In practical fire suppression systems for large rooms or compartments, water sprinklers are often located on or near the ceilings. In this configuration, the droplets from the water spray must be large enough to penetrate the high temperature thermal plume of the tire and reach the pool surface, yet be small enough to evaporate and provide effective suppression of the flame zone. The focus of this research is to investigate computationally the influence of initial drop size and spray system configuration on water suppression of medium to large scale (Le., -100kW) pool fires. The cases addressed are representative of ongoing experiments at the Naval Research Laboratories. The tire scenario examined in this study involves a 123 kW heptane pool fire located in a 3.05m (10 ft) cube enclosed facility. Results from this study indicate that (1) for large drops (Dd > 150 pm) an initial rise in temperature is observed associated with enhanced turbulent mixing before evaporative cooling takes place; (2) an optimum drop size is found that allows for maximum decrease in gas-phase temperature for one of the spray configurations examined: and (3) a low pressure spray with more nozzle locations appears to provide improved suppression when compared to using a single high pressure nozzle.
Citation: Special Publication (NIST SP) - 984-4
NIST Pub Series: Special Publication (NIST SP)
Pub Type: NIST Pubs