Pub Date : 2014-01-01DOI: 10.3801/iafss.fss.11-179
D. Pau, C. Fleischmann, M. Spearpoint, K. Li
The heat of reaction for the decomposition of polyurethane foam and its melt are determined from the heat flow measurements obtained through simultaneous differential scanning calorimetry and thermogravimetric analysis. Under nitrogen environment, the decomposition of foam experiences two endothermic pyrolysis reactions based on the experimental results. Through the investigation on the sensitivity of heat of reaction to heating rate and sample mass, a region where the heat of reaction remains constant is found for the melt samples tested. This consistent region includes heating rate from 5 to 20 °C/min and sample mass between ~20 and ~50 mg. No consistent region is found for the foam samples because of the reduced accuracy in the heat flow measured. For the foams and melts tested, the consistent heat of reaction for the second reaction ranges from endothermic 164 ‐ 295 J/g while the recommended heat of reaction for the first reaction ranges from endothermic 610 ‐ 1023 J/g.
{"title":"Sensitivity of Heat of Reaction for Polyurethane Foams","authors":"D. Pau, C. Fleischmann, M. Spearpoint, K. Li","doi":"10.3801/iafss.fss.11-179","DOIUrl":"https://doi.org/10.3801/iafss.fss.11-179","url":null,"abstract":"The heat of reaction for the decomposition of polyurethane foam and its melt are determined from the heat flow measurements obtained through simultaneous differential scanning calorimetry and thermogravimetric analysis. Under nitrogen environment, the decomposition of foam experiences two endothermic pyrolysis reactions based on the experimental results. Through the investigation on the sensitivity of heat of reaction to heating rate and sample mass, a region where the heat of reaction remains constant is found for the melt samples tested. This consistent region includes heating rate from 5 to 20 °C/min and sample mass between ~20 and ~50 mg. No consistent region is found for the foam samples because of the reduced accuracy in the heat flow measured. For the foams and melts tested, the consistent heat of reaction for the second reaction ranges from endothermic 164 ‐ 295 J/g while the recommended heat of reaction for the first reaction ranges from endothermic 610 ‐ 1023 J/g.","PeriodicalId":12145,"journal":{"name":"Fire Safety Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84103869","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-01-01DOI: 10.3801/iafss.fss.11-1326
D. Morvan, A. Lamorlette
The aim of this paper is to investigate the role played by the size (thickness) of solid fuel particles upon both the heat transfer and the propagation of a surface fire through a homogeneous vegetation layer. Because all the interactions (mass, momentum, and heat transfer) between the solid fuel layer and the gas phase occur at the interface between these two media, the surface area to volume (SA/V) ratio (inversely proportional to the thickness of the solid fuel particles), which appears in the expression of the specific surface separating these two phases, must affect, more or less significantly, the fire dynamics. This problem has been studied numerically, using a multiphase formulation. Various variables, such as the temperature of the solid fuel, the temperature of the gas, the fire residence time and the heat flux by radiation and convection have been analyzed, in order to understand the role played by the SA/V upon the behaviour of the fire.
{"title":"Impact of solid fuel particle size upon the propagation of a surface fire through a homogeneous vegetation layer","authors":"D. Morvan, A. Lamorlette","doi":"10.3801/iafss.fss.11-1326","DOIUrl":"https://doi.org/10.3801/iafss.fss.11-1326","url":null,"abstract":"The aim of this paper is to investigate the role played by the size (thickness) of solid fuel particles upon both the heat transfer and the propagation of a surface fire through a homogeneous vegetation layer. Because all the interactions (mass, momentum, and heat transfer) between the solid fuel layer and the gas phase occur at the interface between these two media, the surface area to volume (SA/V) ratio (inversely proportional to the thickness of the solid fuel particles), which appears in the expression of the specific surface separating these two phases, must affect, more or less significantly, the fire dynamics. This problem has been studied numerically, using a multiphase formulation. Various variables, such as the temperature of the solid fuel, the temperature of the gas, the fire residence time and the heat flux by radiation and convection have been analyzed, in order to understand the role played by the SA/V upon the behaviour of the fire.","PeriodicalId":12145,"journal":{"name":"Fire Safety Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83041323","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-01-01DOI: 10.3801/iafss.fss.11-1010
M. Benfer, D. Gottuk
This study was designed to experimentally characterize factors that can cause electrical failures (i.e., overheating connections), to assess the damage and potential forensic signatures of these failures, and to characterize the similarities and differences between arcing and melting in receptacle components and wiring. Laboratory testing evaluated the impact of a wide range of variables on the formation of overheating connections in residential duplex receptacles including screw terminal torque, wiring method (back-wired, or side-wired), and primary receptacle materials. A total of 408 trials of receptacles with various terminal connections were tested in the laboratory setting; receptacles were powered for up to 16 months. A small portion of receptacles with loose connections overheated to the point of failure of the receptacle; some including flaming events. Failure events occurred between 5 and 365 days after tests were started. Four hundred and sixty eight (468) receptacles were placed in compartment fire tests and furnace fire tests. These tests were designed to evaluate the persistence after fire exposure of overheating/arcing evidence from failure events (i.e., from potential fire cause events). The fire exposure tests also served to analyze the characteristic traits of arcing and melting damage. The results indicated that only very loose connections (less than 0.339 N-m [3 in-lb]) at moderately high currents (9A or higher) tend to form significant overheating connections and receptacle failures, irrespective of other variables such as receptacle materials and installation. Characteristic indicators of overheating and glowing terminal connections were identified and were found to persist after fire exposure.
{"title":"Electrical Receptacles - Overheating, Arcing, and Melting","authors":"M. Benfer, D. Gottuk","doi":"10.3801/iafss.fss.11-1010","DOIUrl":"https://doi.org/10.3801/iafss.fss.11-1010","url":null,"abstract":"This study was designed to experimentally characterize factors that can cause electrical failures (i.e., overheating connections), to assess the damage and potential forensic signatures of these failures, and to characterize the similarities and differences between arcing and melting in receptacle components and wiring. Laboratory testing evaluated the impact of a wide range of variables on the formation of overheating connections in residential duplex receptacles including screw terminal torque, wiring method (back-wired, or side-wired), and primary receptacle materials. A total of 408 trials of receptacles with various terminal connections were tested in the laboratory setting; receptacles were powered for up to 16 months. A small portion of receptacles with loose connections overheated to the point of failure of the receptacle; some including flaming events. Failure events occurred between 5 and 365 days after tests were started. Four hundred and sixty eight (468) receptacles were placed in compartment fire tests and furnace fire tests. These tests were designed to evaluate the persistence after fire exposure of overheating/arcing evidence from failure events (i.e., from potential fire cause events). The fire exposure tests also served to analyze the characteristic traits of arcing and melting damage. The results indicated that only very loose connections (less than 0.339 N-m [3 in-lb]) at moderately high currents (9A or higher) tend to form significant overheating connections and receptacle failures, irrespective of other variables such as receptacle materials and installation. Characteristic indicators of overheating and glowing terminal connections were identified and were found to persist after fire exposure.","PeriodicalId":12145,"journal":{"name":"Fire Safety Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80957919","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-01-01DOI: 10.3801/iafss.fss.11-346
J. Lassus, L. Courty, E. Studer, J. Garo, P. Aîne
An approach for estimating species concentration during a fire in a well-stirred compartment is investigated. A semi-empirical model based on oxygen concentration is used. It gives an estimate of the concentrations of carbon monoxide, carbon dioxide, hydrogen and hydrocarbons with a carbon chain length lower than five. Three intervals of oxygen concentration are noticed, they correspond to sufficiently ventilated, underventilated and very underventilated fires. In order to validate this model, fire experiments are performed in a reduced-scale compartment . Species concentrations predicted by the model are in good agreement with our experimental data and with those of literature. Coefficients used for the model are obtained for heptane and dodecane fires.
{"title":"Experimental approach to estimate species concentrations in a compartment fire","authors":"J. Lassus, L. Courty, E. Studer, J. Garo, P. Aîne","doi":"10.3801/iafss.fss.11-346","DOIUrl":"https://doi.org/10.3801/iafss.fss.11-346","url":null,"abstract":"An approach for estimating species concentration during a fire in a well-stirred compartment is investigated. A semi-empirical model based on oxygen concentration is used. It gives an estimate of the concentrations of carbon monoxide, carbon dioxide, hydrogen and hydrocarbons with a carbon chain length lower than five. Three intervals of oxygen concentration are noticed, they correspond to sufficiently ventilated, underventilated and very underventilated fires. In order to validate this model, fire experiments are performed in a reduced-scale compartment . Species concentrations predicted by the model are in good agreement with our experimental data and with those of literature. Coefficients used for the model are obtained for heptane and dodecane fires.","PeriodicalId":12145,"journal":{"name":"Fire Safety Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90239624","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-01-01DOI: 10.3801/iafss.fss.11-598
M. Bruns, K. Prasad
One-dimensional heat transfer in gypsum wallboard partitions is studied using sensitivity analysis and calibration by error minimization. Analysis of an existing heat and mass transfer model indicates that mass transfer and condensation of water vapor are not of primary importance in predicting board temperatures. A computationally efficient and robust heat transfer model is developed for predicting temperatures in gypsum wallboard partitions. Kinetic parameters are calibrated by error minimization with respect to literature thermogravimetric analysis (TGA) data. Additional thermophysical parameters are calibrated by error minimization with respect to literature ASTM E119 furnace test data. It is found that the calibrated heat transfer model is capable of predicting board temperatures given large thermal conductivities and specific heats at high temperatures. It is hypothesized that these observations imply the need to account for porous media radiation, temperature varying specific heats, and calcium carbonate decomposition in future models. Local sensitivity analysis reveals that board temperatures are most sensitive to initial density, thermal conductivity at moderately high temperatures ( 800 C), and the activation energy of the dehydration reactions. Conversely, model predictions are relatively insensitive to dehydration reaction pre-exponentials and low-temperature heat capacities.
{"title":"Parametric Analysis of Heat Transfer in Gypsum Wallboard Partitions","authors":"M. Bruns, K. Prasad","doi":"10.3801/iafss.fss.11-598","DOIUrl":"https://doi.org/10.3801/iafss.fss.11-598","url":null,"abstract":"One-dimensional heat transfer in gypsum wallboard partitions is studied using sensitivity analysis and calibration by error minimization. Analysis of an existing heat and mass transfer model indicates that mass transfer and condensation of water vapor are not of primary importance in predicting board temperatures. A computationally efficient and robust heat transfer model is developed for predicting temperatures in gypsum wallboard partitions. Kinetic parameters are calibrated by error minimization with respect to literature thermogravimetric analysis (TGA) data. Additional thermophysical parameters are calibrated by error minimization with respect to literature ASTM E119 furnace test data. It is found that the calibrated heat transfer model is capable of predicting board temperatures given large thermal conductivities and specific heats at high temperatures. It is hypothesized that these observations imply the need to account for porous media radiation, temperature varying specific heats, and calcium carbonate decomposition in future models. Local sensitivity analysis reveals that board temperatures are most sensitive to initial density, thermal conductivity at moderately high temperatures ( 800 C), and the activation energy of the dehydration reactions. Conversely, model predictions are relatively insensitive to dehydration reaction pre-exponentials and low-temperature heat capacities.","PeriodicalId":12145,"journal":{"name":"Fire Safety Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88180955","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-01-01DOI: 10.3801/iafss.fss.11-302
Ying Zhen Li, H. Ingason, Anders Lönnermark
A fire development analysis of three series of train carriage fire tests in different scales was carried out. These train carriage fire tests included 1:10 model scale tests, 1:3 model scale tests and 1:1 full scale tunnel tests. The heat release rate (HRR) correlations between different scales of carriage fire tests were carefully investigated. The mechanism of fire development is very similar in different scales of tests involving fully developed fires. After the critical fire spread, the fire travelled along the carriage at an approximately constant speed. The maximum heat release rate obtained for a fully developed fire is dependent on the ventilation conditions and also the type and configuration of the fuels, and a simple equation has been proposed to estimate the maximum heat release rate. A global correction factor of the maximum heat release rate is presented and examined.
{"title":"Fire development in different scales of train carriages","authors":"Ying Zhen Li, H. Ingason, Anders Lönnermark","doi":"10.3801/iafss.fss.11-302","DOIUrl":"https://doi.org/10.3801/iafss.fss.11-302","url":null,"abstract":"A fire development analysis of three series of train carriage fire tests in different scales was carried out. These train carriage fire tests included 1:10 model scale tests, 1:3 model scale tests and 1:1 full scale tunnel tests. The heat release rate (HRR) correlations between different scales of carriage fire tests were carefully investigated. The mechanism of fire development is very similar in different scales of tests involving fully developed fires. After the critical fire spread, the fire travelled along the carriage at an approximately constant speed. The maximum heat release rate obtained for a fully developed fire is dependent on the ventilation conditions and also the type and configuration of the fuels, and a simple equation has been proposed to estimate the maximum heat release rate. A global correction factor of the maximum heat release rate is presented and examined.","PeriodicalId":12145,"journal":{"name":"Fire Safety Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88282523","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-01-01DOI: 10.3801/iafss.fss.11-222
Xinyan Huang, M. Gollner
The time-dependent flame spread process over thermally thick slabs of polymethyl methacrylate (PMMA) is investigated with particular emphasis on the burning behavior and geometry of the flame. 10 cm wide by 20 cm long samples are ignited and allowed to spread upwards at angles of orientation between pool and ceiling burning. Correlations between the flame length and the fuel mass-loss rate have revealed a delayed transition to turbulence for flames residing on the underside of fuel samples, and an earlier transition to turbulence for flames on the topside of these samples, compared to traditional vertical wall flames. As the fuel inclination increases, the relationship between the flame length and fuel mass-loss rate ranges between a recent theoretical prediction for a laminar wall plume dominated by diffusion and the traditional prediction for a turbulent wall plume dominated by convective mixing. The buoyancy-induced flow field, characterized by the flame tilt angle is shown to correspond to previously-found modifications of heat-flux profiles ahead of the flame front, which control flame spread, and the heat flux to the burning surface of the fuel, which controls fuel mass-loss rates. Other correlations between some of these parameters, such as the flame and pyrolysis lengths are also presented as a function of inclination.
{"title":"Correlations for Evaluation of Flame Spread over an Inclined Fuel Surface","authors":"Xinyan Huang, M. Gollner","doi":"10.3801/iafss.fss.11-222","DOIUrl":"https://doi.org/10.3801/iafss.fss.11-222","url":null,"abstract":"The time-dependent flame spread process over thermally thick slabs of polymethyl methacrylate (PMMA) is investigated with particular emphasis on the burning behavior and geometry of the flame. 10 cm wide by 20 cm long samples are ignited and allowed to spread upwards at angles of orientation between pool and ceiling burning. Correlations between the flame length and the fuel mass-loss rate have revealed a delayed transition to turbulence for flames residing on the underside of fuel samples, and an earlier transition to turbulence for flames on the topside of these samples, compared to traditional vertical wall flames. As the fuel inclination increases, the relationship between the flame length and fuel mass-loss rate ranges between a recent theoretical prediction for a laminar wall plume dominated by diffusion and the traditional prediction for a turbulent wall plume dominated by convective mixing. The buoyancy-induced flow field, characterized by the flame tilt angle is shown to correspond to previously-found modifications of heat-flux profiles ahead of the flame front, which control flame spread, and the heat flux to the burning surface of the fuel, which controls fuel mass-loss rates. Other correlations between some of these parameters, such as the flame and pyrolysis lengths are also presented as a function of inclination.","PeriodicalId":12145,"journal":{"name":"Fire Safety Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88556920","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-01-01DOI: 10.3801/iafss.fss.11-234
W. An, H. Xiao, Jinhua Sun, K. Liew, W. Yan, Y. Zhou, L. Jiang, X. Huang
To study the effects of sample width and sidewalls on downward flame spread over extruded polystyrene (XPS) slabs, a series of laboratory-scale experiments were conducted. Flame shape, flame spread rate, mass loss rate and temperature were recorded. For XPS without sidewalls, the average maximum flame height (H) and average flame area per unit of width (A/w) rise linearly with an increase in sample width (w) and mass loss rate per unit of width. When sidewalls are absent, flame spread rate first drops and then rises with an increase in width. This trend is determined by gas-phase heat transfer. When sidewalls are present, flame spread rate increases with a rise in width, and solid-phase heat conduction determines the trend. Sidewall effects are comprised of four aspects: oxygen concentration near the sidewalls and gypsum board is low, which leads to reduced flame heat flux; upward and front air flow is intensified; the flame is stretched, and the surface flame is weakened; and molten XPS mass decreases. For narrow samples, H and A/w with sidewalls are higher than those without sidewalls, while the reverse was observed in wider samples. The mass loss rate, preheating length and average flame spread rate with sidewalls are smaller than those obtained without sidewalls. Flame spread acceleration with sidewalls occurs at a broader width than that without sidewalls. The experimental results agree well with the theoretical analysis.
{"title":"Effects of Sample Width and Sidewalls on Downward Flame Spread over XPS Slabs","authors":"W. An, H. Xiao, Jinhua Sun, K. Liew, W. Yan, Y. Zhou, L. Jiang, X. Huang","doi":"10.3801/iafss.fss.11-234","DOIUrl":"https://doi.org/10.3801/iafss.fss.11-234","url":null,"abstract":"To study the effects of sample width and sidewalls on downward flame spread over extruded polystyrene (XPS) slabs, a series of laboratory-scale experiments were conducted. Flame shape, flame spread rate, mass loss rate and temperature were recorded. For XPS without sidewalls, the average maximum flame height (H) and average flame area per unit of width (A/w) rise linearly with an increase in sample width (w) and mass loss rate per unit of width. When sidewalls are absent, flame spread rate first drops and then rises with an increase in width. This trend is determined by gas-phase heat transfer. When sidewalls are present, flame spread rate increases with a rise in width, and solid-phase heat conduction determines the trend. Sidewall effects are comprised of four aspects: oxygen concentration near the sidewalls and gypsum board is low, which leads to reduced flame heat flux; upward and front air flow is intensified; the flame is stretched, and the surface flame is weakened; and molten XPS mass decreases. For narrow samples, H and A/w with sidewalls are higher than those without sidewalls, while the reverse was observed in wider samples. The mass loss rate, preheating length and average flame spread rate with sidewalls are smaller than those obtained without sidewalls. Flame spread acceleration with sidewalls occurs at a broader width than that without sidewalls. The experimental results agree well with the theoretical analysis.","PeriodicalId":12145,"journal":{"name":"Fire Safety Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86488639","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-01-01DOI: 10.3801/iafss.fss.11-1035
R. Gracia, S. Mongruel, E. Wizenne
The consequences of a fire are twofold: an increase in temperature and heat fluxes, and smoke propagation at the source of the fire and in adjacent rooms. These may lead to malfunctions of fire safety electrical equipment in nuclear power plants. A survey of relevant literature has shown that the equipment most affected by smoke particles and gases are electronic boards. Smoke causes electronic boards to malfunction in four ways: loss of metallic contact due to chemical corrosion, increased short circuiting between the conductors, loss of mechanical contact conductivity, and reduced capacity for movement in electromechanical systems as a result of particle deposits. These effects can occur over different timescales: – In the short term, malfunctions that have critical impact in terms of plant safety occur – such as electrical short circuiting and increased contact resistance, – Mid to longer term, corrosion effects can appear. A test procedure based on the repeatability of a 20-minute duration cable fire was set up. Temperature and smoke composition in terms of both gaseous products and soot were controlled. Tests were performed on boards designed to sum test and regulation signals, or to control an analog chain fitted with relays. Although the behaviour of the equipment may be dependent upon its construction material and equipment layout, no electronic board malfunctions occurred during the 24-hour tests. Furthermore, no malfunctions were detected in the boards when they were retested six months later under normal conditions and without any clean-up following the smoke exposure.
{"title":"Effects of cable fire smoke on electronic boards","authors":"R. Gracia, S. Mongruel, E. Wizenne","doi":"10.3801/iafss.fss.11-1035","DOIUrl":"https://doi.org/10.3801/iafss.fss.11-1035","url":null,"abstract":"The consequences of a fire are twofold: an increase in temperature and heat fluxes, and smoke propagation at the source of the fire and in adjacent rooms. These may lead to malfunctions of fire safety electrical equipment in nuclear power plants. A survey of relevant literature has shown that the equipment most affected by smoke particles and gases are electronic boards. Smoke causes electronic boards to malfunction in four ways: loss of metallic contact due to chemical corrosion, increased short circuiting between the conductors, loss of mechanical contact conductivity, and reduced capacity for movement in electromechanical systems as a result of particle deposits. These effects can occur over different timescales: – In the short term, malfunctions that have critical impact in terms of plant safety occur – such as electrical short circuiting and increased contact resistance, – Mid to longer term, corrosion effects can appear. A test procedure based on the repeatability of a 20-minute duration cable fire was set up. Temperature and smoke composition in terms of both gaseous products and soot were controlled. Tests were performed on boards designed to sum test and regulation signals, or to control an analog chain fitted with relays. Although the behaviour of the equipment may be dependent upon its construction material and equipment layout, no electronic board malfunctions occurred during the 24-hour tests. Furthermore, no malfunctions were detected in the boards when they were retested six months later under normal conditions and without any clean-up following the smoke exposure.","PeriodicalId":12145,"journal":{"name":"Fire Safety Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76122664","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-01-01DOI: 10.3801/iafss.fss.11-361
Hui Wang, H. Sahraoui
A computational fluid dynamic model with full coupling between gaseous and liquid phases is developed to predict buring rates of liquid pool fires in ventilated full-scale tunnel. Rates of fuel release are calculated using predictions of flame feedback to the surface of the pool. A pool fire in tunnel is modelled as an unsteady process, from the time of ignition until convergence to a quasi-steady burning rate. This feedback supports sustained flame above the pool surface and controls the burning rate of the fuel. The numerical model solves three dimensional, time-dependent Navier-Stokes equations, coupled with submodels for soot formation and thermal radiation transfer. Turbulent combustion process is modelled by an Eddy Dissipation Concept (EDC) by using two chemical reaction steps to CO prediction. The numerical model is shown to possess the ability to predict the effect of ventilation on burning rate and the initial growth period in a fullscale tunnel fire. The current study indicates that CO generation is relatively independent of position in the overfire region, and correlated solely as a function of mixture fraction. While no correlation of soot concentrations in terms of the mixture fraction is found. Abundant CO and soot are formed around the fire base, which is later deflected near the tunnel ceiling, and the backflow brings about the toxic products with a noticeable smoke stratification as the airflow velocity is below a critical value.
{"title":"Mathematical Modelling of Pool Fire Burning Rates in a Full- Scale Ventilated Tunnel","authors":"Hui Wang, H. Sahraoui","doi":"10.3801/iafss.fss.11-361","DOIUrl":"https://doi.org/10.3801/iafss.fss.11-361","url":null,"abstract":"A computational fluid dynamic model with full coupling between gaseous and liquid phases is developed to predict buring rates of liquid pool fires in ventilated full-scale tunnel. Rates of fuel release are calculated using predictions of flame feedback to the surface of the pool. A pool fire in tunnel is modelled as an unsteady process, from the time of ignition until convergence to a quasi-steady burning rate. This feedback supports sustained flame above the pool surface and controls the burning rate of the fuel. The numerical model solves three dimensional, time-dependent Navier-Stokes equations, coupled with submodels for soot formation and thermal radiation transfer. Turbulent combustion process is modelled by an Eddy Dissipation Concept (EDC) by using two chemical reaction steps to CO prediction. The numerical model is shown to possess the ability to predict the effect of ventilation on burning rate and the initial growth period in a fullscale tunnel fire. The current study indicates that CO generation is relatively independent of position in the overfire region, and correlated solely as a function of mixture fraction. While no correlation of soot concentrations in terms of the mixture fraction is found. Abundant CO and soot are formed around the fire base, which is later deflected near the tunnel ceiling, and the backflow brings about the toxic products with a noticeable smoke stratification as the airflow velocity is below a critical value.","PeriodicalId":12145,"journal":{"name":"Fire Safety Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75487779","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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