Dissertations / Theses on the topic 'Inverse heat transfer problems'
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Van, Cong Tuan Son. "Numerical solutions to some inverse problems." Diss., Kansas State University, 2017. http://hdl.handle.net/2097/38248.
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Doctor of PhilosophyDepartment of Mathematics
Alexander G. Ramm
In this dissertation, the author presents two independent researches on inverse problems: (1) creating materials in which heat propagates a long a line and (2) 3D inverse scattering problem with non-over-determined data. The theories of these methods were developed by Professor Alexander Ramm and are presented in Chapters 1 and 3. The algorithms and numerical results are taken from the papers of Professor Alexander Ramm and the author and are presented in Chapters 2 and 4.
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Morales, Rebellon Juan Carlos. "Radiation exchange within enclosures of diffuse gray surfaces : the inverse problem /." Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.
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Moore, Travis J. "Application of Variation of Parameters to Solve Nonlinear Multimode Heat Transfer Problems." BYU ScholarsArchive, 2014. https://scholarsarchive.byu.edu/etd/4254.
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The objective of this work is to apply the method of variation of parameters to various direct and inverse nonlinear, multimode heat transfer problems. An overview of the general method of variation of parameters is presented and applied to a simple example problem. The method is then used to obtain solutions to three specific extended surface heat transfer problems: 1. a radiating annular fin, 2. convective and radiative exchange between the surface of a continuously moving strip and its surroundings, and 3. convection from a fin with temperature-dependent thermal conductivity and variable cross-sectional area. The results for each of these examples are compared to those obtained using other analytical and numerical methods. The method of variation of parameters is also applied to the more complex problem of combined conduction-radiation in a one-dimensional, planar, absorbing, emitting, non-gray medium with non-gray opaque boundaries. Unlike previous solutions to this problem, the solution presented here is exact. The model is verified by comparing the temperature profiles calculated from this work to those found using numerical methods for both gray and non-gray cases. The combined conduction-radiation model is then applied to determine the temperature profile in a ceramic thermal barrier coating designed to protect super alloy turbine blades from large and extended heat loads. Inverse methods are implemented in the development of a non-contact method of measuring the properties and temperatures within the thermal barrier coating. Numerical experiments are performed to assess the effectiveness of this measurement technique. The combined conduction-radiation model is also applied to determine the temperature profile along the fiber of an optical fiber thermometer. An optical fiber thermometer consists of an optical fiber whose sensing tip is coated with an opaque material which emits radiative energy along the fiber to a detector. Inverse methods are used to infer the tip temperature from spectral measurements made by the detector. Numerical experiments are conducted to assess the effectiveness of these methods. Experimental processes are presented in which a coating is applied to the end of an optical fiber and connected to an FTIR spectrometer. The system is calibrated and the inverse analysis is used to infer the tip temperature in various heat sources.
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Silieti, Mahmood. "INVERSE BOUNDARY ELEMENT/GENETIC ALGORITHM METHOD FOR RECONSTRUCTION O." Doctoral diss., University of Central Florida, 2004. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3325.
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A methodology is formulated for the solution of the inverse problem concerned with the reconstruction of multi-dimensional heat fluxes for film cooling applications. The motivation for this study is the characterization of complex thermal conditions in industrial applications such as those encountered in film cooled turbomachinery components. The heat conduction problem in the metal endwall/shroud is solved using the boundary element method (bem), and the inverse problem is solved using a genetic algorithm (ga). Thermal conditions are overspecified at exposed surfaces amenable to measurement, while the temperature and surface heat flux distributions are unknown at the film cooling hole/slot walls. The latter are determined in an iterative process by developing two approaches. The first approach, developed for 2d applications, solves an inverse problem whose objective is to adjust the film cooling hole/slot wall temperatures and heat fluxes until the temperature and heat flux at the measurement surfaces are matched in an overall heat conduction solution. The second approach, developed for 2d and 3d applications, is to distribute a set of singularities (sinks) at the vicinity of the cooling slots/holes surface inside a fictitious extension of the physical domain or along cooling hole centerline with a given initial strength distribution. The inverse problem iteratively alters the strength distribution of the singularities (sinks) until the measuring surfaces heat fluxes are matched. The heat flux distributions are determined in a post-processing stage after the inverse problem is solved. The second approach provides a tremendous advantage in solving the inverse problem, particularly in 3d applications, and it is recommended as the method of choice for this class of problems. It can be noted that the ga reconstructed heat flux distributions are robust, yielding accurate results to both exact and error-laden inputs. In all cases in this study, results from experiments are simulated using a full conjugate heat transfer (cht) finite volume models which incorporate the interactions of the external convection in the hot turbulent gas, internal convection within the cooling plena, and the heat conduction in the metal endwall/shroud region. Extensive numerical investigations are undertaken to demonstrate the significant importance of conjugate heat transfer in film cooling applications and to identify the implications of various turbulence models in the prediction of accurate and more realistic surface temperatures and heat fluxes in the cht simulations. These, in turn, are used to provide numerical inputs to the inverse problem. Single and multiple cooling slots, cylindrical cooling holes, and fan-shaped cooling holes are considered in this study. The turbulence closure is modeled using several two-equation approach, the four-equation turbulence model, as well as five and seven moment reynolds stress models. The predicted results, by the different turbulence models, for the cases of adiabatic and conjugate models, are compared to experimental data reported in the open literature. Results show the significant effects of conjugate heat transfer on the temperature field in the film cooling hole region, and the additional heating up of the cooling jet itself. Moreover, results from the detailed numerical studies presented in this study validate the inverse problem approaches and reveal good agreement between the bem/ga reconstructed heat fluxes and the cht simulated heat fluxes along the inaccessible cooling slot/hole wallsPh.D.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Mechanical Engineering
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Rogers, Craig. "PARAMETER ESTIMATION IN HEAT TRANSFER AND ELASTICITY USING TRAINED POD-RBF NETWORK INVERSE METHODS." Master's thesis, University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4143.
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In applied mechanics it is always necessary to understand the fundamental properties of a system in order to generate an accurate numerical model or to predict future operating conditions. These fundamental properties include, but are not limited to, the material parameters of a specimen, the boundary conditions inside of a system, or essential dimensional characteristics that define the system or body. However in certain instances there may be little to no knowledge about the systems conditions or properties; as a result the problem cannot be modeled accurately using standard numerical methods. Consequently, it is critical to define an approach that is capable of identifying such characteristics of the problem at hand. In this thesis, an inverse approach is formulated using proper orthogonal decomposition (POD) with an accompanying radial basis function (RBF) network to estimate the current material parameters of a specimen with little prior knowledge of the system. Specifically conductive heat transfer and linear elasticity problems are developed in this thesis and modeled with a corresponding finite element (FEM) or boundary element (BEM) method. In order to create the truncated POD-RBF network to be utilized in the inverse approach, a series of direct FEM or BEM solutions are used to generate a statistical data set of temperatures or deformations in the system or body, each having a set of various material parameters. The data set is then transformed via POD to generate an orthonormal basis to accurately solve for the desired material characteristics using the Levenberg-Marquardt (LM) algorithm. For now, the LM algorithm can be simply defined as a direct relation to the minimization of the Euclidean norm of the objective Least Squares function(s). The trained POD-RBF inverse technique outlined in this thesis provides a flexible by which this inverse approach can be implemented into various fields of engineering and mechanics. More importantly this approach is designed to offer an inexpensive way to accurately estimate material characteristics or properties using nondestructive techniques. While the POD-RBF inverse approach outlined in this thesis focuses primarily in application to conduction heat transfer, elasticity, and fracture mechanics, this technique is designed to be directly applicable to other realistic conditions and/or industries.M.S.M.E.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Mechanical Engineering MSME
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Cremonini, Guilherme Ernesto Serrat de Oliveira. "Aplicação do método inverso de condução de calor na avaliação de fluidos de resfriamento para têmpera." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/18/18158/tde-11052015-125002/.
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A têmpera dos aços envolve a austenitização de uma peça seguida por um resfriamento rápido para promover a formação de microestrutura martensítica. É necessário avaliar os meios de têmpera para manter o processo de têmpera sob controle. Os parâmetros mais importantes no processo de resfriamento são o coeficiente de transferência de calor e/ou o fluxo de calor entre o meio de têmpera e a peça a ser resfriada. Um dos métodos de se avaliar os meios de têmpera (meios de resfriamento) e saber o que está acontecendo dentro da peça durante o resfriamento do ponto de vista térmico é o problema inverso de condução de calor. O problema inverso de condução de calor consiste na determinação de parâmetros como fluxo de calor, taxa de resfriamento e temperatura em qualquer posição através da peça, assim como o coeficiente de transferência de calor. Esses parâmetros são obtidos a partir de medições de temperatura em um ou mais pontos dentro da peça. O escopo deste trabalho foi desenvolver um software baseado no problema inverso condução de calor para avaliar meios de resfriamento para têmpera. A validação deste código foi feita usando água, óleo de soja, óleo mineral e solução aquosa de NaNO3.Steels quenching involves part austenitization followed by a fast cooling to promote martensitic microstructure formation. It is necessary to evaluate quenchants in order to keep the quenching process under control. The most important cooling process parameters are the heat transfer coefficient and/or the heat flux between the quenchant and the part to be cooled. One of the methods to evaluate quenchants (cooling media) and to know what is happening inside the part during the cooling in the thermal point of view is the inverse heat conduction problem. The inverse heat conduction problem consists in the determination of parameters like heat flux, cooling rate and temperature in any position across the part, as well as the heat transfer coefficient. These parameters are obtained from temperature measurements in one or more points inside the part. The scope of this work was to develop a software based in the inverse heat conduction problem in order to evaluate quenchants for quenching. The validation of this code was made using water, soybean oil, mineral oil and NaNO3 aqueous solution.
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Mansour, Salwa. "Contribution to certain physical and numerical aspects of the study of the heat transfer in a granular medium." Thesis, Rennes 1, 2015. http://www.theses.fr/2015REN1S088/document.
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L'étude du transfert de chaleur et de masse dans les milieux poreux saturés et insaturés fortement chauffés à leur surface possèdent de nombreuses applications, notamment en archéologie, en agriculture et en géothermie. La première partie de ce travail concerne l'amélioration de la méthode AHC (Accumulation de chaleur latente) qui permet de traiter le changement de phase, dans un milieu homogène : l'intervalle de changement de température au moment du changement de phase apparaît comme un paramètre important, et il doit être choisi proportionnel à la taille des mailles. Des résultats à la fois précis et lisses sont obtenus grâce à un raffinement du maillage localisé près de l'interface de changement de phase. La deuxième partie se rapporte à l'estimation des propriétés thermophysiques du sol par problème inverse à l'aide de données à la fois synthétiques et expérimentales. La méthode de Gauss-Newton avec relaxation et l'algorithme de Levenberg-Marquardt sont utilisés pour résoudre le problème inverse. Le choix de l'intervalle de température de la méthode AHC apparaît crucial : la convergence n'est obtenue parfois qu'au prix d'un enchaînement de plusieurs problèmes inverses. La troisième partie présente un modèle simple pour calculer la conductivité thermique effective d'un milieu granulaire contenant une faible quantité d'eau liquide. La forme exacte de ces ménisques est calculée à l'équilibre. Les résultats montrent un phénomène très net d'hystérésis quand on étudie la variation de la conductivité thermique effective en fonction de la quantité d'eau liquide ; un futur travail concernant un nouveau modèle insaturé, limité au cas du régime pendulaire et présenté à la fin de cette thèse, devrait pouvoir utiliser ces résultatsIn this work, we are interested in studying heat and mass transfer in water saturated and unsaturated porous medium with a strong heating at the surface. Applications concerned are archaeology, agriculture and geothermal engineering. The first part of this work concerns the improvement of the AHC (Apparent Heat Capacity) method used in the numerical resolution of phase change problem in a homogeneous medium: the phase change temperature interval, over which the heat capacity varies, appears as a key parameter which must be chosen proportional to the mesh size. Accurate and smooth results are obtained thanks to a local refinement of the mesh near the phase change interface. The second part is about the estimation of the thermophysical properties of the soil by inverse problem using both synthetic and experimental data. The Damped Gauss-Newton and the Levenberg-Marquardt algorithms are used to solve the problem. In relation with the AHC method, the choice of the phase change temperature interval caused convergence problems which have been fixed by chaining many inverse problems. The obtained results show good convergence to the desired solution. The third part presents a simple model to calculate the effective thermal conductivity of a granular medium which contains a small quantity of liquid water. The exact shape of the liquid menisci between the grains is calculated at equilibrium. The effective thermal conductivity experiences a hysteresis behavior with respect to the liquid volume. A future work that concerns a new unsaturated model, restricted to the pendular regime and detailed at the end of this thesis, should be able to use this result
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Hřibová, Veronika. "Vývoj inverzní sub-doménové metody pro výpočet okrajových podmínek vedení tepla." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-232179.
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It is very important to develop efficient but still accurate and stable numerical methods for solving heat and mass transfer processes in many industrial applications. The thesis deals with an inverse heat conduction problem which is used to compute boundary conditions (temperatures, heat flux or heat transfer coefficient). Nowadays, two approaches are often used for inverse task - sequential estimation and whole domain estimation. The main goal of this work is to develop a new approach, the so-called sub-domain method, which emphasizes advantages just as reduce disadvantages of both methods mentioned above. This approach is then tested on generated prototypic data and on data from real experiments. All methods are compared with respect to accuracy of results as well as to computational efficiency.
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Musil, Jiří. "Software pro řešení inverzních úloh přenosu tepla." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-417446.
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Tato práce se zabývá vytvořením softwarového nástroje pro simulaci přenosu tepla se zaměřením na využití inverzní úlohy. Je zde popsána základní teorie inverzních úloh a přenosu tepla, na kterou navazuje odvození numerické rovnice přenosu tepla, vhodné pro počítačovou simulaci. Hlavní část práce se věnuje návrhu a samotné implementaci softwarového řešení, s ohledem jak na funkčnost, tak na uživatelskou přívětivost. Kromě výpočtového modelu, který je zodpovědný za průběh simulace, je vytvořeno také plnohodnotné uživatelské rozhraní (GUI), umožňující jednoduchou interakci s výpočtovým modelem. Závěrem práce je prezentování dosažených výsledků a jejich porovnání s reálným experimentem, stejně jako zjištění vlivu vstupních parametrů na kvalitu simulace.
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AZEGAMI, Hideyuki, Yutaro IWATA, Eiji KATAMINE, 秀幸 畔上, 侑太朗 岩田, and 英次 片峯. "放熱量最大化を目的とした非定常熱伝導場の形状最適化." 一般社団法人日本機械学会, 2008. http://hdl.handle.net/2237/21114.
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Kůdelová, Tereza. "Řešení inverzních úloh v oblasti výměníků hmoty a tepla." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2014. http://www.nusl.cz/ntk/nusl-231153.
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This master’s thesis deals with the dynamic behaviour of the heat exchangers which is described by a system of differential equations. In this connection, it contains general informations about heat transfer, heat exchangers and their arrangements. The main aim of this thesis is to solve the inverse problem of the antiparallel arrangement and discuss the question of the controllability, observability and identifiability of its parameters.
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Gaspar, Jonathan. "Fluxmétrie et caractérisation thermiques instationnaires des dépôts des composants face au plasma du Tokamak JET par techniques inverses." Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4739/document.
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Ces travaux portent sur la résolution successive de deux problèmes inverses en transferts thermiques : l'estimation de la densité de flux en surface d'un matériau puis de la conductivité thermique équivalente d'une couche déposée en surface de ce matériau. Le modèle direct est bidimensionnel orthotrope (géométrie réelle d'un matériau composite), instationnaire, non-linéaire et ses équations sont résolues par éléments finis. Les matériaux étudiés sont les composants face au plasma (tuiles composite carbone-carbone) dans le Tokamak JET. La densité de flux recherchée varie avec une dimension spatiale et avec le temps. La conductivité du dépôt de surface varie spatialement et peut également varier au cours du temps pendant l'expérience (toutes les autres propriétés thermophysiques dépendent de la température). Les deux problèmes inverses sont résolus à l'aide de l'algorithme des gradients conjugués associé à la méthode de l'état adjoint pour le calcul exact du gradient. La donnée expérimentale utilisée pour la résolution du premier problème inverse (estimation de flux surfacique) est le thermogramme fourni par un thermocouple enfoui. Le second problème inverse utilise, lui, les variations spatio-temporelles de la température de surface du dépôt inconnu (thermographie infrarouge) pour identifier sa conductivité. Des calculs de confiance associée aux grandeurs identifiées sont réalisés avec la démarche Monte Carlo. Les méthodes mises au point pendant ces travaux aident à comprendre la dynamique de l'interaction plasma-paroi ainsi que la cinétique de formation des dépôts de carbone sur les composants et aideront au design des composants des machines futures (WEST, ITER)This work deals with the successive resolution of two inverse heat transfer problems: the estimation of surface heat flux on a material and equivalent thermal conductivity of a surface layer on that material. The direct formulation is bidimensional, orthotropic (real geometry of a composite material), unsteady, non-linear and solved by finite elements. The studied materials are plasma facing components (carbon-carbon composite tiles) from Tokamak JET. The searched heat flux density varies with time and one dimension in space. The surface layers conductivity varies spatially and can vary with time during the experiment (the other thermophysical properties are temperature dependent). The two inverse problems are solved by the conjugate gradient method with the adjoint state method for the exact gradient calculation. The experimental data used for the first inverse problem resolution (surface heat flux estimation) is the thermogram provided by an embedded thermocouple. The second inverse problem uses the space and time variations of the surface temperature of the unknown surface layer (infrared thermography) for the conductivity identification. The confidence calculations associated to the estimated values are done by the Monte Carlo approach. The method developed during this thesis helps to the understanding of the plasma-wall interaction dynamic, as well as the kinetic of the surface carbon layer formation on the plasma facing components, and will be helpful to the design of the components of the future machines (WEST, ITER)
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Maia, Neto Alfredo dos Santos. "Simulação computacional do processo de soldagem MIG de uma junta de topo de chapas de aço inoxidável da série 304 com deposição de material." Universidade Federal de Uberlândia, 2014. https://repositorio.ufu.br/handle/123456789/14780.
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Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorThis work presents a 3D computational/mathematical model to solve the heat diffusion equation with phase change, considering addition of material and complex geometry. The finite volume method was used and the computational code was implemented in C++, using Borland compiler. Experimental tests were carried out for validation of the model in question. It was used a material whose thermal properties, varying with temperature, are well known: the stainless steel AISI 304. In addition, an inverse technique based on Golden Section was implemented to estimate the heat flux supplied to the sample. Experimental temperatures were measured using thermocouples type J - in a total of 07 (seven) - all connected to the metal sheet and the Agilent 34970A datalogger. The metal had a \"V\" Groove of 45°. In this location was conducted the deposition of material on only one welding pass and the dimensions (width and height) were measured after welding. The thermal model was validated from comparisons between measured and calculated temperatures. The results were consistent and validated the computational/mathematical model proposed. An innovation presented in this work consists in the calculation and visualization of the dimensions of the welding pool during welding. The complex geometry obtained proves that more studies are needed and new models must be designed to clarify and explain the formation of welding pool during welding of metal sheet.
Desenvolve-se, neste trabalho, um modelo matemático/computacional 3D (tridimensional) de difusão de calor com mudança de fase, acréscimo de material e geometria complexa. O método de volumes finitos foi implementado em linguagem C, utilizando o compilador Borland. Foram realizados testes experimentais para a validação do modelo em questão. Usou-se um material cujas propriedades térmicas, variando com a temperatura, são bem conhecidas: o aço inox AISI 304. Além do modelo direto já citado, foi implementada uma técnica inversa para o cálculo do fluxo de calor. Utilizou-se neste caso a amplamente conhecida Seção Áurea: técnica que exige uma simplificação, fluxo de calor constante ao longo do tempo de soldagem. As temperaturas na chapa foram medidas utilizando termopares do tipo J - em um total de 07 (sete) - todos ligados ao datalogger Agilent 34970A. As medições foram feitas do lado oposto à tocha de soldagem. A chapa metálica possuía um chanfro em V de 45º. Neste local foi realizada a deposição de material (reforço) em somente um passe de soldagem. As dimensões da geometria do reforço (largura e altura) foram medidas depois da realização da soldagem. Em relação aos resultados, além da comparação entre as temperaturas medidas e calculadas, foi também determinada a eficiência térmica da soldagem. Os resultados foram consistentes e validaram o modelo matemático/computacional proposto. Uma inovação apresentada neste trabalho consiste no cálculo e visualização gráfica tridimensional da poça de fusão ao longo do tempo. A complexa geometria obtida comprova que mais estudos se fazem necessários e que novos modelos devem ser concebidos para esclarecer e explicar a formação da poça de fusão durante a soldagem de chapas metálicas.
Doutor em Engenharia Mecânica
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Mohebbi, Farzad. "Optimal shape design based on body-fitted grid generation." Thesis, University of Canterbury. Mechanical Engineering, 2014. http://hdl.handle.net/10092/9427.
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Shape optimization is an important step in many design processes. With the growing use of Computer Aided Engineering in the design chain, it has become very important to develop robust and efficient shape optimization algorithms. The field of Computer Aided Optimal Shape Design has grown substantially over the recent past. In the early days of its development, the method based on small shape perturbation to probe the parameter space and identify an optimal shape was routinely used. This method is nothing but an educated trial and error method. A key development in the pursuit of good shape optimization algorithms has been the advent of the adjoint method to compute the shape sensitivities more formally and efficiently. While undoubtedly, very attractive, this method relies on very sophisticated and advanced mathematical tools which are an impediment to its wider use in the engineering community. It that spirit, it is the purpose of this thesis to propose a new shape optimization algorithm based on more intuitive engineering principles and numerical procedures. In this thesis, the new shape optimization procedure which is proposed is based on the generation of a body-fitted mesh. This process maps the physical domain into a regular computational domain. Based on simple arguments relating to the use of the chain rule in the mapped domain, it is shown that an explicit expression for the shape sensitivity can be derived. This enables the computation of the shape sensitivity in one single solve, a performance analogous to the adjoint method, the current state-of-the art. The discretization is based on the Finite Difference method, a method chosen for its simplicity and ease of implementation. This algorithm is applied to the Laplace equation in the context of heat transfer problems and potential flows. The applicability of the proposed algorithm is demonstrated on a number of benchmark problems which clearly confirm the validity of the sensitivity analysis, the most important aspect of any shape optimization problem. This thesis also explores the relative merits of different minimization algorithms and proposes a technique to “fix” meshes when inverted element arises as part of the optimization process. While the problems treated are still elementary when compared to complex multiphysics engineering problems, the new methodology presented in this thesis could apply in principle to arbitrary Partial Differential Equations.
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Komínek, Jan. "Heuristické algoritmy pro optimalizaci." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2012. http://www.nusl.cz/ntk/nusl-230306.
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This diploma thesis deals with genetic algorithms and their properties. Particular emphasis is placed on finding the influence of mutation and population size. Genetic algorithms are applied on inverse heat conduction problems (IHCP) in the second part of the thesis. Several different approaches and coding methods were tested. Properties of genetic algorithms were improved by definition of two new genetic operators – manipulation and sorting. Reported theoretical findings were tested on the real data of inverse heat conduction problem. The library for easy implementation of GA for solving general optimization problems in C ++ was created and is described in the last chapter.
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Hadad, Waseem Al. "Thermique des mini-canaux : comportement instationnaire et approche convolutive." Thesis, Université de Lorraine, 2016. http://www.theses.fr/2016LORR0121/document.
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Un modèle semi-analytique permettant de simuler le transfert thermique conjugué dans un mini/macro canal plan soumis à des sources de chaleur surfaciques localisées sur les faces externes et variantes en fonction du temps, a été présenté et vérifié. Plus le diamètre hydraulique du canal est petit, plus la caractérisation expérimentale interne (mesure des températures et des flux) en régime thermique permanent ou transitoire à l'aide des capteurs internes est délicate. Une méthode non-intrusive permettant d'estimer les conditions internes à partir des mesures de température par thermographie infrarouge sur les faces externes et d'un modèle semi-analytique, a été effectuée. Comme le coefficient de transfert convectif forcé classique perd son sens en régime instationnaire, une approche alternative basée sur une fonction de transfert, valable pour un système linaire et invariant dans le temps a été mise en œuvre. Cette fonction peut être calculée analytiquement (uniquement pour une géométrie simple) ou estimée expérimentalement (géométrie complexe). Grâce au caractère intrinsèque de cette fonction de transfert, deux capteurs virtuels ont été conçus : capteur virtuel de température et détecteur d'encrassement permettent respectivement d'estimer les températures internes et de détecter l'encrassement qui peut avoir lieu dans l'échangeur à partir des mesures de températures sur les faces externesA semi-analytical model allowing to simulate the transient conjugate heat transfer in mini/macro plane channel subject to a heat source(s) localized on the external face(s), was presented and verified. The developed model takes into account advection-diffusion in the fluid and conduction in the solid. As the hydraulic diameter of the channel becomes small, the internal experimental characterization (measurement of temperature and heat flux) using internal sensors become tricky because internal sensors located may compromise the structural integrity of the whole system. A non-intrusive method for estimating the internal conditions from infrared temperature measurements on the external faces using the semi-analytical model was performed. Since the classic convective heat transfer coefficient loses its meaning in transient state, an alternative approach based on a transfer function, valid for Linear Time-Invariant (LTI) systems, was highlighted. This function can be calculated analytically only for a simple geometry. For complex geometries it can be estimated experimentally. Thanks to intrinsic character of this function, two characterization methods were designed. The first to estimate the temperature at a point from a measurement at another point in the system (virtual temperature sensor). The second method concerns the detection of fouling layers that may appear in the heat exchanger from temperature measurements on the external faces
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Zhang, Xinxin. "Métrologie thermique par méthode quasi-stationnaire : modélisation, identification et application a la caractérisation de solides." Vandoeuvre-les-Nancy, INPL, 1993. http://www.theses.fr/1993INPL037N.
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Nous développons une méthode en régime quasi stationnaire pour déterminer les propriétés thermiques de matériaux solides en utilisant une technique d'estimation de paramètres. La démarche systématique utilisée consiste à modéliser l'expérience par la méthode des quadripôles thermiques. On choisit le modèle d'estimation par comparaison entre divers modèles obtenus. Les bons paramètres à identifier ainsi que le bon intervalle sur lequel ces paramètres seront estimés sont mis en évidence par une analyse de sensibilité et une analyse asymptotique. La sonde plane fait intervenir un seul paramètre caractéristique du milieu, (c)#1#/#2, qui est sensible et donc facile à estimer. La sonde cylindrique fait intervenir deux paramètres: et a/r#2. Dans ce cas, l'étude de sensibilité montre que seul λ est identifiable. La sonde sphérique fait apparaitre deux grandeurs indépendantes (λ, α) dans trois groupements: a, a/r#2 et 1/4 r. Le paramètre caractéristique du milieu a apparait au deuxième ordre du développement asymptotic. C'est une difficulté pour l'identification. Une étude expérimentale portant sur les matériaux céramiques pour les sondes plane et cylindrique et sur un lit de billes de verre pour la sonde sphérique, a validé notre méthode et a confirmé les prédictions théoriques
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Llanos, Luis Alberto Quezada. "Estudo experimental de estabilidade e emissão de radiação térmica em chamas não pré-misturadas de gás natural diluídas com dióxido de carbono." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/178794.
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Modelos algébricos para prever o comprimento de uma chama turbulenta têm sido foco de estudo de diversos grupos de pesquisa por suas aplicações na área de engenharia. O método experimental para obter o modelo varia desde visualizações simples, até técnicas fotográficas, este último com parâmetros fotográficos variando entre os autores. Técnicas fotográficas são usadas para estimar a altura de levantamento da base da chama, (Lift-Off) e o comprimento médio visível de chama (Visible Flame Length, VFL). Duas técnicas comuns que podem ser encontradas na literatura: por imagens de chama com baixo tempo de exposição e longo tempo de exposição, são comparados com um terceiro que se baseia na intensidade luminosa e na frequência de imagens de chama que ocupam um pixel. O melhor método foi utilizado para caracterizar o comportamento das chamas turbulentas de gás natural para diferentes regimes de velocidade do escoamento. Modelos algébricos que preveem o comprimento de chama, altura de levantamento e a velocidade crítica de extinção de chama são avaliados com os novos resultados experimentais. Logo após, os coeficientes numéricos dos melhores modelos algébricos são reajustados Finalmente, foram obtidos mapas de estabilidade relacionados à altura de levantamento e à velocidade crítica de extinção de chama para cada diâmetro em função da diluição com CO2 e do número adimensional de Reynolds. A terceira parte deste trabalho está focada no estudo da distribuição de radiação térmica. Em particular, foram consideradas três distâncias radiais medidas em comprimentos de chama (0,5 Lf, 1 Lf, 2 Lf) visando obter a distribuição do fluxo radiante experimental ao longo de um eixo vertical adjacente às chamas. Finalmente, os dados experimentais foram utilizados como dados de entrada em uma análise inversa com o objetivo de calcular os fatores de ponderação do modelo das múltiplas fontes ponderadas (por suas siglas em inglês WMPS). Nesta última parte, são apresentados frações radiantes e distribuições de fluxo de calor radiante de chamas de gás natural diluídas para diversas diluições com dióxido de carbono e diâmetros do queimador.Predicting models for turbulent diffusion flame lengths have several applications driven the attention of many research groups. Since several studies use photographs to measure the flame length, with photographic parameters varying among authors, in other cases simple visualizations were used. It is important to explore possible discrepancies among measurement technics that could affect the results. Optical visualizations of turbulent diffusion flames are used to estimate the visible average flame length (VFL) and the lift-off. The study presents a study of three different methods to measure the VFL using optical techniques. The effect on the image of the main optic parameters such as focus, exposure time and ISO sensibility are analyzed. The VFL obtained with images in low exposure time and long exposure time are compared with a third optical method that is based on the luminous intensity and the frequency of flame images occupying a pixel. One method was used to characterize the behavior of turbulent diffusion flames of natural gas for a range of flames in function of the flow velocity. Universal non-dimensional models that describe the VFL, lift-off and the blow-out stability limit of gaseous jet diffusion flames in the still air have been compared with new experimental data. The numerical coefficients of the best models are adjusted. Finally, maps of stability related to lift-off and blow-out were obtained for each diameter in function of the dilution with CO2 and flow exit velocity expressed in non-dimensional Reynolds number The third part of this work focuses on the estimation of the thermal distribution of radiative flux from turbulent diffusion flames in laboratory-scale. The experimental measurements were gotten from the previous stability study. In particular, was considered three radial distances measured in flame lengths (0,5 Lf, 1 Lf, 2 Lf) aiming at obtaining the experimental radiant flux along a vertical axis adjacent to the flames. Finally, the experimental data was used as input data in an inverse analysis with the purpose of computing weight coefficients of the weighted multi-point source (WMPS) model. Then, experimental data that include: radiant fractions and radiative heat flux are presents for several flames with different dilutions with carbon dioxide and burner´s diameters.
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Loussouarn, Thomas. "Maîtrise de la thermique des fours de maintien en fonderie." Thesis, Université de Lorraine, 2018. http://www.theses.fr/2018LORR0105.
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Les fours de maintien à induction sous vide sont utilisés pour la fabrication d'aubes de turbine à l'aide du procédé de fonderie à cire perdue. La maîtrise de la thermique de ce dernier est primordiale afin d'assurer la qualité de la production. Ce travail est composé de 3 grandes parties : la modélisation détaillée du four, la modélisation réduite et l'expérience. Un four axisymétrique et sa charge ont été modélisés numériquement à l'aide des logiciels FlexPDE et COMSOL Multiphysics. Ces modèles utilisent en entrée la puissance consommée par les inducteurs et fournissent en sortie la température en tout point du module de chauffe et de la charge. Les modèles réduits étudiés sont des modèles physiques dit convolutifs (enthalpique (0D), analytique de dimension 1 (1D)) et paramétrique de type AutoRégressifs avec variables eXogènes (ARX). Les modèles ARX ont été comparés aux modèles convolutifs (procédures d'identification, puis de validation, de modèles). L'objectif est d'accéder à des températures en certains points du four sans présence d'un capteur physique local (capteur virtuel). Les modélisations détaillées et réduites ont été comparées à des expériences réalisées sur four de production. Cette dernière partie n'est pas décrite dans ce mémoireVacuum holding induction furnaces are used for the manufacturing of turbine blades by loss wax foundry process. Heat transfer control in a holding furnace is crucial to ensure the quality of manufacturing. This work has 3 major parts, which are the detailed modelling, reduced modelling and experiments. An axyisymmetric furnace and its load have been numerically modelled using FlexPDE and COMSOL Multiphysics, finite element codes. Modelling takes as inputs the electric power consumed by inductors and gives the temperature field in the heating module. The studied reduced models are phyisical convolutive models (enthalpic (0D), 1 dimension analytical (1D)) and parametric like AutoRegressive with eXogeneous inputs (ARX). ARX models have been compared to convolutive models (identification, validation). The goal is to get temperatures in the heating module without local presence of physical sensors (virtual sensor). Detailed and reduced models have been compared to experiments on the furnace. This last part is not described in this document
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Jones, Alastair Stephen. "Convection heat transfer problems." Thesis, Keele University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267356.
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Berntsson, Fredrik. "Numerical methods for inverse heat conduction problems /." Linköping : Univ, 2001. http://www.bibl.liu.se/liupubl/disp/disp2001/tek723s.pdf.
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Okamoto, Kei. "Optimal numerical methods for inverse heat conduction and inverse design solidification problems." Online access for everyone, 2005. http://www.dissertations.wsu.edu/Dissertations/Fall2005/k%5Fokamoto%5F120905.pdf.
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Figueiredo, Patric. "Iterative method for solving inverse heat conduction problems." Master's thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/14400.
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Horák, Aleš. "Návrh experimentu pro řešení inverzní úlohy vedení tepla." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-233977.
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this thesis complex inverse heat transfer problem, which is focused on optimal design of experiment, is studied. There are many fields and applications in technical practice, where inverse tasks are or can be applied. On first place main attention is focused on industrial metallurgical processes such as cooling of continues casting, hydraulic descaling or hot rolling. Inverse problems are in general used to calculate boundary conditions of differential equations and in this field are used to find out Heat Transfer Coefficient (HTC). Knowledge of numerical approximation of precise boundary conditions is nowadays essential. It allows for example design of optimized hot rolling mill cooling focused on material properties and final product quality. Sequential Beck’s approach and optimization method is used in this work to solve inverse heat transfer problems. Special experimental test bench measuring heat transfer intensity was developed and built to full fill specific requirements and required accuracy. There were four different types of thermal sensor applied and studied. Those sensors are in usage in Heat Transfer and Fluid Flow laboratory (Heatlab) at various experimental test benches. Each specific sensor was tailored in Heat Transfer and Fluid Flow Laboratory to specific metallurgical application. Fist type of sensor was designed to simulate cooling during continuous casting. Second sensor is used for experiments simulate hot rolling mill cooling, while third sensor is designated for experiments with fast moving hot rolled products. Last sensor is similar to sensor type one, but thermocouple is located parallel to cooled surface. Experimental part of this study covers series of measurements to investigate Heat Transfer Coefficient (HTC) for various types of coolant, cooling mixtures and spray parameters. Results discovered in this study were compared with published scientific articles, and widely extend the knowledge of cooling efficiency for commonly used
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Hussein, Mohammed Sabah. "Coefficient identification problems in heat transfer." Thesis, University of Leeds, 2016. http://etheses.whiterose.ac.uk/12291/.
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The aim of this thesis is to find the numerical solution for various coefficient identification problems in heat transfer and extend the possibility of simultaneous determination of several physical properties. In particular, the problems of coefficient identification in a fixed or moving domain for one and multiple unknowns are investigated. These inverse problems are solved subject to various types of overdetermination conditions such as non-local, heat flux, Cauchy data, mass/energy specification, general integral type overdetermination, time-average condition, time-average of heat flux, Stefan condition and heat momentum of the first and second order. The difficulty associated with these problems is that they are ill-posed, as their solutions are unstable to inclusion of random noise in input data, therefore traditional techniques fail to provide accurate and stable solutions. Throughout this thesis, the Crank-Nicolson finite-difference method (FDM) is mainly used as a direct solver except in Chapter 7 where a three-level scheme is employed in order to deal with the nonlinear heat equation. An explicit FDM scheme is also employed in Chapter 10 for the two-dimensional case. The inverse problems investigated are discretised using the FDM and recast as nonlinear least-squares minimization problems with simple bounds on the unknown coefficients. The resulting problem is efficiently solved using the \emph{fmincon} or \emph{lsqnonlin} routines from MATLAB optimization toolbox. The Tikhonov regularization method is included where necessary. The choice of the regularization parameter(s) is thoroughly discussed. The stability of the numerical solution is investigated by introducing Gaussian random noise into the input data. The numerical solutions are compared with their known analytical solution, where available, and with the corresponding direct problem numerical solution where no analytical solution is available.
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Kaya, Mujdat. "Inverse Problems For A Semilinear Heat Equation With Memory." Phd thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606106/index.pdf.
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ABSTRACT
INVERSE PROBLEMS FOR A SEMILINEAR HEAT
EQUATIONS WITH MEMORY
Kaya, Müjdat Ph.D, Department of Mathematics Supervisor: Prof. Dr. A. Okay Ç
elebi Co-Supervisor: Prof. Dr. Varga Kalantarov May 2005, 79 pages In this thesis, we study the existence and uniqueness of the solutions of the inverse problems to identify the memory kernel k and the source term h, derived from First, we obtain the structural stability for k, when p=1 and the coefficient p, when g( )= . To identify the memory kernel, we find an operator equation after employing the half Fourier transformation. For the source term identification, we make use of the direct application of the final overdetermination conditions.
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Hazanee, Areena. "Boundary element method for solving inverse heat source problems." Thesis, University of Leeds, 2015. http://etheses.whiterose.ac.uk/10570/.
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In this thesis, the boundary element method (BEM) is applied for solving inverse source problems for the heat equation. Through the employment of the Green’s formula and fundamental solution, the BEM naturally reduces the dimensionality of the problem by one although domain integrals are still present due to the initial condition and the heat source. We mainly consider the identification of time-dependent source for heat equation with several types of conditions such as non-local, non-classical, periodic, fixed point, time-average and integral which are considered as boundary or overdetermination conditions. Moreover, the more challenging cases of finding the space- and time-dependent heat source functions for additive and multiplicative cases are also considered. Under the above additional conditions a unique solution is known to exist, however, the inverse problems are still ill-posed since small errors in the input measurements result in large errors in the output heat source solution. Then some type of regularisation method is required to stabilise the solution. We utilise regularisation methods such as the Tikhonov regularisation with order zero, one, two, or the truncated singular value decomposition (TSVD) together with various choices of the regularisation parameter. The numerical results obtained from several benchmark test examples are presented in order to verify the efficiency of adopted computational methodology. The retrieved numerical solutions are compared with their analytical solutions, if available, or with the corresponding direct numerical solution, otherwise. Accurate and stable numerical solutions have been obtained throughout for all the inverse heat source problems considered.
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Buckley, Donovan O. "Solution of Nonlinear Transient Heat Transfer Problems." FIU Digital Commons, 2010. http://digitalcommons.fiu.edu/etd/302.
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In the presented thesis work, meshfree method with distance fields was extended to obtain solution of nonlinear transient heat transfer problems. The thesis work involved development and implementation of numerical algorithms, data structure, and software. Numerical and computational properties of the meshfree method with distance fields were investigated. Convergence and accuracy of the methodology was validated by analytical solutions, and solutions produced by commercial FEM software (ANSYS 12.1). The research was focused on nonlinearities caused by temperature-dependent thermal conductivity. The behavior of the developed numerical algorithms was observed for both weak and strong temperature-dependency of thermal conductivity. Oseen and Newton-Kantorovich linearization techniques were applied to linearized the governing equation and boundary conditions. Results of the numerical experiments showed that the meshfree method with distance fields has the potential to produced fast accurate solutions. The method enables all prescribed boundary conditions to be satisfied exactly.
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Cao, Kai. "Inverse problems for the heat equation using conjugate gradient methods." Thesis, University of Leeds, 2018. http://etheses.whiterose.ac.uk/22611/.
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In many engineering systems, e.g., in heat exchanges, reflux condensers, combustion chambers, nuclear vessels, etc. concerned with high temperatures/pressures/loads and/or hostile environments, certain properties of the physical medium, geometry, boundary and initial conditions are not known and their direct measurement can be very inaccurate or even inaccessible. In such a situation, one can adopt an inverse approach and try to infer the unknowns from some extra accessible measurements of other quantities that may be available. The purpose of this thesis is to determine the unknown space-dependent coefficients and/or initial temperature in inverse problems of heat transfer, especially to simultaneously reconstruct several unknown quantities. These inverse problems are investigated from additional pieces of information, such as internal temperature observations, final measured temperature and time-integral temperature measurement. The main difficulty involved in the solution of these inverse problems is that they are typically ill-posed. Thus, their solutions are unstable under small perturbations of the input data and classical numerical techniques fail to provide accurate and stable numerical results. Throughout this thesis, the inverse problems are transformed into optimization problems, and their minimizers are shown to exist. A variational method is employed to obtain their Fréchet gradients with respect to the unknown quantities. Based on this gradient, the conjugate gradient method (CGM) is established together with the adjoint and sensitivity problems. The stability of the numerical solution is investigated by introducing Gaussian random noise into the input measured data. Accurate and stable numerical solutions are obtained when using the CGM regularized by the discrepancy principle.
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Copiello, Diego <1980>. "Multiobjective genetic algorithms applied to heat transfer problems." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/1218/.
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In the present work, the multi-objective optimization by genetic algorithms is investigated and applied to heat transfer problems. Firstly, the work aims to compare different reproduction processes employed by genetic algorithms and two new promising processes are suggested. Secondly, in this work two heat transfer problems are studied under the multi-objective point of view. Specifically, the two cases studied are the wavy fins and the corrugated wall channel. Both these cases have already been studied by a single objective optimizer. Therefore, this work aims to extend the previous works in a more comprehensive study.
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Yi, Hak-Chae J. "Solution of time-independent inverse problems for linear transport theory /." Thesis, Connect to this title online; UW restricted, 1990. http://hdl.handle.net/1773/10677.
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Langmore, Ian. "Inverse transport with angularly averaged measurements /." Thesis, Connect to this title online; UW restricted, 2008. http://hdl.handle.net/1773/5771.
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Zhong, Rong. "Inverse algorithm for determination of heat flux." Ohio : Ohio University, 2000. http://www.ohiolink.edu/etd/view.cgi?ohiou1173380355.
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Ibrahim, Yasser Aly Abdel-Hamid. "Hydrodynamics, heat, and mass transfer characteristics of three-phase inverse fluidized beds." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0006/NQ42566.pdf.
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Baleine, Erwan. "ON THE USE OF VARIABLE COHERENCE IN INVERSE SCATTERING PROBLEMS." Doctoral diss., University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4114.
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Even though most of the properties of optical fields, such as wavelength, polarization, wavefront curvature or angular spectrum, have been commonly manipulated in a variety of remote sensing procedures, controlling the degree of coherence of light did not find wide applications until recently. Since the emergence of optical coherence tomography, a growing number of scattering techniques have relied on temporal coherence gating which provides efficient target selectivity in a way achieved only by bulky short pulse measurements. The spatial counterpart of temporal coherence, however, has barely been exploited in sensing applications. This dissertation examines, in different scattering regimes, a variety of inverse scattering problems based on variable spatial coherence gating. Within the framework of the radiative transfer theory, this dissertation demonstrates that the short range correlation properties of a medium under test can be recovered by varying the size of the coherence volume of an illuminating beam. Nonetheless, the radiative transfer formalism does not account for long range correlations and current methods for retrieving the correlation function of the complex susceptibility require cumbersome cross-spectral density measurements. Instead, a variable coherence tomographic procedure is proposed where spatial coherence gating is used to probe the structural properties of single scattering media over an extended volume and with a very simple detection system. Enhanced backscattering is a coherent phenomenon that survives strong multiple scattering. The variable coherence tomography approach is extended in this context to diffusive media and it is demonstrated that specific photon trajectories can be selected in order to achieve depth-resolved sensing. Probing the scattering properties of shallow and deeper layers is of considerable interest in biological applications such as diagnosis of skin related diseases. The spatial coherence properties of an illuminating field can be manipulated over dimensions much larger than the wavelength thus providing a large effective sensing area. This is a practical advantage over many near-field microscopic techniques, which offer a spatial resolution beyond the classical diffraction limit but, at the expense of scanning a probe over a large area of a sample which is time consuming, and, sometimes, practically impossible. Taking advantage of the large field of view accessible when using the spatial coherence gating, this dissertation introduces the principle of variable coherence scattering microscopy. In this approach, a subwavelength resolution is achieved from simple far-zone intensity measurements by shaping the degree of spatial coherence of an evanescent field. Furthermore, tomographic techniques based on spatial coherence gating are especially attractive because they rely on simple detection schemes which, in principle, do not require any optical elements such as lenses. To demonstrate this capability, a correlated lensless imaging method is proposed and implemented, where both amplitude and phase information of an object are obtained by varying the degree of spatial coherence of the incident beam. Finally, it should be noted that the idea of using the spatial coherence properties of fields in a tomographic procedure is applicable to any type of electromagnetic radiation. Operating on principles of statistical optics, these sensing procedures can become alternatives for various target detection schemes, cutting-edge microscopies or x-ray imaging methods.Ph.D.
Other
Optics and Photonics
Optics
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Lesnic, Daniel. "Boundary element methods for solving steady potential flow problems and direct and inverse unsteady heat conduction problems." Thesis, University of Leeds, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.404773.
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Chen, Tzu-Fang. "Analytical and experimental studies for space boundary and geometry inverse heat conduction problems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ39790.pdf.
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Valha, Jan. "Interfacial instability and spray heat transfer problems of two phase flow." Thesis, Middlesex University, 1996. http://eprints.mdx.ac.uk/6408/.
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This thesis describes detailed investigations of two different problems in gas-liquid two-phase flow, namely, a study of interfacial stability in a partially filled cylinder subjected to vertical oscillations and a study of heat and mass transfer from hot spray droplets injected into an closed vessel. The interfacial instability study considers experimental data taken from the author's previous work. Cylinders of various diameters, partially filled with water, ethanol or glycerol were subjected to a sinusoidal vertical motion. The critical acceleration, causing the interfacial wave to grow unstable, was found to be approximately constant for a given cylinder diameter, independent on the amplitude of the forcing oscillations. The experiments also indicate that the critical Acceleration always decreases with increasing cylinder diameter. A mathematical analysis of the interfacial instability is based on a stability investigation of a Mathieu equation. It is shown that the experimental data fall into unstable regions for a single, first mode of oscillations. This finding is supported by the experimental analysis given by Cilliberto and Gollub. The analysis shows the effects of the liquid column height on the interfacial instability to be dependent on tanh (k..l.). This multiplier is equal to 1 for the column heights of 250mm, 500 mm and 750 mm, investigated, and a given cylinder diameter, thus having no effect on the results. Computational analysis of the interfacial problem is developed which is based on the simplified MAC method incorporating the Continuum Surface Force (CSF) model for simulating the effects of surface tension. Computational experiments were run for water and glycerol, the two liquids of significantly different properties. The results are presented in the form of time sequenced plots showing the interfacial positions and graphs relating the interfacial wave amplitude and time. Stability of the interface is found to be dependent on the initial surface disturbance. Growth of the interfacial wave is observed in some cases. In the range of situations investigated, surface tension effects are found to have only a small influence both on the stability and frequency of the interfacial oscillations. The period of interfacial oscillations with no forcing vibrations is found to be in good agreement with the period predicted by mathematical analysis. Influence of the initial disturbance profile was also investigated. The results indicate that the interfacial wave adopts oscillatory behaviour similar to the other cases. The oscillation frequency of the interfacial wave undergoing forcing vibrations is found to match the findings of the mathematical analysis. The wave oscillates with an angular velocity equal to the multiples of the half the forcing vibration angular velocity, co/2. In the second investigation a testing rig was constructed to investigate the heat and mass transfer processes in dense hot sprays injected into an enclosed cylindrical vessel. Heat and mass transfer rates were investigated indirectly from the measurements of the gas - vapour mixture pressure rise in the cylinder. The experiments covered different combinations of the parameters influencing the processes. The number and size of spray nozzles, the vessel volume, the type of gas and the initial pressure level in the cylinder were investigated. The experimental results indicate that, for the range of solid cone nozzles tested, the heat and mass transfer characteristics are, to a first approximation independent of the size of the nozzles. The results also show that the rise of spray chamber internal pressure is directly proportional to liquid temperature and flowrate. An analysis, based on energy balances for the whole cylinder, has yielded a new dimensionless group incorporating the important parameters of droplet heat transfer namely the droplet velocity and radius, spray chamber dimensions, gravity, conductivity and convectivity. A good match has been found between the analytical results and experimental findings. An improved analysis, incorporating the effect of evaporation from drops, is also presented. It is based on simultaneous solution of energy and mass balance equations for a single droplet. Again, good agreement with the experimental results is found. Both analyses indicate that, for this particular case of dense, evaporative spray, the Nusselt number tends to have a value equal to I.
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Chiang, Jaw-Yeong, and 江照勇. "Application of Grey Prediction to Inverse Heat Transfer Problems." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/66221404697119960269.
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博士國立成功大學
機械工程學系碩博士班
96
This article applies Grey Prediction Method of Grey System Theory to improve the problem of errors in inverse operation due to the error of temperature measurement when analyze Inverse Heat Transfer Problems (IHTP) with Reversed Matrix Method. For IHTP, this research adopted Revered Matrix Method with Linear Least-squares Error Method to construct a linear inverse model. With finite difference method, we discretized governing equation that is designed to solve IHTP to construct a linear matrix equation. Through the re-arrangement of matrix equation, the unknown conditions (such as initial conditions, boundary conditions, thermal property or geometrical shape) could be demonstrated clearly and independently. Then substitute a small amount of successive measuring points temperature into the linear inverse model and solve the problems by Linear Least-squares Error Method. The process of inverse operation only need to measure a small amount points temperature to estimate the solution of IHTP, but in practical measurement of temperature, the errors of measurement of temperature are inevitable. Such errors will affect the accuracy of estimation value of inverse operation or even lead to an erroneous results. One of improvement method is to increase the number of temperature measurement points. Certainly, more accurate results of inverse operation we want to obtain, the number of measurement points we should increase. Therefore, this research uses the Grey Prediction Method to improve the defect with a hope that significant reduction of the number of practical temperature measurement points could also obtain the same accurate results of inverse operation. The small amount of direct temperature measurement points can increase to more amount of temperature points by Grey Prediction Method, and the temperatures of those increased points could still keep the correlations with previous temperatures from direct measurement. The increased number of temperature points could replace the number of temperature points that is necessary to increase for inverse operation. In other words, Grey Prediction Method could significantly reduce the number of practical temperature measurement points while keep the same accuracy as the results of inverse operation using a great number of direct temperature measurement points.
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Tsai, Pi-Fei, and 蔡璧妃. "Estimation of transient heat transfer coefficient for 2-D inverse heat conduction problems." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/53418219955040193227.
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碩士國立成功大學
機械工程學系碩博士班
95
The study applies the method of Laplace transform and the finite difference method in conjunction with the least-squares methods, the cubic spline and the measured temperature inside the test material to predict the transient heat transfer coefficient on the boundary for the two-dimensional transient inverse heat conduction problems. For the inverse algorithm of the study, the functional form of the heat transfer coefficient is unknown a priori. The whole spatial domain is first divided into p sub-intervals. A series of connected cubic polynomial functions in space and a linear function in time are then introduced to simulate the distribution of the unknown surface heat flux over space and time for the transient inverse heat conduction problem. The study investigates into the effects of p value, the initial guesses of the unknown coefficient, the measurement locations and the measurement errors on the estimated results. The results show that when there is no temperature measurement error, a good estimation on the surface heat flux and the heat transfer coefficient can be derived with the inverse algorithm. The estimated results seem to be not very sensitive to the initial guesses, the measurement locations and the p value. Nevertheless, the predictions agree with the correct results perfectly even if there exist measurement errors, except for the long time estimations. It means that the inverse algorithm of the study presents a good accuracy.
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Wu, Li-Wen, and 吳立文. "Study on Inverse Heat Transfer Problems of Force Convection in Circular Pipe." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/30006708125431734330.
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博士國立成功大學
機械工程學系碩博士班
94
This study addresses the inverse problem of a finite cooled/heated length on the heat transfer characteristics of laminar or turbulent flows through thick-walled circular tubes. Using temperature measurements taken at several different locations within the fluid, the linear least-squares-error method is used to estimate the unknown heat flux on the external surface of the circular pipe and the unknown shape of the thermal insulation. Furthermore, the function specification method is used to estimate the time-varying inlet temperature and the outer-wall heat flux simultaneously on the basis of temperature measurements taken at two different locations within the pipe flow. While determining the steady unknown boundary conditions of the pipe flow, the present approach in this study rearranges the matrix forms of the governing differential equations, and then combines the reverse matrix method and the linear least-squares-error method. Another study about a transient inverse heat transfer problem is solved using a whole domain estimated technique with the function specification method and the linear least-squares-error method to determine the unknown boundary conditions of the pipe flow. The temperature data obtained from the direct problem are used to simulate the temperature measurement, and the influence of errors in these measurements upon the precision of the estimated results is considered. This study also considers the influence of the locations and numbers of sensors used upon the accuracy of the estimated results. The results indicate that the accuracy of the estimated results is improved by taking temperature measurements in locations close to the unknowns. The results confirm that the proposed methods are capable of yielding accurate results even when errors in the temperature measurements are present. The proposed methods provide several advantages compared to traditional methods: (1) it yields a solution within a single computational iteration, (2) no prior information is required regarding the functional form of the quantities of interest, (3) no initial guesses of the unknown parameter values are required, and (4) the inverse problem can be solved in a linear domain. This study also compares the application of the whole domain function specification method (WDFSM) and the sequential function specification method (SFSM) to the inverse problem of transient conjugate heat transfer of laminar forced convection in a circular pipe. These two inverse methods are used to estimate the time-varying inlet temperature and the outer-wall heat flux simultaneously on the basis of temperature measurements taken at two different locations within the pipe flow. The numerical results reveal that the estimations obtained from the WDFSM method are marginally better than those obtained from the SFSM approach. Finally, the performance of two classical algorithms (e.g. uniform and linear function) used in the whole domain function specification method (WDFSM) to obtain simultaneous estimates of the time-varying inlet temperature and outer-wall heat flux are compared. Additionally, this study proposes a modification to the linear assumption employed in the conventional WDFSM method to improve its estimation performance. The numerical results confirm that the proposed algorithm yields slightly more accurate estimates of the unknowns than the two classic algorithms.
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許寶東. "Study of multi-dimensional inverse heat transfer problem." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/23932317774879277014.
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Mirsepahi, Ali. "An intelligent approach to inverse heat transfer analysis of irradiative enclosures." Thesis, 2017. http://hdl.handle.net/2440/105377.
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This is a thesis by publication for a PhD degree of engineering in the university of Adelaide. The current dissertation comprises five published/submitted journal articles. Three of these journal papers have already been published in the journal of "International Communications in Heat and Mass Transfer" and one has been accepted by the editorial board of "Chemical Engineering Communications". This study, based on research undertaken in the area of Inverse Heat Transfer Problems (IHTP), aims at analyzing the applicability of Intelligent Techniques (ITs) to solve sequential (real-time) heat flux estimation class of IHTPs, especially those involving in the most complicated form of heat transfer, radiation. Currently, several optimization based methods have been developed and applied to solve heat flux estimation problems. These methods normally require detailed and accurate information regarding physical properties. Often, the measurement of such physical properties is extremely difficult, if not impossible. Moreover, all optimization-based methods require that the direct problem must be solved first. This constraint of the need for iterated direct problem solutions can produce significant computing errors and calculations may be excessively time-consuming. This thesis offers new inverse models to estimate heat flux based on a sequence of measured temperatures. The offered models developed by ITs, in accordance with the achievement of this research, only requires a series of temperature-input heat data for a few minutes of operation; the dimensions and thermophysical properties are not needed. As another significant advantage, the estimation stage by the trained ITs only includes a small number of simple calculations excluding any recursive computation; this means the method is very fast-paced in comparison with classical avenues of numerical heat transfer for similar problems. At the outset, the most general form of ITs in engineering applications, Artificial Neural Networks (ANNs), employed to formulate an inverse model in the studied furnace/dryer (see chapter 4). The promising results confirmed that ITs are sound candidates to create inverse models. In that study, some deficiencies in ANNs such as finding the relevant parameters by trial and errors motivated the authors to check GA-ANNs and ANFIS as the possible alternatives for ANNs. The comparison study between aforementioned methods (see chapter 5) provided good outlines to find the best method in different situation. As the ANNs optimized by Genetic Algorithms (GA) discovered as the best method in the chapter 5, different types of ANNs were compared to find the best one (see chapter 6) in terms of accuracy and computation time. The results demonstrated that Multilayer Perceptron (MLP) optimized by GA can perform the best among all studied ANNs. Since the literatures lack of a practical comparison between the proposed and optimization based methods, as the next phase of study, these two method were compared (see chapter 7) to reconfirm the superiority of inverse models developed by ITs. In the last stage (chapter 8), a two-input/ two-output problem defined to check the capability of the proposed method in the problems more closer to the real-world industrial applications. In short, a series of very accurate methods for inverse heat transfer problems is proposed and successfully tested using experimental data.Thesis (Ph.D.) (Research by Publication) -- University of Adelaide, School of Chemical Engineering, 2017.
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Osborne, Gregory Evan. "Novel Numerical Approaches for the Resolution of Direct and Inverse Heat Transfer Problems." 2007. http://trace.tennessee.edu/utk_graddiss/257.
Full textAbstract:
This dissertation describes an innovative and robust global time approach which has been developed for the resolution of direct and inverse problems, specifically in the disciplines of radiation and conduction heat transfer.
Direct problems are generally well-posed and readily lend themselves to standard and well-defined mathematical solution techniques. Inverse problems differ in the fact that they tend to be ill-posed in the sense of Hadamard, i.e., small perturbations in the input data can produce large variations and instabilities in the output. The stability problem is exacerbated by the use of discrete experimental data which may be subject to substantial measurement error. This tendency towards ill-posedness is the main difficulty in developing a suitable prediction algorithm for most inverse problems. Previous attempts to overcome the inherent instability have involved the utilization of smoothing techniques such as Tikhonov regularization and sequential function estimation (Beck’s future information method).
As alternatives to the existing methodologies, two novel mathematical schemes are proposed. They are the Global Time Method (GTM) and the Function Decomposition Method (FDM). Both schemes are capable of rendering time and space in a global fashion thus resolving the temporal and spatial domains simultaneously. This process effectively treats time elliptically or as a fourth spatial dimension. AWeighted Residuals Method (WRM) is utilized in the mathematical formulation wherein the unknown function is approximated in terms of a finite series expansion. Regularization of the solution is achieved by retention of expansion terms as opposed to smoothing in the classical Tikhonov sense.
In order to demonstrate the merit and flexibility of these approaches, the GTM and FDM have been applied to representative problems of direct and inverse heat transfer. Those chosen are a direct problem of radiative transport, a parameter estimation problem found in Differential Scanning Calorimetry (DSC) and an inverse heat conduction problem (IHCP). The IHCP is resolved for the cases of diagnostic deduction (discrete temperature data at the boundary) and thermal design (prescribed functional data at the boundary). Both methods are shown to provide excellent results for the conditions under which they were tested. Finally, a number of suggestions for future work are offered.
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Xu, Ming-Yao, and 許銘堯. "Study of Genetic Algorithm on Inverse Heat Transfer problem." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/12551962636922283344.
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碩士國立成功大學
機械工程研究所
84
In the last decade, the study of inverse heat conduction problem (IHCP) is an increasing branch of research. Usually, the mathematical models used in the study of IHCP is highly complicate. In the present study, a simple and novel methodology is adopted to solve the one-dimensional, trasient IHCP on the estimation of the unknown boundary conditions. This methodology used is the combination of Genetic Algorithms (GAs) with the finite difference method and the relative least square scheme. The mathematical model is simple. The advantage of GAs is that it is robust and the solution obtained is global optimum. Two cases are studied in this study. One is the estimation of the surface temperature with known form, the other is the estimation of the surface heat flux without the known form. For the latter case, we assume the surface heat flux is a polynomial with unknown coefficients, then those known coefficients are determined by using GAs. The influences of the noise, the number of simulated sensor data, and the location of the measurement are also investigated in the present study. The measurement error defined in the study is up to 5%. Results reveal that the better solution is obtained for the number of simulated sensor data is about 40 to 50. Also the more the location of the measurement point near the estimated boundary, the more accurate the estimation will be.
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Cheng, Shun-Chung, and 鄭順中. "A Three-Dimensional Inverse Heat Transfer Problem of Estimating the Heat Generation." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/91298782736976455949.
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碩士國立成功大學
造船及船舶機械工程學系
88
We used to solve the general problem of engineering by the traditional method but in many practical problems it is very difficult therefore it can be solved by inverse method. In the present study using the Conjugate Gradient Method and the general-purpose commercial code CFX4.2-based inverse algorithm to estimate the unknown heat generation solves a three-dimensional transient inverse heat conduction problem. In the chapter 2 we use the inverse algorithm to estimate the unknown heat generation in any three-dimensional irregular composite medium and in the chapter 3 to estimate the strength of heat sources for chips on the PC-Board. The advantage of calling the CFX4.2 code as a subroutine in the present inverse calculation lies in that many difficult but practical 3-D inverse problems can be solved under this construction since the general-purpose commercial code has the ability to solve the direct problem easily. Results obtained by using the conjugate gradient method to solve these 3-D inverse problems are justified based on the numerical experiments with the simulated exact and inexact measurements. It is concluded that accurate heat generation can be estimated by the conjugate gradient method except for the final time. The reason and improvement of this singularity are addressed.
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LU, WEN-SHENG, and 呂文聖. "Inverse of Resolution Heat Transfer of Electrical Discharge Machining for Two-Dimensional Nonlinear Problems." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/84450596753656856146.
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碩士國立高雄應用科技大學
模具工程系碩士班
92
This study investigates the phenomena in electric discharge machining (EDM) process which includes the relationship between the discharge energy and the machining crater outline curve, the influence of latent heat effect on the work piece, and the solution of the plasma flushing energy and the thermal conductivity coefficient. The arc, created between the work piece and the electrode in the range from a few microseconds to several hundred microseconds, produces a crater scope in this process. This crater scope, in the dimension between a few micrometers to several hundred micrometers, can be emulated by two-dimensional cylindrical coordinate by the nature of the EDM process itself presents the symmetrical type. During the machining, material will be melted by the enormous fusion heat generated in the evaporating area which will be expanded as the time increase. The solidification phenomenon will then be observed with latent heat released. This latent heat effect which causes nonlinear heat conduction problem is hard to compute by general numerical analysis, and often neglected in previous works. In this study, the average specific heat method is adopted in numerical model to effectively solve the latent heat problem. The results show the more latent heat will create the more depth of the crater. Since it is difficult to measure the inlet electric power when the arc acts on the material, however, the temperature measured from outline of crater curve in discharge process can be used to inversely solve the arc power. For the nonlinear heat transfer problem presented in this study, to the Beck’s development of the nonlinear least square method was used to deduce the numerical model, then the inlet power and the thermal physical properties can be inversely solved by this model. This study deduces the two-dimensional numerical model to simulate the EDM process. Both the direct solving and the inverse operation method were studied. The results can be contributed to the understanding of the relation of the inlet energy and the crater scope in EDM process.
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Tsung-Po, Lin, and 林宗伯. "Inverse Heat Conduction Problem of Simultaneously Determining Thermal Conductivity, Heat Capacity and Heat Transfer Coefficient." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/57886664204503793306.
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碩士大同工學院
機械工程研究所
86
This study presents a theoretical approach for simultaneously estimating the thermal conductivity(k) and heat capacity(C) of a solid body as well as the heat transfer coefficient(h) on the body surface by solving an inverse heat conduction problem. The conjugate gradient method is adopted to obtain the predicted solutions. Concerning feasibility and simplification during measurement implementation, the present approach requires the recorded temperature history only at the solid surface. Three common metals, steel (Cr 18%, Ni 8%), lead, and copper, are considered as test samples for evaluating the accuracy of the approach developed. The evaluation of the accuracy is performed based on a set of pseudo-experimental temperature data which is generated by adding a time-dependent randomly-varying disturbance to the exact solution. Effects of the physical and geometric variables, including thickness of the solid plate(L), rate of heat input(q), temperature measurement error(σ), sampling period(tp), are investigated for each metal considered.
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Hsiung, Tao-Yen, and 熊道彥. "The application of Boundary Element Method at Inverse Heat Transfer Problem." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/62383479656316285429.
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碩士國立成功大學
造船及船舶機械工程學系
87
An inverse design problem is solved to determine the shape of complex coolant flow passages in internal cooled turbine blades by using the conjugate gradient method (CGM). One of the advantages of using CGM lies in that it easily can handle problems having a huge number of unknown parameters and converges very fast. The boundary element method (BEM) is used to calculate the direct, sensitivity and adjoint problems due to its characteristics of easily-handling the problem considered here. Results obtained by using the CGM to solve the inverse problems are verified based on the numerical experiments in the analysis model. One concludes that the CGM is applied successfully in estimating the arbitrary shape of cavities and the rate of convergence is also very fast even when the number of unknown parameters is large. Moreover, the design model of the inverse problem is also performed to estimate the optimal shape of cooling passages in accordance with the desired blade surface temperature distributions.. The applications of inverse problems can be found in several engineering fields, such as the determination of boundary conditions, thermal properties, heat generation, contact resistance and thermal properties and thickness of frost on the tube of evaporator [1-4]. The purpose of the present study is to utilize the technique of inverse problem to estimate the thermal properties and thickness of frost on the tube of evaporator. This kind of problem is classfied as moving boundary problem as well as the inverse problem . In this paper the Conjugate Gradient Method is used for the numerical solution to the inverse geometry problem of identifying the unknown thickness of frost form temperature measurements, based on a boundary element method . The use of boundary element method is suggested bye the basic nature of the inverse problem (to search an unknown domain, thus an unknown surface), because domain discretization is avoided. More specifically, the advantages gained by BEM-based algorithm is the ability to readily accommodate the changes in the unknown boundary shape as it evolves from its initial to its final shape.
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Kuo, Chi-Pin, and 郭啟彬. "Inverse Combined Conduction and Radiation Heat Transfer Problem in a Two-Layer Planar Medium." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/44801808250009657866.
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碩士國立交通大學
機械工程系
88
This study presents a systematic analysis of an inverse heat conduction-radiation problem in a two-layer planar medium by applying the space-marching technique. The use of this inverse technique allows for the estimation of the internal radiation fluxes, temperature distributions, and the surface heat flux histories, from transient temperature measurements within the semitransparent layers at two positions. The present analysis considers an absorbing, emitting, isotropically scattering and gray two-layer planar medium bounded by infinite opaque, diffusely absorbing, and diffusely reflecting surfaces. The results showed that the DDO approximation method was a precision and stable method to solve both direct and inverse combined conduction and radiation problem. Moreover, the modified space-marching technique could accurately estimate the surface fluxes and temperature histories of a inverse heat conduction-radiation problem in a semitransparent single-layer or two-layer planar medium from two internal temperature measurements with exact data (predicted values) and simulated experimental data, and the accuracy wasn’t significantly influenced by the sensor locations. The performance of the presented inverse method for a given time step was investigated. Furthermore, there exists an optimal value of grid number to obtain the minimum standard deviation. For a fixed number of grid points, the inverse solutions for the radiation dominant cases are more accurate than that of the pure conduction cases, but the sensitivity to measurement errors was almost the same.