The dispersion performance is one of the most important factors that affects the extinguishing efficiency and application range of fire suppressants.
Table 5 shows the comparison of dispersion parameters of some typical fire extinguishing agents and the diffusion coefficient of the agents in air is calculated by the commonly used Fuller et al.
[37] method. The main difference between C
6F
12O and other kinds of suppressants is that C
6F
12O has a boiling point of 49.2 °C (1 atm), which is liquid at room temperature (25 °C) and could be considered a high boiling point suppressant. Compared to other gaseous fire extinguishing agents, the vapor pressure of C
6F
12O is the lowest and the dispersion performance is relatively poor, which would have a certain impact on the flow and spread of the fire suppressant after discharging, and further influence the fire extinguishing efficiency. There are relatively few studies on the dispersion characteristics of C
6F
12O. 3M company pointed out in their technical report
[6] that the evaporation rate of C
6F
12O is nearly 50-times faster than that of water, and it can be gasified and dispersed rapidly after releasing. The concentration of C
6F
12O vapor can reach 39% before its saturation, while the typical design concentration of C
6F
12O is less than 10%, which can meet the demand of the total flooding system. In addition, the vapor of C
6F
12O will not condense during fire extinguishing except pressuring or cooling below its dew point temperature (the vapor pressure of C
6F
12O can maintain 5% of the suppressant concentration at −16 °C). It is worth noting that due to its high boiling point, the storage pressure of C
6F
12O in a pressurized nitrogen atmosphere will not change largely with the temperature. In the temperature range of −40–80 °C, the maximum filling density of C
6F
12O is 1.8-times than that of other fire extinguishing agents with a low boing point (such as HFC 227ea). Hence, it is easy to store and transport, and has important application prospects in the fields of aerospace, oil exploration drilling platform, ocean-going ships and other fields with large working temperature difference ranges. Chen et al.
[38] obtained that the storage performance of C
6F
12O is better than Halon 1301 and HFC 227ea. Only when the filling density and initial filling pressure of the system are higher does the storage pressure of the system change obviously with the temperature. Meanwhile, the solubility of nitrogen in C
6F
12O is very low, which is related to the system temperature and initial filling pressure, indicating that nitrogen is appropriate to use as the driving gas, and the maximum filling density of 2.5 MPa and 4.2 MPa fire extinguishing systems are 1419 kg/m
3 and 1397 kg/m
3, respectively. Furthermore, compared with hexafluoropropane (HFC 236fa), which is gaseous at room temperature, C
6F
12O is in a two-phase flow state in the tube, with larger frictional resistance loss and the actual participation amount in cooling the fire after releasing is far less than the filling amount. Under the condition of high pressure, the cooling effect is better than HFC 227ea
[39]. Fan et al.
[40] investigated the flow characteristics of C
6F
12O compared with water and Halon 1301 through hydraulic calculation and experiments, which found that C
6F
12O conforms to single-phase flow in the more upstream sections of the pipeline and two-phase flow state in the main pipe, and the density of the mixture is only 1/26 that of liquid C
6F
12O. However, computational fluid dynamics (CFD) is a powerful method to investigate the flow of the medium, which is still lacking in the study of the flow characteristics of C
6F
12O. Xing et al.
[41] studied the method of improving the dispersibility of C
6F
12O by mixing with low boiling point inert gas (as shown in
Figure 3) and found the droplets diameter, the mixing ratio and the type of mixed inert gases would affect the dispersibility of binary agents. The method develops the binary agents with a lower boiling point and realizes that C
6F
12O is stored in liquid and released in gas, which could improve the dispersion performance of the high boiling point fire suppressant in its actual application.