Validation and Assessment of a Water Mist Multi-hole Nozzle Model for Fire Simulations

In fire safety engineering, when codes and standards do not provide a good solution performance-based design appears the most effective approach to design protection systems for civil buildings and infrastructure. This circumstance often occurs for historical buildings under renovation, for large or complex buildings and for tunnels. In particular, numerical simulations of fire scenarios including evaporating sprays are very interesting due to the fact they have a great potential to assess the effectiveness of sprinklers, mist systems and fire fighting strategies that aim to control or suppress combustion. To do that, a fundamental knowledge of the sprays used and behavior is needed to obtain a good understanding of the effects on fire and smoke. Spray parameters seem different for every model and, besides, results are grid dependent, so comparisons with experimental data are needed to assure consistency of the conclusions. In this paper, the main focus is on the validation and assessment of a high-pressure single fluid water mist nozzle upon droplet dispersion and evaporation rates in different ambient air conditions in terms of temperatures and air humidity. Through the validation of a numerical set-up in OpenFOAM, it is possible to minimize the uncertainty that affect the description of the scenario when predicting its effectiveness in fire simulations.