Abstract
Depending on the size of water drops, process of fire extinguishing is focused either in a zone of combustion or on a burning liquid surface. This article considers two alternate solutions of a heat balance equation. The first solution allows us to trace decrease of temperature of a flammable liquid (FL) surface to a temperature lower than fuel flash point at which combustion is stopped. And the second solution allows us to analyze decrease of burnout rate to a negligible value at which steam-air mixture becomes nonflammable. As a result of solve of a heat balance equation it was made the following conclusion: water drops which size is equal to 100 μm will completely evaporate in a zone of combustion with extent of 1 m if the flying speed of drops is even 16 mps (acc. to Stokes v = 3 mps); whereas drops of larger size will evaporate only partially.
Highlights
In automatic fire extinguishing systems as dispersive devices it is usually used drenchers and sprinklers which provide coarse-particle dispersion of water with the average diameter of drops about 2 mm [1,2,3]
In this case suppression of FL with flash point more than 90 ° C is occurs due to cooling of its surface to a temperature at which the speed of evaporation of a flammable liquid is insufficient for forming of concentration of fuel in gas-air mixture required for combustion
The process of suppression in this case is reduced to following aspects: - cooling of the surface, - absorption of the heat flow, moving from flame jet to a surface of flammable liquid, by water drops
Summary
In automatic fire extinguishing systems as dispersive devices it is usually used drenchers and sprinklers which provide coarse-particle dispersion of water with the average diameter of drops about 2 mm [1,2,3]. It is supposed that drops of large sizes practically don't evaporate in a gas phase as because of high flying speed of drops so of its small specific heat-exchange surface. In this case suppression of FL with flash point more than 90 ° C is occurs due to cooling of its surface to a temperature at which the speed of evaporation of a flammable liquid is insufficient for forming of concentration of fuel in gas-air mixture required for combustion. Depending on the size of water drops extinguishing process is focused either in a zone of combustion or on a burning liquid surface. Decrease of temperature in combustion zone leads to reduction of the input rate of fuel vapors in it [12]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
