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Investigation of Fire Impingement on a Horizontal Ceiling.


pdf icon Investigation of Fire Impingement on a Horizontal Ceiling. (3355 K)
You, H. Z.; Faeth, G. M.

NBS GCR 81-304; 83 p. December 1981.

Sponsor:

National Bureau of Standards, Gaithersburg, MD

Available from:

National Technical Information Service
Order number: PB82-165838

Keywords:

ceilings; fire models; fire plumes; heat transfer; radiation; turbulence

Abstract:

The structure and heat transfer properties of fires and fire plumes impinging on a horizontal ceiling were investigated. Profiles of mean velocity, temperature, composition and mixture fraction were measured. Turbulence quantities were also measured in the plume, including longitudinal fluctuations and Reynolds stress. Other measurements were as follows: convective and radiative heat fluxes to the ceiling, radiative heat flux to the surroundings, and flame shape. The measurements were compared with predications of both differential and integral models. A k-epsilon-g differential model was examined for the plume portion of the flow. This model was originally developed for forced combusting flows and while it includes buoyancy affects in the mean equations, the effect of buoyancy on turbulence quantities is ignored. The prediction of radiation was simplified, in order to avoid complications due to the presence of soot, by either neglecting radiative heat losses entirely or by assuming that a fixed fraction, 20%, of the energy released by combustion was lost due to radiation. Integral models were developed for both the plume and ceiling jet portions of the flow. Computational conveniene was emphasized during the construction of these models; therefore, "top-hat" profiles a flow entrainment expression, and a mixing-controlled combustion model are assumed.