Navegando por Assunto "Heat transfer"

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Acesso aberto (Open Access)
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.
Acesso aberto (Open Access)
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.