24
Average sound velocity
Section 4: Flow measurement
3410 Series Gas Ultrasonic Meters Operations Manual
January 2018
3-9000-777 Rev E
For all other port angles,
where
Note that a positive chord gas velocity indicates flow in the forward direction whereas a
negative chord gas velocity indicates flow in the reverse direction.
4.4.1
Average sound velocity
The Average Sound Velocity is calculated as the average of the active chord sound velocity
measurements as shown in the equation below:
Equation 4-3 Average sound velocity
where
4.4.2
Optional AGA10 sound velocity calculation and comparison
The Daniel 3410 Series Gas Ultrasonic Flow Meter offers an option to calculate the sound
velocity (using AGA10 equations and gas property data) and compare the result to the meter-
measured sound velocity on an hourly basis. This feature is enabled via the AGA10Key (
see
Section 3.1.3
). The gas property data required for using this feature can be specified via data
points or optionally read from a Daniel GC (
see Section 5.11
). The AGA8 Detailed Method must
be selected (via the
HCH_Method
data point,
see Section 5.11
) in order for the AGA10
calculations to be performed (as the AGA10 calculations require AGA8 Detailed method
calculation intermediate results).
=
chord average gas velocity (m/s) (FlowVelA ... FlowVelD)
=
chord average sound velocity (m/s) (SndVelA ... SndVelD)
=
chord “L” dimension (m) (LA ... LD)
=
chord “X” dimension (m) (XA ... XD)
=
chord average transit time in the upstream direction (s)
(MeanTmA1 ... MeanTmD1)
=
chord average transit time in the downstream direction (s)
(MeanTmA2 ... MeanTmD2)
=
average sound velocity (m/s) (
AvgSndVel
)
=
chord average sound velocity (m/s) (
SndVelA
...
SndVelD
)
=
number of active chords
PortAngleFactor
1
=
Vchord
Cchord
Lchord
Xchord
t1
t
2
CAvg
Σ
ActiveChords
Cchord
•
NumActiveChords
----------------------------------------------------------------
=
CAvg
Cchord
NumActiveChords
