Analysis of Water Mist Fire Suppression System Applied on Cellulose Fire

Shophouse (Rumah Toko) is a type of building that provides a combined functions for residential and business purposes. Fire risk of shophouse building depends upon the type and volume of the materials stored in the premises. Fire safety improvement for shophouses can be achieved by providing fast response and effective fire supression system such as water mist system. Water mist is a fire supression system that minimizes the risk of material damage by cooling the surface of fuel material. Wood, cellulose material, is one of the most common materials that can be found in shophouse building, thus it is used as fuel material in this experiment. The experimental work was performed in laboratory scale using a single full cone spray with various water pressures of 3, 5 and 7 bar and various fuel placement ((1) center of the room; (2) one corner of the room; (3) all 4 corners of the room). Comparison with numerical simulation using Fire Dynamics Simulator version 6.0 in 1:1 scale with the real test experiment was also performed. Wood crib of 12 cm x 12 cm x 27 cm sizes with an estimated heat release rate of 126 kW/m2 was applied in this work. The water mist nozzle was placed at 2.5 m height above the floor. The water was supplied by a stand alone pump. The results showed that water mist spray can extinguish the fire effectively under 5 minutes, with 7 bar system pressure as the fastest. Droplet coverage area measured from discharge nozzle, increased in accordance with the increase of water pressure. At higher water pressure, water mist can cover larger fuel surface and perform cooling action, to prevent fuel vapor from reacting with oxygen. Water usage calculated for water mist (NFPA 750) for each system pressure of 3, 5 and 7 bar was 0.15, 0.19, and 0.23 LPM/m3,respectively. It shows that water mist system requires far less water consumption than the calculated water requirements for sprinkler system (NFPA 13) of 0.79 LPM/m3 which uses the nozzle's K factor.