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BS EN ISO 9300:2022

BS EN ISO 9300:2022

$215.11

Measurement of gas flow by means of critical flow nozzles

Published By Publication Date Number of Pages
BSI 2022 132
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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
2 undefined
7 Foreword
9 1 Scope
2 Normative references
3 Terms and definitions
3.1 Pressure
10 3.2 Temperature
3.3 Nozzle
11 3.4 Flow
12 3.5 Flow rate
13 3.6 Gas
14 4 Symbols and abbreviations
17 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
18 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
19 5.4.3 Theoretical mass flow rate of real gas
5.5 Mass flow rate
6 General requirements
20 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
21 8.1.3 Contraction and throat
8.1.4 Diffuser
22 8.2 Requirements for each standard type of CFN
23 8.2.1 Toroidal-throat CFN
8.2.2 Toroidal-throat CFN
24 8.2.3 Cylindrical-throat CFN
26 9 Installation requirements
9.1 General requirements for both the standard configurations
9.1.1 Standard configurations
9.1.2 Upstream pressure tapping
27 9.1.3 Downstream pressure tapping
9.1.4 Temperature measurement
28 9.1.5 Density measurement
9.1.6 Drain hole
9.1.7 Downstream condition
29 9.2 Pipe configuration
9.2.1 General
9.2.2 Upstream pipe
30 9.2.3 Pressure measurement
9.2.4 Temperature measurement
31 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
32 10.3 Calculation of discharge coefficient, Cd
33 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
34 11 Estimation of critical back-pressure ratio
11.1 For a traditional diffuser at Reynolds numbers higher than 2 Ɨ 105
35 11.2 For any diffuser at low Reynolds numbers
36 11.3 For CFNs without diffuser or with very short diffuser
12 Uncertainties in the measurement of flow rate
12.1 General
37 12.2 Practical computation of uncertainty
38 12.3 Correlated uncertainty components
40 Annex A (informative) Discharge coefficient values
42 Annex B (informative) Critical flow function
B.1 General
B.2 Critical flow function of perfect gas
43 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
44 B.4.4 When accurate values are necessary
B.5 Gases with significant vibrational relaxation effect
45 Annex C (informative) Critical flow function values ā€” Pure gases and air
C.1 General
46 C.2 Nitrogen
48 C.3 Argon
50 C.4 Dry air with carbon dioxide (CIPM 2007 composition+CO2/0,04 %)
52 C.5 Dry air without carbon dioxide (CIPM 2007 composition /no CO2)
54 C.6 Humidity correction for air of a typical composition
55 C.7 Methane
60 C.8 Carbon dioxide
64 C.9 Oxygen
67 C.10 Steam (single-phase gas)
70 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
74 Annex E (informative) Diameter correction method
E.1 General
E.2 Procedures
E.2.1 Overview
75 E.2.2 Visual procedure
E.2.3 Coarse procedure
E.2.4 Fine procedure
79 Annex F (informative) Adjustment of discharge coefficient curve on a data set
F.1 General
80 F.2 Fitting procedure
87 Annex G (informative) Discharge coefficient
G.1 General
G.2 Flow field distribution along a diameter at the critical point
88 G.3 Reynolds number dependence of discharge coefficient
89 G.4 Boundary layer transition
90 G.5 Discharge coefficient curves
91 G.6 Obtaining discharge coefficient curve
92 Annex H (informative) Critical back pressure ratio
H.1 General
93 H.2 Theoretical critical back-pressure ratio
94 H.3 Examples of the typical choking patterns with the PUP
98 H.4 Choking test
H.4.1 Against a reference CFN
99 H.4.2 Against a reference flow meter
100 Annex I (informative) Viscosity values ā€“ Pure gases and air
I.1 General
102 I.2 Nitrogen
103 I.3 Argon
104 I.4 Dry air
106 I.5 Methane
110 I.6 Carbon dioxide
113 I.7 Oxygen
114 I.8 Steam (single-phase gas)
116 Annex J (informative) Supplement
J.1 General
J.2 Static pressure
J.3 Static temperature
117 J.4 Stagnation temperature
J.5 Recovery temperature
J.6 Isentropic flow
118 J.7 Critical flow
J.8 Choke
J.9 Critical point
J.10 Critical velocity
119 J.11 Volume flow rate
J.12 Reynolds number
J.13 Compressibility factor
J.14 Volume flow rate through conduit
120 J.15 Maximum mass flow rate
J.16 Detachable diffuser
121 J.17 Downstream pressure
J.18 Temperature correction of throat area
122 J.19 REFPROP
J.20 Critical flow functions of air
123 J.21 Critical flow functions of air
124 Bibliography

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BS EN ISO 9300:2022
$215.11