Convective Heat Transfer in the Impingement Region of a Buoyant Plume

Fires of hazardous scale generate turbulent plumes within which convective heat transfer to surfaces can be important. Relatively little work has been done on developing reliable convective heat transfer correlations applicable to such large-scale flows. The present study, confined to heat transfer rates within the plume impingement region on a ceiling, achieves plume Reynolds numbers an order of magnitude beyond those of previous work by performing laboratory-scale experiments at elevated ambient pressures. Flow disturbances which normally cause scatter in plume heat transfer data are reduced as a consequence of this technique. It is shown that impingement zone Nusselt number depends on the 0.61 power of plume Reynolds numbers in the range of 10⁴ to 10⁵. This result is between the 1/2 power dependence expected for strain rate control (forced jet impingement) and the 2/3 power expected for buoyancy control of turbulent heat transfer rates.