Performance evaluation of water mist fire suppression: A clean and sustainable fire-fighting technique in mechanically-ventilated place

Abstract

Fire disasters occurring in the ventilated places often feature the harmless and pollution-free fire extinguishing methods, one of which is water mist. However, the application of water mist system in the forced-ventilated places is still a controversial issue. The main objective of this study is to present a systematic experimental investigation on water mist suppression performance in the mechanical ventilation conditions. A series of full-scale experiments were conducted in a glass-walled cabin with dimension of 3 m × 3 m × 3 m, measuring instantaneous flame height, smoke temperature, radiative and convective heat flux, and concentrations of oxygen and carbon monoxide. The coupling effect of water mist and mechanical smoke exhaust was revealed. Experimental results show that all the dimensionless maximum temperature rise, dimensionless rising and descending rates decline linearly with exhaust rate. Moreover, the dimensionless maximum temperature rise correlates well with the dimensionless height in a cubical relationship. The inhibitive effect of convective heat transfer is enhanced gradually with the increased mechanical exhaust rate. Both the turbulent mixing and radiation attenuation play significant roles in water mist fire suppression. Furthermore, the minimum value and descending rate of O2 concentration both tend to increase with exhaust rate, while the maximum value and rising rate of CO concentration change inversely. It is implied that the coupling of mechanical ventilation and water mist system is beneficial for personnel evacuation, and it provides a reference for the clean and sustainable fire-extinguishing system design.