Solid fire extinguishment by water mist will be studied by using field modeling technique. The capability and limitations on modeling fire suppression with water mist will be discussed. The fire field model Fire Dynamics Simulator is selected as the tool. Full-scale burning tests with a water mist fire suppression system will be used for validating the predicted results. There, water droplet size, velocity, and water flux distribution from the nozzle measured were taken as parameters. Fire was set up by burning horizontal sheet of polymethylmethacrylate of 0.25 m square. As this CFD model is coupled to the solid surface, steady burning rates and extinguishment with water mist can be predicted. For the gas phase, the fire-induced flow is modeled with Large Eddy Simulation (LES), mixture fraction based combustion model, and discrete ordinate radiation model. For the liquid phase, water mist is described by a number of droplets tracked in a Lagrangian fashion. The interaction of mass, momentum, and heat transfer between water droplets and fire are included as source terms in the gas phase equations-i.e., the "Particle-Source-in-Cell" method. An analytical one-dimensional burning rate model of solid phase is employed, accounting for the energy balance of the solid fuel. Predicted results include: the gas flow vector, temperature, and water vapor mass fraction field; the surface temperature, heat flux, and burning rate distribution; and some relevant macroscopic combustion characteristics such as heat release rate, smoke production rate, carbon dioxide, and carbon monoxide yield rate. A comparison between the predicted and measured data is made in the end.
ASJC Scopus subject areas
- Chemical Engineering(all)
- Safety, Risk, Reliability and Quality
- Condensed Matter Physics