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Algorithm for Estimating the Plume Centerline Temperature and Ceiling Jet Temperature in the Presence of a Hot Upper Layer.


pdf icon Algorithm for Estimating the Plume Centerline Temperature and Ceiling Jet Temperature in the Presence of a Hot Upper Layer. (685 K)
Davis, W. D.; Notarianni, K. A.; Tapper, P. Z.

NISTIR 6178; 27 p. June 1998.

Available from:

National Technical Information Service (NTIS), Technology Administration, U.S. Department of Commerce, Springfield, VA 22161.
Telephone: 1-800-553-6847 or 703-605-6000;
Fax: 703-605-6900.
Website: http://www.ntis.gov
Order number: PB98-146152

Keywords:

aircraft hangars; ceiling jets; fire models; fire plumes; pool fires; zone models; sprinkler activation

Abstract:

The analysis of recent experiments (NIST TN 1423) using JP-5 and JP-8 pool fires performed in 15 m and 22 m high hangars suggest that plume centerline temperature correlations found in the computer fire model FPETool under predict the ceiling temperature for large fires. The analysis was based on the results of thirty-three fire tests which had heat release rates ranging from 100 kW to 33 MW and ambient temperatures ranging from 8 deg C to 31 deg C. The ceiling jet correlation also requries modification since a comparison of predicted sprinkler activation using FPETool to measured sprinkler activation met with only limited success. It is shown that using Evans' virtual source method coupled with a radiative fraction correlation that depends on pool diameter provides plume centerline temperature predictions that agree with experiment. A modified version of Alpert's ceiling jet correlation is presented to account for changes in r/H dependence as the upper layer develops. When an upper layer does not form, both Alpert's and Heskestad's correlations provide good agreement with the measure ceiling temperatures.