Numerical Evaluation of Wall Temperature and Heat Flux Reductions Provided by Water Curtain Systems

In this study, a numerical simulation was performed to determine the wall temperature and heat flux reductions provided by water curtain systems. A fire dynamics simulator (FDS) was used to quantitatively evaluate the fire spread prevention performance provided by these systems in a fire adjacent to factory buildings. The characteristics of the water curtain produced using the flat-fan spray pattern investigated in a previous experimental study were measured, and the results were utilized as nozzle-input conditions for the numerical simulations. These were performed for six cases involving combinations of two water supply pressures (0.12 and 0.2 MPa) and three spray patterns (flat-fan, full-cone, and hollow-cone) to compare the water curtain characteristics, masses of droplets reaching a wall, wall temperatures, and heat flux values under the scenario of a fire adjacent to a sandwich panel. The hollow-cone pattern exhibited the lowest wall temperature at the nozzle centerline, which was attributed to the large mass of the droplets reaching the wall. It also showed the lowest heat flux, which was due to the water curtain being discharged farther away from the wall. On the other hand, the full-cone pattern exhibited the lowest wall temperature at a position between nozzles, which was attributed to the large mass of the droplets reaching the wall. In addition, the 0.2 MPa condition decreased the wall temperature and heat flux more significantly than the 0.12 MPa condition as a result of increases in the water flow rate, spray angle, and amount of droplets reaching the wall, as well as the decrease in droplet size. Overall, under the numerical simulation conditions of this study, water curtains decreased the wall temperature by 98-207 °C and the heat flux by 5.35-15.58 kW/m².