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RISS 인기검색어
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- 발행기관 : Technomic Publising (검색결과 3 건)
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Roh, Jae Seong,Yang, Seung Shin,Ryou, Hong Sun Technomic Publising 2007 Journal of Fire Sciences Vol.25 No.2
<P>In this study, the 1/20 reduced-scale experiments using Froude scaling are conducted to investigate the effect of longitudinal ventilation velocity on the burning rate in tunnel fires. The methanol pool fires, acetone pool fires, and n-heptane pool fires with a heat release rate ranging from 2.02 to ~6.15 kW, 2.76 to ~11.04 kW, and 2.23 to ~15.6 kW, respectively, are used. A load cell is used to measure the mass loss rate of the burning fuel and the temperature distributions are measured by K-type thermocouples in order to investigate smoke movement. The ventilation velocity in the reduced-scale tunnel is controlled by the wind tunnel through an inverter. In the case of a methanol pool fire, the increase in ventilation velocity reduces the burning rate. On the contrary, for acetone and n-heptane pool fires, the increase in ventilation velocity leads to the enhanced burning rate of fuels. The reason is that, for acetone and n-heptane pool fires, the oxygen supply effect prevails rather than the cooling effects as the ventilation velocity increases. However, for a methanol pool fire the cooling effect outweighs the effects of oxygen supply. The relationship between the critical velocity (V<SUB>c</SUB>, m/s) and the heat release rate (Q, MW), for a full tunnel, has been found to be:&illegible;.</P>
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Thermal degradation and flammability behavior of fire-retarded wood flour/polypropylene composites
Sun, Lichao,Wu, Qinglin,Xie, Yanjun,Cueto, Rafael,Lee, Sunyoung,Wang, Qingwen Technomic Publising 2016 Journal of Fire Sciences Vol.34 No.3
<P>Magnesium hydroxide, expandable graphite, and ammonium polyphosphate were used to enhance the thermal stability and fire retardant properties on wood flour/polypropylene composites. The thermal decompositions and flammability properties were investigated using modulated thermogravimetric analysis and cone calorimeter, and the activation energy of each decomposition process was also determined by modulated thermogravimetric analysis. The results showed that both expandable graphite and ammonium polyphosphate promoted thermal degradation of wood flour and char formulation, and magnesium hydroxide did not influence on the wood flour decomposition. Unlike in nitrogen atmosphere, magnesium hydroxide and ammonium polyphosphate increased the peak temperature of wood flour thermal degradation and diminished the decomposition peaks of polypropylene in air atmosphere. Cone calorimeter results showed that expandable graphite greatly reduced the heat and smoke release. A general activation energy range of 187-226kJmol(-1) (in nitrogen), 165-206kJmol(-1) (in air) at wood flour degradation stage, 237-262kJmol(-1) (in nitrogen), and 185-269kJmol(-1) (in air) at polypropylene degradation stage were proposed for wood flour/polypropylene composite with and without fire retardants.</P>
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Shik Han, Yong,Dong Shin, Hyun Technomic Publising 2007 Journal of Fire Sciences Vol.25 No.6
<P>The vortex behavior and thickness of the nozzle fluid layer of pulsating jets under a ceiling are studied using the laser-assisted visualization technique. The vortex formation characteristics of jets pulsating at different frequencies are compared with those of continuously issuing jets to investigate the effects of the pulsating frequency on the thicknesses of the nozzle fluid layers under a ceiling. To identify similarities between the features of pulsating isothermal jets and periodically pulsating pool fires, the frequencies of the pulsating jets are determined using the results obtained from previous pool fire studies. The formation and propagation characteristics of vortices in pulsating jets are investigated, along with the effects of the pulsation frequency on the thickness of the nozzle fluid layer. The size of the first primary vortex generated decreases as the pulsation frequency of the jet increases. The thickness of the nozzle fluid layer of pulsating jets is larger than that of continuously issuing jet, although the first primary vortex is smaller. The thickness of the nozzle fluid layer increases with decreasing pulsation frequency in jets with the same Reynolds number. The results of this study show the possibility that the ceiling jet behavior including the thickness of the smoke layer induced by a pulsating real fire plume can be strongly related to the pulsation frequency of the plume.</P>
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