CEILING JETS OF STRONG FIRE PLUMES

Measurements are presented of maximum excess temperatures in ceiling j ets produced by strong, turbulent, steady fire plumes impinging on fla t horizontal ceilings. The ratio of free flame height (flame height in the absence of a ceiling) to ceiling height (flame-height ratio) rang ed from approximately 0.3 to 3. A common type of correlation of ceilin g jet excess temperatures, employing the ceiling height as a normalizi ng length scale for the observation radius, did not correlate the data well. However, an excellent correlation of the temperature data was a chieved for flame-height ratios up to approximately 2, using an expres sion for the plume radius at the ceiling level as the normalizing leng th scale. Data at the largest flame-height ratio investigated, 3, did not conform with the other data, attributed to significant heat releas e in the ceiling jet itself.