How to improve efficiency of using water when extinguishing fires through the explosive breakup of drops in a flame: Laboratory and field tests

The study reports results of the experimental research on the explosive breakup of heterogeneous water drops in high-temperature (800-1200 K) conditions typical for fires. The temperature of heating conforms to mean values for large forest fires. We use water drops containing special-purpose inclusions, such as 1-3 mm solid opaque particles (natural graphite). Laboratory experiments enable us to define conditions for the intensive fragmentation of such the drops. This process is characterized by formation of droplets of smaller size. The number of fragments can be from several ones to several hundreds. As a result, the evaporation surface area of liquid increases 3-15-fold during such the fragmentation. This effect is important for the most complete water evaporation in a flame during the fire extinguishing process. In such a case, the maximum temperature reduction in a flame zone becomes possible by absorption of heat of phase change. Field tests show that the usage of suspensions based on water facilitates a dramatic drop in temperature in a flame zone by 40-70 K as compared to water without additives. Consequently, fire extinguishing occurs during shorter time and by using smaller volume of water. Both the Characteristics can decrease by 30-40% as compared to water without additives. (C) 2017 Elsevier Masson SAS. All rights reserved.