Ceiling jets of strong fire plumes

Measurements are presented of maximum excess temperatures in ceiling jets produced by strong, turbulent, steady fire plumes impinging on flat horizontal ceilings. The ratio of free flame height (flame height in the absence of a ceiling) to ceiling height (flame-height ratio) ranged from approximately 0·3 to 3. A common type of correlation of ceiling jet excess temperatures, employing the ceiling height as a normalizing length scale for the observation radius, did not correlate the data well. However, an excellent correlation of the temperature data was achieved for flame-height ratios up to approximately 2, using an expression for the plume radius at the ceiling level as the normalizing length scale. Data at the largest flame-height ratio investigated, 3, did not conform with the other data, attributed to significant heat release in the ceiling jet itself.