Extinguishing class B fires with dry chemicals: Scaling studies

Abstract

In a continuing study of flame extinguishment, ~, 2, 3, 4 we report on scaling studies for dry chemicals on larger heptane diffusion flames (0.29 m 2 and 2.32 m 2 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 effectiveness 2,3 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 momenturn 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.

Experimental investigation of the fire extinguishing capability of ferrocene-containing water mist

“…As seen in Table 3, F1 ferrocene dispersions had significantly higher extinguishing abilities than F2 and F3 ferrocene dispersions. This result is entirely consistent with the finding that the extinguishing capability is negatively correlated with the particle size of the suppressant [39,40].…”

Extinguishing pool fires with aqueous ferrocene dispersions containing gemini surfactants

“…Typically, the particle size of a suppressant strongly governs its fire extinguishing ability (Ewing et al, 1995). Assuming that all fine ferrocene particles are spherical, the surface area of each S1…”

The effectiveness of open space fire extinguishing with flammable liquid fighting aerosols

“…Физико-химические характеристики состава STK-2MD [ При уменьшении размера частицы огнетушащая эффективность должна увеличиваться, что указано в работе [13], где исследовали тушение разных по площади модельных пожаров и показали, что мелкие частицы наиболее эффективны при тушении, так как их действие связано с поглощением тепла, разложением, испарением. При этом авторы указали, что ограничение размера частиц для каждого порошка (максимальный размер, который полностью разлагается или испаряется в пламени) не зависит от размера пламени для исследуемых систем.…”