Modeling fire-induced radiative heat transfer in smoke-filled structural cavities

Abstract Accurate heat transfer prediction is important to structural fire engineering in order to analyze thermal–mechanical behavior of structures in fire. However, the presence of cavities and participating media complicates radiative calculations. A numerical approach with finite element and discrete ordinates method is presented in this paper to predict fire imposed radiative heat fluxes to these type of structural members. This approach is used to simulate heat transfer to unprotected steel I-sections with symmetrical cavities exposed to post-flashover fires. Results show that the cavity geometry could strongly attenuate the radiative energy, while the presence of hot smoke enhances radiative transfer by emission. Average radiative fluxes for inner surfaces of the I-sections are seen to increase with smoke opacity. In addition, the radiative fluxes are observed to decrease faster for I-sections with higher section factors. This work also shows that the self-radiating mechanism of I-sections is important in the optically thin region, and existing methodologies neglecting these physics could significantly underpredict steel temperatures.