Dissertations / Theses on the topic 'THERMODYNAMICS PERFORMANCE'

Modifications to the quasistatic Carnot cycle are developed in order to formulate improved theoretical bounds on the thermal efficiency of certain refrigeration cycles that produce finite cooling power. The modified refrigeration cycle is based on the idealized endoreversible finite time cycle. Two of the four cycle branches are reversible adiabats, and the other two are the high and low temperature branches along which finite heat fluxes couple the refrigeration cycle with external heat reservoirs. This finite time model has been used to obtain the following results: First, the performance of a finite time Carnot refrigeration cycle (FTCRC) is examined. In the special case of equal heat transfer coefficients along heat transfer branches, it is found that by optimizing the FTCRC to maximize thermal efficiency and then evaluating the efficiency at peak cooling power, a new bound on the thermal efficiency of certain refrigeration cycles is given by $\epsilon\sb{m} = (\tilde\tau\sp2\sb{m}\ (T\sb{H}/T\sb{L}) - 1)\sp{-1},$ where $T\sb{H}$ and $T\sb{L}$ are the absolute high and low temperatures of the heat reservoirs, respectively, and $\tilde\tau\sb{m}=\sqrt{2}$ + 1 $\simeq$ 2.41 is the dimensionless cycle period at maximum cooling power. Second, a finite time refrigeration cycle (FTRC) is optimized to obtain four distinct optimal cycling modes that maximize efficiency and cooling power, and minimize power consumption and irreversible entropy production. It is found that to first order in cycling frequency and in the special symmetric case, the maximum efficiency and minimum irreversible entropy production modes are equally efficient. Additionally, simple analytic expressions are obtained for efficiencies at maximum cooling power within each optimal mode. Under certain limiting conditions the bounding efficiency at maximum cooling power shown above is obtained. Third, the problem of imperfect heat switches linking the working fluid of an FTRC to external heat reservoirs is studied. The maximum efficiency cycling mode is obtained by numerically optimizing the FTRC. Two distinct optimum cycling conditions exist: (1) operation at the global maximum in efficiency, and (2) operation at the frequency of maximum cooling power. The efficiency evaluated at maximum cooling power, and the global maximum efficiency may provide improved bench-mark bounds on thermal efficiencies of certain real irreversible refrigeration cycles.

In this thesis, applicable data from research on IC engines have been adapted to PACE engine designs. Data from studies on heat transfer, friction, and pressure losses, in particular, have been used. Certain parameters which define operation and design characteristics appear to influence PACE engine performance very strongly. Some of the more critical parameters, notably friction and heat transfer coefficients, must be determined experimentally if accurate model results are to be expected. Pressure ratio, compressor RPM, and maximum combustor temperature, the independent operating parameters, also have a dramatic effect on engine performance. Other design or operating characteristics and working fluid properties are not controlled independently. These are dictated by the engine physical design configuration and operation, ambient conditions, and choice of fuel.

An experimental effort has been completed in which water injection was investigated as a means of enabling increases in engine output and high load efficiency. Water was injected into the intake port of a direct fuel injected, 4-cylinder, boosted engine with dual independent variable valve timing. The water was shown to increase volumetric efficiency and decrease the onset of knock which in turn enable more optimal combustion phasing. Both of these affects resulted increases in load of up to 5.5% at the same manifold pressure as the baseline case. The advancement of combustion phasing, combined with elimination of fuel enrichment resulted in an increase in full load thermal efficiency of up to 35%. Analysis is provided around these affects, as well as the phase transformation of water throughout the engine cycle.

Thesis (M.S. in Physics)--Naval Postgraduate School, June 1990.
Thesis Advisor(s): Atchley, A.A. Second Reader: Hofler, T.J. "June 1990." Description based on signature page. DTIC Identifiers: Thermoacoustics, sound generators. Author(s) subject terms: Thermoacoustics. Includes bibliographical references (p. 51). Also available in print.

Advances in piston engine technology, coupled with high costs of turbine engines have led many general aviation manufacturers to explore the use of piston engines in their smaller vehicles. However, very few engine models are available to analyze piston engine performance. Consequently, designers using vehicle synthesis programs are unable to accurately predict vehicle performance when piston engines are used. This thesis documents the development of a comprehensive, thermodynamics based performance model that meets that need. The first part of this thesis details the basics of piston engine operation, including component geometry and the four stroke engine cycle. Next, the author analyzes the critical components of engine performance, including engine work and power. In developing the engine performance model the Ideal Engine Cycles are discussed. The cold air and fuel-air working fluid models are discussed, along with the types of combustion models, including the Otto Cycle, Diesel Cycle, and the Dual Cycle. Two performance models are generated using the Constant Volume Ideal Engine Cycle: an Ideal Gas Standard Cycle, and a Fuel-Air Cycle. The Ideal Gas Standard Cycle is useful for parametric analysis but lacks the accuracy required for performance calculations. The Fuel-Air Cycle, however, more accurately models the engine cycle and is selected as the basis for the computer program. In developing the computer program the thermodynamic charts used in the Fuel-Air Cycle calculations must be reproduced. To accomplish this, the NASA Chemical Equilibrium Application (CEA) program is integrated into a parent VBA based computer code to provide thermodynamic state point data. Finally, the computer program is correlated to the performance of an existing aviation engine to validate the model.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 2003.
Thesis supervisor: Neil E. Todreas. Includes bibliographical references (p. 117-121). Also available online.

Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, December 1990.
Thesis Advisor(s): Marto, Paul J. ; Memory, Steve. "December 1990." Description based on title screen as viewed on March 30, 2010. DTIC Identifier(s): Pool Boiling. Author(s) subject terms: Heat Transfer, Pool Boiling. Includes bibliographical references (p. 102-104). Also available in print.

There have been several attempts to establish efficient methods to convert the energy of marine waves into electrical power. Wells turbine, with an Oscillating Water Column (OWC), is one of such methods. Wells turbine is the most common type of self-rectifying air turbine employed by OWC wave energy devices due to its technical simplicity, reliability, and design robustness. Because Wells turbine is subject to early stall, which negatively limits its performance, there were many endeavours to improve the energy extraction performance of Wells turbine within the stall regime. However,those endeavours were based only on the first law of thermodynamics analysis, without relying on the second law analysis. Since the second law of thermodynamics is concerned with the generation rate of entropy and accordingly the useful work, it is important to take the entropy generation rate into account while improve the performance of Wells turbine. The main objective of this thesis is to analyse and improve the performance of Wells turbine under sinusoidal wave based on the entropy generation minimization method for various passive flow control technique parameters. To achieve this purpose, two-dimensional numerical models for Wells turbine aerofoils under sinusoidal wave flow conditions were built and used to investigate the single and multi-slots as passive flow control means. Different operating conditions with various design parameters were investigated. Furthermore, the turbine blade with optimum slots number, location and angle were investigated using the oscillating water system based on the real data from the northern coast of Egypt. Firstly, in addition to the commonly used first law analysis, the present study utilized an entropy generation minimization method to examine the impact of the flow control method on the entropy generation characteristics around the turbine blade. The obtained results indicate that the global entropy generation rate has a different value according to the aerofoil design. It was determined that a certain aerofoil geometry always gives a global entropy generation rate less than that of other aerofoil geometries under sinusoidal inlet velocity. Furthermore, the angle of attack radically affects the second law efficiency. Subsequently, a comprehensive investigation was carried out on the passive flow control effect on the entropy generation as well as the torque coefficient. It was found that with the use of passive flow control, the entropy generation around the aerofoil section increases. On the other hand, torque coefficient of aerofoil increases before the stall happens and continues to increase within the stall regime. A significantly delayed stall is also observed with the use of the passive flow control. Moreover, aerofoils with two,three and four slots were investigated to improve the performance of Wells turbine in the stall regime. The optimum slots number and locations were determined based on minimizing the global entropy generation rate in addition to increasing the torque coefficient. Furthermore, the optimum angle for single slot aerofoil was confirmed to provide a lower global entropy generation rate as well as a higher torque coefficient than the zero angle slot before and after the stall. Finally, from the modelling results, it can be concluded that the operating conditions based on real data for the northern coast of Egypt are very suitable for the oscillating water column system with Wells turbine as a wave energy converter. Moreover, by adopting the optimum slots number, location, and angle, the performance of Wellsturbine can be significantly improved for a wide range of operating conditions.

In this article a Novikov engine with fluctuating hot heat bath temperature is presented. Based on this model, the performance measure maximum expected power as well as the corresponding efficiency and entropy production rate is investigated for four different stationary distributions: continuous uniform, normal, triangle, quadratic, and Pareto. It is found that the performance measures increase monotonously with increasing expectation value and increasing standard deviation of the distributions. Additionally, we show that the distribution has only little influence on the performance measures for small standard deviations. For larger values of the standard deviation, the performance measures in the case of the Pareto distribution are significantly different compared to the other distributions. These observations are explained by a comparison of the Taylor expansions in terms of the distributions’ standard deviations. For the considered symmetric distributions, an extension of the well known Curzon–Ahlborn efficiency to a stochastic Novikov engine is given.

The material development cycle is becoming too slow if compared with other technologies sectors like IT and electronics. The materials scientists’ community needs to bring materials science back to the core of human development. ICME (Integrated Computational Materials Engineer) is a new discipline that uses advanced computational tools to simulate material microstructures, processes and their links with the final properties. There is the need for a new way to design tailor-made materials with a faster and cheaper development cycle while creating products that meet “real-world” functionalities rather than vague set of specifications. Using the ICME approach, cutting edge computational thermodynamics models were employed in order to assist the microstructure characterization and refinement during the TIG welding of a functionally graded composite material with outstanding wear and corrosion resistance. The DICTRA diffusion model accurately predicted the carbon diffusion during sintering, Thermo-Calc and TC-PRISMA models described the thermodynamic and kinetics of harmful carbide precipitation, while COMSOL Multhiphysic furnished the temperature distribution profile at every timestep during TIG welding of the material. Bainite transformation and the influence of chromium and molybdenum was studied and modelled with MAP_STEEL software. The simulations were then compared with experimental observations and a very good agreement between computational works and experiments was found for both thermodynamic and kinetics predictions. The use of this new system proved to be a robust assistance to the classic development method and the material microstructures and processes were carefully adjusted in order to increase corrosion resistance and weldability. This new approach to material development can radically change the way we think and we make materials. The results suggest that the use of computational tools is a reality that can dramatically increase the efficiency of the material development.

Current insulation solutions across multiple industries, especially the commercial sector, can be bulky and ineffective when considering their volume. Aerogels are excellent insulators, exhibiting low thermal conductivities and low densities with a porosity of around 95%. Such characteristics make aerogels effective in decreasing conductive heat transfer within a solid. These requirements are crucial for aerospace and spaceflight applications, where sensitive components exist among extreme temperature environments. When implemented into insulation applications, aerogel can perform better than existing technology while using less material, which limits the amount of volume allocated for insulation. The application of these materials into composites can result in enhancing a material's thermal and mechanical properties when exposed to mechanical testing. The main objective of this study was to perform theoretical and experimental analysis on a corrugated composite sandwich structure integrated with aerogel insulation by studying its effective thermal conductivity. The aerogel material used was Pyrogel XT-E, a silica aerogel-based fiberglass insulation manufactured by Aspen Aerogels. Theoretical models of the corrugated composite sandwich structure were constructed in ANSYS Workbench based on geometry from a previous study. The main goal of the theoretical models was to analytically and computationally study the effective thermal conductivity of this sample; the conditions of these simulations were modeled after the experimental setup. Additionally, two insulation studies were performed using the thermal models. The first study was performed on a flat plate structure to determine the optimal thickness of Pyrogel XT-E in a flat plate orientation. The second study compared multiple types of common insulation materials to Pyrogel XT-E when integrated into the corrugated composite sandwich structure model. As expected, aerogel particles and Pyrogel XT-E outperformed all insulation materials and had the lowest effective thermal conductivity. Experimental data was obtained using a test enclosure and a heating element source with an integrated temperature control circuit that was designed and built for this study. This experimental data was compared to the theoretical data obtained from the thermal model simulations. The corrugated composite sandwich structure did not perform as well as expected due to thermal bridging along the composite corrugation. Its effective thermal conductivity was much higher than that of the flat plate structure, even though the effective Pyrogel XT-E layer in the corrugated composite sandwich structure was more than twice as thick as the layer in the flat plate structure. Despite thermal bridging, the corrugated composite sandwich structure exhibits superb thermal resistance, which adds to its impressive strength. Thermal conductivity results from this study can be used to design efficient materials for high structural and thermal stress applications.

In-cylinder thermal barrier materials have been thoroughly investigated for their potential improvements in thermal efficiency in reciprocating internal combustion engines. These materials show improvements both directly in indicated work and indirectly through reduced demand on the cooling system. Many experimental and analytical sources have shown reductions in heat losses to the combustion chamber walls, but converting the additional thermal energy to indicated work has proven more difficult. Gains in indicated work over the expansion stroke could be made, but these were negated by increased compression work and reduced volumetric efficiency due to charge heating. Typically, the only improvements in brake work would come from the pumping loop in turbocharged engines, or from additional exhaust energy extraction through turbine-compounding devices. The concept of inter-cycle wall-temperature-swing holds promise to reap the benefits of insulation during combustion and expansion, while not suffering the penalties incurred with hotter walls during intake and compression. The combination of low volumetric heat capacity and low thermal conductivity would allow the combustion chamber surface temperature to quickly respond to the gas temperature throughout combustion. Surface temperatures are capable of rising in response to the spike in heat flux, thereby minimizing the temperature difference between the gas and wall early in the expansion stroke when the greatest conversion of thermal energy to mechanical work is possible. The combination of low heat capacity and thermal conductivity is essential in allowing this temperature increase during combustion, and in enabling the surface to cool during expansion and exhaust to avoid harmfully affecting engine volumetric efficiency during the intake stroke and minimizing compression work performed on the next stroke. In this thesis, thermal and thermodynamic models are constructed in an attempt to predict the effects of material properties in the walls, and to characterize the effects of heat transfer at different portions of the cycle on indicated work, volumetric efficiency, exhaust energy and gas temperatures of a reciprocating internal combustion engine. The expected impact on combustion knock in spark-ignited engines was also considered, as this combustion mode was the basis for the experimental engine testing performed. Conventional insulating materials were evaluated to benchmark the current state-of-the-art, and to gain experience in the analysis of materials with temperature-swing capability. Unfortunately, the effects of permeable porosity within the conventional coating on heat losses, fuel absorption and compression ratio tended to mask the effects of temperature swing. The individual impact of each of these loss mechanisms on engine performance was analyzed, and the experience helped to further refine the necessary traits of a successful temperature-swing material Finally, from the learnings of this analysis phase, a novel material was created and applied to the piston surface, intake valve faces, and exhaust valve faces. Engine data was taken with these coated components and compared to an un-coated baseline. While some of the test pieces physically survived the testing, analysis of the data suggests that they were not fully sealed and suffered from the same permeability losses that affected the conventional insulation. Further development is necessary to arrive at a robust, effective solution for minimizing heat transfer through wall temperature swing in reciprocating internal combustion engines. The success of temperature-swing thermal barrier materials requires very low thermal conductivity, heat capacity, and appropriate insulation thickness, as well as resilient sealing of any porous volume within the coating to avoid additional heat and fuel energy losses throughout the cycle.
Los materiales aislantes han sido investigados a fondo por sus posibles mejoras en la eficiencia térmica de los motores de combustión interna alternativos. Estas mejoras se ven reflejadas tanto directamente en el trabajo indicado como indirectamente a través de la reducción del sistema de refrigeración del propio motor. Diferentes estudios, tanto experimentales como analíticos, han mostrado la reducción en la transferencia de calor a través de las paredes de la cámara de combustión mediante la utilización de estos materiales. Sin embargo, demostrar la conversión de la energía térmica adicional en trabajo indicado ha resultado más difícil. En ciertos estudios se pudieron obtener mejoras en el trabajo indicado durante la carrera de expansión, pero éstas fueron reducidas debido a un menor rendimiento volumétrico debido al calentamiento de la carga durante el proceso de admisión y un mayor trabajo en la carrera de compresión. Típicamente, las únicas mejoras en el trabajo al freno provendrían de la reducción de pérdidas por bombeo en los motores turboalimentados, o de la extracción de la energía adicional de los gases de escape a través de turbinas. El concepto de los materiales con oscilación de la temperatura durante el ciclo motor intenta aprovechar los beneficios del aislamiento durante los procesos de combustión y expansión, mitigando las perdidas por el incremento de la temperatura de las paredes durante la admisión y la compresión. La combinación de baja capacidad calorífica y baja conductividad térmica permitiría que la temperatura de la superficie de la cámara de combustión respondiera rápidamente a la temperatura del gas durante el proceso de combustión. Las temperaturas de la superficie son capaces de aumentar en respuesta al pico de flujo de calor, minimizando así la diferencia de temperatura entre el gas y la pared en la carrera de expansión cuando es posible la mayor conversión de energía térmica en trabajo mecánico. La combinación de baja capacidad calorífica y conductividad térmica es también esencial para permitir este aumento de temperatura durante la combustión y para permitir que la superficie se enfríe durante la expansión y el escape para no perjudicar así el rendimiento volumétrico del motor durante la carrera de admisión y minimizar el trabajo de compresión realizado en el siguiente ciclo. En esta tesis se han desarrollado modelos térmicos y termodinámicos para predecir los efectos de las propiedades de los materiales en las paredes y caracterizar los efectos de la transferencia de calor en diferentes partes del ciclo sobre el trabajo indicado, el rendimiento volumétrico, la energía en los gases de escape y las temperaturas del gas para un motor de combustión interna alternativo. También se ha evaluado el impacto del uso de estos materiales en el knock en motores de combustión de encendido provocado, ya que los estudios experimentales de esta tesis se realizaron en un motor de estas características. Durante la investigación se evaluaron materiales aislantes convencionales para comprender el estado actual de esta técnica y para adquirir también experiencia en el análisis de materiales aislantes con oscilación de temperatura. Desafortunadamente, los efectos de la permeabilidad a través de la porosidad del material en los recubrimientos convencionales, la absorción de combustible y la relación de compresión tendieron a ocultar los efectos de la oscilación de la temperatura y la reducción de la transferencia de calor a través de las paredes. Así pues, se analizó el impacto individual de cada uno de estos mecanismos y su influencia en el rendimiento del motor para así definir un nuevo material con las características necesarias que mejorasen el aislante con de oscilación de temperatura. Finalmente, a partir de los estudios de esta fase de análisis, se creó un nuevo material y se aplicó a la superficie del pistón y a la supe
Els materials aïllants han estat investigats a fons per les seves possibles millores en l'eficiència tèrmica en el motors de combustió interna alternatius. Aquestes millores es veuen reflectides tant directament en el treball indicat com indirectament a través de la reducció del sistema de refrigeració del propi motor. Diferents estudis, tant experimentals com analítics, han mostrat la reducció en la transferència de calor a través de les parets de la cambra de combustió mitjançant la utilització d'aquests materials. No obstant això, demostrar la conversió de l'energia tèrmica addicional en treball indicat ha resultat més difícil. En certs estudis es van poder obtenir millores en el treball indicat durant la carrera d'expansió, però aquestes van ser reduïdes a causa d'un menor rendiment volumètric causat de l'escalfament de la càrrega durant el procés d'admissió i un major treball en la carrera de compressió. Típicament, les úniques millores en el treball al fre provindrien de la reducció de pèrdues per bombeig en els motors turbo alimentats, o de l'extracció addicional de l'energia dels gasos d'escapament a través de turbines. El concepte dels materials amb oscil·lació de la temperatura durant el cicle motor intenta aprofitar els beneficis de l'aïllament durant els processos de combustió i expansió, mitigant les perdudes per l'increment de la temperatura de les parets durant l'admissió i la compressió. La combinació de baixa capacitat calorífica i baixa conductivitat tèrmica permetria que la temperatura de la superfície de la cambra de combustió respongués ràpidament a la temperatura del gas durant el procés de combustió. Les temperatures de la superfície són capaços d'augmentar en resposta al flux de calor, minimitzant així la diferència de temperatura entre el gas i la paret en la carrera d'expansió quan és possible la major conversió d'energia tèrmica en treball mecànic. La combinació de baixa capacitat calorífica i conductivitat tèrmica és també essencial per permetre aquest augment de temperatura durant la combustió i el refredament de la superfície durant l'expansió i l'escapament per no perjudicar així el rendiment volumètric del motor durant la carrera d'admissió i minimitzar el treball de compressió realitzat en el següent cicle. En aquesta tesi s'han desenvolupat models tèrmics i termodinàmics per predir els efectes de les propietats dels materials en les parets i caracteritzar els efectes de la transferència de calor en diferents parts del cicle sobre el treball indicat, el rendiment volumètric, l'energia en els gasos d'escapament i les temperatures del gas per un motor de combustió interna alternatiu. També s'ha avaluat l'impacte d'aquests materials en el knock en motors de combustió d'encesa provocada, ja que les proves experimentals d'aquesta tesi es van realitzar en un motor d'aquestes característiques. Durant la investigació es van avaluar materials aïllants convencionals per comprendre l'estat actual d'aquesta tècnica i per adquirir també experiència en l'anàlisi de materials aïllants amb oscil·lació de temperatura. Desafortunadament, els efectes de la permeabilitat a través de la porositat del material en el recobriment convencional, l'absorció de combustible i la relació de compressió van tendir a ocultar els efectes de l'oscil·lació de la temperatura i la reducció de la transferència de calor a través de les parets. Així doncs, es va analitzar l'impacte individual de cada un d'aquests mecanismes i la seva influència en el rendiment del motor per així definir un nou material amb les característiques necessàries que milloressin el aïllant d'oscil·lació de temperatura. Finalment, a partir dels estudis d'aquesta fase d'anàlisi, es va crear un nou material i es va aplicar a la superfície del pistó i a la superfície interna de les vàlvules d'admissió i d'escapament. Les dades de motor es van prendre a
Andruskiewicz, PP. (2017). ANALYTICAL AND EXPERIMENTAL INVESTIGATION OF TEMPERATURE-SWING INSULATION ON ENGINE PERFORMANCE [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/90467
TESIS

This research focused on a comprehensive microstructural and mechanical property characterisation study of the Ni-Fe-Cr alloys 718 and 945X. The aim of the project was to better understand the relationship between performance and microstructure of existing (Alloy 718) and newly developed (Alloy 945X) high strength nickel alloys focusing on downhole applications. The main difference between the two alloys is that alloy 945X has lower Nb content than alloy 718, which may minimise the tendency to form delta when combined with correct processing. Previous studies have related the hydrogen embrittlement in alloy 718 with the collection of hydrogen by delta phase. Microstructural characterisation of the new alloy 945X after long term isothermal exposure up to 120 hours in the temperature range 650◦C to 900◦C was conducted with scanning electron microscopy (SEM), to generate a time-temperature-transformation (TTT) diagram. The TTT diagram was used as a road map for designing two isothermal heat treatments of alloy 945X on tensile specimens. Then, the effect of hydrogen charging on the tensile properties and microstructure of the 'as-received' and these two variant heat treatments was investigated. Fractographic analysis showed that, in the presence of hydrogen, intergranular fracture occurred for all the heat treatments, regardless the presence of delta phase at grain boundaries. There was no simple correlation between the volume fraction of delta-phase and susceptibility to hydrogen assisted embrittlement. Rather, it was demonstrated that the morphology and distribution of delta-phase along grain boundaries plays a key role and the other precipitate phases also have an influence through their effect on the ease of strain localisation. This study also examined the hydrogen embrittlement sensitivity of nickel alloy 718 given four different heat treatments to obtain various microstructural states. Each heat treatment leads to differences in the precipitate morphologies of γ', γ'' and delta phases. Material characterisation and fractography of the examined heat treatments were performed using a high resolution FEG-SEM. Three specimens of each condition were pre- charged with hydrogen and tensile properties were compared with those of non-charged specimens. It was observed that hydrogen embrittlement was associated with intergranular and transgranular microcrack formation, leading to an intergranular brittle fracture. delta phase may assist the intergranular crack propagation, and this was shown to be particularly true when this phase is coarse enough to produce crack initia- tion, but this is not the only factor determining embrittlement. Other microstructural features play a role, as does the strength of the material. Finally, the evolution of delta-(Ni3Nb) phase in alloy 718 from the early stages of precipitation, with a particular focus on identifying the grain boundary characteristics that favour precipitation of grain boundary delta phase was investigated. Results showed that delta phase was firstly formed on Σ3 boundaries after 5 hours at the examined temperature (800◦C). Increasing ageing time at 800◦C was observed to lead to an increase in size and precipitation of phases γ'-γ''-delta, an increase in fraction of the special CSL boundaries and an evolution in the morphology of twins and the growth of grains.

Antisense RNA (asRNA) strategies are identified as an effective and specific method for gene down-regulation at the post-transcriptional level. In this study, the major purpose is to find a correlation between the expression level and minimum free energy to enable the design of specific asRNA fragments. The thermodynamics of asRNA and mRNA hybridization were computed based on the fluorescent protein reporter genes. Three different fluorescent proteins (i) green fluorescent protein (GFP), (ii) cyan fluorescent protein (CFP) and (iii) yellow fluorescent protein (YFP) were used as reporters. Each fluorescent protein was cloned into the common pUC19 vector. The asRNA fragments were randomly amplified and the resulted antisense DNA fragments were inserted into the constructed plasmid under the control of an additional inducible plac promoter and terminator. The expression levels of fluorescent reporter protein were determined in real time by plate reader. Different results have been observed according to the fluorescent protein and the antisense fragment sequence. The CFP expression level was decreased by 50 to 78% compared to the control. However, with the GFP, the down-regulation did not exceed 30% for the different constructs used. For certain constructs, the effect was the opposite of expected and the expression level was increased. In addition, the YFP showed a weak signal compared to growth media, therefore the expression level was hard to be defined. Based on these results, a thermodynamic model to describe the relationship between the particular asRNA used and the observed expression level of the fluorescent reporter was developed. The minimum free energy and binding percentage of asRNA-mRNA complex were computed by NUPACK software. The expression level was drawn as a function of the minimum free energy. The results showed a weak correlation, but linear trends were observed for low energy values and low expression levels the CFP gene. The linear aspect is not verified for higher energy values. These findings suggest that the lower the energy is, the more stable is the complex asRNA-mRNA and therefore more reduction of the expression is obtained. Meanwhile, the non-linearity involves that there are other parameters to be investigated to improve the mathematical correlation. This model is expected to offer the chance to "fine-tune" asRNA effectiveness and subsequently modulate gene expression and redirect metabolic pathways toward the desired component. In addition, the investigation of the localization of antisense binding indicates that there are some regions that favors the hybridization and promote hence the down-regulation mechanisms.
Master of Science

La performance énergétique est un pilier pour réduire l'utilisation d'énergie non renouvelable, en plus de l'utilisation des énergies renouvelables. En fait, les bâtiments sont au cœur de la politique des performances énergétiques de l'UE puisque 40% de la consommation finale d'énergie et 36% des émissions de gaz à effet de serre provient des bureaux, magasins et autres bâtiments. Les bâtiments peuvent être considérés comme des systèmes dynamiques et le transfert de la chaleur dans les bâtiments peut être représenté en utilisant des modèles dynamiques. De cette façon, le transfert de la chaleur dans les bâtiments peut être décrit par des réseaux thermiques obtenus en utilisant la théorie des graphes et de la thermodynamique, et peuvent être déduits de l'équation de la chaleur classique. Les réseaux thermiques peuvent être exprimés comme un système d'équations différentielles et algébriques (DAE) qui peut être transformé en représentation d'état et obtenir un fonction de transfert à partir de laquelle un modèle autorégressif avec des variables exogènes (ARX) peut être obtenu. Ces différentes structures de modèle peuvent être utilisées pour identifier les paramètres physiques des réseaux thermiques, ce qui implique que la méthode peut être utilisée pour identifier la performance intrinsèque des bâtiments et aider à la réduction de la consommation d'énergie dans les bâtiments.Cela peut faciliter l'évaluation de la performance énergétique des bâtiments dans un cadre reproductible qui permet la comparaison entre différentes solutions constructives.Les principales contributions originales de cette thèse sont: 1) les réseaux thermiques sont présentées à partir de la théorie des graphes et de la thermodynamique, sans considérer l'analogie thermique-électrique; 2) l'équation classique de la chaleur est reliée explicitement avec un système de DAE (réseau thermique) par les éléments finis; 3) différentes transformations pour déduire des modèles du transfert de la chaleur avec signification physique, à partir de l'équation de la chaleur classique, sont présentées toutes ensemble; 4) les transformations entre les modèles sont effectuées à partir des réseaux thermiques jusqu’aux modèles autorégressifs avec des variables exogènes (ARX) et vice-versa; et 5) un critère de sélection de l'ordre du modèle par une analyse de fréquence des mesures est proposé
Energy efficiency is one of the two pillars to decrease the use of non-renewable energy besides the use of renewables energies. In fact, buildings are central to the EU's energy efficiency policy, as nearly 40% of the final energy consumption and 36% of greenhouse gas emissions take place in houses, offices, shops and other buildings. Buildings may be considered as dynamic systems and heat transfer in buildings may be represented using dynamic models. In this way, heat transfer in buildings may be described by thermal networks which may be stated considering graph theory and thermodynamics, and may be deduced from the classical heat equation. Thermal networks may be expressed as a system of linear differential algebraic equations (DAE) and the system of linear DAE may be transformed into a state-space representation from which an autoregressive model with exogenous (ARX) can be obtained. These different model structures may be used for identifying the physical parameters of thermal networks which implies that this methodology may be useful for identifying the intrinsic performance of buildings and tackling the reduction of non-renewable energy consumption in buildings. This may facilitate the assessment of energy efficiency of buildings within a reproducible framework which allows the comparison between different constructive solutions.The main original contributions of this dissertation are: 1) thermal networks are stated from graph theory and thermodynamics, leaving back the thermal-electrical analogy; 2) classical heat equation is connected explicitly to a system of DAE (thermal network) by using the finite elements; 3) the transformations for deducing heat transfer models with physical meaning from the classical heat equation are put altogether; 4) transformations between models may are done from thermal networks to autoregressive models with exogenous (ARX) and back; and 5) a criterion for selecting the order of the model by frequency analysis of measurements is proposed

The VIVACE European Cycle Program (“VIVACE-ECP”) was part of the virtual engine sub-project of VIVACE and was worth 6.63 million Euros. The main outcome of the “VIVACE-ECP” was the development of a cost effective gas turbine simulation environment called PROOSIS. PROOSIS, which is the Greek word for “propulsion”, is an acronym for “PRopulsion Object Oriented SImulation Software”. PROOSIS was developed by facilitating optimal use of multi-partner gas turbine performance simulation research and development resources and expertise. PROOSIS is a single framework which provides shared standards and methodologies for the European Union (EU) gas turbine community, including original equipment manufacturers (OEMs), industrial companies, universities and research centres. The primary objective of this doctoral thesis is to present advanced performance simulation models of gas turbine components and advanced fluid modelling capabilities developed by the author for the PROOSIS standard components library (SCLib). The main aims of this research are to provide a detailed insight into the effects of dissociation on fluid thermodynamic properties and subsequently on gas turbine performance. Detailed descriptions of the development of an advanced fluid model and a robust flow continuity model, which are the foundation of the PROOSIS standard component library, are provided. The effects of dissociation on isolated Burner and Afterburner components as well as overall engine performance are discussed with the aid of several case studies. Additionally, advanced performance simulation models of Burner and Afterburner components are presented. The development of an extended parametric representation of compressor characteristics is also analysed. Several advanced capabilities of PROOSIS (including test analysis, customer deck generation, 3D compressor zooming and distributed computing) are also introduced. The “evolution of PROOSIS” is presented with an in-depth analysis of the collaborative structure and project management of the VIVACE- ECP, as well as the channels of communication, technology transfer and quality control. A clear emphasis is placed on the contribution of the author to each of these tasks and subsequently the “VIVACE-ECP” as a whole. The main outcome of this work is the development of an advanced fluid model which comprises multi-dimensional fluid property tables for several fuels. The advanced fluid model also caters for “levels of dissociation” ranging from “no dissociation” to chemical equilibrium. This advanced fluid model is complimented by a robust flow continuity model, also developed by the author, which calculates the unknown local flow properties at any point in an engine model. These robust, advanced fluid and flow continuity models facilitate improved accuracy thereby providing a solid foundation for several advanced gas turbine performance simulation capabilities.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.
Includes bibliographical references (leaf 30).
2.670 is a required mechanical engineering class taught during the Independent Activities Period (IAP) at MIT in which each student constructs a Stirling Engine. For the most part, all of the engine parts are uniform, but if so desired, students are allowed to make design changes to certain parts in order to compete for the fastest engine at the end of the class. The research team in the MIT CADlab is working on an environment, called DOME, which makes it easy to link together simulations in different packages to perform integrated analysis and make them operable over the Internet. An integration environment has been created as a DOME project in which students can analyze and optimize the design of the 2.670 Stirling Engine. A thermodynamics model of the engine was created in Matlab and a parametric solid model was created in SolidWorks. Then, DOME was used to link the Matlab thermodynamic models to the Solidworks cad model so that when geometric parameters are changed one can see how this will affect engine performance. Students will be allowed to change the diameter and length of the displacer piston and see how it affects the work per cycle of the engine. In general, DOME was easy to learn how to use and the capabilities of web accessibility and the speed of design analysis and optimization was impressive. The future intention is that 2.670 students could use this integration environment to better analyze the 2.670 Stirling Engine.
by Munhee Sohn.
S.B.

Cette thèse évalue d'abord le potentiel thermodynamique du cycle au CO2 supercritique (sc-CO2) pour une large gamme de température de source chaude et étudie son couplage aux applications nucléaires, 45.7% d’efficacité thermique étant obtenu pour un réacteur à neutrons rapides refroidi au sodium. Des simulations CFD sont réalisées sur un compresseur à échelle réduite et confrontées à une expérience, apportant des éléments de qualification. Des simulations sur un compresseur à échelle 1:1 révèlent des particularités liées à la compression du sc-CO2 au comportement gaz réel, offrant un retour d’expérience pour la conception. Dans ce cadre, une approche de cartes de performance est proposée et validée à l'aide de simulations. Enfin, une étude de la collapse d’une bulle dans le CO2 liquide au voisinage du point critique est réalisée et indique l'absence d’effet destructif de cavitation, ouvrant la voie au fonctionnement du compresseur en phase liquide, lieu optimum de l'efficacité du cycle
This study first evaluates the thermodynamic performance of the supercritical CO2 (sc-CO2) cycle in a large range of heat source temperature, with a focus on the nuclear applications; a thermal efficiency of 45.7% is reported for a Sodium-cooled Fast Reactor. Second, CFD simulations have been performed on a small scale sc-CO2 compressor and results have been confronted positively with the experimental data. Simulation results on a real scale compressor have then revealed some particularities during the compression of a real fluid, providing feedbacks for the component design. In addition, a reliable performance maps approach has been proposed for the sc-CO2 compressor and validated using the CFD results. Finally, an investigation of bubble collapse in the liquid CO2 near the critical point has disclosed the likely absence of detrimental effects. As such, risks of cavitation damage should be low, favoring the compressor operation in the liquid region for cycle efficiency improvement

The investigation described in this thesis is aimed at determining the effect of heated air flow on the behaviour of capillary barriers. In order to achieve the objectives of this investigation, a number of tasks were undertaken, as described hereinafter. First, a laboratory scale testing was carried out to determine the effect of heated air flow on the volumetric water content (VWC) and matric suction in a layer of soil representing the coarse grained soil layer of a capillary barrier. Several types of instruments were used to measure the VWC, matric suction, and temperature at different locations within the soil. Next, a numerical analysis was undertaken to simulate the behaviour of the soil mass subjected to thermal changes in the laboratory experiments. Lastly, two case studies were analyzed with and without the heated air flow in the coarse grained soil layer to validate the proposed model. The method used in this investigation was based on: (1) application of temperature change at the perimeters of the pipes installed in the coarse grained soil layer near the interface between the fine grained and coarse grained soil layers; and, (2) application of suction as a boundary condition at the perforated parts of the pipes to decrease VWC and increase matric suction in the soil mass. Using this specific method, the results of the finite element analyses of the laboratory experiments and the two case studies demonstrated that the heated air flow through the coarse grained soil layer of a capillary barrier would improve its performance as a soil cover for a number of engineering applications. Comparisons of measured and calculated values of VWC and matric suction showed good agreement providing further proof of the validity of the method.

This thesis investigates the synergistic effect of thermodynamic inhibitors (TIs) including monoethylene glycol and Methanol towards KHI poly(ethyleneoxide-co-vinylpyrrolidone) (PEO-co-VP) on the natural gas hydrate inhibition. Hydrate were formed inside the high pressure cell. The effect of inhibitors’ concentrations (TIs, KHI, and TIs + KHI) and sub-cooling were examined by parameters (onset time, growth time, gas consumption, and percentage of hydrate conversion). The change of KHI concentrations were tested to understand the inhibitor’s behaviour.

Globally, there are vast amounts of low-grade heat sources from industrial waste and renewables that can be converted into electricity through advanced thermodynamic power cycles and appropriate working fluids. In this thesis, experimental research was conducted to investigate the performance of a small-scale Organic Rankine Cycle (ORC) system under different operating conditions. The experimental setup consisted of typical ORC system components, such as a turboexpander with a high speed generator, a scroll expander, a finned-tube condenser, an ORC pump, a plate evaporator and a shell and tube evaporator. R245fa was selected as the working fluid, on account of its appropriate thermophysical properties for the ORC system and its low ozone depletion potential (ODP). The test rig was fully instrumented and extensive experiments carried out to examine the influences of several important parameters, including heat source temperature, ORC pump speed, heat sink flow velocity, different evaporators and with or without a recuperator on overall R245fa ORC performances. In addition, in terms of the working fluid’s environmental impact, temperature match of the cycle heat processes and system compactness, CO2 transcritical power cycles (T-CO2) were deemed more applicable for converting low-grade heat to power. However, the system thermal efficiency of T-CO2 requires further improvement. Subsequently, a test rig of a small-scale power generation system with T-CO2 power cycles was developed with essential components connected; these included a plate CO2 supercritical heater, a CO2 transcritical turbine, a plate recuperator, an air-cooled finned-tube CO2 condenser and a CO2 liquid pump. Various preliminary test results from the system measurements are demonstrated in this thesis. At the end, a theoretical study was conducted to investigate and compare the performance of T-CO2 and R245fa ORCs using low-grade thermal energy to produce useful shaft or electrical power. The thermodynamic models of both cycles were developed and applied to calculate and compare the cycle thermal and exergy efficiencies at different operating conditions and control strategies. In this thesis, the main results showed that the thermal efficiency of the tested ORC system could be improved with an increased heat source temperature in the system with or without recuperator. When the heat source temperature increased from 145 oC to 155 oC for the system without recuperator, the percentage increase rates of turbine power output and system thermal efficiency were 13.6% and 14% respectively while when the temperature increased from 154 oC to 166 oC for the system with recuperator, the percentage increase rates were 31.2% and 61.97% respectively. In addition, the ORC with recuperator required a relative higher heat source temperature, which is comparable to a system without recuperator. On the other hand, at constant heat source temperatures, the working fluid pump speed could be optimised to maximise system thermal efficiency for ORC both with and without recuperator. The pressure ratio is a key factor impacting the efficiencies and power generation of the turbine and scroll expander. Maximum electrical power outputs of 1556.24W and 750W of the scroll expander and turbine were observed at pressure ratio points of 3.3 and 2.57 respectively. For the T-CO2 system, the main results showing that the CO2 mass flow rate could be directly controlled by varying the CO2 liquid pump speeds. The CO2 pressures at the turbine inlet and outlet and turbine power generation all increased with higher CO2 mass flow rates. When CO2 mass flow rate increased from 0.2 kg/s to 0.26kg/s, the maximum percentage increase rates of measured turbine power generation was 116.9%. However, the heat source flow rate was found to have almost negligible impact on system performance. When the thermal oil flow rate increased from 0.364kg/s to 0.463kg/s, the maximum percentage increase rate of measured turbine power generation was only 14.8%. For the thermodynamic analysis, with the same operating conditions and heat transfer assumptions, the thermal and exergy efficiencies of R245fa ORCs are both slightly higher than those of T-CO2. However, the efficiencies of both cycles can be enhanced by installing a recuperator at under specific operating conditions. The experiment and simulation results can thus inform further design and operation optimisations of both the systems and their components.

Internal combustion engines have been very successful as power producers in the marineapplicaiton due to their simplicity of construction, high efficiency and long track of proven technology. However, as the environmental foot print of industry is gaining more and more attention, the emission from the engine must be reduced. The main emission fromthe diesel engines are namely nitrogen oxide(NOx) and particulate matter(PM). Sulfuroxide(SOx) and carbon dioxide emission(CO2). In the marine industry, the transientemission has not been brought to the table of discussion when it comes down to theregulations. However, the assessment and improvement in the transient emission willgain more attention.In order to predict the emission from the diesel engine in the generic manner, the dynamic engine model should be developed. This model must be able to capture the in-cylinder process during the combustion in cylcle-to-cycle resolution. Transient load would put more challenges to the prediction as the in-cylinder states are far from the steady-state conditions. In the thesis, the dynamic simulation model of the diesel engine is developed in order to predict the emission. Firstly, the emission from the diesel engine, with special focus on NOx formation, is reviewed in general. Then overall process of the development of the mathmatical model of the diesel engine is described. Bond graph model was used as the framework of modeling approach. Finally the simulation result is compared with the test result from the laboratory and recommendations for further development are presented.The main contributions of the thesis are:• A overall process of building the engine model of was reviewed and implemented. It covers most of the building blocks from the thermodynamic calculation to the calculation of states of the components of the diesel engine.• The model developed in the project has significant improvement in terms of computational efficiency. Implementing Grill’s method for the calculation of the equilibrium composition of the combustion gas was the key to this success.• The bond graph model based on the multi-component gases in the combustion gases was constructed and it founded a ground for adaptation of the emission reduction strategy such as exhaust gas recirculation.• The overall model was built with component libraries which can be reused in the future project. Full description of the components libraries is given so that potential users may have the easy access.• A mathmatical model for NOx is coupled with the dynamic engine model together with the two-zone model approach. The calculation of the two-zone model in the absence of the pressure profile was achieved with an effective method so that calculation time has not increased significantly from the single zone model.

The difficulty that exists in accurately monitoring the performance of air conditioners has made performance prediction an arduous task. Nevertheless, the performance still needs to be monitored and predicted as it helps solve a lot of problems resulting from this technology like effect of the technology on the grid, energy consumption, water utilisation and GHGs emission. With the introduction of regression modelling as a means of system monitoring and prediction some years ago, the accuracy was still a call for concern. It is worth realising that increasing the number of predictors will enhance this method’s accuracy. As such, this document intends to increase the accuracy of this method’s monitoring and predicting ability by increasing the number of predictors to cut across system thermal, environmental and human behavioural variation. These predictors experimentally gotten are used to build an environ-behavioural model that monitors the coefficient of performance and energy consumption of a domestic split-type air conditioner with higher accuracy. Refrigerants have undergone evolution in the past decades in a bid to come up with a refrigerant that has zero ODP, lower – than – R22 GWP and much better than R22 thermodynamic performance. No pure refrigerant has been found to possess these qualities as such mixtures or blends are the best shot at the moment. R410A could stand the test of time to be the long term R22 replacement but for the fact that besides R410A’s higher GWP than that of R22, the former’s system performance is lower than that of the latter’s due to the lower thermodynamic performance of the former. This means the search continues. In this document, a combination of carefully chosen refrigerant components are carefully blended to come up with a simulation based R22 long term replacement, which will be referred to in this document as BTEP.

Orientador: Marco Aurélio Cremasco
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
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Resumo: O piperonal (ou heliotropina) apresenta aplicações industriais no ramo de cosméticos como fixador de fragrâncias, além de ser matéria prima para componentes de maior valor agregado, como a piperina que é empregada como antiiflamatorio; a vanila que tem aplicações antioxidantes; o pirebidil e a L-dopa que são agentes anti Parkinson. A síntese do piperonal, a partir do óleo essencial da pimenta longa (Piper hispidinervum C. DC), não gera um produto 100 % puro, dessa forma vê-se a importância de estudar uma maneira de separar o piperonal dos demais compostos, safrol, isosafrol e terpinoleno, também presentes no produto final da síntese. Dentre os métodos de purificação há a cromatografia líquida de alta eficiência, que ao longo do tempo mostrou-se eficaz na purificação e separação de diversos compostos. O método de separação baseada em cromatografia líquida de alta eficiência depende de diversos fatores, tais como a escolha da fase estacionária e da fase móvel, bem como estudos preliminares para a posterior implementação das variáveis definidas em uma escala semi preparativa ou preparativa. Na presente Dissertação a fase estacionária utilizada foi à sílica C18 e a fase móvel uma mistura binária 70/30 (v/v) de etanol e água. A escolha da fase móvel binária deveu-se aos bons resultados de resolução obtidos entre o componente de interesse, o piperonal, e o safrol, isosafrol e terpinoleno. A resolução alcançada para o piperonal com relação aos demais componentes, safrol e isosafrol foi de 2,986 e para o terpinoleno 6,900, a literatura relata que valores acima de 1,5 representam uma completa separação. A estimativa de parâmetros chave para a coluna, como a porosidade da partícula e a fração de vazios do leito, foram obtidas por meio do método dos momentos e as isotermas de adsorção por análise frontal. As isotermas foram determinadas entre 20 e 35 ºC, com passo de 5 ºC, apresentaram uma configuração linear. De posse das isotermas, foi possível estimar os valores das constantes modificadas de Henry e as grandezas termodinâmicas ?G, ?H e ?S para o sistema, por meio do gráfico de van't Hoff. Os valores de entalpia apontam que o piperonal é o composto menos retido, pois apresenta uma entalpia igual a -1,134 KJ mol-1, o maior valor se comparado com os obtidos para o safrol, isosafrol e terpinoleno, o que demonstra a baixa interação com a fase estacionária, e consequentemente um baixo tempo de retenção do composto na coluna. Esse efeito foi comprovado com os resultados obtidos para a entropia, o piperonal foi o composto que apresentou o maior valor (6,812 J mol K-1). Ao passo que o terpinoleno apresentou um valor igual a -6,485 J mol K-1. Estes valores descrevem que a retenção do piperonal é menor se comparada com a retenção do terpinoleno. Essas distinções proporcionaram a separação entre os compostos
Abstract: Piperonal (or heliotropine) presents industrial applications in the field of cosmetics as fragrance fixative, besides being the raw material for value-added components such as piperine which is employed as anti-inflammatory, vanilla which has antioxidants applications, pirebidil and L -dopa which are anti Parkinson's disease. The synthesis of piperonal, from the Piper hispidinervum C. DC, does not generate 100% pure product, that way we can see the importance of studying a way to purify piperonal from the others compounds, safrole, isosafrole and terpinoleno, also presente in the final product of the synthesis. A method to be studied is high performance liquid chromatography, which has been proved as an effective in the purification and separation of various compounds. The separation method based on high performance liquid chromatography depends on several factors, such as the choice of stationary phase and mobile phase, as well as preliminary studies for further implementation of the defined variables in a semi-preparative or preparative scale. In the present study silica gel C18 was used as stationary phase and mobile phase was a binary mixture 70/30 (v / v) ethanol and water, respectively. The choice of the binary mobile phase was due to the good results of resolution between the component of interest, piperonal, and others; safrole, isosafrole and terpinolene. The resolution achieved for piperonal in relation to other components, safrole and isosafrole was 2.986 and 6.900 for terpinoleno. The literature reports that values above 1.5 represent a complete separation. The estimation of key parameters for the column, such as the porosity of the particle and the bed porosity were obtained by the moment method and adsorption isotherms by frontal analysis. The isotherms determined between 20 and 35 º C, with steps of 5 º C showed a linear configuration. With the isotherms in hands, it was possible to estimate the values of the Henry constants and the thermodynamics parameters for the system through the van't Hoff graphical. The enthalpy values point out that piperonal is the less retained compound, because it shows an enthalpy value equal to -1.134 KJ mol-1, the greater value if we compare to the safrol, isosafrol and terpinoleno values, this value demonstrate low interaction with the stationary phase and, consequently, a low retention time of the compound in the column. This effect was proved by the entropy values, piperonal showed the greater entropy (6.812 J mol K-1). The terpinoleno showed a value equal to -6.485 J mol K-1. These values describe that piperonal retention is smaller if we compare to terpinoleno retention. This difference makes possible the separation between the compounds
Mestrado
Engenharia de Processos
Mestre em Engenharia Química

Theoretical bounds for performance measures of thermodynamical systems are investigated under conditions of finite times and rates of processes using endoreversible models. These models consist of reversible operating sub-systems which exchange energy via generally irreversible interactions. Analytical and numerical calculations are performed to obtain performance optima and respective optimized process and design parameters for four model systems. A heat engine where the heat transfer between the working fluid and heat reservoirs is described by generalized, polytropic process is optimized for maximum work output. Thermal efficiencies, optimal values for temperatures and process times of the heat transfer processes are determined. A model of a generalized system suited to describe the operation of heat engines, refrigerators, and heat pumps is optimized with respect to thermal efficiency. Several examples illustrate how the results of the analysis are used to allocate financial resources to the heat exchanger inventory in an optimal way. A power-producing thermal system which exchanges heat with several heat reservoirs via irreversible heat transfer processes is analyzed to find the optimal contact times between the working fluid and each of the reservoirs. The piston motion of a Diesel engine is optimized to achieve maximum work for a given amount of fuel. The endoreversible model of the Diesel engine accounts for the temporal variations of the heat produced by the combustion process, the basic flow pattern within the engine's cylinder, the temperature dependence of the viscosity, thermal conductivity, and heat capacity of the working fluid and losses due to friction and heat leak through the cylinder walls
Theoretische Grenzen für verschiedene Leistungsmerkmale von thermodynamischen Systemen werden unter der Bedingung endlicher Zeiten und Prozessraten im Rahmen endoreversibler Modelle untersucht. Diese Modelle bestehen aus reversiblen Subsystemen, welche über allgemein irreversible Wechselwirkungen Energie austauschen. Analytische und nummerische Berechnungen quantifizieren diese Grenzen und liefern optimale Prozess- und Konstruktionsparameter für vier Modellsysteme. Für eine auf maximale Ausgangsarbeit optimierte Wärmekraftmaschine, bei der die Wärme zwischen Arbeitsmedium und Wärmereservoirs während allgemeiner polytroper Zustandsänderungen des Arbeitsmediums übertragen wird, werden optimale Temperaturen und Zeiten für die Wärmeübertragungsprozesse sowie die thermischen Wirkungsgrade bestimmt. Für ein wirkungsgrad-optimiertes Modell eines verallgemeinerten thermischen Umwandlungssytems, das sowohl Wärmekraftmaschinen, Kühler und Wärmepumpen beschreibt, wird die optimale Verteilung von Investitionskosten auf die Wärmetauscher ermittelt und die Anwendung der allgemeingültigen Ergebnisse anhand mehrerer Beispiele demonstriert. Für eine Wärmekraftmaschine mit mehreren Wärmereservoirs wird bestimmt, welche der Wärmereservoirs wie lange kontaktiert werden müssen, um eine maximale Ausgangsarbeit zu erzielen. Für einen Dieselmotor wird die Kolbenbewegung so optimiert, dass bei gegebener Treibstoffmenge eine maximale Ausgangsarbeit erzielt wird. Das endoreversible Modell des Dieselmotors berücksichtigt die Temperaturabhängigkeit der Wärmekapazität, Wärmeleitfähigkeit und Viskosität des Arbeitsfluids, die Zeitabhängigkeit des Verbrennungsprozesses sowie Reibungs- und Wärmeverluste

Orientador: Marco Aurélio Cremasco
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
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Resumo: O ácido (RS)-2-(4-(2-metilpropil)fenil)propanoico, conhecido como ibuprofeno, é um importante fármaco anti-inflamatório não esteroidal, também notório por suas propriedades analgésicas e antipiréticas. A droga é comercializada em sua forma racêmica, no entanto em alguns países é empregado apenas o S-(+)-ibuprofeno que detém o princípio ativo. Além disso, o R-(-)-ibuprofeno provoca toxicidade devido à formação de triglicerídeos híbridos no organismo humano. Substâncias que desempenham funções biológicas no corpo necessitam de métodos eficazes de separação e purificação. Os métodos cromatográficos se apresentam como uma alternativa para obter as formas isoladas de enantiômeros com elevado grau de pureza. No presente trabalho, estudou-se estabelecer condições necessárias para a separação eficaz em escala analítica por meio da abordagem termodinâmica do fenômeno. A separação foi realizada com o método direto empregando uma coluna quiral recheada com sílica recoberta por tris (3,5-dimetilfenilcarbamato) de celulose. A fase móvel composta por n-hexano e isopropanol na proporção 99/1 foi definida com base nos parâmetros cromatográficos seletividade e resolução. O aditivo ácido trifluoracético também foi utilizado na fase móvel para melhorar a definição dos picos cromatográficos. Após a determinação das fases estacionária e móvel, iniciou-se a caracterização da adsorção envolvida na separação. A ordem de eluição dos enantiômero foi verificada por dicroísmo circular e polarimetria, desta forma constatou-se que o S-(+)-ibuprofeno é o composto mais retido. A porosidade total foi determinada com o método do primeiro momento utilizando o 1,3,5-tri-terc-butilbenzeno, um composto pequeno o suficiente para se difundir tanto entre as partículas do leito quanto em seus interstícios. O valor obtido foi de 0,647. A abordagem do primeiro momento do pulso cromatográfico também possibilitou a determinação da constante de equilíbrio de adsorção para cinco temperaturas entre 15 °C e 35 °C. Neste estudo utilizou-se a porosidade total e o comprimento do leito como parâmetros do método para realizar a linearização do tempo de retenção versus o inverso velocidade da fase móvel. Por fim, os parâmetros entálpicos e entrópicos de adsorção foram calculados por meio da abordagem cromatográfico da equação de van¿t Hoff. Este equacionamento possibilitou definir o fenômeno como endotérmico, no qual ocorreu adsorção física. O composto mais retido apresentou valor de 8,76 kJ mol-1 para a variação de entalpia, enquanto o R-(-)-ibuprofeno 7,21 kJ mol-1. A temperatura isoenantiosseletiva calculada foi 237,38 K
Abstract: The (RS)-2-(4-(2-methylpropyl)phenyl) propanoic acid, known as ibuprofen, is an important non-steroidal anti-inflammatory drug, notorious for its analgesic and antipyretic properties. The drug is commercialized in its racemic form. However in some countries only the S-(+)-ibuprofen is used, which it is the active isomer. Since the R-(-)-ibuprofen is toxic due to forms hybrid triglycerides in the human body. Substances with biological functions in the body must undergo effective methods of separation and purification. Chromatographic methods are an alternative for the separation of enantiomers with high purity. In the present study the necessary conditions for effective separation in analytical scale by means of thermodynamic approach of the phenomenon was studies. The separation was carried out employing a chiral column packed with silica coated with cellulose tris (3,5-dimethylphenylcarbamate). The mobile phase consisting of n-hexane and isopropanol in ratio 99/1 was defined on the basis in chromatographic parameters as selectivity and resolution. The trifluoroacetic acid additive also was used on the mobile phase to improve the resolution of the chromatographic peaks. After the determination of stationary and mobile phases, the characterization the adsorption involved in the separation was studies. The order of elution of the enantiomers was checked by circular dichroism and polarimetry. It was observed that the S-(+)-ibuprofen is the most retained compound. The total porosity was determined by first moment using 1,3,5-tri-tert-butylbenzene. This molecule is small enough to diffuse through the bed particles, but also the between the particles interstices. The value obtained was 0,647. The approach of first moment of the chromatographic pulse also allowed the determination of the adsorption equilibrium constant for five temperatures between 15 °C and 35 °C. In this study, the bed void and bed length were used as input parameters in the perform linearization of retention time versus the mobile phase inverse velocity. Finally, the enthalpy and entropy of adsorption were calculated by means of chromatographic approach usual the van't Hoff equation. The adsorptions of enantiomers were endothermic. Both molecules adsorbed physically. The enthalpy of the most retained compound was 8,76 kJ mol-1 and 7,21 kJ mol-1 for R-(-)-ibuprofeno. The enantioselective temperature was 237,38 K
Mestrado
Engenharia de Processos
Mestre em Engenharia Química

Le chauffe-eau thermodynamique (CET), dont le principe repose sur une pompe à chaleur (PAC), est l’une des principales solutions pour répondre à l’enjeu de réduction des consommations énergétiques des bâtiments liées à l’eau chaude sanitaire. Le CET le plus courant sur le marché français est composé d’une PAC sur air extérieur, au R134a, dont le condenseur est de type manteau, entourant le ballon de stockage. Bien que le système arrive à maturité, les performances annuelles semblent encore loin des performances théoriques. Cette thèse a donc pour objectif l’optimisation des performances énergétiques des CET, en partant du CET standard français, selon un principe de compromis technico-économique. Pour cela, un modèle détaillé du CET standard est élaboré. La PAC est modélisée sous Dymola à l’aide de la bibliothèque TIL. Le ballon de stockage est modélisé par une combinaison d’une approche zonale et d’un modèle 1D. Ce modèle détaillé est calibré et validé expérimentalement grâce à des essais d’un CET standard réalisé en enceintes climatiques. Ce modèle est ensuite utilisé pour identifier les principaux gisements d’économie d’énergie. Une première analyse permet d’identifier les paramètres les plus influents sur les performances du CET. Cette sélection conduit ensuite à l’élaboration d’un modèle simplifié, plus apte à étudier des périodes longues de fonctionnement en intégrant des critères de coût et de confort. Une étude spécifique, à l’aide d’un algorithme génétique, permet d’évaluer le potentiel d’optimisation lié au pilotage du CET. Une étude multi-paramétrique montre ensuite que le design des échangeurs joue également un rôle important. Les résultats de ces deux voies prometteuses d’optimisation du CET étant inter-dépendants, une dernière partie consiste en une étude multi-critère. Les résultats montrent qu’avec la nouvelle configuration proposée sont obtenus, un meilleur confort thermique sur une plus large gamme de scénario, une augmentation de COP moyenne annuelle de 37 % et une réduction moyenne de facture électrique de 30 %
Heat Pump Water Heaters (HPWH) are efficient and fast-developing sanitary hot water production systems relying on a heat pump thermodynamic cycle for heat generation, consequently offering a considerable energy saving potential in the buildings sector. The most forthcoming HPWH on the French market are Air-Source Heat Pump Water Heaters (ASHPWH) composed of an exterior air source R134a heat pump and using a wrap-around type condenser, surrounding the thermal storage tank (TST). However, it is found that although these ASHPWH have reached an important level of maturity, it seems that there is still room for improvement of their energy performance. Consequently, the main objective of this PhD thesis is to search for optimization pathways, starting of from the reference ASHPWH on the French market, leading a better technical and economical compromise in terms of ASHPWH design. To reach this objective, a detailed model is first developed using Dymola (Modelica langage). This model comprises of a zonal model and a 1D model for the TST associated to an air source heat pump modeled with the TIL thermal component modeling library. After model calibration, the model is validated thanks to a large set of experimental tests carried out on a standard ASHPWH in climatic cells. The validated model is then used to identify optimization pathways by carrying out annual simulations and identifying energy performance improvement potentials. It is found out that both thermodynamic cycle performance and improved ASHPWH control logics are major contributors to the final energy performance. Both being highly interdependent and impacting energy performances, but also comfort and ASHPWH cost, the last part of the study consists of a multi-criteria optimization. Finally, a new ASHPWH design is proposed achieving better thermal comfort upon a large variety of user draw-off profiles, achieving a 37 % average annual energy saving and a 30 % reduction of the electrical bill

Les besoins en énergie dédiés au chauffage et à l'eau chaude sanitaire dans des bâtiments, caractérisés par des pics de consommation en début et en fin de journée tout comme en hiver, représentent un défi d’importance vis-à-vis de l'utilisation des énergies renouvelables. Une des technologies les plus prometteuses, se présente sous la forme d’un système de stockage d'énergie dit thermochimique (TCES). Ce mode de stockage permet en effet de stocker différents types d'énergie sous la forme d’un potentiel chimique et est caractérisé par une absence de dissipation d'énergie. En tant que matériau de stockage thermochimique récemment étudié, l'ettringite conviendrait ainsi à une utilisation à grande échelle en raison de sa non-toxicité, de son faible coût de production et de sa haute densité énergétique à basse température de fonctionnement. Cette thèse avait pour premier objectif d’étudier les propriétés physico-chimiques de l’ettringite et les mécanismes réactionnels lors des processus d'hydratation (formation d’ettringite) et de déshydratation (formation de méta-ettringite). Les connaissances acquises lors de ces travaux de thèse, vis-à-vis de la cinétique des réactions et des diagrammes thermodynamiques (Déshydratation: Ett30.6 → Ett30 → Met12 → Met6; Hydratation: Met7.4 → Met12 →hydrate de 24H2O→ hydrates supérieurs), permettront ainsi de mieux utiliser l'ettringite pour stocker/déstocker de la chaleur (à différentes conditions isothermes et isobares). Après avoir étudié les propriétés de l'ettringite pure, trois liants cimentaires distincts pouvant être produits industriellement ont été utilisés afin de tester des teneurs en ettringite différentes mais aussi des mélanges de phases hydratées particulières. Les travaux effectués ont permis d’étudier les mécanismes de carbonatation de ces différents matériaux ettringitiques et de déduire plusieurs informations pertinentes quant à leur durabilité dans le cadre d’une utilisation en tant que TCES. Enfin, le matériau cimentaire ettringitique le plus résistant au phénomène de carbonatation a été caractérisé par différentes techniques d’analyse afin de mieux maitriser l’influence des paramètres thermo-physiques sur sa performance énergétique. Ce matériau a ensuite été in-corporé dans un réacteur à lit fixe, sous la forme d’un lit poreux de 56 mm de hauteur composé de granulés de 1 à 2 mm de diamètre. Le processus de chargement/déchargement de l'énergie a été réalisé pour étudier la réversibilité du couple ettringite/méta-ettringite dans diverses conditions expérimentales. Les essais réalisés dans le réacteur ont alors montré qu’une puissance instantanée maximale de 915 W par kg de matière hydratée initiale et une densité de déstockage d'énergie de 176 kWh/m3 pouvaient être obtenues. Ces données seront très utiles pour envisager un futur prototype (à l’échelle 1:1) d’un système de chauffage contenant de l’ettringite et destiné aux bâtiments
The high energy demands for space heating and domestic hot water in buildings, character-ized by peaks in consumption at the beginning and end of the day as well as in winter, repre-sent a major challenge in terms of the use of renewable energies. A system of thermochemical energy storage (TCES), one of the most promising accessible technologies, could store different types of energies as chemical potential without energy dissipation. As a recently studied TCES material, ettringite is suitable for large scale use due to its no-toxicity, low material cost, and high energy density at lowing operating temperature. The first objective of this thesis was to study the physicochemical properties of ettringite and the reaction mechanisms during the hydration (formation of ettringite) and dehydration (formation of meta-ettringite) processes. The knowledge obtained on the reaction kinetics and thermodynamics (Dehydration: Ett30.6 → Ett30 → Met12 → Met6; Hydration: Met7.4 → Met12 →24-hydrate → higher hydrates) allows better use of ettringite for heat storage/release (under different isothermal and isobaric conditions). After having studied the properties of pure ettringite, three different cementitious binders that are industrially producible were used to test different ettringite contents but also mixtures of particular hydrated phases. The work carried out made it possible to study the carbonation mechanisms of these different ettringite materials and to deduce some relevant information as to their durability in terms of their use in TCES. Finally, the ettringite-based material most resistant to the carbonation phenomenon has been characterized by different analysis techniques in order to better control the influence of ther-mo-physical parameters on its energy performance. This material was then incorporated into a fixed bed reactor in the form of a 56 mm high porous bed composed of granules (1–2 mm in diameter). The energy charging / discharging process carried out to study the reversibility of ettringite / meta-ettringite under various experimental conditions. The reactor tests then showed that a maximum instantaneous power of 915 W per kg of initial hydrated material and an energy-releasing density of 176 kWh/m3. These results will be very useful in designing a future prototype (in scale 1:1) containing ettringite materials for a heating system in buildings

L’accroissement de la variabilité temporelle de la production et de la consommation d’énergie et la multiplication des vecteurs énergétiques sont des déterminants du contexte énergétique à venir. Une approche possible pour gérer ces contraintes est le développement de systèmes multifonctionnels (multi-effets utiles) incluant une fonction de stockage d’énergie. Pour développer de tels systèmes, ce travail propose de coupler deux cycles thermodynamiques afin de combiner leurs fonctionnalités : le cycle innovant ainsi réalisé, dit « hybride », associe multifonctionnalité, flexibilité et compacité. L’un des cycles hybrides envisageables est le cycle thermochimique hybride, construit à partir (i) du cycle tritherme à sorption solide/gaz (cycle thermochimique), qui permet de stocker une énergie thermique (sous forme de potentiel chimique) et de produire un effet frigorifique à la demande, et (ii) du cycle organique de Rankine (ORC), qui est le cycle ditherme le plus performant pour la production de travail mécanique à partir d’une source de chaleur à basse température.Un état de l’art des travaux existants sur les cycles thermodynamiques hybrides impliquant un procédé à sorption a été réalisé. Il a démontré leur fort potentiel de valorisation d’énergie thermique à basse température (i.e. inférieure à 250 °C) sous la forme d’une cogénération de froid et travail mécanique, mais a également mis en évidence la nécessité d’élargir la gamme de réactifs et les configurations de cycles et d’approfondir l’analyse du comportement dynamique de ces cycles.Ainsi, la première partie de cette thèse a porté sur le développement d’une analyse thermodynamique large du cycle thermochimique hybride utilisant l’ammoniac comme gaz réactif et fluide de travail, focalisée sur les sources chaudes à moins de 250 °C (correspondant à la valorisation de chaleur à basse température) : 5 modes de fonctionnement du cycle ont été identifiés et leurs performances énergétiques et exergétiques ont été évaluées pour un grand nombre de sels réactifs solides. Parmi ces cinq modes permettant la cogénération de froid et travail mécanique, 3 privilégient la production de froid: leur proportion de travail mécanique produit varie de 0 à 30 % et leurs rendements énergétique et exergétique atteignent respectivement 0,61 et 0,40. Pour les 2 autres modes, la production de travail est privilégiée : la proportion de travail produit varie entre 50 et 100 % et les rendements énergétique et exergétique atteignent respectivement 0,24 et 0,40. Dans la gamme de réactifs analysée, la température de source chaude minimale requise est 87 °C, et la densité énergétique de stockage (rapportée au volume total de stockage) atteint 170 kWh/m3. L’analyse thermodynamique a été complétée par une comparaison des performances du cycle hybride avec celles d’un système construit à partir de procédés commercialisés et équivalent en termes de fonctionnalités (stockage de la chaleur à basse température et cogénération de froid et électricité).Dans un second temps, le comportement dynamique du cycle thermochimique hybride a été analysé afin d’approfondir la problématique du couplage entre l’organe de détente et le réacteur du cycle, qui constitue un verrou scientifique majeur. Pour ce faire, des modèles de comportement dynamique ont été développés pour chacun des composants du cycle, puis pour le cycle complet. A partir de ces modèles, un outil de simulation numérique du comportement dynamique global a été développé. Trois méthodes de contrôle de l’organe de détente ont été proposées (pression de refoulement, vitesse de rotation ou puissance mécanique constante) et intégrées à cet outil de simulation. Ces simulations ont permis de quantifier les effets de la stratégie de pilotage de ce composant sur la dynamique (températures, pressions, débits, puissances) et les performances globales du cycle, en vue d’une application expérimentale
The increasing time-variability of energy supply and demand, along with the increasing number of energy carriers, are decisive issues in the upcoming energy context. One way to address these issues is to develop multi-purpose systems (i.e. systems providing several useful effects) integrating an energy storage feature. Developing such systems can be achieved by coupling two thermodynamic cycles in order to combine their respective features: the resulting innovative cycle, which is called a “hybrid” cycle, combines multifunctionality, flexibility and compactness. One relevant hybrid cycle is the hybrid thermochemical cycle: it is built upon (i) the three-temperatures solid/gas sorption cycle (thermochemical cycle), which enables storage of the input thermal energy (in the form of chemical energy) and provides a refrigeration effect, and (ii) the organic Rankine cycle (ORC), which is the most efficient two-temperatures cycle for providing mechanical work from a low-grade heat source.A state of the art in the field of hybrid thermodynamic cycles involving a sorption process is achieved. It points out the promising potential of these cycles for the cogeneration of power and cold from a low-grade heat source (at temperatures under 250 °C), as well as the need for investigations in a larger range of reactants and cycle configurations and for a deeper understanding of their dynamic behavior. The first part of this thesis work deals with the development of a wide thermodynamic analysis of the hybrid thermochemical cycle using ammonia as reactive gas and working fluid, focusing on heat source temperatures under 250 °C (low-grade heat sources) : 5 operating modes of the hybrid thermochemical cycle are identified and their energy and exergy performances are assessed for a wide range of solid reactive salts. Among these five modes providing power and cold cogeneration, 3 have a prevailing cold production: their share of mechanical work in useful effects ranges from 0 to 30 % and their energy and exergy efficiencies reach 0.61 and 0.40, respectively. The 2 other modes have a prevailing power production: their share of mechanical work in useful effects ranges from 50 to 100 % and their energy and exergy efficiencies reach 0.24 and 0.40, respectively. The minimal heat source temperature required for running the hybrid cycle is 87 °C and the energy storage density (related to the total volume of storage components) reaches 170 kWh/m3. The thermodynamic analysis is enriched through a comparison of the performances of hybrid thermochemical cycle with those of an alternative system made of well-known commercially available processes, providing the same features (low-grade heat storage and conversion into power and cold).At a later stage, an analysis of the dynamic behavior of hybrid thermochemical cycle is proposed to deepen the coupling between the expansion device and the reactor of the cycle, which is a key scientific issue. To this end, dynamic models are built for each component and then for the whole cycle. Starting from these models, a numerical tool is developed for the simulation of the overall dynamic behavior of the cycle. For the expansion device, three control procedures are proposed (constant exhaust pressure, constant rotation speed or constant mechanical power) and included in the numerical simulation tool: this enables quantifying the effects of the driving strategy of the expansion device on the dynamics (temperatures, pressures, flow rates and powers) and global performances of the cycle, which is needed for the upcoming experimental setup

Une des principales applications de la refrigeration cryogenique par cycle de joule-thomson consiste au refroidissement, dans la gamme 80-100 k, de detecteurs infrarouges ou de composants electroniques, au sol ou embarques. Pour ce type d'application, la simplicite technologique et la robustesse des mini-refroidisseurs utilises en circuit ouvert a l'atmosphere (alimentation a partir de reservoirs de gaz comprime) sont gages de fiabilite. Cependant, l'efficacite mediocre du cycle, due a une consommation specifique ainsi qu'un rapport de pressions hp/bp eleves, le rend inadapte aux applications necessitant une forte autonomie. L'amelioration des performances du refroidisseur (puissance frigorifique specifique et temps de mise en froid) est possible grace a l'utilisation de melanges gazeux azote-hydrocarbures plus performants que les gaz purs habituellement employes dans cette gamme de temperature. La reduction de la pression d'alimentation occasionnee permet alors le developpement de refrigerateurs autonomes, avec une efficacite thermodynamique et une fiabilite accrues. L'approche theorique met en uvre l'equation d'etat de peng-robinson, permettant de traduire le comportement des melanges gazeux a forte pression et a basse temperature. Les resultats experimentaux obtenus sur un refrigerateur prototype sont en bon accord avec la theorie. Ils sont egalement tres encourageants puisqu'une capacite de refrigeration comparable a celle de l'azote a une pression d'entree de 100 a 130 bars a pu etre atteinte grace a des melanges gazeux azote-methane-ethane-propane specifiques avec des pressions aussi basses que 30 a 40 bars, a une temperature tres voisine de celle de l'azote liquide (80-82 k)

La gamme de produits fils fins commercialisée par METALOR est basée sur des alliages d’argent, de cuivre et de palladium à hautes performances électrique et mécanique, à l’exemple du produit NOVAE1 qui présente une résistance mécanique de 1,3 GPa et une conductivité électrique de 17 % IACS. L’objectif de cette étude est de comprendre les mécanismes métallurgiques à l’origine de ces caractéristiques et de les mettre à profit afin de proposer une nouvelle gamme d’alliage à conductivité améliorée tout en conservant une résistance mécanique élevée. L’étude préliminaire menée sur le système binaire Cu-Pd met en évidence la présence de la phase βCuPd en-dessous de 600°C, dont la conductivité électrique est évaluée à 30 % IACS. Cette phase est mise en évidence expérimentalement dans le fil fin NOVAE1 et sa formation est associée à une augmentation de la conductivité de 8 % IACS. Ce pourrait donc être une réponse prometteuse pour le développement des nouveaux alliages. Des expériences ciblées ont été menées sur sept nuances d’alliages élaborés et recuits pendant plusieurs mois à 727 °C et 550 °C et caractérisés ensuite par microsonde, DRX et MEB. Ces nouvelles données permettent d’affiner la description thermodynamique du système ternaire Ag-Cu-Pd, en particulier de la lacune miscibilité, constituée des deux solutions solides cfc α1 et α2 et de l’extension de la phase βCuPd dans le système ternaire. La caractérisation multi-échelle du fin fil NOVAE1 met évidence la structure complexe, triphasée et nanostructurée de l’échantillon. Ces observations permettent la mise au point de modèles phénoménologiques des propriétés mécanique et électrique des fils en considérant une matrice constituée de phase α1 riche en Ag, associée à une phase molle dans laquelle sont incluses des domaines de phases dures riches en Cu et Pd, α2 et βCuPd. Les caractéristiques du fil sont ainsi évaluées en fonction de leur composition chimique. Cela met en évidence les paramètres clés du système : proportions de phases, tailles de grains, module élastique de la phase molle et propriétés électriques des phases
The range of fine wire products marketed by METALOR is based on silver, copper and palladium alloys with high electrical and mechanical performance, such as the NOVAE1 product which has a mechanical strength of 1.3 GPa and an electrical conductivity of 17 % IACS. The objective of this study is to understand the metallurgical mechanisms behind these characteristics and to take advantage of them in order to propose a new range of alloys with improved conductivity while maintaining high mechanical strength. The preliminary study carried out on the Cu-Pd binary system highlights the presence of the βCuPd phase below 600 °C, whose electrical conductivity is estimated at 30 % IACS. This phase is experimentally highlighted in the NOVAE1 fine wire and its formation is associated with an 8 % IACS increase in conductivity. It could therefore be a promising answer for the development of new alloys. Targeted experiments were carried out on seven grades of alloys developed and annealed for several months at 727 °C and 550 °C and then characterized by microprobe, XRD and SEM. These new data allow to refine the thermodynamic description of the Ag-Cu-Pd ternary system, in particular the miscibility gap, consisting of the two solid solutions cfc α1 and α2 and the extension of the βCuPd phase in the ternary system. The multi-scale characterization of the fine NOVAE1 wire highlights the complex, three-phase and nanostructured structure of the sample. These observations allow the development of phenomenological models of the mechanical and electrical properties of the wires by considering a matrix consisting of an Ag-rich α1 phase, associated with a soft phase in which are included hard phase domains rich in Cu and Pd, α2 and βCuPd. The wire characteristics are thus evaluated according to their chemical composition. This highlights the key parameters of the system: phase proportions, grain sizes, elastic modulus of the soft phase and electrical properties of the phases

The aim of this thesis is to evaluate ORC systems and technologies from an energy and economic perspective. ORC systems are a growing renewable electricity generation technology, but New Zealand has limited local skills and expertise for identifying ORC resource opportunities and subsequently developing suitable technologies at low cost. For this reason, this thesis researches ORC technology, resource types, and international development, with the aim to determine guidelines for how to cost-effectively develop ORC systems, and to make recommendations applicable to furthering their development within a New Zealand context. This thesis first uses two surveys, one of commercial ORC installations, and a second of economic evaluations of ORC systems in literature, to determine what resources and economic scenarios are supportive of commercial development. It is found that geothermal resources provide the largest share of ORC capacity, with biomass and waste-heat recovery (WHR) being developed more recently. The surveys also found that countries with high electricity prices or policy interventions have developed a wider range of resources using ORC systems. This thesis then undertakes an EROI evaluation of ORC electricity generation systems using a combination of top-down and process based methodologies. Various heat sources; geothermal, biomass, solar, and waste heat are evaluated in order to determine how the utilised resource can affect energy profitability. A wide range of EROIstnd values, from 3.4 – 22.7 are found, with solar resources offering the lowest EROIs, and geothermal systems the highest. Higher still EROI values are found to be obtainable with longer system lifetimes, especially for WHR systems. Specific engineering aspects of ORC design and technology such as high-side pressure, heat storage, modularity, superheating, pinch-point temperature difference, and turbine efficiency are evaluated in terms of economic performance, and a variety of general conclusions are made about each. It is found that total system thermo-economic optimisation may not lead to the highest possible EROI, depending on the objective function. Lastly, the effects of past and potential future changes to the markets and economies surrounding ORCs are explored, including the New Zealand electricity spot price, steel and aluminium prices, subsidies, and climate policy. Of the subsidy types explored, it is found that directly subsidising ORC system capital has the greatest effect on the economic performance of ORC systems, as measured by common metrics. In conclusion, this thesis finds that ORC systems have a limited applicability to New Zealand’s electricity market under current economic conditions outside of geothermal and off-grid generation, but changes to these conditions could potentially make their development more viable. The author recommends that favourable resources should be developed using systems that provide high efficiencies, beyond what might provide the best economic performance, in order to increase EROI, and reduce the future need for costly investments into increasingly less favourable resources.

Evaluation of the variability of theoretical and effective CO2 storage capacity estimation within depleted gas reservoirs is dependent on the integrated analysis of reservoir structure, aquifer performance and thermodynamic behaviour. Four published theoretical CO2 storage capacity methods and one effective method have been used to estimate the capacity and variability of two Triassic depletion drive reservoirs and two Triassic water drive reservoirs located within the UK Southern North Sea and East Irish Sea Basin. Input parameters to the storage capacity equations have shown a degree of natural variability whereas others are more accurately constrained. As such, attempts have been made to more accurately constrain the most variable input parameters. The geometric, petrophysical and production characteristics of the reservoirs are analysed. Material balance methods are used to assess the reservoir drive mechanism of the reservoirs. If reservoirs are found to experience a water drive, the aquifer strength is estimated. The gas compressibility factor, gas formation volume factor and CO2 density is estimated under initial reservoir temperature conditions using six equations of state for comparison of results. These results are then input to storage capacity equations producing a range of estimates. The most susceptible parameter to variability was the cumulative volume of water influx to a reservoir, We. Variability was also found to be the result of error in estimation of the original gas in place. As such, the water drive reservoirs made further use of aquifer modelling to achieve more precise estimates of OGIP and We. The effective capacity coefficients for the various reservoirs have been estimated to assess the proportion of pore space available for CO2 storage. The effective CO2 storage capacity constitutes a fraction of the theoretical CO2 storage capacity which ranges between 0 (no storage possible) and 1 (all theoretically accessible pore volume is occupied by CO2). Overall, it was found that depletion drive reservoirs have the potential to store greater volumes of CO2 than water drive reservoirs whose aquifer waters occupy the newly liberated pore space.

Différents secteurs industriels génèrent, par an, des milliers de tonnes de catalyseurs usés contenant jusqu'à 35% de métaux de valeur comme Co, Cr, Cu, Ni, Mo, Ti, V, W, etc. , sur des supports composés d'alumine, de silico-aluminate, de dioxyde de titane, etc. Ces solides contiennent souvent des impuretés comme C, S, Fe, Pb, P, etc. Le recyclage des éléments économiques de ces déchets pourrait contribuer à la protection de l'environnement. L’objet de ce travail est d'extraire sélectivement le cobalt, le nickel, le molybdène et le vanadium des catalyseurs usés d'hydrodésulfuration de pétrole et d'obtenir un résidu final inoffensif pour l'environnement. La caractérisation physico-chimique de 30 échantillons provenant de trois pays européens a permis de les classer en 4 groupes majeurs. Des échantillons représentatifs de ces groupes ont été utilisés au cours de ce travail. Le grillage préalable, pour l'élimination des impuretés, a été optimisé. Après une analyse thermodynamique, la cinétique de chloruration et de carbochloruration des composés purs, des éléments majeurs de ces catalyseurs usés, a été étudiée. Les résultats ont servi comme base pour aborder la chloruration et la carbochloruration des catalyseurs usés. La chloruration sélective de ces échantillons par différents mélanges gazeux a été obtenue grâce au contrôle de la pression partielle d'oxygène, du temps et de la température. Les meilleurs résultats ont été obtenus par la chloruration des échantillons non grillés en employant un mélange chlore-air à des températures inferieures à 600°C. Plus de 90% des métaux de valeur sont extraits. Ces résultats ont été confirmés à l'échelle semi-pilote. Le résidu final est composé essentiellement d'alumine ou de silico-aluminate. Un schéma de traitement est proposé

Ce mémoire de thèse présente une méthode de caractérisation des performances des ailettes d’échangeurs de chaleur automobiles basée sur le second principe de la thermodynamique. Dans le cadre de la mise en place d’une plateforme d’optimisation des surfaces d’échanges, l’approche proposée s’appuie sur des outils de modélisation numérique. L’étude est en particulier consacrée à la détermination du nombre de production d’entropie N s1 = ƒ (S gen) et à son évolution en fonction de paramètres clés du dimensionnement des ailettes d’échangeurs. Les termes du taux de production d’entropie S gen sont modélisés par une approche RANS. Une attention particulière est portée à la modélisation en proche paroi. Des lois de paroi spécifiques aux termes de production d’entropie sont introduites et discutées. A partir des champs locaux du taux de production d’entropie, le critère N s1 est déterminé. La méthode est tout d’abord appliquée à une configuration d’ailette munie de promoteurs de tourbillons longitudinaux. L’angle d’incidence des promoteurs et la conductivité de l’ailette sont modifiés afin d’étudier l’influence du transfert conjugué sur le taux production d’entropie. Dans un second temps des ailettes à persiennes sont étudiées. Les influences sur N s1 du point de fonctionnement, de la résistance de contact thermique tube-ailette, et de paramètres géométriques sont examinées. Cette étude révèle l’existence d’un optimum thermodynamique qui est fonction de ces différents paramètres. Le critère qui lie les irréversibilités visqueuses et thermiques met en lumière la compétition entre ces deux phénomènes antagonistes et permet de définir une limite caractérisant la prépondérance de l’un par rapport à l’autre
This thesis presents a methodology for the characterization of automotive finned tube heat exchanger performances, which is based on the second law of thermodynamics. In order to integrate this methodology as a part of an optimization platform of finned surfaces, the proposed approach is based on the numerical tools. The study is focused on the estimation of the entropy production number N s1 = ƒ (S gen) and on the evolution of this criterion with respects to the key parameters of the fin surface design. A RANS approach is used to calculate each term of the entropy production rate S gen. We focus our attention on the entropy production rate near the wall and specific near wall treatments for the entropy production terms are introduced and discussed. With all local information obtained, the entropy production criterion is calculated. The methodology is first applied to a finned tube with longitudinal vortices generators. The angle of attack of the vortices generators and the fin material are modified in order to study the influence of the conjugated heat transfer on the entropy production rate. As a second step, louvered fins are examined. The influences on N s1 of the operating point, of the thermal contact resistance between the tube and the fin, and of geometrical parameters are examined. This study reveals the existence of a thermodynamic optimum which depends on these parameters. The entropy production number that links the viscous and thermal dissipation terms shows a competition between two antagonist phenomena and permits to determine the boundary that characterize the predominance of the one with respect to the other

Actuellement, la plupart des fabricants de pompes à chaleur (PAC) fournissent les valeurs de coefficients de performances (COP) obtenus en laboratoire en conditions contrôlées et standardisées. Une méthode prometteuse, appelée méthode de mesure des performances dans la suite, d’évaluation des performances de PAC in situ, basée sur le bilan énergétique du compresseur, a été présentée par Tran et al. (2013). Cette méthode détermine le débit de fluide frigorigène et est compatible avec différents types de PAC, notamment air-air, et des cycles frigorifiques plus complexes.Tran et al. (2013) ont déterminé que l’incertitude sur l’évaluation de pertes thermiques du compresseur contribue à hauteur de 40% sur l’erreur d’estimation de la puissance thermique. L’objectif de cette thèse est d’établir une méthode simplifiée quant à l’instrumentation pour mesurer les pertes thermiques in situ. Pour cela, deux modèles numériques détaillés sont développés afin d’examiner la distribution de température sur l’enveloppe de deux types de compresseurs, scroll et rotary. Les mesures expérimentales fournies par un fabricant de compresseurs, Mitsubishi Heavy Industries (MHI), sont utilisées pour calibrer et valider les modèles numériques. Ces derniers permettent de définir deux protocoles de mesures différents pour les deux compresseurs. Ensuite, le protocole établi pour le compresseur rotary est intégré dans la méthode de mesures des performances. Les puissances thermiques calculées sont comparées avec des valeurs de référence, obtenues à partir d’un prototype en banc d’essai à EDF Lab Les Renardières
Currently, most heat pump(HP) manufacturers provide coefficient of performance (COP) values obtained in laboratories under standardized controlled operating conditions. These COP values are not necessarily representative of those obtained on-field. A promising method, referred to as the performance assessment method, that measures heat pump performances in-situ based on compressor energy balance, was presented by Tran et al. (2013). The method determines refrigerant mass flow rate and has the capability of measuring performances of various HP types, such as air-to-air, as well as more complex refrigeration cycles. The method abstains from intrusive measurements, and is, therefore, perfectly suitable for in-situ measurements.As shown in the work of Tran et al. (2013), compressor heat losses account for 40% in the final uncertainty of performance values obtained with the performance assessment method. The objective of this thesis is to establish a rather simplified measurement method, in terms of instrumentation, that is used to determine compressor heat losses in-situ. For this purpose two detailed numerical models for assessing the temperature fields of the scroll and rotary compressor shells were developed. Experimental measurements obtained with the help of compressor manufacturer, Mitsubishi Heavy Industries (MHI), are used to validate and calibrate the numerical models. The developed numerical models allow to define two different measurement protocols for both compressors. Established compressor heat loss protocol for rotary compressor is then integrated in the performance assessment method and the obtained heating capacities are compared with reference measurements in an experimental test bench in EDF Lab Les Renardières

Les problèmes environnementaux et économiques, engendrés par l’usage des produits pétroliers, et la pénurie de ces énergies fossiles ont conduit à rechercher d’autres sources d’énergies, renouvelables et respectueuses de l’environnement. Nombre de ces sources sont intermittentes et nécessitent de prévoir des solutions de stockage. Le gaz de dihydrogène apparait comme un bon candidat pour remplir cette fonction. L’élément hydrogène, abondant dans la nature, présente sous sa forme gazeuse un pouvoir calorifique de 140 MJ/kg, soit 2,5 fois celui de l’essence. La filière ’hydrogène’ s’appuie sur 3 piliers : la production, le stockage-la distribution et l’utilisation. Le stockage d’hydrogène est traditionnellement réalisé par compression, sous des pressions allant de quelques bars à plusieurs centaines, et par liquéfaction à 20 K. La faible densité volumique de ces deux types de stockage (42 et 70 kgH2/m3) associée à de sérieux problèmes de sécurité et de conception mécanique, rend le stockage solide dans les alliages métalliques particulièrement pertinent pour certaines applications. Cette solution favorise le développement de réservoirs de conception sûre, compacts et ayant une grande densité volumique de 120 kgH2/m3 pour les alliages TiFe par exemple. Ce type d’hydrure a été retenu dans le cadre de ce travail parce qu’il présente des températures et pressions d’utilisation relativement proches des conditions ambiantes, mais aussi parce qu’il ne contient pas de terre rare d’utilisation relativement proches des conditions ambiantes, mais aussi parce qu’il ne contient pas de terre rare. La présente étude vise à caractériser et modéliser le comportement d’hydruration/déshydruration de l’alliage TiFe0.9Mn0.1, en vue d’améliorer ses performances lorsqu’il est intégré à un système de stockage. Dans un premier temps, nous nous sommes attachés à caractériser expérimentalement l’alliage TiFe0.9Mn0.1 sous forme de poudre en le décrivant sur les plans morphologique, chimique et thermodynamique. Ensuite, deux stratégies d’amélioration ont été testées, la première repose sur un traitement mécanique par broyage planétaire à billes, la deuxième considère un traitement thermochimique à température et durée de maintien données. Ces deux stratégies ont permis d’accélérer le processus d’activation de la poudre, mais le broyage planétaire à billes a détérioré de façon notable la cinétique apparente de désorption. Le traitement thermochimique n’a quant à lui pas dégradé les domaines d’équilibre et n’a donc pas eu d’effet néfaste sur les cinétiques de réaction. Les deux paramètres les plus importants de ce traitement, température et temps de maintien, ont été optimisés. D’autres paramètres restent à affiner.[...]La conception d’un système de stockage solide d’hydrogène exige la bonne compréhension des aspects macroscopiques, mais aussi microscopiques, de la réaction d’hydruration, et requiert donc des recherches complémentaires pour trouver de nouveaux axes d’amélioration de ses performances
He environmental and economic problems caused by the use of petroleum products and the scarcity of these fossil fuels have led to the search for alternative sources of energy, which are renewable and respectful of the environment. Many of these sources are intermittent and require storage solutions. Hydrogen gas appears as a good candidate for this function. The hydrogen element, abundant in nature, has in its gaseous form a calorific value of 140 MJ / kg, i.e. 2.5 times that of gasoline. The 'hydrogen' sector is based on 3 pillars: production, storage, distribution and use. The storage of hydrogen is traditionally carried out by compression, under pressures ranging from a few bars to several hundreds, and by liquefaction at 20 K. The low density of these two types of storage (42 and 70 kgH2 / m3) associated with serious problems of safety and mechanical design, make solid storage in metal alloys particularly relevant for some applications. This solution favors the development of safe, compact design tanks with a high density of 120 kgH2/m3for TiFe alloys, for example. This type of hydride has been retained in this work because it has operating conditions of temperatures and pressures that are relatively close to ambient conditions, and also because it does not contain rare earth elements. The aim of this study is to characterize and model the hydriding/dehydriding behavior of the TiFe0.9Mn0.1 alloy, in order to improve its performance when it is integrated into a storage system. We first tried to characterize the alloy TiFe0.9Mn0.1 in powder form by describing it morphologically, chemically and thermodynamically. Then, two strategies of improvement were tested, the first one based on a mechanical treatment by planetary ball milling, the second considers a thermochemical treatment at given temperature and duration. Both strategies accelerated the process of powder activation, but the planetary ball milling significantly impaired the apparent desorption kinetics. The thermo-chemical treatment did not degrade the equilibrium domains and thus did not have an adverse effect on the reaction kinetics. The two most important parameters of this treatment, temperature and holding time, have been optimized. Other parameters remain to be refined.In addition to this experimental characterization, we have undertaken to describe the hydriding / dehydriding reaction macroscopically. The model allows to account for the thermodynamic response of the hydride within a reservoir. This work presents the results obtained on a tank containing 4 kg of TiFe0.9Mn0.1 powder when different hydrogen loading / unloading scenarios are considered: (i) loading / unloading under constant pressure, (ii) loading / unloading under an initial dose ( Method of Sievert), iii) loading / unloading under inlet or outlet flux of hydrogen. For each scenario, the effect of the coupling with a heat exchange system on the filling / emptying times is analyzed and optimal operating conditions are proposed. Finally, a sensitivity study using the Morris method is presented, and the most influential parameters of the model on the reaction rates are identified. The design of a solid hydrogen storage system requires a good understanding of the macroscopic as well as the microscopic aspects of the hydriding reaction and therefore requires further research to find new directions for improving its performance