ISSN:
1572-8099
Keywords:
Flame extinguishment
;
thermal mechanisms
;
flame quenching
;
theory
;
heat-absorption sinks
;
scaling
Source:
Springer Online Journal Archives 1860-2000
Topics:
Architecture, Civil Engineering, Surveying
Notes:
Abstract In a continuing study of flame extinguishment,1,2,3,4 we report on scaling studies for dry chemicals on larger heptane diffusion flames (0.29 m2 and 2.32 m2 pans). We demonstrate again that small particle sizes extinguish most effectively. Extinguishment is related to heat absorption by decomposing or vaporizing particles. We show that the limiting particle size for each dry chemical—that is, the maximum size which completely decomposes or vaporizes in the flame—is independent of flame size for the systems studied. We broaden and apply the concept of latent or maximum effectiveness2,3 to pan fires of all sizes. Finally, we describe and characterize an aerodynamic effect in the transport of powders, where large particles with their higher momentum entrain and drag smaller, more effective particles into the flame. We also show that extinction curves, involving the ratio of real-to-latent extinction weight and the proportion of small to large particles, have predictable shapes and predictable quantitative levels for most dry chemicals. We have developed the real-to-latent concept along with scaling equations for agent mixtures and for a wide spectrum of agents and particle sizes.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01305266
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