Experimental study on the temperature distribution of impingement flow in a double slope roof generated by jet fire

The double slope roof is a commonly used building structure due to its adequate drainage and stable structural features. The thermal impinging on the double slope roof generated by the jet fire caused many casualties and property damage, whose thermal hazard has not been quantified in literatures. The temperature distribution at different source-ridge heights (H), heat release rates (HRR), and roof angle (theta) was measured in the experiment, with a total of 125 sets of experimental conditions. Results show that the ceiling maximum temperature rise increases with the roof angle decreases. A maximum temperature rise prediction model was established based on the analysis of the free plume length beneath the roof, which considering the effect of theta. Moreover, the model's accuracy was validated by comparing previous experimental data. The mean deviation between the proposed model and the experimental results is less than 5.7 %. The rate of temperature decay beneath the ridge decreased as the theta decreased. When the H is smaller, and the HRR is larger, the influence of the theta on the temperature decay profile is more significant. A new correlation has been proposed to correlate the temperature decay profile of a double slope roof with different theta by introducing flame extension length to modify the characteristic radius b. The model prediction agreed well with the experimental data, with a maximum error of around 20 %. New findings are helpful in guiding the building fire prevention and detection design.