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Calculation of the Flow Through a Horizontal Ceiling/Floor Vent.

Calculation of the Flow Through a Horizontal
Ceiling/Floor Vent.
(941 K)

Cooper, L. Y.

NISTIR 89-4052; 30 p. February 1989.

### Sponsor:

Naval Research Lab., Washington, DC

### Available from:

National Technical Information Service

Order number: PB89-189252

### Keywords:

vents; algorithms; building fires; compartment fires;
computer models; computer programs; fire models;
pressure differential; pressure effects; zone models;
ceiling vents; oxygen concentration

### Abstract:

*
Calculation of the flow through a horizontal vent
located in a ceiling or floor of a multi-room
compartment is considered. It is assumed that the
environments of the two, vent-connected spaces near the
elevation of the vent are of arbitrary relative buoyancy
and cross-vent pressure difference. An anomaly of the
standard vent flow model is discussed. The problem
occurs in practical vent configurations of unstable
hydrostatic equilibrium, where, for example, one gas
overlays a relatively less-dense gas. In such
configurations the cross-vent flow is not
uni-directional. Previously published experimental data
on a variety of related flow configurations are used to
develop a general flow model which does not suffer from
the standard model anomaly. The model developed leads
to a uniformly valid algorithm, called VENTCL, for
horizontal vent flow calcualtions suitable for general
use in zone-type compartment fire models. Based on an
assumption of total consumption of net oxygen flow rate,
the algorithm is used in an example application where
steady-state rate-of-burning in a ceiling-vented room is
estimated as a function of room temperature, vent area,
and oxygen concentration.
*