EXPERIMENTAL STUDY ON PYROLYSIS OF A HEPTANE POOL FIRE IN A REDUCED-SCALE COMPARTMENT

Among all the experimental works performed earlier for the purpose of determining the energy balance at the pool fire surface in compartm ents, no study has been reported yet dealing with the measurement of total heat flux rec eived by the fuel surface taking into account heat transfer enhancement due to hot gases and compartment surfaces. This paper presents experimental results of the burning behavi our of a heptane pool fire in a reduced scale compartment equipped with a mechanical ventilation network. The objective of this work is to study heat flux of the flame at the hept ane surface in a vitiated environment formed with air and combustion products gases. Measurements of heat fluxes, fuel mass loss rate, oxygen concentration and temperature are performed for a 0.3 m diameter pool fire for different ventilation flows rate. An original metho d to separate effects of the radiant heat flux of the flame and of the external heat feedback to t he fuel surface is developed by the way of using an additional heat flux measurement located u nder the pool fire. The results show that the fuel mass loss rate, flame temperature and heat fluxes to the fuel surface decrease as the oxygen concentration measured near the fuel decreas es by varying the air refresh rate of the compartment. The flame radiation fraction shows similar behaviour whereas the convection fraction of the total heat flux received by the fue l increases when oxygen concentration decreases. It is also shown that the contribution o f the radiant heat flux of the flame is not so small and cannot be neglected against the convectiv e heat flux and external heat feedback from smoke and compartment surfaces even if oxygen concentration decreases and reaches a low value. Based on these experimental findings, it is discussed that any analytical approach conducted to predict the fuel mass loss rate in a s imilar confined compartment should consider variations of the total flame heat flux, i ncluding convective and radiant component, against oxygen concentration.

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