Study on the Effects of Heat Flux Levels on Heat Release Rate of Wood

2003 ◽  
Vol 21 (1) ◽  
pp. 55-65 ◽  
Author(s):  
Jingwei Ji ◽  
Liz-Hong Yang ◽  
Xiaojun Chen ◽  
Weicheng Fan
Keyword(s):  
Heat Flux ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate

DNS of Flame-Wall Interaction and Heat Transfer in a Constant Volume Vessel

2010 ◽  
Author(s):  
Akihiko Tsunemi ◽  
Yoshihiro Horiko ◽  
Masayasu Shimura ◽  
Naoya Fukushima ◽  
Seiji Yamamoto ◽  
...  
Keyword(s):  
Heat Flux ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Burning Velocity ◽  
Fluid Velocity ◽  
Pressure Rise ◽  
Kinetic Mechanism ◽  
Constant Volume ◽  
Wall Interaction

Direct numerical simulations of turbulent hydrogen/air and methane/air premixed flames in a rectangular constant volume vessel have been conducted with considering detailed kinetic mechanism to investigate flame behaviors and heat losses. For the hydrogen cases, since heat release rate increases with pressure rise due to dilatation during combustion in the constant vessel, heat flux on a wall also increases. For the methane cases, the pressure increase does not raise wall heat flux significantly because of the decrescence of heat release rate caused by thermo-chemical reaction near a wall. Pressure waves caused by wall reflection fluctuate flame propagation for the hydrogen flames. Flame displacement speed decreases remarkably at the moment when the pressure wave passes through flame fronts from unburnt side to burnt side. However, the turbulent burning velocity at that time does not decrease because of increases of fluid velocity normal to the flame fronts.

A Comparison of the Behaviour of Spruce Wood and Polyolefins during the Test on the Cone Calorimeter

2013 ◽  
Vol 726-731 ◽  
pp. 4280-4287 ◽  
Author(s):  
Jozef Martinka ◽  
Emília Hroncová ◽  
Tomáš Chrebet ◽  
Karol Balog
Keyword(s):  
Heat Flux ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Cone Calorimeter ◽  
Lower Sensitivity ◽  
Average Heat ◽  
Fire Propagation ◽  
Spruce Wood

This article deals with comparison of the behaviour of spruce wood and polyolefins (polyethylene PE and polypropylene PP) during the test on the cone calorimeter. Samples were tested on the cone calorimeter at heat flux of 20 and 40 kW/m2. An evaluation of the behaviour of examined materials was based on the determination of the maximum and the average heat release rate, yield of carbon monoxide (CO), and relative comparison of tendency to fire propagation in a flashover phase. The tendency of materials to fire propagation in the flashover phase was evaluated based on the Pearson ́s correlation, the Spearman ́s correlation and the Kendall ́s correlation coefficient of HRR-CO and CO2-CO. Spruce wood showed better properties in comparison with PE and PP in all evaluated parameters (the maximum and the average heat release rate, the yield of CO, and also the resistance to fire propagation in the flashover phase. Additionally, spruce wood showed significantly lower sensitivity of dependence of the maximum and also the average heat release rate on external heat flux.

scholarly journals Fire Behavior of Thermally Thin Materials in Cone Calorimeter

Polymers ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1297
Author(s):  
Marouane El El Gazi ◽  
Rodolphe Sonnier ◽  
Stéphane Giraud ◽  
Marcos Batistella ◽  
Shantanu Basak ◽  
...  
Keyword(s):  
Heat Flux ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Cone Calorimeter ◽  
Fire Hazard ◽  
Heat Of Combustion ◽  
Sample Weight ◽  
Effective Heat ◽  
Effective Heat Of Combustion

In this study, a representative set of thermally thin materials including various lignocellulosic and synthetic fabrics, dense wood, and polypropylene sheets were tested using a cone calorimeter at different heat fluxes. Time-to-ignition, critical heat flux, and peak of heat release rate (pHRR) were the main parameters considered. It appears that the flammability is firstly monitored by the sample weight. Especially, while the burning rate of thermally-thin materials does never reach a steady state in cone calorimeter, their pHRR appears to be mainly driven by the fire load (i.e., the product of sample weight and effective heat of combustion) with no or negligible influence of textile structure. A simple phenomenological model was proposed to calculate the pHRR taking into account only three parameters, namely heat flux, sample weight, and effective heat of combustion. The model allows predicting easily the peak of heat release rate, which is often considered as the main single property informing about the fire hazard. It also allows drawing some conclusions about the flame retardant strategies to reduce the pHRR.

scholarly journals Test of total heat flux from wood crib fire in and outside compartment

2007 ◽  
Vol 11 (2) ◽  
pp. 197-206 ◽  
Author(s):  
Xu Qiang ◽  
Gregory Griffin ◽  
Christopher Preston ◽  
Ashley Bicknell ◽  
Glenn Bradbury ◽  
...  
Keyword(s):  
Heat Flux ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Total Heat ◽  
Total Heat Flux ◽  
Surrounding Area ◽  
Wood Crib ◽  
Gas Concentration ◽  
Space Effect

Woo d crib fires were studied by using of ISO 9705 Room. These free burning tests with different heat release rate were conducted inside room and outside room (under the hood). Thermal condition around crib fire was measured by using of thermocouples, total heat flux gauge, gas concentration analyzer, and standard instrumentations for heat release rate measurement in ISO 9705 Room. This paper focuses on the total heat flux to the surrounding area from wood crib fire. The correlation between heat release rate and total heat flux is presented. Wall and space effect is also analyzed.

scholarly journals Inversion for Fire Heat-Release Rate Using Heat Flux Measurements

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Andrew J. Kurzawski ◽  
Ofodike A. Ezekoye
Keyword(s):  
Heat Flux ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Fire Hazard ◽  
Computational Cost ◽  
Inversion Algorithm ◽  
Fire Dynamics ◽  
Oxygen Consumption Calorimetry ◽  
Flux Measurements

Abstract In fire hazard calculations, knowledge of the heat-release rate (HRR) of a burning item is imperative. Typically, room-scale calorimetry is conducted to determine the HRRs of common combustible items. However, this process can be prohibitively expensive. In this work, a method is proposed to invert for the HRR of a single item burning in a room using transient heat flux measurements at the walls and ceiling near the item. The primary device used to measure heat flux is the directional flame thermometer (DFT). The utility of the inverse method is explored on both synthetically generated and experimental data using two so-called forward models in the inversion algorithm: fire dynamics simulator (FDS) and the consolidated model of fire and smoke transport (CFAST). The fires in this work have peak HRRs ranging from 200 kW to 400 kW. It was found that FDS outperformed CFAST as a forward model at the expense of increased computational cost and that the error in the inverse reconstruction of a 400 kW steady fire was on par with room-scale oxygen consumption calorimetry.

scholarly journals Ignition Properties of Thermally Thin Plastics: The Effectiveness of Non-Competitive Char Formation in Reducing Flammability

2002 ◽  
Vol 6 (3) ◽  
pp. 155-181 ◽  
Author(s):  
M. I. Nelson ◽  
J. Brindley ◽  
A. C. Mcintosh
Keyword(s):  
Activation Energy ◽  
Heat Flux ◽  
Steady State ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Critical Mass ◽  
Single Step ◽  
Maximum Heat ◽  
Char Formation

The retardancy effect of char formation upon the flammability of thermally thin products is investigated. The char is formed in a single-step non-competitive scheme and is assumed to be thermally stable. The criterion for ignition is that of a critical mass flux of volatiles from the solid into the gas phase. Both steady-state and transient formulations of the model are considered. In the high activation energy limit the critical heat flux efficiency in the steady-state model is proportional to c/(1−c), where c is the fraction of char formed. In the transient model the efficiency in reducing the maximum heat release rate, average heat release rate, and total heat released is given by c and is independent of activation energy and heat flux. The specific application that we have in mind for our model is piloted ignition in the cone calorimeter.

Combustion Performance of Composite Floor with Different Radiant Heat Flux

2014 ◽  
Vol 501-504 ◽  
pp. 2415-2418
Author(s):  
Yan Ying Xu ◽  
Ruo Jun Wang ◽  
Jian Chen ◽  
Lu Chao Li
Keyword(s):  
Heat Flux ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Ignition Time ◽  
Radiation Heat ◽  
Radiation Heat Flux ◽  
Combustion Performance ◽  
Wood Flooring ◽  
Engineered Wood

The combustion performance of engineered wood flooring and intensive composite floor under the different radiation heat flux were experimented by cone calorimeter. Fire parameters were measured including the ignition time and heat release rate. Experimental results show that the ignition time of engineered wood flooring is much lower than intensive composite floor, and the ignition time are decreased with the increase of radiation heat flux. The heat release rate (HRR) curve has two peaks under the same radiation heat flux, and the first peak of the heat release rate of engineered wood flooring occurs significantly earlier than intensive composite floor. The heat release rate is increased and the first peak significantly ahead of time with the increase of the radiation intensity

scholarly journals Influence of Density on Foam Collapse under Burning

Polymers ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 13
Author(s):  
Abdoul Fayçal Baguian ◽  
Salifou Koucka Ouiminga ◽  
Claire Longuet ◽  
Anne-Sophie Caro-Bretelle ◽  
Stéphane Corn ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Polyurethane Foams ◽  
Pool Fire ◽  
Macroscopic Model ◽  
Infrared Cameras ◽  
Flexible Polyurethane

The fire behaviour of flexible polyurethane foams was studied using a cone calorimeter, with a special emphasis on the collapse step. Only one peak of heat release rate, ranging from 200 to 450 kW/m2, is observed for thin foams, depending on the foam density and the heat flux. On the contrary, heat release rate (HRR) curves exhibit two peaks for 10 cm-thick foams, the second one corresponding to the pool fire formed after foam collapse. In all cases, the collapse occurs at a constant rate through the whole thickness. The rate of the recession of the front was calculated using digital and infrared cameras. Interestingly, its value is relatively constant whatever the heat flux (especially between 25 and 35 kW/m2), probably because of the very low heat conductivity preventing heat transfer through the thickness. The rate increases for the lightest foam but the fraction of burnt polymer during collapse is constant. Therefore, the pool fire is more intense for the densest foam. A simple macroscopic model taking into account only the heat transfer into the foam leads to much lower front recession rates, evidencing that the collapse is piloted by the cell walls’ rigidity.

Bench-scale experimental study on the fire behavior of electric cable arrays by considering different layouts

2021 ◽  
pp. 073490412110432
Author(s):  
Zhou Cai ◽  
Xiao Chen ◽  
Jiaqing Zhang ◽  
Shouxiang Lu
Keyword(s):  
Heat Flux ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Fire Behavior ◽  
Radiant Heat ◽  
Radiant Heat Flux ◽  
Total Heat Release ◽  
Electric Cable ◽  
Peak Heat Release Rate

The effect of different cable layouts on the fire behavior of electric cable arrays was experimentally studied. The influence of external heat flux on cable fire characteristics was investigated. Several parameters for electrical cables such as the post-burning morphology, ignition time, heat release rate, peak heat release rate and total heat release were obtained. The results show that cable layouts could affect cable charring degrees according to the post-burning morphology. A linear relationship was found in the transformed form of time to ignition and radiant heat flux, and the critical radiant heat flux value for the single cable array appeared smaller than that for the other two layouts. The peak heat release rate for Cables A–D with the single array presents the increasing trend with an increase in radiant heat flux, while the two parallel and intersectional cable arrays present the different trends. Moreover, the total heat release values of Cables A–D in the different cable layouts were analyzed. This work provides the basic data and preliminary investigation to fire engineering of cable arrays with the different layouts.

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.

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