Experimental and numerical study of water mist fire suppression system effectiveness on shielded fire

This study aims to investigate the effectiveness of water mist on suppressing a shielded fire. Full-scale experiments are carried out in a partition room of (lxwxh) 2x2x2.5 m size. Five water mist nozzle which consist of two type nozzle was used, high flow (fogjet) nozzle installed at top center of the room and fine spray nozzle installed at each side of room at high 1.5 m from ground. The pressure of water mist system was maintained at 20 bar which correspond to 2.6 lpm of water flow rate. Wood crib of 6.5 x 6.5 x 6 cm size was used as the fuel source. The obstruction used as a fuel shield has table like form with 40 x 40 cm cover area and 0.5 m height. The location of fuel source and fuel shield was varied (1) fuel source and shield at centre of room, (2) fuel source at one side of shield and the shield at centre of room, (3) fuel source and shield at corner of room, and (4)) fuel source at one side of shield and the shield at corner of room. Numerical simulation using FDS 6.5.3 was also performed to validate the use of FDS and get better understanding of the phenomena. The results showed that water mist was able to extinguish the fire around 20 s, 16 s, 30 s, and 24 s for scenario 1, 2, 3 and 4 respectively. It is also observe that the mist distribution around the shield and cover area of the shield play a role on the capacity and time needed of water mist to extinguish the fire.