Burning Rate Model for Charring Materials.
Burning Rate Model for Charring Materials.
(4311 K)
Anderson, G. W.
NIST GCR 97-725; 93 p. August 1997.
Sponsor:
National Institute of Standards and Technology,
Gaithersburg, MD
Available from:
National Technical Information Service
Order number: PB97-205991
Keywords:
burning rate; char; fire growth; flame spread;
pyrolysis; model studies
Abstract:
A one dimensional model has been developed to describe
the processes involved in the transient pyrolysis of a
semi-infinite charring material subjected to a constant
radiant heat flux. Material properties are assumed
constant with respect to temperature and time. The
model tracks the char layer growth, thermal penetration
depth, surface temperature and mass loss rate. A review
of the physical phenomena involved in charring pyrolysis
is presented and the relevant phenomena included in the
model. the integral method is described, and an example
for constant surface heat flux is solved. The
derivation of the model divides the material into three
regions: char layer, vaporization plane, and virgin
material and the equations of conservation of mass and
energy are applied to each region using the integral
approximation with polynomial temperature profiles. The
resulting coupled, nonlinear, autonomous system of three
different equations and one algebraic equation is
suitably nondimensionalized and solved using Mathematics
(tm) software. The results generated by the model are
compared to existing models and, a method by which
effective properties for use in the model might be
deduced from experimental data is suggested.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899