**5. Conclusions**

The flow and diffusion characteristics of a typical candidate substitute for the halon fire extinguishing agents, namely, HFC-125 under different release pressures (2.41, 2.76, 3.1, 3.45, 3.79, and 4.14 MPa) were investigated in the present study. A series of parameters including the degree of superheat, the injection duration, the differential pressure in the pipeline, the jet structure, and the concentration distribution in the enclosure space were measured and analyzed. The major results and conclusions are summarized as follows.


It can be concluded from the present study that one nozzle is not enough to meet the requirement of MPS for HFC-125. Several nozzles and appropriate nozzle distribution design in the target enclosure space are needed.

**Author Contributions:** Conceptualization, J.J. and R.P.; methodology, J.J. and Q.L.; validation, R.P., Q.L., and R.C.; resources, R.P.; data curation, J.J. and X.X.; writing—original draft preparation, J.J.; writing—review and editing, R.P., Q.L., and R.C.; visualization, J.J.; supervision, R.P.; project administration, R.P.; funding acquisition, R.C. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the National Natural Science Foundation of China (no. 51806106) and the Natural Science Foundation of Jiangsu Province, China (no. BK20170838).

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.
