Improving the Estimates of Methodological Errors when Reproducing Volumetric Air Flow Rates Using a Critical Nozzle as a Standard.

In order to improve the metrological characteristics of a standard nozzle under actual operating conditions, an improved model of a steady-state gas flow in the varying-cross-section channels was used to refi ne the estimates of two methodological errors when reproducing a volumetric flow rate of gas. The first methodological error is caused by the selection of a gas flow model, accounting for the initial kinetic energy of the flow at the nozzle inlet, and the second – by the variation in humidity of the process air. It is shown that these methodological errors should be considered when operating standard volumetric air flow rate measuring devices, containing critical nozzles. [ABSTRACT FROM AUTHOR]