Дисертації: "Thermo Mechanical system"

1

Olofsson, Joel. "Thermo-mechanical analysis of cryo-cooled electrode system in COMSOL." Thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-353895.

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In the planned linear accelerator called Compact Linear Collider, CLIC, electrons and positrons will be accelerated to velocities near the speed of light. A limiting factor in accelerating structures are vacuum breakdowns, which are electrical discharges from a surface as a result of a large electric field being applied. In the preparatory studies for the CLIC, Uppsala University in collaboration with The European Organization for Nuclear Research, CERN, is building a DC Spark system to analyze vacuum breakdowns. This system containing large planar electrodes will be cooled down all the way down to around 4 K in order to limit the rate of wich vacuum breakdowns happen. When cooling a system like this, which consists of different components made of different materials there is the question of how the system will be affected. The objective of this project is to investigate how the cooling will affect the stability in terms of stresses and to analyze the cool down time of the system. Another goal is to make a material recommendation for a few parts based on the results. This will be done by simulating the cooling in COMSOL Multiphysics, which is a program that uses finite element analysis to solve complex problems where different branches of physics interact. The conclusion is that the system will most likely be stable as it is and there is no need to redesign it. The choice of recommended material is alumina with the reason being it should cause the least stress and the smallest gap between the electrodes when the cooling is done. There was no big difference in the cool down time between the materials. Further studies and simulations on the system is also recommended since there are many factors not taken into consideration in this study.

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2

Elschich, Ahmed. "Thermo-mechanical Fatigue of Electrical Insulation System in Electrical machine." Thesis, Karlstads universitet, Avdelningen för maskin- och materialteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-62579.

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Electrical machines in electrified heavy-duty vehicles are subjected to dynamic temperature loadings during normal operation due to the different driving conditions. The Electrical Insulation System (EIS) in a stator winding is aged as an effect of these dynamic thermal loads. The thermal loads are usually high constant temperatures and thermal cycling. The high average constant thermal load is well-known in the electrical machine industry but little is known about the effect of temperature cycling. In this project, the ageing of the EIS in stator windings due to temperature cycling is examined. In this project, computational simulations of different simplified models that represent the electrical insulation system are made to analyse the thermo-mechanical stresses that is induced due to thermal cycling. Furthermore, a test object was designed and simulated to replicate the stress levels obtained from the simulations. The test object is to ease the physical testing of electrical insulation system. Testing a complete stator takes time and has the disadvantage of having a high mass, therefore a test object is designed and a test method is provided. The results from the finite element analysis indicate that the mechanical stresses induced will affect the lifetime of the electrical insulation system. A sensitivity study of several thermal cycling parameters was performed, the stator core length, the cycle rate and the temperature cycle amplitude. The results obtained indicate that the stator core length is too short to have a significant effect on the thermo-mechanical stresses induced. The results of the sensitivity study of the temperature cycle rate and the temperature cycle amplitude showed that these parameters increase the thermo-mechanical stresses induced. The results from the simulations of the test object is similar to the results from the simulations of the stator windings, which means that the tests object is valid for testing. The test method that is most appropriate is the power cycling test method, because it replicates the actual application of stator windings. The thermally induced stresses exposing the slot insulation exceeds the yield strength of the material, therefore plastic deformation may occur only after one thermal cycle. The other components in the stator are exposed to stresses below the yield strength. The thermally induced stresses exposing the slot insulation are high enough to low cycle fatigue the electrical insulation system, thus thermo-mechanical fatigue is an ageing factor of the electrical insulation system.

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3

Chang, Gary Carleton University Dissertation Engineering Systems and Computer. "System identification and control of a thermo-mechanical pulping refiner." Ottawa, 1995.

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4

Krishnan, Ganesh. "Thermo-mechanical reliability of ultra-thin low-loss system-on-package substrates." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26474.

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Thesis (M. S.)--Materials Science and Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Tummala, Rao; Committee Member: Pucha, Raghuram V.; Committee Member: Wong, C.P. Part of the SMARTech Electronic Thesis and Dissertation Collection.

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5

Christian, Corey D. (Corey Dwight). "Breaking the thermo-mechanical coupling of thermoelectric materials : determining the viability of a thermoelectric generator." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/121790.

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Thesis: S.M. in Engineering and Management, Massachusetts Institute of Technology, System Design and Management Program, 2019
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 69-70).
Thermoelectric power generators (TEGs) convert a temperature difference into electricity. This temperature difference can be created from waste heat. Since up to 50% [1] of US industrial energy input is lost as waste heat, an economical means of recovering waste heat and converting it into useful electricity could represent significant energy savings. Coupled with our integrative system design which involves creating application specific thermoelectric arrays, this technology can also help enable low power generation for off-grid needs in the developing world. Although conversion efficiencies as high as 20.9% [2] (heat to electrical energy) have been predicted from simulations of TEGs systems, in practice the efficiencies are typically only a few percent. Moreover, conventional systems often require expensive components to manage heat flow through the system.
As a result of the low efficiency and high system cost, electricity generated by thermoelectric energy harvesting from waste heat is currently not competitive with conventional electricity generation on a dollars-per-watt basis. This realization has led researchers to not only focus on increasing TEG device efficiency limits but to devise cheaper manufacturing processes and methods. A system design constraint that has not been fully investigated is the coupling of thermal and mechanical properties in thermoelectric materials. The extent to which this coupling affects the performance of the TEGs will be studied. This thesis develops an approach for decoupling the thermal and mechanical properties and tests it through a variety of simulations. We propose a mechanically compliant attachment strategy which could be integrated in various waste heat recovery applications.
The strategy involves breaking the thermal and mechanical bond formed by the brittle thermoelectric elements and its substrate. Copper wire, which is more pliable, is then used to connect the thermoelectric element to the substrate. A system analysis was performed for waste heat recovery from a vehicles exhaust pipe. We found that utilizing the proposed strategy should not only lead to increased mechanical compliance but can also lead to cost savings on a dollars-per-watt basis. We found that 84% power retention could be obtained when up to 16x less material is used under most apparent conditions¹.
by Corey D. Christian.
S.M. in Engineering and Management
S.M.inEngineeringandManagement Massachusetts Institute of Technology, System Design and Management Program

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6

Bitadze, Alexander. "Thermo-dynamical measurements for ATLAS Inner Detector (evaporative cooling system)." Thesis, University of Glasgow, 2014. http://theses.gla.ac.uk/5186/.

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During the construction, installation and initial operation of the Evaporative Cooling System for the ATLAS Inner Detector SCT Barrel Sub-detector, some performance characteristics were observed to be inconsistent with the original design specifications, therefore the assumptions made in the ATLAS Inner Detector TDR were revisited. The main concern arose because of unexpected pressure drops in the piping system from the end of the detector structure to the distribution racks. The author of this theses made a series of measurements of these pressure drops and the thermal behavior of SCT-Barrel cooling Stave. Tests were performed on the installed detector in the pit, and using a specially assembled full scale replica in the SR1 laboratory at CERN. This test setup has been used to perform extensive tests of the cooling performance of the system including measurements of pressure drops in different parts of system, studies of the thermal profile along the stave pipe for different running conditions / parameters and coolant flow measurements in the system. The pressure drops in the system and the associated temperatures in the barrel cooling loops have been studied as a function of the system variables, for example; input liquid pressure, vapour back pressure, module power load and input liquid temperature. Measurements were performed with 10, 11, 12, 13 barabs inlet liquid pressure in system, 1.2, 1.6, 2.0, 2.5, 3.0, 4.0, 5.0, 6.0 barabs vapour back pressure in system, and 0 W, 3 W, 6 W, 9 W, 10.5W power applied per silicon module. The measurements clearly show that the cooling system can not achieve the design evaporation temperature of -25C in every part of the detector (SCT Barrel loops) in case of 13 barabs nominal inlet liquid pressure, 1.2 barabs minimum possible back pressure and 6W nominal power per SCT Barrel silicon module and especially at the end of the ATLAS ID operation period when modules will work on full power of 10.5 W. This will lead to the problem of thermal run-away of the ATLAS SCT, especially near the end of the operational period after significant radiation exposure has occurred. The LHC luminosity profile, depletion voltage and leakage current values and the total power dissipated from the modules were revised. Thermal runaway limits for the ATLAS SCT sub-detector were also revised. Results show that coolants evaporation temperature necessary for the sub-detector's safe operation over the full lifetime (10 years) is -15C with a safety factor of 2. Laboratory measurements clearly show that the cooling system can not achieve even this necessary evaporation temperature of -15C. It is now impossible to make mechanical modifications to the cooling system, for example; changing the diameter of the cooling pipes, or the thermal performance of the in-system heat exchanger or reducing the vapour back pressure. It was therefore decided to investigate changes to the cooling fluid and to test mixtures of Hexafluoroethane (R116) C2F6 and Octafluoropropane(R218) C3F8 at differing ratios instead of just pure C3F8 coolant presently used. For this purpose, a new "blending" machine was assembled in the SR1 laboratory, with a new device an "on-line acoustic flow meter and fluorocarbon coolant mixture analyzer" (Sonar Analyzer) attached to it. The Machines were connected to the already existing laboratory test station and new extensive tests were performed to investigate different proportion of C3F8/C2F6 blends to find the mixture ratio which resulted in the best operational performance as measured by: the temperature distribution, pressure drops and flow parameters over the system, to ensure best cooling performance of SCT Barrel cooling loops for long term ATLAS SCT operation. Measurements were performed with different percentage of C2F6 (1%, 2%, 3%, 5%, 10%, 20%, 25%) coolant in the C3F8/C2F6 mixture, for different power (0 W, 3 W, 6 W, 9 W, 10.5W) applied to dummy modules on the SCT cooling stave, with 13 barabs inlet liquid pressure and for different vapour back pressures (1.2, 1.6, 2.0, 2.5, 3.0 barabs) in the system. Results prove that with 25% of C2F6 in the blend mixture, it is possible to lower the evaporation temperature by ~10C in the case of nominal operation parameters of the system. The ATLAS Inner Detector Evaporative Cooling System can therefore reach the necessary evaporation temperature and therefore can guarantee thermal stability of the SCT, even at the end of the operation period.

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7

Popov, Anton. "Three-dimensional thermo-mechanical modeling of deformation at plate boundaries : case study San Andreas Fault System." Phd thesis, Universität Potsdam, 2008. http://opus.kobv.de/ubp/volltexte/2009/3187/.

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It has always been enigmatic which processes control the accretion of the North American terranes towards the Pacific plate and the landward migration of the San Andreas plate boundary. One of the theories suggests that the Pacific plate first cools and captures the uprising mantle in the slab window, and then it causes the accretion of the continental crustal blocks. The alternative theory attributes the accretion to the capture of Farallon plate fragments (microplates) stalled in the ceased Farallon-North America subduction zone. Quantitative judgement between these two end-member concepts requires a 3D thermomechanical numerical modeling. However, the software tool required for such modeling is not available at present in the geodynamic modeling community. The major aim of the presented work is comprised basically of two interconnected tasks. The first task is the development and testing of the research Finite Element code with sufficiently advanced facilities to perform the three-dimensional geological time scale simulations of lithospheric deformation. The second task consists in the application of the developed tool to the Neogene deformations of the crust and the mantle along the San Andreas Fault System in Central and northern California. The geological time scale modeling of lithospheric deformation poses numerous conceptual and implementation challenges for the software tools. Among them is the necessity to handle the brittle-ductile transition within the single computational domain, adequately represent the rock rheology in a broad range of temperatures and stresses, and resolve the extreme deformations of the free surface and internal boundaries. In the framework of this thesis the new Finite Element code (SLIM3D) has been successfully developed and tested. This code includes a coupled thermo-mechanical treatment of deformation processes and allows for an elasto-visco-plastic rheology with diffusion, dislocation and Peierls creep mechanisms and Mohr-Coulomb plasticity. The code incorporates an Arbitrary Lagrangian Eulerian formulation with free surface and Winkler boundary conditions. The modeling technique developed is used to study the aspects influencing the Neogene lithospheric deformation in central and northern California. The model setup is focused on the interaction between three major tectonic elements in the region: the North America plate, the Pacific plate and the Gorda plate, which join together near the Mendocino Triple Junction. Among the modeled effects is the influence of asthenosphere upwelling in the opening slab window on the overlying North American plate. The models also incorporate the captured microplate remnants in the fossil Farallon subduction zone, simplified subducting Gorda slab, and prominent crustal heterogeneity such as the Salinian block. The results show that heating of the mantle roots beneath the older fault zones and the transpression related to fault stepping, altogether, render cooling in the slab window alone incapable to explain eastward migration of the plate boundary. From the viewpoint of the thermomechanical modeling, the results confirm the geological concept, which assumes that a series of microplate capture events has been the primary reason of the inland migration of the San Andreas plate boundary over the recent 20 Ma. The remnants of the Farallon slab, stalled in the fossil subduction zone, create much stronger heterogeneity in the mantle than the cooling of the uprising asthenosphere, providing the more efficient and direct way for transferring the North American terranes to Pacific plate. The models demonstrate that a high effective friction coefficient on major faults fails to predict the distinct zones of strain localization in the brittle crust. The magnitude of friction coefficient inferred from the modeling is about 0.075, which is far less than typical values 0.6 – 0.8 obtained by variety of borehole stress measurements and laboratory data. Therefore, the model results presented in this thesis provide additional independent constrain which supports the “weak-fault” hypothesis in the long-term ongoing debate over the strength of major faults in the SAFS.
Seit jeher rätselhaft sind die Prozesse, die die Akkretion der Nordamerikanischen Terranen in Richtung der Pazifischen Platte sowie die Wanderung der Plattengrenze der San-Andreas-Verwerfung in Richtung Festland bestimmen. Eine Theorie besagt, dass sich die Pazifische Platte erst abkühlt und den aufsteigenden Mantel im „Slab Window“ fängt und somit die Akkretion der kontinentalen Krustenblöcke bewirkt. Die andere Theorie geht von einer Akkretion durch das Fangen von Teilen der Farallon-Platte (Mikroplatten) aus, die in der inaktiven nordamerikanischen Farallon-Subduktionszone fest stecken. Die quantitative Beurteilung dieser beiden gegensätzlichen Konzepte erfordert eine thermomechanische numerische 3-D-Modellierung. Das dafür benötigte Software Tool steht jedoch der geodynamischen Modellierung derzeit noch nicht zur Verfügung. Das Hauptziel der vorliegenden Arbeit umfasst im Wesentlichen zwei miteinander verbundene Aufgaben. Die erste besteht in der Entwicklung und Erprobung des Finite-Element-Codes, dessen Eigenschaften den hohen Anforderungen an die Ausführung der dreidimensionalen Simulationen lithosphärischer Deformation auf geologischer Zeitskala gerecht werden müssen. Die zweite Aufgabe ist die Anwendung des entwickelten Tools auf die neogenen Deformationen der Kruste und des Mantels entlang der San-Andreas-Verwerfung in Zentral- und Nordkalifornien. Die Modellierung auf geologischer Zeitskala lithosphärischer Deformation bringt für die Software Tools in Bezug auf Konzept und Durchführung zahlreiche Herausforderungen mit sich. Unter anderem gilt es, den Brittle-Ductile-Übergang in einem einzigen Modell sowie die Gesteinsrheologie in einer breiten Spanne unterschiedlicher Temperaturen und Spannungen adäquat darzustellen und die extremen Deformationen der freien Oberfläche und internen Grenzen aufzulösen. Im Rahmen der vorliegenden Arbeit erfolgte die erfolgreiche Entwicklung und Erprobung des neuen Finite-Element-Codes (SLIM3D). Dieser Code beinhaltet eine gekoppelte thermomechanische Behandlung von Deformationsprozessen und ermöglicht eine elasto-visko-plastische Rheologie mit Diffusion, Dislokation, Peierls Kriechmechanismen und Mohr-Coulomb-Plastizität. Der Code verbindet eine Arbitrary Lagrangian-Eulerian kinematische Formulierung mit freien Oberflächen- und Winkler-Randbedingungen. Das entwickelte Modellierungsverfahren wird für die Untersuchung der Aspekte verwendet, die die neogene lithosphärische Deformation in Zentral- und Nordkalifornien beeinflussen. Die Modellanordnung konzentriert sich auf die Interaktion zwischen drei großen tektonischen Elementen in dieser Region: die Nordamerikanische Platte, die Pazifische Platte sowie die Gorda-Platte, die sich in der Mendocino-Triple-Junction treffen. Unter anderem verdeutlicht die Modellierung den Einfluss des Aufsteigens der Asthenosphäre in das sich öffnende „slab window“ der übergelagerten Nordamerikanischen Platte. Die Modelle beziehen auch die angelagerten Überreste der Mikroplatten in der fossilen Farallon-Subduktionszone, die vereinfachte subduzierende Gorda-Platte sowie markante Heterogenitäten der Kruste, wie beispielsweise den „Salinian Block“, mit ein. Die Ergebnisse zeigen, dass die Erwärmung der Mantellithosphäre unter den älteren Störungszonen sowie die Transpression eine Abkühlung im „Slab Window“ als alleinige Begründung für die Ostwärtsbewegung der Plattengrenze nicht zulassen. Aus Sicht der thermomechanischen Modellierung bestätigen die Ergebnisse das geologische Konzept, welches durch das mehrmalige Fangen von Mikroplatten den Hauptgrund für die Wanderung der Plattengrenze der San-Andreas-Verwerfung in Richtung Festland über die letzten 20 Millionen Jahre sieht. Die Überreste der Farallon-Platte, die in der fossilen Subduktionszone gefangen sind, verursachen im Mantel eine wesentlich stärkere Heterogenität als die Abkühlung der Asthenosphäre und stellen somit den effizienteren und direkteren Weg für die Anlagerung der nordamerikanischen Gebiete an die Pazifische Platte dar. Die Modelle demonstrieren, dass ein hoher effektiver Reibungskoeffizient an großen Störungen nicht in der Lage ist, die eindeutigen Zonen der Dehnungslokalisierung in der spröden Kruste vorherzusagen. Die Größe des Reibungskoeffizienten, die sich aus der Modellierung ableitet, beträgt etwa 0,075 und ist damit wesentlich kleiner als die durch unterschiedliche Bohrlochmessungen und Labordaten ermittelten Spannungswerte zwischen 0,6 und 0,8. Daher liefern die in dieser Arbeit präsentierten Ergebnisse der Modelle in der seit langem geführten Debatte über die Stärke von großen Störungen in der San-Andreas-Verwerfung eine zusätzliche unabhängige Begründung der „Weak-Fault“-Hypothese.

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8

Amin, Abdullah Al. "MULTISCALE MULTIPHYSICS THERMO-MECHANICAL MODELING OF AN MGB₂ BASED CONDUCTION COOLED MRI MAGNET SYSTEM." Case Western Reserve University School of Graduate Studies / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=case151385068164148.

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9

Ngaradoumbe, Nanhornguè Ronel. "Sensitivity analysis applied to fem models for coupled multiphase system." Doctoral thesis, Università degli studi di Padova, 2010. http://hdl.handle.net/11577/3421559.

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Coupled multiphysics problems are very actual research topics in civil engineering. In this work we focus on multiphase models for concrete exposed to high temperature, applicable to the evaluation of re resistance in industrial and civil concrete structures. Many non-linear phenomena and interactions are involved in concrete behaviour when temperatures higher than the standard ones are considered. Such phenomena involve not only heat conduction and vapour diffusion, but also liquid water ow caused by pressure gradients, capillary effects, adsorbed water content gradients, as well as latent heat transfer due to water phase change inside the pores. Moreover, high temperatures induce severe micro-structural changes and several interacting physical and chemical phenomena, resulting in signicant changes of the material inner structure and properties. During modelling of hygro-thermal-mechanical behaviour of concrete, one should use models considering possibly the whole complexity and mutual interactions of the analysed physical processes. The use of fully coupled multiphase models, based on mechanics of multiphase porous media, is therefore necessary to correctly predict the hygro, thermal, chemical and mechanical behaviour of this material, including damage effects. These models are nevertheless very complex and sophisticated because they are dealing with several elds strongly coupled, they are characterized by sets of coupled, nonlinear, differential equations and they require a large number of material parameters. Moreover, as it is well known, the computer solution of such large set of equations needs rather long computer times when applied to real life problems and can be therefore quite expensive. From this stems the necessity to reduce both the number of parameters to be determined accurately by experiments, and the computing time. Hence, a sensitivity analysis of the model with respect to variations of its parameters is needed, to be able to distinguish how sensitive is the solution to variations of the parameters of the equation set. Such an analysis reveals which are the main control parameters in the model and which are the effects of parameter changes, suggesting which parameters should be determined in an accurate way and which can simply be found from literature. The identication of parameters inuence should also allows to proceed to a simplication of the mathematical model (model reduction). The aim of this thesis is the sensitivity analysis of a nite element model (Comes-HTC) for the analysis of the behaviour of concrete exposed to high temperature; the sensitivity analysis has been performed with the automatic differentiation (AD) technique. The application of AD to the fem code Comes-HTC has allowed to develop an ecient tool for the computation of the sensitivity coecients, which has enabled to quantify the effect and relative importance of the material parameters with regards to the different model outputs. The results obtained allow for a better understanding of physical phenomena described by the Comes-HTC; they also highlight the full coupling between the hygral, thermal and mechanical eld that impacts on the link between model variables and material parameters.
I problemi che accoppiano vari campi della sica sono temi molto attuali nell'ambito dell'ingegneria civile. Il presente lavoro prende in esame modelli multifase per lo studio di calcestruzzi sottoposti ad alte temperature, applicabili per la valutazione della resistenza al fuoco di strutture civili o industriali. Numerosi fenomeni non lineari interessano il comportamento del calcestruzzo quando si considerano temperature elevate; tali fenomeni riguardano non solo la conduzione di calore e la diffusione di vapore, ma anche il trasferimento di calore latente provocato dal cambiamento di fase dell'acqua all'interno dei pori ed il usso d'acqua causato da gradienti di pressione, da effetti capillari, da gradienti del contenuto di acqua adsorbita. Inoltre le alte temperature causano forti cambiamenti microstrutturali e fanno sì che si sviluppino diversi fenomeni sici e chimici interagenti fra di loro, che provocano variazioni signicative della struttura interna e delle proprietà del materiale. Nella modellazione del comportamento igro-termo-meccanico del calcestruzzo, si dovrebbero utilizzare modelli che considerano la complessità e le interazioni dei processi sici descritti in precedenza. L'utilizzo di modelli accoppiati multifase, basati sulla meccanica dei mezzi porosi, si dimostra pertanto uno strumento necessario per una corretta previsione del comportamento igrometrico, termico, chimico e meccanico di tale materiale. Questi modelli sono tuttavia molto complessi e sosticati, perché hanno a che fare con parecchi campi fortemente accoppiati, sono caratterizzati da sistemi accoppiati di equazioni differenziali non lineari e richiedono un gran numero di parametri del materiale. Inoltre, nelle applicazioni di interesse pratico, la soluzione numerica di tali sistemi di equazioni richiede notevoli tempi di calcolo risultando quindi piuttosto costosa. Nasce quindi l'esigenza di ridurre sia l'onere richiesto dalla determinazione sperimentale dei parametri necessari, sia i tempi computazionali. Per poter procedere in questo senso serve quindi un'analisi della sensitività del modello rispetto alla variazione dei suoi parametri, per poter individuare in che modo la soluzione venga inuenzata dalla variazione dei parametri che compaiono nei sistemi di equazioni. Tale analisi rivela quali sono i parametri che controllano il modello e quali sono gli effetti delle loro variazioni, permettendo quindi di individuare i parametri la cui determinazione precisa è essenziale per l'accuratezza dei risultati e distinguerli da quelli la cui determinazione può essere meno precisa o che possono essere reperiti in letteratura. Dopo aver eseguito tale analisi, si potrà procedere ad una semplicazione del modello matematico, con effetti beneci anche sui tempi di calcolo, ed avviare in questo modo un processo di "model reduction". Lo scopo di questa tesi è l'analisi di sensitività di un modello agli elementi finiti (Comes-HTC) per l'analisi del comportamento del calcestruzzo esposto ad alte temperature; l'analisi di sensitività è stata eettuata attraverso la differenziazione automatica (AD). L'applicazione di questa tecnica al codice fem Comes-HTC ha permesso di sviluppare uno strumento eciente per il calcolo dei coecienti di sensitività, attraverso il quale è stato possibile quanticare gli effetti e l'importanza relativa dei parametri del materiale sull'insieme di soluzioni calcolate dal modello. I risultati ottenuti hanno consentito una migliore comprensione dei fenomeni sici descritti dal codice Comes-HTC, evidenziando anche il forte accoppiamento tra il campo igrometrico, termico e meccanico che inuisce sul legame tra le variabili del modello e i parametri del materiale.

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10

Ismail, Dahman, and Alexis Andrei. "Thermomechanical stress analysis of the main insulation system of traction electrical machines." Thesis, Blekinge Tekniska Högskola, Institutionen för maskinteknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-20305.

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More efficiency heavy-duty vehicles are developed with higher range, updated electronic and mechanical parts. The fuel efficiency and pollution of carbon dioxide need to be lower to achieve new EU regulations. The global population increases with an increased number of heavy-duty vehicles. This, in turn, increases the emission. By taking the electrical and mechanical parts to the next step, the global emission problems can be massively reduced. Electrical machines are the next step towards a cleaner future. The main goal of this study to investigate the electrical machine’s insulation system. Thermo-mechanical stresses due to thermal cycling affect the electrical machines and its sub-components. By using a FEM application with simplified models of the electrical machine, results are obtained and discussed. Specifically, if 2D-models are sufficient enough to represent a 3D-model. How good different 2D-models can represent the 3D-model is compared and discussed in this study. A physical experimental analysis is done to verify and calibrate the FE-models. Which one of the less frequent higher amplitude or more frequent, lower amplitude thermal cycling affects the insulation system most is determined. The simulations could be done with either, coupled-temperature displacement analysis or sequentially coupled analysis. Coupled-temperature displacement is the fastest method to use in the simulation models. A 3D-model is the best way to describe an object and is therefore implemented. Two additional 2D-models are developed for faster computation and to investigate if the models can represent the three-dimensional geometry. All the models have specific boundary conditions to make the models more simplified. Sensitivity studies have been done to determine which parameter affects the induced thermo-mechanical stresses the most. A physical experimental setup is also implemented to validate and calibrate the simulation model. The result of the 3D-model is most accurate when simulating a three-dimensional object. Simulation results have shown that epoxy, one of the main components in the insulation system, is most critical in terms of reaching breakdown first, followed by paper insulation and copper coating. This is a typical result of all three simulation models. Whereas it is concluded that some 2D-models can present the 3D-model, others can’t. The dependent factor is the different cross-section of the electrical machine. The physical experiment shows similar results between simulation in terms of strain at a lower temperature, and the deviation gets larger as the temperature increases. The 3D-model is the model that has the best representation of a real electrical machine as it accounts for all the normal and shear stress components in all directions, but also because it has better boundary conditions compared to the 2D-models. The 2D-model in XY-plane has shown similar results to the 3D-model. One of the main insulation system components, epoxy, is exposed to the highest stresses compared to its yield and ultimate strength, followed by the paper insulation and copper coating. The sensitivity study has concluded that the axial length of the stator does not affect the stress amplitudes. The most critical parameter that affects the thermo-mechanical stresses is the temperature amplitude, the materials CTE and the thickness of the jointed layer. All maximum stress amplitudes of all the components are located at the free end.
Mer effektiva tunga fordon utvecklas med högre räckvidd, uppdaterade elektroniska och mekaniska delar. Bränsleeffektiviteten och föroreningen av koldioxid måste vara lägre för att uppnå nya EU-förordningar. Antalet tunga fordon ökar i takt med att den globala befolkningen ökar, detta leder i sin tur till ökad utsläpp av bland annat koldioxid. Genom att ta de elektriska och mekaniska delarna till nästa steg kan de globala utsläppsproblemen minskas massivt. Elektriska maskiner för framdrivning är nästa steg mot en renare framtid. Studiens huvudmål för att undersöka den elektriska maskinens isoleringssystem. Termomekaniska påfrestningar på grund av termisk cykling påverkar de elektriska maskinerna och dess delkomponenter. Genom att använda en FEM-applikation med förenklade modeller av den elektriska maskinen erhålls och diskuteras resultat. Specifikt om 2D-modeller är tillräckliga för att representera en 3D-modell. Hur tillräckligt de olika 2D-modeller kan representera 3D-modellen jämförs och diskuteras i denna studie. Ett fysiskt experiment utförs för att validera och kalibrera FEA-modellerna. Vilken av de mindre frekventa cykler med högre amplitud eller mer frekventa cyckler med lägre amplitud påverkar isoleringssystemet mest har undersökts. Simuleringarna kan göras med antingen, temperatur kopplad förskjutnings analys eller sekventiellt kopplad analys. Temperatur kopplad kopplad förskjutning är den snabbaste metoden att använda i simuleringsmodellerna. En 3D-modell är det bästa sättet att beskriva ett objekt och har därför implementerats. Ytterligare två, 2Dmodeller är framtagna i FEM-miljö för snabbare beräkning och för att undersöka om 2D-modellerna kan representera den tredimensionella geometrin. Samtliga tre modeller har specifika randvillkor för att förenkla modellerna. Känslighetsstudier görs för att bestämma vilken parameter som påverkar de inducerade termomekaniska spänningarna mest. Ett fysiskt experiment har utförsts för att validera och kalibrera simuleringsmodellerna. Resultatet visar att 3D-modellen representerar ett tre dimensonellt objekt bäst. Simuleringsresultat har visat att epoxy, som är en av huvudkomponenterna i isoleringssystemet, är mest kritisk när det gäller att först nå brott- och sträckgräns, följt av pappersisolering och koppar beläggningen. Detta är ett typiskt resultat av alla tre simuleringsmodeller. Slutsatsen visar att vissa 2D-modeller kan presentera 3D-modellen, andra kan inte. Den beroende faktorn beror på ur vilket tvärsnitt man tittar på den elektriska maskinen. Det fysiska experimentet visar liknande resultat jämfört med simuleringen när det gäller belastning vid en lägre temperatur, och avvikelsen blir större när temperaturen ökar. 3D-modellen, är den modell som har den bästa representationen av en riktig elektrisk maskin eftersom den inkluderar normal- och skjuvspänningskomponenter i alla riktningar. Anledningen är att den har bättre randvillkor jämfört med 2Dmodellerna. 2D-modellen i XY-planet har visat liknande resultat som 3D-modellen. En av huvudkomponenterna i isoleringssystemet, epoxy, utsätts för de högsta spänningarna jämfört med dess sträck- och den brottgräns, följt av pappersisolering och koppar beläggning. Känslighetsstudien har kommit fram till att statorns axiella längd inte påverkar spänningsamplituderna. Den mest kritiska parametern som påverkar de termomekaniska spänningarna är temperatur amplituden, materialens CTE och tjockleken på det skarvade skiktet. Alla maximala spänningsamplituder för samtliga tre komponenter är belägna i den fria änden.

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11

CAIVANO, RICCARDO. "Design for Additive Manufacturing: Innovative topology optimisation algorithms to thrive additive manufacturing application." Doctoral thesis, Politecnico di Torino, 2022. http://hdl.handle.net/11583/2957748.

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12

Chen, Dongju. "Analysis and identification technology of system errors of large vertical ultra-precision machine tool." Compiègne, 2010. http://www.theses.fr/2010COMP1890.

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Анотація:

Dans plusieurs pays, les technologies d'usinage d'ultra-précision apportent une contribution importante au développement des sciences et des hautes technologies, principalement dans les domaines de l'optique, des microsystèmes et des ordinateurs avec des applications dans l'industrie des semi-conducteurs, du stockage de données, de l'aéronautique et de l'espace. L'usinage d'ultra-précision est entré dans le domaine de la nano-échelle et devient une dé nécessaire au développement des hautes technologies tant civiles que militaires. L'objectif de la recherche était de développer des méthodes de modélisation des axes mobiles d'une machine-outil d'ultra-précision, afin de prédire et identifier les erreurs de la machine et sa précision d'usinage. L'analyse des erreurs a été effectuée par la théorie multi-corps, la méthode des matrices de transfert et la méthode des éléments finis. La broche verticale sur paliers hydrostatiques a été modélisée. La raideur des paliers a été déduite des calculs de la portance par éléments finis et par une approximation analytique, en très bon accord. Le modèle mathématique de l'équilibre statique de la broche a permis d'évaluer la raideur sur tous les degrés de liberté, conduisant à la relation entre l'angle d'erreur de battement et le chargement. Les vibrations forcées de la broche générées par un défaut d'équilibrage pendant l'usinage ont été calculés par un modèle dynamique, dont on peut déduire la raideur dynamique et la réponse en fréquence. Un modèle thermomécanique de la broche intégrée à la machine a été établi, avec estimation des sources et des transferts de chaleur : l’influence des mécanismes de transfert sur l'erreur thermique a été analysée et l'impact sur la précision de la machine a été déduit. Un modèle d'erreur couplée des axes la machine sur guidages à paliers aérostatiques a été établi par la théorie multi-corps. La distribution de pression du film de gaz alimenté par une double rangée d'orifices a été obtenue par la théorie de la lubrification pour la structure complexe composée de guidages verticaux associés à des chariots d'équilibrage. Le modèle dynamique couplé du système de glissière a été établi et la réponse dynamique des guidages en fonction de la hauteur du film d'air a été déduite. Finalement, une méthode d’identification de l'erreur de mouvement de la machine à partir de la mesure d'une pièce usinée a été développée. Les mesures de la surface de la pièce usinée ont été traitées par transformation en ondelettes. L'erreur de rotation de la broche a été modélisée par une fonction de Weierstrass du temps. La corrélation entre les mesures géométriques des guidages, du système de broche et de la pièce permet d'en déduire l'influence de chaque source d'erreur sur la précision d'usinage. En combinant les analyses par ondelettes et densité spectrale, on peut également identifier les différentes erreurs dynamiques de la machine dans le domaine fréquentiel et la relation entre les ondulations de petite amplitude présentes dans la morphologie de la surface sur la précision de la machine
Ultra-precision machining technology is an important supporting technology of modern high-technology warfare, which is the development foundation for hightech industries and science and technology, and is the development direction of modern manufacturing science. The semiconductor device supported by ultraprecision machining technology, laid the foundation for the development of electronics and information industry. The development of modern science and technology based on the test, almost all of the test equipment needs the support of ultra-precision machining technology. Now ultra-precision machining has entered the nano-scale, and become an indispensable key means of developing high-tech. Whether the military industry, or civilian industry, all need such advanced machining technology. The research on machining precision of a two-axis large ultra-precision machine tool, analyzing the errors of main components of machine tool by multibody theory, the transfer matrix method, and finite element method. In order to show the comprehensive characterization of workpiece, wavelet method, correlation analysis and power spectral density method are used to analyze the surface topography of workpiece, different from the traditional Fourier transfer method, wavelet method express the comprehensive characterization of the signal in time and frequency domain. Correlation analysis method can estimate the signal in two different processes. Power spectral density method can fully reflect the impact of small-scale waviness of surface morphology on the machined accuracy. For the hydrostatic bearings, the parameters equation of bearings was deduced by the knowledge of fluid mechanics, and the calculated results were compared with other calculations. The mathematical model of spindle system in equilibrium was established according to Newton’s law, based on the the model, the relationship between derivation angle and stiffness of bearing was deduced, and the stiffness in all directions are given. The forced vibration of spindle caused by unbalance during machining process was researched through dynamic model of spindle. Dynamic stiffness and frequency response were deduced according to the axial static stiffness of spindle. Thermal-mechanical model of spindle system was established, the calculation basis of the heat transfer in the spindle system was deuced, and thermal error was analyzed with heat transfer mechanism, the variation of bearing performance at the different conditions under the influence of thermal errors, and the impact on the machining accuracy was analyzed. The coupling error model of guidewaies of machine tool was established with multi-body system theory. For the complex structure of guideway and unloading slide, the pressure distribution of gas film of guideway with double row orifices by gas lubrication theory, and corresponding load capacity and gas stiffness was obtained. The movement frequency with gas film thickness of entire slide system during machining process was showed. The coupling dynamic model of motion and unloading slides was established through corresponding frequency, the dynamic response of slide with the variation of gas film thickness was deduced. Finally, the variation of moving frequency in the whole gas film thickness was obtained. Finally, the measured result of workpiece was processed by wavelet transfer. The rotation error model of spindle was proposed by Weierstrass function, and the correctness and feasibility of this model was verified by comparing with actual test results. The correlation between guideway, spindle system and measured result of workpiece was analyzed, thus the degree of influence of every error on the machining accuracy was deduced. Combained with wavelet method and power spectral density method, the errors of guideway and spindle systems was analyzed in frequency domain, the characteristics of vibration signal of machine tool in frequency domain was extracted, and various error that affect the machining accuracy were identified according to the spectral characteristics

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13

Chen, J. P. "Thermo-mechanical behaviour of heavy-duty disc brake systems." Thesis, Cranfield University, 2001. http://dspace.lib.cranfield.ac.uk/handle/1826/10701.

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In heavy-duty disc brake systems, braking is a transient, non-linear and asymmetrical thermo-mechanical process. Surface cracking, rather than wear, is the major factor limiting the brake disc's life. The disc material (cast-iron), heat transfer boundary conditions and pad-disc frictional reactions are characteristically non-linear and asymmetrical during the friction process. Non-uniform deformation and surface cracks in brake discs result from the accumulation of excessive residual stress/strain. During braking processes, many factors affect the distributions of the residual stress and strain in discs, and hence the propagation of the surface cracks. The disc material, structure and boundary conditions are three of the crucial aspects. From the structure, a brake disc could be either solid or ventilated. In practice, solid structures always have higher anti-cracking performance than the same class of ventilated designs. However solid discs cost more material and have lower cooling efficiency. This thesis presents an improved finite element analysis for heavy-duty disc brakes and identifies design improvements. As the friction pads slide against the disc's surfaces continuously, the thermal and mechanical loads are functions of time and spatial coordinates. A 3-D asymmetrical finite element model was developed to achieve more accurate simulations of the thermo-mechanical behaviour of brake discs during braking processes. A non-linear inelastic material model for cast-iron was employed in the FE model. Permanent plastic stress and strain fields were predicted and analysed for multi-stop drag operations. The residual stress/strain fields in the discs are investigated to understand the differences between solid and ventilated discs in terms of the cracking resistance ability. Several engineering solutions are recommended for optimising the performance of the disc brake system. _ The thesis is organized in five chapters. Chapter One introduces the background concepts about the commercial disc brake system. In this part, the brake structure, material and previous researches are reviewed. The goals for this investigation are also summarised at the end of this chapter. Chapter Two introduces the general finite element modelling knowledge, procedures and the modelling boundary conditions and material models. Chapter Three presents an analysis of the disc brakes thermo-mechanical behaviour and the affecting factors. Chapter Four is focused on the residual stress field prediction and cracking behaviour analysis. The project conclusions and further research recommendations are presented in Chapter Five.

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14

Chen, Jing Ping. "Thermo-mechanical behaviour of heavy-duty disc brake systems." Thesis, Cranfield University, 2001. http://dspace.lib.cranfield.ac.uk/handle/1826/10701.

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Анотація:

In heavy-duty disc brake systems, braking is a transient, non-linear and asymmetrical thermo-mechanical process. Surface cracking, rather than wear, is the major factor limiting the brake disc's life. The disc material (cast-iron), heat transfer boundary conditions and pad-disc frictional reactions are characteristically non-linear and asymmetrical during the friction process. Non-uniform deformation and surface cracks in brake discs result from the accumulation of excessive residual stress/strain. During braking processes, many factors affect the distributions of the residual stress and strain in discs, and hence the propagation of the surface cracks. The disc material, structure and boundary conditions are three of the crucial aspects. From the structure, a brake disc could be either solid or ventilated. In practice, solid structures always have higher anti-cracking performance than the same class of ventilated designs. However solid discs cost more material and have lower cooling efficiency. This thesis presents an improved finite element analysis for heavy-duty disc brakes and identifies design improvements. As the friction pads slide against the disc's surfaces continuously, the thermal and mechanical loads are functions of time and spatial coordinates. A 3-D asymmetrical finite element model was developed to achieve more accurate simulations of the thermo-mechanical behaviour of brake discs during braking processes. A non-linear inelastic material model for cast-iron was employed in the FE model. Permanent plastic stress and strain fields were predicted and analysed for multi-stop drag operations. The residual stress/strain fields in the discs are investigated to understand the differences between solid and ventilated discs in terms of the cracking resistance ability. Several engineering solutions are recommended for optimising the performance of the disc brake system. _ The thesis is organized in five chapters. Chapter One introduces the background concepts about the commercial disc brake system. In this part, the brake structure, material and previous researches are reviewed. The goals for this investigation are also summarised at the end of this chapter. Chapter Two introduces the general finite element modelling knowledge, procedures and the modelling boundary conditions and material models. Chapter Three presents an analysis of the disc brakes thermo-mechanical behaviour and the affecting factors. Chapter Four is focused on the residual stress field prediction and cracking behaviour analysis. The project conclusions and further research recommendations are presented in Chapter Five.

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15

REGORDA, ALESSANDRO. "THE THERMO-MECHANICAL EVOLUTION OF THE SUBDUCTION-COLLISION SYSTEMS." Doctoral thesis, Università degli Studi di Milano, 2017. http://hdl.handle.net/2434/481243.

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The aim of this work was to develop a 2D thermo-mechanical model to analyse in detail the effects of the shear heating and mantle wedge hydration on the thermal state and dynamics of an ocean/continent subduction system. The thermal setting and dynamics that result from models with shear heating and/or mantle hydration are directly compared to a model that does not account for either (Marotta and Spalla, 2007) to analyse their effects on both the strain rate and the viscosity. The new model show the activation of short-wavelength mantle convection related to the hydration and the serpentinisation of the mantle wedge, with the consequent recycling of oceanic and continental subducted material. The effects of the subduction velocities on the size of the hydrated area are also analysed, and predictions of the pressure-temperature evolutions of crustal markers and the thermal field, which affect different portions of subduction systems, are used to infer the thermal regimes that affect the models. Similarly, the model can help to understand extensively both the distribution and the evolution, in time and space, of metamorphic conditions characterised by contrasting P/T ratios in subduction systems. In a second phase, P-T predicted by the model has been compared with natural P max -T estimates related to the Variscan metamorphism, from both the present domains of the Alps and from the French Central Massif. However, the model did not allow to compare simulated P-T paths with successive metamorphic stages recorded and preserved by the rocks during their metamorphic evolution, because of the lack of exhumation of subducted material up to the shallowest portion of the crust. Then, the model has been implemented by the introduction of the atmosphere and erosion-sedimentation mechanism, to verify that a free upper boundary could allow the rising of material up to the upper continental crust. The analysis of the simulated paths suggests the possibility to have two cycles of subduction and collision involved in the evolution of the Variscan belt. The hypothesis of two successive subduction systems is in agreement with geodynamics models proposed by many authors (e.g. Matte, 2001; Guillot et al., 2009; Lardeaux, 2014). On these results, a model characterised by two opposite subduction systems has been developed, to verify that it could represent a better evolutionary system for the reconstruction of the Variscan orogeny. Lastly, a comparison between the new model and P-T data of Variscan metamorphism has been performed.
La finalité de ce travail est de développer un modèle thermomécanique 2D pour analyser en détails les effets de la dissipation visqueuse et de l'hydratation du coin de manteau sur l’état thermique et la dynamique dans les zones de subduction. L’état thermique et la dynamique résultant des modèles prenant en compte la dissipation visqueuse et/ou l'hydratation du manteau sont comparés aux modèles le les prenant pas en compte (Marotta and Spalla, 2007), afin d’analyser leurs effets sur la viscosité et sur la vitesse de déformation. Notre nouveau modèle démontre l’activation de la convection du manteau à courte longueur d’onde en fonction de l'hydratation et de la serpentinisation du coin de manteau. Il en résulte un recyclage des croûtes continentales et océaniques subduites. En outre, les effets de la vitesse de subduction sur l’ampleur de la région hydratée ont été analysés. Les évolutions des conditions P-T des marqueurs de crustaux et l'état thermique enregistré dans les différentes portions du complexe de subduction sont utilisés pour avoir une meilleure compréhension de la distribution et de l'évolution, dans le temps et dans l'espace, de conditions métamorphiques caractérisées par des rapports P/T contrastés. Une fois ces modèles établis, les évolutions P-T prédites par les modèles sont comparées aux données métamorphiques naturelles observées dans la chaine varisque, plus particulièrement dans les Alpes et le Massif Central français. Afin de prendre en compte l’exhumation de croûte subduite jusqu’aux niveaux les plus superficiels, le modèle prends en compte le rôle de l'atmosphère et donc des mécanisme d’érosion et de sédimentation. Cette condition induit une limite supérieure libre qui permet à la croûte subduite d’ arriver à la surface. L'analyse des trajets simulés est compatible avec des scénarios impliquant deux cycles de subduction et de collision dans l'évolution orogénique de la chaîne varisque. L'hypothèse de deux subduction successives est en accord avec les modèles géodynamiques proposés par de nombreux auteurs (e.g., Matte 2001; Guillot et al., 2009; Lardeaux 2014). Sur la base de ces résultats, un modèle caractérisé par deux subductions opposées a été mis en œuvre à fin de mieux rendre compte de l'évolution thermo-mécanique de l'orogenèse varisque.

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16

Crain, Kevin Richard. "Mechanical characterization and thermal modeling of a MEMS thermal switch." Online access for everyone, 2005. http://www.dissertations.wsu.edu/Thesis/Fall2005/k%5Fcrain%5F120905.pdf.

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17

Paspuleti, Suma. "Mechanical and thermal buckling of thin films." Diss., Columbia, Mo. : University of Missouri-Columbia, 2005. http://hdl.handle.net/10355/4302.

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Thesis (M.S.)--University of Missouri-Columbia, 2005.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (July 14, 2006) Includes bibliographical references.

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18

De, Simone Silvia. "Induced seismicity in enhanced geothermal systems : assessment of thermo-hydro-mechanical effects." Doctoral thesis, Universitat Politècnica de Catalunya, 2017. http://hdl.handle.net/10803/405890.

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Micro-seismicity, and especially felt seismicity, induced by Enhanced Geothermal Systems (EGS) operations is a matter of scientific interest, not only because of the related risks and concerns, but also because the correspondence between injection and seismic activity still remains unclear. The Thesis aims to deepen the understanding of the involved Thermo-Hydro-Mechanical (THM) processes, in order to explain and manage co- and post-injection seismicity. First, we investigate the HM coupling and its effects on pressure response. Fluids injection exerts a force over the aquifer that causes deformation. This implies that Specific Storage, which reflects the capacity of permeable media to deform, cannot be treated as a single parameter, like in classical groundwater hydrology, because deformation also depends on aquifer geometry and on surrounding formations, which constrain displacements. We demonstrate the non-local nature of storage (i.e., its dependence on the poroelastic response over the whole aquifer) by means of analytical solutions to the transient pressure response to injection into one-dimensional and cylindrical finite aquifers, while acknowledging HM coupling. We find that the pressure response is faster and much greater than predicted with traditional solutions. Second, we consider non-isothermal injection and compare the effects of HM and TM couplings. We present analytical expressions for long-term hydraulic and thermal stresses and displacements for unidirectional and radial geometries. To obtain them, we assume steady-state fluid flow and develop an easy-to-use solution to the transient heat transport problem. The solution is then used to illustrate the poroelastic and thermoelastic response and, in particular, the sensitivity of stresses to the outer mechanical boundary conditions. Third, we perform coupled HM and THM simulations of cold water injection in a fault-intact rock system, which allows us to analyze mechanical stability changes during injection in the vicinity of the well. Simulation results show that temperature drop induces a significant perturbation of stresses in the intact rock near the injection well. This perturbation is likely to induce seismicity around critically oriented fractures. HM simulations show that fracture stability depends on the orientation of the faults and on the initial stress tensor. Results show that TM effects dominate and could induce seismicity, when the largest confining stress acts perpendicular to a fracture. Finally, we investigate the mechanisms that may induce seismicity after the end of fluid injection into a deep geothermal system (post-injection seismicity). Apart from the direct impact of fluid pressure increase, we acknowledge thermal effects due to cooling and stress redistribution caused by shear slip along favorably oriented fractures during injection. The effect of these three processes are analyzed both separately and superimposed. We find that post-injection seismicity may occur on unfavorably oriented faults that were originally stable. During injection, such faults become destabilized by thermal and shear slip stress changes, but remain static by the superposition of the stabilizing effect of pressure forces. However, these fractures become unstable and fail when the pressure forcing dissipates shortly after injection stops abruptly, which suggests that a slow reduction in injection rate may alleviate post-injection seismicity.
La micro-sismicitat induïda per operacions relacionades amb els Sistemes Geotèrmics Estimulats ha originat un gran interès científic, no només pel risc i la preocupació que comporta, sinó també perquè la relació entre la injecció de fluids i l'activitat sísmica no s'entén completament. Aquesta tesi pretén avançar en la comprensió dels processos hidro-termo-mecànics (THM) que causen aquesta sismicitat, per poder explicar-la i gestionar-la. En primer lloc, hem investigat l'acoblament hidro-mecànic (HM) i el seu efecte sobre les pressions. En Hidrologia Subterrània clàssica l'emmagatzematge especifico expressa la capacitat de l'aqüífer de deformar-se després d'una variació de pressió. Malgrat això, la sobrepressió generada per la injecció exerceix una força que deforma tot l'aqüífer, depenent de la seva geometria i de les formacions adjacents. Per això, l'emmagatzematge no es pot expressar amb un sol paràmetre, sinó que depèn de la resposta poro-elàstica de tot l'aqüífer, per la qual cosa diem que l'emmagatzematge específic és "no-local", cosa que vam mostrar mitjançant solucions analítiques de la resposta transitòria al problema HM de la injecció en aqüífers de dimensió finita, amb geometria tant unidimensional com cilíndrica. Seguidament, hem considerat una injecció no isoterma i comparat els efectes de l'acoblament hidro-mecànic (HM) i termo-mecànic (TM). Hem obtingut expressions analítiques per a les tensions i els desplaçaments induïts a llarg termini per la pertorbació hidràulica i tèrmica, en el cas de dominis unidireccional i radial. Per a això, hem considerat flux estacionari i desenvolupat una solució analítica senzilla per al transport de calor en règim transitori, la qual cosa ens ha permès calcular la resposta poro i termo-elàstica i en particular la sensibilitat de les tensions a les condicions mecàniques en el contorn exterior. A continuació, hem desenvolupat simulacions HM i THM acoblades de la injecció d'aigua freda en un sistema format per una falla embeguda en una roca intacta, a fi d'analitzar les variacions de l'estabilitat mecànica durant la injecció. Les simulacions HM mostren que l'estabilitat de les fractures depèn de la seva orientació i del tensor de tensions inicial. Concloem que la reducció de temperatura provoca prop del pou una forta pertorbació de les tensions, que pot induir sismes en fractures orientades críticament, especialment quan la tensió màxima actua perpendicularment a la fractura. Finalment, hem estudiat els mecanismes que poden induir sismes quan s'atura la injecció de fluids en sistemes geotèrmics profunds (sismicitat post-injecció). A més de l'efecte directe de l'augment de la pressió, hem considerat l'efecte tèrmic a causa del refredament i la redistribució de tensions generada pel moviment de cisalla que ocorre durant la injecció en fractures favorablement orientades. Aquests efectes s'han analitzat tant per separat com superposats. Dels resultats podem deduir que la sismicitat post-injecció pot ocórrer al llarg de fractures que eren inicialment estables i es desestabilitzen durant la injecció, a causa de les tensions tèrmiques i a les induïdes per la cisalla, però es mantenen estables gràcies a les forces de pressió. Posteriorment, aquestes fractures trenquen quan s'interromp la injecció, ja que les pressions es dissipen ràpidament. Això suggereix que la sismicitat post-injecció pot atenuar-se amb una reducció lenta del cabal d'injecció.

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19

Khadivipanah, Peiman. "Modelling thermo-mechanical response of metal canister disposed in engineered barrier systems." Doctoral thesis, Universitat Politècnica de Catalunya, 2022. http://hdl.handle.net/10803/673618.

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The main objective of this thesis is to describe and implement a rate-dependent (viscoplastic) constitutive equations for copper based canister using a single internal state variable and use it for modelling disposal schemes subjected to shear conditions. The model of Bodner and Partom (BP) is considered for this purpose (Bodner & Partom, 1975). To evaluate the copper's response to variations in strain rate throughout a temperature range, this model uses viscoplastic constitutive equations based on a single internal state variable that is a function of plastic work. The BP constitutive model has been implemented in CODE_BRIGHT computer code (DIT-UPC, 2021; Olivella et al., 1994; Olivella et al., 1996). The constitutive equation is verified against existing results and its validation is carried out by assessing the capability to reproduce experiments. For verification, the stress-strain response of a bar under uniaxial tensile conditions at a constant velocity was simulated with CODE_BRIGHT and the results compared with the solution obtained from Stealth Finite Difference Code and the semi-analytical solutions. In addition, it is analyzed the reaction of a canister installed inside an engineered barrier which undergoes hydration and swelling until it reaches full saturation prior to shearing. The implemented elasto-viscoplastic model actually represents the behavior of the canister in yielding conditions. Although the canister is very stiff and strong compared to the clay components where it will be emplaced in a clay volume shear deformations occurring on the engineered barrier system (EBS) will have an impact on the canister (Börgesson, 1986). Finally, a repository of nuclear spent fuel is analyzed under extreme conditions as it is a long-life system and has to resist all types of environmental conditions, for instance earthquakes and glaciations. After model implementation and verification in CODE BRIGHT this program has been used to model the canister-clay shear tests in 2D and 3D. In the Mock-up scale and Full-scale in 2D and 3D models, a comparison between the total stress method (mechanical analysis only) and the effective stress method (hydro-mechanical analysis) has been investigated. Experimental results from a canister-clay shear test (Börgesson, 1986) have been compared to the findings of the numerical model using CODE BRIGHT. Sensitivity analysis on viscosity for total stress calculations and permeability for effective stress calculations have been performed in the Mock-up scale and Full-scale. In the canister-clay shear test, a mesh sensitivity analysis and also a comparison between the updated mesh (Lagrangian method) and the fixed mesh method have been carried out. Finally, in two and three dimensions, the simulation of canister-clay shear tests based on impact of discontinuity (the discontinuity is in the rock and due to it, there is shearing in canister-rock system), as well as sensitivity analysis of parameters and mesh in mechanical and a coupled hydro-mechanical analysis, have been investigated.
El principal objetivo de esta tesis es describir e implementar una ecuación constitutiva dependiente de la velocidad (viscoplástica) para un contenedor a base de cobre usando una única variable de estado interna y usarlo para modelar esquemas de almacenamiento sujetos a condiciones de cizallamiento. Para ello se considera el modelo de Bodner y Partom (BP) (Bodner & Partom, 1975). Para evaluar la respuesta del cobre a las variaciones en la velocidad de deformación a lo largo de un rango de temperatura, este modelo utiliza ecuaciones constitutivas viscoplásticas basadas en una única variable de estado interno que es una función del trabajo plástico. El modelo constitutivo de BP se ha implementado en programa de ordenador CODE_BRIGHT (DIT-UPC, 2021; Olivella et al., 1994; Olivella et al., 1996). La ecuación constitutiva se verifica con los resultados existentes y su validación se lleva a cabo evaluando la capacidad para reproducir experimentos. Para la verificación, se simuló la respuesta tensión-deformación de una barra en condiciones de tracción uniaxial a velocidad constante con CODE_BRIGHT y se compararon los resultados con la solución obtenida de Stealth Finite Difference Code y las soluciones semi-analíticas. Además, se analiza la reacción de un contenedor instalado dentro de una barrera de ingeniería, que sufre hidratación e hinchazón hasta que alcanza la saturación completa antes del cizallamiento. El modelo elasto-viscoplástico implementado realmente representa el comportamiento del contenedor en condiciones de plastidad. Aunque el contenedor es muy rígido y resistente en comparación con los componentes de arcilla donde se colocará, las deformaciones por cizallamiento que ocurren en el sistema de barrera de ingeniería (EBS) tendrán un impacto en el contenedor (Börgesson, 1986). Por último, el contenedor de combustible nuclear gastado se podrá analizar en condiciones extremas, ya que es un sistema de larga duración y debe resistir todo tipo de condiciones ambientales, por ejemplo, terremotos y glaciaciones. Después de la implementación y verificación del modelo en CODE BRIGHT, este programa se ha utilizado para modelar las pruebas de cizallamiento en 2D y 3D. En la escala Mock-up y Full-scale en modelos 2D y 3D, se ha llevado a cabo una comparación entre el método de tensiones totales (solo análisis mecánico) y el método de tensiones efectivas (análisis hidromecánico). Los resultados experimentales de una prueba de cizallamiento canister en arcilla (Börgesson, 1986) se han comparado con los resultados del modelo numérico utilizando CODE BRIGHT. El análisis de sensibilidad sobre la viscosidad para los cálculos de tensión total y la permeabilidad para los cálculos de tensión efectiva se han realizado en la escala Mock-up y Full-scale. En la prueba de cizalla de contenedor-arcilla, se ha realizado un análisis de sensibilidad de la malla y también una comparación entre el método que actualiza la malla con los desplazamientos (método Lagrangiano) y el método de malla fija. Finalmente, en dos y tres dimensiones, se ha realizado la simulación de ensayos de cizallamiento contenedor-arcilla basados en el impacto de la presencia de una discontinuidad (la discontinuidad está en la roca y por ello hay cizallamiento en el sistema), así como análisis de sensibilidad de parámetros. y malla en análisis mecánico e hidromecánico acoplado
Enginyeria civil

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20

Aldubyan, Mohammad Hasan. "Thermo-Economic Study of Hybrid Photovoltaic-Thermal (PVT) Solar Collectors Combined with Borehole Thermal Energy Storage Systems." University of Dayton / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1493243575479443.

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21

Huang, Yi Ph D. Massachusetts Institute of Technology. "Spectral engineering for solar-thermal and thermal-radiative systems." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/127052.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, May, 2020
Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 224-239).
Increasing energy efficiency for power generation and reduction of energy consumption are two important venues to address the energy supply and global warming challenges we face today. Radiation from the sun and terrestrial heat sources can be harvested for power generation. It is also an important heat transfer channel, with which one can control in order to regulate the temperature of objects. In this thesis, we focus on strategies to harvest and control solar and thermal radiation, with the goals (1) to improve power generation efficiency using solar and thermal photovoltaics and (2) to reduce the energy consumption used to maintain human comfort in built environments. Solar radiation, as one of the most abundant energy sources on Earth, is now harvested by photovoltaics around the world. While solar photovoltaics already has reached considerable efficiencies, there is still room for improvement.
One fundamental limit in solar photovoltaics is the discard of photons with energy smaller than the material bandgap. Another challenge for solar PVs, due to the intermittent nature of solar power, is the lack of low-cost electricity storage systems that provide electricity on-demand. Solar thermal systems, on the other hand, can dispatch energy on-demand due to low-cost of thermal storage systems. Hybrid systems that combine solar PV and solar thermal systems can potentially harvest solar energy at higher efficiency and provide more dispatchable sources of energy. In the first part of my thesis, we designed and experimentally tested a spectral-selective, thermally-conductive component to be used in such hybrid solar-PV thermal system.
The component can direct part of the solar spectrum to the photovoltaics and to absorb the rest of the spectrum for use in a thermal system, thereby harvesting the entire solar spectrum with an energy conversion efficiency close to 23%, and with over 40% dispatchable electricity generated from thermal energy. The photovoltaic energy conversion efficiency can also improve by recycling photons with energy smaller than the material bandgap. In a thermo-photovoltaic system, low-energy photons can be designed to reflect back to the radiation source, and therefore energy carried by these photons can be re-used. Thermo-photovoltaic devices also showed great potential to provide low-cost, dispatachable electricity when combined with high-temperature thermal storage systems and concentrated solar power. In the second part of my thesis, we have designed and optimized a practical, crystalline-Si based thermo-photovoltaic cell to be fabricated on double-side polished wafers.
The Si-based TPV cell, combined with a 2300K gray radiator, can potentially reach 40% energy conversion efficiency. We have evaluated and optimized the Si-TPV performance with comprehensive considerations of components in the photovoltaic cell, including doping and junction depth, front and back surface field, passivation layer, back reflector, front metallization, as well as tolerance to roughness introduced in fabrication. Experimental tests have been conducted on doped Si samples with back reflectors, and identified potential pathways to further reduce optical and electrical losses. The maturity of the Si PV technologies and its relatively low cost points to great promise of high-efficiency thermo-photovoltaic devices for high-temperature thermal energy storage. Thermal radiation is also integral to the regulation of heat balance and temperatures of human body. Spaces in built environments are typically kept at near-ambient temperatures for human thermal comfort.
However, heating and cooling of spaces consume 40% of the total energy used in the US. Instead of regulating temperature in vast spaces, local regulation of heat near human bodies can potentially save large amounts of energy. In the third part of my thesis, we study the use of fabrics to regulate skin temperatures of the human body by controlling the input and output radiation channels of the human skin, an important yet largely under-studied channel for body temperature regulation. We then propose desired spectral properties of fabrics for both heating and cooling purposes, and in both indoor and outdoor environments. Finally, we investigate via both simulation and experiments, how morphology and material of polymer-based fabrics can be used to achieve the desired spectral properties.
by Yi Huang.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Mechanical Engineering

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22

McEuen, Scott Jacob. "Thermal analysis of biochemical systems." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/81702.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 109-112).
Scientists, both academic and industrial, develop two main types of drugs: 1) small molecule drugs, which are usually chemically synthesized and are taken orally and 2) large molecule, biotherapeutic, or protein-based drugs, which are often synthesized via ribosome transcription in bacteria cells and are injected. Historically, the majority of drug development, revenue, and products has come from small molecule drugs. However, recently biotherapeutic drugs have become more common due to their increased potency and specificity (the ability to chemically bond to the targeted protein of interest). Researchers now estimate that as much as 50% of current drug development activities (pre-market approval) are focused on these protein-based drugs. There are several well-documented steps necessary in the development of a new large molecule drug. One critical element during the end of the biotherapeutic drug discovery phase and the beginning of the manufacturing phase is known as preformulation or formulation development. During this stage scientists systematically test the effects of adding various excipients (non-protein additives added to enhance the protein stability, solubility, activity of the drug, etc.) to the potential large molecule drug. Differential scanning calorimetry (DSC) is a common technique used to perform these formulation studies. In a classic DSC experiment, a protein is heated from 20-80°C and the heat absorbed while the protein unfolds is measured. Many researchers prefer the use of a DSC instrument because of its label-free nature, meaning that no fluorescent or radio-labeled tag is necessary to perform the measurement. The heat absorbed during the unfolding event(s) is directly measured. However, current commercial DSC instruments suffer from high protein consumption (especially when compared to other labeled techniques), low sensitivity, and slow throughput. The aim of this thesis is to address two of the three areas mentioned above: high protein consumption and slow throughput. Since many formulation development studies are performed at therapeutic or high protein concentrations, one can reduce the experimental cell volume and thereby reduce the amount of protein material consumed. However, since there is less sample, less heat is produced. While in the literature there are several heat transfer models that describe how a DSC instrument literature there are several heat transfer models that describe how a DSC instrument functions, there are surprisingly few heat transfer models that detail how ambient temperature disturbances impact the thermal measurement. To better describe this behavior, a simplified state-space thermal model was created to predict the disturbance rejection of a custom DSC instrument. This model was verified experimentally using linear stochastic system identification techniques. To reduce sample throughput, the prototype calorimeter cell was made from disposable materials. Because the majority of protein systems are thermodynamically irreversible, at elevated temperatures the protein solution often aggregates and needs to be cleaned before a subsequent experiment can be run. This cleaning process constitutes a significant portion of the overall time to run an experiment. This thesis documents a fully functional DSC instrument that, while not completely disposable, has been designed, built, and tested with disposable microfluidic materials. Future work would then solve the technical hurdles of repeatably loading disposable microfluidic cells into the DSC instrument.
by Scott Jacob McEuen.
Ph.D.

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23

Barnat, Samed. "Etude prédictive de fiabilité de nouveaux concepts d’assemblage pour des « system-in-package » hétérogènes." Thesis, Bordeaux 1, 2011. http://www.theses.fr/2011BOR14243/document.

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Ce projet de thèse se situe dans le cadre de l'étude de la fiabilité prédictive de nouveaux concepts d'assemblages microélectroniques de type « system in package » SiP. L'objectif est de développer une méthodologie de fiabilité prédictive adaptée aux nouveaux concepts d'assemblage qui permet d'optimiser et de prédire les performances dès la phase de conception. Elle est ensuite appliquée sur des projets concrets. Cette méthodologie de fiabilité prédictive fait intervenir des études expérimentales, des simulations thermomécaniques et des analyses statistiques pour traiter les données et évaluer la fiabilité et les risques de défaillance. L'utilisation d'outils de simulation des composants électroniques est bien adaptée pour aider à l'évaluation des zones les plus fragiles, la mise en place des règles de conception et la détermination des paramètres les plus influents avec une réduction du temps de mise en marché d'un produit fiable et une optimisation des performances. Les études réalisées sur le silicium avec deux tests : bille sur anneau et test trois points montrent que le rodage et l'épaisseur ont une influence sur la variation de la contrainte et la déflexion du silicium à la rupture. Avec le test trois points, le déclenchement des fissures est lié à la qualité de sciage et de rodage. Cependant avec le test bille sur anneau, seule la qualité de surface influence le déclenchement des fissures. Le test bille sur anneau est bien adapté pour évaluer la qualité de surface du silicium. Avec les techniques chimiques de réduction de contraintes, comme la gravure humide et plasma, la résistance à la rupture a été considérablement améliorée. Ces tests de rupture sur le silicium ont permis de caractériser la rupture du silicium sous une contrainte de flexion et de compléter les résultats de simulation. Ces travaux démontrent, le besoin et l'utilité du prototypage virtuel des composants électroniques et de l'utilisation d'une méthodologie prédictive dans l'évaluation de la fiabilité en l’appliquant sur des composants réels
This thesis project is a study of the predictive reliability of new microelectronic package concepts such as "system in package" SiP. The objective is to develop a reliable predictive methodology adapted to the new assembly concepts to optimize and to predict the performance at the design phase. Then, the methodology is applied to concrete projects. This methodology of predictive reliability involves the use of experimental studies, thermomechanical simulations and statistical analysis to process the data and assess the reliability and risks of failure. The use of simulation tools for electronic components is well suited to assist in the evaluation of the most fragile areas, the setting up of design rules and the determination of the most influential parameters with a reduction in the setup time market for a reliable and optimized performance. Studies on silicon strength are conducted with two tests: ball on ring test and on three-point bend test show that the grinding and the thickness influence the variation of the stress and deflection of the silicon at break. With the three points bend test, the onset of crack is linked to defects in sawing and grinding zone. However, with the ball on ring test, only the surface quality influences the initiation of cracks. The ball on ring test is well suited for evaluating the quality of the silicon surface. Chemical techniques of stress release, such as wet etching and plasma etching, improve significantly the strength of silicon samples. These tests on silicon dies are used to characterize the breakdown of silicon under bending test and to complete the simulation results. We have demonstrated in this work, the need and the usefulness of the virtual prototyping of electronic components and the use of a predictive methodology in assessing reliability

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24

Ebinger, Cynthia Joan. "Thermal and mechanical development of the East African Rift System." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/53531.

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Thesis (Ph. D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), June 1988.
"May 1988."
Includes bibliographical references (p. 163-169).
The deep basins, uplifted flanks, and volcanoes of the Western and Kenya rift systems have developed along the western and eastern margins of the 1300 km-wide East African plateau. Structural patterns deduced from field, Landsat, and geophysical studies in the Western rift reveal a series of asymmetric basins bounded by approximately 100 kmlong segments of the border fault system. These basins are linked by oblique-slip and strike-slip faults cross-cutting the rift valley. Faults bounding the Kenya and Western rift valleys delineate two north-south-trending, 40-75 km wide zones of crustal extension, and little or no crustal thinning has occurred beneath the uplifted flanks or the central plateau. In the Western rift, volcanism in Late Miocene time began prior to or concurrent with basinal subsidence, followed by rift flank uplift. Individual extensional basins developed diachronously, and basinal propagation may give rise to the along-axis segmentation of the rift valley. The coherence between gravity and topography data indicates that the mechanical lithosphere beneath the two rift valleys has been weakened relative to the central plateau and adjacent cratonic regions. Gravity and topography data at wavelengths corresponding to the overcompensated East African plateau can be explained by density variations within the upper mantle that are dynamically maintained.
by Cynthia J. Ebinger.
Ph.D.

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25

Singh, Naveen Chandra Lall Pradeep. "Thermo-mechanical reliability models for life prediction of area array electronics in extreme environments." Auburn, Ala., 2006. http://repo.lib.auburn.edu/2006%20Spring/master's/SINGH_NAVEEN_54.pdf.

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26

Bracey, Marcus J. "Dynamic Modeling of Thermal Management System with Exergy Based Optimization." Wright State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=wright1503682474459341.

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27

Phan, Long N. 1976. "Automated rapid thermal imaging systems technology." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/75664.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 266-276).
A major source of energy savings occurs on the thermal envelop of buildings, which amounts to approximately 10% of annual energy usage in the United States. To pursue these savings, energy auditors use closed loop energy auditing processes that include infrared thermography inspection as an important tool to assess deficiencies and identify hot thermal gradients. This process is prohibitively expensive and time consuming. I propose fundamentally changing this approach by designing, developing, and deploying an Automated Rapid Thermal Imaging Systems Technology (ARTIST) which is capable of street level drive-by scanning in real-time. I am doing for thermal imaging what Google Earth did for visual imaging. I am mapping the world's temperature, window by window, house by house, street by street, city by city, and country by country. In doing so, I will be able to provide detailed information on where and how we are wasting energy, providing the information needed for sound economic and environmental energy policies and identifying what corrective measures can and should be taken. The fundamental contributions of this thesis relates to the ARTIST. This thesis will focus on the following topics: * Multi-camera synthetic aperture imaging system * 3D Radiometry * Non-radiometric infrared camera calibration techniques * Image enhancement algorithms - Hyper Resolution o Kinetic Super Resolution - Thermal Signature Identification - Low-Light Signal-to-Noise Enhancement using KSR
by Long N. Phan.
Ph.D.

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28

Siefert, Nicholas S. "Experimental and Thermo-Economic Analysis of Catalytic Gasification and Fuel Cell Power Systems." Research Showcase @ CMU, 2013. http://repository.cmu.edu/dissertations/255.

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This dissertation presents a comprehensive experimental and thermo-economic evaluation of coal gasifiers with in-situ carbon capture for generating high-hydrogen and high-methane content syngas for solid oxide fuel cell power plants. The goals of this thesis were the following: to conduct lab-scale experiments on catalytic coal gasification with in situ capture of acid gases, such as CO2 and H2S; to use the experimental results to model a commercial scale catalytic, in situ capture, coal/waste gasifiers; to integrates this gasifier with a solid oxide fuel cell (SOFC) system and to an build economic model to determine the internal rate of return on investment (IRR) of this system; then to compare the IRR of these power plant designs with other fossil fuel based power plant designs with CO2 capture and sequestration (CCS); and finally, to use the techniques/models developed here create an economic model of a SOFC fueled by an anaerobic digester. In this thesis, we estimate what range of economic parameters, such as SOFC stack capital cost, electricity sale price, and capacity factor, are required so that the systems analyzed can obtain unsubsidized, positive rates of returns on investment. The following are the highlights from each of the chapters. First, a molten catalytic process has been demonstrated for converting coal into a synthesis gas consisting of roughly 20% methane and 80% hydrogen using alkali hydroxides as both catalysts and in situ CO2 & H2S capture agents. Baselines studies were also conducted using no catalyst, a weak capture agents (CaSiO3) and strong in situ capture agents for acid gases (NaOH, KOH & CaO). Parametric studies were conducted to understand the effects of temperature, pressure, catalyst composition, steam flow rate and the coal-to-catalyst ratio on the performance of the catalytic gasifier in terms of kinetics and syngas composition. Second, we conducted multi-cycle studies in which CaCO3 was calcined by heating to 900oC to regenerate the CaO, which was then re-used in repeated CaO-CaCO3 cycles. We measured increased steam-coal gasification kinetics rates when using both CaO+KOH; these rates persisted even when the material was reused in six cycles of gasification and calcination. Third, we present an exergy and economic analysis of a power plant system that integrates a CaOlooping gasifier with a pressurized, solid oxide fuel cell (SOFC). We used the gas composition, steamcoal gasification rate and CO2 capture cycle degradation rate from the previous chapter as input into the model of this CaO-looping gasifier. We conducted an economic analysis of the system as a range of different operating pressures, current densities, fuel utilizations, and air stoichiometric ratios. We calculated an IRR of 6%/yr±4%/yr for the system when the sale price of electricity was $50/MWh if the CO2 could be used for enhanced oil recovery (EOR), where the uncertainty accounts only for an estimated uncertainty in the capital costs of +50%/-30%. We conducted a sensitivity analysis to determine the effect of changing some of the assumptions in our cost model, such as the price of the fuel cell stacks, the sale price of CO2, the sale price of electricity, the capacity factor, and the fuel price. Fourth, for comparison, we present exergy and economic analyses of two advanced coal-based power plants configurations in which the CO2 capture occurs outside of the gasifier. These cases are: an integrated gasification fuel cell cycle with a catalytic gasifier and a pressurized solid oxide fuel cell including CO2 sequestration (Adv. IGFC-CCS) and an integrated gasification combined cycle with advanced H2 and O2 membrane separation including CO2 sequestration (Adv. IGCC-CCS). Using the same economic assumptions, the IRR of the Adv. IGFC-CCS configuration was 4±3 %/yr if the CO2 can be used for EOR and 1±3 %/yr if the CO2 can only be sequestered in a saline aquifer. The IRR of the Adv. IGCC-CCS configuration with H2 and O2 membrane separation was 8±4 %/yr if the CO2 can be used for EOR and 3±3 %/yr if the CO2 must be sequestered in a saline aquifer. Fifth, we compare the IRR of these configurations with the IRR of other fossil fuel power plant configurations. For example, we present results showing which power plant configuration would yield the lowest levelized cost of electricity (LCOE) as a function of the price of CO2 emissions and a function of the price of natural gas, holding all other variables constant. Finally, we present an economic analysis of a configuration that uses biogas produced from an anaerobic digester (AD) to fuel a solid oxide fuel cell (SOFC) modeled based off of the pressurized SOFC we developed to the IGFC configurations presented earlier. We performed parametric studies of the AD-SOFC system in order to minimize the normalized capital cost ($/kW). The four independent variables were the current density, the stack pressure, the fuel utilization, and the total air stoichiometric ratio. Given our economic assumptions, our calculations show that adding a new AD-SOFC system to an existing wastewater treatment (WWT) plant could yield positives values of IRR (9%/yr ±4%/yr at $80/MWh electricity sale price), and could significantly outcompete other options for using biogas to generate electricity. AD-SOFC systems can convert WWT plants in net generators of electricity rather than net consumers of electricity while generating positives rates of return on investment, based on the assumptions of this analysis.

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29

Lambert, Adrien Pascal. "Thermal-mechanical analysis of system-level electronic packages for space applications." Thesis, Montana State University, 2012. http://etd.lib.montana.edu/etd/2012/lambert/LambertA1212.pdf.

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A position sensitive radiation sensor is being designed in conjunction with a field programmable gate array (FPGA) in order to further harden space flight computers against cosmic radiation. The system functionality is such that it requires a stack of PCB's that power and support the radiation sensor. The stacked architecture introduces limitations in terms of mechanical stability that must be addressed. Mechanical characterization of system electronics must be performed in order to ensure that a new system will not fail under normal operation. This is especially true for systems subjected to harsh environments such as space flight. System level packaging must be employed in order to prevent damaging these systems. Factors such as weight constraints, system architecture, mechanical, and thermal loading must be considered, especially in space applications. During development of the sensor, different test beds were employed in order to characterize the radiation sensor and it's supporting electronic systems. The most common preliminary tests are high altitude balloon tests which allow the sensor to experience cosmic radiation at high altitudes, consistent with space flight operations. Each balloon test has mechanical and thermal criteria that must be met in order to survive flight. These criteria include resistance to vibration loading, as well as the ability to maintain system operational temperatures inside a payload as it ascends through the atmosphere. Finite element analysis (FEA) was used to evaluate primary system architecture, system support structures, as well as the flight payload in order to determine if the system would survive preliminary, and future, testing. System level architecture and test payloads were designed using SolidWorks cad software. ANSYS FEA software was used to create thermal models which accurately simulated convective cooling through the atmosphere, and solar radiation loading on the exterior of the payload. Vibration models were performed in order to find the natural frequencies of the subsystem, as well as characterize the response to applied vibrations. Conclusions from each model show that the system will survive expected test loading at a wide range of vibration frequencies, and maintain a thermally stable environment in order to prevent damage to the internal electronic systems.

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30

Kelley, Leah C. (Leah Camille). "The design and control of a thermal management system for a photovoltaic reverse osmosis system." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/67620.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 86-90).
Reverse osmosis (RO) is a well-known process for desalinating seawater and brackish groundwater. Desalination is energy-intensive, so using photovoltaic (PV) panels to power the process is an attractive environmentally friendly concept, especially for community-scale systems. Increasing the system efficiency will lower the total cost of water produced, making the systems more economically competitive for a greater number of geographic locations. The thermal behaviors of PV panels and RO systems are complementary and can be exploited to improve photovoltaic reverse osmosis (PVRO) system efficiency. For a given level of solar radiation, a PV panel produces more electrical power at lower panel temperatures. For a given applied pressure, the flow of clean water across an RO membrane increases with increasing temperature. By using the RO feed water to cool the PV panels and warming the water in the process, more electrical power can be produced and higher flow rates of clean water across the RO membrane can be achieved, increasing total daily water production. The ability to cool the PV panels permits the use of low-cost, flat-plate concentrating mirrors, which further increase electrical power and clean water production. This thesis develops a thermal management system to improve the performance of a small-scale PVRO. Preliminary case studies show that the thermal exploitation concept is feasible and that a 50% increase in the total daily clean water production of a PVRO system is achievable, with an active thermal controller. A thermal controller is proposed that optimizes the PVRO system performance by minimizing the temperature of the solar panel and maximizing the temperature of the RO feed water. The control system uses a solar panel-mounted heat exchanger, circulator pump and servo valves to maximize water production while operating within the temperature limits of both the solar panel and the reverse osmosis membrane. Preliminary controller simulations show that it can successfully manage the temperatures of both the solar panel and RO feed water. The thermal management concept was experimentally validated on a small-scale, 300 L/day PVRO system. A 57% increase in clean water production was achieved using thermal management and solar concentrating mirrors, which agrees well with simulated performance predictions.
by Leah C. Kelley.
S.M.

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31

Thoms, Matthew W. "Adsorption at the nanoparticle interface for increased thermal capacity in solar thermal systems." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/74946.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 86-88).
In concentrated solar power (CSP) systems, high temperature heat transfer fluids (HTFs) are responsible for collecting energy from the sun at the solar receiver and transporting it to the turbine where steam is produced and electricity is generated. Unfortunately, many high temperature HTFs have poor thermal properties that inhibit this process, including specific heat capacities which are half that of water. In an effort to enhance the effective heat capacity of these high temperature HTFs and thus increase the efficiency of the CSP systems, adsorption energy at the liquid-solid interface was investigated as a mechanism for increased thermal capacity. Solid ceramic nanoparticles were dispersed in several molten salts at 1-2% by mass with diameters ranging from 5 nm to 15 nm to provide a significant available surface area for adsorption at the particle-molten salt interface. After successful nanofluid synthesis, differential scanning calorimetry (DSC) was used to measure anomalous deviations from the expected heat capacity and enthalpy of fusion values in the nanofluids. The variation in the sensible and latent heat values was determined to be dependent on the presence of sub-100 nm particles and attributed to a layer of salt that remains adsorbed to the surface of the nanoparticles after the bulk of the salt has melted. The adsorbed salt layer is expected to desorb at a higher temperature, providing an increased effective thermal capacity in the vicinity of this desorption temperature. A thermal analysis technique utilizing DSC was proposed to approximate the thickness of the adsorbed layer at the liquid-solid interface, a value that has previously only been obtained using simulation or transmission electron microscopy. More specifically, the adsorbed layer of LiNO3 on Al2O3 particles was determined to be 5.3-7.1 nm thick, similar to the 1-3 nm layers that have been observed in literature for simple, monatomic fluids. The results provide new insight into the nature of adsorption at the liquid-solid interface in more complex fluid and particle systems that can be harnessed for enhanced thermal capacity in HTFs.
by Matthew W. Thoms.
S.M.

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32

Hatzenbuehler, Mark A. "Modeling of jet vane heat-transfer characteristics and simulation of thermal response." Thesis, Monterey, California. Naval Postgraduate School, 1988. http://hdl.handle.net/10945/23314.

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Approved for public release; distribution is unlimited
The development of a dynamic computational model capable of predicting, with the requisite design certainty, the transient thermal response of jet vane thrust control systems has been undertaken. The modeling and simulation procedures utilized are based on the concept that the thermal processes associated with jet vane operation can be put into a transfer function form commonly found in the discipline of automatic controls. Well established system identification methods are employed to formulate and verify the relationships between the various gains and frequencies of the transfer function model and experimental data provided by Naval Weapons Center, China Lake.
http://archive.org/details/modelingofjetvan00hatz
Lieutenant, United States Navy

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33

Ghavam-Nasiri, Ali. "Thermo-Hydro-Mechanical Behaviour of Composite Geosynthetic Lining Systems under High Temperature and Low Pressure." Thesis, The University of Sydney, 2017. http://hdl.handle.net/2123/17782.

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Aim. Composite geosynthetic clay lining systems (CGCLS), a combination of high density polyethylene geomembranes and geosynthetic clay liners (GCLs), have been used in brine ponds to manage the large amount of waste water produced by coal seam gas extraction. Exposure to sunlight combined with the thermal properties of brine water can lead to temperatures of up to 85-95°C at the liner. The goal of the thesis is to investigate whether GCLs may desiccate in engineering applications with high temperatures and low overburden loads. Methodology. A multi-phase, thermo-hydro-elastic theory of soil behaviour is first adopted to the study of desiccation of GCLs. The theory has been implemented in a computer simulation environment (CODE_BRIGHT). Next, the dependence of the GCL’s soil-water chararcteristic curve (SWCC) on temperature and overburden load are characterised experimentally and new forms of the SWCC equations are developed. A set of column studies are conducted. The aims of the column studies are to assess whether desiccation of bentonite occurs and to generate experimental data that can be used to validate the above-mentioned theory. Findings. The new developed SWCCs perform well in predicting the effects of void ratio on SWCC based on the available data. A non-linear thermo-hydro-elastic theory is found to be capable of replicating the observed change in time of temperature and water contents in the subsoil with reasonable accuracy, even with minimal back-fitting of data and independent determination of material properties of both GCLs and subsoil. The thesis has established experimentally, for the first time, that GCLs in composite liners, subject to surface temperatures of 78°C and overburden loads of 20kPa, may experience high levels of desiccation cracking. The findings of this thesis call for caution in using the type of GCL studied here in applications in which they are exposed to temperatures higher than 60°C.

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34

Foley, Brian S. B. (Brian M. ). Massachusetts Institute of Technology. "Solar thermal collector system modeling and testing for novel solar cooker." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/92179.

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Анотація:

Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.
Cataloged from PDF version of thesis.
Includes bibliographical references (page 22).
Solar cookers are aimed at reducing pollution and desertification in the developing world. However, they are often disregarded as they do not give users the ability to cook after daylight hours. The Wilson solar cooker is a solar cooker designed to address this problem by converting solar energy and storing that energy as heat in the form of molten salt (lithium nitrate). This thesis involved research, modeling, and experimentation for the solar collection system of the cooker. This thesis looked at prior research on glazing, Fresnel lenses, and absorber surface treatments to identify and evaluate elements for use in the collection system. Borosilicate glass, with a thermal conductivity of 1.005 W/mK and a solar transmittance of 0.91, and flat black paint, with absorptivity 0.96 and emissivity 0.88 were identified as potential elements for use in first trials. Experimentation was performed on copper and aluminum samples with various surface treatments powered by various Fresnel lenses to evaluate the relative efficiency of these treatments. A novel treatment method, machining a conical hole into the sample, was found to improve efficiency on untreated samples, but inferior to flat black paint. Modeling predicted that the minimum collection area for an acrylic Fresnel lens off-number 1.2 was 0.60 m² for and 0.65 m² for the proposed collector without and with glazing, respectively. A recommendation of collection area 1 m² was proposed to account for unexpected losses due to manufacturing errors, positioning errors, and environmental variation. This thesis also analyzed a proposal for a novel solar collector, a polished aluminum cone. Modeling and efficiency testing showed the cone to be inadequate for the radiation collection needed for the solar cooker.
by Brian Foley.
S.B.

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35

Algareu, Abdulmaged Omer. "Development of reflective low concentrated photovoltaic/thermal system." Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7674/.

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This work aims to investigate the performance of a new design for CPV/T system using 3D flat sided (3D V-trough) concentrators named squared (SAC), Hexagonal (HAC), Octagonal (OAC) and Circular (CAC) inlet and exit Aperture concentrators, with an effective cooling facility that keeps PV temperature within the Normal operating range. Novel mathematical optical models were generated, to the HAC and OAC geometries and validated using OPTISORKS software, to calculate the geometrical concentration ratio (GCR) and actual concentration ratio (ACR) by the inlet aperture area (A_in) a function of aperture width (W_in) and number of reflections (n), and material reflectivity (p) and at any concentrator side angle (Ψ), consequently the optical performance. Results showed that the optimum concentrator side angels for GCR of 2, 4, 6, 8 and 10 are 35°, 30°, 20°, 20° and 15°, respectively for all investigated geometries. Also COMSOL Multiphysics software was used for thermal modelling. Optical, thermal and electrical investigation results highlight that the designed CPV/T system is beneficial enough and feasible to be used in generating electrical and thermal powers for domestic use, as one useful package of energy with high output compared with the flat PV modules which generate only electrical power.

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36

Sweetland, Matthew 1970. "Design of thermal control systems for testing of electronics." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/8927.

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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001.
Includes bibliographical references (p. 239-242).
In the electronic component manufacturing industry, most components are subjected to a full functional test before they are sold. Depending on the type of components, these functional tests may be performed at room temperature, at cold temperature, or at high temperature (-50C to 1600C) depending on the type of component and intended market. The thermal management of these components during testing forms two basic issues that need to be addressed. The first issue is the heating or cooling of devices to the desired temperature prior to being tested, and the second issue concerns temperature control during the actual functional test. This thesis covers the design, modeling and testing of two prototype systems. One system uses a low cost IR heating system to preheat bulk devices to a target temperature, prior to the actual functional test. Theory shows that the limits on temperature ramp rates are imposed by the device package configuration and carrier configuration. The results from the prototype system show that the IR heating chamber is an effective low cost, low volume system for uniformly heating a wide range of device and carrier types. The second prototype system uses high performance jet impingement coupled with laser heating to actively control the temperature of a high power density device during a functional test. Experimental results from the prototype system are presented and design guidelines for future systems are developed. The theory for temperature control is developed and the effects of package design and test sequence design on the temperature control limits are studied.
by Matthew Sweetland.
Ph.D.

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37

Rao, Sachit Srinivasa. "Sliding mode control in mechanical, electrical and thermal distributed processes." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1164817694.

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38

Choi, Joon Ho. "CoBi: Bio-Sensing Building Mechanical System Controls for Sustainably Enhancing Individual Thermal Comfort." Research Showcase @ CMU, 2010. http://repository.cmu.edu/dissertations/33.

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Current existing thermal control systems are operated based on thermal comfort models generated by regression formulas averaging the thermal responses over data collected during extensive experiments involving panels of human subjects. These models may not be appropriate for an individual whose physiological characteristics happen to be located outside of the main stream from the experimental sample of occupants. By necessity, existing automatic control systems disregard individual characteristics such as health, age, gender, body mass, etc., which may affect physiological responses. Thereby these systems have serious limitations in ensuring individual thermal satisfaction. While there have been many efforts to overcome the limitations of current technology and to improve individualized control, most of the attempts to make smart controllers for buildings have dealt primarily with optimizing mechanical building components to deliver uniform conditions, largely ignoring whether a generated thermal environment by building systems meet actual users’ comfort and satisfaction. Over-cooling and over-heating are common unnecessary results. Thermal control innovations for building mechanical systems are critically needed to demonstrate that meeting the physiological needs of occupants can actually save energy and improve environmental quality while enhancing user satisfaction. The thermoregulation of the human body has a biological mechanism, homeostasis, which enables it to maintain a stable and constant body temperature by changing physiological signals including skin temperatures and heart rate. These signal patterns have the potential to provide information about each individual’s current thermal sensation.The goal of this research is to establish an adaptive thermal comfort control driven by ongoing human physiological responses or bio-signals. Confirming the optimum driver of skin temperature, and location of sensors, the bio-sensing adaptive control logic is developed to support the optimum control of HVAC terminal units. The bio-sensing controllers offer major opportunities for office, healthcare and residential buildings, especially where environmental quality and control can be linked to productivity and health, and where energy savings are critical. The CoBi bio-sensing adaptive HVAC systems control research would substantially improve occupant comfort, health, and well-being while advancing environmental sustainability with energy savings, at a small first cost for existing or new buildings.

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39

DiBartolomeo, Franklin. "HIGH SPEED CONTINUOUS THERMAL CURING MICROFABRICATION SYSTEM." UKnowledge, 2011. http://uknowledge.uky.edu/gradschool_theses/105.

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Rapid creation of devices with microscale features is a vital step in the commercialization of a wide variety of technologies, such as microfluidics, fuel cells and self-healing materials. The current standard for creating many of these microstructured devices utilizes the inexpensive, flexible material poly-dimethylsiloxane (PDMS) to replicate microstructured molds. This process is inexpensive and fast for small batches of devices, but lacks scalability and the ability to produce large surface-area materials. The novel fabrication process presented in this paper uses a cylindrical mold with microscale surface patterns to cure liquid PDMS prepolymer into continuous microstructured films. Results show that this process can create continuous sheets of micropatterned devices at a rate of 1.9 in2/sec (~1200 mm2/sec), almost an order of magnitude faster than soft lithography, while still retaining submicron patterning accuracy.

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40

Moody, Seth S. "Development of Dynamic Thermal Performance Metrics For Eco-roof Systems." Thesis, Portland State University, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=1535587.

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In order to obtain credit for an eco-roof in building energy load calculations the steady state and time-varying thermal properties (thermal mass with evapotranspiration) must be fully understood. The following study presents results of experimentation and modeling in an effort to develop dynamic thermal mass performance metrics for eco-roof systems. The work is focused on understanding the thermal parameters (foliage & soil) of an eco-roof, further validation of the EnergyPlus Green Roof Module and development of a standardized metric for assessing the time-varying thermal benefits of eco-roof systems that can be applied across building types and climate zones.

Eco-roof foliage, soil and weather parameters were continuously collected at the Green Roof Integrated PhotoVoltaic (GRIPV) project from 01/20/2011 to 08/28/2011. The parameters were used to develop an EnergyPlus eco-roof validation model. The validated eco-roof model was then used to estimate the Dynamic Benefit for Massive System (DBMS) in 4 climate-locations: Portland Oregon, Chicago Illinois, Atlanta Georgia and Houston Texas.

GRIPV30 (GRIPV soil with 30% soil organic matter) was compared to 12 previously tested eco-roof soils. GRIPV30 reduced dry soil conductivity by 50%, increased field capacity by 21% and reduced dry soil mass per unit volume by 60%. GRIPV30 soil had low conductivity at all moisture contents and high heat capacity at moderate and high moisture content. The characteristics of the GRIPV30 soil make it a good choice for moisture retention and reduction of heat flux, improved thermal mass (heat storage) when integrating an eco-roof with a building.

Eco-roof model validation was performed with constant seasonal moisture driven soil properties and resulted in acceptable measured - modeled eco-roof temperature validation. LAI has a large impact on how the Green Roof Module calculates the eco-roof energy balance with a higher impact on daytime (measured - modeled) soil temperature differential and most significant during summer.

DBMS modeling found the mild climates of Atlanta Georgia and Houston Texas with eco-roof annual DBMS of 1.03, 3% performance improvement above the standard building, based on cooling, heating and fan energy consumption. The Chicago Illinois climate with severe winter and mild spring/summer/fall has an annual DBMS of 1.01. The moderate Portland Oregon climate has a below standard DBMS of 0.97.

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41

Lenert, Andrej. "Tuning energy transport in solar thermal systems using nanostructured materials." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/92164.

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Анотація:

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 137-146).
Solar thermal energy conversion can harness the entire solar spectrum and theoretically achieve very high efficiencies while interfacing with thermal storage or back-up systems for dispatchable power generation. Nanostructured materials allow us to tune the spectral properties and heat transfer behavior to enable such systems. However, under high temperature conditions, thermal management, system optimization and minimization of parasitic losses are necessary to achieve competitive solar power generation. This thesis seeks to achieve spectral control and thermal management through manipulation of nanostructured materials. First, this thesis presents the design and development of a nanophotonic solar thermophotovoltaic (STPV) that harnesses the full spectrum of the sun, in a solid-state and scalable way. Through device optimization and control over spectral properties at high temperatures (~1300 K), a device that is 3 times more efficient than previous STPVs is demonstrated. To achieve this result, a framework was developed to identify which parts of the spectrum are critical and to guide the design of nanostructured absorbers and emitters for STPVs. The work elucidated the relative importance of spectral properties depending on the operating regime and device geometry. Carbon nanotubes and a silicon/silicon dioxide photonic crystal were used to target critical properties in the high solar concentration regime; and two-dimensional metallic photonic crystals were used to target critical properties in the low solar concentration regime. A versatile experimental platform was developed to interchangeably test different STPV components without sacrificing experimental control. In addition to demonstrating significant improvements in STPV efficiency, an experimental procedure to quantify the energy conversion and loss mechanisms helped improve and validate STPV models. Using these validated models, this thesis presents a scaled-up device that can achieve 20% efficiencies in the near term. With potential integration of thermal-based storage, such a technology can supply power efficiently and on-demand, which will have significant implications for adoption of STPVs. Second, the thesis shifts focus away from solid-state systems to thermal-fluid systems. A new figure of merit was proposed to capture the thermal storage, heat transfer and pumping power requirements for a heat transfer fluid is a solar thermal system. Existing and emerging fluids were evaluated based on the new metric as well as practical issues. Finally, sub-micron phase change material (PCM) suspensions are investigated for simultaneous enhancement of local heat transfer and thermal storage capacity in solar thermal systems. A physical model was developed to explain the local heat transfer characteristics of a flowing PCM suspension undergoing melting. A mechanism for enhancement of heat transfer through.control over the distribution of PCM particles inside a channel was discovered and explained. Together, this thesis makes significant contributions towards improving our understanding of the role and the effective use of nanostructured materials in solar thermal systems.
by Andrej Lenert.
Ph. D.

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42

Lizarraga-García, Enrique. "Optimal operation and design of solar-thermal energy storage systems." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/74925.

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Анотація:

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 99-105).
The present thesis focuses on the optimal operation and design of solar-thermal energy storage systems. First, optimization of time-variable operation to maximize revenue through selling and purchasing electricity to/from the grid is presented for a thermal energy storage system. Time-variable electricity prices and electricity buy-back from the grid to re-charge the energy storage is considered. The concentrated solar power on demand (CSPonD) concept, in which a salt pond receives solar energy, stores thermal energy, and delivers thermal energy to the power cycle is considered. Electric heaters are added to the CSPonD concept, allowing for periods of electricity buy-back from the grid to re-charge the energy storage. System-level models are developed and optimization of the design and operation is performed with local solvers. Three main case studies are considered: the first case study investigates the optimization of time-variable operation without electrical heating under time-invariant electricity price; the second case study optimizes the operation under time-variant electricity price without electric heaters; the third case study optimizes the operation under time-variant electricity price allowing charging of the pond using the grid electricity. The first case study reflects the time-invariant tariff model, whereas the second and third case studies consider a time-of-use feed-in-tariff. Two hourly price profiles are considered in order to assess the influence of it on the optimal design and operation of the thermal energy storage. The first electricity profile consists of a price profile that fluctuates moderately, and the second price profile fluctuates highly, including negative prices. The results show significant increase in the revenue when adding electric heaters. Under the moderately fluctuating electricity price, the use of heaters increases the revenue significantly, compared to the same case with no electric heaters considered. Under the highly fluctuating electricity price, the use of heaters more than doubles the revenue, compared to the same case with no electric heaters considered. Also, the performance analysis of a regenerative thermal energy storage system with enhancement heat transfer structures is presented. In a regenerative thermal storage system, thermal energy is transferred from a hot heat transfer fluid to the storage unit core elements during charge, and from the core elements to the cold heat transfer fluid during discharge. Herein, concrete as the solid storage material, nitrate solar salt as the heat transfer fluid, and aluminum plates as the heat transfer structures is considered. The discharge process from uniform initial temperature is studied with different configurations (pure concrete and concrete enhanced by transfer structures), operation strategies (laminar versus turbulent flow regimes), and dimensions. Results show a significant decrease in the cost of the thermal energy storage system when heat transfer structures are added, as well as a better performance in terms of discharge efficiency and discharge time period. The amount of solar salt needed for this configuration is approximately one fourth that required for a nitrate two-tank system operating with the same temperature difference.
by Enrique Lizarraga-García.
S.M.

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43

Lee, Heon Ju 1977. "Thermal stability of nano-structured selective emitters for thermophotovoltaic systems." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/78173.

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Анотація:

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 97-103).
A fundamental challenge in solar-thermal-electrical energy conversion is the thermal stability of materials and devices at high operational temperatures. This study focuses on the thermal stability of tungsten selective emitters for thermophotovoltaic (TPV) systems which are anticipated to enhance the conversion efficiency. Selective emitters, 2-D photonic crystals, are periodic micro/nano-scale structures that are designed to affect the motion of photons at certain wavelengths. The structured patterns, however, lose their structural integrity at high temperatures, which disrupt the tight tolerances required for spectral control of the thermal emitters. Through analytical studies and experimental observations, the failure modes of tungsten 2-D photonic crystal are indentified. There were four major mechanisms of thermal degradation by which micro/nano-scale structures change their geometry when heated: grain growth and recrystallization, oxidation, surface diffusion, and evaporation. A novel idea of flat surface tungsten photonic crystal (FSTPC) was proposed and was validated by theoretical modeling and by experiments. Pre-annealing or using single crystalline tungsten will prevent the grain growth. A thin layer of diffusion barrier will prevent oxidation and/or evaporation and maintain the optical performance. By filling in the micro/nano-scale cavities with a damascened IR transparent ceramic, the surface of the emitter will have negligible second derivative of the curvature, and thus eliminates the surface diffusion even at high temperatures. Accelerated tests on silicon-based 2-D photonic crystal show that the micro/nano-scale structures on the silicon surface survive for at least 100 hours at 400 °C, homologous temperature of 0.4, which is equivalent temperature of 1200 °C for tungsten. Based on a scale-accelerated failure model, the life time of the Flat Surface Tungsten Photonic Crystal (FSTPC) is estimated to be at least 40 years at 800 °C.
by Heon Ju Lee.
Ph.D.

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44

Pfahnl, Andreas Carl. "Design of a thermal control system for an IC test-in-tray handler." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/41026.

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45

Graham, Matthew R. (Matthew Ryan) 1976. "Detection of DNA polymorphisms in thermal gradients via a scanning laser confocal system." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/89327.

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46

Dinh, Toan Khac. "Thermoresistive Effect for Advanced Thermal-Based Sensors." Thesis, Griffith University, 2017. http://hdl.handle.net/10072/365574.

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Thermoresistive effects in semiconductors (e.g. silicon) and metals (e.g. platinum) have been widely utilized to develop MEMS (Micro Electro-Mechanical Systems) thermal-based sensors. Thanks to their simplicity in design and implementation using conventional MEMS technologies, these sensors have been found in a wide range of applications, including temperature sensing, flow monitoring and acceleration measurement. However, their material cost, inflexibility, inadequate sensitivity and, especially, their lack of ability to work in harsh environments impede these devices in many applications, particularly where the temperature is high. Therefore, there is a strong demand for investigating the alternative materials with high thermosensitivity for niche thermal-based sensors. This research aims to theoretically and experimentally investigate thermoresistive effect in a group of semiconductors (e.g. silicon, silicon carbide and graphite) for niche and advanced thermal-based sensors such as high-temperature sensors, low-cost and highly sensitive thermoresistive sensors, and flexible/wearable sensors for healthcare applications.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Engineering
Science, Environment, Engineering and Technology
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47

Greenhut, Andrew David. "Modeling and analysis of hybrid geothermal-solar thermal energy conversion systems." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/58087.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, February 2010.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 116-118).
Innovative solar-geothermal hybrid energy conversion systems were developed for low enthalpy geothermal resources augmented with solar energy. The goal is to find cost-effective hybrid power cycles that take advantage of the potential synergies of solar thermal and geothermal resources. One aspect is to determine the hybrid configuration that yields the highest annualized electricity generation. The levelized cost of electricity (LCOE) is estimated using equipment costing rules of thumb developed from Aspen HTFS and Aspen ICARUS software and from other sources. Detailed models for the hybrid solar-geothermal system were developed using Aspen Plus and Aspen Dynamics. Turbine flexibility relative to vapor flow rate, temperature and pressure variations was analyzed. In one scenario, a parametric steady-state study was carried out to examine the performance over the range of conditions resulting from diurnal and seasonal variations. The results of the diurnal and seasonal parametric studies were grossly weighted to approximate a typical year in Nevada, and these results led to an estimate of the annualized electricity generation. In another scenario, a dynamic model was selected from possible "greenfield" hybrid systems and used to examine the transient performance for a typical January day and a typical July day in Nevada. The dynamic model approximates the thermal inertial of the heat exchangers and the working fluids in the exchangers, solar collectors, piping and storage tanks. The dynamic model is driven with forcing functions for solar input and ambient temperature to approximate the typical winter and summer days.
(cont.) In all cases, solar energy was found to come at a higher cost per kW capacity than geothermal when the cost of geothermal wells was not considered. However, including well costs had an effect of evening out the levelized cost of electricity. Model complexity increased as more solar heat was added to existing geothermal systems, which suggests that moving a higher exergy heat source down to a lower exergy heat source is difficult, especially given the transient nature of the solar resource. The models developed in this thesis demonstrate the design decisions and complex dynamic behavior inherent in this type of hybrid system.
by Andrew David Greenhut.
S.M.

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48

Meroueh, Laureen. "Electrically charged thermal energy storage systems for grid-level electricity storage." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/115660.

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Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 155-171).
Unlike most other commodities, electricity produced at any given time must match the electricity being consumed or the stability of the electric grid is jeopardized. Electricity demand changes throughout the day result in required generation ramp-ups that strain power plants, reduce cycle efficiency and increase CO2 emissions. This problem is exacerbated when renewable sources such as wind and solar are integrated into the grid, due to their intermittency. A change in methods of energy production globally that allows synergistic coupling of renewable and fossil fuels is needed. Currently, pumped hydroelectric and compressed air energy storage are the two most common methods of storage, but are highly geographic dependent systems and thus of limited applicability. There exists a strong demand for grid-scale energy storage that are cost-effective and without geographic constraints. In this thesis, storage systems that are charged by electricity and discharged to produce electricity at times of high demand, are theoretically evaluated. Various types of storage such as chemical, thermal, and mechanical, are reviewed to determine the most ideal method for grid-level energy storage. Thermal energy storage systems using phase change materials are most attractive on a cost and energy density basis. Two system designs are evaluated that can couple to both existing and future power plants since they are electrically charged, via joule heating for example, and later discharged to produce electricity using the plant's turbomachinery. Described within is a novel system in which silicon is used as the storage medium and energy release is predominantly through radiative heat transfer. Another design based on the eutectic alloy Al0.88 Si0.12 and other sensible energy storage materials is also evaluated. As an example, the energy storage systems are coupled to a power plant operating according to a supercritical Rankin cycle, and their performance is compared to that of a boiler. Additionally, system cost is compared to existing storage technologies. Although storing electricity as heat and back to electricity is thermodynamically unfavorable, we present an analysis to show that this approach can be cost competitive and provides a segue from fossil fuels to renewable energy.
by Laureen Meroueh.
S.M.

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49

Ajja, Rameshwar. "Numerical heat transfer analysis of carbon-based foams for use in thermal protection system." FIU Digital Commons, 2006. http://digitalcommons.fiu.edu/etd/1179.

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The applicability of carbon-based foams as an insulating or active cooling material in thermal protection systems (TPSs) of space vehicles is considered using a computer modeling. This study focuses on numerical investigation of the performance of carbon foams for use in TPSs of space vehicles. Two kinds of carbon foams are considered in this study. For active cooling, the carbon foam that has a thermal conductivity of 100 W/m-k is used and for the insulation, the carbon foam having a thermal conductivity of 0.225 W/m-k is used. A 3D geometry is employed to simulate coolant flow and heat transfer through carbon foam model. Gambit has been used to model the 3D geometry and the numerical simulation is carried out in FLUENT. Numerical results from this thesis suggests that the use of CFOAM and HTC carbon foams in TPS's may effectively protect the aluminum structure of the space shuttle during reentry of the space vehicle.

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50

Crane, Bryan Lee 1976. "DNA mutation detection via fluorescence imaging in a spatial thermal gradient, capillary electrophoresis system." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/88874.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001.
"February 2001."
Includes bibliographical references (leaves 122-126).
by Bryan Lee Crane.
S.M.

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