In order to investigate the influence of changes in the thermal properties of solid combustibles on thermal pyrolysis process, a series of experiments were performed using a cone calorimeter specified in ISO 5660-1. In the present study, Poly Methyl Methacrylate (PMMA) which does not produce char during pyrolysis process was used as solid combustibles. Results obtained from the cone calorimeter experiments were compared to numerical results calculated from Fire Dynamics Simulator (FDS) pyrolysis model which adopts with the thermal properties of PMMA reported in literatures as input variables. Comparisons between experimentally measured and model-predicted mass loss rate (MLR) and heat release rate (HRR) were then made to elucidate the effect of changes in the thermal properties on the thermal pyrolysis process of PMMA.
Comparisons made between experimentalandnumerical results clearly have highlighted an importance of thermal properties of PMMA plugged in the FDS thermal pyrolysis model as a function of temperature. Both calculated HRR and MLR were found to be in good agreement with ones measured from the cone calorimeter experiments when the thermal properties of PMMA were put as a function of temperature into the model. Numerical results also clearly indicate that the thermal properties declared as constant variables using reported values at ignition temperature are useful to predict the HRR and MLR of solid combustibles during thermal pyrolysis.
In the present study, the FDS 1D pyrolysis model (which does not take combustion reactions into account) was further extended to reasonably simulate the thermal pyrolysis process after ignition. To this end, the calculated total heat flux and convective heat transfer coefficient imposed on the surface of PMMA were retrieved from numerical solution in the FDS 3D pyrolysis model (which does take combustion reactions into account) and additionally put into the FDS 1D pyrolysis model to mimic flame-like thermal environments after ignition. Numerical results clearly demonstrate that the FDS 1D pyrolysis model with retrieved data can quite well predict the HRR and MLR of PMMA, shortening the computational time for pyrolysis phenomena after ignition.