25 October 2004
Plenum Design. Use perforated plate to cover as much of the ceiling (or
wall opposite the exhaust hood(s)) as practical. The diameter of the perforation should
be between 6.3 mm and 9.5 mm (1/4 in and 3/8 in). Perforated plenums work best
when ceiling height is less than 4.58 m (15 ft). Use either of the following two choices
for replacement air plenum design:
a. Design for 5.1 m/s (1,000 fpm) replacement air velocity through the
open area of the perforated plate if perforated duct is used inside the
plenum as shown in Figure 2-3.
b. Design for 10.2 m/s (2,000 fpm) replacement air velocity through the
open area of the perforated plate if the plenum is served with ducts using
diffusers, grills or registers as shown in Figure 2-4.
Figure 2-3. Plenum design with perforated duct.