Brochure

92 Series, H and V Series Alternate Sizing Graph (Page 7-16)
Method of Determining
Alternate Grille Sizes
Extensive tests indicate that by varying dimensions of
a grille there is no appreciable effect on the air throw,
provided the same area is maintained. To change the
dimensions of a grille, place a straight edge across
the width and height scales on dimensions as selected
from charts. Place a pointer at the crossing point on
the turning line and rotate the straight edge around this
point until it crosses width and height scale at dimen
-
sions desired.
NOTE: Grille sizes determined from this chart are the
nominal or duct dimensions.
General Conclusions on
Air Distribution
1. The throw from a straight flow grille varies
with the square root of the daylight area
of the grille and with the face velocity.
2. The ratio of the width to the height
(aspect ratio) of a grille has no
appreciable effect on the distance of air
throw.
3. If the air streams from a grille are
converged, it results only in cutting down
the effective area of the grille.
4. Breaking the air stream up into jets has
no effect on either the rate of mixing or
the flow.
5. Fanning out the air stream shortens
the throw. The amount depends on the
degree of deflection.
6. The drop, for a given throw, of an air
stream below room temperature varies
about inversely as the face velocity and
directly as the temperature differential.
7. For any given velocity neither the aspect
ratio of the grille, breaking the air stream
up into jets, nor impinging the air
streams together equally have any effect
on the drop of the air stream.
Basic formula determined through elaborate test work and
used in the compilation of the charts contained herein
are:
(1) T = Kt x CFM
√A x Vt
(2) CFM = V x Ak
(3) CFM = An x Vn
Where: T = Throw (feet)
Kt = Throw factor determined by test
CFM = Air flow rate (cubic feet per minute)
A = Core Area, sq. ft.
Vt = Terminal Velocity
Vk = Face Velocity (Feet per minute)
Ak = Effective area
Where: Vn = Neck Velocity in feet per minute
An = Neck area in square feet
Listed Size 6 8 10 12
An (Round) .20 .35 .55 .79
An (Square) .25 .44 .69 1.00
Listed Size 14 16 18 20
An (Round) 1.10 1.40 1.80 2.20
An (Square) 1.40 1.80 2.30 2.80
Air Velocity (FPM) and Velocity Pressure (Pv, inches
water column) relationships:
Vel = 4005 √Pv
Pv = Vel
2
4005
CFM = BTUH
∆T x 1.085
( )
Grille Width
in Inches
Turning
Line
Grille Height
in Inches
Engineering Data
Engineering Data
134 Recommended Noise Criteria and Face Velocity Ranges are on page 75