This paper presents a comprehensive study of spectral line weighted-sum-of-gray-gases (SLW) through OpenFOAM a computational fluid dynamics (CFD) open source software. The modified OpenFOAM with SLW is evaluated through the prediction of incident heat fluxes and radiative source terms in two test problems: isothermal homogeneous water vapor and an isothermal mixture of H₂O and CO₂. To assess accuracy of the results of the SLW implementation are compared with benchmark models, including the Ray Tracing (RT) with Statistical Narrow Band Model (SNB) and Method of Lines (MOL). The comparisons between the SLW implementation in OpenFOAM and the benchmark models reveal a good agreement, confirming the accuracy of the modified code. The predictions of incident heat fluxes and radiative source terms are matching well with the reference models. Additionally, a comparison is conducted between the use of 8 and 20 gray gases, demonstrating that the results are closely matching with standard results with minor deviations.