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Navegando por Assunto "Transferência de calor"

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    Análise computacional do fenômeno de transferência de calor em paredes divisórias do tipo dry wall
    (2007-06) ALVES, Maurício Coelho; BATISTA, Eduardo de Miranda
    The present work aims to give a contribution to the study of cold–formed steel members under fire condition. Specifically, the heat transfer in light steel framed walls with or without thermal insulation was studied. For this, computational models are applied to obtain, with acceptable precision, the values of temperature in any position of the structural system. In this way, it will be possible to describe the temperature distribution (uniform or non–uniform) over the cross–section of the studs that constitute the panel, giving subsidies for stability and pos–buckling analyses of the structural members. The numerical simulations of heat transfer are developed with the aid of computational programs ABAQUS and SAFIR, both based on the finite element method.
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    Análise da convecção natural no escoamento laminar em cavidades parcialmente preenchidas com meios porosos utilizando transformadas integrais
    (Universidade Federal do Pará, 2016-04-15) QUARESMA, Sil Franciley dos Santos; MACÊDO, Emanuel Negrão; http://lattes.cnpq.br/8718370108324505; QUARESMA, João Nazareno Nonato; http://lattes.cnpq.br/7826389991864785
    A numerical study is performed to analyze the natural convection in a vertical rectangular enclosure that is partially filled with a porous medium, by the Generalized Integral Transform Technique (GITT). The first studies concerning flow transient in a channel partially filled with porous medium without the effect of natural convection in order to understand the technical solution or problems with interfaces. Two different formulations were studied: the two-domain approach and the single-domain approach. Subsequently a numerical study is performed to analyze the steady-state thermal natural convection fluid flow and heat transfer in a vertical rectangular enclosure that is partially filled with a porous medium. The flow is modeled using the Brinkman- Forchheimer extended Darcy and energy conservation equation was used to predict the heat transfer. The mathematical description of the problem is based on a one-domain formulation of the conservation equations. Finally it carried out the study of double diffusive natural convection, also nominated thermosolutal natural convection in partially porous enclosures. The validity of the so-called one-domain approach used in this case compared to existing results in the literature. A particular class of problems dealing with thermal and double diffusive natural convection mechanisms in partially porous enclosures is presented, and it is shown that this configuration exhibits specific features in terms of the heat and mass transfer characteristics.
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    Aplicação da extrapolação de Richardson na otimização de problemas em fluidodinâmica computacional
    (Universidade Federal do Pará, 2020-02-03) SANTOS, Alexandre Marcus Madeira; MAGNO, Rui Nelson Otoni; http://lattes.cnpq.br/9017163598972975
    The present work aims to investigate the application of the Richardson Extrapolation (ER) method as an alternative to reduce the simulation time of a specific CFD problem, which is related to a convective and diffusive problem. The geometry under study was built in the Blender software. The initial and boundary conditions were set using the BlenderFDS program, the calculation was done with a CFD code called Fire Dynamics Simulator (FDS), the results were extracted with smokeview software. In addition, Richardson extrapolation code was developed in the Fortran programming language. Flow field properties such as specific mass, pressure, temperature and velocity were calculated for three mesh sizes with and without the RE method. The extrapolated results show promise for maintaining accuracy at a lower computational cost.
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    Finite approximate controllability for semilinear heat equations in noncylindrical domains
    (2004-09) MENEZES, Silvano Dias Bezerra de; FERREL, Juan Bautista Límaco; MEDEIROS, Luiz Adauto da Justa
    We investigate finite approximate controllability for semilinear heat equation in noncylindrical domains. First we study the linearized problem and then by an application of the fixed point result of Leray-Schauder we obtain the finite approximate controllability for the semilinear state equation.
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    Influência da convecção termossolutal na transição colunar/equiaxial em ligas Al-Si sob condições unidirecionais e transitórias de extração de calor
    (Universidade Federal do Pará, 2011) MOUTINHO, Andréa Moreira; MOREIRA, Antonio Luciano Seabra; http://lattes.cnpq.br/0667768010106721
    The macrostructure of cast ingots consists of three different zones, that is, the chill, columnar, and equiaxed zones respectively. The origin of each one has been the subject of numerous experimental and theoretical researches in the field of metallurgy because of the well-known correlation between grain structures and mechanical properties. The structure is almost determined in the solidification process, so it is essential to control the solidification process. Despite this effort there is as yet no way that the macrostructure of an ingot can be predicted nor even any clear agreement on how the columnar to equiaxed transition (CET) actually occurs. The CET during solidification has been studied for many years and experimental observations show that the position of the CET and the size of the equiaxed grains is dependent on thermal conditions associated with the casting process including alloy system, alloy composition, melt superheat, mold temperature, mold material, heat-transfer coefficients at the metal-mold interface, cooling rate, casting size, melt convection, transport of solute, and the concentration of nucleating particles. The objective of this contribution is the presentation of experimental results on the CET in three hypoeutectic Al-Si alloys during the horizontal unsteady-state directional solidification in a cooled mold. The thermal contact condition at the metal/mold interface was also standardized with the heat extracting surface being polished. Thermocouples have been connected with the metal, and the time– temperature data have been recorded automatically. A combined theoretical and experimental approach is applied to quantitatively determine the solidification thermal parameters such as transient heat-transfer coefficients, tip growth rates, thermal gradients, and cooling rates which affect the structure transition. The experimental and calculated values have shown a very good agreement. A comparative study between the results of this article and those from the literature proposed to investigate the CET during upward vertical solidification of Al-Si hypoeutectic alloys is also presented.
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    Soluções híbridas por transformadas integrais para o escoamento magnetohidrodinâmico com transferência de calor em canais de placas paralelas
    (Universidade Federal do Pará, 2015-06-26) PONTES, Fábio de Andrade; QUARESMA, João Nazareno Nonato; http://lattes.cnpq.br/7826389991864785
    The present study is to analyze the dynamics of the magnetohydrodynamic flow of electrical conductors newtonian fluids within a parallel flat plate channel subjected to a uniform external magnetic field, wherein the mathematical formulation of the model is given in terms of stream-function, obtained from the Navier-Stokes equations and the Energy Equation. The adopted assumptions are steady state, laminar and incompressible flow and constant physical properties. It is also admitted that the external magnetic field applied in the normal direction of flow remains uniform, not being thus influenced by any internal magnetic effect. For the solution of the governing equations, the Generalized Integral Transform Technique (GITT) is applied to this system of partial differential equations and a hybrid solution (numerical and analytical), which is computationally implemented using the programming scientific language FORTRAN 90. In order to illustrate the consistency of the integral transformation, convergence analysis is performed and presented. Results for velocity and temperature fields as well as potential correlates are generated and compared with the literature on the basis of the main parameters of government. An in-depth analysis of parametric sensitivity of the main dimensionless parameters such as the Reynolds number, Hartmann number, Eckert number, electric parameter and Prandtl number for some typical situations is performed.
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