Accession Number : ADA137952

Title :   Dry Chemical Development - A Model for the Extinction of Hydrocarbon Flames.

Descriptive Note : Memorandum rept.,


Personal Author(s) : Ewing,C T ; Hughes,J T ; Carhart,H W

PDF Url : ADA137952

Report Date : 08 Feb 1984

Pagination or Media Count : 32

Abstract : An empirical relation has been developed which correlates and predicts the suppression effectiveness of a wide variety of gaseous, liquid, and solid agents. The flame extinguishment model is based on the premise that extinction is dominated by heat absorption processes and that a flame is extinguished when sufficient heat has been removed by the extinguishment to reduce the temperature to a limit value. This limit is the minimum temperature at which the effective rate of the combustion reactions is sufficient to maintain flame propagation, and it depends in a predictable way on the properties of the suppressant and flame system. The heat-balance equation describing this is derived in two stages. In the first, a preliminary equation is obtained by considering only those substances which are thermally stable and act only as heat capacity sinks. In the second, the equation is generalized by consideration of all endothermic reaction sinks, e.g., vaporization, dissociation, and decomposition. The general equation correlates most of the extinction data found in the literature. The results suggest that for many substances the extinguishing capacity is related to heat extraction and that many of the effects previously attributed to chemical mechanisms are thermodynamic in nature rather than kinetic. (Author)

Descriptors :   *Fire extinguishing agents, *Chemicals, *Extinguishing, *Flames, *Mathematical models, Fire suppression, Gases, Liquids, Solids, Extinction, Correlation techniques, Predictions, Efficiency, Heat, Extraction, Absorption, Temperature, Burning rate, Flame propagation, Dry materials

Subject Categories : Statistics and Probability
      Safety Engineering
      Combustion and Ignition

Distribution Statement : APPROVED FOR PUBLIC RELEASE