Heat transfer to a burning ceiling with intermittent flame impingement

Experiments were carried out to quantify the heat flux and the temperature profile to a ceiling from floor fires, ceiling fires and combined floor/ceiling fires. The floor fire was created by using a sand burner, and the ceiling fire was created using a water-cooled sintered bronze burner. Propane was used for both burners. The results showed that when a floor fire was present, momentum from impingement dominated the flow behaviour. This allowed the flow conditions at the ceiling to be treated using the existing scaling approaches for an impinging plume. However, the thermal conditions at the ceiling were strongly influenced by the heat release due to the ceiling burner. Flame extension on the ceiling was correlated with the dimensionless ceiling fire size, and this was used to normalise the excess temperature and heat flux. Correlations to modify existing correlations for temperature and heat flux are proposed. • Ceiling flow in combined ceiling and floor fires is driven by the buoyant plume. • Thermal conditions are strongly influenced by the ceiling fire. • Thermal conditions can be scaled with flame extension.