Experimental study of downstream local heat flux of pool fires under relatively strong cross flows

Abstract

Pool fire is the common form of combustion posing hazard to surroundings by thermal heat transfer. The local heat flux of pool fire under relatively small cross flow has been widely studied. However, none work investigates the influence of relatively strong cross flow to the local heat flux of pool fires. In this study, experiments are carried out to reveal the effect of strong cross flow on the downstream heat flux distributions of pool fires. Four square quartz sand boxes with the side lengths of 8 cm, 10 cm, 15 cm, and 20 cm are applied to simulate the pool fires. The cross flow speed ranges from 0 to 5.0 m/s. Eight local heat flux gauges are aligned downstream with 6 cm interval. In still air or when the flame base drag is smaller than the distance (6 cm) between the closest heat gauge and downstream pool rim, the heat flux decreases monotonically with the downstream distance. For other conditions, the local heat flux firstly increases then decreases with the downstream distance. And the location of peak local heat flux is the same as the flame base drag length. For a given pool size and heat release rate, the evolution of local heat flux with cross flow speed is complicated and shows three trends. Local heat flux is determined by the flame base drag representing the influence of pool dimension, cross flow speed, heat release rate and side entrainment, as well as downstream distance. Two regions of local heat flux are observed based on the different physics of heat transfer. Correlations are obtained for the two regions respectively and agree well with the experimental data.