Hubert Biteau

Calculation methods for the heat release rate of materials of unknown composition

The Heat Release Rate (HRR) is a critical parameter to characterise a fire. Different methods have been developed to estimate it. The most widespread techniques are based on mass balance. If the heat of combustion of the fuel is known, the measure of the mass loss allows its evaluation. If the burning material can not be identified, calorimetric principles can be used. They rely on oxygen consumption (OC) or carbon dioxide and carbon monoxide generation (CDG) measurements. Their asset comes from the observation that the amount of energy release per unit mass of O2 consumed or per unit mass of CO2 produced is relatively constant for a large number of materials. Thus, an accurate HRR can be obtained without knowing the composition of the burning fuel. The aim of this work is to assess this last statement and define how essential the knowledge of the chemistry to calculate HRR for complex materials such as polymers including fire retardants and/or nanocomposites, energetic materials or pine needles is. This assessment ends in an OC and CDG calorimetry comparison of several materials in order to investigate the propensity to determine whether converging or diverging HRR results when average energy constants are used. Copyright

Comparison of Pyrolysis Behavior Results between the Cone Calorimeter and the Fire Propagation Apparatus Heat Sources

The cone calorimeter and the Fire propagation apparatus are often used to carry out flammability analyses of materials. Among the numerous differences between these two devices, the impact of the heat sources has been studied by other means that time to ignition measurements as performed in past studies. In particular, visual observations, mass loss rate and temperature measurements are used to analyze the impact on the pyrolysis behavior of the two types of heaters on clear PMMA and wood samples. The mechanism, of in-depth radiation absorption and the wavelength dependency of this one are the main reasons for the different pyrolysis behavior observed.

Ability of the Fire Propagation Apparatus to characterise the heat release rate of energetic materials.

Energetic materials encompass a wide range of chemical compounds. They react very rapidly releasing large amounts of energy. One of their peculiarities is that they carry an oxidizer and do not require oxygen from the air as their primary reaction partner. The aim of this paper is to present an analysis of the ability to estimate the heat release rate of a sample energetic material using two calorimetric methodologies. The methods are based on Oxygen Consumption and Carbon Dioxide Generation principles. Data have been obtained from experiments carried out with the Fire Propagation Apparatus. First, results from smoke powder combustion tests reveal significant discrepancies between the two approaches. Results from a sensitivity analysis realised in a previous work underlined that the most likely parameters to alter the heat release rate estimation are the energy constants and the concentration of oxygen. Correction procedures have been developed; one based on the estimation of the amount of oxygen supplied by the oxidizer, and a second one based on the calculation of new energy constants accounting for the chemical decomposition of the tested materials. Results are presented in this study.