Compartment fire is conducted by complex phenomena which have been the topics of many studies. During fire incident in a building, damage to occupants is not often due to the direct exposition to flames but to hot and toxic gases resulting from combustion between combustibles and surrounding air. Heat is therefore taken far from the source by combustion products which could involve a rapid spread of fire in the entire building. With the intention of studying the impact of the opening size on the behaviour of fire, experimental and computational studies have been undertaken in a reduced scale room including a single open door. Owing to Froude modelling, the obtained results have been transposed into full scale results. In accordance with experiments, numerical studies enabled the investigation of the influence of the ventilation factor on velocities of incoming air and outgoing burned gases and on areas of the surfaces crossed by these fluids during full-developed fire. Comparison of the deduced mass flow rates with the literature reveals an approval agreement.
Many experiments have been done by authors to study the influence of the natural ventilation through openings on fire behaviour in compartments. It has been revealed that fire will be influenced by the size of existing openings which can be an open window, an open door, or both of them. Concerning the last case, the literature does not give any information about the impact of the arrangement of these openings on the behaviour of fire. The present paper aims then to carry out a comparative study of the disposition of the window compared to the door, on the behaviour of fire in a compartment. To achieve that objective, fire experiments were conducted in a reduced scale room of dimensions 1.20 m × 1.20 m × 1.02 m, which can be modulated into two configurations. The first one named “PFC configuration” is the case where the open door and the open window are in nonopposite walls. The second one named “PFO configuration” is the case where these both openings are in opposite walls. After having performed several fire tests in both configurations using the same amount of diesel fuel as fire source, results revealed that the fuel burns faster in the PFC configuration compared to that in the PFO configuration. This is due to a global mass loss rate of 2.93 × 10−4kg.s−1 against 2.62 × 10−4kg.s−1, respectively. Beyond a difference of 20°C observed on the maximal temperature of burned gases located at ceiling, results also revealed the production of ghosting flames in the PFO configuration.
Backdraft is a complex phenomenon which occurs during cases of confined fires. It appears by a fast deflagration which occurs after the introduction of oxygen into a compartment filled with hot gases rich in unburned combustible vapor. Practically, this situation could occur at the time of intervention of firemen who break the door or when a window breaks under the action of thermal stresses. Based on a strong experimental campaign, the present paper aimed to make a quantitative investigation of the effect of confining on a totally closed fire. With this focus, fire tests were carried out in a completely closed room of dimensions 1.20 m × 1.20 m × 1.02 m, with five sources of fire of different heat release rates. The same fire sources were also tested in a free atmosphere in order to get reference data. After a statistical study of data, a comparative analysis between both results has been done. Its outcome is that confining has a major impact on the quality of combustion and on the fire duration. More precisely, it has been noticed comparatively to fire tests in free atmosphere that confining increases the fire duration by 14.85 percent while it decreases the heat release rate by 21.72 percent.
According to the geometry of compartments, quantities of smokes released during fire tend to accumulate at ceiling so as to form a cloud of hot gases. Heat transfer between these hot gases and walls is decisive for the development of fire. An increase in temperature of these gases could lead to dangerous phenomena such as flashovers and backdrafts. Owing to experiments and numerical simulation, the objective of the present paper is to investigate on the influence of natural ventilation on convective heat transfer between hot gases and walls of a room in fire. So, varying the ventilation level, it was firstly about to carry out fire tests in an experimental room. Secondly, study was focused on the numerical simulation of these tests so as to estimate velocity field of burnt gases near walls during fire. Validation of numerical results has been done by confronting simulated results to experimental results. A full-scale extrapolation of results enabled revealing that while the ventilation level in the room changes, the amplitude of convective heat transfer changes according to the regime of fire. It was shown that for the fuel-controlled fire, the convective heat transfer coefficient strongly increases with the ventilation factor, and for the ventilation-controlled fire, convective heat transfer coefficient weakly decreases with the ventilation factor and remains nevertheless close to value 8.75 W ⋅ m − 2 ⋅ K − 1 .
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