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
QRaw VWetCal
π
D
2
4
-----------
3600
s h
⁄
(
)
⋅
⋅
=
QRaw
VWetCal
π
D
QFlow
QRaw
(
)
ExpCorrP
(
)
ExpCorrT
(
)
CorrFctr
(
)
=
QFlow
QRaw
ExpCorrP
ExpCorrT
CorrFctr
