Dynamics of redirected flashing jets of a fire suppression agent

We discuss the dynamics of a jet of multi-phase fire suppression agent that issues from a simple pipe distribution network fed by a pressurized plenum and obliquely impacts a solid obstruction. One-dimensional multi-phase pipe flow simulations are used to estimate the time-varying discharge properties, including the liquid fraction at the exit plane. The flow is found to be choked and partially evaporated for the duration of the discharge event. We use two different models for the ash evaporation that will take place outside of the piping network. The first is a simple evaporation wave model where the flow is instantaneously accelerated as complete phase change occurs. This evaporation wave is anchored to the outflow of the distribution piping and results in a sonic single-phase jet that impacts the obstruction. The second model assumes the fluid is in thermodynamic equilibrium and phase change occurs along saturation curves as the local thermodynamic state changes due to the expansion of the jet. We compare the compressible wave structures and corresponding jet dynamics that result from the choice of phase change model.