A Study on Actual Delivered Density of Water Application Under the Effects of Fire Sources

Water application has been used widely and considered as one of the most reliable fire extinguisher systems. Although Actual Delivered Density (ADD) is a vital property to evaluate its performance that fire can be suppressed when the value of ADD is higher than that of Required Delivered Density (RDD). It is still unclear how to accurately estimate the amount of water penetrated through flames, which is essential to calculate ADD. The purpose of this study is to assess the influential factors of ADD and to establish proper evaluation criteria of water application. To this end, a series of experiments were conducted to measure the effects of a fire source on the amount of spraying water delivered by water application. The variable parameters include the type of head, the height between head and fire source (later, spraying height), the dimensions of the fire source, and the heat release rate. The experimental results show that the spraying height and the nozzle characteristics can dramatically influence the water penetration ratio. Furthermore, when JJXP060 was within 0.5 m spraying height, the ADDs were significantly affected by the scale of the fire source. Large-scale fire source scenarios were also simulated using Fire Dynamics Simulator (FDS). It shows that the ratio of the ADD with a fire source to the ADD without a fire source, directly below a nozzle at 3 m height, is within 10%, and its value does not decrease as the scale of fire increases. Lastly, a simple predictive model was calibrated experimentally, which can serve as a tool to estimate the amount of water penetrated through flames.