Дисертації з теми "Themal"
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1
McNeill, David William. "Semiconductor layer growth by rapid themal chemical vapour deposition." Thesis, Queen's University Belfast, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238986.
2
Newton, Mark K. "The initial perception of humidity." Thesis, University of Portsmouth, 2011. https://researchportal.port.ac.uk/portal/en/theses/the-initial-perception-of-humidity(5c072ca2-6291-450a-a7ac-32c9d6ec1cbc).html.
3
Stärk, Martin [Verfasser]. "Control of magnetic domains and domain walls by themal gradients / Martin Stärk." Konstanz : Bibliothek der Universität Konstanz, 2016. http://d-nb.info/1111565201/34.
4
Meek, Romney. "Synthesis and Characterization of Graphene-family Mesoporous Nanomaterials for Themal Energy Harvesting and Sensing Applications." TopSCHOLAR®, 2018. https://digitalcommons.wku.edu/theses/3090.
Анотація:
Graphene-family nanomaterials (GFNs) have attracted a great deal of attention both in academia and in industry for a range of applications relevant for homeland security. In this thesis, an array of graphene-based hybrid materials and aerogels are synthesized for use as novel thermo-electrochemical energy harvesters and for ascorbic acid biosensing devices. The graphene-family nanomaterials include graphene oxide-GO, thermally reduced GO-rGOth, nitrogenated functionalized graphene-NFG, graphene aerogel-GA, nitrogen-doped graphene aerogel-NGA, multi-walled carbon nanotube aerogel-MWCNT, single-walled carbon nanotube aerogel-SWCNT, graphene and nanotube combined ‘hybrid’ aerogels-Gr:(SW/MW)CNT of various ratios, along with multilayered nanostructured architectures such as gold (AuNP) and silver nanoparticles (AgNP) decorated NFG coated with a thin layer of polyaniline (PANi). Precursor aerogel materials were also analyzed to demonstrate the effect of mesoporous architectures and the interplay of various components in augmenting physical-chemical properties.
These precursors were combined through multiple deposition schemes including electrodeposition, hydrothermal synthesis, and freeze drying techniques. This project was developed in an effort to enhance electrochemical properties through modification of the morphology, surface and structural properties, making them more suitable for thermal energy harvesting and bio-sensing applications. Hydrothermal synthesis created chemical bridged interfaces, interconnectedness, and improved electrical conductivity besides increasing the surface area of mesoporous aerogels created by freeze-drying. This causes an increase in the number density of electrochemically active sites. The surface morphology, lattice vibrations, and electrochemical activity of the materials were investigated using electron microscopy, micro-Raman Spectroscopy, and electrochemical microscopy techniques [namely cyclic voltammetry (CV), alternating current electrochemical impedance spectroscopy (acEIS), amperometric techniques, and scanning electrochemical microscopy (SECM)]. For thermoelectric and thermoelectrochemical power measurements, a custom-designed set up was made for creating a temperature gradient across two legs of a thermocell and experiments were performed in various device configurations (a) symmetric and asymmetric, (b) single thermocells, and (c) multiple (“in-tandem”) thermocells. Interestingly, we observed changes in conducting behavior from Ohmic to semiconducting and polarity shifts from positive to negative or vice versa on introduction of the redox electrolyte solution. The parametric correlations (thermopower and resistivity or conductivity) are established and the results are discussed in terms of the polarity switching behavior observed for some of the aerogels combinations.
5
Nagy, Hamed A. "Effect of simulated welding themal cycles on the mechanical and corrosion properties of P/M stainless steels /." The Ohio State University, 1999. http://rave.ohiolink.edu/etdc/view?acc_num=osu1488187049541973.
6
Moraes, Thiago Finotti de. "Implementação de protótipo de resfriador termoelétrico por efeito Peltier aplicado a dispositivos semicondutores de potência." Universidade Federal de Uberlândia, 2014. https://repositorio.ufu.br/handle/123456789/14598.
Анотація:
Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorIn any electrical or electronic circuit, thermal energy is a quantity that is always present and generally must be considered in the specifications of any application. In many cases, the heat from the Joule effect, as well as from other internal and irreversible losses, represent the biggest share of maximum heat that a system can dissipate under normal operation. In Power Electronics, the study and application of semiconductor power switches are particularly important. Many solutions have been developed over the years aiming to mitigate electrical losses and heat built-up in semiconductor power switches. It is important to state that the current amount of research available to academics and the general public into thermal effects on semiconductor power switches is not as wide as that concerning the applications of those switches. It is remarkably reduced the amount of work concerning active cooling of semiconductor power switches and components, as well as concerning the behavior of semiconductor power switches and components under active cooling. Thus, there is a lack of studies aiming the investigation of the behavior of electric switches under different thermal loads. Because of this lack, this work is focused on a proposal of an equipment actively cools semiconductor power switches used in Power Electronics, particularly those usually found in switched mode power supplies. The main purpose of this work is to develop an equipment for being used on a lab bench based on Peltier technology that sets thermal action on semiconductor power switches, making possible the evaluation of the behavior of these switches under different thermal exposures and temperatures. Fist, the Peltier technology was investigated and, later on, a solution was developed allowing the usage of this technology on semiconductor power switches. A detailed description and the calculations of the developed thermoelectric system are presented. The results of this work are presented as a comparative study of the behavior and limits of performance of MOSFETs in DC-DC Boost converters under active cooling compared to traditional passive heat sinks. During active cooling the MOSFET was cooled below ambient temperature, assuring its external thermal safety. The experimental results confirm the operation as intended. The main confirmed advantages were greater dissipated power, increase of thermal margin and capacity of actively transferring heat to an overloaded area to another place.
Em qualquer circuito elétrico ou eletrônico, a energia térmica é uma grandeza que está sempre presente e em geral deve ser levada em conta nas especificações de qualquer aplicação. Em vários casos, o calor decorrente do efeito joule, bem como de outras perdas internas e irreversíveis, representam a parcela mais impactante da quantidade de calor limítrofe que um sistema consegue dissipar em operação normal. São de particular importância em Eletrônica de Potência o estudo e a aplicação de chaves semicondutoras. Várias soluções têm sido desenvolvidas ao longo dos anos no sentido de mitigar as perdas elétricas em chaves semicondutoras, bem como o aumento de temperatura nas mesmas durante operação. É importante frisar que atualmente a quantidade de pesquisas disponíveis ao público acadêmico e geral sobre os efeitos térmicos em chaves semicondutoras não é tão ampla quanto sobre as aplicações dessas chaves. É particularmente reduzida a quantidade de trabalhos ligados ao resfriamento ativo de chaves e componentes elétricos, assim como de trabalhos voltados ao comportamento de chaves e componentes mediante resfriamento ativo. Sendo assim, existe uma carência de estudos que objetivem a investigação do comportamento de chaves semicondutoras mediante distintas cargas térmicas. Diante desta carência, o foco deste trabalho é apresentar uma proposta de equipamento que atue termicamente, seja aquecendo ou resfriando, sobre chaves semicondutoras utilizadas em eletrônica de potência, particularmente aquelas comumente usadas em fontes elétricas chaveadas. O objetivo principal deste trabalho é desenvolver um equipamento para uso em bancada baseado na tecnologia Peltier que resfrie ativamente chaves semicondutoras, possibilitando a avaliação de comportamento das mesmas mediante diferente exposições térmicas e temperaturas. Primeiramente a tecnologia Peltier foi investigada e, posteriormente, foi desenvolvida uma solução que permite a utilização desta tecnologia em dispositivos semicondutores de distintos encapsulamentos. Uma descrição detalhada e os cálculos de dimensionamento do sistema termoelétrico desenvolvido são apresentados. Os resultados deste trabalho são apresentados em forma de estudo comparativo sobre o comportamento e limites de desempenho de MOSFETs em conversores CC-CC Boost mediante resfriamento ativo frente aos tradicionais dissipadores passivos. Durante resfriamento ativo o MOSFET foi resfriado à temperatura subambiente e constante, garantindo sua a segurança térmica relacionada à temperatura do encapsulamento. Os resultados experimentais confirmam a operação do protótipo conforme a proposta deste trabalho. As principais vantagens confirmadas foram maior potência dissipada, aumento da margem térmica e capacidade de transferir ativamente calor de uma área sobrecarregada para outro local.
Mestre em Ciências
7
Sonar, Shilpa. "Abatement of toluene through storage-regeneration sequential process : application of thermal and plasma assisted catalytic regeneration." Thesis, Université de Lille (2018-2021), 2021. https://pepite-depot.univ-lille.fr/ToutIDP/EDSMRE/2021/2021LILUR064.pdf.
Анотація:
Le toluène est un composé organique volatil (COV) toxique présent dans les environnements intérieurs et extérieurs. La dépollution du toluène se fait généralement par adsorption ou oxydation catalytique. Dans ce dernier cas, le toluène est converti en CO2 et H2O, mais des espèces toxiques peuvent s'accumuler sur les catalyseurs, provoquant leur empoisonnement, leur désactivation et leur frittage. Pour surmonter ces inconvénients, nous proposons des procédés hybrides innovants de "stockage-régénération". Il s’agit de procédés séquentiels basés l’adsorption suivie de l'oxydation catalytique activée soit thermiquement (ATC) ou par un plasma (APC). Ces procédés sont divisés en deux étapes : "L'étape de stockage où le toluène gazeux est adsorbé sur la surface du matériau et l'étape d'oxydation où le toluène adsorbé est converti catalytiquement en CO2 et H2O dans un environnement thermique ou plasma. Le processus ATC a été testé sur de l'hopcalite commerciale (CuMnOx), de la Cérine-NR et de l'UiO-66-SO3H. L'hopcalite se distingue des autres par sa grande capacité d'adsorption "utile" et ses propriétés redox, permettant une activité et une sélectivité en CO2 élevées dans l'oxydation du toluène. Dans le procédé APC, la morphologie de la poudre et le manque d'effet de synergie dans la Cérine-NR et l'UiO-66-SO3H ne permettent pas de générer un plasma stable. Ainsi, seule l'Hopcalite a été étudiée de manière approfondie en APC. Il est observé que l'activité d'oxydation du toluène adsorbé est significativement affectée par les variables du procédé. La stabilité du matériau a été étudiée dans les deux cas au moyen de différentes techniques de caractérisation et il a été confirmé que les matériaux Hopcalite sont très stables. L'activité catalytique a été améliorée par l'imprégnation d'une phase active telle que l'argent, ce qui a conduit à une augmentation de la sélectivité et du rendement en CO2 avec une charge d'argent très faible, tant dans l'ATC que dans l'APC. Un examen approfondi du matériau a révélé qu'un bon équilibre entre la capacité d'adsorption et l'activité catalytique (Cu2+,3+ et Mn3+,4+) est nécessaire. De plus, le coût énergétique de l'APC se situe dans une fourchette acceptable (11.6 kWh-m-3), ce qui signifie qu'avec une optimisation supplémentaire des différents paramètres expérimentaux, il peut être facilement mis à l'échelle de manière rentable. L'ATC et l'APC permettent tous deux d'atteindre une efficacité de réduction du toluène et de conversion en CO2 supérieure à 95 % au premier passage et à 75 % pour les matériaux stabilisés. Ces résultats montrent que les deux procédés ATC et APC pourraient être des procédés prometteurs de réduction du toluène, efficaces sur le plan énergétique, et ouvrent la voie à de nouveaux développements et à une mise à l'échelleToluene is a toxic volatile organic compound (VOC) present in indoor and outdoor environments. The abatement of toluene is typically done by adsorption or catalytic oxidation. In the latter case, toluene is converted into CO2 and H2O, but toxic species can build up on catalysts, causing poisoning, deactivation, and sintering. To overcome these drawbacks, we propose innovative “storage-regeneration” hybrid processes based on sequential adsorption-thermal catalytic oxidation (ATC) and sequential adsorption-plasma catalysis (APC). These processes are divided into two steps: “storage step” where gaseous toluene adsorbed on the surface of material and “oxidation step” where the adsorbed toluene species is catalytically converted into CO2 and H2O in thermal or plasma environment. ATC process was tested on commercial Hopcalite (CuMnOx), Ceria-NR and UiO-66-SO3H. Hopcalite stands out from others owing to its high “useful” adsorption capacity and redox properties, allowing a high activity and CO2 selectivity in toluene oxidation. In APC process, the powder morphology and lack of synergy effect in Ceria-NR and UiO-66-SO3H does not allow to generate stable plasma. Thus only Hopcalite has been studied in depth in APC. It is observed that the oxidation activity of the adsorbed toluene is significantly affected by the process variables. The stability of material was investigated in both cases, and it was confirmed that Hopcalite materials are very stable as evidenced by various characterization techniques. The catalytic activity was enhanced by impregnating active phase such as silver which led to improvement in the CO2 selectivity and CO2 yield at very low silver loading in both ATC and APC. A thorough examination of the material revealed that a good balance of adsorption capacity and catalytic activity (Cu2+,3+ and Mn3+,4+) is required. Moreover, the energy cost of APC is in the range of acceptable level (11.6 kWh·m−3) as a result with further optimization in different experimental parameters, it can be easily scalable in cost-effective manner. Both ATC and APC allow to reach toluene abatement efficiency and conversion to CO2 above 95 % on first run and 75% on stabilized materials. These results show that both ATC and APC process could be a promising energy-efficient toluene abatement processes and open the path for further development and scale-up
8
Cavalcante, Miquelina Rodrigues Castro. "Avaliação da qualidade térmica de praças em Maceió Alagoas : três estudos de caso." Universidade Federal de Alagoas, 2007. http://repositorio.ufal.br/handle/riufal/672.
Анотація:
The aim of this work is to evaluate the thermal quality of urban squares in Maceió city, AL,
Brazil, and its relationship with the use of those areas and the thermal sensation of the users.
The adopted procedures were the bibliographic review and a field research. In the bibliografic
review was set the theoretical reference: the squares´ characteristics, the urban climate and its
relationship with human thermal confort. To charachterize those squares it was used the
concept of Robba and Macedo´s SQUARE (2002). As a field research after an inventory of
the squares in Maceió, AL these squares were chosen and analyzed: Ricardo Lessa´s square,
in Tabuleiro dos Martins district; Tenente Madalena´s square, in Cruz das Almas district; and
Muniz Falcão´s square, in Ponta Verde´s district. Climate variables were measured and
questionnaires were applyed, and behaviour maps were built for January and February, 2006.
As thermal confort index it was used the parameters proposed by Fanger (1970). It has been
found that thermal quality in square areas is an important factor for their use, specially
because they refer to leasure and relaxing areas. This study represents an effort to raise
questions and should continue as an investigation object.Fundação de Amparo a Pesquisa do Estado de Alagoas
O presente trabalho tem como objetivo avaliar a qualidade térmica de praças na cidade de Maceió - AL e a sua relação com a utilização destes espaços e a sensação térmica dos usuários. Os procedimentos utilizados foram a pesquisa bibliográfica e documental e a pesquisa de campo. Na pesquisa bibliográfica e documental foi demarcado o referencial teórico: as características de praças, do clima urbano e a sua relação com o conforto térmico humano. Para caracterizar as praças foi usado o conceito de PRAÇA de Robba e Macedo (2002). Na pesquisa de campo, após a elaboração de um inventário das praças de Maceió-AL, foram escolhidas e analisadas as praças Ricardo Lessa, no Bairro Tabuleiro do Martins; Tenente Madalena, no Bairro Cruz das Almas; e Muniz Falcão, no Bairro Ponta Verde. Foram realizadas medições de variáveis climáticas, aplicados questionários e construídos mapas comportamentais nos meses de janeiro e fevereiro de 2006. Como Índice de Conforto Térmico foram utilizados os parâmetros estabelecidos por Fanger (1970). Ficou comprovado que a qualidade térmica dos espaços nas praças é um importante fator para a sua utilização, principalmente quando se trata de uma área destinada ao lazer e descanso. Em virtude dos limites e dificuldades, este estudo representa esforço de reflexão e um levantamento de questões que devem continuar sendo objeto de investigação.
9
Bärenfänger, Maja [Verfasser]. "Ebenen des Themas : Zur Interaktion von Thema, Text und Wissen / Maja Bärenfänger." Gießen : Universitätsbibliothek, 2012. http://d-nb.info/1064760600/34.
10
Zhang, Hua. "Saline, thermal and thermal-saline buoyant jets." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq21325.pdf.
11
Shi, Jun. "On thermal mismatch and thermal gradients and the failure of thermal barrier coatings." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 2.35 Mb., 123 p, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:3221078.
12
Rashidian, Mahla. "Thermal degradation study by continuous thermal stability rig." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for kjemisk prosessteknologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-22913.
Анотація:
This investigation was done at NTNU and together with Statoil research and development department in Rotvoll, Trondheim to facilitate a new semi dynamic amine thermal degradation rig.This study was an initial attempt to investigate semi dynamic thermal stability rig as an alternative to thermal degradation study. The major purposes are: (1) to study MEA and MDEA thermal degradation by thermal stability rig apparatus which is designed by Statoil. (2) to demonstrate the result differences between the new and conventional experimental method. MEA and MDEA were selected in this study due to have more available literature data in amine based absorption process. The loaded liquid was circulated through the pipe from the cold stream to the hot stream. There is no analytical method was connected to the rig therefore a regular sample was taken every week and sent to SINTEF analytical lab to identify degradation products.Residence time of solution in high temperature zone also was calculated as an important factor in thermal degradation investigation. Different authors have been provided to understand: the background, the experimental set up, the analytical method to describe the degradation products, data interpretation and the mechanism of the degradation.Based on analytical results, it seems that only small portion of MEA and MDEA were degraded. It showed that the elapsed time was not enough to observe degradation in a significant amount. Metal qualification tests showed low metal concentration in solutions and generally very little corrosiveness effect. However, few degradation products were reported in this study the most probably degradation mechanism is estimated similar to suggested degradation pathway by Davis (2009). More works are required in future to better interpret the new thermal stability rig.
13
Dyer, Kristy Kathleen. "Thermal and Non-Thermal Emission in Supernova Remnants." NCSU, 2001. http://www.lib.ncsu.edu/theses/available/etd-20010806-162918.
Анотація:
Supernova remnants present an excellent opportunity to study the shockacceleration of relativistic particles. X-ray synchrotron emission fromrelativistic electrons should contain important information, butextracting it requires advances in models and observations. I present thefirst test of sophisticated synchrotron models against high resolutionobservations on SN 1006, the first and best example of synchrotron X-rayemission, which has been well observed at radio, X-ray and gamma-raywavelengths. Synchrotron emission can be limited at the highest energies by finite age,radiative losses or electron escape. Earlier calculations suggested thatSN 1006 was escape limited. I adapted an escape-limited synchrotron modelfor XSPEC, and demonstrated that it can account for the dominantlynonthermal integrated spectrum of SN 1006 observed by ASCA-GIS and RXTEwhile constraining the values of the maximum electron energy and otherparameters. Combined with TeV observations, the fits give a mean postshockmagnetic field strength of 9 microgauss and 0.7% of the supernova energyin relativistic electrons. Simultaneous thermal fits gave abundances farabove solar, as might be expected for ejecta but had not previously beenobserved. I created subsets of the escape-limited model to fit spatially resolvedASCA SIS observations. I found only small differences between thenortheast and southwest limbs. A limit of less than 9% was placed on theamount of nonthermal flux elsewhere in the remnant. Important findingsinclude the possibility that rolloff frequency may change across theremnant face, and ruling out cylindrical symmetry for SN 1006 along aNW/SE axis. These models have implications far beyond SN 1006. The only previousmodel available to describe X-ray synchrotron emission was a powerlaw.These new models are superior to powerlaws both for their robustconstraints and because they shed physical insight on the accelerationmechanism. As new instruments increase our spatial and spectral resolutionI predict many more remnants will be found with varying amounts of X-raysynchrotron emission, hidden along with thermal lines and continuum. Theability to separate thermal and nonthermal emission is essential tounderstanding both nonthermal emission as well as the thermal component.
14
Šumić, Mersiha. "Thermal Performance of a Solarus CPC-Thermal Collector." Thesis, Högskolan Dalarna, Energi och miljöteknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:du-14526.
Анотація:
The aim of this master thesis is an investigation of the thermal performance of a thermal compound parabolic concentrating (CPC) collector from Solarus. The collector consists of two troughs with absorbers which are coated with different types of paint with unknown properties. The lower and upper trough of the collector have been tested individually. In order to accomplish the performance of the two collectors, a thorough literature study in the fields of CPC technology, various test methods, test standards for solar thermal collectors as well as the latest articles relating on the subject were carried out. In addition, the set‐up of the thermal test rig was part of the thesis as well. The thermal performance was tested according to the steady state test method as described in the European standard 12975‐2. Furthermore, the thermal performance of a conventional flat plate collector was carried out for verification of the test method. The CPC‐Thermal collector from Solarus was tested in 2013 and the results showed four times higher values of the heat loss coefficient UL (8.4 W/m²K) than what has been reported for a commercial collector from Solarus. This value was assumed to be too large and it was assumed that the large value was a result of the test method used that time. Therefore, another aim was the comparison of the results achieved in this work with the results from the tests performed in 2013. The results of the thermal performance showed that the optical efficiency of the lower trough of the CPC‐T collector is 77±5% and the corresponding heat loss coefficient UL 4.84±0.20 W/m²K. The upper trough achieved an optical efficiency of 75±6 % and a heat loss coefficient UL of 6.45±0.27 W/m²K. The results of the heat loss coefficients are valid for temperature intervals between 20°C and 80°C. The different absorber paintings have a significant impact on the results, the lower trough performs overall better. The results achieved in this thesis show lower heat loss coefficients UL and higher optical efficiencies compared to the results from 2013.
15
Humpheson, Lee. "Thermal inactivation kinetics and thermal physiology of Salmonella." Thesis, University of Surrey, 1997. http://epubs.surrey.ac.uk/844197/.
Анотація:
Microbial thermal inactivation survivor curves (log10 numbers plotted against time) have long been described as maintaining a strictly linear rate of decline. However, much evidence exists which suggests deviation from log-linear kinetics does occur, and that this is not purely the result of experimental procedure as contended by some authors. Here, the shape of inactivation kinetics in Salmonella enteritidis was investigated. A heat challenge method was developed which, as far as could be ascertained, was free from methodological artefacts influencing the shape of survivor curves. High initial cell densities allied to sensitive enumeration resulted in biphasic survivor curves at 60°C. Tailing survivors accounted for approximately 1 in 105 of the initial population and possessed roughly four times the heat resistance. At temperatures 50 to 65°C, the presence of tailing prevented the use of D-values to accurately describe death rates. However, describing survivor curves using a log-logistic model increased data-fit at all temperatures investigated. The biphasic nature of survivor curves was studied closely between 49 and 60°C. It was observed that the extent of tailing was temperature-dependent; as temperature decreased, linearity increased such that at 51°C, survivor curves had no tailing. Studies using S. typhimurium and S. senftenberg 775W revealed similar kinetics. In these salmonellas, survivor curves demonstrated linearity at 54 and 57°C, respectively. The influences of culture age and growth rate on the shape of 60°C-inactivation curves were also investigated. Batch-cultured S. enteritidis cells of various maturities gave rise to survivor curves of differing heat sensitivities. Exponentially growing cells were shown to be the most heat sensitive, while late-stationary phase cells were the only populations to result in non-tailed survivor curves. Carbon-limited continuously cultivated cells demonstrated similar biphasic inactivation kinetics. Predictably, the slowest dilution rate corresponded to the greatest heat resistance. Starved cells produced linear inactivation kinetics that were virtually identical to those of late-stationary phase batch-cultured cells. That tailing in batch cultures was similar to chemostat populations, indicated that possible differences in growth rates in batch-cultured cells could not account for tailing. Furthermore, growth was necessary for tailing to be observed. Investigations into the cause of tailing revealed that these cells were not genetically distinct from the majority population. Instead, it is believed that tailing cells arise following the expression of heat-shock proteins during heating. Partial inhibition of de novo protein synthesis during heating resulted in much reduced levels of tailing. It is proposed that the temperature of inactivation determines the proportion of cells capable of expressing a heat-shock response, such that the temperature at which linearity is achieved corresponds to the point at which all cells are fully heat-shock protected.
16
De, Indrayush. "Thermal characterization of nanostructures using scanning thermal microscopy." Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0563/document.
Анотація:
La caractérisation thermique est cruciale pour la conception et le développement d'applications critiques dans divers domaines. Elle trouve son utilisation dans la détection de défauts et de points chauds dans la fabrication de semi-conducteurs, l'imagerie sous-sol ainsi que la recherche de transport thermique et de charge à des longueurs inférieures à 100 nm. La capacité de comprendre et de contrôler les propriétés thermiques des nanostructures à un niveau de sous-micron est essentielle pour obtenir les performances souhaitées. Pour atteindre cet objectif, la microscopie thermique à balayage (SThM) est très bien adaptée pour cartographier la conductivité thermique à la surface des matériaux et des appareils à l'échelle nanométrique.SThM est une technique d'imagerie "champ proche". C'est une méthode de contact, la sondeétant en contact avec la surface à une force contrôlée. STHM utilise une structure cantilever identique à celle des sondes utilisées dans un Microscope à Force Atomique (AFM). La principale différence est le fait qu'un capteur thermique est intégré à la pointe de la sonde. En outre, ce capteur peut également être utilisé comme chauffage dans le cas d'éléments thermorésistants tels que Pt ou Pd. Par conséquent, le SThM est le résultat d'un AFM équipé d'une sonde thermique. Cet instrument fournit une résolution sous-micromètre dans la résolution spatiale, c'est-à-dire plus que la résolution des techniques optiques dans la gamme de longueurs d'onde visible. La résolution classique qui est réalisée de nos jours est de l'ordre de moins de 100nanomètres alors que celle obtenue avec la première sonde Wollaston était environ 10 fois plus élevée.Par conséquent, mesurer la température et les propriétés thermiques de la matière à la microscales ont deux objectifs difficiles qui ont monopolisé l'énergie et le temps de nombreux chercheurs partout dans le monde depuis plusieurs décennies. Ces deux objectifs ne sont pas similaires. Tout d'abord, la mesure d'une température dans un domaine dont la dimension caractéristique est inférieure au micromètre semble moins difficile que mesurer la conductivité thermique d'un matériau à cette échelle. [...]The objective of this thesis is to master quantitative aspects when using nearfield thermal microscopy by using the scanning thermal microscopy technique (SThM). We start by taking an in-depth look into the work performed previously by other scientist and research organizations. From there, we understand the progress the SThM probes have made through the decades, understand the probe sensitivity to the range of conductivity of the materials under investigation, verify the resistances encountered when the probe comes in contact with the sampl and the applications of SThM.Then we look into the equipment necessary for performing tests to characterize material thermal properties. The SThM we use is based on atomic force microscope (AFM) with a thermal probe attached at the end. The AFM is described in this work along with the probes we have utilized.For the purpose of our work, we are only using thermoresistive probes that play the role of the heater and the thermometer. These probes allow us to obtain sample temperature and thermalconductivity. We use two different types of thermal probes – 2-point probe and 4-point probe with SiO2 or with Si3N4 cantilever. Both the probes are very similar when it comes to functioning with the major difference being that the 4-point probe doesn’t have current limiters. Then, we present the use of recent heat-resistive probes allowing to reach a spatial resolution of the orde rof 100 nm under atmosphere and of 30 nm under vacuum. These probes can be used in passive mode for measuring the temperature at the surface of a material or component and in activemode for the determination of the thermal properties of these systems. Using thermoresistive probes means that no specialized devices are necessary for operation. Using simple commercialsolutions like simple AC or DC current and Wheatstone bridge are sufficient to provide basic thermal images. In our case we have also utilized other industrial devices and a home madeSThM setup to further improve the quality of measurement and accuracy. All the elements of the experimental setup have been connected using GPIB and that have been remotely controlled from a computer using a code developed under Python language. This code allows to make the frequency dependent measurement as well as the probe calibration. [...]
17
Li, Yifan Li. "NANOSCALE THERMAL CHARACTERIZATION BY SCANNING THERMAL MICROSCOPY (STHM)." University of Akron / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=akron159057422807603.
18
Mao, Guofeng. "Thermal bridges." Doctoral thesis, KTH, Byggnader och installationer, 1997. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-2609.
19
Karayacoubian, Paul. "Effective Thermal Conductivity of Composite Fluidic Thermal Interface Materials." Thesis, University of Waterloo, 2006. http://hdl.handle.net/10012/2881.
Анотація:
Thermally enhanced greases made of dispersions of small conductive particles suspended in fluidic polymers can offer significant advantages when used as a thermal interface material (TIM) in microelectronics cooling applications. A fundamental problem which remains to be addressed is how to predict the effective thermal conductivity of these materials, an important parameter in establishing the bulk resistance to heat flow through the TIM. The following study presents the application of two simple theorems for establishing bounds on the effective thermal conductivity of such inhomogeneous media. These theorems are applied to the development of models which are the geometric means of the upper and lower bounds for effective thermal conductivity of base fluids into which are suspended particles of various geometries.
Numerical work indicates that the models show generally good agreement for the various geometric dispersions, in particular for particles with low to moderate aspect ratios. The numerical results approach the lower bound as the conductivity ratio is increased. An important observation is that orienting the particles in the direction of heat flow leads to substantial enhancment in the thermal conductivity of the base fluid. Clustering leads to a small enhancement in effective thermal conductivity beyond that which is predicted for systems composed of regular arrays of particles. Although significant enhancement is possible if the clusters are large, in reality, clustering to the extent that solid agglomerates span large distances is unlikely since such clusters would settle out of the fluid.
In addition, experimental work available in the literature indicates that the agreement between the selected experimental data and the geometric mean of the upper and lower bounds for a sphere in a unit cell are in excellent agreement, even for particles which are irregular in shape.
20
Yam, Chi-wai, and 任志偉. "Effect of internal thermal mass on building thermal performance." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2003. http://hub.hku.hk/bib/B27770631.
21
Carmody, Rachel Naomi. "Energetic Consequences of Thermal and Non-Thermal Food Processing." Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10608.
Анотація:
All human societies process their food extensively by thermal and non-thermal means. This feature distinguishes us from other species, and may even be compulsory given that humans are biologically committed to an energy-rich diet that is easy to chew and digest. Yet the energetic consequences of food processing remain largely unknown. This dissertation tests the fundamental hypothesis that thermal and non-thermal processing lead to biologically relevant increases in energy gain from protein-rich meat and starch-rich tubers, two major caloric resources for modern and ancestral humans that present divergent structural and macronutrient profiles. The energetic consequences of food processing are evaluated using three indices of energy gain, each of which account for costs not currently captured by conventional biochemical assessments of dietary energy value. Chapter 2 investigates the effects of cooking and pounding on net energy gain as indexed by changes in body mass, controlling for differences in food intake and activity level. Chapter 3 examines the effect of cooking and pounding on diet-induced thermogenesis, the metabolic cost of food digestion. Chapter 4 considers the effort required to engage in food processing, arguing that the advantageous ratio of benefit to cost has likely had important effects on human life history. By each of these definitions of energy gain, food processing is shown to have substantial energetic significance. Overall, energetic gains due to thermal processing exceeded those of non-thermal processing, consistent with recent proposals that the adoption of cooking had a particularly important influence on human biology. Gains due to food processing were observed in both meat and tuber substrates, supporting a transformative role for habitual food processing in the evolution and maintenance of the human energy budget.Human Evolutionary Biology
22
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.
Анотація:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, May, 2020Cataloged 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
23
Green, Craig Elkton. "Composite thermal capacitors for transient thermal management of multicore microprocessors." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44772.
Анотація:
While 3D stacked multi-processor technology offers the potential for significant computing advantages, these architectures also face the significant challenge of small, localized hotspots with very large heat fluxes due to the placement of asymmetric cores, heterogeneous devices and performance driven layouts. In this thesis, a new thermal management solution is introduced that seeks to maximize the performance of microprocessors with dynamically managed power profiles. To mitigate the non-uniformities in chip temperature profiles resulting from the dynamic power maps, solid-liquid phase change materials (PCMs) with an embedded heat spreader network are strategically positioned near localized hotspots, resulting in a large increase in the local thermal capacitance in these problematic areas.
Theoretical analysis shows that the increase in local thermal capacitance results in an almost twenty-fold increase in the time that a thermally constrained core can operate before a power gating or core migration event is required. Coupled to the PCMs are solid state coolers (SSCs) that serve as a means for fast regeneration of the PCMs during the cool down periods associated with throttling events. Using this combined PCM/SSC approach allows for devices that operate with the desirable combination of low throttling frequency and large overall core duty cycles, thus maximizing computational throughput. The impact of the thermophysical properties of the PCM on the device operating characteristics has been investigated from first principles in order to better inform the PCM selection or design process.
Complementary to the theoretical characterization of the proposed thermal solution, a prototype device called a "Composite Thermal Capacitor (CTC)" that monolithically integrates micro heaters, PCMs and a spreader matrix into a Si test chip was fabricated and tested to validate the efficacy of the concept. A prototype CTC was shown to increase allowable device operating times by over 7X and address heat fluxes of up to ~395 W/cm2. Various methods for regenerating the CTC have been investigated, including air, liquid, and solid state cooling, and operational duty cycles of over 60% have been demonstrated.
24
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.
25
Nasrollahi, Nazanin. "Thermal environments and occupant thermal comfort in Iranian office buildings." Thesis, Cardiff University, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.445202.
26
Broadbent, Alison. "The thermal and non-thermal radio emission from the galaxy." Thesis, Durham University, 1989. http://etheses.dur.ac.uk/6548/.
Анотація:
It is shown that a detailed correlation exists between IRAS 60 µm band emission from the galactic disc and radio continuum emission measured at a similar angular resolution at 11 and 6 cm. The emission at these short radio wavelengths is predominantly from thermal bremsstrahlung in regions of ionized gas and so the strong correlation, which holds for the diffuse, extended emission as well as the discrete, compact sources, indicates that an important contribution to the 60 µm emission is associated with HII regions. Isolation of this component of the 60 µm infrared emission has involved the estimation of the zodiacal light contamination and detailed modelling of the HI-associated dust emission. The residual 60 µm emission can then be used as a tracer of radio thermal emission. On the small scale this enabled a search for new supernova remnant candidates in the 11 cm survey of Reich et al. and the 6 cm survey of Haynes et al. close to the inner Galactic Plane. On the large scale we have separated the thermal and non-thermal emission of the 408 MHz all-sky survey of Haslam et al. from the whole of the Galactic Plane and within ~ 8º of the plane. From the thermal galactic emission we have been able to estimate the average infrared excess, the total 60 µm luminosity and total mass of HII in the Galaxy. The clearer picture obtained of the non-thermal emission of the Galaxy has allowed us to improve upon previous attempts at modelling the synchrotron emission in terms of the cosmic ray electron distribution and magnetic field variation modulated by the galactic spiral structure.
27
Kuryliw, Erik Adam. "Analyzing the thermal annealing behavior of laser thermal processed silicon." [Gainesville, Fla.] : University of Florida, 2003. http://purl.fcla.edu/fcla/etd/UFE0000979.
28
Tang, Xiaoli Dong Jianjun. "Theoretical study of thermal properties and thermal conductivities of crystals." Auburn, Ala, 2008. http://repo.lib.auburn.edu/EtdRoot/2008/SUMMER/Physics/Dissertation/Tang_Xiaoli_9.pdf.
29
Vuppala, Archana. "Thermal and thermal stress analyses of the state-changing tooling." abstract and full text PDF (free order & download UNR users only), 2008. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1460787.
30
Alammar, Ahmed Ali Ghulfus. "Enhancing thermal performance of heat pipe based solar thermal collector." Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8207/.
Анотація:
In this work, a CFD model was developed to simulate the flow and phase-change process inside the Two-Phase Closed Thermosyphon (TPCT). This was carried out to investigate the effect of fill ratio and inclination angle on the thermal performance of the TPCT, and to visualise the phase change characteristics under the influence of the inclination and different fill ratios. Also, the surface wettability in terms of the contact angle was investigated to report their effect on the thermal characteristics of the TPCT and to visualise the phase-change characteristics inside the TPCT for different contact angles using Fluent Ansys. Furthermore, the effect of different parameters on the geyser boiling in the TPCT was investigated experimentally. Consequently, the influence of geyser effect on the TPCT thermal characteristics was examined under the effect of various liquid charges and inclination angles at a broad range of heat inputs. Finally, advanced manufacturing technique using wire Electrical Discharge Machining (EDM) was employed to introduce a surface roughness in the TPCT internal wall, thereby enhancing the thermal performance of the TPCT. This was achieved by comparing its thermal performance with a plain TPCT at two different initial sub-atmospheric pressures (3 and 30 kPa) and different heat loads.
31
Samba, Ahmadou. "Battery electrical vehicles analysis of thermal modelling and thermal management." Caen, 2015. http://www.theses.fr/2015CAEN2003.
Анотація:
L’avancée de la recherche sur les batteries a conduit à une utilisation massive des batteries Lithium-ion de grande capacité dans les véhicules électriques. De tels designs, en grand format, ont l'avantage de réduire le nombre de cellules interconnectées dans les packs de batteries. Dans les applications de transport, le temps de recharge des batteries constitue un frein au développement des véhicules électriques. L'augmentation du courant de charge peut soumettre à la batterie à des situations très critiques et peut ainsi entrainer une augmentation considérable de sa température. En long terme, ces phénomènes peuvent conduire à la réduction de sa durée de vie ainsi que ses performances et dans certains cas à l’emballement thermique. Afin d’éviter de telles situations, il est nécessaire d’optimiser la gestion thermique de manière à maintenir la batterie dans une gamme de températures de fonctionnement sûre. Ceci passe par la mise en place d’un modèle thermique capable de prédire la température d’une cellule et d’un pack de batterie à différentes conditions de fonctionnement et ensuite proposer différentes stratégies de refroidissements. Compte tenu de la forme et des dimensions du type de batterie utilisé (batterie « pouch ») un modèle électro-thermique est développé afin de prédire la distribution de température de la cellule, ce modèle nécessite moins de paramètres d'entrée et possède une grande précision. En outre, un nouvel outil d'estimation des paramètres thermiques a été développé. Le comportement thermique de la batterie, soumise à des conditions de fonctionnements extrêmes, a été étudié avec ce modèle. De ces résultats, on remarque que la cellule de batterie présente une distribution thermique non-uniforme lorsque celle-ci est parcourue par des courants de grandes amplitudes. Ce constat nous amène à étudier le design des batteries de type « pouch » afin d’élire celle qui présente une distribution thermique et électrique plus uniformes. Pour se faire un modèle 3D électrochimique-thermique a été développé. Enfin, différentes stratégies de gestion thermique des batteries telles que: le refroidissement actif par liquide et passif utilisant un matériau à changement de phase (liquide-solide à changement de phase) incorporé dans une mousse d'aluminium, ont été étudiées puis comparés en appliquant un cycle de conduite, provenant d’un véhicule tout électrique de la gamme Peugeot. L'objectif principal est de réduire la complexité, le poids, le volume, le coût et également de maintenir à un haut niveau de sureté de fonctionnement du module de batterieAdvanced research on rechargeable Lithium-ion batteries has allowed for large format and high-energy batteries to be largely used in Battery Electric Vehicles (BEVs). For transportation applications, beside limitations of driving range, long charging time is still considered as an important barrier for a wide use of BEVs. The increase of the charging current amplitude may however subject the battery to stressful situations and can significantly increase the temperature of the battery. These phenomena reduce the battery’s lifetime and performances and in worst-case scenario, thermal runaway can occur. To avoid this, there is a need for an optimized thermal management in order to keep the battery in a safe and beneficial range of operating conditions. Firstly, in this PhD dissertation a two-dimensional electrical-thermal model has been developed to predict the cell temperature distribution over the surface of the battery. This model requires less input parameters and still has high accuracy. In addition, a novel estimation tool has been developed for estimation of the thermal model parameters. Furthermore, the thermal behavior of the proposed battery has been investigated at different environmental conditions as well as during the abuse conditions for assessment of thermal stability of the battery. Taking into account the harsh thermal distribution, an advanced three-dimensional electrochemical-thermal model has been developed in order to investigate the impact of the cell design on the thermal, voltage and current distributions in order to avoid high non-homogenous distribution. The developed model allows us to optimize the cell design, in order to achieve the longest lifetime and high performances of battery cell. Finally, different thermal management strategies such as liquid cooling and passive cooling using phase change material embedded in an aluminium-foam (liquid-solid phase change) have been investigated and compared in depth by applying real BEV drive cycles. The main objective of this study is to decrease the complexity, the weight, the volume and the cost and to maintain high safety according to the best strategy
32
Fredi, Giulia. "Multifunctional polymer composites for thermal energy storage and thermal management." Doctoral thesis, Università degli studi di Trento, 2020. http://hdl.handle.net/11572/265328.
Анотація:
Thermal energy storage (TES) consists in storing heat for a later use, thereby reducing the gap between energy availability and demand. The most diffused materials for TES are the organic solid-liquid phase change materials (PCMs), such as paraffin waxes, which accumulate and release a high amount of latent heat through a solid-liquid phase change, at a nearly constant temperature. To avoid leakage and loss of material, PCMs are either encapsulated in inert shells or shape-stabilized with porous materials or a nanofiller network. Generally, TES systems are only a supplementary component added to the main structure of a device, but this could unacceptably rise weight and volume of the device itself. In the applications where weight saving and thermal management are both important (e.g. automotive, portable electronics), it would be beneficial to embed the heat storage/management in the structural components.
The aim of this thesis is to develop polymer composites that combine a polymer matrix, a PCM and a reinforcing agent, to reach a good balance of mechanical and TES properties. Since this research topic lacks a systematic investigation in the scientific literature, a wide range of polymer/PCM/reinforcement combinations were studied in this thesis, to highlight the effect of PCM introduction in a broad range of matrix/reinforcement combinations and to identify the best candidates and the key properties and parameters, in order to set guidelines for the design of these materials.
The thesis in divided in eight Chapters. Chapter I and II provide the introduction and the theoretical background, while Chapter III details the experimental techniques applied on the prepared composites. The results and discussion are then described in Chapters IV-VII. Chapter IV presents the results of PCM-containing composites having a thermoplastic matrix. First, polyamide 12 (PA12) was melt-compounded with either a microencapsulated paraffin (MC) or a paraffin powder shape-stabilized with carbon nanotubes (ParCNT), and these mixtures were used as matrices to produce thermoplastic laminates with a glass fiber fabric via hot-pressing. MC was proven more suitable to be combined with PA12 than ParCNT, due to the higher thermal resistance. However, also the MC were considerably damaged by melt compounding and the two hot-pressing steps, which caused paraffin leakage and degradation, as demonstrated by the relative enthalpy lower than 100 %. Additionally, the PCM introduction decreased the mechanical properties of PA12 and the tensile strength of the laminates, but for the laminates containing MC the elastic modulus and the strain at break were not negatively affected by the PCM. Higher TES properties were achieved with the production of a semi-structural composite that combined PA12, MC and discontinuous carbon fibers. For example, the composite with 50 wt% of MC and 20 wt% of milled carbon fibers exhibited a total melting enthalpy of 60.4 J/g and an increase in elastic modulus of 42 % compared to the neat PA. However, the high melt viscosity and shear stresses developed during processing were still responsible for a not negligible PCM degradation, as also evidenced by dynamic rheological tests. Further increases in the mechanical and TES properties were achieved by using a reactive thermoplastic matrix, which could be processed as a thermosetting polymer and required considerably milder processing conditions that did not cause PCM degradation. MC was combined with an acrylic thermoplastic resin and the mixtures were used as matrices to produce laminates with a bidirectional carbon fabric, and for these laminates the melting enthalpy increased with the PCM weight fraction and reached 66.8 J/g. On the other hand, the increased PCM fraction caused a rise in the matrix viscosity and so a decrease in the fiber volume fraction in the final composite, thereby reducing the elastic modulus and flexural strength. Dynamic-mechanical investigation evidenced the PCM melting as a decreasing step in ’; its amplitude showed a linear trend with the melting enthalpy, and it was almost completely recovered during cooling, as evidenced by cyclic DMA tests.
Chapter V presents the results of PCM-containing thermosetting composites. A further comparison between MC and ParCNT was performed in a thermosetting epoxy matrix. First, ParCNT was mixed with epoxy and the mixtures were used as matrices to produce laminates with a bidirectional carbon fiber fabric. ParCNT kept its thermal properties also in the laminates, and the melting enthalpy was 80-90 % of the expected enthalpy. Therefore, ParCNT performed better in thermosetting than in thermoplastic matrices due to the milder processing conditions, but the surrounding matrix still partially hindered the melting-crystallization process. Therefore, epoxy was combined with MC, but the not optimal adhesion between the matrix and the MC shell caused a considerable decrease in mechanical strength, as also demonstrated by the fitting with the Nicolais-Narkis and Pukanszky models, both of which evidenced scarce adhesion and considerable interphase weakness. However, the Halpin-Tsai and Lewis-Nielsen models of the elastic modulus evidenced that at low deformations the interfacial interaction is good, and this also agrees with the data of thermal conductivity, which resulted in excellent agreement with the Pal model calculated considering no gaps at the interface. These epoxy/MC mixtures were then reinforced with either continuous or discontinuous carbon fibers, and their characterization confirmed that the processing conditions of an epoxy composite are mild enough to preserve the integrity of the microcapsules and their TES capability. For continuous fiber composites, the increase in the MC fraction impaired the mechanical properties mostly because of the decrease in the final fiber volume fraction and because the MC phase tends to concentrate in the interlaminar region, thereby lowering the interlaminar shear strength. On the other hand, a small amount of MC enhanced the mode I interlaminar fracture toughness (Gic increases of up to 48 % compared to the neat epoxy/carbon laminate), as the MC introduced other energy dissipation mechanisms such as the debonding, crack deflection, crack pinning and micro-cracking, which added up to the fiber bridging.
Chapter VI introduces a fully biodegradable TES composite with a thermoplastic starch matrix, reinforced with thin wood laminae and containing poly(ethylene glycol) as the PCM. The wood laminae successfully acted as a multifunctional reinforcement as they also stabilized PEG in their inner pores (up to 11 wt% of the whole laminate) and prevent its leakage. Moreover PEG was proven to increase the stiffness and strength of the laminate, thereby making the mechanical and TES properties synergistic and not parasitic.
Finally, Chapter VII focused on PCM microcapsules. The synthesis of micro- and nano-capsules with an organosilica shell via a sol-gel approach clarified that the confinement in small domains and the interaction with the shell wall modified the crystallization behavior of the encapsulated PCM, as also evidenced by NMR and XRD studies and confirmed by DSC results. In the second part of Chapter VII, a coating of polydpamine (PDA) deposited onto the commercial microcapsules MC. The resulting PDA coating was proven effective to enhance the interfacial adhesion with an epoxy matrix, as evidenced by SEM micrographs. XPS demonstrated that the PDA layer was able to react with oxirane groups, thereby evidencing the possibility of forming covalent bond with the epoxy matrix during the curing step.
33
Xu, Zheng. "Thermal Performance Comparison of Three Integrated Thermal Solar Roof Collectors." Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/35859.
Анотація:
The integrated solar roof collector system can bring the house year-round energy saving benefit. In heating season, part of the space heating and preheating domestic hot water demand can be met by this integrated system. In the cooling season, cooling load reduction and preheating domestic hot water can be achieved by operating this system. The traditional solar thermal system is an add-on system rather than integrated, which increases the cost-benefit ratio. The current system is integrated with the roof structure. Except for the energy collecting benefit, it will reduce the material cost, labor cost and construction period.
The objectives of this research is to estimate the energy performance of three collector configurations including space heating saving, and preheat hot water saving. This study also compares energy performance for the three collectors on two types of evaluated houses in Roanoke, Virginia.Master of Science
34
Jensma, Madeline R. "THERMAL MODELING AND TESTING OF THE BLUE THERMAL VACUUM CHAMBER." DigitalCommons@CalPoly, 2020. https://digitalcommons.calpoly.edu/theses/2151.
Анотація:
The Blue Thermal Vacuum Chamber (TVAC) located in the Space Environments Laboratory at California Polytechnic State University, San Luis Obispo (Cal Poly), may be used for thermal vacuum testing of test articles that fit with in the semi cylindrical test section that has a radius of approximately 18 cm and a length of 61 cm. The potential test articles include CubeSat systems and subsystem. The Blue TVAC can also be used for educational and research purposes. The goal of this thesis project is to develop a thermal model of the Blue TVAC to predict and analyze the thermal response of the chamber. Thermal vacuum testing is conducted to verify the repeatability of a test and validate the thermal model. Thermal vacuum tests were conducted according to the ISO Standard 19683 to measure the temperature at various points in the chamber. This data was used to determine the thermal response of the chamber and the distribution of heat within the chamber. After conducting a total of fifteen thermal vacuum tests, eleven without a test article and four with a test article, a repeatable testing procedure was written to ensure that results from such tests are consistent. A thermal model was developed using Thermal Desktop to predict the temperature distribution within the chamber during the cooling phase, cold soak phase, heating phase, and hot soak phase of a thermal vacuum test. The simulations of the empty thermal vacuum test predict the platen temperature in the Blue TVAC with a thermal uncertainty margin of less than 10℃. The simulations of the thermal vacuum test with a 3U CubeSat mass model predict the platen temperature in the Blue TVAC with a thermal uncertainty margin of less than 30℃. These simulations can predict the mass model temperature with a thermal uncertainty margin of less than 15℃. The thermal model can v be used to analyze how future changes to the Blue TVAC may affect the thermal distribution in the chamber. Finally, recommendations are made to further improve the performance and repeatability of the Blue TVAC as well as the thermal model with specific instruction for implementing changes and verifying potential improvements.
35
Shi, Qi. "PREDICTION OF THERMAL DISTORTION AND THERMAL FATIGUE IN SHOT SLEEVES." The Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=osu1034967167.
36
Tardieu, Giliane. "Thermal conductivity prediction." Thesis, Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/10014.
37
Huynh, Kien Khanh. "Human Thermal Comfort." MSSTATE, 2001. http://sun.library.msstate.edu/ETD-db/theses/available/etd-04092001-135104/.
Анотація:
The purpose of this research is to investigate human comfort criteria under steady-state conditions as a function of ambient air temperature, mean radiant temperature, relative humidity, air velocity, level of activity, and clothing insulation. Since the current ASHRAE Standard 55-1994 is for sedentary activity, this study will consider relative humidity (20% to 65%), dry bulb temperature (73 oF to 82 oF), air velocity (30 fpm and 50 fpm), and sedentary-to-moderate activity. The mean radiant temperature will be taken to be the same as the ambient air temperature. The experimental results collected at the Kansas State University Environmental Test Chamber are compared with the Fanger (1982) thermal comfort model and with ASHRAE Standard 55-1994. The experimental study results agreed well with ASHARE Standard 55-1994 for 1-met activity level (sedentary), and the thermal comfort for 1-met activity level was predicted with reasonable accuracy by Fanger?s (1982) Model. For 2.3 met activity level, the experimental results did not agree with ASHRAE Standard 55-1994 or the Fanger Model predictions.
38
Loo, Fook Leong. "Polarimetric thermal imaging." Thesis, Monterey, Calif. : Naval Postgraduate School, 2007. http://bosun.nps.edu/uhtbin/hyperion.exe/07Mar%5FLoo.pdf.
Анотація:
Thesis (M.S. in Electronic Warfare System Engineering)--Naval Postgraduate School, March 2007.Thesis Advisor(s): Alfred W. Cooper. "March 2007." Includes bibliographical references (p. 101-102). Also available in print.
39
Ruffoni, Matthew Paul. "Thermal differential EXAFS." Thesis, University of Warwick, 2006. http://wrap.warwick.ac.uk/59702/.
Анотація:
Differential EXAFS (DiffEXAFS) is a new and novel technique for the study of small atomic strains. It relies on examining tiny differences in x-ray absorption spectra - taken under high-stability, low-noise conditions - generated by unit modulation of some sample bulk parameter. Initial experiments conducted by Pettifer et al. [64] to measure the magnetostriction of FeCo, revealed a sensitivity to atomic displacements of the order of one femtometre (10−15m). This was two orders of magnitude more sensitive than thought possible, based on conventional EXAFS techniques [16] [2]. The mandate for this thesis was to extend DiffEXAFS to the case of samples undergoing temperature modulation - to develop Thermal Differential EXAFS - and in doing so, demonstrate that DiffEXAFS is a generally applicable technique for studying small atomic strains. Topics covered here include the nature of Thermal DiffEXAFS signals, the design, manufacture, and characterisation of apparatus for Thermal DiffEXAFS experiments, and new analysis techniques developed to extract information from DiffEXAFS data. Thermal expansion coefficients have been determined for Fe and SrF2, for temperature modulation of the order of one Kelvin, proving the viability of the technique. Numerically, these were a Fe = (11.6±0.4)×10−6K−1 and a SrF2 = (19±2)×10−6K−1 respectively, which agreed with published values [52] [74]. In these measurements sensitivity to mean atomic displacements of about 0.3 femtometres was achieved. The more interesting case of thermally induced phase transitions has also been studied, with DiffEXAFS measurements taken through the Martensitic phase transition of the Heusler alloy Ni2MnGa. These revealed a hardening of the lattice as the transition was approached in the Martensite phase, agreeing with published trends [93][56], and an accompanying lattice contraction not seen previously.
40
Weir, I. J. M. "The thermal lens." Thesis, University of Strathclyde, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372116.
41
Zhang, L. "Modelling thermal regenerators." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385828.
42
Schmidt, Aaron Jerome 1979. "Contact thermal lithography." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/27116.
Анотація:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.Includes bibliographical references (p. 65-67).
Contact thermal lithography is a method for fabricating microscale patterns using heat transfer. In contrast to photolithography, where the minimum achievable feature size is proportional to the wavelength of light used in the exposure process, thermal lithography is limited by a thermal diffusion length scale and the geometry of the situation. In this thesis the basic principles of thermal lithography are presented. A traditional chrome-glass photomask is brought into contact with a wafer coated with a thermally sensitive polymer. The mask-wafer combination is flashed briefly with high intensity light, causing the chrome features heat up and conduct heat locally to the polymer, transferring a pattern. Analytic and finite element models are presented to analyze the heating process and select appropriate geometries and heating times. In addition, an experimental version of a contact thermal lithography system has been constructed and tested. Early results from this system are presented, along with plans for future development.
by Aaron Jerome Schmidt.
S.M.
43
Klett, Sven. "Creating Thermal Solutions." Technische Universität Chemnitz, 2018. https://monarch.qucosa.de/id/qucosa%3A21506.
Анотація:
Redesign einer Halbleiterklammer mittels Topologieoptimierung und integrierter FEM Rechnung.
Optimierung mittels Inspire von solidThinking. Halbleiterklammer zur Sicherstellung der Kühlung von IGBT Bausteinen in Hochstromapplikationen.
Optimierung unter der Restriktion verfügbarer Fertigungsverfahren.
44
Mavromatidis, Pavlos. "Microwave thermal spraying." Thesis, University of Liverpool, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.422101.
45
Peiró, Bell-lloch Gerard. "Emmagatzematge d’energia tèrmica d’alta temperatura per aplicacions de fred solar i centrals termosolars." Doctoral thesis, Universitat de Lleida, 2017. http://hdl.handle.net/10803/462071.
Анотація:
Aquesta tesi contribueix en el camp de l’emmagatzematge d’energia tèrmica (TES) per aplicacions de fred solar i centrals termosolars. Concretament, en la validació i optimització de la tecnologia TES a través de l’experimentació a escala de planta pilot. La present tesi s’ha dividit en dues parts. Una, on s’estudien dues tècniques de millora de la transferència de calor en sistemes d’emmagatzematge per calor latent per aplicacions de fred solar. I una altra, on s’estudia la viabilitat d’un intercanviador de plaques per operar en un sistema d’emmagatzematge de doble tanc per centrals termosolars de cilindre parabòlic. Així com la influència de les estratègies d’operació i del fluid caloportador en el procés de transferència de calor en el mateix intercanviador. Els diferents estudis d’aquesta tesi han estat realitzats mitjançant la planta pilot de la Universitat de Lleida construïda l’any 2008 amb la col·laboració d’Abengoa.Esta tesis contribuye en el campo del almacenamiento de energía térmica (TES) para aplicaciones de frío solar y centrales termosolares. Concretamente, en la validación y optimización de la tecnología TES a través de la experimentación a escala de planta piloto. La presente tesis está dividida en dos partes. Una, donde se estudian dos técnicas de mejora de la transferencia de calor en sistemas de almacenamiento por calor latente para aplicaciones de frío solar. Y otra, donde se demuestra la viabilidad de un intercambiador de placas para operar en un sistema de almacenamiento de doble tanque para centrales termosolares de cilindro parabólico. Así como la influencia de las estrategias de operación y del fluido caloportador en el proceso de transferencia de calor en el mismo intercanviador. Los diferentes estudios de esta tesis se han realizado mediante la planta piloto de la Universidad de Lleida construida en 2008 con la colaboración de Abengoa.
This thesis has contributed to the thermal energy storage (TES) field applied in solar cooling and concentrated solar power plants. Specifically, it is focused on validation and optimization of TES technology through the experimentation at pilot plant scale. This thesis is divided in two parts. A first part, where two heat transfer enhancement techniques in latent heat storage systems for solar cooling applications have been studied. And a second part, where the feasibility of plate heat exchanger to operate in a two-tank molten salts TES system for parabolic trough solar plant has been demonstrated. Moreover the influence of operational strategies and heat transfer fluid in heat transfer process of the same heat exchanger has been studied. The different studies included in this thesis has been performed through the pilot plant of University of Lleida built in 2008 in collaboration with Abengoa.
46
Ocak, Mustafa. "Conduction Based Compact Thermal Modeling For Thermal Analysis Of Electronic Components." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612100/index.pdf.
Анотація:
Conduction based compact thermal modeling of DC/DC converters, which are
electronic components commonly used in military applications, are investigated.
Three carefully designed numerical case studies are carried out at component, board
and system levels using ICEPAK software. Experiments are conducted to gather
temperature data that can be used to study compact thermal models (CTMs) with
different levels of simplification.
In the first (component level) problem a series of conduction based CTMs are
generated and used to study the thermal behavior of a Thin-Shrink Small Outline
Package (TSSOP) type DC/DC converter under free convection conditions. In the
second (board level) case study, CTM alternatives are produced and investigated for
module type DC/DC converter components using a printed circuit board (PCB) of an
electro-optic system. In the last case study, performance of the CTM alternatives
generated for the first case are assessed at the system level using them on a PCB
placed inside a realistic avionic box.
v
Detailed comparison of accuracy of simulations obtained using CTMs with various
levels of simplification is made based on experimentally obtained temperature data.
Effects of grid size and quality, choice of turbulence modeling and space
discretization schemes on numerical solutions are discussed in detail.
It is seen that simulations provide results that are in agreement with measurements
when appropriate CTMs are used. It is also showed that remarkable reductions in
modeling and simulation times can be achieved by the use of CTMs, especially in
system level analysis.
47
McDowell, Alastair Kieran Joel. "Thermal modelling and optimisation of building-integrated photo-voltaic thermal systems." Thesis, University of Canterbury. Electrical & Computer Engineering, 2015. http://hdl.handle.net/10092/11079.
Анотація:
This Masters project has involved detailed thermal analysis of a unique
renewable energies building. A TRNSYS model of this building has been
developed and validated by real measurements and has shown to be capable of accurately predicting room temperatures and total heat gain from a solar-thermal roofing system. Supporting experiments were conducted experimentally and numerically. An experimental solar thermal testing unit constructed for the purpose of validating the solar-thermal roof concept. This experimental apparatus has been used to evaluate the effect of various operating procedures on the total heat gain from the system under a range of meteorological conditions. The validated thermal building model is used to conduct long-term simulations to provide a measure of year-round thermal performance of the building and estimated gains from renewable energy systems. Similar techniques are used to assist in the design and optimisation of a new transportable sustainable building concept in association with StoneWood Homes. It was found that a 4.5kW BIVP/T system could
supply the small building with 100% of the yearly electrical energy and space heating requirements.
48
Ding, Siwen. "Investigation on thermal barrier coating and thermal behaviour at high temperature." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/41696/.
Анотація:
The oxidation behaviour of diffusion and overlay coating, manufactured by pack cementation and high velocity oxygen fuel (HVOF) techniques, was studied under isothermal condition at a temperature of 1100 °C for up to 500 hours. Detailed analysis on oxide thickness coupled with cross section microstructure observation was carried out. The results shown sub-parabolic oxide growth for all samples. To simulate a real operating condition for the thermal barrier coating (TBC) system, high temperature oxy-acetylene flame based burner rig was designed, manufactured and calibrated. A maximum surface temperature of 1400 °C detected by a single wavelength pyrometer with a 700 °C through sample thickness thermal gradient was achieved. A TBC system in which the ceramic top layer deposited by air plasma spray (APS) technique was tested under such condition. Several damage/failure types were identified in comparison with samples tested under isothermal loading. A novel physical based mathematical moving boundary problem model utilizing asymptotic analysis that predicts the growth of the oxide layer on a binary bond coat system was proposed. The governing equations were discretized and solved numerically using finite difference and Newton’s iteration method respectively. Numerical results obtained from this model had shown a good qualitative agreement from comparison with the experimental studies.
49
Bhatia, Padampat Chander. "Thermal Analysis of Lithium-Ion Battery Packs and Thermal Management Solutions." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1371144911.
50
Alshatshati, Salahaldin Faraj. "Estimating Envelope Thermal Characteristics from Single Point in Time Thermal Images." University of Dayton / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1512648630005333.