BS ISO 3354-2008 Measurement of clean water flow in closed conduits - Velocity-area method using current-meters in full conduits and under regular flow conditions《封闭管道中清洁水流量的测量 在全部.pdf

1、BS ISO 3354:2008ICS 17.120.10NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBRITISH STANDARDMeasurement of cleanwater flow in closedconduits Velocity-area method usingcurrent-meters in fullconduits and underregular flow conditionsThis British Standardwas published under theaut

2、hority of the StandardsPolicy and StrategyCommittee on 31 August2008 BSI 2008ISBN 978 0 580 62864 1Amendments/corrigenda issued since publicationDate CommentsBS ISO 3354:2008National forewordThis British Standard is the UK implementation of ISO 3354:2008. Itsupersedes BS 1042-2.4:1989 which is withd

3、rawn.The UK participation in its preparation was entrusted to TechnicalCommittee CPI/30/5, Velocity based methods.A list of organizations represented on this committee can be obtained onrequest to its secretary.This publication does not purport to include all the necessary provisionsof a contract. U

4、sers are responsible for its correct application.Compliance with a British Standard cannot confer immunityfrom legal obligations.BS ISO 3354:2008Reference numberISO 3354:2008(E)ISO 2008INTERNATIONAL STANDARD ISO3354Third edition2008-07-15Measurement of clean water flow in closed conduits Velocity-ar

5、ea method using current-meters in full conduits and under regular flow conditions Mesurage de dbit deau propre dans les conduites fermes Mthode dexploration du champ des vitesses dans les conduites en charge et dans le cas dun coulement rgulier, au moyen de moulinetsBS ISO 3354:2008ISO 3354:2008(E)

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9、GHT PROTECTED DOCUMENT ISO 2008 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below o

10、r ISOs member body in the country of the requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ii ISO 2008 All rights reservedBS ISO 3354:2008ISO 3354:2008(E) ISO 2008 All rights

11、 reserved iiiContents Page Foreword. v 1 Scope 1 2 Normative references 1 3 Terms and symbols .2 3.1 Terms 2 3.2 Symbols 3 4 Principle4 4.1 General4 4.2 Measurement of the measuring cross-section .5 4.3 Measurement of local velocities.6 4.4 Location and number of measuring points in the cross-sectio

12、n .7 5 Description of the current-meter9 6 Requirements for the use of current-meters 9 6.1 Selection of the measuring cross-section 9 6.2 Devices for improving flow conditions10 6.3 Calibration of the current-meter.11 6.4 Limits of use.11 6.5 Inspection and maintenance of current-meters .13 7 Setti

13、ng of current-meters into the conduit13 7.1 Setting of current-meters13 7.2 Mounting in a circular cross-section.13 7.3 Mounting in a rectangular cross-section 14 8 Determination of the mean axial fluid velocity by graphical integration of the velocity area .16 8.1 General16 8.2 Circular cross-secti

14、ons.16 8.3 Rectangular cross-sections18 9 Determination of the mean axial fluid velocity by numerical integration of the velocity area20 9.1 General20 9.2 Circular cross-sections.21 9.3 Rectangular cross-sections22 10 Determination of the mean axial fluid velocity by arithmetical methods.23 10.1 Gen

15、eral23 10.2 Log-linear method23 10.3 Log-Chebyshev method25 11 Uncertainty in the measurement of flow-rate .27 11.1 General27 11.2 Sources of error in local velocity measurements 27 11.3 Sources of error in estimation of flow-rate .28 11.4 Propagation of errors 29 11.5 Presentation of results29 11.6

16、 Calculation of uncertainty.30 Annex A (normative) Measuring sections other than circular or rectangular sections 33 Annex B (normative) Corrections for blockage effect.38 BS ISO 3354:2008ISO 3354:2008(E) iv ISO 2008 All rights reservedAnnex C (normative) Recommendations for the selection of the typ

17、e of current-meter and mounting strut. 39 Annex D (normative) Example of measuring point distribution along a radius for velocity measurement in a conduit of circular cross-section in the case of the graphical and numerical methods . 41 Annex E (normative) Determination of boundary layer coefficient

18、, m, for extrapolation near the wall 43 Annex F (normative) Definition of terms and procedures used in the uncertainty calculation . 45 Annex G (normative) Students t distribution 48 Annex H (informative) Examples of values of component uncertainties 49 Annex J (informative) Example of calculation o

19、f the uncertainty in the flow-rate measurement using current-meters 51 BS ISO 3354:2008ISO 3354:2008(E) ISO 2008 All rights reserved vForeword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing In

20、ternational Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison

21、with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of techn

22、ical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn

23、 to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. This International Standard was prepared by Technical Committee ISO/TC 30, Measurement of fluid flow in closed conduits

24、, Subcommittee SC 5, Velocity and mass methods. This third edition results from the reinstatement of ISO 3354:1988 which was withdrawn in 2003 and with which it is technically identical. BS ISO 3354:2008BS ISO 3354:2008INTERNATIONAL STANDARD ISO 3354:2008(E) ISO 2008 All rights reserved 1Measurement

25、 of clean water flow in closed conduits Velocity-area method using current-meters in full conduits and under regular flow conditions 1 Scope This International Standard specifies a method for the determination of the volume flow-rate in a closed conduit by means of the velocity-area method using pro

26、peller-type current-meters under the following conditions: a) the velocity distribution is regular (see 6.1.2); b) the fluid is water which is clean or considered to be clean 1); c) the conduit is full; d) the flow is steady 2). It deals in particular with the technology and calibration of propeller

27、-type current-meters, the measurement of local velocities and the calculation of the flow-rate by velocity integration. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated

28、references, the latest edition of the referenced document (including any amendments) applies. ISO 3455, Hydrometry Calibration of current-meters in straight open tanks ISO 4006, Measurement of fluid flow in closed conduits Vocabulary and symbols ISO 5168, Measurement of fluid flow Procedures for the

29、 evaluation of uncertainties ISO 7194, Measurement of fluid flow in closed conduits Velocity-area methods of flow measurement in swirling or asymmetric flow conditions in circular ducts by means of current-meters or Pitot static tubes 1) This method may be applied to other single-phase fluids but sp

30、ecial precautions should be taken in this case. 2) The steady flows observed in conduits are in practice flows in which quantities such as velocity, pressure, density and temperature vary in time about mean values independent of time; these are actually “mean steady flows”. BS ISO 3354:2008ISO 3354:

31、2008(E) 2 ISO 2008 All rights reserved3 Terms, definitions and symbols For the purposes of this document, the terms and definitions given in ISO 4006 and the following apply. 3.1 Terms 3.1.1 current-meter device provided with a rotor the rotational frequency of which is a function of the local veloc

32、ity of the fluid in which the device is immersed NOTE 1 This International Standard is concerned only with propeller-type current-meters, i.e. current-meters the rotor of which is a propeller rotating around an axis approximately parallel to the direction of flow. NOTE 2 Obviously this definition do

33、es not prohibit the use of self-compensating propellers (see 6.1.5), the merit of which is, in particular, that they can be used at a rather high angle relative to the local direction of the flow. However, the use of cup-type current-meters is not allowed for the purposes of this International Stand

34、ard. 3.1.2 stationary array set of current-meters mounted on one or more fixed supports which sample simultaneously the whole measuring cross-section 3.1.3 peripheral flow-rate the volume flow-rate in the area located between the pipe wall and the contour defined by the velocity measuring points whi

35、ch are closest to the wall 3.1.4 mean axial fluid velocity ratio of the volume flow-rate (the integral over a cross-section of the conduit of the axial components of the local fluid velocity) to the area of the measuring cross-section 3.1.5 relative velocity ratio of the flow velocity at the conside

36、red point to a reference velocity measured at the same time, which is either the velocity at a particular point (e.g. at the centre of a circular conduit) or the mean axial fluid velocity in the measuring section 3.1.6 straight length portion of a conduit whose axis is straight, and in which the cro

37、ss-sectional area and cross-sectional shape are constant; the cross-sectional shape is usually circular or rectangular, but could be annular or any other regular shape 3.1.7 irregularity any pipe fitting or configuration of a conduit which renders the conduit different from a straight length or whic

38、h produces a considerable difference in wall roughness NOTE In the case of the method of measurement specified in this International Standard, those irregularities which create the most serious disturbances are generally bends, valves, gates and sudden widening of the cross-section. 3.1.8 hydraulic

39、diameter diameter equal to four times the hydraulic radius, i.e. four times the ratio of the wetted cross-sectional area to the wetted perimeter EXAMPLE In a conduit of circular cross-section running full, the hydraulic diameter is equal to the geometric diameter. BS ISO 3354:2008ISO 3354:2008(E) IS

40、O 2008 All rights reserved 33.1.9 index of asymmetry for circular ducts ratio of the standard deviation of the mean velocities calculated along each radius (i.e. along each radial line from the pipe centre to the wall along which velocity measuring positions are located) to the mean axial fluid velo

41、city calculated for the pipe, i.e. ()1/ 22111iniUiUUYUU n=where Uiis the mean velocity, calculated, in accordance with the integration method agreed, from the individual point velocity measurements on the ith radius (see 8.2 and 9.2); U is the mean axial fluid velocity calculated from all the indivi

42、dual point velocity measurements throughout the cross-section; n is the number of radii along which measurements are made 3.1.10 regular velocity distribution distribution of velocities which sufficiently approaches a fully developed velocity distribution to permit an accurate measurement of the flo

43、w-rate to be made 3.2 Symbols Symbol Quantity Dimension SI unit A area of the measuring cross-section L2m2a, a distance along a measuring line in a rectangular cross-section from the extreme measuring point to the nearest wall L mD pipe diameter L m d propeller diameter L m e uncertainty (absolute v

44、alue) a aerrandom uncertainty aaessystematic uncertainty aaE relative uncertainty Errelative random uncertainty Esrelative systematic uncertainty H length of the smaller side of the cross-section of a rectangular conduit L m h distance from a given measuring point to the reference wall, in the direc

45、tion parallel with the smaller side of the cross-section L m k equivalent uniform roughness L m L length of the larger side of the cross-section of a rectangular conduit L mBS ISO 3354:2008ISO 3354:2008(E) 4 ISO 2008 All rights reservedSymbol Quantity Dimension SI unit l distance from a given measur

46、ing point to the reference wall, in the direction parallel with the larger side of the cross-section L mm boundary layer coefficient n frequency of rotation of a propeller T1r/s p number of measuring points along a radius (circular cross-section) or a straight line (rectangular cross-section) qVvolu

47、me flow-rate L3T1m3/s R pipe radius L m r measuring circle radius L m r*measuring circle relative radius, *rrR= Re Reynolds number U mean axial fluid velocity LT1m/s u mean velocity along a measurement circumference or line LT1m/s v local velocity of the fluid LT1m/s v0local velocity of the fluid at

48、 the centre-line of the pipe LT1m/s Y index of asymmetry of the flow y distance from a measuring point to the nearest wall L m y*relative interval between two measuring points, ( )*1iiyllL= polar angle of a measuring point (in a circular cross-section) rad universal coefficient for pipe head loss aT

49、he dimensions and units are those of the quantity to which the symbol refers. 4 Principle 4.1 General The principle of the method consists of a) measuring the dimensions of the measuring section, which shall be chosen to be normal to the conduit axis; this measurement is for defining the area of the cross-section (see 4.2); b) defining the position of the measuring points in this cross-section, where the number of measuring points shall be sufficient to