Experimental Validation of Froude-Modeling-Based Physical Scaling of Water Mist Cooling of Enclosure Fires

Abstract

Fire suppression experiments were conducted in two geometrically similar enclosures of 3-to-1 ratio under fire products collectors to quantify water mist cooling of propane fires, to evaluate the scaling applicability of Froude modeling for water mist cooling of enclosure fires. The parameters considered in the evaluation were: enclosure size, door opening size, water mist spray condition, fire size, fire location and fireshielding condition. The two enclosures measured 1.22x1.22x1.22 m high and 3.66x3.66x3.66 m high. Two door opening sizes were tested for each enclosure: 0.30x0.61 m high and 0.61x0.61 m high for the Scale-1 enclosure and 0.91x1.83 m high and 1.83x1.83 m high for the Scale-3 enclosure. Propane fires were established on 0.3-m and 0.91-m diameter burners respectively for the two scaled enclosures. Four corresponding pairs of propane supply rates were selected according to the scaling requirement, producing 10 to 50 kW at Scale-1 and 150 to 800 kW at Scale-3. Two water mist nozzles operating respectively at 13.8 and 43.7 bar were used to produce the water mist sprays in the two enclosures. In each enclosure, nine nozzles were arranged in a 3x3 pattern at the ceiling level with equal nozzle-to-nozzle and nozzle-to-wall spacing. The results show that Froude modeling can be used to scale water mist cooling of enclosure fires under the present experimental conditions.