Procedure For Measuring Diffuser, Register And Grille Velocities With Diffuser Probe; Typical Diffuser Air Flow Measuring Procedure - Alnor Velometer 6000 Serie Mode D'emploi

Procedure for Measuring Diffuser, Register and Grille
Velocities with Diffuser Probe
To calculate the air volume passing through a diffuser, register or grille
outlet, measure the velocity at the outlet, applying the air flow factor that
is provided by the outlet manufacturer, and use the following equation:
Q = K x V
Where
Q = Volume flow rate
K = Manufacturer's flow factor
V = Average measured velocity
Instructions for positioning the Diffuser Probe at the outlet for measuring
the velocity, as well as an appropriate flow factor, are available from the
outlet manufacturer. Shown below is a typical example:

Typical Diffuser Air Flow Measuring Procedure

To determine the volume of air discharged, a Velometer with a Diffuser
Probe may be used as shown below.
Note that the bottom of the positioning fins on the probe are level with
(and touching) the bottom of the intermediate spinning of the diffuser.
The probe is held vertically. The flow factors shown in the
accompanying table are applied to an average of six velocity readings
taken at equally spaced positions around the periphery of the diffuser.
English Units Metric Units
ft /min m /s
3 3
— —
ft/min m/s
Diffuser Air Flow
Size Factor
10
12
14
17
20
24
32
40
0.42
0.66
0.9
1.3
1.8
2.8
4.9
7.7
11