EFFECT OF AIR VELOCITY ON PYROLYSIS OF FIRE RETARDANT COATINGS EXPOSED TO AIR HEATED AT CONTROLLED TEMPERATURES

A general model for the behavior of a fire retardant coating exposed to a flame or heated air is presented. Successive and simultaneous steps are considered: heat transfer by convection through air from the fire to the coating face; heat transfer by conduction through the coating followed by pyrolysis; and the effect of air velocity responsible for the type of convection, motionless, laminar or turbulent. The particular value of Nusselt number is shown to be of interest. The study is conducted for coatings of different thicknesses within the 80-320 micron range, when exposed to air heated with a logarithmic rate of increase in temperature.