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Heat transfer is the mechanism by which a fire grows. Heat from a developing fire begins to heat up spaces and the surfaces of surrounding objects, possibly to a destructive point.
There are three methods in which a fire transfers heat:Conduction Conduction takes place through direct contact. The object generating the heat, usually by being heated itself, has to be in contact with the material being heated. The second object then begins to absorb the heat. The characteristics of the material being heated through conduction will dictate how fast it will combust. Here is an example of a fire developed from heat transfer through conduction: Suppose a welder is welding brackets to a steel pipe in a small building. In the adjacent building through which the piping continues, the walls have been covered with combustible spray-on insulation, and it is in contact with the pipe being welded. The heat developed by the welding operation will heat up the insulation to the point where the insulation bursts into flames. Convection Convection involves passing heat through a medium & either a gas, like air, or a liquid, such as water. This is the concept of how a fireplace or wood stove heats a room. The fire in the stove simply heats the air in the room, and the natural movement of the buoyant air through the space heats it up by setting up slight air currents as it displaces the cold air. Radiation Radiation is the transfer of heat through electromagnetic waves. It does not need a medium, and can transfer heat through a vacuum. The only effective ways to reduce radiative heat transfer is to provide open space, as the effect of radiated energy is reduced in the atmosphere, or to provide a solid object such as a wall, to deflect the energy.
© Hughes Associates,Inc. 2012