Numerical method for determining water droplets size distributions of spray nozzles using a two-zone model

Abstract

The water spray systems is widely used for fire safety area and is a well-established technique for providing safety and protection of nuclear installations and also in industrial facilities. One major challenge is to be able to properly determine the technical features of the water spray system that are required for predictive simulations. For that, a Phase Doppler Interferometer (PDI) device, that is a complex and challenging laser technique, is often used to measure the droplet size distributions and the droplet velocities. However, some usual water spray models can require as input parameters only an overall droplet size distribution and an initial velocity and some statistical methods are needed to determine them from local accurate measurements. In this paper, it is addressed a new calibration approach for assessing the input parameters of this modeling by using large-scale and wellcontrolled fire tests. Then, by introducing some correlations to take into account different operating conditions of the pressure at the nozzle head, this technique is validated on other large-scale fire tests. After discussing thoroughly the results, this new method shows that it can be a valuable and efficient tool for determining the overall features of water spray systems linked with the modeling of water spray system used in this study.

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

“…The water phase is represented by a population of representative droplets (or samples), themselves composed by a fixed number of single identical droplets. Thanks to the calibration technique developped by Plumecocq et al,the droplet size distribution (with an assumption of lognormal distribution) produced by the deluge spray nozzle during the PR2_FES_1 fire test was assessed previously by some experiments using a gas burner. For a volume flow‐rate of 55 l.min −1 , the lognormal distribution of the nozzle is characterized by a mass median diameter of 5.6 10 −4 m, a geometric standard deviation of 0.405 and an initial droplet velocity of 7 m.s −1 .…”

Horizontal cable tray fire in a well‐confined and mechanically ventilated enclosure using a two‐zone model

“…The model of horizontal cable tray fire was implemented in the SYLVIA software developed at IRSN. This software is designed to predict the behaviors of mechanical/natural ventilation, fire growth, hot gas and smoke propagation, and airborne contamination transfer in confined and mechanically ventilated enclosures.…”

“…Pure aeraulic simulations in connection with the ventilation requirements (design of ventilation networks, aeraulic balancing, studies of the wind effect on airborne contamination transfer and their release to the environment …) are possible with the SYLVIA software . For more details about the SYLVIA modeling, see Plumecocq et al…”

“…In this paper, the ignition of the upper cable tray is performed by the assessment of the thermal stress on it due to the flame located on the lower tray. This new modeling was implemented in the two‐zone model SYLVIA and is here applied to the IRSN cable fire tests in order to validate properly the SYLVIA software. Such an approach is very useful in fire design of NPPs or some such to predict the fire spread on cable trays including both the thermal properties of cables and the distance separating each tray.…”

An Approach to Determine the Median Diameter of Droplets in a Water-Mist Spray

“…The first concern is that these laser-based methods are very expensive and require specialised techniques. The second concern is that the size distribution of water droplets and their initial velocity are susceptible to the pressure at the nozzle head [15]. Therefore, with regard to experimental studies, the drop size of sprays has represented a challenge for decades as a parameter to be quantitatively determined [7].…”