Development of a computational model simulating the interaction between a fire plume and a sprinkler spray

Abstract

Numerical simulations to predict actual delivered densities (ADDs) of early suppression fast response (ESFR) sprinklers in heptane spray fire scenarios were sought. First, in order to supply input data for the development of numerical models and experimental data for validation of the models, four sets of measurements were carried out: the momentum and water flux distribution of two ESFR sprinkler sprays without fire; the temperature and axial velocities along the axis of free-burn fires; and the actual delivered densities. Then, a numerical model for a sprinkler spray was completed by assigning the representative drop size, mass flow rate, discharge speed and discharge angle of 275 trajectories in such a way that they produced reasonable agreement with the measured water flux distribution and spray momentum in the absence of fire. A numerical model for the free-burn fire was created by assigning a heat flux distribution on a horizontal surface and simulating a central, vertical air jet used in the experiment, varying parameters until a reasonable match was established with the measured temperatures and the axial velocities along the axis. Numerical computations of actual delivered densities were carried out by combining the water spray model and the free-burn fire model for different water flow rates of the sprinklers. The ADDs obtained from the simulations compared reasonably well with those from the measurements.