MIL-HDBK-1011/2
APPENDIX C (continued)
Similarly for the large-scale model:
delta Pnl = (1/2 p Unl2)Cpn
EQUATION:
(23)
The total pressure coefficient measured on the large- scale model is assumed
to equal that on the small-scale model, and that on the full-scale building.
The interior wind velocities on the large-scale model Unl have been measured,
as well as the pressure differentials, WPns and WPnl. Dividing one equation
by the other leads to:
Uns = (delta Pns / delta Pnl) 1/2 Unl
EQUATION:
(24)
Interior air velocity ratios (the final answers) are then obtained as:
EQUATION:
Cvn = Uns /Uref
(25)
where
Uns
is the interior air velocity of the small-scale model for
the direction n, and
Cvn
is the ratio of interior air velocity to a reference mean
free-stream velocity.
1.3.4.3
Procedure for High-Rise Buildings. The second procedure is
particularly appropriate for the determination of interior airflow rates in
highrise buildings composed of typical floors, or typical living units. This
method may become cumbersome when many different interior space models are
required for a single building. An alternative method has been suggested by
Vickery (1981) to streamline the determination of airflow rates in highrise
buildingw with many different interior spaces.
Starting with mean pressure distributions obtained from a
small-scale model, interior airflow rates are computed analytically. Each
interior space is in essence a closed conduit. Basic laws of closed-conduit
flow can be used to determine airflow rates through each space, given the
pressure differential across the conduit, and the pressure loss coefficients
through halls, through openings, and around corners. A number of such computer
models have been developed. Refer to paras. 2.3 to 2.3.3 of this Appendix.
Use of Wind Tunnel Air Flow Rates. The airflow rates obtained from
1.3.5
wind tunnel tests alone do not determine whether or not a building can be
naturally ventilated. Interior airflow rates must be combined with other
information, particularly probability distributions of directional reference
velocities, temperature, humidity, and solar radiation, in order to determine
the appropriateness of naturally ventilating a space. See Appendices B and C,
para 1.1 for the minimum climatic considerations.
1.4
Field Modeling. Researchers at the Florida Solar Energy Center
(FSEC) have proposed testing small scale models outdoors in the natural wind
to observe airflow through naturally ventilated buildings. Their limited
testing (Chandra et al., 1983) shows excellent correlation between a one-story
building and a model tested in this manner on the actual building site.
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