Analysis of Effective Thermal Properties of Thermall Thick Materials.
Analysis of Effective Thermal Properties of Thermall
Mowrer, F. W.
NIST GCR 03-855; 25 p. July 2003.
Sponsor:National Institute of Standards and Technology,
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thermal properties; ignition; thermial inertia
The standard methods used to derive effective thermal
properties of thermally thick materials based on
bench-scale radiant exposure tests are reviewed and
analyzed. These methods are compared with numerical
calculations for the same boundary conditions. These
comparisons show that the standard analytical methods
for predicting surface temperature histories are not
accurate because they either ignore heat losses from the
surface or do not adequately treat the highly nonlinear
reradiative surface heat loss term. A method is
presented for determining more accurate values for the
thermal inertia based on effective values for this term
published widely in the literature. It is found that
actual thermal inertias tend to be lower by about a
factor of 1.3 to 2.7 when compared with reported
effective values for a wide range of conditions. This
can have a significant effect on flame spread
predictions for models that rely on accurate values for
the thermal inertia.