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森林在着火之后,火就会向四周和上下不断地扩展和蔓延,使大片森林发生火灾,这就是星星之火可以燎原的原因。火在森林中所以能自由蔓延,无限制地进行扩展,这与热的传播方式有着密切关系。热的传播方式总的来说有三种,即热对流,热辐射和热传导,前两种热的传播,主要是将热能传送到可燃物的表面,即可燃物之间的外部传热方式,而后一种则是可燃物在其内部的传热方式,这三种热的传播对林火的蔓延都起到一定的作用。热对流:众所周知,热空气比冷空气轻,在强风作用下,使对流热转为平流热,产生使火能过大江的现象,例如:1979年在大兴安岭林区春防期间的一次火灾,在15米/秒的大风影响下,林火越过三百米宽的嫩
After the fire in the forest, the fire will continue to expand and spread around and up and down, causing fire in large forest areas. This is why the spark of the stars can start a prairie fire. Fire in the forest so it can spread freely, unlimited expansion, which is closely related to the way of heat transmission. In general, there are three modes of heat transmission: convection, thermal radiation and heat conduction. The first two types of heat are mainly transmitted to the surface of combustibles, that is, the external heat transfer between combustibles, and then One is the way in which combustibles heat transfer, and the spread of these three heats all play a role in the spread of fire. Thermal Convection: It is well-known that hot air is lighter than cold air and under the action of strong winds, the convection heat is converted into advection heat, resulting in the phenomenon that the fire can cross the river. For example, a fire during the spring prevention in Daxing’anling District in 1979 Under the influence of the strong wind of 15 m / s, the forest fire crossed the width of 300 meters