Fire Dynamics Simulator Analysis of Smoke Confinement and Radiation Shielding using Water Mist Curtains

Abstract

This research was conducted to numerically analyze the smoke confinement and radiation shielding characteristics of water mist curtains during the process of plume flow that propagates along the ceiling after its occurrence in fire source. We reviewed the flow field based on the location of the spray, size of water mist droplets, temperature distribution, and soot distribution. The optical density extracted at a height of 1.5 m and the thermal radiation attenuation rate values were comparatively analyzed. In the case of no water-mist operation, the temperature and soot concentration were stable as they formed a layer toward the floor from the ceiling. By contrast, when the water mist curtain was operational, the spray flow obstructed the ceiling jet flow and caused considerable mixing. The results from reviewing the optical density predictions showed that it tended to decrease at a distance sufficiently far downstream of the curtain, but overall the effect was not meaningful compared to the case of no water-mist operation. This was considered to be because a considerable number of fine droplets, as well as soot particles included in the smoke, affected the optical density. Conversely, the attenuation rate of thermal radiation was greatly affected by the average size of the droplets. In the case when the location of the water mist curtain was x<sub>inj</sub> = 6 m, the thermal radiation attenuation rate at the lowermost part changed from 79.0%, 29.7%, and 17.0% as the average spray droplet size increased from 200, 500, and 1,000 <i>μ</i>m., respectively.