Showing papers in "Fire Safety Science in 2003"
TL;DR: In this paper, the thermal environment in small and moderate-scale pool flames is studied by large eddy simulation and the Finite Volume Method for radiative transport, and the spectral dependence of the local absorption coefficient is represented using a simple wide band model.
Abstract: The thermal environment in small and moderate-scale pool flames is studied by Large Eddy Simulation and the Finite Volume Method for radiative transport. The spectral dependence of the local absorption coefficient is represented using a simple wide band model. The predicted radiative heat fluxes from methane/natural gas flames as well as methanol pool burning rates and flame temperatures are compared with measurements. The model can qualitatively predict the pool size dependence of the burning rate, but the accuracy of the radiation predictions is strongly affected by even small errors in prediction of the gas phase temperature.
86 citations
TL;DR: GridFlow has been developed to represent individual occupants in building spaces on a grid network, moving to exits through escape routes using an x,y coordinate and distance map method, and is considered to be as informative as the most sophisticated models, using simple, transparent and easily verifiable behavioural inputs.
Abstract: Methods for estimating the time required for building evacuations range from simple calculations to highly complex computer-based models. Some of these more complex models attempt to represent the pre-movement behaviour of occupants, as well as their movement behaviours and physical movement characteristics, often using detailed rule-based algorithms, or artificial intelligence techniques. The quantification of such behaviours can be obscure and the models complex to use. Other models may ignore pre-movement behaviours. GridFlow has been developed to represent individual occupants in building spaces on a grid network, moving to exits through escape routes using an x,y coordinate and distance map method. Walking speeds, effects of crowding, obstacle avoidance, merging flows and flows through restrictions such as corridors, stairs and doorways are represented. Physical movement methods are therefore similar to those used in other models such as Crisp, Exodus, Simulex and others. GridFlow differs from other models in that premovement time and pre-movement-travel interactions are considered central to evacuation time modelling. In GridFlow, the pre-movement time is handled in the form of distributions obtained by direct measurements during monitored evacuations. The model therefore encompasses crucial elements of the evacuation process, without requiring detailed behavioural simulations. This is considered to be as informative as the most sophisticated models, using simple, transparent and easily verifiable behavioural inputs, derived from empirical data or specified and justified by the user.
66 citations
TL;DR: In this paper, improvements have been made to the combustion and radiation routines of a large eddy simulation fire model maintained by the National Institute of Standards and Technology (NIST), and some approximations were made within the new algorithms.
Abstract: Improvements have been made to the combustion and radiation routines of a large eddy simulation fire model maintained by the National Institute of Standards and Technology. The combustion is based on a single transport equation for the mixture fraction with state relations that reflect the basic stoichiometry of the reaction. The radiation transport equation is solved using the Finite Volume Method, usually with the gray gas assumption for large scale simulations for which soot is the dominant emitter and absorber. To make the model work for practical fire protection engineering problems, some approximations were made within the new algorithms. These approximations will be discussed and sample calculations presented.
65 citations
TL;DR: In this article, the effects of cross-winds on apparent flame heights and tilt angles were investigated with a single fire source and three sets of propane burners as model fire sources, one was a small circular burner, the other two were large square burners, and the other was rectangular burners with aspect ratio ranging from 1 to 6.
Abstract: Experiments with a single fire source were carried out in an unconfined space to characterise the effects of cross-winds on apparent flame heights and flame tilt angles. Three sets of propane burners were used as model fire sources. One was a small circular burner, the other was large square burners, and the other was rectangular burners, having the aspect ratio ranging from 1 to 6. A refined empirical model on the apparent flame heights of the inclined flames modified by heat release rate and aspect ratio of fire source was presented. We also developed an empirical model of the flame tilt angles based on the balance of mass between the fluxes given by the upward hot current and the cross-winds. These models are correlations with respect to dimensionless heat release rates, Froude numbers and aspect ratios of fire sources. The values of empirical coefficients and exponents of the correlations were derived from the experimental results.
53 citations
TL;DR: In this paper, the authors proposed to apply pre-movement time distributions measured from monitored evacuations, fire incidents, or derived using behavioral models, and specified in terms of a number of "design behavioural scenarios" analogous to design fire scenarios, classified according to the key features listed.
Abstract: Performance-based life-safety design depends on a comparison between the time required for escape (Required Safe Escape Time – RSET) and the time to loss of tenability (Available Safe Escape Time ASET). Both include a number of stages, involving a variety of processes and requiring a range of input data. A problem for the design engineer is that while all stages need to be addressed to obtain a realistic outcome for the analysis, some aspects are reasonably well understood and quantified, while others are often oversimplified or ignored. For the RSET time line, most emphasis is usually placed upon the travel time component, representing the physical movement of occupants into and through the escape routes. However, the time required for occupants to engage in a range of behaviours before the travel phase (pre-movement time), often represents a greater component of the total escape time. Pre-movement time distributions are dependent upon key features such as occupancy type, warnings, occupant characteristics, building complexity and fire safety management strategy. It is proposed that a practical solution for the engineer is to apply pre-movement time distributions measured from monitored evacuations, fire incidents, or derived using behavioral models, and specified in terms of a number of “design behavioural scenarios” analogous to “design fire scenarios”, classified according to the key features listed. A problem with the evaluation of travel time, is that most calculation methods assume no interaction between the occupants and the fire effluent. If occupants are exposed to irritant smoke, then movement speeds are likely to be reduced. A calculation method is proposed, relating predicted travel speed to smoke and irritant concentrations. The ASET time line ends when occupant incapacitation is predicted from exposure to fire effluent. This depends upon the time-concentration curves for the main toxic fire effluents, requiring inputs on smoke and toxic product yields under different fire conditions. Existing engineering calculations use only smoke density and/or carbon monoxide, with yields often treated as constants, usually for the well-ventilated fire case. A method is proposed, whereby yield data for major toxic effluent species can be obtained over a range of fire conditions, expressed in relation to the global equivalence ratio. Results are illustrated for carbon monoxide and hydrogen cyanide.
52 citations
TL;DR: In this article, an experimental program was intended to analyse the heat feedback from a spreading wall fire to its unburned surface, one of the two important parameters determining its spread rate.
Abstract: An experimental programme was intended to analyse the heat feedback from a spreading wall fire to its unburned surface, one of the two important parameters determining its spread rate. The heat flux from PMMA fires was observed to be higher than those from previous investigations as plotted with normalised flame height (X/Xf). However, very good consistency was performed with another study as a parameter " wo q& is introduced with heat flux plotted in another normalisation. The averaged heat flux, an important parameter used in upward flame spread modelling, was discussed and suggested to be around 15–20 kW/m. This is much lower than the commonly accepted 25-30 kW/m.
47 citations
TL;DR: In this paper, a prototype of a seismic-induced fire risk assessment method was developed to evaluate fire risk based on factors such as size and type of buildings, installed fire protection systems, and the intensity of input earthquake motion.
Abstract: Post-earthquake fire risk can be different from other design scenarios because fire protection systems can be non-functional even when a building itself is structurally sound. We have developed a prototype of a seismic-induced fire risk assessment method to evaluate fire risk based on factors such as size and type of buildings, installed fire protection systems, and the intensity of input earthquake motion. This paper describes the outline of the framework and examples of results from a case study applying a tentative simplified model. Results from our study show that sprinkler systems that are designed to be seismically resistant have a significant effect in mitigating fire risk associated with earthquakes.
43 citations
TL;DR: In this paper, a physically-based model for simulating urban fire spread is proposed. But the model is based on single zone method, applying control volumes to compartments in a building.
Abstract: An attempt is made to develop a physically-based model for simulating urban fire spread. In the model, urban fire is regarded as an ensemble of multiple building fires. The model consists of two sub-models, i.e. the model to predict the building fire behavior under the exposure of heating from other building fires and the model to predict the thermal environment caused by building fires. The building fire model is based on single zone method, applying control volumes to compartments in a building. When the external heating, whether it is from the same building or from other buildings, exceeds the critical heat flux, the fire load in the compartment ignites and burns. For the thermal environment model, thermal radiation and fire-induced plume are considered as the factors of building-to-building fire spread. The model is applied to a fictitious urban district where 49 multi-room buildings are arrayed in a simple configuration.
39 citations
TL;DR: In this paper, a multi-layer zone fire model for a single compartment was developed to predict the vertical distributions of the temperature and the gas concentrations, in which the volume of a fire room was divided into an arbitrary number of horizontal layers, and the mass and enthalpy flow rates through the layer interfaces and the opening and the heat transfer rates for each layer were derived.
Abstract: A multi-layer zone fire model for a single compartment was developed to predict the vertical distributions of the temperature and the gas concentrations. The basic concept of this model is to divide the fire room volume into an arbitrary number of horizontal layers, in which the temperature and other physical properties are assumed to be uniform. Considering the mass and the enthalpy flow rates through the layer interfaces and the opening and the heat transfer rates for each layer, the zone equations for the temperature and the species mass fractions are derived. The results of the sample calculations are compared with the experiments conducted by Steckler et al. From the comparison, it is considered that the model can be a practical tool to predict the behavior of fire in a room, although continuing effort may be necessary to improve the prediction.
32 citations
TL;DR: In this paper, the differential mass scattering cross section (m·g·sr) of various non-flaming and flaming fire generated smoke aerosols as well as nuisance aerosols created in the Fire Emulator/Detector Evaluator is presented.
Abstract: This paper presents the differential mass scattering cross section [m·g·sr] of various non-flaming and flaming fire generated smoke aerosols as well as nuisance aerosols created in the Fire Emulator/Detector Evaluator. These measurements have been determined for two linear polarizations and the scattering angle range of 5° to 135° at a wavelength of 632.8 nm. Small diameter particles have been separated from large particles using the forward scattering information. Discrimination of soot generated by flaming fuels from both smoke aerosols generated by non-flaming fires and nuisance aerosols is demonstrated by the ratio of forward (45°) to backward scattering (135°), the polarization ratio, and dependence on scattering parameter, ( ) 2 sin 4 1 θ πλ− = q .
32 citations
TL;DR: In this article, a series of salt water experiments that resemble the smoke flow in the early stages of a residential scale building fire were performed using the Laser Induced dye Fluorescence (LIF) technique.
Abstract: This paper summarises a series of salt water experiments that resemble the smoke flow in the early stages of a residential scale building fire. Experimental measurements of the fluid density of the salt water flow field are made using the Laser Induced dye Fluorescence (LIF) technique. The salt water experiments are then simulated using the Large Eddy Simulation (LES) and Direct Numerical Simulation (DNS) computational techniques that are available within the Fire Dynamics Simulator (FDS) computer fire model. Computations, using each technique, are conducted at a number of different grid resolutions. The comparison of computational results and experimental measurements show that the LES technique performs better at coarse grid resolutions, due primarily to the computational stability requirement for an artificially high fluid viscosity in DNS, which inhibits turbulent mixing. The LES computations were capable of resolving the flow field features that are evident in the experimental density measurements when the uniform grid resolution has a characteristic dimension that is less than the vertical extent of the domain divided by fifty. Generally speaking, at high grid resolutions, the agreement between experimental measurements and the LES computational results were very good.
TL;DR: In this paper, a distributed fiber optic Brillouin scattering investigation is presented, which involves measuring the intensity versus time for real-time temperature measurements, which can be applied in practical fire detection schemes through the use of a threshold temperature that corresponds to the maximum intensity.
Abstract: This paper presents a distributed fiber optic Brillouin scattering investigation, which involves measuring the Brillouin intensity versus time for real-time temperature measurements. This can be applied in practical fire detection schemes through the use of a threshold temperature that corresponds to the maximum Brillouin intensity. In the experiments, a 11 km fiber length was interrogated by 20 ns pulses (2 m spatial resolution) to monitor the temperature variations in a 10 m fiber region. The corresponding theory has confirmed the suitability of real-time intensity monitoring for temperature measurement.
TL;DR: In this paper, a model for the local configuration factor for the radiant interchange between the internal surface of the cone heater and the specimen's surface in the cone calorimeter was developed.
Abstract: A model has been developed for the local configuration factor for the radiant interchange between the internal surface of the cone heater and the specimen's surface in the cone calorimeter. The incident heat flux under the cone was characterised in a series of experiments as a function of spatial coordinates. Both the emissivity and the temperature of the heating element were estimated from the experimental data. Significant variations in the surface temperature, and therefore in radiosity, were observed. The expression for the configuration factor was applied to estimate uncertainties in the measured variables due to tolerances in independent parameters. Plots were provided of the configuration factor and isolines of the radiant heat flux at various heights below the base of the cone. A comparison was carried out between predicted and measured data, demonstrating good agreement. The model predicted that, at the standard location of the specimen of 25 mm below the frustum, the radiant flux is uniform but only within the central area of the sample. Toward the edges and corners, the flux decreases by 2.6 and 15.9%, respectively, in comparison to that along the centreline.
TL;DR: In this article, the authors investigated the effect of water application on the time to ignition and the heat release rate of a Group A Plastic Commodity (GAP) fire.
Abstract: The objective of this work was to provide measurements from reduced-scale experiments for use in the NIST Fire Dynamics Simulator, a computational fluid dynamics model that calculates fire growth, spread, sprinkler activation, and water suppression of rack-storage commodity fires The model requires implementable sub-grid algorithms and corresponding data that adequately represent the full-scale heat and mass transfer that occurs in a warehouse fire with rack-storage of a standard commodity This paper describes experiments that investigated the effect of water application on the time to ignition and the heat release rate of the Group A Plastic Commodity Several types of experiments were conducted including small-scale ignition measurements using the LIFT device and the cone calorimeter, and moderate-scale heat release rate measurements using oxygen consumption calorimetry Both ignition and heat release rate measurements were made with and without water application The results showed that the heat release rate is adequately described as a function of the water application rate in a form suitable for implementation in a CFD fire model
TL;DR: In this article, the authors derived the data for the ignition frequency of structural fires from statistics for different building categories in Finland and found that the power law function of the total floor area was at variance with the data, but working heuristically, it was found that a sum of two power functions led to a fairly good fit with the available statistical data.
Abstract: In this study the data for the ignition frequency of structural fires was derived from statistics for different building categories in Finland. Following a model obtained from literature, the power law function of the total floor area was observed to be at variance with the data, but working heuristically, it was found that a sum of two power functions led to a fairly good fit with the available statistical data. Since theoretically power law dependence is a special case, a generalized theoretical model was proposed, starting from the initial distributions of the buildings involved in fires and the total stock at risk. Good agreement with the observations was obtained using this ansatz. The general method shed new light on ignition frequency, and good theoretical explanation was achieved for the observed phenomena. It showed that ignition frequency varied with the floor area, and has maxima and minima depending on the form of these size distributions. Estimation of systematic errors yielded values of partial safety constants needed for the calculation of the ignition frequency for design purposes. The model is useful for determining the ignition frequency of buildings with a floor area of between 100 and 20 000 m.
TL;DR: In this paper, the use of smoke optical densities outside a detector as criteria for predicting smoke detector responses was evaluated and results were presented for optical density alarm thresholds corresponding to when 20, 50 and 80 percent of the detectors had alarmed in full-scale tests.
Abstract: Models have been used to estimate smoke detector alarm times by calculating smoke optical densities resulting from fires and correlating the smoke value to an alarm threshold of the detector. This work evaluated the use of smoke optical densities outside a detector as criteria for predicting smoke detector responses. Results are presented for optical density alarm thresholds corresponding to when 20, 50 and 80 percent of the detectors had alarmed in full-scale tests. The data showed that there was a large amount of variability in the measured smoke optical density values outside a detector at the time of alarm. Major variables evaluated included detector type, fire type and nominal detector sensitivity. This evaluation also examined experimental smoke optical density data at the time of detector alarms and compared these smoke values to alarm thresholds recommended in the literature.
TL;DR: In this paper, a series of fire experiments in a 0.9m by 0.4m high compartment with a single rectangular opening for the ventilation with opening factors (AH 0.5 ) ranging from 0.02 m5/2 to 0.10 m5 /2.
Abstract: This paper describes a series of fire experiments in a 0.9m by 0.6m by 0.4m high compartment. A single rectangular opening is set for the ventilation with opening factors (AH0.5 ) ranging from 0.02 m5/2 to 0.10 m5/2. Propane gas and three kinds of solid fuel (wood crib, PMMA and polyurethane flexible foam) are used as fuels. Mass loss rates are measured and net heat release rates are estimated with a furniture calorimeter to examine combustion efficiency, which effects ejected flame formation. Results indicate that the combustion efficiency of gas fuel depends on ‘fuel to air’ global equivalence ratios (Φ ) and the efficiency starts to decrease at about the 0.75 of Φ. Moreover, the efficiency reaches 77 % when Φ is at 1.27. However, when more fuel is supplied, the efficiency is improved to 100 % at the 2.0 point, because combustion is promoted within externally ejected flames. In the case of solid fuels, maximum heat release rates become 1.5 to 2.5 times higher than the suppositional maximum heat release rate determined by the opening factor. Under these cases, flames are ejected longer and the efficiency of the combustion also recovers as well as gas fuel combustion.
TL;DR: In this article, the authors compare the results of two separate analysis methods, one relatively simple and one relative complex, to provide an estimate of the impact of missing fire protection material on the temperature rise experienced by a steel column exposed to the conditions associated with the ASTM E119 standard test.
Abstract: The loss of fire protection material is generally acknowledged to reduce the fire resistance of protected steel structural members, but the magnitude of the reduction is unknown. Two analyses are applied to assess the heat transfer to a steel column and investigate the proportional decrease in the fire resistance when relatively minor portions of spray-applied fire protection material are removed. One method is an elementary, lumped heat capacity analysis (LHC). The second method involves the application of a three-dimensional, finite element model. In both cases, the column is assumed to be subjected to the standard ASTM E119 fire resistance test. The predicted temperature distributions within the member over time are used in conjunction with the thermal endpoint criteria specified in ASTM E119. The LHC analysis of the temperature rise of the entire column shows the area of missing protection to be of little consequence in determining the average temperature of the entire column. The column temperatures calculated using the LHC approach are primarily dependent on the original fire resistance of the column for the small areas of missing protection examined. In contrast, the area of the missing protection and the size of the column are found to have an appreciable effect upon the thermal response of the column regardless of the protection thickness using the finite element analysis. Introduction ASTM E119 documents the standard test to assess the fire resistance of structural members in North America [1]. The temperature endpoint criteria for steel columns are: an average temperature of 538°C and 649 °C at a single point [1]. One method of protecting steel columns is through the use of an insulating, spray-applied fire protection material. Several such materials are identified as part of listed steel column assembly designs included in the Fire Resistance Directory [2]. The intent of this study is to compare the results from two separate analysis methods, one relatively simple and one relative complex, to provide an estimate of the impact of missing fire protection material on the temperature rise experienced by a steel column exposed to the conditions associated with the ASTM E119 standard test. One method, referred to as the LHC analysis, uses an algebraic equation that is reiterated to determine the temperature rise of the column [3]. The second analysis method uses a finite element model, FIRES-T3, to conduct the analysis [4]. Assessing the impact of the local temperature rise on the structural performance of the column is beyond the scope of this paper. However, such is needed to conduct a more comprehensive analysis of the impact of the missing protection, rather than applying the endpoint temperature criteria from ASTM E119. 1 Copyright © International Association for Fire Safety Science
TL;DR: A probabilistic risk assessment method is described in this paper for the analysis of expected risk to life of building occupant evacuation process and the attainment of untenable conditions due to fires in buildings.
Abstract: A probabilistic risk assessment method is described in this paper for the analysis of expected risk to life. The method involves stochastic, as well as deterministic, modelling of building occupant evacuation process and the attainment of untenable conditions due to fires in buildings. Both the number of occupants leaving a building at a given time and the time to untenable conditions are treated as random variables. A general expression for calculating the expected number of death is given. With the postulated Poisson distribution for the number of occupants leaving a building and uniform distribution for the time to untenability, a simple expression for the calculation of the expected number of deaths is obtained. An example is given to illustrate the application of the method.
TL;DR: In this paper, the authors used the Fire Dynamics Simulator (FDS) to simulate the fire and smoke behavior of the twin towers of the World Trade Center (WTC) on September 11, 2001.
Abstract: Based on preliminary assumptions and analysis, mathematical models have been used to estimate the behavior of the fires in the twin towers of the World Trade Center (WTC) on September 11, 2001. The hijacked-plane collision with each tower produced significant structural damage, generated a spectacular external fireball, and started burning within the tower. The fuel consumed by the fireball was lost as an ignition source, but produced a pressure pulse that broke windows and changed the ventilation for the fires. The subsequent fire in each tower generated a quasi-steady, wind-blown smoke plume. The fire and smoke behavior were simulated using the Fire Dynamics Simulator (FDS). Comparison of the observed plume trajectory with the simulated one allowed us to estimate that the rate of energy supplied by the fire to the plume was of the order of magnitude of a gigawatt (GW). The rate of energy supplied to the plume, plus the energy-loss rate, determine the total heat release rate (HRR), the most important single parameter for each tower fire. Two bounding scenarios for the interior damage and fuel distributions were assumed for the north tower. For each scenario, the simulated visible fire and smoke behavior outside the tower were compared with the photographic and video records to determine which scenario seemed more appropriate. The simulations for the two scenarios also provided estimates of the likely thermal environment within each tower.
TL;DR: In this paper, heat flux and temperature measurements were conducted on a square steel column adjacent to and surrounded by fire sources from the interest in the application to the structural fire safety design of metal structures.
Abstract: Heat flux and temperature measurements were conducted on a square steel column adjacent to and surrounded by fire sources from the interest in the application to the structural fire safety design of metal structures. The tests on the adjacent fires demonstrate a description of the heat flux profile along the column surface as a single function of the height normalized by flame height for each column-fire distance and notable decrease of surface heat flux by the increase of the column-source distance. Surface temperature of the column in this configuration was found to be notably lower than the estimate from heat flux data based on the uniform heating assumption, which suggests the significance of the conductive heat loss to unheated surfaces of the column. The tests on the surrounding fires has resulted in heat flux profile weakly dependent on heat release rate and coincidence of the measured surface temperature and its estimate from heat flux due to rather even heat flux on all surfaces of the column.
TL;DR: In this paper, a fire growth model was developed to predict material performance in the ISO 9705 test using small-scale test data from ASTM E1354 cone calorimeter.
Abstract: The flammability of interior finish materials for many applications is regulated using the ISO 9705 large-scale room corner fire test. To aid designers in developing new materials, a fire growth model has been developed to predict material performance in the ISO 9705 test using small-scale test data from ASTM E1354 cone calorimeter. The fire growth model includes a flame spread model linked with a two zone compartment fire model, CFAST Version 3.1.2. At a user selected time interval, the flame spread model uses the gas temperature from CFAST to predict the heat release rate of the fire at that time interval, and then provides CFAST with a new heat release rate to predict conditions during the next time step. The flame spread model is an improved version of the flat wall flame spread model previously developed for the U.S. Navy. The model is capable of predicting flame spread in a variety of configurations including a flat wall, a corner with a ceiling, flat wall with a ceiling, unconfined ceiling, and parallel walls. The fire growth model was used to predict the heat release rate and smoke production rate measured in eight ISO 9705 room corner fire tests on composite materials used in marine applications.
TL;DR: In this paper, the authors present data relating to occupant pre-evacuation times from a university and a hospital outpatient facility, showing that over 50% of evacuees were less dependent upon the actions of the staff with no prior prompting.
Abstract: This paper presents data relating to occupant pre-evacuation times from a university and a hospital outpatient facility. Although the two structures are entirely different they do employ relatively similar procedures: members of staff sweeping areas of the structure to encourage individuals to evacuate. However, the manner in which the dependent population reacts to these procedures is quite different. In the hospital case the patients only evacuated once a member of the nursing staff had instructed them to do so while in the university evacuation the students were less dependent upon the actions of the staff with over 50% of them evacuating with no prior prompting. Although this data may be useful in a variety of areas, it was collected primarily for use within evacuation models.
TL;DR: In this article, a simple kinetic description is developed based on the experimental results and integral analysis method to determine the mass loss kinetics of the thermal decomposition with linear temperature programming in air atmosphere.
Abstract: The wood and leaf samples of eight species are examined by non-isothermal means to determine the mass loss kinetics of the thermal decomposition with linear temperature programming in air atmosphere. A simple kinetic description is developed based on the experimental results and integral analysis method. In the model, the mass loss process consists of three steps. The first step corresponds to the water evaporation, and the subsequent two mass loss steps are mainly due to two major pseudo components. The two pseudo components decompose respectively at two separate temperature regions. Under this kinetic scheme, the kinetic compensation effect is analyzed and it is found that the kinetic parameters E and A resulted from the variation of the species and the variation of model functions exhibit kinetic compensation effect. Quantitative and statistical criterion to distinguish between real and false compensation effect is discussed in detail.
TL;DR: In this article, a flammability area of a CO/F2/N2 mixture was determined experimentally, and designated in a triangular diagram, and a SiH4/CF3OF/N 2 mixture was also determined and designated.
Abstract: Recently, a variety of gases have been used in advanced technological industries, such as a semiconductor industry. There are several highly reactive gases among them. Fluorine is one of the representative gases which have very high reactivity. Its high reactivity has been known qualitatively for a long time. But its quantitative hazard has not been assessed yet. In this study, a flammability area of a CO/F2/N2 mixture was determined experimentally, and designated in a triangular diagram. And, a flammability area of a SiH4/CF3OF/N2 mixture was also determined and designated in a triangular diagram. CF3OF is a product of a reaction between CO and F2, which are components of the first mixture, and used as an etching or a cleaning gas in a semiconductor industry. Namely, there is a possibility of accidental mixing between SiH4 and CF3OF. SiH4 is a material of silicon based semiconductors. The flammability diagrams obtained in this study are indispensable for safe handling of these gases.
Journal Article•
TL;DR: Wang et al. as mentioned in this paper calculated the consumed biomass due to forest fires according to the statistics of forest fires from 1991 to 2000 and research results of Chinese forest biomass, which indicated that the products of biomass burning affect the atmosphere in short and long term.
Abstract: Many studies indicated that the products of biomass burning affect the atmosphere in short and long term. Vegetation burning can produce some gases, which have significant affections on environment, including some greenhouse gases, such as CO2 and CH4 etc. Smoke aerosols produced from biomass burning also change global climate and atmospheric chemistry. The paper calculates the consumed biomass due to forest fires according to the statistics of forest fires from 1991 to 2000 and research results of Chinese forest biomass. During the study period, forest fires burned average 5～7Tg biomass each year and directly emitted carbon 20.24～28.56 Tg, CO2 74.2～104.7 Tg, CH4 1.797～2.536 Tg,smoke aerosols 0.999～1.410 Tg. In 19912000, average emission of carbon dioxide accounts for 2.7～3.9% of the total emission of China (using the data of 2000), CH4 3.3～4.7%.
TL;DR: In this paper, the authors established a similarity relationship controlling the buoyant turbulent boundary layer combustion of wall fires, which is suitable for development of analytical and CFD models of turbulent wall fires.
Abstract: The study establishes a similarity relationship controlling the buoyant turbulent boundary layer combustion of wall fires. Measurements of soot deposition onto glass rods allow one to infer the characteristic thickness, S δ , of propylene flames at different heights, z , and mass transfer rates, m ′ ′ & . The normalized flame thickness, z S δ , is successfully correlated by the overall fuel to air mass ratio of the flames, Ψ . Similarly, Ψ , correlates the measured boundary layer temperature profiles of the flames normal to the wall. It correlates measurements of the outward directed radiance, r N from the same propylene wall fires with a uniform effective flame radiation temperature, f T , and uniform soot absorption/emission coefficient being independent of both height, z , and fuel mass transfer rate, m ′ ′ & . Finally the same fuel to air ratio, Ψ , correlates, here for the first time, the LDV velocity measurements of Most et al for turbulent ethane wall flames performed at Factory Mutual Research in 1982. The data presented here are suitable for development of analytical and CFD models of turbulent wall fires.
TL;DR: In this paper, the optimal design parameters of water-based protection systems against large industrial oil cooker fires were evaluated using 14 full-scale fire tests and the results showed that the systems using the nominal 6.4 mm orifice spray nozzles placed in a double-row 0.76 m above the oil surface, discharging a 20 mm/min density, yielded the best performance.
Abstract: Fourteen full-scale fire tests were conducted to determine the optimal design parameters of water-based protection systems against large industrial oil cooker fires. All but one test fires were self-ignited by heating the oil inside a test pan above its auto-ignition temperature. Three test mock-ups that simulated industrial oil cookers were fabricated for the tests: 3.0 m long by 2.4 m wide, 6.1 m long by 2.4 m wide, and 12.2 m long by 2.4 m wide. Three types of water spray systems utilizing 13 mm orifice sprinklers, 13 mm orifice spray nozzles, and 6.4 mm orifice spray nozzles, respectively, were installed to discharge water with various discharge densities into burning oil inside a pan. Rapid fire suppression was achieved, although fire flare-up was very pronounced and the interaction between the fire and the water spray was very intense. Test results showed that the systems using the nominal 6.4 mm orifice spray nozzles placed in a double-row 0.76 m above the oil surface, discharging a 20 mm/min density, yielded the best performance. The tests also indicated that bronze sprinklers or bronze spray nozzles may not be strong enough to use against auto-ignition fires inside a cooker. None of the stainless steel sprinklers or spray nozzles showed any damage after they were exposed to several test fires.
TL;DR: In this article, a geographic information system (GIS) model linked to property and valuation data is shown to be an appropriate tool for estimating urban fire losses, and a dynamic cellular automaton technique is used to determine both the rate and extent of fire-spread in response to a wide range of factors including wind, radiation, sparking, branding, building separations and building claddings.
Abstract: Fires after earthquakes sometimes develop into conflagrations resulting in widespread losses of life and property. A geographic information system (GIS) model linked to property and valuation data is shown to be an appropriate tool for estimating urban fire losses. One approach uses a static buffering technique to define potential burnout zones that are sampled randomly to give estimates of losses. The other uses a dynamic cellular automaton technique for determining both the rate and extent of fire-spread in response to a wide range of factors including wind, radiation, sparking, branding, building separations and building claddings. The dynamic approach uses a set of ‘rules’ based on fire physics modified by historical data. The model runs in real time for single ignitions. The static method is used to estimate losses assuming a 12m separation will prevent fire spread All buildings are assumed combustible (upper bound case). The dynamic model assuming fire can not spread to buildings with non-combustible claddings and areas of vegetation are not flammable (lower bound case). The resulting losses are between NZ$50M and NZ$500M (excluding building contents), compared with NZ$5,000M for shaking losses for a magnitude 7.3 earthquake and a total building stock of NZ$19,000M.