3. Results and Discussion
Table 2 summarizes experimental conditions and results. Characteristics of cooking oil fires, oil splash caused by water mist discharge as well as effectiveness of water mist against cooking oil fires were investigated.
During the experiments, palm oil was heated continuously. After the oil was heated over 230 °C, smoke appeared over the oil surface. During seven experiments, the oil auto ignited at temperatures ranging from 350 °C to 368 °C. The flame consumed all the fuel vapor over the oil surface that was generated in the heating period and quickly spread to the whole oil surface. During free burning, the fire was fully developed. A large amount of dark smoke was produced. The flame temperatures were high at the center of the oil pan and they decreased with an increase in distance from the center of the oil pan.
Fig. 5 shows the variation of the cooking oil temperature with time in a typical experiment. It takes aproximately 9 minutes for each scenarios for cooking oil fire to extinquised without applied water mist.
Fig. 6 shows variation of temperatures measured above the oil surface at four different locations of thermocouple with time. Once the water mist discharge was activated,