Quantification of Flame Heat Feedback in Cone Calorimetry Tests

In order to understand material flammability, accurate pyrolysis models must be developed. Understanding flame heat feedback is essential in developing accurate pyrolysis models. The most widely used standard to quantitatively assess material flammability is the cone calorimeter. The goal of this project was to develop a spatially-resolved flame heat feedback model for 10 cm square horizontal specimens under buoyancy-driven flames to represent the conditions of the cone calorimeter and reasonably, the Fire Propagation Apparatus (FPA). Standard cone calorimeter experiments were performed on several thermoplastics in order to obtain heat release rate (HRR) and mass loss rate (MLR) data. In addition to standard cone calorimetry, side and center flame heat flux was measured under the cone calorimeter using two water-cooled heat flux gauges. The heat flux results show relatively good agreement with prior studies. Heat transfer coefficients were developed from the heat flux measurements in order to quantify heat feedback. It was found that the heat flux in the center of the burning materials is dominated by radiation and the side is dominated by convection. A two-zone heat feedback model with one convection and one radiation dominated zone was then developed, using a heat transfer correlation from the literature. The heat feedback model developed in this study will later be implemented into an in-house numerical pyrolysis model, ThermaKin