Numerical Simulation on Water Mist Fire Suppression Effects and Mechanisms in Hot and High Humidity Surroundings

Abstract On account of the fire development rules with great complexity and uncertainty in hot and high humid confinement spaces, fire suppression effects and mechanisms by water mist of different pressures in confined space with one opening at surroundings of different temperature (40oC/26.5oC) and different humidity (RH 90% / 37.5%) were simulated by FDS. The flame and the smoke layer temperature, the heat radiation received by the floor and the oxygen near the flame were analyzed. It is concluded that under the experimental and simulated conditions in this paper, in hot and high humid environment, the flame cooling effect by the water mist is less significant than that in normal surroundings, and decreasing with the increase of the water mist pressure. The reason is the stronger perturbation to airflow near the flame root by the higher pressure water mist, so the average flame temperature decreases slowly. With the increase of pressure, the cooling effect on smoke layer is enhancing. At hot (40oC) and high humidity (RH90%) environment, the cooling effect on smoke layer by water mist is weaker than that in normal temperature and humidity environment, but the gap is reduced with the increase of water mist pressure. The heat radiation attenuation effect is more significant in hot and high humid surroundings than that in normal environment, and increasing with the increase in pressure. With the increase of water mist pressure, the temperature and humidity of surroundings, the oxygen concentration reduction rate will be greater, and the oxygen suffocation effect will be more significant. The researches have important theoretical and application value for application of water mist fire suppression technology.