1. According to Fourier’s Law conductive heat transfer can be obtained using the equation
Q = k A ∆T/d where A is the heat transfer area (m2),
k is the materials thermal conductivity (W/m. K),
∆T is the temperature difference in Kelvins(K), and
d is the distance in metres (m).
If, for example, a wall constructed of solid copper was 100mm thick, had a surface area of 1m by 1m and the temperature on one side was 25 oC and the other 225 oC, conductive heat transfer can be calculated as;
1 Btu/ (ft h oF) = 1.731 W/ (m K)
213 Btu/ (ft h oF)* 1.731 = 368.703 W/ (m K)
Q = k A ∆T/d
Q= 400 W/ (m.K)*1 m2* (225 oC – 25 oC)/0.1m
Q = 800000W = 800 kW
2. Flame spreads faster when going vertically than horizontally.
3. This is because heat generally rises. This makes the material that is directly vertical to the fire to be preheated and to reach its lowest combustion temperature faster than the material that is horizontal to the fire. The material that is beside the fire is only heated by the radiant heat which has less effect than the heat burning the points directly above the fire. Most of the heat due to convectional currents is also lost in the atmosphere.
4. Intumescent coatings are substances that are used as insulators because of their insulating properties. When heated they expand and become denser, impairing heat transfer. They have various applications which include fireproofing and stopping of fires. They are used to coat aircraft and ships for the same reason.
5. Flame retardants have various disadvantages. The main reason why they may not be installed is their adverse effect on the environment. The toxic gas that they emit into the atmosphere during combustion leads to air pollution. Their production process is also characterized by the same problem.
