10.10.2006
The primary standards for atmospheric air and high-pressure natural gas were compared by means of sonic Venturi nozzles and the method was verified in a comparison with LNE and NIST.
The realization of the units for high-pressure natural gas and atmospheric air could for the first time be compared directly and with low measurement uncertainty. For this purpose, sonic Venturi nozzles were used, whose calibration value can be determined both via a comparison with the primary standards and via flow-theoretical derivations and a geometric measurement as a function of the Reynolds number. This allows both traceability chains to be compared by independently obtained traceability to geometric quantities and gas quality such as pressure, temperature and molar mass. On the international level, the quality of this comparison could be shown by comparison measurements with LNE, France, and NIST, USA. In this comparison, the deviations of the individual partners from the value obtained in flow-theoretical and geometrical measurements were in the order of magnitude of only 0.05%. This lies clearly below the measurement uncertainties of 0.12% to 0.19% indicated by the partners. The results and the flow-theoretical backgrounds were presented to the professional audience on the sixth International Symposium on Fluid Flow Measurement (6th ISFFM) in Mexico.
Contact person:
Bodo Mickan, FB 1.4, AG 1.42, bodo.mickan@ptb.de