Fire Safety Science Digital Archive

A one/two-dimensional, quasi-steady heat-and-mass transfer model is presented to describe gas-sprinkler interaction. The spray droplet dynamics in gas flow is accounted for in heat transfer by introducing the droplet residential time into droplet number density. The model is capable, therefore, of simulating gas cooling effects in terms of sprinkler locations relative to fire source, initial droplet angles, velocities and droplet diameters. It is also capable of estimating the droplet evaporation rate and influence of gas flow parameters, such as velocity direction and magnitude, temperature and initial relative humidity. With combination of droplet dynamics and heat-mass transfer, an optimal droplet diameter is defined in gas cooling. The sensitivity of the spray model to the initial droplet angle, number of droplet trajectories to represent the sprinkler spray, droplet diameter distribution and relative fire sprinkler locations, has been demonstrated. Finally, a one-trajectory, single-size droplet model is adopted. Gas cooling rates calculated with this model and penetration predictions are compared with experimental data and other simulations from the literature.