scholarly journals Fire Growth Rate Index as a Key Fire Characteristic of Electrical Cables

2021 ◽  
Vol 29 (48) ◽  
pp. 81-90
Author(s):  
Jozef Martinka ◽  
Peter Rantuch ◽  
Igor Wachter ◽  
Tomáš Štefko ◽  
Martin Trčka ◽  
...  
Keyword(s):  
Heat Flux ◽  
Growth Rate ◽  
Aluminum Hydroxide ◽  
Cone Calorimeter ◽  
Unit Length ◽  
Heat Fluxes ◽  
Fire Growth ◽  
Ethylene Copolymer ◽  
Electric Cables ◽  
Electrical Cables

Abstract This study deals with the Fire Growth Rate Index (FIGRA) as a key fire characteristic of electrical cables (determined by a cone calorimeter) that allows to estimate their reaction to fire class. Three power (supply) electrical cables (reaction to fire class B2ca) were tested by a cone calorimeter using different heat fluxes of 20, 30, 40 a 50 kW·m−2. The cables were three-wire (cross-section of each wire was 1.5 mm2) with a nominal voltage of 0.6 kV (alternating current), resp. 1 kV (direct current). The cable sheaths were made of an ethylene copolymer filled with aluminum hydroxide. The beddings were made of an ethylene copolymer filled with a mixture of aluminum hydroxide and calcium carbonate. The conductor insulations of one electrical cable were made of crosslinked polyethylene and the conductor insulations of the other two electrical cables were made of an ethylene copolymer filled with aluminum hydroxide. FIGRA was determined per unit length and unit area of electrical cables. FIGRA increased with increasing heat flux. At a heat flux of 50 kW·m−2, all the electric cables examined showed a very similar FIGRA (from 0.19 to 0.21 kW·m−1·s−1 and 18.4 to 21.2 kW·m−1·s−1, respectively). Conversely, at a heat flux of 20 kW·m−2, the investigated cables showed greater FIGRA variance (in the range of 0.11 to 0.16 kW·m−1·s−1 or 10.8 to 16.2 kW·m−1·s−1).

Influence of grammage on heat release rate of polypropylene fabrics

2017 ◽  
Vol 36 (1) ◽  
pp. 30-46 ◽  
Author(s):  
Nicolas Hernandez ◽  
Rodolphe Sonnier ◽  
Stéphane Giraud
Keyword(s):  
Heat Flux ◽  
Growth Rate ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Cone Calorimeter ◽  
Heat Fluxes ◽  
Fire Growth ◽  
Time To Ignition ◽  
Moderate Change

The flammability of nine polypropylene fabrics or sheets has been tested using cone calorimeter at various heat fluxes (25, 35, 50, and 75 kW/m2) in order to assess the relevance of this fire test for thermally thin materials. The chosen procedure uses a grid and allows maintaining a constant exposed surface during the test, except for the lightest fabric. The structure of the knitted fabrics has a relatively small influence on the main flammability parameters. On the contrary, the area density of the sample (from 218 to 5729 g/m2) impacts strongly the time to ignition, the peak of heat release rate, and the increase in heat release rate after ignition (fire growth rate). At a fixed heat flux, thicker is the sample, higher are the time to ignition and the peak of heat release rate and lower is the fire growth rate. Moreover, thick samples exhibit the highest sensitivity of peak of heat release rate and the lowest sensitivity of fire growth rate to heat flux. This study emphasizes the fact that a moderate change in weight may have a significant influence on cone calorimeter results, without any significance on real flammability.

Modeling Exposures of a Nylon-Cotton Fabric to High Radiant Heat Flux

2016 ◽  
Vol 11 (3) ◽  
pp. 155892501601100
Author(s):  
Thomas Godfrey ◽  
Margaret Auerbach ◽  
Gary Proulx ◽  
Pearl Yip ◽  
Michael Grady
Keyword(s):  
Heat Flux ◽  
Cone Calorimeter ◽  
Burn Injury ◽  
Thermal Protection ◽  
Transient Heat Conduction ◽  
Radiant Heat ◽  
Heat Fluxes ◽  
Direct Result ◽  
Face Modeling ◽  
Flaming Combustion

American soldiers and marines involved in the recent conflicts in Iraq and Afghanistan have suffered increased incidence of burn injury, often as a direct result of exposure to improvised explosive devices. In this work, a one dimensional numerical pyrolysis model for transient heat conduction, incorporating material transformations described by chemical kinetics, is used to investigate the response of the standard 230 g/m2 Army Combat Uniform (ACU) fabric to high radiant heat fluxes in short duration thermal protection tests and long duration cone calorimeter tests. Thermal protection tests are performed using a Thermal Barrier Test Apparatus–an automated device, incorporating a closed-loop controlled IR radiant heat source, automated water cooled shutter, a fabric sample holder, an adjustable stage with a water cooled Schmidt-Boelter heat flux gauge and a PC based data acquisition system. Cone calorimeter tests are performed on fabric specimens at an exposure heat flux of 25 kW/m2. In thermal protection tests involving exposures of 90 kW/m2 for five seconds and 77 kW/m2 for four seconds, modeling indicated that desorption and evaporation of moisture content has an important effect, but melting of the nylon component and material decomposition had insignificant effects on the heat flux transmitted through the fabric back face. Modeling results for cone testing exhibited good agreement for time to ignition and duration of flaming combustion.

scholarly journals Effects of External Heat Flux and Exhaust Flow Rate on CO and Soot Yields of Acrylic in a Cone Calorimeter

2021 ◽  
Vol 11 (13) ◽  
pp. 5942
Author(s):  
Sun-Yeo Mun ◽  
Jae-Ho Cho ◽  
Cheol-Hong Hwang
Keyword(s):  
Heat Flux ◽  
Mass Flow ◽  
Flow Rate ◽  
Cone Calorimeter ◽  
Mass Loss Rate ◽  
External Heat ◽  
Heat Fluxes ◽  
Temperature Fields ◽  
The Mean ◽  
External Heat Flux

The effects of changes in irradiance level (external heat flux), exhaust flow rate, and hood height on CO and soot yield were examined using a cone calorimeter. Black acrylic, having similar constituents as polymethyl methacrylate, was used as a combustible, and external heat fluxes ranging from 15 to 65 kW/m2 were considered. Both auto and spark ignitions were applied as ignition methods. The difference in auto and spark ignition methods had no effect on CO and soot yields, or on the mass loss rate (MLR), heat release rate (HRR), and effective heat of combustion (EHC), which are global parameters of fire. As the external heat flux increased, the mean MLR and HRR linearly increased while the EHC remained constant. When the external heat flux increased, the mean mass flow rates of CO and CO2 had a directly proportional relationship with the mean MLR. Consequently, CO and CO2 yields remained constant regardless of the external heat flux. In contrast, the mean mass flow rate and mean MLR of soot were linearly proportional as opposed to directly proportional, and the soot yield thus increased linearly with external heat flux. Variations in the exhaust flow rate and hood height, which can alter the velocity and temperature fields in post-flame and plume regions, had almost no impact on CO and soot yields, as well as on MLR and HRR. The results of this study are expected to provide improved insight into conventional approaches on the recognition of CO and soot yields as unique properties of each combustible.

scholarly journals IMPACT OF THE ELECTRIC CABLES INSTALLATION ON THE IGNITION PARAMETERS OF THE SPRUCE WOOD SURFACE

Wood Research ◽  
2021 ◽  
Vol 66 (5) ◽  
pp. 732-745
Author(s):  
ALEŠ NEČAS ◽  
JOZEF MARTINKA ◽  
PETER RANTUCH ◽  
IGOR WACHTER ◽  
TOMÁŠ ŠTEFKO
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Ignition Temperature ◽  
Thermal Inertia ◽  
Thermal Response ◽  
Heat Fluxes ◽  
Wood Board ◽  
Spruce Wood ◽  
Board Surface ◽  
Electrical Cables

This study is aimed to investigate of an impact of electrical cables installed on Norway spruce (Picea abies(L.) Karst.) wood board surface on main ignition parameters (mainly critical heat flux, ignition temperature, thermal response parameter and thermal inertia). Ignition parameters have been determined by dependence of ignition times (raised to the power of -1, -1/2 and -0.547) on heat flux. Initiation times have been measured for three configurations of spruce wood boards with surface dimensions of 100 x 100 mm ± 1 mm (the first configuration: board without cables on surface, the second configuration: board with three electrical cables on surface -spacing between cables was equal to their diameter and the third configuration: board with five electrical cables -spacing between cables was equal to their diameter) at five heat fluxes (30, 35, 40, 45 and 50 kW·m-2). Obtained results proved that installation of the electrical cables on the spruce wood board surface has a significant impact on the ignition parameters. The critical heat flux (8.5 kW·m-2), apparent thermal inertia0.20 ± 0.02 kJ2·m-4·K-2·s-1and ignition temperature 324 ± 105°C of spruce wood board increased up to 18 ± 3 kW·m-2(critical heat flux), 0.68 ± 0.03 kJ2·m-4·K-2·s-1(apparent thermal inertia) and 475 ± 27°C (ignition temperature) by theinstallation of electrical cableson the surface of spruce wood board.

scholarly journals The melt/shrink effect of low density thermoplastics insulates: Cone calorimeter tests

2017 ◽  
Vol 21 (5) ◽  
pp. 2177-2187 ◽  
Author(s):  
Qiang Xu ◽  
Cong Jin ◽  
Jordan Hristov ◽  
Greg Griffin ◽  
Yong Jiang
Keyword(s):  
Heat Flux ◽  
Surface Area ◽  
Current Literature ◽  
Cone Calorimeter ◽  
Fire Behavior ◽  
Expanded Polystyrene ◽  
Heat Fluxes ◽  
Low Density ◽  
Test Results ◽  
Thermoplastic Foam

The melt/shrink effects on the fire behavior of low density thermoplastic foam have been studied in a cone calorimeter. The experiments have been performed with four samples of expanded polystyrene foams having different thicknesses and two extruded polystyrene foams. Decrease in surface area and increase in density, characterizing the melt/shrink effect have been measured at different incident heat fluxes. Three of these foams tested have been also examined by burning tests at an incident heat flux of 50 kW/m2. It was assessed that the fire behavior predictions based the current literature models provided incorrect results if the cone test results were applied directly. However, the correct models provided adequate results when the initial burning area and the density of the molten foam were used to correct the initial cone calorimeter data. This communication refers to the fact that both the effective burning area and the density of the molten foam affect the cone calorimeter data, which requires consequent corrections to attain adequate predictions of models about the materials fire behavior.

scholarly journals Assessing IDDES-Based Wall-Modeled Large-Eddy Simulation (WMLES) for Separated Flows with Heat Transfer

Fluids ◽  
2021 ◽  
Vol 6 (7) ◽  
pp. 246
Author(s):  
Rozie Zangeneh
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Large Eddy Simulation ◽  
Skin Friction ◽  
Heat Fluxes ◽  
Separated Flows ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Isothermal Wall

The Wall-modeled Large-eddy Simulation (WMLES) methods are commonly accompanied with an underprediction of the skin friction and a deviation of the velocity profile. The widely-used Improved Delayed Detached Eddy Simulation (IDDES) method is suggested to improve the prediction of the mean skin friction when it acts as WMLES, as claimed by the original authors. However, the model tested only on flow configurations with no heat transfer. This study takes a systematic approach to assess the performance of the IDDES model for separated flows with heat transfer. Separated flows on an isothermal wall and walls with mild and intense heat fluxes are considered. For the case of the wall with heat flux, the skin friction and Stanton number are underpredicted by the IDDES model however, the underprediction is less significant for the isothermal wall case. The simulations of the cases with intense wall heat transfer reveal an interesting dependence on the heat flux level supplied; as the heat flux increases, the IDDES model declines to predict the accurate skin friction.

scholarly journals Drift kinetic theory of alpha transport by tokamak perturbations

2021 ◽  
Vol 87 (2) ◽  
Author(s):  
Elizabeth A. Tolman ◽  
Peter J. Catto
Keyword(s):  
Heat Flux ◽  
Kinetic Theory ◽  
Alpha Particle ◽  
Heat Fluxes ◽  
Alpha Particles ◽  
Alpha Power ◽  
Mode Amplitude ◽  
Effective Collision Frequency ◽  
Perturbation Frequency ◽  
Particle Confinement

Upcoming tokamak experiments fuelled with deuterium and tritium are expected to have large alpha particle populations. Such experiments motivate new attention to the theory of alpha particle confinement and transport. A key topic is the interaction of alpha particles with perturbations to the tokamak fields, including those from ripple and magnetohydrodynamic modes like Alfvén eigenmodes. These perturbations can transport alphas, leading to changed localization of alpha heating, loss of alpha power and damage to device walls. Alpha interaction with these perturbations is often studied with single-particle theory. In contrast, we derive a drift kinetic theory to calculate the alpha heat flux resulting from arbitrary perturbation frequency and periodicity (provided these can be studied drift kinetically). Novel features of the theory include the retention of a large effective collision frequency resulting from the resonant alpha collisional boundary layer, correlated interactions over many poloidal transits and finite orbit effects. Heat fluxes are considered for the example cases of ripple and the toroidal Alfvén eigenmode (TAE). The ripple heat flux is small. The TAE heat flux is significant and scales with the square of the perturbation amplitude, allowing the derivation of constraints on mode amplitude for avoidance of significant alpha depletion. A simple saturation condition suggests that TAEs in one upcoming experiment will not cause significant alpha transport via the mechanisms in this theory. However, saturation above the level suggested by the simple condition, but within numerical and experimental experience, which could be accompanied by the onset of stochasticity, could cause significant transport.

Thermal decomposition of multilayer honeycomb core laminate sandwich composite panels in cone calorimeter apparatus – Effect of the top decomposed layer

2021 ◽  
pp. 002199832199087
Author(s):  
Hussain Najmi ◽  
Jocelyn Luche ◽  
Thomas Rogaume
Keyword(s):  
Cone Calorimeter ◽  
Single Layer ◽  
Heat Fluxes ◽  
Decomposition Process ◽  
Phase Iii ◽  
Sandwich Composite ◽  
Back Surface ◽  
Multilayer Composite ◽  
In Fire

Multilayer composite materials are frequently used in aircraft interiors. Even though they have high properties (such as physical, chemical and mechanical properties), their application is limited due to lack of knowledge of their decomposition process and on the interaction between different layers in fire. In the present work, two types of composites with 3 and 4 layers are studied. The fire characterization of multilayer composite is studied in 3 different phases using ISO-5660 cone calorimeter at two heat fluxes (35 and 50 kW.m−2). Phase-I mainly concentrates on the decomposition of single layer materials (paint, laminate and honeycomb) while in phase-II and phase-III, different assemblies are formed using a single layer material and studied in the same experimental configuration. In all the three phases, back surface temperatures of the materials or assemblies are measured and analyzed with different gas productions which allow to understand the dynamics of the decomposition process. The finding from the cone calorimeter study suggests that the ignition primarily depends on the top layer behavior of the composite. The permeability analysis on the top layer of the composite confirms that decomposed layer of paint offers more resistance to the volatile gases escaping from the composite. At the end of the study, thermal conductivity is determined and the ignition temperature of both the composite is determined.

scholarly journals Air–Sea Interaction in the Central Mediterranean Sea: Assessment of Reanalysis and Satellite Observations

2021 ◽  
Vol 13 (11) ◽  
pp. 2188
Author(s):  
Salvatore Marullo ◽  
Jaime Pitarch ◽  
Marco Bellacicco ◽  
Alcide Giorgio di Sarra ◽  
Daniela Meloni ◽  
...  
Keyword(s):  
Heat Flux ◽  
Mediterranean Sea ◽  
Seasonal Cycle ◽  
Heat Fluxes ◽  
Meteorological Variables ◽  
Central Mediterranean ◽  
High Quality ◽  
Central Mediterranean Sea ◽  
In Situ Observations

Air–sea heat fluxes are essential climate variables, required for understanding air–sea interactions, local, regional and global climate, the hydrological cycle and atmospheric and oceanic circulation. In situ measurements of fluxes over the ocean are sparse and model reanalysis and satellite data can provide estimates at different scales. The accuracy of such estimates is therefore essential to obtain a reliable description of the occurring phenomena and changes. In this work, air–sea radiative fluxes derived from the SEVIRI sensor onboard the MSG satellite and from ERA5 reanalysis have been compared to direct high quality measurements performed over a complete annual cycle at the ENEA oceanographic observatory, near the island of Lampedusa in the Central Mediterranean Sea. Our analysis reveals that satellite derived products overestimate in situ direct observations of the downwelling short-wave (bias of 6.1 W/m2) and longwave (bias of 6.6 W/m2) irradiances. ERA5 reanalysis data show a negligible positive bias (+1.0 W/m2) for the shortwave irradiance and a large negative bias (−17 W/m2) for the longwave irradiance with respect to in situ observations. ERA5 meteorological variables, which are needed to calculate the air–sea heat flux using bulk formulae, have been compared with in situ measurements made at the oceanographic observatory. The two meteorological datasets show a very good agreement, with some underestimate of the wind speed by ERA5 for high wind conditions. We investigated the impact of different determinations of heat fluxes on the near surface sea temperature (1 m depth), as determined by calculations with a one-dimensional numerical model, the General Ocean Turbulence Model (GOTM). The sensitivity of the model to the different forcing was measured in terms of differences with respect to in situ temperature measurements made during the period under investigation. All simulations reproduced the true seasonal cycle and all high frequency variabilities. The best results on the overall seasonal cycle were obtained when using meteorological variables in the bulk formulae formulations used by the model itself. The derived overall annual net heat flux values were between +1.6 and 40.4 W/m2, depending on the used dataset. The large variability obtained with different datasets suggests that current determinations of the heat flux components and, in particular, of the longwave irradiance, need to be improved. The ENEA oceanographic observatory provides a complete, long-term, high resolution time series of high quality in situ observations. In the future, more similar sites worldwide will be needed for model and satellite validations and to improve the determination of the air–sea exchange and the understanding of related processes.

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