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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 (PxL) $({P}_{x}L)$ 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 (PxL;T) $({P}_{x}L;T)$ using the AS, the spectral absorptivity aλ ${a}_{\lambda }$ and emissivity ελ ${\varepsilon }_{\lambda }$ were determined, while for the gas mixture the emissivity εm ${\varepsilon }_{m}$ and absorptivity am ${a}_{m}$ 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. [ABSTRACT FROM AUTHOR]

In this work, an approximate analytical solution (AS) is presented to evaluate the radiative thermal exchange through a gaseous participating medium composed of H2O, CO2, and CO, which is valid for the product values of pressure path‐length (PL) from 0.06 to 20 atm m and temperatures (T) from 300 K to 2100 K. The Spence root weighting method is used to approximate the exact solutions. For each set of PL;T $\mathrm{PL}{\rm{;}}T$, the value of exact spectral emissivity and absorptivity ελ ${\varepsilon }_{\lambda }$ and aλ ${a}_{\lambda }$ for the gas mixture is calculated using the AS, the Hottel graphical method (HGM) and the proposed approximate solution. The weaker adjustment was achieved in the modeling of the HGM, with a mean deviation obtained of ±15% and ±20% for 43.8% and 56.3% of the data evaluated, respectively, while the best indices were obtained in the estimation of the proposed method, with a mean deviation obtained of ±10% and ±15% for 81.3% and 98.1% of the available data, respectively. In all cases, the agreement of the proposed model with the available experimental data is good enough to be considered satisfactory for practical design. [ABSTRACT FROM AUTHOR]