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Volume 41 (1992)
- Issue 2 Pages 41-
- Issue 1 Pages 1-
Volume 41, Issue 2
Displaying 1-4 of 4 articles from this issue
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Paper
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Wataru TAKAHASHI, Osami SUGAWA, Iichi OGAHARA1993 Volume 41 Issue 2 Pages 41-50
Published: 1993
Released on J-STAGE: January 10, 2012
JOURNAL FREE ACCESSThe fire retardance mechanism of magnesium hydroxide for ethylene copolymers were studied experimentally, using low density polyethylene (LDPE), ethylene-ethylacrylate copolymers (EEA) and ethylene-vinylacetate copolymers (EVAc). This study was carried out utilizing a high radiant furnace, thermogravimetry-gas chromatography (TG-GC) and infrared spectroscopy (IR). The results show that magnesium hydroxide have little fire retardance on polyethylene and on ethylene-vinylacetate copolymers, but have remarkable fire retardance on ethylene-ethylacrylate copolymers. The differences of the fire retardance effects in these polymer-Mg(OH)2 systems are due to the thermal stability of char layer formed on the polymer surface. The char formation is due to certain intermolecular reaction forming cross-linked structures in the system. In the case of ethylacrylate copolymers system, particularly, magnesium hydroxide reacts with ethylacrylate groups resulting the cross-links among the polymer chains, and both these reactions and char formation enhance the thermal stability against the burning propagation into the material. The dehydration of magnesium hydroxide gives also important effects for fire retardancy which is given by endothermic effects as well as dilution in gas phase.View full abstractDownload PDF (747K) -
M. KITANO, M. NAGANO1993 Volume 41 Issue 2 Pages 51-58
Published: 1993
Released on J-STAGE: January 10, 2012
JOURNAL FREE ACCESSExperiments of smoldering in a layer of flexible polyurethane foam under natural convection conditions were conducted, and effects of the propagation direction of smolder wave toward the buoyant force (downward and upward propagation) and the fuel layer thickness were investigated on smoldering characteristics, such as the intensity of energy input to initiate smolder, minimum energy for smolder wave to completely propagate through the fuel layer, smolder velocity, and maximum reaction zone temperature. The main findings were: (1) Smolder initiation and propagation was restricted within a certain range of energy input intensity. (2) One-dimensionality of the smolder wave was fairly good for the downward propagation, but not for the upward propagation, implying an occurrence of complex secondary flow inside the layer. (3) In the middle part of the layer where end surface effects of heating or heat loss were small, smolder velocities were nearly constant and the wave seemed to propagate steadily. Downward smolder was stronger (faster smolder velocity and higher maximum temperature) than upward smolder in this region. (4) Increasing the fuel layer thickness, which further restricted air suction under natural convection conditions, decreased smolder velocity as well as maximum temperature, suggesting that the limit for self-sustaining smolder might appear for much thicker fuel layers without a forced air supply.View full abstractDownload PDF (612K) -
M. KADOYA, H. MIYAGI, K. HARADA, T. TEARAI1993 Volume 41 Issue 2 Pages 59-67
Published: 1993
Released on J-STAGE: January 10, 2012
JOURNAL FREE ACCESSIt is well known that excessive depressurization caused by the mechanical smoke exhaust system creates difficulties in opening and closing the doors. This will also increase smoke leakage into depressurized areas. It is difficult to estimate flow rates and depressurization due to the lack of available data concerning the leakage of building elements other than the leakage around the doors.
Therefore, the authors took measurements in a nine story office building and carried out a computer simulation, then compared the data. The results of the measurements show that with all the doors closed the required force to open the door reached 8.2 [kgf], and the 70% of the exhaust volume comes through gaps in the doors, (15% from the assumed fire room, the rest from other rooms). The remaining 30% comes from gaps in fixtures, ceilings, air ducts and pipe shafts, for which the effective flow area amounts to 0.039 [m2].
In order to estimate the flow rates and depressurization through the computer simulation, a ventilation network was formed and the effects of the gaps were calculated. If the gaps corresponding to 30% of the leakage are neglected then the calculated pressure is higher than the measured pressure, however, the results are in agreement if all gaps are taken into account.View full abstractDownload PDF (820K) -
K. HARADA, T. TERAI, M. KADOYA, H. MIYAGI1993 Volume 41 Issue 2 Pages 69-75
Published: 1993
Released on J-STAGE: January 10, 2012
JOURNAL FREE ACCESSIn order to prevent excessive depressurization and smoke inflow in the area where a mechanical smoke exhaust system is operating, it is necessary to supply air to the area. In this paper a method is proposed to determine the required size of the air supply opening. This method was verified using the experiments conducted in the same building as in the previous paper. It was determined an opening with 0.073 [m2] of effective flow area is adequate to reduce excessive pressure to half in the case of an 80 [m3/min.] exhaust rate for the 50.6 [m2] floor area.
Two methods were used to determine the required air supply opening area; one by a precise ventilation network and another by a simplified equation. The required area can be predicted accurately by using the precise network method, however it is relevant to know the full route including leakage from gaps in doors, ceilings, air ducts and pipe shafts. That is quite difficult in a practical design process, because often they are altered by many factors including methods of construction, alterations of design, etc.
The simplified equation method also provides practical estimations of required air supply opening area if all the gaps are taken into account. If the door gaps only are taken into accounts, it gives somewhat large area, which will satisfy the safety requirements.View full abstractDownload PDF (666K)
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