Experimental and numerical study of water spray system for a fire event in a confined and mechanically ventilated compartment

Abstract

Summary The present work addresses the application of a water spray system in case of a fire event in large‐scale experiments for nuclear safety issues. It focuses on the interaction between a water spray system and a stratified smoke layer due to a pool fire in a mechanically ventilated enclosure. This study is supported by a set of four large‐scale tests and one numerical simulation with a 3D CFD software, named CALIF3S/ISIS, and developed by the French Institut de Radioprotection et de Sûreté Nucléaire (IRSN). The modelling used in this paper is based on an Eulerian‐Lagrangian approach. The fire tests are performed in a 165 −m3 mechanically ventilated single room. The fire is a lubricant oil pool fire of about 400 kW. The ventilation flow rate is 2550 m3.h−1 and corresponds to a renewal rate of 15.5 h−1. The spray nozzles are deluge and sprinkler type. The test parameters are the water flow rate, the time of activation, and the duration of activation. Based on the large‐scale experiments and the numerical simulation, four typical physical mechanisms have been enlightened. The first one corresponds to the cooling of the gas phase that is the straightforward consequence of the heat transfer exchange between the water droplets and the surrounding gas. The second effect is the process of gas mixing and homogenization induced by the water spraying system. The gas concentrations (O2, CO2) in the upper and lower parts of the room tend to the same level. The third effect is the significant increase of the fire heat release rate (HRR), up to 25 %, when the water spray is activated. Then, the last noteworthy effect is the occurrence of gas pressure peaks when the water spray is activated or shut off, consequence of the sudden change of the gas temperature. The processes of gas cooling and fire HRR increase are showed to be the main causes of these variations of gas pressure.

Optimized Design for Reliability of Pointer Irrigation Machine Components for Intelligent Computing

“…Reliability optimization of pivot irrigation parts has profound implications for the agricultural sector. Among them, Vaux et al resented its focus on the interaction between sprinkler systems and stratified smoke layers due to pool fires in mechanically ventilated enclosures in pivot system design [1]. Xu et al proposed that the high-fidelity visualization of fires in urban areas is rarely mentioned in existing models.…”

Effects of water spray on smoke layer in buildings with natural venting

“…When a water spray system is activated, additional pressure variations occur due to the sudden cooling of the gas phase. This phenomenon has recently been highlighted by Prétrel et al 9,12–14…”

“…When a water spray system is activated, additional pressure variations occur due to the sudden cooling of the gas phase. This phenomenon has recently been highlighted by Prétrel et al 9,[12][13][14] Few studies were done on spray droplet evaporation. This process was affected by parameters such as the initial water spray characteristics, smoke temperature and air velocity.…”

“…In recent decades, 11 effort has been made to improve the prediction capability of numerical tools and to develop efficient water spray systems for fire suppression, fire control or smoke cooling. Two main areas of interest have been identified: 12 the interaction between droplets and the flame with the goal of fire suppression, and the interaction between droplets and the smoke layer, for controlling the development of the fire environment.…”

Fire Plume in a Sharply Stratified Ambient Fluid

“…To perform the numerical simulation of a turbulent fire plume in a two-layer stably stratified fluid, we use the code CALIF3S-ISIS developed at the French Institut de Radioprotection et de Surete Nucléaire (IRSN), originally dedicated to the simulation of fires in mechanically ventilated compartments [28,29] and more generally to three-dimensional simulations of turbulent and slightly compressible flows (low-Mach-number approach). The Favre-averaged Navier-Stokes equations (mass and momentum balance) along with the heat transport equation are solved.…”