Fire-Plume-Generated Ceiling Jet Characteristics and Convective Heat Transfer to Ceiling and Wall Surfaces in a Two-Layer Zone-Type Fire Environment: Uniform Temperature Ceiling and Walls.
Fire-Plume-Generated Ceiling Jet Characteristics and
Convective Heat Transfer to Ceiling and Wall Surfaces in
a Two-Layer Zone-Type Fire Environment: Uniform
Temperature Ceiling and Walls.
(1285 K)
Cooper, L. Y.
NISTIR 4705; 57 p. November 1991.
Fire Science and Technology, Vol. 13, No. 1/2, 1-17,
1993.
Sponsor:
Nuclear Regulatory Commission, Washington, DC
Available from:
National Technical Information Service
Order number: PB92-123074
Keywords:
ceiling jets; building fires; compartment fires;
computer models; fire models; heat transfer;
mathematical models; zone models
Abstract:
It has been determined by Sandia National Laboratories
and the U. S. Nuclear Regulatory Commission that the use
of deterministic, multi-room, zone-type fire modeling
technology could enhance the reliability of their recent
reactor safety risk studies. These studies are confined
to the relatively early detection times of fire
development when fire-driven ceiling jets and
gas-to-ceiling convective heat transfer are expected to
play a particularly important role in room-to-room smoke
spread and in the response of near-ceiling mounted
detection hardware. A parameter of concern in these
risk analyses is the location of the fire within the
space of fire origin. One goal of the analyses is to
determine the significance to risk of this fire-position
parameter. This work presents a model to predict the
instantaneous rate of convective heat transfer from fire
plume gases to the overhead ceiling surface in a room of
fire origin. The room is assumed to be a rectangular
parallelopiped and, at times of interest, ceiling
temperatures are simulated as being uniform. Also
presented is an estimate of the convective heat
transfer, due to ceiling-jet-driven wall flows, to both
the upper and lower portions of the walls. The effect on
the heat transfer of the location of the fire within the
room is taken into account. Finally presented is a
model of the velocity and temperature distributions in
the ceiling jet. The model equations were used to
develop an algorithm and associated modular computer
subroutine to carry out the indicated heat transfer
calculations. The subroutine is written in FORTRAN 77
and called CEILHT. The algorithm and subroutine are
suitable for use in two-layer zone-type compartment fire
model computer codes. The subroutine was tested for a
variety of fire environments involving a 10(7)W fire in
a 8m x 8m x 4m high enclosure. While the calculated
results were plausible, it is important to point out
that CEILHT simulations have not been experimentally
validated.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899