Experimental study of heat loss and heat feedback of pool fire of millimeter to centimeter fuel thickness

Abstract

The leaked liquid fuel has the potential to form a pool fire due to the boundary. The thickness of the fuel (δ) may transition from the millimeter-level to the centimeter-level over time as it leaks. In cases where the pool fires have a δ at the millimeter-level, it is important not to ignore heat loss from the fuel to the substrate, as this can significantly impact both heat transfer and heat feedback evolution. Experiments were conducted to investigate the heat loss and feedback of n-heptane pool fires with varying δ and pool diameters (D). Results showed that the fuel burning rate remains constant whereas δ will vary if the flame is in the steady burning stage. As δ increases, both convection and radiation losses absorbed by the substrate decrease rapidly before decreasing slowly. Smaller values of δ or larger D can result in a greater percentage of heat loss. The effect of heat loss on heat feedback was revealed, and a dominant control mechanism (DCM) for heat feedback was identified for values of δ ranging from millimeters to centimeters with D. As D increases, when δ≤5.0 mm, DCM transits from convection to radiation; when δ=5.0∼10.0 mm, DCM transits from radiation to convection, then to radiation; when δ≥10.0 mm, DCM transits from conduction to convection, then to radiation again. As δ increases, when D ≤ 5.0 cm, DCM transits from convection to radiation, then to conduction; when D continues to increase, DCM is always convection (D = 5.0∼10.0 cm) or transits from convection to radiation (D = 10.0∼20.0 cm). When D ≥ 20.0 cm, DCM is always radiation.