Exergy utilization calculations have been in the past repeatedly used to quantify the quality and quantity of energy used in thermal energy processes. This thesis is an attempt to derive a common language exergy utilization and compare for the first time two entirely different manufacturing processes, namely material processing by a mechanical method of straining of the material and simple heating of the same mass of the material using exergy utilization as a metric. The exergy utilization of material processing is determined by performed work and utilized heat transfer using 1) Ramberg-Osgood equation and 2) Lumped heat capacitance method. A comparison of these two methods is presented.

Global warming is an unequivocal fact proved by the persistent rise of the average temperature of the earth. IPCC reported that scientists were more than 90 % certain that most of the global warming was caused by increasing concentrations of greenhouse gases (GHG) produced by human activities. One alternative to combat the GHG is to explore technologies for utilizing CO2 already generated by current energy systems and develop methods to convert CO2 into useful combustible gases. Two-step conversion of CO2 with catalysts is one of the most promising methods. Ceria (CeO2) is chosen as the main catalyst for this conversion in the thesis. It releases O2 when it is reduced in a heating process, and then absorbs O2 from CO2 to produce CO when it is re-oxidized in a cooling process. To make the conversion economic, solar power is employed to drive the conversion system. In this thesis, a flexible system with fluidized bed reactors (FBRs) is introduced. The thermogravimetric analysis (TGA) was carried out to examine the performance of ceria during its reduction and oxidation. Subsequently, the exergy analysis was used to evaluate the system’s capability on exporting work. The theoretical fuel to chemical efficiency varied from 4.85 % to 43.2 % for CO2 conversions. To investigate the operation mechanism of the system, a mathematical model was built up for the dynamic simulation of the system. Variables such as temperatures and efficiencies were calculated and recorded for different cases. The optimum working condition was found out to be at 1300 ⁰C for the commercial type of ceria. Finally, an experimental system was set up. The hydrodynamics and heat transfer in the fluidized bed reactor were studied. A CFD model was built up and validated with the experimental trials around 120 ⁰C. The model was then used as a reliable tool for the optimization of the reactor. The entire work in the thesis follows the procedure of developing an engineering system. It forms a solid basis for further improvements of the system to recycle CO2. / <p>QC 20141006</p>

Cities interact with and rely on energy in complex ways. Fundamentally cities rely upon high quality energy and outputs of low quality for their very existence. The energy flows and transformations enabling cities are tied to physical limits imposed by thermodynamics. Understanding of these limits and the relationships among energy and cities, it is revealed herein, is of vital importance to the sustainability of cities. Four contributions to this understanding are provided. The first articulates how the thermodynamic forces driving cities, together with the dynamic environment within which cities reside, stipulates what type of activities within cities are sustainable. Second, a model depicting the scaling relationship between urban energy use and economic output is devised, and it’s fit to historical data demonstrated via nonlinear regression. By differentiating between energy used to grow and energy used to maintain economic output the model illustrates how reductions in these values on a per dollar basis abets growth while the reverse delays growth, or stops it altogether when energy needs for maintenance become too high. Third, an exergy network conceptualization of cities is developed that reveals the structure of the exergy flows in a city. The topology of the network drastically alters the city’s ability to maximize usefulness of imported energy as well as alter that variability in the amount of usefulness extracted. Finally, the resilience of cities with respect to energy is presented by considering the energy storage and buffer capacity of the urban metabolism. The city of Toronto is shown to have adequate flexibility in food and transport fuels to withstand operation for days without undue interruption of typical activities. Together these differing aspects of the open non-equilibrium details of cities establish an improved prescription of the sustainable city.

Cities interact with and rely on energy in complex ways. Fundamentally cities rely upon high quality energy and outputs of low quality for their very existence. The energy flows and transformations enabling cities are tied to physical limits imposed by thermodynamics. Understanding of these limits and the relationships among energy and cities, it is revealed herein, is of vital importance to the sustainability of cities. Four contributions to this understanding are provided. The first articulates how the thermodynamic forces driving cities, together with the dynamic environment within which cities reside, stipulates what type of activities within cities are sustainable. Second, a model depicting the scaling relationship between urban energy use and economic output is devised, and it’s fit to historical data demonstrated via nonlinear regression. By differentiating between energy used to grow and energy used to maintain economic output the model illustrates how reductions in these values on a per dollar basis abets growth while the reverse delays growth, or stops it altogether when energy needs for maintenance become too high. Third, an exergy network conceptualization of cities is developed that reveals the structure of the exergy flows in a city. The topology of the network drastically alters the city’s ability to maximize usefulness of imported energy as well as alter that variability in the amount of usefulness extracted. Finally, the resilience of cities with respect to energy is presented by considering the energy storage and buffer capacity of the urban metabolism. The city of Toronto is shown to have adequate flexibility in food and transport fuels to withstand operation for days without undue interruption of typical activities. Together these differing aspects of the open non-equilibrium details of cities establish an improved prescription of the sustainable city.

Solar assisted single-stage absorption heat pump (AHP) was used to supply energy to a floor-heating system by using the exergy methods. An existing duplex-house,in Ankara, with a heating load of 25.5 kW was analysed. Heating loads of the spaces in the building were calculated and a floor heating panel was modelled for each space leading to the capacity of the AHP before it was designed. Solar energy was delivered to the evaporator and high temperature heat input delivered to the genarator are met by auxiliary units operating with natural gas.The solar energy gained by flat-plate collectors was circulated through AHP.The anaysis performed according to the storage tank temperature reference value if the water temperature leaving the storage tank exceeds a predetermined value it is directly circulated through the floor heating system. Exergue analysis were carried out with Mathcad program. Exergy analysis showed that irreversibility have an impact on absorption system performance.This study indicated which components in the system need to be improved thermally.A design procedure has been applied to a water-lithium-bromide absorption heat pump cycle and an optimisation procedure that consists of determinig the enthalpy, entropy ,exergy, temperature, mass flow rate in each component and coeficient of performance and exergetic coefficient of performance has been performed and tabulated.

In this thesis, several configurations of combined cycle cogeneration systems proposed by the author and an existing system, the Bilkent Combined Cycle Cogeneration Plant, are investigated by energy, exergy and thermoeconomic analyses. In each of these configurations, varying steam demand is considered rather than fixed steam demand. Basic thermodynamic properties of the systems are determined by energy analysis utilizing main operation conditions. Exergy destructions within the system and exergy losses to environment are investigated to determine thermodynamic inefficiencies in the system and to assist in guiding future improvements in the plant. Among the different approaches for thermoeconomic analysis in literature, SPECO method is applied. Since the systems have more than one product (process steam and electrical power), systems are divided into several subsystems and cost balances are applied together with the auxiliary equations. Hence, cost of each product is calculated. Comparison of the configurations in terms of performance assessment parameters and costs per unit of exergy are also given in this thesis.

Este trabalho contém um estudo experimental para a obtenção e a validação de um combustível à base de água, obtido através da eletrolise desta e denominado de HHO (Gás de Brown), a ser utilizado como auxiliar na queima de hidrocarbonetos dos demais combustíveis fósseis e de fontes renováveis como o álcool hidratado (etanol). Para a realização deste trabalho foi utilizado um eletrolisador composto por placas de aço inox 316L e eletrólito à base de hidróxido de potássio, conjunto este de eletrólito em sua concentração ideal, material de construção do eletrolisador determinado através de estudo prévio em bibliografia. Posto o sistema em funcionamento, realizado a análise exergética da composição e do gás gerado, onde se verificou a existência de energia disponível para gerar trabalho útil e que o maior desperdício se encontrava na potência elétrica utilizada para a produção do gás. Após esta validação o gás foi submetido a testes em dinamômetro de desempenho e emissões com motores de combustão interna com deslocamento de 1,6 litros, porém com configurações diferentes de alimentação. Para que os dados refletissem a utilização de maior demanda de combustível, como no trânsito urbano, foram escolhidas as rotações de 1500rpm, 2500rpm e 3500rpm, com aberturas de borboleta em dois estágios, total 100% e abertura parcial a 40%. As variáveis controladas foram a potência, o torque, o consumo instantâneo de combustível, o fator lambda (λ) e a emissão dos gases CO, CO2 e HC. Em ambos os testes, aberturas total e parcial, com suas respectivas particularidades de no sistema de alimentação, foram apresentadas tendências de melhora em desempenho e reduções de emissões, devido aos valores obtidos estarem dentro das incertezas de medição no caso do sistema de alimentação por carburador e combustível principal o álcool hidratado, contudo no caso do sistema de alimentação por injeção eletrônica programável à gasolina comercial, com injeção de gás individualizada os resultados apresentados ficaram moderadamente acima das incertezas de medição. Entretanto, o sistema utilizado no experimento com gasolina + HHO e injeção programável, apresentou uma redução de emissões de CO em 26,4% (abertura parcial) e 18,6% (abertura total), reduzindo as emissões de HC em 16% (abertura parcial) e 14,5% (abertura total) e, por sua vez, o consumo de combustível reduziu em 29,6%. / This work contains an experimental study to obtain and validate a water-based fuel obtained through the electrolysis of this one and denominated HHO (Brown Gas), to be used as an auxiliary in the hydrocarbon burning of other fossil fuels and renewable sources such as hydrated alcohol (ethanol). For this work, an electrolyzer composed of 316L stainless steel plates and electrolyte based on potassium hydroxide was used, this electrolyte assembly in its ideal concentration, electrolyte construction material determined through a previous bibliography study. After the system was in operation, the exergy analysis of the composition and generated gas was performed, where the existence of available energy to generate useful work was verified and that the greatest waste was in the electric power used for the production. After this validation the gas was submitted to dynamometer tests of performance and emissions with engines of internal combustion with displacement of 1.6 liters, but with different feeding configurations. For the data to reflect the use of higher fuel demand, such as in urban traffic, the revolutions of 1500rpm, 2500rpm and 3500rpm were chosen, with twostage butterfly apertures, total 100% and partial opening at 40%. The variables controlled were power, torque, instantaneous fuel consumption, lambda factor (λ) and emission of CO, CO2 and HC gases. In both tests, total and partial openings, with their respective peculiarities of the feed system, presented trends of improvement in performance and emission reductions, due to the values obtained being within the uncertainties of measurement in the case of the carburetor feed system and the main fuel is the hydrated alcohol, however in the case of the commercial gasoline programmable electronic fuel injection system with individualized gas injection the presented results were moderately above the measurement uncertainties. However, the system used in the experiment with gasoline + HHO and programmable injection showed a reduction of CO emissions by 26.4% (partial opening) and 18.6% (total opening), reducing HC emissions by 16% ( partial opening) and 14.5% (total opening) and, in turn, fuel consumption decreased by 29.6%.

Le développement scientifique actuel contribue à assurer le confort dans les bâtiments grâce à une grande variété de technologies. Une utilisation rationnelle des ressources énergétiques a un effet bénéfique sur l'économie et la protection de l'environnement. En ce qui concerne l'utilisation de la trigénération, elle devient de plus en plus répandue. La thèse porte sur l'analyse et l'optimisation de schemas hybrides d'alimentation des espaces habitables avec de l’énergie thermique. Pour une analyse cohérente il est nécessaire d'utiliser un outil qui peut égaliser les différents types d'énergie dans le système: chimique, électrique, thermique. L'étude basée sur l'analyse exergétique met en évidence les pertes d'énergie utilisable et les opportunitées de recuperation de l'energie, tout en offrant la possibilité de prendre des décisions fonctionnelles et structurelles pour accroître l'efficacité du système. Les objectifs de cette thèse sont : l'élaboration de différents schémas pour produire simultanément de l’électricité, du froid et de l’eau chaude sanitaire; l’étude et l’optimisation des machines frigorifiques à absorption et à éjection en utilisant l’approche exergétique; l’étude d'un moteur turbo diesel suralimenté; l’étude et l’optimisation du système moteur – machine à froid en utilisant l’analyse exergétique. Deux études de cas ont été développées : bilan thermique d'un bâtiment à rafraîchir, qui a permis d’estimer la puissance frigorifique à installer et bilan global d’un système de cogénération – électricité plus chauffage urbain. / The current scientific development help ensure the comfort in buildings with a large variety of technologies. Rational use of energy resources has a positive effect on the economy and protecting the environment. Concerning the trigeneration, it is becoming more and more widespread. This PhD focuses on the analysis and optimization of hybrid schemes of production and distribution of heat for buildings. For a coherent analysis it is necessary to use a tool that can equalize the different types of energy in the system: chemical, electrical, thermal. The study based on exergy analysis highlights the energy losses and opportunities for the recovery of energy, and provide ability to take functional and structural decisions to increase efficiency.In this thesis, several aspects were examined: the development of a scheme to supply several utilities: electricity, cold and hot water; the study and optimization of absorption and ejection refrigerating machines using exergy analysis; the study of a supercharged turbo diesel engine, the study and optimization of the engine – refrigerating machine system, using exergy analysis.Two case studies were performed: the energy balance of a building, which was used to estimate the cooling capacity to install and the overall performance of a cogeneration - district heating system.

Ce travail de thèse apporte une contribution à l’utilisation de grandeurs thermodynamiques ainsi que géométriques en mécanique. La première partie de ce manuscrit est consacrée à l’étude de la fatigue oligocyclique, et de l’entropie de rupture en fatigue. Des entropies de rupture en fatigue sont estimées expérimentalement par diverses relations et sont comparées aux modèles empiriques utilisés dans la littérature. Il apparait que ces diverses entropies de rupture sont très proches ce qui permet de conclure qu'il existe une entropie de rupture constante liée uniquement au matériau. Pour les modèles empiriques, une extension du modèle de Ramberg-Osgood cyclique prenant en compte la variation temporelle de la contrainte est proposée et une étude sur l'imprécision du modèle de Park et Nelson est réalisée. Puis, une étude des différentes phases durant le test de fatigue est effectuée à travers l’étude de l’endommagement lié à l’entropie accumulée par le matériau. Une extension par l’utilisation du concept d’exergie permet la mise en évidence d’une nouvelle quantité, une exergie associée au travail de déformation plastique faisant intervenir une notion de qualité de la déformation plastique. Dans une deuxième partie, la diffusion de l’entropie d’échelle est étudiée et permet de créer divers comportements dépendants d’échelle. Elle permet d’étudier la log-périodicité d’un fractal déterministe fini (ou préfractal) ou de vérifier la construction de géométries déterministes finies dépendantes d’échelle. Une application de ces modèles dépendants d’échelle est effectuée dans le cadre de la détermination de propriétés mécaniques, pour l’analyse de faciès de rupture et pour la fragmentation. Finalement un lien possible entre comportement mécanique, géométrie et théorie constructale est présenté. / This Phd thesis is a contribution to the use of thermodynamics and geometry in mechanics. The first part of this manuscript is devoted to the study of low cycle fatigue and the notion of fracture fatigue entropy. Fracture fatigue entropies are experimentally estimated by various equations and compared to empirical models used in the litterature. It appears that these diverse fracture fatigue entropies are very close and allows to conclude that a constant fracture fatigue entropy exists only depending on the material. For the empirical models, an extension of the Ramberg-Osgood model is proposed taking into account the temporal variation of the loading, and, a study on the inaccuracy of the Park and Nelson model is realized. Then, a study on the different phases occurring in a fatigue test is done through the study of a damage parameter based on the entropy accumulated by the material. An extension using the concept of exergy allows the highlight of a new quantity, an exergy associated with plastic strain involving a quality factor. In a second part, the diffusion of scale-entropy is studied and permits to create various scale-dependent behaviors. It allows the study of log-periodicity of a finite deterministic fractal (or prefractal), or the verification of finite deterministic scale-dependent geometries. An application of these scale-dependent models is performed within the framework of the determination of mechanical properties, for the analysis of fractured surfaces and for fragmentation. Finally, a possible link between mechanical behavior, geometry and constructal theory is presented.

Submitted by MARCELO RAMSDORF (marceloramsdorf@gmail.com) on 2016-04-07T18:09:06Z No. of bitstreams: 1 Dissertacao_Marcelo_Ramsdorf.pdf: 3773711 bytes, checksum: 2740d7feeceb5938048e38e5ea25595e (MD5) / Approved for entry into archive by Felipe Augusto Arakaki (arakaki@reitoria.unesp.br) on 2016-04-08T11:53:43Z (GMT) No. of bitstreams: 1 ramsdorf_ma_me_guara.pdf: 3773711 bytes, checksum: 2740d7feeceb5938048e38e5ea25595e (MD5) / Made available in DSpace on 2016-04-08T11:53:43Z (GMT). No. of bitstreams: 1 ramsdorf_ma_me_guara.pdf: 3773711 bytes, checksum: 2740d7feeceb5938048e38e5ea25595e (MD5) Previous issue date: 2016-02-26 / Não recebi financiamento / O uso de células combustível de baixa temperatura embarcadas em aeronaves pode favorecer a geração de energia elétrica sem maiores impactos ambientais. Se, por um lado, o projeto de aeronaves atuais requer o uso de sistemas dedicados, por outro há uma maior demanda de energia elétrica a bordo. Isto significa que a pressurização da cabine, o sistema anti-gelo e a hidráulica da aeronave não devem depender da extração de ar do compressor das turbinas ou da potência de eixo. Entretanto, células combustível a hidrogênio apresentam dificuldades aos projetistas devido aos tanques de armazenamento, componentes em alta pressão e altas temperaturas para a reforma. Neste contexto, as células-combustível a etanol direto são uma tecnologia promissora. Publicações recentes mostram que, devido à baixa eficiência, células a etanol líquido em eletrólitos de membrana polimérica produzem calor residual. Conforme o Diagrama de Sankey obtido neste trabalho, 68% da energia total do combustível é convertida em calor, que deve ser gerenciado para evitar o ressecamento da membrana e o colapso do sistema. No presente trabalho um arranjo teórico de células a etanol direto é estudado. A metodologia leva em conta as demandas de energia de uma aeronave a jato de transporte regional em cada etapa do voo (táxi, decolagem, cruzeiro, descida e pouso). O trabalho apresenta uma contribuição inédita pela análise exergética do arranjo, que fornece um bom critério para a melhor escolha entre um sistema de cogeração ou recuperação de calor a bordo. Em um sistema otimizado, o calor residual pode ser utilizado no aquecimento de cabine ou aquecimento do combustível da aeronave. São apresentadas algumas estimativas de capacidade de aquecimento do combustível e da produção de água aquecida. A metodologia pode auxiliar o projetista a escolher entre duas configurações possíveis (com recuperação de calor no aquecimento de cabine ou puramente elétrico) dependendo da missão proposta para a aeronave. / The use of low temperature fuel cell stacks onboard aircrafts may provide a good way to generate electricity with less environment impact. Nowadays, the design of jet aircrafts requires embedded systems, which demand more electric power. This means that cabin air pressure, anti-icing and hydraulics should not depend on the engine bleed air or shaft power. However, hydrogen fuel cells pose difficulties for aircraft designers due to the storage tanks, high pressure systems and high temperatures for reforming. In this context, direct ethanol polimeric fuel cells are a promising technology. Recent publications show that the low efficiency of liquid ethanol in polymeric electrolyte produces waste heat. According to the Sankey Diagram obtained, 68% of the total input energy is heat that must be managed to avoid electrolyte drying and system collapse. In this article, a theoretical direct ethanol fuel cell stack is studied. The methodology takes into account the energy demands of a regional jet for each flight regime (start up, taxi, take off, cruise, descend and landing). It provides an unprecedented exergetic analysis that points out a good hint to choose between cogeneration or heat recovery onboard aircraft. The waste heat may be recovered for cabin and aircraft fuel heating in an optimized system. Some predictions for aircraft fuel heating capacity and water production are also presented. The methodology may help designers to decide which configuration is more appropriate (whether use heat recovery for cabin heating or a pure electric fuel cell stack) for the aircraft mission sought.