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This differen al pressure compares the sta c pressure in front of the fan inlet ring with the
sta c pressure in the inlet ring of the narrowest point. The differen al pressure between
the sta c pressures is related to the air volume via the energy conserva on rate as per the
graph below. Simply read across from the pressure measurement to the appropriate fan
curve and down to calculate the resultant air volume.
Measured differen al pressure: 1400Pa - Unit: TLL400
Reading from graph: 1.6 = Air Volume: 1.6 m³/s
Differen al pressure
tapping point
Set-up
5
Con nued
Example:
0
250
500
750
1000
1250
1500
1750
2000
2250
2500
2750
3000
3250
3500
3750
4000
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
6
6.5
7
7.5
8
8.5
9
9.5
10
10.5
11
Δpw Diff
er
en"
al Pr
essur
e P
a
TLL350
TLL250
TLL400
TLL450
TLL500
TLL560
TLL630
TLL710
TLL800
TLL250 = 60
TLL350 = 121
TLL400 = 154
TLL450 = 197
TLL500 = 252
TLL560 = 308
TLL630 = 381
TLL710 = 490
TLL800 = 620
k
(nozzle coefficient)
1400
1.6
q Air Volume m³/s
v
This measurement can also be expressed in the following calcula on:
q
V
is the air volume in m³/s
k
is the fan nozzle coefficient
pW is the measured differen al pressure
in Pa
q = (k
v
pw) / 3600
√Δ
Δ
Alterna vely, to calculate a dif feren al pr essure reading from a v olume:
Δ
pw = ((
3600)
)
q
v
×
Example:
Measured differen al pressure: 1400Pa
Unit: TLL400
q
V
= (154 1400) / 3600
q
V
= (154 x 37.417) / 3600
q
V
= 5762 / 3600
q
V
= air volume = 1.6 m³/s
Example:
Required air volume (q
V
) = 1.6 m³/s
Δ
pw = ((1.6 3600) 154)
Δ
pw
²
= (37.4)
Δ
pw = 1399 Pa
×
Fig.
9
Fig.
10
t-line
Extract Units
