Calculating Flows Through Vertical Vents in Zone Fire Models Under Conditions of Arbitrary Cross-Vent Pressure Difference.
Calculating Flows Through Vertical Vents in Zone Fire
Models Under Conditions of Arbitrary Cross-Vent Pressure
Difference.
(759 K)
Cooper, L. Y.
NBSIR 88-3732; 16 p. May 1988.
Available from:
National Technical Information Service
Order number: PB89-148126
Keywords:
fire models; building fires; compartment fires; computer
models; computer programs; algorithms; pressure
differential; pressure effects; pressure vessels; zone
models
Abstract:
In typical compartment fire scenarios, ratios of
cross-vent absolute pressures are close to 1. When such
is the case, algorithms are available to predict the
resulting cross-vent room-to-room flows. There are,
however, important situations where this pressure
condition does not prevail, for example, in fire
scenarios involving relatively small penetrations in
otherwise hermetically-sealed compartments of fire
origin. It is important for a versatile compartment
fire model have a capability of predicting vent flows
for the entire range of possible cross-vent pressure
conditions. This paper develops a unified analytic
description for flows through vertical vents between
pairs of two-layer room fire environments under
conditions of arbitrary cross-vent pressure difference.
The analysis, which takes advantage of generally useful
modeling approximations, leads to a concise result which
is not significantly more complicated than the result
for simple, low-pressure-difference cases.
