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