Experimental Studies on the Heat Flux of Individual Firebrands
Amy Mensch, Savannah Wessies, Anthony Hamins, Jiann C. Yang
Every year, thousands of wildfires burn all over the world threatening lives and property in the wildland-urban interface. These wildland-urban interface fires spread by radiation, direct flame contact, or firebrand transport. Firebrand exposures are a significant cause of structural ignitions and have a significant impact at considerable distances from the fire. While firebrand ignition has been demonstrated in experiments, current fire models cannot accurately predict the threat of firebrand ignition to structures. One of the missing pieces for such a model framework is a thorough characterization of the heat transfer of glowing firebrands to structural surfaces. The current study uses a thin skin calorimeter to conduct measurements of the heat flux from individual firebrands. Generally, thin skin calorimeters are used to quantify only the radiative heat transfer to a surface from a fire exposure. In this work, we present results for the peak and total heat flux from a firebrand to an inert substrate in direct contact with the thin skin calorimeter. Using a propane burner, a disc-shaped piece of wood is used to generate consistent glowing firebrands, which are then placed on the thin skin calorimeter installed flush with the substrate. Previous studies on firebrand ignition of substrates have observed the effects on ignition propensity with variation in wind speed and wood type. The thin skin calorimeter experiments allow investigation of the impact of these factors on the firebrand heat transfer, which directly correlates to ignition. These experiments examine the effects of different firebrand wood types and wind speeds on peak heat flux, total heating, and duration of heating from the firebrand. These results will allow for the development of more accurate firebrand models and, in general, a better assessment of the hazard posed by firebrands in different scenarios.
, Wessies, S.
, Hamins, A.
and Yang, J.
Experimental Studies on the Heat Flux of Individual Firebrands, 13th US National Combustion Meeting, College Station, TX, US, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=936167
(Accessed September 25, 2023)