Radiative heat transfer for modelling fire and fire suppression

Non-grey radiation modelling of non-scattering gas-phase combustion products is considered within the frame of FireFOAM, the turbulent flame solver part of the open source CFD platform OpenFOAM®. FireFOAM's built-in finite volume-based radiation solver (FVM) was modified to account for banded solutions of the radiative transfer equation (RTE). The author implemented six gas radiation property models: two grey and three non-grey variants the weighted-sum-of-grey-gases (WSGG) and a 'box' model based on the exponential wide band model (EWB), specially optimised for fire scenarios. The models were first tested and validated in a series of canonical pure-radiation scenarios, then used for runtime radiation calculations in large eddy simulations (LES) of methanol and heptane pool fires based on the experiments of Klassen and Gore (1992) and Weckman and Strong (1996), where the effects of turbulence-radiation interaction (TRI) were discussed. Finally, the author coupled the box model with a Mie theory-based radiation model accounting for the scattering and absorbing/emitting properties of lagrangian objects such as water droplets, ultimately to be used in future, full-physics fire suppression CFD simulations. The thesis highlights the fact that the differences in accuracy between the grey and non-grey approaches are less striking in the canonical pure-radiation scenarios than in the fire simulations. However, the non-grey WSGG approach offers much potential for fires where the mean beam length cannot be trivially estimated. Older and more CPU-efficient WSGG correlations performed just as well as newer ones in this particular open boundary fire context. The optimised box model offered CPU performance that is comparable to WSGG, and coupled with the Mie model, it showed promising results in a two-non-grey-phase radiation context. Overall, this work has been largely useful for the community of FireFOAM scientists and engineers (who now have access to these new gas radiation models via the Github repository), but also it has contributed to a better assessment of such well-known radiation models in fire scenarios that are more practical for CFD engineers seeking all-in-one solutions, than the decoupled approach usually favoured in radiation work