Gas emissivities and absorptivities for H2O–CO2–CO mixtures

Abstract

In this work, an approximate solution is given to compute the gas emissivities and absorptivities for H₂O–CO₂–CO mixtures. The proposed model is valid for temperatures from 300 to 2700 K and pressure path-length $\left(P_{x}L\right)$ from 0.06 to 40 atm m. In the calculation of the analytical solution (AS), the nonlinear methods of Galerkin and Ritz were implemented based on the residual solution of the differential roots of the Finite Element Method. For each point value $(P_{x}L;T)$ using the AS, the spectral absorptivity $a_{\lambda }$ and emissivity ${\epsilon }_{\lambda }$ were determined, while for the gas mixture the emissivity ${\epsilon }_m$ and absorptivity $a_m$ were computed using the Hottel Graphical Method (HGM) and the proposed method. In the emissivity calculations, the HGM shows less adjustment, with values of ±20% and ±15% for 79.1% and 56.2% of the available analytical data, while the proposed model correlates adequately with the available data, showing an average deviation of ±15% and ±10% for 91.4% and 76.2% of the available data. In the absorptivity estimations, the HGM shows a weaker fit, with values of ±20% and ±15% for 77.3% and 51.4% of the experimental data, respectively, while the proposed model shows good agreement with the available data, with a mean deviation of ±15% and ±10% for 89.8% and 74.1% of the test made.