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ICLASS 94<br>Proceedings of the Sixth International Conference on Liquid Atomization and Spray Systems

ISBN:
978-1-56700-019-1 (Print)
978-1-56700-445-5 (Online)

COMPUTER SIMULATION OF THE LIQUID AGENT SPRAY MOTION AND EVAPORATION

G. Gmurczyk
Building and Fire Research Laboratory, Gaithersburg, USA

L. Cooper
National Institute of Standards and Technology Gaithersburg, USA

William L. Grosshandler
National Institute of Standards and Technology, Gaithersburg, MD, USA

W.M. Pitts
Building and Fire Research Laboratory, Gaithersburg, USA

Abstract

The discharge of a liquid fire extinguishing agent stored in a pressurized vessel through an orifice generates a freely moving spray outside the vessel. The flow has been modeled as a two-phase, three-component, turbulent, compressible, dissipative flow. It has been assumed that the gaseous phase consists of agent vapor, nitrogen and oxygen, whereas the liquid consists of agent only. Viscosity, heat conduction, mass diffusion and turbulence have been included in the description. Interphase processes; such as Stokes forces and aerodynamic drag, forced convection and evaporation; have also been included. The spray is assumed to be a monodispersed phase described by the Sauter mean diameter. All the transport coefficients, the specific heats and the vapor pressure equation are temperature dependant. The impact of the gravitational field on the momentum exchange has also been included. The mathematical model describing the physical phenomena has been formulated with the use of the partial differential equations associated with the relevant initial-boundary conditions, expressing the balances of mass, momentum and energy. The set of time-dependant equations has been referred to the two-dimensional cylindrical geometry. The equations have been solved numerically with the use of time-marching finite-difference partially implicit scheme. The Conchas-Spray computer code of Los Alamos National Laboratory has been used to run the calculations. Sample results obtained for an extinguishing agent have been presented and the potential of the model and computer code have been discussed.