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Computer Model of the Smoldering Ignition of Furniture.


pdf icon 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.