Eventos Anais de eventos
COBEM 2017
24th ABCM International Congress of Mechanical Engineering
WSGG correlations for H2O and CO2 in high pressure conditions
Submission Author:
Francis França , RS , Brazil
Co-Authors:
Felipe Ramos Coelho, Francis França
Presenter: Felipe Ramos Coelho
doi://10.26678/ABCM.COBEM2017.COB17-1025
Abstract
Thermal radiation is often a very important heat transfer mechanism in high pressure combustion processes due to the presence of participating media and the high temperatures involved. Solving thermal radiation in participating media is a tough problem due to the integro-differential governing equation and the complex spectral dependence of radiation properties. Currently, the most accurate method to solve the spectral integration is the line-by-line (LBL) method, which has a very high computational cost. In order to avoid this drawback the spectral problem is usually solved using spectral models, and as a consequence the radiative transfer equation (RTE) is simplified. One of the models is the weighted-sum-of-gray-gases (WSGG) which replaces the highly irregular spectral behavior of the absorption coefficient by bands of uniform pressure absorption coefficients, and has shown great performance in a lot of applications even though it is a very simple model. However, recently some authors didn’t have good results when trying to apply the WSGG to high pressure combustion problems. This paper develops a WSGG model for both CO2 and H2O on high pressure conditions. In order to validate the model the total emittance is calculated using the WSGG coefficients and compared to the LBL solution which was obtained using the HITEMP 2010 spectral emissivity database. The results showed that the emittance values from both methods were very close even for high pressure values for both CO2 and H2O proving that the WSGG method is applicable to high pressure conditions. A second validation was made through results of radiative heat flux and heat source and compared to the LBL solution with acceptable deviations. The effect of pressure on LBL solution showed that both radiative heat flux and heat source increased more than 100% from 1 atm to 10 atm, and more than 150% from 1 atm to 40 atm. The WSGG method presented lowest deviations for CO2 at 40 atm proving that the method is accurate for CO2 at high pressure values while for H2O it presented an opposite behavior.
Keywords
thermal radiation, weighted-sum-of-gray-gases, line-by-line, high pressures
