Fire/Arson Investigations : Fire/Arson Investigations
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Re: Pyrophoric Carbonization
Posted by: dcarpenter (IP Logged)
Date: January 25, 2018 09:22AM
The 200 degrees C is associated with a specific boundary condition. The 80 degrees C is associated with a different boundary condition. These are different hypotheses that based on the theory of self-heating are not interchangeable.
In my review of the antidotal evidence of these types of fires, the common element is a heat source passing through a wood void space. So this second boundary conditions applies. How low a temperature that will allow this to occur under a specific set of circumstances is ruled by specific heat transfer. That is, in order to increase the temperature inside the void space from a heat source, the rate of heat generation must be greater than the heat losses at the boundaries. This positive net rate of thermal energy will be different for different configurations, heat sources, and type of wood. Thus, a model is needed for prediction. The model would need to include some type of chemical kinetics sub-model to predict the thermal energy release rate of the wood.
Douglas J. Carpenter, MScFPE, CFEI, PE, FSFPE
Vice President & Principal Engineer
Combustion Science & Engineering, Inc.
8940 Old Annapolis Road, Suite L
Columbia, MD 21045
(410) 884-3266
(410) 884-3267 (fax)
www.csefire.com
In my review of the antidotal evidence of these types of fires, the common element is a heat source passing through a wood void space. So this second boundary conditions applies. How low a temperature that will allow this to occur under a specific set of circumstances is ruled by specific heat transfer. That is, in order to increase the temperature inside the void space from a heat source, the rate of heat generation must be greater than the heat losses at the boundaries. This positive net rate of thermal energy will be different for different configurations, heat sources, and type of wood. Thus, a model is needed for prediction. The model would need to include some type of chemical kinetics sub-model to predict the thermal energy release rate of the wood.
Douglas J. Carpenter, MScFPE, CFEI, PE, FSFPE
Vice President & Principal Engineer
Combustion Science & Engineering, Inc.
8940 Old Annapolis Road, Suite L
Columbia, MD 21045
(410) 884-3266
(410) 884-3267 (fax)
www.csefire.com
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