O método k-médio em conjunto com o método de distribuição-k para simulações da transferência de calor por radiação em meios participantes não-uniformes

Abstract

Thermal radiation is a very important mechanism of heat trasnfer in processes that contains participating gases, as CO2 and H2O, at high temperature. However, exact lineby- line solution of radiation heat transfer in participating media is highly computer time consuming due to the dependence of the radiative properties with the wavenumber. A manner to approach such a problem is employing k-distribution methods, as FSK and SLW, which are exact when applied to uniform media, but have limitations in the treatment of non-uniform media. The application of the FSK method to non-uniform media requires the k-correlated assumption (resulting in the FSCK method). This leads to error due the fact that the absorption coefficients of real media are not truly correlated. Therefore, this work proposes and investigates a new approach to solve non-uniform media using the FSK method and which does not require the k-correlated assumption. The FSK method applied with this new approach was labeled FSAK (Full spectrum averaged-k distribution). The method was used to solve a series of problems involving gases composed of CO2 and non-participating species. The results obtained with the FSAK method were more accurate when temperature and species mole fraction gradients where high. It has also been verified that different procedures can be used to average the absorption coefficient, and that the procedure highly influences the accuracy of the results, indicating that averaging procedures to increase the method accuracy could be found in further research works.