Computer Model of the Smoldering Ignition of Furniture.
Computer Model of the Smoldering Ignition of Furniture.
(2601 K)
Mitler, H. E.; Walton, G.
NISTIR 4973; 100 p. November 1992.
Available from:
National Technical Information Service
Order number: PB93-125060
Keywords:
furniture; smoldering; ignition; computer models;
mathematical models; pyrolysis
Abstract:
This paper describes a user-friendly computer model,
TMPSUB2. This model calculates the temperature field
throughout a solid (but porous) substrate which can
undergo exothermic pyrolysis, when it is exposed to an
arbitrary (localized) heat flux which can move
uniformly, such as that of a smoldering cigarette.
TMPSUB2 has successfully simulated the thermal runaway
signifying smoldering ignition of the substrate when it
is exposed to a set of external heating fluxes. The
processes taken into consideration are three-dimensional
heat conduction in the substrate, pyrolysis of the
latter, and the diffusion of air into it at the top
surface. TMPSUB2 also takes into account the fact that
the substrate consists of two layers (a foam pad covered
by a fabric), with the possibility of an air gap between
them, up to three pyrolytic reaction steps, and with
temperature-dependent thermophysical constants. TMPSUB2
solves the equations describing the physics and
chemistry of the heating and ignition process
numerically; the results have been compared with a set
of ignition experiments, and have been found to be
semi-quantitatively correct, both for the ignition
temperature and for the time to ignition. Analysis of
the experiments indicates that the substrate, which
consists of a thin fabric layer over a thick foam
padding, behaves as a thermally thin layer. Use of
TMPSUB2 shows that smoldering ignition would result from
a stationary hot spot of intensity and dimension
simulating a quietly smoldering cigarette. A users'
guide is included.
