Generally, the fire and/or explosion are looked upon as main causes behind marine casualties. This has been backed by recent statistical data which showed that approximately 15.4 % of all marine casualties are caused by fire and/or explosion.
The fire accidents on board mostly occur in engine rooms. Hence, a number of requirements for the prevention, detection and extinction of fire in engine rooms have been incorporated into international conventions such as SOLAS (International Convention for the Safety of Life at Sea) and national regulations of different countries.
Among various fire safety related means available, fixed fire extinguishing system is used as a last resort to secure fire safety onboard. And out of many fixed fire extinguishing systems used in engine rooms, CO2 fire extinguishing system, which uses carbon dioxide(CO2) as fire extinguishing agent, is most common system in use at present.
Recently, however, there is an international trend to ban the use of CO2 due to its effect on the global warming. As a result, researches and studies are widely being conducted to develop an alternative fire extinguishing system in lieu of CO2 fire extinguishing system, a prime example being the water mist fire extinguishing system.
The fire extinguishing capability of water mist fire extinguishing system depends largely on the water supplying capacity to the protected space and the diameter of water mists. Consequently, proper pump capacity and pipe size and discharge pressure at water mist nozzle are very important.
To select proper pump capacity and pipe size, accurate estimation of flow rate and pressure at each position of piping system is required. And for the accurate estimation, a pipe network analysis need to be carried out. However, since the conventional pipe network analysis method such as Hardy-Cross method cannot analyze the flow rate and pressure at each position of water mist system, flow energy loss evaluation and pipe network analysis method, which consider characteristics of water mist system, were developed in this study.
Furthermore, to confirm the correlation between the discharge pressure at water mist nozzles and the diameter of water mists, a computational analysis for the flow characteristics (CFD) was performed using the actual dimension of water mist nozzle. The result of analysis showed that the water mist diameter gets smaller with the increase in discharge pressure. Also, it was confirmed that the increased discharge pressure leads to increase in surface area, i.e. heat transfer area, resulting in enhanced fire extinguishing capability. The comparison of analysis result with the measured result obtained using PIV showed that they are in agreement qualitatively.