The boreal forest or Taiga occupies one third of forest area in the world. From spring to fall, the risk of fire is high in this region due to low precipitation regime which amounts to less than 300mm. Due to ongoing global climate change, fire incidence in high latitude may increase because of the observed decreasing trend of summer precipitation. In 2002, many large-scale forest fires occurred near Yakutsk, the capital city of the Sakha Republic in Siberia. The total burnt area was estimated at more than 23,000km2, this burnt area is the largest reported in Sakha since 1955 and about ten times larger than mean burnt area (about 2,400km2). In 2003, forests near the Baykal lake in Siberia burned severely. The total burnt area in Russia (whole Siberia) was estimated at more than 234,000km2. In 2004, many large-scale forest fires occurred in Alaska. The main cause was lightning. Many of them grew into large-scale fires due to severe drought conditions and the presence of Chinook or Foehn phenomenon. As a result, the total burnt area in 2004 was about 26,000km2, the largest historical record since 1956. To protect the Taiga from severe forest fires due to global climate change, it is important to investigate the trends and characteristics of not only forest fire occurrences but also weather.
It is empirically well known that a moist fire protection material shows good heat protection characteristics. From this fact, a fire protection material is made of mixture of cement mortar in which water storage materials such as silica gels or moist perlites are mixed. The latent heat of water in the fire protection material plays an important role in the resistance to temperature rise. In this study, the fire resistance tests of a fire protection material of high water content is conducted and the temperature response of the test material is measured. The test material consists of the perlite mortar in which the sodium meta-silicate are mixed as the water storage material. The water content, the thermal conductivity and the fire resistance time of the test materials were measured. The water content of the test materials ranges from 30.1 to 38.6 mass % and the thermal conductivity of the test materials ranges from 0.66 to 0.7 W/(mK). The fire resistant time of one of the test materials of 60 mm thick is about190min.
This paper describes the results of the simulation of backdraft with the one-zone modeling. The one-dimensional pyrolysis model was added to the one-zone model in order to consider supplying pyrolysate from a flammable wall. Also the heat generation model with first-order Arrhenius' equation was added to consider the heat generation due to the oxidizing pyrolysate after a self-extinction. The temperature peak was shown in the result of simulation. This temperature peak was consequence of a backdraft. Then, the backdraft simulation was carried out in several opening parameters and types of opening. In AH1/2=0. 02m5/2 window type opening case, the backdraft occurs most frequently. In this case, six backdrafts occur. In too large (AH1/2 > 0.06m5/2) or too small (AH1/2 < 0.005m5/2) opening case, the backdraft does not occur. In the AH1/2=0.03m5/2 door type opening case, eight backdrafts occur and in AH1/2=0.01m5/2 slot opening case, four backdrafts occur. These results suggested that frequency of backdraft depends on the height of opening, the sill height and the opening parameter, AH1/2.
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