Numerical investigation of water mist fire suppression effectiveness at various nozzle heights

Water mist fire suppression systems are used in machinery spaces and combustion turbine enclosures and now new applications such as data centres, sensitive storage areas, and heavy machine vehicles are appearing. These systems are a safe alternative to previously used suppression methods that use gas agents and have been found to be harmful to the environment. As the demand increases for these systems to be used in new and larger applications, it is important that the industry has a clear understanding backed by research on their suppression ability in different environments and fire hazards. The purpose of this research has been to understand the suppression mechanisms of water mist systems and explore if these systems can be suitable for large scale applications. This will expand the range of protection solutions available for fire safety engineers when faced with new potential fire hazards. This research includes an extensive literature review that has been conducted on academic research, fire tests previously completed, industry technical data on existing systems available on the market, and the codes and standards applicable to system design. A numerical investigation using Fire Dynamics Simulator (FDS) was completed to simulate a warehouse storage fire scenario to test water mist system suppression at various ceiling heights. It was found that water mist performance was reduced as nozzle height was increased. Changes to the water mist system were varied to understand how to maintain a strong suppression performance at these increased nozzle heights. Extinguishment was able to be achieved in all scenarios by increasing the system operating pressure and flow rate or using smoke detection as the form of system activation opposed to thermal detection. These findings led to recommended guidelines for designing water mist system parameters at various heights that can be used in the fire protection engineering industry.