A Study on the Structural Optimization of Multiwater Mist Nozzle for Improved Spray Stability

This study aimed to develop a sealed multiwater mist nozzle equipped with a dual filtration system and empirically verify its performance to address life safety risks of gas-based fire suppression systems and chronic orifice clogging issues of conventional water mist nozzles. The nozzle structure was optimized by integrating a built-in debris collection space and cone spring mechanism to ensure stable atomization (<i>D</i><sub><i>v</i>0.99</sub> 300 <i>μ</i>m) even under a low-pressure condition of 7 bar. The extinguishing performances for Class A (wood) and Class B (n-heptane) fires were quantitatively evaluated by full-scale cabinet fire tests. The experimental results showed that in Class A fires, the internal temperature rapidly dropped below 100 °C within an average of 22 s postactivation, achieving complete suppression via deep-seated cooling without reignition. In case of Class B fires, the flames were completely suppressed within 25 s, thereby confirming the excellent suffocation and initial cooling effects of the developed nozzle on combustible vapors. Consequently, the developed multiwater mist nozzle exhibits fire control performance equivalent to or greater than that of conventional gas agents, which shows its engineering feasibility as a highly reliable water-based suppression solution for high-value special hazard environments, such as data centers.