The use of halons for fire fighting is being phased out due to their deleterious effects on stratospheric ozone. This report summarizes the first-year findings of a three-year study designed to characterize and identify super-effective thermal fire-fighting agents as possible replacements for these effective compounds. Three distinct aspects related to the effectiveness of potential thermal agents have been considered. First, existing thermodynamic databases maintained by NIST have been searched in order to identify chemical compounds which are predicted to extract large amounts of heat from a combustion zone. Second, detailed chemical kinetic modeling has been used to characterize the effects of thermal agents on an idealized flame system, namely, a methane/air counterflow diffusion flame. Third, empirical heat transfer correlations for spray cooling of a surface have been used to estimate the efficiencies of surface cooling by thermal agents. The database search used two primary sources--the Design Iustitute for Physical Properties database containing 1458 compounds from 83 family types and a smaller database, REFPROP, containing 43 compounds which is tailored to refrigerant applications. Additional substances were included which are not well represented in these databases. Compounds having 1) high heats of vaporization, 2) liquid-phase heat capacities, and 3) total heat absorption due to phase changes (if applicable), heating of a liquid (if applicable), and the heating of the gas phase to combustion temperatures were identified. The results are reported in tables of compounds ordered in terms of their ability to extract heat. Detailed chemical kinetic modeling of opposed flow methane diffusion flames burning in air and air diluted with thermal agents has been used to obtain insights into the effectiveness of thermal agents and their mechanisms of flame extinction.
Citation: NIST Interagency/Internal Report (NISTIR) - 6414Report Number:
NIST Pub Series: NIST Interagency/Internal Report (NISTIR)
Pub Type: NIST Pubs
fire extinguishing agents, databases, diluents, diluent gases, fire extinguishment, reaction kinetics, surface cooling, temperature effects