Effects of pool size and spacing on burning rate and flame height of two square heptane pool fires

•Experimental study on burning of two heptane pools in free space was conducted.•Square pool side length and spacing were changed.•Both the fuel burning rate and flame height changed non-monotonically with spacing.•A correlation for predicting the flame height of two pool fires was developed.•The burning rate was qualified based on the energy balance of fuel surface. The interaction of multiple pool fires might lead to higher burning rate and flame height than single pool fire, raising the possibility of fire ignition and flame spread and increasing the risks to people, buildings and environment. To quantify the burning rate and flame height of multiple pool fires from the view of physical mechanism, this paper presents an experimental study on two identical square pool fires. Heptane was used as fuel. The pool size and spacing were varied. Results showed that both the burning rate and flame height change non-monotonically with spacing. From the view of air entrainment, a correlation for the flame height of two pool fires is developed involving pool size, spacing and the flame height of zero spacing. The comparison with experimental results shows that the developed correlation is suitable for two heptane or propane fires. A theoretical study based on energy balance at one of the pool surfaces is performed to evaluate the burning rate of two fires, which is finally expressed as a function of pool size, spacing, burning rate and the flame height of single fire. The proposed model is validated using the experimental and literature data, which presents a reasonable reliability.