3410 Series Gas Ultrasonic Meters Operations Manual Section 4: Flow measurement
3-9000-777 Rev E January 2018
Volumetric flow rate 29
4.5 Volumetric flow rate
The Daniel 3410 Series Gas Ultrasonic 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.
4.5.1 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 4-8.
Equation 4-8 Raw volumetric flow rate
where
4.5.2 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 4-9 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.
Equation 4-9 Flow-condition volumetric flow rate
where
= “raw” volumetric flow rate (m3/h) (QMeter)
= wet-calibration gas flow velocity (m/s) (AvgFlow)
= geometric constant, pi (dimensionless) (3.14159...)
= pipe inside diameter (m) (PipeDiam)
=
flow-condition volumetric flow rate (m
3
/h) (QFlow)
=
“raw” volumetric flow rate (m
3
/h) (QMeter)
= expansion correction factor due to pressure (dimensionless)
(ExpCorrPressure) calculated as shown in
Equation 4-10
= expansion correction factor due to temperature (dimensionless)
(ExpCorrTemperature) calculated as shown in Equation 4-11
= profile-effect correction factor (CorrectionFactor) calculated as
shown in
Equation 4-13
Q
Raw
V
WetCal
πD
2
4
-----------
3600 sh⁄()⋅⋅=
Q
Flow
Q
Raw
()ExpCorr
P
()ExpCorr
T
()CorrFctr()=
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