EN ISO 9300:2005 (edition 2)

Foreword
1 Scope
2 Terms and definitions
  2.1 Pressure measurement
  2.2 Temperature measurement
  2.3 Venturi nozzles
  2.4 Flow
3 Symbols
4 Basic equations
  4.1 State equation
  4.2 Flow-rate under ideal conditions
  4.3 Flow-rate under real conditions
  4.4 Critical mass flux
5 Applications for which the method is suitable
6 Standard critical flow Venturi nozzles (CFVN)
  6.1 General require
  6.2 Design
7 Installation requirements
  7.1 General
  7.2 Upstream pipeline
  7.3 Large upstream space
  7.4 Downstream requirements
  7.5 Pressure measurement
  7.6 Drain holes
  7.7 Temperature measurement
  7.8 Density measurement
  7.9 Calculated density
8 Calculation methods
  8.1 Mass flow-rate
  8.2 Discharge coefficient, C[d']
  8.3 Critical flow function, C[*], and real gas critical
      flow coefficient, C[R]
  8.4 Conversion of measured pressure and temperature to
      stagnation conditions
  8.5 Maximum permissible downstream pressure
9 Uncertainties in the measurement of flow-rate
  9.1 General
  9.2 Practical computation of uncertainty
Annex A (normative) Venturi nozzle discharge coefficients
Annex B (normative) Tables of values for critical flow
                    function C[*] - Various gases
Annex C (normative) Computation of critical mass flux for
                    natural gas mixtures
Annex D (normative) Mass flow correction factor for
                    atmospheric air
Annex E (normative) Computation of critical mass flux for
                    critical flow nozzles with high
                    nozzle throat to upstream pipe diameter
                    ratio, beta > 0,25
Bibliography

ISO 9300:2005 specifies the geometry and method of use (installation in a system and operating conditions) of critical flow Venturi nozzles (CFVN) used to determine the mass flow-rate of a gas flowing through a system. It also gives the information necessary for calculating the flow-rate and its associated uncertainty. It is applicable to Venturi nozzles in which the gas flow accelerates to the critical velocity at the throat (this being equal to the local sonic velocity), and only where there is steady flow of single-phase gases.