Em projetos de oleodutos e gasodutos utilizam-se aços de alta resistência e baixa liga (ARBL), como o aço API 5L X80. Na soldagem multipasse destas tubulações, a zona afetada pelo calor (ZAC) do passe de raiz é submetida a um novo ciclo térmico pelos passes de soldagem subsequentes. Isto resulta em alterações nos valores das propriedades físicas. Nos aços ARBL, a ZAC de grãos grosseiros reaquecida intercriticamente (IC-ZACGG) pode se tornar uma zona frágil localizada, isto é, uma zona com maior dureza. Consequentemente, falhas estruturais podem ocorrer, ocasionando paradas não desejadas no transporte de fluidos. O objetivo deste trabalho é desenvolver uma metodologia baseada no modelo de fontes de calor distribuídas de Mhyr e Gröng, para avaliar o fluxo de calor na soldagem considerando as propriedades físicas dependentes da temperatura. Estender a aplicação desta ferramenta em soldagens multipasses para identificar sub-regiões da ZAC de um passe anterior sendo afetada pela ZAC de passes subsequentes. As isotermas simuladas foram validadas através de medições realizadas em macrografias de juntas soldadas. Os ciclos térmicos simulados foram validados através das temperaturas máximas atingidas e pelos tempos de resfriamento de 800 a 500 ºC (?t8-5) dos ciclos térmicos experimentais. Ao aplicar a metodologia proposta, foi possível delimitar com acurácia as regiões reaquecidas da ZAC e analisar os efeitos dos passes subsequentes em cada uma das sub-regiões da ZAC do passe de raiz. A IC-ZACGG na região do passe de raiz foi localizada, mas não se comportou como zona frágil devido à boa soldabilidade do aço API 5L X80 comprovada pelos ensaios de dureza e de tenacidade ao impacto Charpy-V. / In pipelines projects, the high strength low alloy (HSLA) steels are used, such as the API 5L X80 steel. During the multipass welding of these pipes, the heat affected zone (HAZ) of the root pass is subjected to a new thermal cycle by the subsequent welding passes. This results in changes in the values of the physical properties. In the HSLA steels, the intercritical reheated coarse-grained heat-affected zone (IR-CGHAZ) can become a local brittle zone, that is, a region with greater hardness. Consequently, structural failures could happen, causing undesired shutdowns in fluid transportation. The objective of this work is to develop a methodology based on the distributed heat sources model of Mhyr and Gröng, to evaluate the heat flux in the welding considering the temperature-dependent physical properties. Extend the application of this tool in multipass welds to identify HAZ subregions of a previous pass being affected by the HAZ of subsequent passes. The simulated isotherms were validated through measurements made on macrographs of welded joints. The simulated thermal cycles were validated through the maximum temperatures reached and the cooling times from 800 °C to 500 ºC (?t8-5) of the experimental thermal cycles. By applying the proposed methodology, it was possible to accurately delimit reheated HAZ regions and analyze the effects of subsequent passes in each of the root pass HAZ subregions. The IRCGHAZ in the root pass region was localized, but it did not behave as a brittle zone due to the good weldability of the API 5L X80 steel as proven by the hardness and Charpy-V impact tests.

L'objectif de cette thèse est de mener une caractérisation expérimentale complète du comportement mécanique et thermomécanique d'un polyuréthane thermoplastique compact et sous forme moussée, utilisé dans la fabrication de pièces antivibratoires dans l'industrie automobile. Cette caractérisation est effectuée en s'appuyant sur des techniques d'imagerie quantitative, la thermographie infrarouge en particulier. D'un point de vue mécanique, la dépendance des différents phénomènes - effet Mullins, hystérésis mécanique, déformation résiduelle et variation de volume - à la densité initiale et à la vitesse de chargement a été établie. Sur le plan thermique et calorimétrique, la signature de ces différents phénomènes a été caractérisée et les bilans énergétiques menés ont permis d'estimer la dissipation mécanique en fonction des conditions d'essais et de la densité initiale du matériau. Les résultats de ces travaux constituent une base de données expérimentale pour l'identification de paramètres constitutifs et l'enrichissement de lois de comportement. / This PhD thesis deals with the full mechanical and thermomechanical characterization of thermoplastic polyurethane, in its compact and foam states, dedicated to antivibratory systems for automotive. This characterization has been carried out by using quantitative imaging techniques, especially infrared thermography. From a mechanical point of view, the dependency of the different phenomena involved in the material deformation - Mullins effect, mechanical hysteresis, residual deformation and volume change - on the initial density and loading rate has been established. The thermal and calorimetric signature of these phenomena has been characterized and the mechanical dissipation was estimated from energy balances. The results obtained provide an experimental database for the identification of constitutive parameters and the enrichment of behavior laws.

The diploma thesis is focused on district heat supply, heat sources, machinery and safety equipment of boiler rooms. The main goal of the thesis is to modernize parts of the heat sources with the respective boiler room equipment in accordance with the latest available technology. The generated thermal energy is used for heating or hot water production for residential and non-residential buildings in the vicinity of the boiler room. In the theoretical part, the thesis focuses in more detail on boiler rooms, specifically on heat energy sources, machinery and safety equipment of boiler rooms, system ventilation and combustion exhaust. The findings are applied in the design of the new boiler room layout. It is followed by a detailed description of the current state of the boiler room and heat networks. An essential part of the work is the assessment of layout of the current heat sources and the creation of a new design for the replacement of insufficient sources and related equipment. The last goal is an economic overview of the designed project solution.

The diploma thesis deals with the analysis of the cost of a house in the area of peripheral constructions and the effect of thermal insulation on energy consumption for heating and hot water. The theoretical part generally defines renewable energy sources, heat sources, thermal transmissions and structural losses, basics of valuation of construction works and supplies and overview of state subsidies. In the practical part are proposed composition of peripheral constructions, calculation of heat transfer coefficient of all designed perimeter structures and their subsequent evaluation. Furthermore, there is an estimated annual energy demand for heating and hot water and annual electricity consumption in the household. At the end of diploma thesis is a proposal of suitable energy sources and calculation of the return on investment in these sources.

Heat production together with electricity production stands for 31% of the global CO2 emissions. The production is as of today still highly dependent on fossil fuels, with a global district energy mix share of fossil fuels of 90%. To stay in line with the Paris Agreement, district heating must be configured away from fossil fuels by utilizing new emission free heat sources as well as creating higher energy efficient cities by incorporating more waste heat recovery. Helsinki has a District Heating (DH) dominated by fossil fuels and proclaimed goals of becoming carbon-­neutral by 2035, as of 2020 the annual heat demand in the city was 6.4TWh of heat. To do so, there is a need for research to investigate ways to include carbon-­free heat sources into the current heating system. There is currently a limited amount of literature available in this area and from the identified research gap the following main research question was developed. How can Helsinki achieve carbon-­free district heating? To easier answer the main research question, three three sub­questions were developed. (1) How large is the energy potential for non­-carbon based heat sources in Helsinki for district heating? (2) Where are the heat sources located? (3) What are the techno-­economic implications of the heat sources? A high resolution heat source mapping and spatial analysis was conducted for the city of Helsinki where low grade heat sources were to be identified for the purpose of district heating. The work focused on the following heat sources: Grocery Retail, Ice Rinks, Subway Stations, Data Centers, Wastewater, Sea Water Heat Pumps and Geothermal Energy. The developed model consists of five steps: (1) Heat source identification, (2) Technical potential evaluation, (3) DH-network mapping & Spatial analysis, (4) Economic model, and (5) Techno-­Economic evaluation. A total of 363 heat source points was identified and evaluated. The combined results of the heat sources were a total capacity of 1257.56 MW with a resulting total annual heat production of 7008.31 GWh. The majority of the capacity and heat was contributed from seawater heat pumps and geothermal heat pumps. Around 84% of the mapped heat sources were within 100 meters of the current district heating piping network. The economical findings show that a majority of the heat sources yield a positive net present value and a discounted payback period of below 11 years. The levelized cost of heat was within reasonable expectations when compared to existing data where Data centers showed the most promising result. The study can conclude that Helsinki can potentially achieve a non-­carbon­ based district heating system with a sufficient heat production management strategy. / Värme­- och elproduktionen står tillsammans för 31% av de globala koldioxidutsläppen. Produktionen är idag fortfarande starkt beroende av fossila bränslen med en global andel fossila bränslen i fjärrvärmeblandningen på 90%. För att hålla sig i linje med Parisavtalet måste fjärrvärmen konfigureras bort från fossila bränslen genom att utnyttja nya utsläppsfria värmekällor samt skapa mer energieffektiva städer genom att utnyttja mer återvinning av spillvärme. Helsingfors har en fjärrvärme som domineras av fossila bränslen och har utsatt mål om att bli koldioxidneutralt senast 2035, vid 2020 hade staden en årlig värmekonsumption på 6.4 TWh. För att uppnå detta behövs forskning för att undersöka hur man kan inkludera koldioxidfria värmekällor i det nuvarande värmesystemet. Det finns för närvarande bristfällig mängd litteratur på detta område och utifrån den identifierade forskningsluckan utvecklades följande huvudsakliga forskningsfråga. Hur kan Helsingfors uppnå koldioxidfri fjärrvärme? För att lättare kunna besvara huvudfrågan utvecklades tre underfrågor. (1) Hur stor är energipotentialen för icke kolbaserade värmekällori Helsingfors för fjärrvärme? (2) Var finns värmekällorna? (3) Vilka är de tekno-­ekonomiska konsekvenserna av värmekällorna? En högupplöst kartläggning av värmekällor och en rumslig analys genomfördes för Helsingfors stad där lågkvalitativa värmekällor skulle identifieras för fjärrvärme. Arbetet fokuserade på följande värmekällor: Livsmedelsbutiker, isbanor, tunnelbanestationer, datacenter, avloppsvatten, värmepumpar för havsvatten och geotermisk energi. Den utvecklade modellen består av fem steg: (1) Identifiering av värmekällor, (2) Utvärdering av teknisk potential, (3) Kartläggning av DH­-nätverk och rumslig analys, (4) Ekonomisk modell och (5) Teknisk-ekonomisk utvärdering. Totalt 363 värmekällor identifierades och utvärderades. De kombinerade resultaten av värmekällorna var en total kapacitet på 1,257.56 MW med en total årlig värmeproduktion på 7,088.31 GWh. Merparten av kapaciteten och värmen kom från havsvattenvärmepumpar och geotermisk värme. Cirka 84% av de kartlagda värmekällorna låg inom 100 meter från det nuvarande fjärrvärmerörnätet. De ekonomiska resultaten visar att majoriteten av värmekällorna gav ett positivt nettonuvärde och en diskonterad återbetalningstid på mindre än 11 år. Den standardiserade kostnaden för värme låg inom rimliga gränser när den jämförs med befintliga data, där datacenter visade det mest lovande resultatet. Givet studiens resultat kan slutsatsen erhållas att Helsingfors potentiellt kan uppnå ett fossilfritt fjärrvärmesystem med en tillräcklig produktions-­ och värmehanteringsstrategi för fjärrvärme.

An investigation into the performance of several combined gas-steam power generating plants’ cycles was undertaken at the School of Engineering and Technology at the University of Hertfordshire and it is predominantly analytical in nature. The investigation covered in principle the aspect of the fundamentals and the performance parameters of the following cycles: gas turbine, steam turbine, ammonia-water, partial oxidation and the absorption chiller. Complete thermal analysis of the individual cycles was undertaken initially. Subsequently, these were linked to generate a comprehensive computer model which was employed to predict the performance and characteristics of the optimized combination. The developed model was run using various input parameters to test the performance of the cycle’s combination with respect to the combined cycle’s efficiency, power output, specific fuel consumption and the temperature of the stack gases. In addition, the impact of the optimized cycles on the generation of CO2 and NOX was also investigated. This research goes over the thermal power stations of which most of the world electrical energy is currently generated by. Through which, to meet the increase in the electricity consumption and the environmental pollution associated with its production as well as the limitation of the natural hydrocarbon resources necessitated. By making use of the progressive increase of high temperature gases in recent decades, the advent of high temperature material and the use of large compression ratios and generating electricity from high temperature of gas turbine discharge, which is otherwise lost to the environment, a better electrical power is generated by such plant, which depends on a variety of influencing factors. This thesis deals with an investigation undertaken to optimize the performance of the combined Brayton-Rankine power cycles' performance. This work includes a comprehensive review of the previous work reported in the literature on the combined cycles is presented. An evaluation of the performance of combined cycle power plant and its enhancements is detailed to provide: A full understanding of the operational behaviour of the combined power plants, and demonstration of the relevance between power generations and environmental impact. A basic analytical model was constructed for the combined gas (Brayton) and the steam (Rankine) and used in a parametric study to reveal the optimization parameters, and its results were discussed. The role of the parameters of each cycle on the overall performance of the combined power cycle is revealed by assessing the effect of the operating parameters in each individual cycle on the performance of the CCPP. P impacts on the environment were assessed through changes in the fuel consumption and the temperature of stack gases. A comprehensive and detailed analytical model was created for the operation of hypothetical combined cycle power and power plant. Details of the operation of each component in the cycle was modelled and integrated in the overall all combined cycle/plant operation. The cycle/plant simulation and matching as well as the modelling results and their analysis were presented. Two advanced configurations of gas turbine cycle for the combined cycle power plants are selected, investigated, modelled and optimized as a part of combined cycle power plant. Both configurations work on fuel rich combustion, therefore, the combustor model for rich fuel atmosphere was established. Additionally, models were created for the other components of the turbine which work on the same gases. Another model was created for the components of two configurations of ammonia water mixture (kalina) cycle. As integrated to the combined cycle power plant, the optimization strategy considered for these configurations is for them to be powered by the exhaust gases from either the gas turbine or the gases leaving the Rankine boiler (HRSG). This included ChGT regarding its performance and its environmental characteristics. The previously considered combined configuration is integrated by as single and double effect configurations of an ammonia water absorption cooling system (AWACS) for compressor inlet air cooling. Both were investigated and designed for optimizing the triple combination power cycle described above. During this research, tens of functions were constructed using VBA to look up tables linked to either estimating fluids' thermodynamic properties, or to determine a number of parameters regarding the performance of several components. New and very interesting results were obtained, which show the impact of the input parameters of the individual cycles on the performance parameters of a certain combined plant’s cycle. The optimized parameters are of a great practical influence on the application and running condition of the real combined plants. Such influence manifested itself in higher rate of heat recovery, higher combined plant thermal efficiency from those of the individual plants, less harmful emission, better fuel economy and higher power output. Lastly, it could be claimed that various concluding remarks drawn from the current study could help to improve the understanding of the behaviour of the combined cycle and help power plant designers to reduce the time, effort and cost of prototyping.

This study is part of an original approach based on quantitative imaging techniques, such as Infrared Thermography, to study the damage under fretting loadings. The main objective was the establishment of new experimental method for a rapid determination of crack initiation conditions under fretting loadings, based on the analysis of the thermal signal. One other objective was the determination of the different heat sources in order to assess a local analysis of the fretting damage. This work underlined the great potential of Infrared Thermography to study this damage. / Cette étude s'inscrit dans une approche originale basée sur des techniques d'imagerie quantitatives comme la thermographie infrarouge pour étudier l'endommagement sous chargement de fretting. Le premier objectif était de développer une méthode de construction rapide de carte de fretting basée sur l'analyse du signale thermique au cours d'essais de fretting. Un deuxième objectif était de déterminer les sources de chaleurs accompagnant le fretting pour une meilleure compréhension des mécanismes d'endommagement. Ce travail a souligné le grand potentiel de la thermographie infrarouge pour l'étude de c'est phénomènes.

Les alliages à mémoire de forme Nickel Titane sont des matériaux aux propriétés remarquablesdues à une transformation martensitique réversible et sont largement utiliséspar l’industrie biomédicale et dans des dispositifs de type actionneurs. La première partiede cette étude porte sur une analyse de leur comportement thermomécanique basée surla réalisation de mesures de champs cinématiques (par corrélation d’images visibles) etthermiques (par caméra infrarouge). Une part importante du travail présenté concernel’amélioration des calculs de sources de chaleur à partir des champs de température. Pource faire, les capacités et conductivités thermiques des phases austénitique et martensitiqueont été estimées par différentes méthodes expérimentales. Ensuite, la méthode de calcul desource a été validée sur des données virtuelles obtenues numériquement et sur des donnéesexpérimentales obtenues lors d’une transformation martensitique induite par un refroidissementnaturel. Cette première partie se conclut par l’application des développements àdes mesures réalisées lors d’un essai de cisaillement. La seconde partie est une contributionà la réalisation de matériaux architecturés constitués d’empilement de tubes de NiTi liésentre eux ; notre étude concerne la réalisation et la caractérisation de liaisons de tubes deNiTi par soudage résistif. / NiTi shape memory alloys have amazing properties due to a reversible martensitictransformation and are widely used by biomedical industries and as actuators. The firstpart of this study deals is a thermomechanical analysis of the material, based on kinematical(with digital image correlation) and thermal (with infrared camera) field measurements.An important part of this work deals with the improvement of the heat sources estimationfrom thermal fields. For this, thermal heat capacities and conductivities of austeniteand martensite were estimated with several experimental methods. Then, the heat sourceestimation method was validated from virtual data obtained numerically and from experimentaldata obtained during a martensitic transformation induced by natural cooling.This first part is concluded with the use of this technique to study shear tests. The secondpart of this study is a contribution to the realization of architectured materials composedof linked stacked tubes. Our study deals with the realization and the characterization ofthe NiTi link, realized by resistance welding.

Les travaux présentés dans cette thèse concernent l'étude thermique des batteries Li-ion en vue d'une application de gestion thermique pour l'automobile. La compréhension des phénomènes thermiques à l'échelle accumulateur est indispensable avant de réaliser une approche de type module ou pack batterie. Ces phénomènes thermiques sont mis en évidence à partir d'une modélisation thermique globale de deux accumulateurs de différentes chimies, en décharge à courant constant. La complexité du caractère résistif de l'accumulateur Li-ion a mené au développement d'un modèle prenant en compte l'interaction entre les phénomènes électrochimiques et thermiques, permettant une approche prédictive de son comportement. Enfin la réalisation de deux boucles expérimentales, de simulation de systèmes de gestion thermique d'un module de batterie, montre les limites d'un refroidissement classique par air à respecter les critères de management thermique. En comparaison, le second système basé sur l'intégration innovante d'un matériau à changement de phase (MCP) se montre performant lors de situations usuelles, de défauts ou encore lors du besoin d'une charge rapide de la batterie. / This work relates to the thermal study of Li-ion batteries in order to develop an optimized battery thermal management system. The understanding of thermal phenomena at cell scale is essential before to undertake an approach of the battery module or pack. Galvanostatic discharges of two kind of Li ion cells are modeled to highlight thermal phenomena. The complexity of the resistive behavior of Li-ion cell led to the development of an electrochemical-thermal coupled model to get a predictive approach. Then, two experimental tests benches were designed so as to compare two battery thermal management systems (BTMS). Restrictions of air cooling highlight its disability to achieve thermal management criteria. Innovative integration of a phase change material (PCM) was then tested under several uses of the battery module. This new BTMS showed really promising performances during intensive driving cycles, failure tests, and when a fast charge is needed.

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