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Simulating Smoke Movement Through Long Vertical Shafts in Zone-Type Compartment Fire Models.


pdf icon Simulating Smoke Movement Through Long Vertical Shafts in Zone-Type Compartment Fire Models. (1076 K)
Cooper, L. Y.

NISTIR 5526; 30 p. November 1994.

Fire Safety Journal, Vol. 31, No. 2, 85-99, September 1998.

Available from:

National Technical Information Service
Order number: PB95-143152

Keywords:

building fires; compartment fires; computer models; fire models; mathematical models; vents; zone models; smoke movement; elevator shafts

Abstract:

A limitation of traditional zone-type compartment fire modeling concepts is identified; namely, the inadequacy of two-layer quasi-steady-buoyant-plume analyses to simulate the fire-generated environment in room configurations with large height-to-span ratios, e.g., elevator shafts and long, vertical, ventilation shafts and ducts. A possible means of removing this limitation is developed. This involves a method of analysis and associated model equations that can be implemented and used to advance zone-type models. The model equations simulate time-dependent flows in a long, ventilated, vertical shaft/duct with an arbitrary vertical density distribution, including one or more intervals along the shaft/duct length where the vertical distribution of the average cross-section density may be unstably stratified, i.e., density increasing with increasing elevation. The model equations are partially verified by favorable comparisons between solutions and previously published data from unsteady experiments in long vertical tubes involving initially unstable configurations: salt-water over fresh-water and heavy-gas over light-gas. Additional verification of the proposed equation set with cold-air over hot-air systems and with fire-driven smoke flows, both of which involve gas-to-surface heat transfer, is required before this model can be used with confidence in professional practice.