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196 Volumetric flow rate
Section 6: Meter operation Reference, Installation, and Operations Manual
June 2013 3-9000-743 Rev S
6.1.9 Volumetric flow rate
The Daniel Mark III Ultrasonic Gas Flow Meter meter provides three volumetric flow rate values:
raw, (expansion-corrected and/or profile-effect corrected) flow-condition, and base-condition.
Note that a positive volumetric flow rate indicates flow in the forward direction whereas a
negative volumetric flow rate indicates flow in the reverse direction.
Raw volumetric flow rate
The “raw” volumetric flow rate is calculated from the average gas flow velocity (wet-calibration
gas flow velocity) as shown in Equation 6-12.
Equation 6-12 Raw volumetric flow rate
where
Flow-condition volumetric flow rate
The flow-condition volumetric flow rate is the result of applying expansion correction and flow-
profile correction to the raw volumetric flow rate as shown in Equation 6-13 subject to the low-
flow cut-off. If the resulting value is below the low-flow cut-off value, it is set to zero. The low-flow
cut-off volumetric flow rate (CutRate) is the specified low-flow velocity threshold (ZeroCut)
converted to a volumetric flow rate.
=
“raw” volumetric flow rate (m
3
/h) (QMeter)
=
wet-calibration gas flow velocity (m/s) (AvgFlow)
=
geometric constant, pi (dimensionless) (3.14159...)
=
pipe inside diameter (m) (PipeDiam)
Q
Raw
V
WetCal
πD
in
2
4
-----------
× 3600× shr⁄=
Q
Raw
V
WetCal
π
D
in