Experimental performance evaluation of water mist fire suppression system

The present thesis attempts to understand the performance of the water mist fire suppression system, including the water mist nozzles and the whole system operation under different conditions through experiments and theoretical analysis. The impacts of the water mist nozzle, different fire parameters on the performance of the fire as well as the quantitative correlations between the fire size, i.e. the heat release rate of the fire and the room temperature change with respect to the extinguishing time were studied.;A comprehensive literature review of the studies of the water mist system conducted by different researchers and organizations in different countries has been carried out. It was found that under the ideal situation, water mist discharged is assumed to evaporate completely after coming into contact with the flame. With a proper design, the WMFSS can be used to extinguish electrical fires without danger. But the WMFSS was also found to have some limitations, for example its extinguishing performance is case-dependent and highly relates to the fire scenarios concerned. No "rule of thumb" type design standard is available. And three common types of water mist nozzles are widely applied including the impinging type, pressure-jet type and twin-fluid air-atomizing type.;30 full-scale experiments have been conducted. In the full-scale tests, different ventilation conditions, fire sizes, discharging methods of water mist, pre-burn time of the fire and the fire types were chosen as the testing parameters. The experimental results revealed that under the same operation condition of pressure and flow rate, factors like the fire size, type of fuel, pre-hum time and discharging method affected the performance of the WMFSS in different ways. Through results analysis, it was found that the extinguishing time is proportional to the heat release rate for liquid fires. The steady state room air temperature after extinguishment also increased with the heat release rate. The peak temperature difference was directly proportional to the extinguishing time. Some experimental findings agreed with the literature results. The study results are helpful to understand the effectiveness of the water mist system when facing different fire challenges.