Le procédé de soudage TIG est actuellement le plus utilisé dans l’industrie aéronautique du fait de la qualité des joints de soudure qu’il permet d’obtenir et de sa simplicité d’automatisation. Une opération de soudage provoque des gradients thermiques dus au passage de la source de chaleur sur la pièce qui induisent des déformations et des contraintes résiduelles pouvant impacter la durée de vie de l’assemblage. Ce travail vise à mettre en place un modèle de simulation de ce procédé dans le but d’optimiser les paramètres opératoires.Avant d’envisager un couplage thermomécanique, il convient de représenter convenablement les transferts thermiques au cours du soudage et en particulier l’apport de chaleur lié au procédé. Dans cette étude, on propose une source de chaleur prédictive simplifiée représentative des paramètres opératoires qui permet en particulier d’estimer les dimensions caractéristiques du cordon de soudure et de traduire fidèlement l’évolution thermique dans la pièce. Cette source est définie par un flux de chaleur homogène dépendant d’une puissance P, réparti sur un disque de rayon R, ces 2 paramètres numériques étant liés aux principaux paramètres opératoires de soudage que sont l’intensité I et la hauteur d’arc h.Une campagne d’essais expérimentaux dans laquelle on étudie les variations des dimensions de la Zone Fondue (ZF) pour des cas non pénétrants et pénétrants en fonction des paramètres opératoires (I, h) est présentée. Pour chaque essai, un couple de paramètres d’entrée de la source de chaleur (P, R) permettant de reproduire les dimensions du bain fondu est identifié. La confrontation des résultats obtenus numériquement et expérimentalement permet de mettre en place des relations entre les paramètres opératoires de soudage (I, h) et les paramètres numériques (P, R) conférant un caractère prédictif à la source de chaleur. Ce modèle de source a été validé pour différentes configurations de soudage en termes d’épaisseurs de tôles, de matériaux à assembler, de vitesses d’avance de la torche, ...Notre modèle thermique a ensuite servi de base pour la simulation thermomécanique du procédé. Le modèle est appliqué à l’assemblage de deux composants d’un turbomoteur en superalliage base Nickel. / Gas Tungsten Arc Welding (GTAW) is the most widely used welding process in aeronautics, due to its weld quality. During a welding operation, the thermal source induces thermal gradients causing strains and stresses that could affect assembly’s life duration. The aim of this study is to develop a numerical model of the welding process in order to get optimized process parameters.Before coupling thermal and mechanical phenomena, we must modelize heat transfers during welding. We propose a simplified heat source linked to the process parameters which enables to predict the main dimensions of the weld pool and the thermal evolution in the solid part. This source is defined by an homogeneous heat flux depending on a power P distributed in a R radius disk. These two parameters relate to process parameters, the arc height (h) and the current intensity I.Experiment tests was achieved to study the weld pool dimensions for both cases : incomplete penetration and full penetration weld. For each test, we identified the heat source parameters (P, R) which allow to obtain the experimental weld pool dimensions. The confrontation of numerical and experimental results enables to get links between the heat source parameters (P, R) and the welding parameters (I, h), producing a predictive heat source. The heat source reliability was verified taking into account several welding configurations with various superalloys sheet thickness, welding speed, materials.A coupled thermal-mechanical analysis, based on our thermal model, was applied to an industrial case: a nickel based superalloy components assembly of a gas turbine.

Un nouveau procédé de trigénération thermo-hydraulique fonctionnant à partir d'énergie thermique basse température (80 à 110 °C) a été étudié pour assurer les différents besoins du secteur résidentiel. Le terme "thermo-hydraulique" se réfère à l'utilisation d'un liquide incompressible qui permet de transférer le travail hydrauliquement entre différents composants ou sous-systèmes, permettant d'améliorer l'efficacité de la chaine de conversion énergétique. Un modèle quasi-statique a été développé pour évaluer les performances énergétiques des différentes variantes du procédé. Ces calculs ont permis de définir parmi un large choix, quels fluides de travail étaient les plus appropriés. Ces calculs ont été complétés par une étude quasi-dynamique et dynamique permettant un meilleur dimensionnement du procédé. Enfin, une étude de fonctionnement annuel a été réalisée à partir du modèle quasi-statique pour évaluer l'évolution des performances ainsi que sa production d'énergie sur une année complète de fonctionnement. Ces études montrent que le couple fluide R1234yf/R1233zd semble le plus approprié à un fonctionnement en climat méditerranéen. L'étude annuelle montre qu'en considérant les données climatiques de la ville de Perpignan, le procédé permet d'amplifier l'énergie solaire collectée d'un facteur de 1,32 en moyenne et permet d'atteindre un COP solaire de 0,24 en mode rafraichissement. Quand les besoins thermiques sont satisfaits, l'intégralité de l'énergie solaire captée est valorisée pour produire de l'électricité avec un rendement moyen annuel de 4,2%. / A new process based on thermal-hydraulic conversion actuated by low-grade thermal energy (80–110 °C) is investigated and aims at providing trigeneration energy features for the residential sector. "Thermo-hydraulic" term refers to a process involving an incompressible fluid used as an intermediate medium to transfer work hydraulically between different thermal operated components or sub-systems allowing to improve the efficiency of the energy conversion chain. A model, assuming steady-state operations, is developed to assess the energy performances of different variants of this thermo-hydraulic process as well as various pairs of working fluids. These calculations were completed by a quasi-dynamic and dynamic models allowing a better sizing of the process. Finally, an annual study was realized from the quasi-static model in order to estimate the evolution of the performances as well as its power production over a complete year of functioning. For instance, in the frame of a single-family home, located in the Mediterranean region, the working fluid pair (R1234yf/R1233zd) is investigated in detail in order to estimate the annual performances. For domestic houses, the process aims at amplifying the solar energy collected by a factor of 1.32 for heating purpose, provides a cold production with a solar COP of 0.24 and generates electricity from the remaining solar energy with an efficiency of 4.2%.

Stirling engines are promising candidates for applications where air breathing engines cannot be used. Self contained engines capable of operating independently of the environment are required to convert thermal energy into electric power, or to perform other necessary functions. These are ideally suited for power generation onboard spacecrafts with radioisotope heat source. These engines can power interplanetary missions to Mars and beyond. The problem of parametric analysis, sensitivity and numerical optimization of Stirling cycle engine is discussed and applied to a specific example of a 2kWe free piston Stirling engine. Stirling cycle simulation programs are generated with emphasis and adaptations peculiar to free piston design for space use. Design algorithms are generated in MatLab and optimization toolbox is used for the parametric analysis adopted in this thesis. A free piston beta Stirling engine with a linear alternator configuration has been studied for the interdependency and performance effects of various important operational parameters. The analysis has been carried out in order to optimize the primary parameters, weight vis a vis envelope (length and diameter) and stroke of the engine, to make it suitable for space use. The major cycle parameters considered are operating pressure, linear speed, dead space ratio and swept volume ratio, classified as secondary parameters. The whole analysis has been carried out at a cycle temperature ratio of 0.4 for a heat source temperature of 873 K, typical of a radioisotope heat source. The optimization is carried out for the defined design requirements viz. envelope of 50 × 50 cm , stroke of less than 10 cm, and heat source temperature of 873 K. The process of parametric optimization of the primary parameters viz engine envelope and stroke are carried out with respect to the secondary parameters. Iterations are carried out on the design programs in MatLab. The results indicate that the three primary parameters have a different set each, of the secondary parameter values when optimized to the design requirement. The fmincon solver of MatLab in the optimization tool box is selected in order to validate the optimization results. The solver is used to find a minimum of a constrained nonlinear multivariable function defining the primary parameters. The results obtained concur with the optimization results generated by the design algorithm. Further, the interdependency amongst the primary and secondary parameters is studied by generating MatLab plots for all possible combinations among the various parameters. The effect of variations in the pressure and linear speed on the system envelope and stroke are more pronounced at lower range values of the pressure and speed and the variations of the primary parameter values are constant at higher ranges. The effect of dead space ratio and swept volume ratio (>1.0) is not pronounced. The requirements in the environment of space place a number of constraints upon a Stirling engine/alternator design that are not present in terrestrial applications. High specific power is achieved by designing the engine for higher pressure and frequency operation than a terrestrial Stirling engine, and by using light weight materials where appropriate. Cylinder is the heart of the engine and it forms a major proportion of the total system mass. Mass and heat loss estimates and analysis have been carried out on the cylinder for various materials of construction. Based on the analysis feasibility exists for a Cu-Ni combination. The system would have a mass of 7kg with a specific power estimate of 0.28kW/kg and a conduction heat loss to mass ratio of 159W/kg. The system obtained by numerical analysis is modeled in system simulation software SIMULATIONX. The simulation of the system is studied and a sensitivity analysis performed in order to assess the parametric interdependency of the whole free piston Stirling engine system. The system sensitivity to piston and displacer mass is studied using the simulation model. Sensitivity results indicate that there is a range of mass values within which the system is operational, mass values outside the range makes the system non-functional. Also the range is a function of various parameters and detailed analysis is required in this direction in order to further optimize all the functional parameters. Engineering approximation is carried out using the curve fitting toolbox in MatLab to generate design equations in order to provide preliminary design data for the designer, further a scaling study is carried out at various power levels in order to assess the sensitivity of system geometry at various power levels.

This master’s thesis deals with influence of heat source on the value of the apartment building. The introduction describes the calculation of heat losses, types of heating systems, heating elements, heat sources for heating and hot water, methods of market valuation. Further are chosen two variants of heat sources for heating and domestic hot water for the Domino apartment building. Both heating elements are designed to cover the heat losses of the house. At the end of the thesis is an evaluation of the return of a more expensive variant, but cheaper to operate, profit from sale and profibility on rent of the apartment building.

This diploma thesis deals with the issue of heat pumps as devices using low-potential heat of the surrounding environment for heating of buildings. In the theoretical part of the thesis there are described various types of these devices, the sources of low-potential heat and the possibilities of heat energy accumulation. The practical part of the thesis is focused on processing and evaluation of operational data of air/water heat pump used for heating of family house and assessment of importance of accumulation tank in heating system. Part of the thesis is also a proposal of optimization of heat pump control.

The scope of this diploma thesis is feasibility study of enlargement the current energy source by new technological equipment designed for heat and electric energy production. Technological equipment is designed regarding to capital costs and minimum enviromental effects. In the thesis is described most important aspects for successful design new biomass energy source. The result can be used for investor´s decision making about determination toward investment.

This master’s thesis deals with the design of the ventilation and heating system in low-energy single family house. The thesis is divided into three parts. The first part of the thesis provides an overview of the project together with the requirements of the house owner. The options for heating and ventilation in low-energy buildings are also discussed in this part. The second part deals with the design of the ventilation system with heat recovery. The design includes determination of the amount of ventilation air, selection of a suitable ventilation unit and the design of the supply air and return air ductworks. The last part focuses on the heating system. It includes the calculations of the heat loss of the house and design of floor heating. Furthermore, the selection of heat source together with the safety measures is described in this part. Both design parts include the bills of materials, along with the budget and the drawings.

This thesis deals with the influence of building insulation to design of the heat source. The theoretical part describes the historici evolution of the construction, insulation origins and basic concepts associated with heat loss calculations. Introduction to the practical part describes possible wals of rating proposal and construction and technical description of the new residential building Cacovická. The main part deals with "Influence of thermal insulation on the building proposal heat" performed in two different variants. Finally work is a comparison of the two variants and evaluation of lower cost options.

The thesis deals with the calculation of the design heat load of a reconstructed family house and the design of both the space heating system and the balanced ventilation system for the house. The determination of the design heat load was performed according to ČSN EN 12831 technical standard. A low-temperature hydronic heating system was chosen for space heating of the house. The thesis describes the design of the system including calculations and the technical drawings. A heat source for the heating system was chosen with regard to the requirements of the investor. A mechanical ventilation system with heat recovery was proposed for house ventilation. The thesis contains the design of the ventilation system including calculations and the technical drawings.

The master's thesis is focused on heat pumps as a device using sources of a low-potential heat for building's heating. There are individual types of these devices characterized by a principle of operation and used media. Main focus of this thesis is a design of a compact air-water heat pump for the company PZP HEATING a.s. consisting of a cooling circulation’s design and individual components of this circulation. Finally there is a proposal of the heat pump’s case presented at the end of this work.