Navegando por Autor "Vielmo, Horácio Antonio"
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Artigo Comparison of the standard weighted-sum-of-gray-gases with the absorption-line blackbody distribution function for the computation of radiative heat transfer in H2O/CO2 mixtures(Elsevier, 2008-07) Maurente, André Jesus Soares; Vielmo, Horácio Antonio; França, Francis Henrique RamosThis paper presents the computation of radiation heat transfer in a cylindrical enclosure in which the dimensions, the chemical species concentrations and the temperature fields make a realistic representation of an actual combustion chamber. Two gas models are applied and compared: the absorption-line blackbody distribution function (ALBDF), and the standard weighted-sum-of-gray-gases (WSGG) based on coefficients and correlations that are widely used in engineering. While the standard WSGG is restricted to the assumption of homogeneous gas mixture, the ALBDF can be applied to both homogeneous and non-homogeneous media. For the two gas models, the radiative exchanges are computed with the aid of the Monte Carlo method. The results show considerable discrepancies between the WSGG and the ALBDF models for the homogeneous medium. In addition, the importance of considering the non-homogeneity of the medium for an accurate computation of the radiative heat transfer is shown. r 2008 Elsevier Ltd. All rights reservedArtigo A Monte Carlo implementation to solve radiation heat transfer in non-uniform media with spectrally dependent properties(Elsevier, 2007-11) Maurente, André Jesus Soares; Vielmo, Horácio Antonio; França, Francis Henrique RamosThis paper presents the application of the Monte Carlo method to solve the radiative heat exchange in non- homogeneous, non-isothermal gases with spectrally dependent properties. Among others models, the absorption-line blackbody (ALB) distribution function, originally defined and derived for the spectral line-based weighted-sum-of-gray-gases (SLW) model, allows an immediate, simple implementation of the Monte Carlo method to account the spectral dependence of the radiative properties. This work shows how the Monte Carlo method can be combined to the ALB distribution function, and provides results for heat transfer in a mixture of water vapor, carbon dioxide and nitrogen that have satisfactory agreement with the SLW method and with line-by-line integration. Finally, the solution technique is employed to solve two examples aiming at demonstrating the effect of the absorbing species concentration on the thermal radiative exchanges. The method is of great interest for the computation of radiative transfer in combustion systems where the chemical species concentration and the temperature are not uniform