Ability of Compressed-Air Foam to Absorb Heat and Mitigate Gas Propagation.

摘要

Despite their limited use, compressed-air foam systems (CAFS) have important benefits for firefighting, life safety and fire control including reducing water demand, limiting damage and mitigating adverse effects on the environment.;As compressed air-foam's (CAF) ability to extinguish a fire within one to two minutes is well documented, in this research, the immediate post-fire conditions were simulated by applying a heat source to the bottom of a foam layer to determine CAF's ability to cool hot surfaces.;A method of calculation was developed and validated to determine the convective heat transfer coefficient between steel and CAF in contact with a horizontal surface that is applicable for surface temperatures above 100°C.;The heat transfer coefficient was then used to calculate the optimal application density of CAF to provide the maximum rate of cooling.;The objectives of this study were to: (1) determine the heat absorption capacity of compressed-air foam, and (2) determine the foam's ability to mitigate gas propagation.;The ability of CAF to mitigate the transfer of hot gases was studied by first measuring the concentrations of CO2 that were generated by burning propane and subsequently propagated through the foam layer. It was concluded that, as long as the foam cover is intact, the propagation of CO2 is substantially reduced.;The results can be used to predict the ability of CAF to control products of combustion crossing a foam layer after the initial cooling of the surface. CAFSs could be used to control the spread of flammable vapours and therefore minimize the possibility of explosion in case of a flammable liquid spill. CAF could also provide a temporary control of gas evaporation of dangerous materials to ensure adequate environmental protection until specialized decontamination equipment can arrive at the site.