Cooling of Room Fires by Sprinkler Spray

Cooling of combustion products and the room by vaporizing water droplets appears to be a promising mechanism in sprinkler control of residential fires. An experimental procedure coupled with an energy balance scheme has been developed to obtain the heat absorption rate of a sprinkler spray. A test room was constructed, 3.05 × 3.66 × 2.45 m high, with a window. Hexane pool fires were selected to simulate room fires. The key parameters of investigation were water-discharge rate and drop size. For the room tested, a correlation has been established between the heat-absorption rate by the sprinkler water and the relative median drop size of the sprinkler spray. It is found that the rate of sprinkler water evaporated is directly proportional to the heat release rate and the water discharge rate, and varies as the minus 0.73 power of the relative median drop size. An extinction criterion for the hexane pool fire in the enclosure, based on the water evaporation rate at the time of sprinkler operation, has also been established.