Accurate calculations of heat release in fires

Fire is often considered as the most hazardous accidental event which may affect safety in the chemical industries. The fire damage may be thermal or non thermal. As examples, the fire plume may transport a variety of toxic effluents, which may injure the staff of the industrial premises and the fire fighters, as well as the inhabitants in the neighbourhood. Intense radiation produced by big fires may cause serious burn injuries and generate "domino effects" to previously non affected equipment in the vicinity and result in related phenomena such as jetfires, fireballs, BLEVEs1 . Moreover, polluted extinction waters while unconfined may greatly affect the aquatic environment. Although several ambitious projects were recently carried out in the field, there is still much work to be performed to get validated techniques capable of predicting (and keeping under acceptable control) the consequences of indoor and outdoor large chemical fires

A zone model for the prediction of thermal and chemical effects of a pool fire in a forced ventilated enclosure

Zone models have been developed since the early 60s for the prediction of fire parameters such as smoke temperature, smoke filling and movement in multi-compartment buildings. Unfortunately, one major difficulty in current zone models is that heat and chemical species release rates in relation with a given fire source term are usually to be provided as input data. A new zone model for prediction of thermal and chemical effects of pool fire in a forced ventilated enclosure has been developed

La qualité : des concepts à la pratique

Introduction La référence à la « qualité » n’est pas neuve. Mais elle s’exprime aujourd’hui dans une acception spécifique, voire technique, en de nombreuses occasions et dans bien des domaines. Des normes internationales lui sont consacrées, des modèles, simples ou moins simples, sont proposés à son sujet. Les rayons des librairies s'encombrent d'ouvrages généraux, de livres introductifs, de bouquins spécialisés,… qui prétendent vous apprendre, en cent pages ou en mille, le what's what de la ..

Chemfire : a zone model for predicting chemical effects of pool fire in a single forced ventilation enclosure

International audienceZone models have been developed since the early 60s for the prediction of fire parameters such as smoke temperature, smoke filling and movement in multi-compartment buildings. Unfortunately, one major difficulty in current zone models is that heat and chemical species release rates in relation with a given fire source term are usually to be provided as input data. A new zone model for prediction of thermal and chemical effects of pool fire in a forced ventilated enclosure has been developed. The novelty of the approach relies in particular on the provision of three sub-models that are used for reducing the number of input data needed for a given simulation. The burning rate history of liquid pool fire is calculated from a vaporisation sub-model. A solid flame sub-model is used for predicting radiative properties of flame. Yields of chemical species are estimated from a dedicated sub-model of combustion. This zone model has received some validation for use in forced ventilated enclosures only. Promising results have been obtained

Improvement of the hazard identification and assessment in application of the Seveso II Directive

International audienceThe Council Directive 96/82/EC of 9 December 1996 on the control of major-accident hazards involving dangerous substances, known as SEVESO II Directive, aims at the prevention of major accidents and the limitation of their consequences for human beings and environment. Although rules are well established to identify potential risk, there is no method to measure the risk level which takes into account safety devices and safety management systems implemented by operators. This paper deals with the first stage of a global methodology that aims to better assess benefits form safety devices and safety management systems through accident scenario selection

Sooth generation in fires : an important parameter for accurate calculation of heat release

Oxygen consumption (OC) calorimetry and carbon dioxide generation (CDG) calorimetry are usual methods to determine the heat release rate (HRR) in bench-scale and large-scale fire tests. The paper emphasises on measuring problems associated with fires releasing large amounts of soot. Until now, the soot-related energy transfer was hardly ever taken into consideration in practical applications of HRR calculations. From standard CDG calorimetry, a generalised relationship is introduced in order to take into account the soot generation in the accurate determination of the heat release produced in sooty fires. The analysis of the significance of this correction factor is discussed by theoretical consideration as well as from results of lab-scale experiments recently carried out on chemicals by means of the INERIS fire calorimeter

The effect of oxygen concentration on CO yields in fires

International audienceIn addition to global ventilation effects on fires, vitiation of air is a ventilation related phenomenon that can also affect the generation of chemical species in a built environment. The paper is a contribution to the study on the subject. Experiments were performed at lab-scale with the Fire Propagation Apparatus in order to study the effect of air vitiation on the CO yield. Results are also presented for the fuel burning rate. Both carbon dioxide and nitrogen were used as diluents in the inlet air flows. The oxygen concentration was decreased stepwise until the extinction point was reached. A first set of experiments was performed in well-ventilated fire conditions (equivalence ration between 0.1 and 0.25). A second set of experiments was carried out in under-ventilated fire conditions (equivalence ratio equal to 1.1). The results revealed useful for improving the combustion sub-model predictions in a zone model under development

A two-thermocouple probe for radiation corrections of measured temperatures in compartment fires

International audienceBare-bead thermocouples are widely used for measuring temperature fields in compartment fires. It is well-known that temperature readings using such a device call be significantly affected by radiation errors, the apparent thermocouple junction temperature being thus different from the true gas temperature. However, a probe consisting of two thermocouples of unequal diameters, but made of the same material can be used for estimating the gas temperature in a fire environment. Using a steady-state heat transfer model applicable to a bare-bead thermocouple, a very simple rule is proposed for the estimation of radiation errors when temperatures are measured by use of two thermocouples of different diameters. Radiation errors obtained from this simple rule are compared and discussed with experimental results involving a compartment fire with pyridine as the fuel

The effect of oxygen concentration on CO and soot yields in fires

International audienceIn addition to global ventilation effects on fires, vitiation of air can also affect the generation of chemical species in a built environment. Experiments were performed at lab-scale with the Fire Propagation Apparatus (ASTM E2058) in order to study the effect of air vitiation on CO and soot yields. Results regarding the fuel burning rate are also presented. Both carbon dioxide and nitrogen were used as diluents in the inlet air flows. The oxygen concentration was decreased stepwise until the extinction point was reached. A first set of experiments was performed in well-ventilated fire conditions (equivalence ratio between 0.1 and 0.25). A second set of experiments was carried out in under-ventilated fire conditions (equivalence ratio equal to 1.1). A procedure is proposed for experimental data reduction. The results revealed useful for improving combustion sub-model predictions