C125 – Ulatrasonic Meter – Flowrate Calculation
Description
This calculates the flowrate, applying corrections for the elastic distortion of the ultrasonic meter spool due pressure and thermal expansion.
References
DanielTM Ultrasonic Gas Flow Meters with Mark III Electronics – Reference, Installation, and Operations Manual
Kelton calculation reference C125
FLOCALC calculation reference F048
KIMS calculation reference K109
Kelton calculation C244 – Calibration Correction
Options
Flow velocity
- User Entered
- Calculated
Select based on whether flow velocity is an unknown.
Juniorsonic correction
- Profile-effect correction
Check box if profile-effect correction is needed. This should only be applied to Juniorsonic meters.
Calibration Correction
- None
- Before spool correction
- After spool correction
This option is used to specify whether there is a linearization applied to the flow rate. If linearization is applied to the raw volume flow rate then select before spool correction, if it is done after correction factors have been applied select after spool correction. The calibration correction is carried out according to C244 – Calibration Correction.
Calculation
Uncorrected volume flow rate
The uncorrected volume flow rate is calculated by:
| Where | ||
|---|---|---|
| v | = | Flow velocity |
| D | = | Internal diameter |
Observed volume flow rate
The observed volume flow rate is calculated by:
| Where | ||
|---|---|---|
| v | = | Flow velocity |
| MF | = | Meter Factor |
| Cfac | = | C-factor |
| D | = | Internal diameter |
| Ctsm | = | Temperature correction factor |
| Cpsm | = | Pressure correction factor |
Temperature correction factor
The temperature correction factor is calculated by:
| Where | ||
|---|---|---|
| TC | = | Temperature coefficient |
| t | = | Temperature |
| tcal | = | Calibration temperature |
Pressure correction factor
The pressure correction factor is calculated by:
| Where | ||
|---|---|---|
| β | = | Strain per unit stress |
| P | = | Pressure |
| Pcal | = | Calibration pressure |
| E | = | Young’s modulus |
| ν | = | Poisson’s ratio (note this is set to 0.3) |
| Dex | = | External diameter |
| Din | = | internal diameter |
Profile-effect correction
The profile-effect correction factor is for Juniorsonic meters and is calculated as follows:
| Where | ||
|---|---|---|
| Din | = | internal diameter |
| Re | = | Reynolds number |
| Sro | = | Spool wall roughness |