80
3 Flow Rates and Pressure Measurements
The distance (L m ) from the emission to the measurement point is determined by
means of Eq. 3.10:
L m =
44 A
O
√ λ
(3.10)
where
• A: Area of the gallery (m
2 ),
• O: Perimeter of the gallery (m), and
• λ: Coefficient of friction.
The start time for measurements (t m ) corresponds to Eq. 3.11:
t m =
2.6L m
v
(3.11)
where
v is the air speed in the gallery (m s
−1 ).
The concentration of the tracer gas can be calculated as:
c =
q
Q + q
Since:
q Q
Therefore, the rate of air flowing through the gallery can be approximated as
(Eq. 3.12):
Q =
q
c
(3.12)
A variant of the previous method is applied to measuring leaks in airlocks.
Figure 3.15 illustrates the methodology (d’Albrand 1976).
Using the preceding expression, c 1 , c 2 and c 3 are assigned as the concentrations
at points 1, 2 and 3, respectively. The flow rate at point 1 in Fig. 3.15 will thus be:
Q 1 =
q
c 1
At point 2:
Q 2 =
q
q
1
c 2
−
1
c 1
3 Flow Rates and Pressure Measurements
The distance (L m ) from the emission to the measurement point is determined by
means of Eq. 3.10:
L m =
44 A
O
√ λ
(3.10)
where
• A: Area of the gallery (m
2 ),
• O: Perimeter of the gallery (m), and
• λ: Coefficient of friction.
The start time for measurements (t m ) corresponds to Eq. 3.11:
t m =
2.6L m
v
(3.11)
where
v is the air speed in the gallery (m s
−1 ).
The concentration of the tracer gas can be calculated as:
c =
q
Q + q
Since:
q Q
Therefore, the rate of air flowing through the gallery can be approximated as
(Eq. 3.12):
Q =
q
c
(3.12)
A variant of the previous method is applied to measuring leaks in airlocks.
Figure 3.15 illustrates the methodology (d’Albrand 1976).
Using the preceding expression, c 1 , c 2 and c 3 are assigned as the concentrations
at points 1, 2 and 3, respectively. The flow rate at point 1 in Fig. 3.15 will thus be:
Q 1 =
q
c 1
At point 2:
Q 2 =
q
q
1
c 2
−
1
c 1