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Abstract
A critical factor in the fire endurance of a wood member is its rate of charring. Most available charring rate data have been obtained using the time-temperature curves of the standard fire resistance tests (ASTM E 119 and ISO 834) to define the fire exposure. The increased use of heat release calorimeters using exposures of constant heat flux levels has broadened the available database on wood charring. This paper presents such char rate data obtained with an Ohio State University (OSU) calorimeter. Results include char depth versus time models, char rates as function of other parameters, and temperature profiles in the remaining uncharred wood. Several investigators have measured charring rates for fixed heat fluxes. Butler (1971) reviewed such data and found charring rate to be directly proportional to the incident flux for the range of 20 to 3000 kW/m2. Nussbaum (1988) used a cone calorimeter to obtained charring rates for wood impregnated with low concentrations of fire retardants. Also with a cone calorimeter, Mikkola (1990, 1991) obtained charring rates for a variety of wood products at 50 kW/m2 and for spruce at fluxes of 25 to 75 kW/m2. Other charring data for specific constant heat fluxes have been reported by Fredlund (1988) and Cramer and White (1993).
Keywords
Calorimeters,
Calorimetry,
Testing,
Burning,
Fire testing,
Charring,
Fire endurance,
Pine,
Basswood,
Redwood,
Red oak
Citation
White, R. H.; Tran, H. C. 1996. Charring rate of wood exposed to a constant heat flux. Wood and fire safety : 3rd International Scientific Conference: proceedings, May 6-9, 1996, The High Tatras, Slovak Republic. [Zvolen, Slovak Republic] : Technical University of Zvolen, Faculty of Wood Technology, 1996.:p. 175-183.
