The Buoyant Plume-Driven Adiabatic Ceiling Temperature Revisited

In previous works, convective heat transfer from buoyant plume-driven ceiling jets to unconfined ceilings has been estimated using a formula for the temperature distribution below an adiabatic ceiling T_ad obtained from experimental data in the range 0 ≤ r/H < 0.7 (r is the radial distance from the plume and H is the plume source-to-ceiling distance). The present study re-evaluates these data, and develops an independent estimate for T_ad. The analysis takes account of the effect of ceiling surface reradiation, and use is made of the previously established similarity between plume/ceiling- and jet/wall-driven heat transfer phenomena. The latter similarity is the basis of a correlation of recently reported free jet-wall jet “recovery temperature” data into a normalized T_ad distribution. All of the analysis leads to new formulae for estimating the convective heat transfer to ceilings during enclosure fires. These new results confirm previous formulae, and extend them into the larger range 0 ≤ r/H ≤ 2.2.