Flame spread over solid surface coated with a layer of noncombustible porous material

Small-scale experiments are performed to determine the influence of noncomb ustible coating material on the behavior of flame propagation over solid fu els. Thick polymethylmethacrylate (PMMA) sheets are used as combustible mat erials, and sand layer is used as the solid coating material in the experim ents. The results of the experiments show that the size of the sand and the thickness of the sand layer have significant effects on the flame spread r ate. The influence is through the amount of heat flux absorbed by the unbur ned fuel surface and the mass diffusion of the vaporized fuel to react with the oxygen in the ambient air. As the sand layer thickness increases, the flame spread rate decreases. An inverse trend is observed with the increase of the sand size. In this paper, a simplified heat transfer model is propo sed for the flame spread rate over the combustible material with a layer of noncombustible porous material. The experimental results have been found t o be in agreement with the results from the model. Results from this study can be used in two areas. One is in understanding how flame spread is retar ded by application of porous material as an extinguishing agent. Another as pect is that more and more household items nowadays have a noncombustible c oating on the surface as a means of decoration, more fundamental informatio n on how the flame spreads is useful in future building fire safety designs .