IMPROVEMENT OF THERMODYNAMIC CALCULATIONS USED FOR THE FLOW RATE OF SONIC NOZZLES |
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| J. P. Vallet, C. Windenberger, F. Vulovic, R. Bouard |
- Abstract:
- Nozzles operating under sonic conditions are already used widely as reference flowmeters in many countries to measure gas flow rate under pressure. These Nozzles are calibrated, in each of the countries concerned, on approved primary test rigs. The techniques used in these countries today are the fruit of R&D carried out on nozzles for more than twenty years. The outcome has been standard ISO 9300, published in 1990, on the technique for measuring gas flowrates using a sonic nozzle.
In the past years, it was decided to revise the ISO 9300 in order to improve the values of the thermodynamic coefficients used to calculate the mass flow rate through the sonic nozzles.
The paper describes the results of the comparison on the thermodynamic calculations used by the participants to establish the critical mass flow rate through a sonic nozzle. It was initially conducted in line with the activities of EUROMET, a grouping of European flow metering laboratories which were subsequently joined by NOVA, CEESI, and NIST.
The comparison was more specifically made between the methods used by those laboratories to calculate the critical flow function C*. The calculation methods considered were the ISO 9300 standardized equations for dry air and natural gaz, the different versions of the AGA8 method, as well as several other methods developed by the laboratories, some of them based on the free energy equations.
The 1992 version of the AGA8 calculation method appreciably improves the calculation uncertainty of the critical flow coefficient C* for natural gas. The most recent thermodynamic values obtained for dry air using the NEL / Panasati method is more reliable than the method developed on the basis of the Johnson data (basis in ISO 9300 for air).
From this study, the most accurate calculation methods are selected in order to re calculate the results obtained from sonic nozzle international intercomparisons and thus to improve significantly the accuracy of the experimental discharge coefficient equation obtained from all calibration results.
All these results will be used for the revision of ISO 9300. - Download:
- IMEKO-TC9-2000-061.pdf
- DOI:
- -
- Event details
- IMEKO TC:
- TC9
- Event name:
- FLOMEKO 2000
- Title:
- 10th Conference on Flow Measurement
- Place:
- Salvador, Bahia, BRAZIL
- Time:
- 04 June 2000 - 08 June 2000