PYROLYSIS OF SOLID MATERIALS EXPOSED TO HIGH THERMAL RADIATIVE HEAT FLUX

摘要

Fire safety in buildings depends on many parameters, and inflammability of materials is among thernmost influent. In order to assess the fire hazard associated with specific materials used for furniture andrnequipment of houses or offices, experimental tests have been carried out to study their pyrolysis under highrnradiative flux. For that purpose, a range of samples including mainly fabrics and plastics were exposed tornvarious levels of radiative heat flux. The tests were achieved using a 45 kW solar concentrator, capable ofrndelivering heat fluxes up to 6 MW.m~(-2) with fully parameterized shapes, lasting from 0.3 second to severalrnhours. Samples’ masses and temperatures were measured during the tests, and a full modeling process wasrncarried out.rnPolyoxymethylene (POM-Delrin) and two PVC-based polymers cylindrical samples of 2 mm thick and 50rnmm diameter were exposed to high radiative heat fluxes from the solar furnace ranging from 300 to 4500rnkW.m~(-2). The experiments have been modeled thanks to FDS v6.1 software. This software was implementedrnwith thermo-physical properties identified with classical experimental benches. The pyrolysis law wasrnmodeled by an Arrhenius law. Two methods were used for modeling the thermal decomposition ofrnmaterials. The first way was to use fixed parameters for the activation energy and the pre-exponentialrnfactor. The second way was to make the Arrhenius parameters progressive with the conversion. Moreover,rncomposite materials or materials with several kinetic behaviors were modeled step by step (thermo-physicalrnproperties and kinetics parameters) by FDS.rnFor all tested materials, pyrolysis models were firstly validated by comparing experimental results realizedrnby thermogravimetry analysis (TGA) to FDS modeling. Then, solar furnace experiments were modeledrnthanks to FDS v6.1 and comparisons were made on front side and back side temperatures and on massrnlosses. During the first stage of the exposition, computed temperatures were showing a satisfactoryrnagreement with the experiment. After few seconds, results have been showing differences. Differences arernmore important for PVC-base polymers than for POM.