullated-bed pilot plant and industrial process were developed for the study. The models take into account a detailed description of the reactive system and the configuration of the pilot and industrial plants: three phases, kinetics and flow characterization. A stationary and dynamic thermal stability analysis was carried out for both configurations and stable/unstable operating regions were identified. The study showed that the pilot plant reactor can operate in a larger domain of operating conditions compared to the industrial reactor while the parameters have the same effect on both reactors. The resulting reactor operation diagrams are a essential guide for engineers in the reactor design and operation practice
Kassem, Wassim. "Direct molecular dynamics simulation of piezoelectric and piezothermal couplings in crystals." Thesis, Châtenay-Malabry, Ecole centrale de Paris, 2015. http://www.theses.fr/2015ECAP0043/document.
The thesis is focused on investigating the effect of strain on the thermal conductivity of piezoelectric materials. Piezoelectric materials are crystals which display a mechanical deformation upon application of an electric field. Examples of such material are ZnO, AlN, and SiO2. Using Molecular Dynamics simulations, we calculate the thermal conductivity of unstrained and strained ZnO and AlN crystals. We also calculate the thermal resistance of SiO/graphene interfaces under strain.We calculate the piezoelectric and elastic properties of ZnO. These will serve as confirmation of the correctness of the inter-atomic potential used, and will serve to show the magnitude of strain that is possible to apply. Using non-equilibrium molecular dynamics, we determine the elastic coefficient of ZnO c33, and we see that it agrees with experimental values. We also determine that the elastic limit of a perfect ZnO crystal is 6 GPa which corresponds to a 6% strain. We also determine the piezoelectric coefficient of ZnO using NEMD, and we find that the piezoelectric coefficient d33 also agrees with literature values.Second, we look at the effect of strain on the intrinsic thermal conductivity of ZnO and AlN. We use reverse non-equilibrium molecular dynamics to calculate the conductivity because the computational costs are significantly lower than those for the equilibrium method; especially for ZnO whose inter-atomic potential contains Coulomb interaction. We also study the size-effect on the thermal conductivity of ZnO and AlN. We show that the Schelling formula can indeed be implemented to both crystals for different values of strain. The infinite length thermal conductivity for ZnO is extracted from the formula, and it is found to be 410 W/mK. We then calculate the thermal conductivity of strained ZnO crystals. We show that after correcting for the size effect the thermal conductivity follows power-law dependence to uniaxial strain. Also, we demonstrate that the thermal conductivity of ZnO can be affected by a static external field due to the induced strain. The infinite length thermal conductivity of AlN is found to be 3000 W/mK. We show that for the case of AlN the effect of strain does not affect the thermal conductivity due to the different inter-atomic bonding. Hence, AlN might not be a useful material for piezothermal application.Third, we explore the effect of piezoelectric strain on the thermal conductance of SiO2/graphene and ZnO/graphene superlattices. Using EMD we calculate the thermal conductivity of a superlattice composed of silica and graphene monolayers. The thermal conductance of the superlattice was evaluated under different values of external electric field. We find that applying a positive electric field parallel to the Z-direction leads to reduction of the thermal conductance by a factor of 2 for an electric field of 20 MV/m. On the other hand, no change in the thermal conductance is noted for ZnO/graphene superlattice. The effect is due to the non-uniform strain induced at the superlattice junctions. The effect is recreated in Si/Ge superlattice by mechanically applying a non-uniform strain at the interface. This approach might be responsible for the scattering of phonons
Tchekiken, Chahinez. "Modélisation et simulations numériques d’écoulements compressibles dans des micro-conduites planes." Thesis, Paris Est, 2014. http://www.theses.fr/2014PEST1109/document.
These phenomena are rarely taken into account all at once, at least one of them is neglected and often without justification. Our approach is to get as close as possible to reality by taking into account all the phenomena that appear at once and then to study the effect of the phenomena most often overlooked. First, the study is conducted using a commercial code for solving the conservation equations by the finite volume method. Validations were performed for problems ranging from the simplest (incompressible, non-slip flow) to the more complex (compressible, slip flow). This study highlighted the problems associated with simulations when the flows Peclet numbers are less than unity (Pe <1). In this case, the inverse diffusion effects are dominant and the use of extensions at the upstream becomes unavoidable. In addition, compressibility effects were identified; they have resulted in expansions of the gas near the exit of the pipe (acceleration + cooling). Finally, comparisons were made with analytical solutions of compressible slip flows assumed isothermal by imposing small variations of pressure. We showed that these solutions remain valid even if the pressure variations are important because the detents are located only near the exit of the pipe. In this case, they do not affect the properties of the flow. Further works were carried out using an in-house computer code, previously developed and validated in the laboratory for flows with large scales and for which slipping limits conditions have been added so that it can properly resolve slip flows. In view of its accuracy and performances in terms of CPU-time, the code allowed us to achieve a parametric study on a wide range of input and output pressures, so as to sweep all runoff from few to very compressible and few to very slip flow. The results were first presented for quasi-isothermal flow, which subsequently were compared to analytical solutions to test these ones on a wider range of pressure. Finally, the results were made for heated flows. Correlations have been obtained for a complete model using a statistical based software and design of experiments. Comparisons to simplified models were performed to assess the inaccuracies linked to the omission of terms often overlooked in the literature
Davier, Brice. "Theoretical study of thermoelectric properties in nanostructures." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS529/document.
Thermoelectric generators are able to directly convert heat into electrical energy. They could have a great potential in terms of energy harvesting, but unfortunately, the best thermoelectric materials are rare and pollutant.Silicon and Germanium would be attractive materials if their thermoelectric efficiency were improved. For this purpose, nanostructuring is a possible route, for instance via the introduction of rough boundaries or interfaces between materials.Recently, polytype nanowires (composed of a sequence of cubic and hexagonal phases of Si and Ge) have been fabricated, but the experimental characterization of such complex nanostructures with exotic materials is challenging.In this thesis, we study the details of thermal transport in nanostructures with numerical simulations. An original Monte Carlo method is developed, with a full band emph{ab initio} description of materials. It includes models for the rough boundaries and the solid-solid interfaces. Molecular Dynamics simulations are also performed to characterize the properties of interfaces.We confirm that the hexagonal phases of Si and Ge have lower thermal conductivity than their cubic counterparts. The full band model shows a strong anisotropy in the heat flux.Usual semi-analytical models failed to reproduce the thermal conductivity of simulated nanostructures with rough boundaries. Besides, those boundaries tend to focus the heat flux in the main direction of the nanostructure. Finally, some polytype interfaces can have an interfacial conductance almost as low as Si/Ge interfaces, and thus could improve significantly the thermoelectric efficiency of polytype nanowires. The presented Monte Carlo method could easily be used with a wide range of materials,and it can model arbitrarily complex nanostructures. In the future, the results from Molecular Dynamics simulation will be used to parametrize a more realistic model of solid-solid interfaces
Ngono, Mebenga Frédéric. "Investigations from experiments and simulations of amorphous forms of lactulose obtained by different routes." Electronic Thesis or Diss., Lille 1, 2017. http://www.theses.fr/2017LIL10213.
In this thesis, we have investigated the influence of the amorphisation route on the physical and chemical properties of lactulose. This sugar has the characteristic of being able to exist in several different tautomeric forms. Four amorphisation routes very different in their principle have been studied: quenching from the melt, freeze-drying, spray-drying and mechanical milling. The results indicate that the amorphisation route used has a direct effect on the tautomeric composition of the material. The influence of this composition on the glass transition of the amorphous material has been studied in detail. Moreover, the eventual structural differences generated by the various amorphisation routes have been studied both by neutron scattering and by simulation (molecular dynamics). The results indicate the existence of a particular locally ordered structure in the amorphous material obtained by spray-drying which seems to be able to explain the higher degree of stability of the amorphous material obtained by this route. Furthermore, the amorphisation kinetic induced directly in the solid state by a high energy mechanical milling has been characterised in detail. This has required the use of an original method of isothermal calorimetry of dissolution
Seck, Cheikh. "Analyse et modélisation du comportement thermique d'un système de préchauffage d'air neuf pour l'habitat, intégrant un matériau à changement de phase." Thesis, Artois, 2010. http://www.theses.fr/2010ARTO0204.
The objective of this thesis is to study an integrated energy system in the building envelope for fresh air preheating. The originality of the work is that the wall is equipped with phase-change material (MCP) packed into briquettes. The main role ofthe wall is to preheat the fresh air (coming from outside) by destocking the solar energy captured in sunny periods.Our study consists of two phases, an experimental phase and a numerical one. The experimental phase involves a series of tests that allow studying the thermal behaviour of the system under thermal stress. These tests were done in laboratory through a prototype of the wall which is instrumented and installed between two airconditioned cells.The purpose of the numerical phase is to develop a one-dimensional model to simulate the thermal behaviour of the wall and especially that of MCP. This model has been validated by comparing numerical results with those obtained experimentally. To model the phase changing we used the thermophysical parameters of the same material obtained by experimental characterization conducted in our laboratory.We used a variable capacity method whose principle is to vary the heat capacity as a function of temperature in order to simulate the phase changing of the wall. The last part of the numerical work is the exploitation of the model, the aim is to determine the optimal configuration of the wall that provides maximum energy savings. Dynamic simulation of the system was performed using the TRNSYS. This one is equipped with weather files which allow carrying out heat balances and the estimation of the system efficiency for various climates
Zuñiga, Ulloa Ruben. "Études numérique et expérimentale des transferts couplés masse-chaleur modélisation, simulation et optimisation d'un traitement thermique dynamique de surface d'un produit alimentaire." Nantes, 2005. http://www.theses.fr/2005NANT2039.
This work concerns the decontamination of the surface of a food, consisting in blowing hot air onto the food surface with the objective of inactivating the bacteria located on the surface. This process has a renewal of interest but it is still a challenge to accurately control the evolution of the surface temperature. In this aim, a coupled heat and mass transfer model has been developed taking into account convective and diffusive mechanisms, evaporation and shrinkage of the product during the treatment. It also accommodates the dependence of the thermal properties with the moisture content. A specific heat treatment chamber was used to validate the model. Some parameters of the model were taken from the literature whereas the convective heat transfer coefficient was experimentally determined. From simulations, we highlighted the great influence of the water diffusivity on the surface temperature prediction. Reverse methods were then used to optimize this parameter and we pointed out its correlation with the convective heat transfer. Finally, this model was used as a simulator to design a control law allowing surface temperature tracking. This algorithm required the knowledge of an internal temperature, which was supplied by a software sensor
Rivalin, Lisa. "Vers une démarche de garantie des consommations énergétiques dans les bâtiments neufs : Méthodes d'évaluation des incertitudes associées à la simulation thermique dynamique dans le processus de conception et de réalisation." Thesis, Paris Sciences et Lettres (ComUE), 2016. http://www.theses.fr/2016PSLEM007/document.
Before the construction of a building, an energy performance guarantee consists in predicting the energy required for user comfort. To do that, it is necessary to state a contractual consumption and identify the key parameters to pay special attention to. Thus, for new buildings, consumption is calculated under design phase, when several data are uncertain. Thus, the dynamic thermal simulation is carried out with hypothetical data, without having the possibility to calibrate with measures.This PhD thesis aims to develop a method of uncertainty quantification during the design step and construction process of a new building. These uncertainties are classified into three categories: those associated with the calculation methods used for building and system modeling, those related to the lack of knowledge of model parameters and those due to the real use conditions of the building (occupancy and weather).To achieve this goal, uncertainties associated with the calculation methods are addressed, to identify some practices limiting the number of errors and the associated uncertainties. Then, a methodology is defined to choose the critical parameters used for the probabilistic study and to associate them with a distribution according to the available knowledge. The central part of this PhD thesis is dedicated to an exhaustive comparison of methods to select a fast uncertainty propagation and sensitivity analysis method. Finally, after illustrating the overall contracting approach and discussing the inclusion of financial risks, the method is applied on a real case, on which an adjustment formula is added to take into account actual weather and usage