ISO-3966-2008.pdf
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1、 Reference number ISO 3966:2008(E) ISO 2008 INTERNATIONAL STANDARD ISO 3966 Second edition 2008-07-15 Measurement of fluid flow in closed conduits Velocity area method using Pitot static tubes Mesurage du dbit des fluides dans les conduites fermes Mthode dexploration du champ des vitesses au moyen d
2、e tubes de Pitot doubles ISO 3966:2008(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobes licensing policy, this file may be printed or viewed but shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performi
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5、etariat at the address given below. COPYRIGHT 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 writ
6、ing from either ISO at the address below or 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 reserved ISO 3966:
7、2008(E) ISO 2008 All rights reserved iii Contents Page Foreword iv 1 Scope . 1 2 Normative references. 1 3 Symbols and definitions 2 4 Principle. 4 5 Design of Pitot tubes 7 6 Requirements for use of Pitot tubes. 8 7 Positioning of Pitot tube 11 8 Velocity computation 11 9 Determination of the disch
8、arge velocity by graphical integration of the velocity area 14 10 Determination of the discharge velocity by numerical integration of the velocity area . 17 11 Determination of the discharge velocity by arithmetical methods 19 12 Corrections of local velocity measurements. 23 13 Errors . 28 Annex A
9、(normative) Pitot tubes 34 Annex B (normative) Correction to the measuring position of Pitot tubes used in a transverse velocity gradient . 39 Annex C (normative) Study concerning turbulence correction 41 Annex D (normative) Damping of pressure gauges . 44 Annex E (normative) Measurements with a Pit
10、ot tube in a compressible fluid. 46 Annex F (normative) Determination of coefficient m for extrapolation near the wall . 50 Annex G (normative) Example of calculation of the uncertainty on the flow-rate measurement by means of Pitot tubes. 51 Bibliography. 54 -,-,- ISO 3966:2008(E) iv ISO 2008 All r
11、ights reserved Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subjec
12、t 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 with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC)
13、 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 technical committees is to prepare International Standards. Draft International Standards adopted by the technical committee
14、s 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 to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be he
15、ld responsible for identifying any or all such patent rights. ISO 3966 was prepared by Technical Committee ISO/TC 30, Measurement of fluid flow in closed conduits, Subcommittee SC 5, Velocity and mass methods. This second edition results from the reinstatement of ISO 3966:1977 which was withdrawn in
16、 2003 and with which it is technically identical. INTERNATIONAL STANDARD ISO 3966:2008(E) ISO 2008 All rights reserved 1 Measurement of fluid flow in closed conduits Velocity area method using Pitot static tubes 1 Scope This International Standard specifies a method for the determination in a closed
17、 conduit of the volume rate of flow of a regular flow: a) of a fluid of substantially constant density or corresponding to a Mach number not exceeding 0,25; b) with substantially uniform stagnation temperature across the measuring cross-section; c) running full in the conduit; d) under steady flow c
18、onditions. In particular, it deals with the technology and maintenance of Pitot static tubes, with the calculation of local velocities from measured differential pressures and with the computation of the flow rate by velocity integration. 2 Normative references The following referenced documents are
19、 indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 2186, Fluid flow in closed conduits Connections for pressure signal transmissions b
20、etween primary and secondary elements 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 -,-,- ISO 3966:2008(E) 2 ISO 2008 All rights reserved 3
21、Symbols and definitions 3.1 Symbols Symbol Quantity Dimensions SI unit A cross-sectional area of the conduit L2 m2 a, a distance of the extreme measuring point to the nearest wall L m D pipe diameter L m d head diameter L m d steam diameter L m di total pressure tapping hole diameter L m H rectangul
22、ar conduit height L m h height of a particular point above the bottom L m kb blockage coefficient of a cylindrical stem kg coefficient depending on the nose shape kt coefficient of turbulence correction L rectangular conduit width L m l distance from a particular point to the side-wall L m M molar m
23、ass of fluid M kg/mol m roughness coefficient Ma Mach number p absolute static pressure of the fluid ML1T2 Pa qV volume flow rate L3T1 m3/s Rg molar constant of gas ML2T11 J/molK R pipe radius L m r measuring circle radius L m Re Reynolds number S frontal projected area of the stem inside the condui
24、t L2 m2 T absolute temperature K U discharge velocity LT1 m/s u mean velocity along a circumference or a measurement line LT1 m/s v local velocity of the fluid LT1 m/s X pipe dimension L m y distance of a measuring point to the wall L m Z gas law deviation factor calibration factor of the Pitot tube
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