BS EN ISO 9300:2022 – TC
$280.87
Tracked Changes. Measurement of gas flow by means of critical flow nozzles
| Published By | Publication Date | Number of Pages |
| BSI | 2022 | 296 |
This document specifies the geometry and method of use (installation in a system and operating conditions) of critical flow nozzles (CFNs) used to determine the mass flow rate of a gas flowing through a system basically without the need to calibrate the CFN. It also gives the information necessary for calculating the flow rate and its associated uncertainty. This document is applicable to nozzles in which the gas flow accelerates to the critical velocity at the minimum flowing section, and only where there is steady flow of single-phase gas. When the critical velocity is attained in the nozzle, the mass flow rate of the gas flowing through the nozzle is the maximum possible for the existing inlet condition, while the CFN can only be used within specified limits, e.g. the CFN throat to inlet diameter ratio and Reynolds number. This document deals with the toroidal- and cylindrical-throat CFNs for which direct calibration experiments have been made in sufficient number to enable the resulting coefficients to be used with certain predictable limits of uncertainty.
PDF Catalog
| PDF Pages | PDF Title |
|---|---|
| 1 | 30460113 |
| 165 | A-30414574 |
| 166 | undefined |
| 171 | Foreword |
| 173 | 1 Scope 2 Normative references 3 Terms and definitions 3.1 Pressure |
| 174 | 3.2 Temperature 3.3 Nozzle |
| 175 | 3.4 Flow |
| 176 | 3.5 Flow rate |
| 177 | 3.6 Gas |
| 178 | 4 Symbols and abbreviations |
| 181 | 5 Basic equations 5.1 Gas behaviour 5.1.1 Isentropic process 5.1.2 State equation 5.2 Isentropic flow of a perfect gas 5.2.1 Flowing area 5.2.2 Static pressure |
| 182 | 5.2.3 Static temperature 5.3 Theoretical variables at the critical point 5.3.1 General 5.3.2 Critical pressure 5.3.3 Critical temperature 5.3.4 Critical density 5.3.5 Critical velocity 5.4 Theoretical mass flow rates 5.4.1 General 5.4.2 Theoretical mass flow rate of a perfect gas |
| 183 | 5.4.3 Theoretical mass flow rate of real gas 5.5 Mass flow rate 6 General requirements |
| 184 | 7 Applications for which the method is suitable 8 CFN 8.1 General requirements for both the standard CFN types 8.1.1 General 8.1.2 Materials |
| 185 | 8.1.3 Contraction and throat 8.1.4 Diffuser |
| 186 | 8.2 Requirements for each standard type of CFN |
| 187 | 8.2.1 Toroidal-throat CFN 8.2.2 Toroidal-throat CFN |
| 188 | 8.2.3 Cylindrical-throat CFN |
| 190 | 9 Installation requirements 9.1 General requirements for both the standard configurations 9.1.1 Standard configurations 9.1.2 Upstream pressure tapping |
| 191 | 9.1.3 Downstream pressure tapping 9.1.4 Temperature measurement |
| 192 | 9.1.5 Density measurement 9.1.6 Drain hole 9.1.7 Downstream condition |
| 193 | 9.2 Pipe configuration 9.2.1 General 9.2.2 Upstream pipe |
| 194 | 9.2.3 Pressure measurement 9.2.4 Temperature measurement |
| 195 | 9.3 Chamber configuration 9.3.1 General 9.3.2 Upstream chamber 9.3.3 Pressure measurement 9.3.4 Temperature measurement 9.3.5 Back-pressure ratio 10 Calculations 10.1 General 10.2 Calculation of mass flow rate, qm |
| 196 | 10.3 Calculation of discharge coefficient, Cd |
| 197 | 10.4 Calculation of critical flow function, C* or C*D 10.5 Conversion of measured pressure into stagnation pressure 10.6 Conversion of measured temperature into stagnation temperature 10.7 Calculation of viscosity |
| 198 | 11 Estimation of critical back-pressure ratio 11.1 For a traditional diffuser at Reynolds numbers higher than 2 × 105 |
| 199 | 11.2 For any diffuser at low Reynolds numbers |
| 200 | 11.3 For CFNs without diffuser or with very short diffuser 12 Uncertainties in the measurement of flow rate 12.1 General |
| 201 | 12.2 Practical computation of uncertainty |
| 202 | 12.3 Correlated uncertainty components |
| 204 | Annex A (informative) Discharge coefficient values |
| 206 | Annex B (informative) Critical flow function B.1 General B.2 Critical flow function of perfect gas |
| 207 | B.3 Critical flow function of real gas B.4 Critical flow function to be used when CFN is flow calibrated B.4.1 General B.4.2 Using in the same gas at the same stagnation condition B.4.3 Using in the same gas at the same range of stagnation condition |
| 208 | B.4.4 When accurate values are necessary B.5 Gases with significant vibrational relaxation effect |
| 209 | Annex C (informative) Critical flow function values — Pure gases and air C.1 General |
| 210 | C.2 Nitrogen |
| 212 | C.3 Argon |
| 214 | C.4 Dry air with carbon dioxide (CIPM 2007 composition+CO2/0,04 %) |
| 216 | C.5 Dry air without carbon dioxide (CIPM 2007 composition /no CO2) |
| 218 | C.6 Humidity correction for air of a typical composition |
| 219 | C.7 Methane |
| 224 | C.8 Carbon dioxide |
| 228 | C.9 Oxygen |
| 231 | C.10 Steam (single-phase gas) |
| 234 | Annex D (informative) Computation of critical mass flux for critical flow nozzles with high nozzle throat to upstream pipe diameter ratio, ( ( 0,25 D.1 General D.2 Correction factors |
| 238 | Annex E (informative) Diameter correction method E.1 General E.2 Procedures E.2.1 Overview |
| 239 | E.2.2 Visual procedure E.2.3 Coarse procedure E.2.4 Fine procedure |
| 243 | Annex F (informative) Adjustment of discharge coefficient curve on a data set F.1 General |
| 244 | F.2 Fitting procedure |
| 251 | Annex G (informative) Discharge coefficient G.1 General G.2 Flow field distribution along a diameter at the critical point |
| 252 | G.3 Reynolds number dependence of discharge coefficient |
| 253 | G.4 Boundary layer transition |
| 254 | G.5 Discharge coefficient curves |
| 255 | G.6 Obtaining discharge coefficient curve |
| 256 | Annex H (informative) Critical back pressure ratio H.1 General |
| 257 | H.2 Theoretical critical back-pressure ratio |
| 258 | H.3 Examples of the typical choking patterns with the PUP |
| 262 | H.4 Choking test H.4.1 Against a reference CFN |
| 263 | H.4.2 Against a reference flow meter |
| 264 | Annex I (informative) Viscosity values – Pure gases and air I.1 General |
| 266 | I.2 Nitrogen |
| 267 | I.3 Argon |
| 268 | I.4 Dry air |
| 270 | I.5 Methane |
| 274 | I.6 Carbon dioxide |
| 277 | I.7 Oxygen |
| 278 | I.8 Steam (single-phase gas) |
| 280 | Annex J (informative) Supplement J.1 General J.2 Static pressure J.3 Static temperature |
| 281 | J.4 Stagnation temperature J.5 Recovery temperature J.6 Isentropic flow |
| 282 | J.7 Critical flow J.8 Choke J.9 Critical point J.10 Critical velocity |
| 283 | J.11 Volume flow rate J.12 Reynolds number J.13 Compressibility factor J.14 Volume flow rate through conduit |
| 284 | J.15 Maximum mass flow rate J.16 Detachable diffuser |
| 285 | J.17 Downstream pressure J.18 Temperature correction of throat area |
| 286 | J.19 REFPROP J.20 Critical flow functions of air |
| 287 | J.21 Critical flow functions of air |
| 288 | Bibliography |
