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1
Ptitsin, V. E. "New Thermal Field Electron Emission Energy Conversion Method." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/35247.
Full textAbstract:
New thermal field electron emission energy conversion method for vacuum electron-optical systems
(EOS) with a nanostructured surface electron sources is offered and developed. Physical and numerical
modeling of an electron emission and transport processes for different EOS is carried out. It is shown that
at the specific configuration of electrostatic and magnetic fields in the EOS offered method permits to
realize energy conversion processes with high efficiency.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35247
2
James, William Thomas. "Electro-thermal-mechanical modeling of GaN HFETs and MOSHFETs." Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41212.
Full textAbstract:
High power Gallium Nitride (GaN) based field effect transistors are used in many high power applications from RADARs to communications. These devices dissipate a large amount of power and sustain high electric fields during operation. High power dissipation occurs in the form of heat generation through Joule heating which also results in localized hot spot formation that induces thermal stresses. In addition, because GaN is strongly piezoelectric, high electric fields result in large inverse piezoelectric stresses. Combined with residual stresses due to growth conditions, these effects are believed to lead to device degradation and reliability issues.
This work focuses on studying these effects in detail through modeling of Heterostructure Field Effect Transistors (HFETs) and metal oxide semiconductor hetero-structure field effect transistor (MOSHFETs) under various operational conditions. The goal is to develop a thorough understanding of device operation in order to better predict device failure and eventually aid in device design through modeling.
The first portion of this work covers the development of a continuum scale model which couples temperature and thermal stress to find peak temperatures and stresses in the device. The second portion of this work focuses on development of a micro-scale model which captures phonon-interactions at the device scale and can resolve local perturbations in phonon population due to electron-phonon interactions combined with ballistic transport. This portion also includes development of phonon relaxation times for GaN. The model provides a framework to understand the ballistic diffusive phonon transport near the hotspot in GaN transistors which leads to thermally related degradation in these devices.
3
Christensen, Adam Paul. "Multiscale modeling of thermal transport in gallium nitride microelectronics." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31681.
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Thesis (Ph.D)--Mechanical Engineering, Georgia Institute of Technology, 2010.<br>Committee Chair: Samuel Graham; Committee Member: Donald Dorsey; Committee Member: Douglas Yoder; Committee Member: Michael Leamy; Committee Member: Sankar Nair; Committee Member: Zhuomin Zhang. Part of the SMARTech Electronic Thesis and Dissertation Collection.
4
Hösthagen, Anders. "Thermal Crack Risk Estimation and Material Properties of Young Concrete." Licentiate thesis, Luleå tekniska universitet, Byggkonstruktion och brand, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-65495.
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This thesis presents how to establish a theoretical model to predict risk of thermal cracking in young concrete when cast on ground or an arbitrary construction. The crack risk in young concrete is determined in two steps: 1) calculation of temperature distribution within newly cast concrete and adjacent structure; 2) calculation of stresses caused by thermal and moisture (due to self-desiccation, if drying shrinkage not included) changes in the analyzed structure. If the stress reaches the tensile strength of the young concrete, one or several cracks will occur. The main focus of this work is how to establish a theoretical model denoted Equivalent Restraint Method model, ERM, and the correlation between ERM models and empirical experiences. A key factor in these kind of calculations is how to model the restraint from any adjacent construction part or adjoining restraining block of any type. The building of a road tunnel and a railway tunnel has been studied to collect temperature measurements and crack patterns from the first object, and temperature and thermal dilation measurements from the second object, respectively. These measurements and observed cracks were compared to the theoretical calculations to determine the level of agreement between empirical and theoretical results. Furthermore, this work describes how to obtain a set of fully tested material parameters at CompLAB (test laboratory at Luleå University of Technology, LTU) suitable to be incorporated into the calculation software used. It is of great importance that the obtained material parameters describe the thermal and mechanical properties of the young concrete accurately, in order to perform reliable crack risk calculations. Therefore, analysis was performed that show how a variation in the evaluated laboratory tests will affect the obtained parameters and what effects it has on calculated thermal stresses.
5
Pimenta, Paulo Vicente de Cassia Lima. "Thermomechanical simulation of continuous casting process using element based finite-volume method." Universidade Federal do CearÃ, 2014. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=13684.
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CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior<br>The continuous casting technique in the last four decades has been large used for to production of semi-finished steel. The heat transfer is major mechanism and it occurs in various steps during the continuous casting. The quality of steel is directly related to the way the heat transfer occur because the thermal variations produce mechanical loads as well as contact forces which are generated through the rollers and shake of the mold. Such factors may cause defects such as fractures or cracks in the final product if the resulting stresses and strains exceed critical values. The technique must be improved in order to reduce the appearance of defects and the production time. For this a good understanding of physical phenomena involved during the solidification process is critical. The focus of this work is to apply the EbFVM (Element based Finite-Volume Method) approach to study the effects of linear tensions unidirectionally coupled with the temperature applied to continuous casting of the steel 1013D (0,3% of carbon)
In the simulations we adopted some simplifications such as the Plane Strain and isotropic material. We also neglected the body forces contact with the rollers the liquid pressure on the walls of the steel ingot (ferrostatic pressure) and the convective effect. However despite of the simplifications adopted this work provides quantitative informations on the linear tensions accumulation that point out to areas of possible of cracks formations<br>A tÃcnica de lingotamento contÃnuo nas Ãltimas quatro dÃcadas à cada vez mais utilizada na produÃÃo de aÃo semiacabado. A transferÃncia de calor à o principal mecanismo dominante e ocorre em todas as etapas do processo. A qualidade do aÃo no lingotamento està diretamente relacionada à forma que ocorrem as trocas de calor pois as variaÃÃes tÃrmicas produzem carregamentos mecÃnicos assim como as forÃas de contato as quais sÃo geradas por intermÃdio dos rolos e da oscilaÃÃo do molde. Tais fatores podem causar defeitos como fraturas ou trincas no produto final caso as tensÃes e deformaÃÃes resultantes excedam valores crÃticos. O aprimoramento da tÃcnica tem a finalidade de evitar o surgimento de defeitos e reduzir o tempo de produÃÃo. Para isso à fundamental uma boa compreensÃo dos fenÃmenos fÃsicos envolvidos ao longo do processo de solidificaÃÃo. O foco deste trabalho à aplicar a abordagem do EbFVM (Element based Finite-Volume Method) no estudo dos efeitos das tensÃes lineares acopladas unidirecionalmente com a temperatura aplicado ao lingotamento contÃnuo do aÃo 1013D (0,3% de carbono)
Nas simulaÃÃes adotou-se algumas simplificaÃÃes com o estado plano de tensÃes e isotropia do material. Descartando-se as forÃas de corpo o contato com os rolos a pressÃo do aÃo lÃquido nas paredes do lingote (pressÃo ferrostÃtica) e o efeito convectivo. Contudo apesar das simplificaÃÃes adotadas este trabalho traz informaÃÃes quantitativas quanto a formaÃÃo do acÃmulo das tensÃes lineares que apontam para regiÃes de possÃveis formaÃÃes de trincas
6
Brdečko, Radim. "Větrací systém automobilu - porovnání vlivu okrajových podmínek na proudění z různých typů vyústek." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-417049.
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Diploma thesis deals with a research of the flow in front of three different automotive vents. The velocity field and intensity of the turbulence was measured in detail, using thermoanemometry. After that the same data was measured with PIV method and validation was performed. The difference between achieved data was investigated. The design among the vents was also investigated, because it’s fundamentally affects the air flow. The purpose of this thesis is to obtain data about the velocity field using two methods and their subsequent use to validate numerical simulations, which will be performed in the future. The diploma thesis also contains the calculation of measurement uncertainty.
7
Sathyanarayana, Aravind. "Pool and flow boiling of novel heat transfer fluids from nanostructured surfaces." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50299.
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Steadily increasing heat dissipation in electronic devices has generated renewed interest in direct immersion cooling. The ideal heat transfer fluid for direct immersion cooling applications should be chemically and thermally stable, and compatible with the electronic components. These constraints have led to the use of Novec fluids and fluroinerts as coolants. Although these fluids are chemically stable and have low dielectric constants, they are plagued by poor thermal properties. These factors necessitate the development of new heat transfer fluids with improved heat transfer properties and applicability. Computer Aided Molecular Design (CAMD) approach was used in this work to systematically design novel heat transfer fluids that exhibit significantly better properties than those of current high performance electronic coolants. The candidate fluids generated by CAMD were constrained by limiting their boiling points, latent heat of vaporization and thermal conductivity. The selected candidates were further screened using a figure of merit (FOM) analysis. Some of the fluids/additives that have been identified after the FOM analysis include C₄H₅F₃O, C₄H₄F₆O, C₆H₁₁F₃, C₄ H₁₂O₂Si, methanol, and ethoxybutane. The heat transfer performance of these new fluids/fluid mixtures was analyzed through pool boiling and flow boiling experiments. All the fluid mixtures tested showed an improvement in the critical heat flux (CHF) when compared to the base fluid (HFE 7200). A pool boiling model was developed using the phase field method available in COMSOL. Although these simulations are computationally expensive, they provide an alternate solution to evaluate several candidate fluids generated using the CAMD approach.
8
Бокоч, М. М., Георгій Васильович Кулінченко, Георгий Васильевич Кулинченко та Heorhii Vasylovych Kulinchenko. "Побудова теплового поля процесу випалювання цегли". Thesis, Сумський державний університет, 2017. http://essuir.sumdu.edu.ua/handle/123456789/65248.
Full textAbstract:
Забезпечення розвитку будівничої галузі країни залежить від динаміки будівництва нових та модернізації існуючих цегляних заводів.
При цьому основним питанням розвитку залишається енергоємність і
трудомісткість процесів виробництва цегли.
9
Wirnsberger, Peter. "Computer simulation and theoretical prediction of thermally induced polarisation." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/282988.
Full textAbstract:
In this thesis, we study the phenomenon of thermally induced polarisation using a combination of theory and computer simulation. Molecules of sufficiently low symmetry exhibit thermo-molecular orientation when subjected to a temperature gradient, leading to considerable electrostatic fields in polar liquids. Here, we first use non-equilibrium molecular dynamics simulations to study this interesting effect numerically. To this end, we propose an integration algorithm to impose a constant heat flux in simulations and show that it greatly improves energy conservation compared to a previous algorithm. We next investigate the thermal polarisation of water and find that truncation of electrostatic interactions can lead to severe artefacts, such as the wrong sign of polarisation and an overestimation of the electric field. We further show that the quadrupole-moment contribution to the electric field is significant and responsible for an inversion of its sign. To facilitate the theoretical description of electrostatic interactions, we propose a new dipolar model fluid as a perturbation of a Stockmayer fluid. Using this modified Stockmayer model, we provide numerical evidence for the recently proposed phenomenon of thermally induced monopoles. We show that the electrostatic field generated by a pair of heated/cooled colloidal particles immersed in such a solvent can be trivially described by two Coulomb charges. Finally, we propose a mean-field theory to predict the thermo-polarisation effect exhibited by our model fluid theoretically, and demonstrate near quantitative agreement with simulation results.
10
CAVALIERI, TASSIO A. "Emprego do NCNP no estudo dos TLDs 600 e 700 visando a implementação da caracterização do feixe de irradiação na instalação de BNCT do IEA-R1." reponame:Repositório Institucional do IPEN, 2013. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10565.
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19174.pdf: 31751 bytes, checksum: 7f1e1ac2bd5fcea7b8edbb1e6ba7a12b (MD5)<br>Dissertação (Mestrado)<br>IPEN/D<br>Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Wagner, Valentin Kurt [Verfasser]. "Thermal field methods of the shallow subsurface / Valentin Kurt Wagner." Karlsruhe : KIT-Bibliothek, 2014. http://d-nb.info/1052933432/34.
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Pustějovský, Michal. "Optimalizace teplotního pole s fázovou přeměnou." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-232173.
Full textAbstract:
This thesis deals with modelling of continuous casting of steel. This process of steel manufacturing has achieved dominant position not only in the Czech Republic but also worldwide. The solved casted bar cross-section shape is circular, because it is rarely studied in academical works nowadays. First part of thesis focuses on creating numerical model of thermal field, using finite difference method with cylindrical coordinates. This model is then employed in optimization part, which represents control problem of abrupt step change of casting speed. The main goal is to find out, whether the computation of numerical model and optimization both can be parallelized using spatial decomposition. To achieve that, Progressive Hedging Algorithm from the field of stochastic optimization has been used.
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OLIVEIRA, José Ricardo Ferreira. "Identificação da difusividade térmica de ligas metálicas utilizando um campo de temperatura periódico." Universidade Federal de Campina Grande, 2017. http://dspace.sti.ufcg.edu.br:8080/jspui/handle/riufcg/1488.
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Previous issue date: 2017-11-30<br>CNPq<br>A caracterização termofísica dos materiais utilizados na Engenharia é de grande
importância para realização de projetos nas mais diversas áreas de conhecimento
onde os fenômenos ligados aos processos de transferência de calor exercem um
papel fundamental. A difusividade térmica é uma propriedade termofísica
importantíssima na análise de problemas de difusão de energia térmica. Este trabalho
teve como proposta a determinação desta propriedade utilizando um campo de
temperatura periódico. Para isto, foi construído um dispositivo experimental com
princípio de funcionamento no método de Angstrom, o qual faz uso de um fluxo de
calor periódico de uma fonte controlada, gerando assim, um campo de temperatura
periódico na amostra em teste. Termopares foram instalados nas amostras para
captar os sinais de temperatura gerados pelo fluxo de calor periódico. A amplitude e
a fase destes sinais foram obtidas por meio de um software de análise gráfica. O
termopar mais próximo da fonte de calor foi adotado como referência, ao passo que a
razão de amplitudes e a defasagem, entre os sinais térmicos registrados pelos demais
termopares em relação ao registrado por àquele termopar , foram calculadas. Estes
resultados foram utilizados em modelos matemáticos para determinar a difusividade
térmica, que pode ser identificada ou atra vés da razão de amplitudes ou através da
defasagem entre os perfis de temperatura. As amostras utilizadas neste trabalho
foram de aço inox AISI 304, aço inox AISI 316 e de uma liga de memória de forma de
níquel-titânio. Os valores de difusividade térmica identificados para estes materiais,
quando foram comparados com valores disponíveis na literatura, obtiveram uma boa
concordância, tendo em vista a faixa de incerteza apresentada.<br>Thermophysical characterization of materials used in engineering is very important for
realization of projects in the most diverse areas of knowledge where the phenomena
related to the process of heat transfer play an important role. Thermal diffusivity is a
very important thermal property on the analysis of problems of diffusion of thermal
energy. This work proposes the determination of this property using a periodic
temperature field. For this, an experimental device was built with principle of operation
in Angstrom’s method, which makes use of a periodic heat flow from a controlled
source, thereby generating a periodic temperature field in the test sample.
Thermocouples were installed on the samples for capture of signals generated by the
periodic heat flow. Amplitude and phase of these signals were obtained by means of
graphic analysis software. The thermocouple closest to the heat source was adopted
as reference, and the ratio and phase lag, between the thermal signals registered by
other thermocouples in relation to that registered by that thermocouple, were
calculated. These results were utilized in mathematical models to determine the
thermal diffusivity, whose identification can be performed either through the amplitude
ratio or through the phase lag between the temperature profiles. Samples utilized in
this work were stainless steel AISI 304, stainless steel AISI 316 and a shape memory
alloy of nickel-titanium. Identified values of thermal diffusivity of these materials, when
compared whit values available in literature obtained a good agreement, considering
the range of uncertainty presented.
14
Ali, Salamat. "Specific heat measurements using the A.C. technique on the chevrel phase superconductor Pb(_1-x)Gd(_x)Mo(_6)S(_8) in high magnetic fields." Thesis, Durham University, 1996. http://etheses.dur.ac.uk/5284/.
Full textAbstract:
We have developed a probe to measure specific heat of Gd-doped PbMo(_6)S(_8), at low temperatures in high magnetic fields up to 12.5 T using a heat pulse method and an a.c. technique. Comparison between these heat capacity measurements and transport measurements provides critical complimentary information about fundamental thermodynamic properties and granularity m superconductors. We have used a tiny, robust, highly sensitive and broadly field independent Cemox thermometer (CX-1030), eliminating the use of bulky gas thermometry or capacitance thermometry. The diameter of the probe is 20 min which facilitates use in our 17 T high field magnet and in free-standing cryostats. Experiments include accurate measurement of temperature oscillations of 10(^-6)K. The measurements and analysis of the data were made fully computer controlled. Measurements on Cu and NbTi demonstrate we achieved an accuracy of ±0.2 K in temperature and a typical accuracy of -10% m the specific heat values quoted. Gd-doped Lead Chevrel phase material Pb(_1-x)Gd(_x)Mo(_6)S(_8) has been fabricated in a controlled environment using simple sintering methods and a Hot Isostatic Press (HIP) operating at pressures up to 2000 atmospheres. Cp has been measured and the properties of the materials including B(_c2)(T) have been determined. HIP processing improves the materials, increasing Tc ~ 15 K and B(_c2)(0) ~ 60 T. These values are amongst the best reported values for the Chevrel phase materials to date. I am personally responsible for taking all the data and its analysis. The modification of the probe were also undertaken by me. The fabrication of the samples was not my work
15
Yarimpabuc, Durmus. "Numerical Simulation Of Thermal Convection Under The Influence Of A Magnetic Field By Using Solenoidal Bases." Phd thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613393/index.pdf.
Full textAbstract:
The effect of an imposed magnetic field on the thermal convection between rigid plates heated from below under the influence of gravity is numerically simulated in a computational domain with periodic horizontal extent. The numerical technique is based on solenoidal basis functions satisfying the boundary conditions for both velocity and induced magnetic field. The
expansion bases for the thermal field are also constructed to satisfy the boundary conditions. The governing partial differential equations are reduced to a system of ordinary differential equations governing the time evolution of the expansion coefficients under Galerkin projection onto the subspace spanned by the dual bases. In the process, the pressure term in the momentum equation is eliminated. The system validated in the linear regime is then used for some numerical experiments in the nonlinear regime.
16
Castellví, Fernández Quim. "Non-focal non-thermal electrical methods for cancer treatment." Doctoral thesis, Universitat Pompeu Fabra, 2017. http://hdl.handle.net/10803/586217.
Full textAbstract:
Most physical ablation modalities for cancer treatment are focal and are based on thermal damage. Despite their regular clinical use as an alternative to surgical resection, their thermal principle of operation entails risks regarding the preservation of neighboring vital structures, such as large vessels, critical ducts or nerves. In addition, being focal, their use is unpractical in cases where multiple nodules are present or tumors are difficult to reach with the applicators.
This thesis explores non-thermal electrical treatments which can be applied in a non-focal manner. Two treatments have been investigated: the first treatment, proposed by others a few years ago, is based on the permanent application of low magnitude alternating electric fields through surface electrodes. Here, this treatment has been in vivo studied to evaluate its efficacy as well as to discern whether it is non-thermally mediated. The second electrical treatment is based on the electroporation phenomenon and targets liver tumor nodules.
Electroporation-based therapies employ brief high magnitude electric fields. These pulsed fields, alone or in combination with chemotherapeutic drugs, are able to kill cells by increasing their membrane permeability. Current electroporation-based therapies for internal tumors are local and are delivered through needle-shaped electrodes. Rather than using needle electrodes to treat liver tumors, here it is explored a novel treatment in which large plate electrodes are used to deliver the field across the whole liver in a non local fashion. The treatment aims at simultaneously destroying all tumors while preserving healthy tissue. Its efficacy is based on selectively enhancing the electric field over the tumors by infusing a solution with high electrical conductivity.
The proposed treatment for liver tumors requires a high performance generator which is not currently available. The work presented here includes the design of a new generator topology able to fulfill the requirements.<br>La majoria del mètodes físics d'ablació tumoral es basen en produir dany tèrmic de manera focalitzada. Tot i ser considerats una alternativa habitual a la resecció quirúrgica, el principi tèrmic de funcionament, comporta un risc per la preservació d'estructures vitals adjacents a la zona de tractament, tals com grans vasos o nervis. A més, el fet de ser focals, fa impracticable la seva aplicació en cas de múltiples nòduls o tumors de difícil accés.
Aquesta tesi explora tractaments elèctrics no basats en temperatura, capaços de ser aplicats de manera no focal. S'han investigat dos tractaments: El primer, proposat per altres fa pocs anys, està basat en aplicar permanentment camps elèctrics alterns de baixa magnitud a través d'elèctrodes superficials. Aquí, aquest tractament s'ha estudiat in vivo tant per avaluar la seva eficàcia com per discernir si aquesta resideix en la temperatura. El segon tractament es basa en el fenomen d'electroporació i persegueix el tractament de nòduls hepàtics. En els tractaments basats en electroporació, s’apliquen breus camps elèctrics de gran magnitud per tal de permeabilitzar la membrana cel·lular. Això permet la penetració d’agents quimioterapèutics o produeix directament la mort cel·lular. En lloc d'utilitzar, com és habitual, agulles per tal d'aplicar el tractament, aquí s'explora tractar tot el fetge de forma no localitzada, fent servir grans elèctrodes plans i paral·lels. Utilitzant solucions d'alta conductivitat elèctrica, es pretén magnificar selectivament el camp elèctric sobre els tumors, sent així capaços de destruir tots els tumors i alhora preservar el teixit sà.
El tractament proposat per els tumors hepàtics, requereix d'un equip generador actualment no disponible. El presentat treball inclou el disseny d'una nova topologia de generadors capaç de complir amb els requisits.
17
Moreau, Denis. "Etude de mélange de jets gazeux dans une chambre de combustion." Rouen, 1988. http://www.theses.fr/1988ROUES043.
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Etude expérimentale du mélange de plusieurs jets ronds gazeux dans différents types de configuration (doublet, triplet, quintriplet, multitriplet). Emploi de deux méthodes de diagnostic: visualisation par tomographie flash (étude qualitative de la structure des jets avant et après l'interaction) et méthode thermique (évolution du mélange par la mesure des caractéristiques du champ de température)
18
Beyers, Johannes Henricus Meiring. "A finite volume method for the analysis of the thermo-flow field of a solar chimney collector." Thesis, Stellenbosch : Stellenbosch University, 2000. http://hdl.handle.net/10019.1/51568.
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Thesis (MEng)--University of Stellenbosch, 2000.<br>ENGLISH ABSTRACT: This study investigates the implementation of the finite volume numerical
method applicable to non-orthogonal control volumes and the application of
the method to calculate the thermo-flow field within the collector area of a
solar chimney power generating plant. The discretisation of the governing
equations for the transient, Newtonian, incompressible and turbulent fluid
flow, including heat transfer, is presented for a non-orthogonal coordinate
frame. The standard k - E turbulence model, modified to include rough
surfaces, is included and evaluated in the method.
An implicit solution procedure (SIP-semi implicit procedure) as an alternative
to a direct solution procedure for the calculation of the flow field on nonstaggered
grids is investigated, presented and evaluated in this study. The
Rhie and Chow interpolation practice was employed with the pressurecorrection
equation to eliminate the presence of pressure oscillations on nonstaggered
grids.
The computer code for the solution of the three-dimensional thermo-flow
fields is developed in FORTRAN 77. The code is evaluated against simple
test cases for which analytical and experimental results exist. It is also
applied to the analysis of the thermo-flow field of the air flow through a
radial solar collector.
KEYWORDS:
NUMERICAL METHOD, FINITE VOLUME, NON-ORTHOGONAL, k+-e
TURBULENCE MODEL, SIP<br>AFRIKAANSE OPSOMMING: Die studie ondersoek die implementering van 'n eindige volume numeriese
metode van toepassing op nie-ortogonale kontrole volumes asook die
toepassing van die metode om die termo-vloei veld binne die kollekteerder
area van 'n sonskoorsteen krag aanleg te bereken. Die diskretisering van die
behoudsvergelykings vir die tyd-afhanlike, Newtonse, onsamedrukbare en
turbulente vloei, insluitende hitteoordrag, word beskryf vir 'n nie-ortogonale
koordinaatstelsel. Die standaard k - E turbulensiemodel, aangepas om growwe
oppervlakrandvoorwaardes te hanteer, is ingesluit en geevalueer in die studie.
'n Implisiete oplossings metode (SIP-semi implisiete prosedure) as alternatief
vir 'n direkte oplossingsmetode is ondersoek en geimplimenteer vir die
berekening van die vloeiveld met nie-verspringde roosters. 'n Rhie en Chow
interpolasie metode is gebruik tesame met die drukkorreksie-vergelyking ten
einde ossilasies in die drukveld in die nie-verspringde roosters te vermy.
Die rekenaarkode vir die oplossing van die drie dimensionele termo-vloeiveld
is ontwikkel in FORTRAN 77. Die kode is geevalueer teen eenvoudige
toetsprobleme waarvoor analitiese en eksperimentele resultate bestaan. Die
kode IS ook gebruik om die termo-vloeiveld binne 'n radiale son
kollekteerder te analiseer.
SLEUTELWOORDE:
NUMERIESE METODE, EINDIGE VOLUME, NIE-ORTOGONAAL, k - E
TURBULENSIE MODEL, SIP
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Dai, Wenhua. "Large signal electro-thermal LDMOSFET modeling and the thermal memory effects in RF power amplifiers." Connect to this title online, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1078935135.
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Thesis (Ph. D.)--Ohio State University, 2004.<br>Title from first page of PDF file. Document formatted into pages; contains xix, 156 p.; also includes graphics (some col.). Includes bibliographical references (p. 152-156).
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Mehra, Bineet. "Design and optimisation of innovative electronic cooling heat sinks with enhanced thermal performances using numerical and experimental methods." Thesis, Ecole nationale supérieure Mines-Télécom Lille Douai, 2019. http://www.theses.fr/2019MTLD0005/document.
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Cette thèse de doctorat s’intéresse aux mécanismes d’amélioration des transferts dans des géométries de dissipateurs thermiques à plaques et ailettes. Une première partie est consacrée à l’étude d’une configuration académique à l’aide de simulations numériques visant à obtenir une amélioration du transfert de chaleur conjugué en modifiant uniquement par des découpes la forme géométrique des ailettes planes conductrices. Une analyse locale approfondie de l’écoulement et des champs thermiques a été effectuée avec notamment le principe de synergie locale, des champs de vitesse et de gradients thermiques, pour comprendre l’effet des modifications géométriques. Ce mémoire présente également le développement de dissipateurs aux performances thermo-aérauliques augmentées pour des applications de refroidissement de coffrets électronique embarqués. L’intensification des transferts thermiques est obtenue par la génération d’écoulements secondaires qui provoquent un brassage de fluide et réduisent la résistance thermique à la paroi en perturbant le développement de la couche limite thermique. Différentes configurations de dissipateurs avec deux types de générateurs d’écoulements secondaires, paires d’ailettes Delta et protrusions, ont été étudiées numériquement, en employant une modélisation de type « RANS ». Les performances thermo-aérauliques des géométries munies de générateurs de vorticité ont été comparées à celle d’un dissipateur thermique de référence « lisse ». Des prototypes ont également été fabriqués et testés sur un banc expérimental spécifiquement développé pour réaliser des mesures des performances globales en termes de puissance thermique et de pertes de charge. Les résultats expérimentaux et numériques ont été confrontés afin de qualifier les simulations réalisées. Par la suite, une étude d’optimisation employant l’analyse factorielle Taguchi a été utilisée afin d’optimiser les paramètres géométriques des dissipateurs retenus. Deux fonctions objectif ont été considérées : la maximisation du facteur de performance thermique à iso puissance de ventilation (PEC) et la réduction de la température moyenne de paroi du dissipateur par rapport au cas de référence. L’analyse des performances thermo-aérauliques globales des géométries étudiées a été complétée par une analyse qualitative locale des champs thermiques et d’écoulement notamment avec le principe de synergie<br>This doctoral thesis focuses on mechanisms of heat transfer enhancement in plate and fin heat sink geometries. First part of the thesis is dedicated to study an academic configuration using numerical simulations to achieve an improvement in conjugate heat transfer by modifying only the geometrical shape (through punching) of the conductive plane fins. An in-depth local analysis of the flow and thermal fields was carried out with the local synergy principle, velocity and thermal gradients, to understand the effect of geometric modifications. This thesis also presents the development of heat sinks with increased thermo-hydraulic performance for on-board electronic box cooling applications. The intensification of the heat transfer is obtained by the generation of secondary flows which cause an intensive mixing of fluid and reduces the thermal resistance to the wall by disrupting the development of the thermal boundary layer. Different heat sink geometries with two types of secondary flow generators : delta winglet pair and protrusions were numerically studied using RANS approach. The thermo-hydraulic performances of the geometries equipped with vortex generators were compared with that of a smooth reference heat sink. The prototypes were also manufactured and tested on an experimental bench specifically designed to perform global performance measurements in terms of thermal power and pressure drops. Experimental and numerical results were compared to qualify the simulations performed. Subsequently, an optimization study using Taguchi factorial analysis was used to optimize the geometrical parameters of the chosen dissipaters. Two objective functions were considered : maximization of either iso-pumping power performance criteria (PEC) or average wall temperature of the dissipaters compared to the reference case. The global thermo-hydraulic performance analysis of the studied geometries was completed by a qualitative analysis of local flow and thermal fields, in particular with the local field synergy principle
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Grmela, Petr. "Analýza teplotního pole u asynchronního stroje." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2010. http://www.nusl.cz/ntk/nusl-218763.
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This thesis is dealing with thermal fields and the possibilities of their solution by a finite element method. Thereinafter thesis describe assembling a 3D model of induction machine with known parameters, and solving thermal field of the model by Ansys Workbench program and verification of these results by practical measuring on real machine.
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Troussaut-Bertrand, Francine. "Etude du KH2PO4 au voisinage du point tricritique : mesures de biréfringence sous pression et détermination des coefficients d'électrostriction." Grenoble 1, 1987. http://www.theses.fr/1987GRE10039.
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Mise en evidence de la possibilite d'etude des variations du parametre d'ordre, en fonction de la pression, de la temperature et du champ electrique, a partir de mesures de birefringence; confirmation de l'ordre de transition de rbh::(2)po::(4) et etude du diagramme de phases 3d de kh::(2)po::(4) au voisinage d'un point tricritique. Etude des proprietes electromecaniques de kh::(2)po::(4) par une nouvelle technique de diffraction simultanee neutron-gamma, dans le but de preciser la relation entre les variations du parametre d'ordre et les anomalies de la dilatation au voisinage de la transition; interpretation qualitative par un modele de type slater
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Khlifi, Imad. "Optimisation of optical methods for strain field measurements dedicated to the characterisation of the fracture behaviour of refractories : Application to magnesia based materials." Thesis, Limoges, 2019. http://www.theses.fr/2019LIMO0123.
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Les briques de magnésie-spinelle et magnésie-hercynite sont fréquemment utilisées dans les fours rotatifs de cimenterie pour leur tenue aux chocs thermiques venant d’une résistance accrue à la propagation de fissures conférée par leur microstructure. Les réseaux de microfissures résultant du différentiel de dilatation thermique entre la matrice magnésienne et les agrégats de spinelle/hercynite favorisent l'activation de mécanismes dissipatifs d’énergie au sein de la zone d’élaboration de la rupture (FPZ) lors d’un chargement mécanique. Dans cette étude, le comportement à la rupture de matériaux modèles à base de magnésie a été étudié en couplant une méthode de corrélation d'images numériques (2P-DIC) adaptée aux problématiques de fissuration avec l’essai de « Wedge Splitting » (WST). Le couplage judicieux de ces méthodes innovantes a fourni des mesures précises des propriétés de rupture et a mis en évidence des mécanismes de rupture caractéristiques, tels que la bifurcation de fissures. L’étude des relations propriété-microstructure a démontré l’impact des microfissures introduites volontairement au sein du matériau sur le comportement thermomécanique de la magnésie-spinelle et la magnésie-hercynite. Malgré des propriétés élastiques et dilatométriques assez similaires entre les inclusions de spinelle et d’hercynite, des mécanismes de microfissuration différents ont été observés, en particulier pour la magnésie-hercynite. En effet, la diffusion entre la magnésie et l’hercynite pendant le frittage a conduit à la formation de solutions solides de spinelles autour des agrégats d'hercynite. Ces solutions solides ont contribué à leur tour à la création de nombreuses microfissures fines par l’effet d’un différentiel de dilatation thermique avec la magnésie. Initialement présents dans la microstructure, les réseaux de microfissures favorisent l’augmentation de l'énergie de rupture des matériaux modèles pendant le WST. De plus, l’analyse des champs de déformation mesurée par 2P-DIC a révélé d’importantes bifurcation de la fissure principale pour les matériaux magnésie-hercynite. Le couplage de la 2P-DIC avec l’essai du WST a démontré que les réseaux de microfissures favorisaient le développement de la FPZ, qui induisait à son tour une augmentation notable de l’énergie de rupture. Dans une approche affinée des courbes-R, des énergies de rupture effectives ont été calculées à l'aide des longueurs de fissure mesurées par 2P-DIC. Cela a permis d'établir des liens étroits entre le développement de la FPZ et une résistance accrue à la propagation de la fissure. Les tendances observées à température ambiante lors des essais de WST ont été confirmées à l’aide d’essais de cyclage dans un nouveau banc de chocs thermiques<br>Magnesia-spinel and magnesia-hercynite bricks destined for thermal shock applications in cement rotary kilns often show an enhanced crack propagation resistance due to an engineered microstructure design. In these materials, microcrack networks resulting from the thermal expansion mismatch between magnesia matrix and spinel/hercynite aggregates promote the activation of energy dissipating mechanisms within the so-called Fracture Process Zone (FPZ) during loading. In this research, the fracture behaviour of magnesia-based model materials was investigated by coupling a refined Digital Image Correlation method (2P-DIC) with the Wedge Splitting Test (WST). The coupling of these advanced characterisation methods has proven to be very effective in measuring important fracture parameters accurately and in highlighting characteristic fracture mechanisms, such as crack-branching. The investigation of microstructure-property relationships underlined the impact of thermally induced microcracks on the thermomechanical behaviour of magnesia-spinel and magnesia-hercynite materials. Despite the rather similar elastic and dilatometric properties of spinel and hercynite single constituents, peculiar microcracking patterns were observed, especially in magnesia-hercynite. In fact, extensive diffusion between magnesia and hercynite during sintering led to the formation of spinel solid solutions around hercynite aggregates. As a result of thermal expansion mismatch with magnesia, these solid solutions contributed to creating numerous fine microcracks confined within the diffusion zone. Initially present within the microstructure, microcrack networks promote an increase of the specific fracture energy during WST experiments. Moreover, the analysis of strain fields measured by 2P-DIC revealed extensive crack branching for magnesia-hercynite materials. In essence, 2P-DIC and WST measurements showed that microcrack networks promoted the development of the FPZ, which in turn induced higher fracture energies. In a refined R-curve approach, effective fracture energies were calculated using crack lengths measured by 2P-DIC, which helped establish strong links between FPZ development and an enhanced crack propagation resistance. The tendencies observed at room temperature during WST experiments were confirmed during thermal cycling experiments using a novel thermal shock device
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Haratek, Jiří. "Výpočet rozložení teplotního pole v elektrickém stroji." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2017. http://www.nusl.cz/ntk/nusl-318865.
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This diploma thesis deals with methods used to determine the temperature field distribution within an electric machine. The first part is focused on methods of temperature measurement, generation and transfer of the thermal energy within the electric machine, asynchronous motor in particular. The thesis describes classical methods of temperature measurement and it also deals with ANSYS Workbench finite element method for thermal analysis of the motor. The final part of the thesis is focused on a comparation of all discussed methods with respect to results of thermal test for real asynchronous motor and concludes the most proper method.
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Ayvazyan, Vigen. "Etude de champs de température séparables avec une double décomposition en valeurs singulières : quelques applications à la caractérisation des propriétés thermophysiques des matérieux et au contrôle non destructif." Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR14671/document.
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La thermographie infrarouge est une méthode largement employée pour la caractérisation des propriétés thermophysiques des matériaux. L’avènement des diodes laser pratiques, peu onéreuses et aux multiples caractéristiques, étendent les possibilités métrologiques des caméras infrarouges et mettent à disposition un ensemble de nouveaux outils puissants pour la caractérisation thermique et le contrôle non desturctif. Cependant, un lot de nouvelles difficultés doit être surmonté, comme le traitement d’une grande quantité de données bruitées et la faible sensibilité de ces données aux paramètres recherchés. Cela oblige de revisiter les méthodes de traitement du signal existantes, d’adopter de nouveaux outils mathématiques sophistiqués pour la compression de données et le traitement d’informations pertinentes. Les nouvelles stratégies consistent à utiliser des transformations orthogonales du signal comme outils de compression préalable de données, de réduction et maîtrise du bruit de mesure. L’analyse de sensibilité, basée sur l’étude locale des corrélations entre les dérivées partielles du signal expérimental, complète ces nouvelles approches. L'analogie avec la théorie dans l'espace de Fourier a permis d'apporter de nouveaux éléments de réponse pour mieux cerner la «physique» des approches modales.La réponse au point source impulsionnel a été revisitée de manière numérique et expérimentale. En utilisant la séparabilité des champs de température nous avons proposé une nouvelle méthode d'inversion basée sur une double décomposition en valeurs singulières du signal expérimental. Cette méthode par rapport aux précédentes, permet de tenir compte de la diffusion bi ou tridimensionnelle et offre ainsi une meilleure exploitation du contenu spatial des images infrarouges. Des exemples numériques et expérimentaux nous ont permis de valider dans une première approche cette nouvelle méthode d'estimation pour la caractérisation de diffusivités thermiques longitudinales. Des applications dans le domaine du contrôle non destructif des matériaux sont également proposées. Une ancienne problématique qui consiste à retrouver les champs de température initiaux à partir de données bruitées a été abordée sous un nouveau jour. La nécessité de connaitre les diffusivités thermiques du matériau orthotrope et la prise en compte des transferts souvent tridimensionnels sont complexes à gérer. L'application de la double décomposition en valeurs singulières a permis d'obtenir des résultats intéressants compte tenu de la simplicité de la méthode. En effet, les méthodes modales sont basées sur des approches statistiques de traitement d'une grande quantité de données, censément plus robustes quant au bruit de mesure, comme cela a pu être observé<br>Infrared thermography is a widely used method for characterization of thermophysical properties of materials. The advent of the laser diodes, which are handy, inexpensive, with a broad spectrum of characteristics, extend metrological possibilities of infrared cameras and provide a combination of new powerful tools for thermal characterization and non destructive evaluation. However, this new dynamic has also brought numerous difficulties that must be overcome, such as high volume noisy data processing and low sensitivity to estimated parameters of such data. This requires revisiting the existing methods of signal processing, adopting new sophisticated mathematical tools for data compression and processing of relevant information.New strategies consist in using orthogonal transforms of the signal as a prior data compression tools, which allow noise reduction and control over it. Correlation analysis, based on the local cerrelation study between partial derivatives of the experimental signal, completes these new strategies. A theoretical analogy in Fourier space has been performed in order to better understand the «physical» meaning of modal approaches.The response to the instantaneous point source of heat, has been revisited both numerically and experimentally. By using separable temperature fields, a new inversion technique based on a double singular value decomposition of experimental signal has been introduced. In comparison with previous methods, it takes into account two or three-dimensional heat diffusion and therefore offers a better exploitation of the spatial content of infrared images. Numerical and experimental examples have allowed us to validate in the first approach our new estimation method of longitudinal thermal diffusivities. Non destructive testing applications based on the new technique have also been introduced.An old issue, which consists in determining the initial temperature field from noisy data, has been approached in a new light. The necessity to know the thermal diffusivities of an orthotropic medium and the need to take into account often three-dimensional heat transfer, are complicated issues. The implementation of the double singular value decomposition allowed us to achieve interesting results according to its ease of use. Indeed, modal approaches are statistical methods based on high volume data processing, supposedly robust as to the measurement noise
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Zang, Zhong-Yuan, and 臧忠元. "The Simulation of Thermal Flow Field in LPCVD Chamber Using Parallel DSMC Method." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/73951074901214840920.
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碩士<br>國立交通大學<br>機械工程系<br>90<br>In this thesis, the parallelization is applied to DSMC method by utilizing chain partitioner. The computation is carried out on a PC cluster system consisting of nine processors. The preliminary results are compared with the Hsiao’s single-processor results [5], to demonstrate the advantage of parallelization. The computational domain is decomposed according to the same number of simulated particles in each processor. When a parallel program is executed on a distributed memory system, the speedup may not be proportional linearly to the number of processor. The computing load in each processor becomes lighter by increasing the processor number, whereas the communication load becomes heavier at the same time. Therefore the efficiency becomes worse with an increment of processor number. The parametric studies are based on the variations of particle number, computing domain size and time step, respectively. The better speedup and efficiency can be achieved when the particle number and computational domain increase. The performance does not depend on time step in present case because the variation of particle number is not severe.
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Shih, Man-Wen, and 施嫚雯. "Measurement of energy loss of magnetic microstructures under alternating magnetic field by thermal deflection method." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/00521111009361226295.
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Chang, Cheng-Chi, and 張鉦淇. "A study on multi-branch channel thermal mixing flow by Lattice Boltzmann method and field synergy principle." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/41790448978282811749.
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碩士<br>國立成功大學<br>機械工程學系碩博士班<br>95<br>This study applies the Lattice Method to simulate low Reynolds number, steady-state and 2-D incompressible thermal mixing flow in a multi-branch channel. The pressure difference of inlet and outlet is set appropriately so that the fluid particles can be driven. To accelerate the efficiency of the thermal mixing, the distinct shapes of obstacles are inserted into the straight wall being in back of the multi-branch channel. After the fluid particles bomb into the obstacles, the variation of the flow and temperature field then generated.
When the fluid particles flow past the inserted obstacles in two parallel plates, the perturbation caused by the impact will affect the heat transfer of the flow. This type of flow is associated with the fabrication design along with the effect of heat transfer so that the application is very important. If we consider the flow with temperature difference mix inside the channel, the geometry of the channel will have great effect on thermal characteristics.
We place numbers of obstacles being in the form of wavy-like and touch down circle in the back straight part of multi-branch channel. When fluid particles flow past these obstacles, the recirculation regions are raised due to the pressure drag. The recirculation region impact on the temperature distribution magnificently and hasten the efficiency of the thermal mixing.
Taking another view of field synergy principle specify the thermal mixing problem. The increase of intersection angle will accelerate the heat exchange rate between high-temperature and low-temperature fluid particles.
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Hsiao, Chi-Hong, and 蕭啟宏. "The Simulation of Thermal Flow Field and Film Deposition in Vertical Rotating Substrate for LPCVD Using DSMC Method." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/00031111807177172417.
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碩士<br>國立交通大學<br>機械工程系<br>89<br>This thesis analyzes the flow and thermal field in a vertical LPCVD chamber with rotating susceptor by using DSMC method. It aims at the remodeling of boundary conditions to eliminate the shortcoming in Dei’s work [1], the extra design parameters, such as inlet tube diameter, gravity, and side-wall temperature and an application of parallel computation. For the different design parameters, the predicted results show that a higher average deposition rate and better uniformity can be achieved by shortening the distance between inlet and substrate. It leads to a better deposition rate but a poorer uniformity by increasing the operating pressure, inlet flow, substrate temperature and side wall temperature, respectively. Putting an annular baffle, whose width is equal to the one of outlet area in inlet area, results in a better uniformity but a poorer deposition rate. Rotating the susceptor will improve the uniformity without affecting the deposition rate. Increasing the percentage of reactant, Cu, can raise the deposition rate without affecting the uniformity. The gravity orientation has insignificant effect on the uniformity and deposition rate of LPCVD. The parallelization of DSMC is done in output process only. The saving times, 0.23 second and 0.97 second, are for 4-inch and 8-inch wafer computations, respectively.
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Yang, Pao-Ming, and 楊寶明. "Analysis of Thermal Flow Field and Film Deposition in Vertical Rotating Substrate for LPCVD Using the DSMC Method." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/25103700096549347988.
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碩士<br>國立交通大學<br>機械工程系<br>87<br>This thesis analyzes the flow and thermal field in a vertical LPCVD chamber with rotating susceptor by using the DSMC method. Complying with the requirements of project "Development of Cu-CVD Technology and Fabrication" supported by the National Science Council of Taiwan, this work aims at exploring the Cu-deposition characteristics of various operating parameters, including the sticking coefficient (Sc), activation energy, temperature distribution on the susceptor, and different carrier gases. For the simulation of using different carrier gas, it quarries the difference between the gases with rotational energy and without any internal mode. For being closer to real situation, the simulation of chemical reaction including the by-products is also carried out.
The predicted results show that the uniformity becomes worse and the deposition rate becomes greater with an increase of Sc. For the case of higher activation energy 4.0 kcal/mole, it belongs to the reaction control regime and can obtain an even film. If the masses for two carrier gases are similar, the one with considering rotational energy has the faster deposition rate because of the greater heat transfer capability. The faster deposition rate can be achieved by using a lighter carrier gas such that the precursor can be easier to reach the substrate. The deposition rate obtained by the by-product model in the present study is about 38.0 nm/min, which is close to the one obtained by experiment. The uniformity of film thickness is found sensitive to the distribution of temperature. Finally, a comparison of using DSMC and CFX-4.1 methods is given. It is found that some of the special phenomena in rarefied gas can not be reproduced by the CFX method, even it sets the slip condition at the solid boundary. However, both methods can obtain the similar trends in the transition flow regime.
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Hsu, Yao-An, and 許燿安. "Prediction of Early Hydration Behavior of Concrete by Maturity Method and Finite Element Analysis of Early Thermal Field for Mass Concrete." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/y8nahd.
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碩士<br>國立臺灣大學<br>土木工程學研究所<br>106<br>The strength and stiffness of concrete come from the C-S-H gel produced by hydration reaction of cement, pozzolanic material and mixing water. Hydration reaction is exothermic chemical reaction. 1 to 3 days after concrete placement is the most severe stage of hydration reaction, and this period is also the fastest stage of concrete temperature rise. Because of its large size and poor thermal conductivity of concrete, mass concrete has heat storage at the center at the early age. Moreover, the high temperature environment stimulates the rate of hydration reaction, so that the temperature difference between the center and surface of the concrete will increase rapidly to form larger thermal stress, resulting in the early cracks of concrete. Therefore, early temperature prediction and control of mass concrete is the topic to be discussed in this study.
In this study, the finite element method were used to simulate the temperature field of the early age of mass concrete in ANSYS. The early hydration reaction was predicted through the experimental results of concrete adiabatic temperature rise test, and the unit volume heat generation rate of concrete, which could simultaneously consider the age and temperature effects, was derived by the maturity method. It was hoped that the heat load given to the model during the finite element analysis could adjust the heat generation rate with time and temperature to conform to the actual hydration behavior. Moreover, this study gave another heat load of the model which could only be adjusted the hydration rate with time to analyze the temperature field. In this study, the above two kinds of heat loads were respectively used to do the finite element analysis of the early temperature field of the mass concrete specimen in the field, and this study also compared the difference between the two methods.
In addition to the development of concrete hydration, initial temperature, ambient temperature, thermal conductivity and heat preservation measures of concrete will also affect the development of the early temperature field of the mass concrete. In this study, the effects of above variables on center temperature, side temperature and center-side temperature difference were analyzed by finite element analysis. It is recommended that mass concrete should be avoid high temperature pouring, be avoid pouring in a low temperature environment and be arranged insulation measures on the surface.
Moreover, by collecting the data of adiabatic temperature rise test at home and abroad for nearly 15 years, the variation of hydration behavior of concrete at the early age was discussed with the establishment of the database of hydration parameters to provide reference and suggestions for establishing the prediction formula of the degree of hydration in the future.
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Sun, Yun-Chiang, and 孫運強. "Analysis of Thermal Flow Field in Vertical Rotating Injector Low Pressure Chemical Vapor Deposition Reactor Using the Directs Simulation Monte Carlo Method." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/47907890823565153955.
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碩士<br>國立交通大學<br>機械工程研究所<br>86<br>This thesis applies a numerical technique, DSMC, to simulate the thermal flow field in a vertical low-pressure Cu-CVD reactor. It is incorporated with a project supported by a manufacturer and the National Science council, ROC, under a contract, NSC87-2622-E-009-004. The main purpose is to provide the simulation data as a reference for designing the reacting chamber. According to the requirement of the manufacturer, the effects of rotating injector with fixed suscepter are investigated numerically in this thesis. The parametric studies are based on the changes in physical conditions, such as reactor pressure, temperature of substrate, inlet flow rate, angular velocity of rotating injector and carrier gas. The effect of distance between the injector and substrate is also studied. In the meantime, the influence of two different chemical reaction models on the surface deposition of substrate is considered as well.
The results show that a good deposition uniformity for the angular velocities within the domain of 10 to 20 rpm can be achieved. When the reactor pressure increases, the deposition rate increases but the uniformity becomes worse. Increasing the percentage of reactant in precursor can raise the deposition rate more effectively than increasing the reactor pressure. It can also obtain a better deposition uniformity. A higher deposition rate and a better deposition uniformity can be reached by shorting the distance between the injector and substrate. However, an enough distance should be reserved to let the robot arm be able to deliver the wafer into and out from the reacting chamber. When a carrier gas with lower molecular weight is used, a higher deposition rate but with a worse deposition uniformity is found. The high temperature of substrate results in a high temperature in the injector, therefore, the temperature of suscepter suggested not too high in order not to make the reactant deposition on the its aperture to block the transportation of carrier gas and reactants.
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Lin, Chen-Yun, and 林辰昀. "Analysis of the Thermal and Fluid Flow Fields under Multiple-Nozzle Impingement Jet Cooling with Taguchi Method." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/k9d539.
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碩士<br>國立虎尾科技大學<br>車輛工程系碩士班<br>101<br>In the era of technological progress increasingly, electronic components develop towards compact size and precision. As the power of the electronic product quickly raises, it accompanies with a large amount of heat generation. The high heat generation effect significantly shortens the life of electronic components. Therefore developing the cooling module has become an important topic. Among these studies, the impingement jet integrated with the heat sink with excellent thermal conductivity properties provides a large heat reduction effect for local rapid cooling .
In this study, the thermal and flow field phenomena for a heat sink with constant heat input under multiple-nozzle impingement jet cooling are investigated with computational fluid dynamics software FLUENT combined with computer aided design software SolidWorks. Taguchi method is also utilized to analyze the effects of nozzle inlet velocity, number of nozzles, jet angle and distance from nozzle to the top heat sink. The results show that increase of the nozzle inlet velocity can effectively reduce the thermal resistance of heat sink. However with the increase in flow rate, decrease of the magnitude of the thermal resistance becomes slowly. Distance from the nozzle to the top of the heat sink too far or too close will diminish the cooling effect. According to the numerical simulations, a better choice is between 48~64mm. In terms of the jet angle, controlling the angle for jet flow towards the middle point between the center and the edge of the wafer is the best choice. Investigation of the nozzle number, four-nozzle type can effectively dissipate heat when the angle is near 90 degrees. The jet flows create circulations around the central area when the jet flows towards the center of heat sink. This phenomenon results in a higher thermal resistance. Overall, number of nozzles and jet-angle must be considered at the same time to obtain a better cooling effect. According to Taguchi method analyses, the optimal parameters are A1B2C3D4, and the effect of parameter is ranked as jet velocity>jet>angle>impingement distance>number of nozzle.
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Hung, Kuo-Shu, and 洪國書. "Numerical Method for Analysis of Thermal and Flow Fields of Compressible Flow in an Enclosure with Periodically Moving Boundary." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/77261804017888908369.
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博士<br>大同大學<br>機械工程學系(所)<br>94<br>The aim of this thesis is to develop a numerical method for analysis of thermal and flow fields of compressible flow in an enclosure with periodically moving boundary. The combined influence of the partitions, movement of the walls, and the buoyancy as well on the flow pattern and heat transfer performance is evaluated. The two-stage pressure correction scheme is developed and modified for simultaneously determining the distributions of absolute pressure, density, temperature, and velocity of the compressible flow field in the enclosure during the start-up and periodically stable periods. The compressible-flow model is adopted, and the governing equations are expressed in integral form and discretized on the staggered grids which may locally or globally deform in resonance with the walls to accommodate the variation in the volume of the enclosure.
The application of this method has been extended to the following topics: (1) thermal convection in a square enclosure with a vibrating wall, (2) flow and thermal fields in an enclosure with two periodically vibrating walls, (3) flow and thermal fields in an enclosure with partitions and two periodically vibrating walls, and (4) pressure effects on natural convection for non-Boussinesq fluid in a rectangular enclosure.
Effects of wall vibration in a rectangular enclosure containing air under various thermal boundary conditions are investigated. The vibrating wall leads to periodic variations in the flow and thermal fields, and also in Nusselt numbers, within the rectangular enclosure, and hence results in remarkable different features in different situations. Major parameters, including frequency, stroke, and the phase angle of the wall vibrations on the flow, are evaluated. For particular situations, the effects of height of aperture formed by adiabatic partitions are added to study.
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Niu, Furong. "Transpiration by oil palm and rubber plantations: refining methods and delineating differences." Doctoral thesis, 2016. http://hdl.handle.net/11858/00-1735-0000-002B-7C2C-3.
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Дудка, Владислав Сергійович. "Особливості технології вирощування монокристалів кремнію". Магістерська робота, 2020. https://dspace.znu.edu.ua/jspui/handle/12345/4778.
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Дудка В. С. Особливості технології вирощування монокристалів кремнію : кваліфікаційна робота магістра спеціальності 136 "Металургія" / наук. керівник Р. М. Воляр. Запоріжжя : ЗНУ, 2020. 61 с.<br>UA : Проведено аналіз методів вирощування монокристалів кремнію та оцінено структуру та зріст монокристалів по методу Чохральського. Виконана оцінка температурних полів в зоні росту монокристалів, що можуть допомогти оптимізувати процес вирощування монокристалів кремнію. Проаналізовано швидкості зросту монокристалів кремнію по базових напрямах.<br>EN : The analysis of methods for growing silicon single crystals is carried out, and the structure and growth of single crystals by the Czochralski method are estimated. The temperature fields in the growth zone of single crystals are estimated, which can help to optimize the process of growing silicon single crystals. The growth rates of silicon single crystals in basic directions are analyzed.
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Gaspar, Ana Pimentel Torres. "Contribution to control uncertainties in numerical modelling of dam performances: an application to an RCC dam." Doctoral thesis, 2014. http://hdl.handle.net/1822/35837.
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Tese de doutoramento em "Civil Engineering" (ramo do conhecimento em "Geotechnics")<br>The use of fully probabilistic approaches to account for uncertainties within dam engineering is a
recently emerging field on which studies have been mostly done concerning the safety evaluation
of dams under service. This thesis arises within this framework as a contribution on moving
the process of risk analysis of dams beyond empirical knowledge, applying probabilistic tools
on the numerical modelling of a roller compacted concrete (RCC) dam during its construction
phase.
The work developed here aims to propose a methodology so as to account for risks related
to cracking during construction which may compromise the dam’s functional and structural
behaviour.
In order to do so, emphasis is given to uncertainties related to the material itself (i.e.
strength, water-to-cement ratio, among others) as well as to ambient conditions during the
construction phase of RCC dams. A thermo-chemo-mechanical model is used to describe the
RCC behaviour. Concerning the probabilistic model, two aspects are studied: how the uncertainties
related to the input variables are propagated through the model, and what is the
influence of their dispersion on the dispersion of the output, assessed by performing a global
sensitivity analysis by means of the RBD-FAST method. Also, spatial variability of some input
parameters is accounted for through bi-dimensional random fields.
Furthermore, a coupling between reliability methods and finite element methods is performed
in order to evaluate the cracking potential of each casted RCC layer during construction
by means of a cracking density concept. As an important outcome of this applied research,
probability curves for cracking density within each casted layer as functions of both age and
boundary conditions are predicted, which is believed to be an original contribution of this thesis.
The proposed methodology may therefore be seen as a contribution to help engineers understand
how uncertainties will affect the dam behaviour during construction and rely on it in
the future to improve and support the design phase of the dam project.<br>A aplicação de métodos probabilísticos para o estudo de incertezas no ramo da engenharia de
barragens é um campo em crescente ascensão no qual a grande maioria dos estudos realizados se
concentra na avaliação da segurança de barragens durante o período de serviço. Este trabalho
de tese situa-se neste contexto, pretendendo contribuir para a abordagem de análise de risco em
barragens em betão compactado com cilindros (BCC) durante a fase de construção.
Assim, é proposta uma metodologia na qual são tidos em conta riscos relacionados com
a fissuração do BCC durante a sua construção, o que poderá comprometer o comportamento
funcional e estrutural da barragem.
As incertezas consideradas integram algumas propriedades do material (i.e. resistência, rácio
água-cimento, entre outras) bem como as condições climatéricas que se observam durante a fase
de de construção de barragens em BCC. Para descrever o comportamento do BCC é utilizado um
modelo termo-químico-mecânico. O modelo probabilístico considera, por um lado, a propagação
das incertezas relacionadas com as variáveis de entrada e, por outro, permite avaliar qual a
influência que têm na dispersão da resposta do modelo. Essa influência é avaliada através
de uma análise de sensibilidade global, recorrendo ao método RBD-FAST. A variabilidade
espacial de alguns parâmetros de entrada é também tida em conta através de campos aleatórios
bi-dimensionais.
O acoplamento entre métodos de fiabilidade e elementos finitos permite avaliar o potencial
de fissuração de cada camada de BCC durante a construção da barragem. Para tal é introduzido
o conceito de densidade de fissuração. Esta abordagem constitui uma contribuição original, com
a obtenção de curvas de probabilidade para a densidade de fissuração, avaliadas ao nível de cada
camada e em função da idade e condições de fronteira.
A metodologia desenvolvida constitui uma contribuição para a compreensão da influência
de determinadas incertezas no comportamento da barragem durante a sua construção, podendo
servir no futuro como um importante suporte à fase de projecto de barragens.<br>Contribution pour le controle des incertitudes dans la modelisation numerique
de la performance de barrages. Application a un barrage en BCR.
L’application des approches probabilistes pour tenir compte des incertitudes dans le domaine
des barrages est un sujet en developpement. Cependant, la plupart des etudes ont ete realisees
sur l’evaluation de la securite des barrages pendant leur service. Ce travail de these vise a
appliquer ce type d’approches et a faire une contribution a l’analyse de risque des barrages en
beton compacte au rouleau (BCR) des sa construction, a l’aide d’une simulation numerique.
Les travaux presentes dans ce manuscrit proposent l’application d’une methodologie qui vise
a quantifier la vulnerabilite vis-a-vis de l’apparition de la fissuration pendant la construction
du barrage, ce qui peut aflecter a long-terme la permeabilite et par consequent, compromettre
son comportement structurel.
Pour ce faire, l’accent est mis sur les incertitudes liees a quelques caracteristiques des materi-
aux (e.g., resistance, rapport eau-ciment, entre autres) et aux conditions environnementales
pendant la phase de construction. Un modele thermo-chemo-mecanique est utilise pour decrire
le comportement du BCR. En ce qui concerne le modele probabiliste, deux aspects sont etudies:
i) comment les incertitudes liees aux variables d’entree sont propagees dans le modele, et ii)
quelle est l’influence de leur dispersion par rapport a la dispersion totale de la sortie. Ce
dernier est evalue par l’intermediaire d’une analyse de sensibilite globale eflectuee avec la meth-
ode RBD-FAST. En outre, la variabilite spatiale des parametres d’entree est aussi prise en
compte a travers des champs aleatoires bidimensionnels.
Par ailleurs, un couplage entre des methodes de fiabilite et la methode d’elements finis est
eflectue de facon a evaluer le potentiel de fissuration dans chaque couche de BCR lors de sa
construction en utilisant un concept de densite’ dc fissumtion. Comme resultat important issu
de ce travail de recherche, des courbes de probabilite pour la densite de fissuration sont obtenues
au niveau de chaque couche en fonction de leur age et des conditions aux limites, ce qui est considérée comme étant une contribution originale de cette these.
La méthodologie proposée peut etre utilise pour aider a comprendre comment les incerti-
tudes vont affecter le comportement du barrage pendant sa construction et servir d’appui dans
le futur pour améliorer et soutenir la phase de conception du projet de barrage.
Mots-clés: Barrages BCR, Comportement thern1o-chemo-nqécanique, Incertitudes, Meth-
odes de fiabilité, Analyse de sensibilité, RBD-FAST, Champs aléatoires.<br>The financial support by the Portuguese Foundation for Science and Technology (FCT) PhD grant (SFRH/BD/63939/2009, QREN POPH - Tipologia 4.1).