Mixing and Evaporation of Potential Halon 1301 Replacement Agents Following Release from Pressurized Bottles
William M. Pitts, Jiann C. Yang, B D. Breuel
The mixing and evaporation behavior of releases of potential halonreplacements for fire suppression have been investigated as part of a USAFadministered Halon Replacement Project. Ten agents have been considered: FC-31-10, FC-318, HCFC-124, HFC-227, HFC-l34a, FC-218, HCFC-22, HFC- 125, HFC-32, and HFC-32/HFC-125 azeotrope. For comparison purposes, halon 1301 has also been investigated. The weighed amount of agent to be tested was placed in a 500 cm3 vessel constructed from either plexiglass or stainless steel. The vessel was equipped with a burst disk designed to release at a preset pressure which was generally 4.1 MPa (41 atmospheres). After filling with the agent, an experiment was initiated by pressurizing the vessel with nitrogen to the bursting pressure. A number of diagnostics were used to characterize the dynamics and mixing behavior outside the vessel. High-speed films provided visualization of the flows. A laser extinction technique allowed measurements of the velocity for the downstream edge of the released material. Dynamic pressure transducers located near the vessel orifice and on the flow centerline 1.3 m downstream of the vessel provided qualitative characterization of the degree of vaporization. A sonically-choked hot-film probe provided additional characterization of the flow at the downstream location. The results show that the velocities for the agent flows as well as their mixing behaviors are strongly dependent on the degree of superheating of the agent. A new mechanism for agent dispersion involving the impingement of a high-speed nitrogen flow on the liquid stream has also been identified. The degree of vaporization for a given downstream position is found to depend on the degree of superheating, the Jakob number, and the molar density of the liquid. It is shown that effective dispersion and evaporation of these agents is enhanced by high superheats, high Jakob numbers, and a low molar density for the liquid
, Yang, J.
and Breuel, B.
Mixing and Evaporation of Potential Halon 1301 Replacement Agents Following Release from Pressurized Bottles, Other, National Institute of Standards and Technology, Gaithersburg, MD, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=909893
(Accessed December 8, 2023)