An experimental study of the effects of water mist characteristics on pool fire suppression

Suppression of pool fire by a water mist is influenced by mist characteristics, its location and orientation relative to the fire. A heptane pool fire was generated in 1 m x 1 m x 1 m chamber in a 125 mm diameter pan. Mist was generated with a pair of twin-fluid atomizers installed at the ceiling centre. Nitrogen at 4-8 bar and 104-136 LPM flow rate aspirated water at 0.18-0.22 LPM. Mean droplet diameter and velocity measured at 500 mm and 850 mm from the atomizer were 18-30 mu m and 2.2-3.2 m/s, respectively. The fire was produced at four locations and mist was activated 30 s after fire initiation. Temperatures were measured along the flame centreline at 160, 360 and 560 mm above the fuel surface. CO, CO2 and O-2 concentrations were also measured. Mean droplet diameter decreased and velocity increased with increasing nitrogen pressure. Fire suppression time decreased with increasing gas pressure approaching asymptotic value for pressures greater than 6 bar for all location of fire. The fastest suppression (12-18 s) was achieved for fire at the chamber centre where mist spray was symmetrical and slowest (47-68 s) for farthest location of fire from mist. (C) 2012 Elsevier Inc. All rights reserved.