Explore the vast range of titles available.

EDITORIALThis special issue is based on the papers selected for presentation during the 4th ESFSS (European Symposium on Fire Safety Science), held in Barcelona, Spain from October 9 to 11, 2024. Following the previous conference held in Nancy in 2018, the European Symposium on Fire Safety Science was the fourth edition in these series of symposia organized in Europe. The aim was to bring together researchers from Europe and beyond for exchanges and discussions on fire safety science.Approximately 200 contributions were received during the conference preparation, including submissions for both oral and poster presentations. Following a rigorous selection process involving at least 2 peer reviews of the full papers, 45 contributions were accepted for oral presentation and 99 for poster presentation, with 23 of the latter dedicated to work-in-progress.The conference was attended by 180 scientists from around the world, including countries such as Australia, Belgium, Canada, Chile, China, Czech Republic, Denmark, Finland, France, Germany, Hong Kong, India, Italy, Japan, Republic of Korea, Malaysia, New Zealand, Norway, Poland, Slovenia, South Africa, Spain, Sweden, Switzerland, the United Kingdom, Turkey, and the United States.This volume includes all the papers from the contributions presented during the seminar. They are organized into six main topics, in line with the conference program:• Material behaviour in fire (ignition, pyrolysis, flame spread, smouldering)• Fire dynamics, structures in fire (fire plumes, compartment fires, tunnel fires)• Wildland fires / Wildland-urban fires• Fire detection and suppression• Evacuation and human behaviour• Miscellaneous (e.g.: explosions and industrial fires, battery fires, solar panels, fire codes and standards)The conference organizers gratefully acknowledge the members of the scientific committee and the experts who reviewed the papers. They also extend their thanks to ACTIVA Congresos and the local organizing committee for their efforts in preparing the conference. The support from the IAFSS, the sponsors (SODECA; Kingspan. OFR Consultants, FM Global, Efectis and CSTB) the UPC research group CERTEC, and the Universitat Politècnica de Catalunya is also acknowledged.List of Syposium chairs, Organizing committee, Local organizing committee and Scientific committee are available in this pdf.

EDITORIAL This special issue is based on the papers selected for presentation during the 4 th ESFSS (European Symposium on Fire Safety Science), held in Barcelona, Spain from October 9 to 11, 2024. Following the previous conference held in Nancy in 2018, the European Symposium on Fire Safety Science was the fourth edition in these series of symposia organized in Europe. The aim was to bring together researchers from Europe and beyond for exchanges and discussions on fire safety science. Approximately 200 contributions were received during the conference preparation, including submissions for both oral and poster presentations. Following a rigorous selection process involving at least 2 peer reviews of the full papers, 45 contributions were accepted for oral presentation and 99 for poster presentation, with 23 of the latter dedicated to work-in-progress. The conference was attended by 180 scientists from around the world, including countries such as Australia, Belgium, Canada, Chile, China, Czech Republic, Denmark, Finland, France, Germany, Hong Kong, India, Italy, Japan, Republic of Korea, Malaysia, New Zealand, Norway, Poland, Slovenia, South Africa, Spain, Sweden, Switzerland, the United Kingdom, Turkey, and the United States. This volume includes all the papers from the contributions presented during the seminar. They are organized into six main topics, in line with the conference program: • Material behaviour in fire (ignition, pyrolysis, flame spread, smouldering) • Fire dynamics, structures in fire (fire plumes, compartment fires, tunnel fires) • Wildland fires / Wildland-urban fires • Fire detection and suppression • Evacuation and human behaviour • Miscellaneous (e.g.: explosions and industrial fires, battery fires, solar panels, fire codes and standards) The conference organizers gratefully acknowledge the members of the scientific committee and the experts who reviewed the papers. They also extend their thanks to ACTIVA Congresos and the local organizing committee for their efforts in preparing the conference. The support from the IAFSS, the sponsors (SODECA; Kingspan. OFR Consultants, FM Global, Efectis and CSTB) the UPC research group CERTEC, and the Universitat Politècnica de Catalunya is also acknowledged. List of Syposium chairs, Organizing committee, Local organizing committee and Scientific committee are available in this pdf.

Classical thermal theory of steady counterflow flame propagation is extended by allowing for the finite-rate of the heat release in the flame edge and by introducing the dependence of the flame edge temperature on the opposed flow velocity. The experimentally observed non-monotonic dependence of the flame spread rate on the velocity of opposed gas flow is replicated. The relation between the flame edge temperature and the opposed gas velocity is derived. Similar to the experimental observations, the proposed approach predicts existence of two extinction limits corresponding to flame quenching at low velocities (either due to insufficient reactant diffusion rate or excessive radiative losses) and blow-off at high velocities (due to the insufficient residence time).

Travelling fires (TFs) have been increasingly observed in large-scale fire events, prompting the development of analytical models to characterise their behaviour based on experimental studies and computational fluid dynamics (CFD) simulations. However, they are not commonly considered in a fire safety design process to date. This study describes a three-stage methodology to systematically do so, after reviewing the limitations of TF models. The first stage involves determining whether the scenario of a TF is more probable than that of a fully-developed fire, which would alter the predicted thermal exposure of the structure, and depends on a series of key parameters. These include geometric factors such as floor area, ceiling height, opening factor, and fuel load density within the compartment. In this study, these values are selected based on insights from existing literature. The second stage focuses on characterising the potential worst-case travelling fire (WCTF), which is influenced by the same parameters. The final stage would be to employ CFD models to more accurately assess fire behaviour. This paper addresses the first two stages of the design methodology, highlighting its contribution in discovering the WCTF with practical analytical methods for fire safety engineering.

The work described in this paper is undertaken with the purpose of providing a detailed assessment of the current modelling capabilities of the effects of fire suppression systems (e.g., sprinklers) in fire-driven flows. Such assessment will allow identifying key modelling issues and, ultimately, improving the reliability of the numerical tools in fire safety design studies. More specifically, we studied herein the heating and evaporation of a single water droplet. This rather 'simple' configuration represents the first step in a tedious and rigorous verification and validation process, as advocated in the MaCFP (Measurement and Computation of Fire Phenomena) working group (see https://iafss.org/macfp/). Such process starts ideally with single-physics 'unit tests' and then more elaborate benchmark cases and sub-systems, before addressing 'real-life' application tests. In this paper, we are considering the recently published comprehensive and well-documented experimental data of Volkov and Strizhak (Applied Thermal Engineering, 2017) where a single suspended water droplet of a diameter between 2.6 and 3.4 mm is heated up by a convective hot air flow with a velocity between 3 and 4.5 m/s and a temperature between 100 and 800°C. The high temperatures considered therein represent a strong element of novelty, since previous experimental studies on single droplets were limited to rather relatively 'moderate' temperatures, up to around 350°C. Furthermore, the monitoring of the time history of the droplet temperature field, in addition to the droplet lifetime, provides very useful information for model development and validation purposes. In this numerical study, 36 experimental tests have been simulated with the Fire Dynamics Simulator (FDS 6.6.0). The results show that the droplet lifetime is overpredicted with an overall accuracy of 31%. The accuracy in the range 300 to 800°C is even better, i.e., 7 %, whilst the cases of 200 and, more so 100°C, showed much stronger deviations. The measured droplet saturation temperatures did not exceed 70°C, even for high air temperatures of around 800°C, whereas the predicted values approached 100°C. Based on the current findings, further analysis is required on the modelling of the heat and mass transfer coefficients, and more specifically the sub-models for the Nusselt and Sherwood numbers.

The work described in this paper presents a comprehensive analysis of the convective heat and mass transfer coefficient modelling around a single water droplet using an in-house code. The most widely used approach is to rely on sub-models for the non-dimensional heat and mass transfer numbers (called hereafter the Nusselt, Nu, and the Sherwood, Sh, numbers) and which are shown to take the theoretical and functional form of Nu = 2 . 0 + K 2 Re d 1 / 2 Pr 1 / 3 and Sh = 2 . 0 + K 1 Re d 1 / 2 Sc 1 / 3 where Red is the droplet Reynolds number, Pr and Sc are the Prandtl and Schmidt numbers of the surrounding gas and K1 and K2 are constants. This formulation, which is generally referred to in the literature as the Ranz-Marshall model (with K1 = K2 = 0.6), is the most used approach in Computational Fluid Dynamics (CFD) codes for fire safety engineering. In this paper, we first assessed this formulation based on 36 experimental tests carried out in [Volkov and Strizhak, Applied Thermal Engineering (2017)] and where a single suspended water droplet of a diameter between 2.6 and 3.4 mm is heated up by a convective hot air flow with a velocity between 3 and 4.5 m/s and a temperature between 100 and 800°C. The results showed that the overall model uncertainty in the droplet lifetime prediction is about 34% with particularly poor results when the air temperature is 100 or 200°C. The droplet saturation temperatures were overestimated by around 20 to 30°C. After this initial assessment, we performed a sensitivity analysis and selected a combination of values for K1 and K2 that provided an overall simultaneous good agreement for both the droplet lifetimes (model uncertainty of 5%) and the droplet saturation temperatures (around 10°C). This analysis showed that, for high air temperatures (i.e., Ta ≥ 300°C), the value of K2 = 0.6 remains suitable. However, for these cases, the value of K1 needed to be increased (to 1.8 and up to 4) in order to promote the evaporation-induced cooling and improve the predictions in terms of droplet saturation temperatures. For Ta = 100°C, the 'best' combination was found to be K1 = K2 = 1.8. Such combination allowed to reduce the initially overestimated droplet lifetimes by promoting mass transfer (through an increased value of K1) without slowing down the heating process that generates water vapor at the droplet surface (explaining the equally increased value of K2). The case of Ta = 200°C appeared to be an intermediate case. The present results indicate that the 'classical' Ranz-Marshall approach with K1 = K2 = 0.6 is not optimal. A more thorough analysis, with eventually additional experimental data, is required.

Large eddy simulations of flame extinction with N2 as extinguish agent are performed focusing on combustion and radiation modelling with infinitely fast chemistry. The use of a EDC combustion model with dynamically determined coefficients, an enthalpy-based flame extinction model based on a locally variable critical flame temperature and the use of the WSGGM for radiation are employed in order to predict flame extinction in a turbulent CH4 line burner. The numerical predictions of mean temperatures, combustion efficiencies and radiative fractions with different grid sizes are compared to the experiments by White et al. (2015). Overall, the results from the numerical simulations agree well qualitatively and, to some extent, quantitatively with the experimental data when small grid sizes are employed. More specifically, the maximum values and the profile widths of the mean temperatures at two axial locations examined are reasonably well predicted. The decrease in the combustion efficiencies as the extinction limit is approached is reproduced by the numerical simulations. The decreasing trend in the radiative fractions as the oxidizer stream is diluted with N2 is also captured by the simulations using a WSGGM model for radiation with a dynamically determined beam length which is calculated based on the local heat release rate. Nevertheless, the resulting radiative fractions are still over-predicted as the extinction limit is approached. Limitations of some of the typically used approaches regarding radiation modelling in flame extinction scenarios are outlined. Additionally, possible deficiencies on the use of a fixed critical flame temperature and/or re-ignition temperature in the flame extinction/re-ignition modelling are discussed and possible extensions of the modelling approaches are presented.

The total wall time is often difficult to predict a priori in compartment fire simulations due to dynamic phenomena that can occur, e.g., flame extinction. The wall time is dependent on multiple physical factors in the simulation, along with simulation factors and the system used to compute the model. Specifically, the CFL number of a simulation is highly influential to the wall time, as this restricts the time step size. In this paper, the prediction of the total wall time for a single-compartment fire is investigated considering varying fire heat release rates and compartment ventilation factors. It is shown that an increasing heat release rate increases the total wall time due to higher velocities inside the compartment. Furthermore, when the compartment becomes under-ventilated, the wall time becomes more difficult to predict early on in the simulation, as steady state conditions are reached later, compared to well-ventilated cases. The time at which the wall time can be accurately predicted changed from a few physical seconds in the well-ventilated case, to up to 60 physical seconds for the under-ventilated case.

Buoyant fires with gaseous fuel are discussed in the context of a closed, mechanically ventilated enclosure. Focus is on the ventilation flow rates (admission and extraction) and on the effect of leakages. The impact of the combustion is discussed. Multiple definitions of the global equivalence ratio (GER) are considered and the consequences therefore on the combustion regime is quantified. In the experimental campaign, these regimes varied from steady well-ventilated combustion to rapid extinction. These new results shed light on the fire scenario in a closed, mechanically ventilated enclosure and identify the most complex and critical configurations in terms of risk assessment.

The objective of this work is to provide a ‘support tool’ to assess the burning rate of a pool fire in a well-confined and mechanically-ventilated room using a single-zone model based on conservation equations for mass, energy and oxygen concentration. Such configurations are particularly relevant for nuclear facilities where compartments are generally sealed from one another and connected through a ventilation network. The burning rates are substantially affected by the dynamic interaction between the fuel mass loss rate and the rate of air supplied by mechanical ventilation. The fuel mass loss rate is controlled by (i) the amount of oxygen available in the room (i.e. vitiation oxygen effect) and (ii) the thermal enhancement via radiative feedback from the hot gas to the fuel surface. The steady-state burning rate is determined by the ‘interplay’ and balance between the limiting effect of oxygen vitiation and the enhancing effect of radiative feedback. An extensive sensitivity study over a wide range of fuel areas and mechanical ventilation rates shows that a maximum burning rate may be obtained. For the studied HTP (Hydrogenated Tetra-Propylene) pool fires, the maximum burning rate is up to 1.75 times the burning rate in open air conditions.