1、Designation: D 3464 96 (Reapproved 2001)Standard Test Method forAverage Velocity in a Duct Using a Thermal Anemometer1This standard is issued under the fixed designation D 3464; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the y
2、ear of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 This test method describes th
3、e measurement of theaverage velocity with a thermal anemometer for the purpose ofdetermining gas flow in a stack, duct, or flue (1-5).2It is limitedto those applications where the gas is essentially air at ambientconditions and the temperature, moisture, and contaminantloading are insignificant as s
4、ources of error compared to thebasic accuracy of the typical field situation.1.2 The range of the test method is from 1 to 30 m/s (3 to100 ft/s).1.3 The values stated in SI units are to be regarded as thestandard.1.4 This standard does not purport to address all of thesafety concerns, if any, associ
5、ated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3D 1356 Terminology Relating to Sampling and Analysis ofAtmo
6、spheresD 3796 Practice for Calibration of Type S Pitot Tubes2.2 Other Standards:ASME PTC 19.5-72 Application of Fluid Meters, Sixth Ed.1971 (Interim Supplement 19.5 on Instruments however, where expediency dic-tates, field calibration at the sampling site is permissible.7.2 For velocities below 3 m/
7、s (10 ft/s) calibrate in thelaboratory using a calibrated orifice or nozzle in accordancewith PTC 19.5-72.7.3 Calibrate the thermal anemometer for a minimum ofthree velocities covering the range of velocities which areanticipated for a particular test. Calibrate an increased numberof points, typical
8、ly five to seven, for the complete range of theinstrument if the anticipated test velocity range is not known.(WarningIf this test method is used for gases other than air,calibrate using the test gas.)8. Single-Point Velocity Measurement8.1 VelocityThe hot-wire anemometer is effective formeasuring v
9、elocities over a range from 1 m/s (3 ft/s) to 30 m/s(100 ft/s). Record measurements at specific points within theflue in accordance with a plan determined by the flue size.Place marks on the instrument probe or probe extension to aidin locating the sampling points at which the velocity is to bemeasu
10、red.9. Average Velocity Measurements9.1 Average Velocity Average flue gas velocity is equal tothe algebraic average of the single point velocity measurementsmade in accordance with 9.2-9.2.4.9.2 To determine the average velocity in a flue it isnecessary to record several velocities. This is true eve
11、n if theflow does not vary with time. Velocities in any flue cannot beassumed to be uniform across any large cross-sectional area.However, in any single subarea, one may assume a constantrate of change of velocity over the area with average velocityat the centroid of this area. Determine the number
12、of points andtheir locations, at which velocities are to be recorded inaccordance with commonly accepted practices when gas flowpatterns are essentially uniform, that is, 80 to 90 % of themeasurements are greater than 10 % of the maximum flow. Inall cases, divide the effective inside area of the flu
13、e into anumber of equal areas, and record the gas velocity at thecentroid of each of these areas.9.2.1 In rectangular flues, divide the cross-sectional areainto equal rectangular subareas as shown in Fig. 1. The numberof areas to be used depends on the flow pattern and flue size.Use Table 1 to find
14、the minimum number of areas whensampling at least eight equivalent diameters downstream andtwo equivalent diameters upstream from the nearest flowdisturbance, such as a bend, expansion or contraction. Theequivalent diameter can be determined as follows:De5 2LW/L 1 W! (1)where:De= equivalent diameter
15、, m (ft),L = duct length, m (ft), andW = duct width, m (ft).If a site less than eight diameters downstream and twodiameters upstream from a flow disturbance, such as a bend,expansion or contraction is used increase the number ofsampling points in accordance with 9.2.4.9.2.2 In circular flues divide
16、the area concentrically asshown in Fig. 2. The minimum number areas to be used and thedistance to the test point are shown in Table 2 or calculate asfollows:rn5 Ds=2n 2 1!/4N (2)where:Ds= internal diameter of flue, cm (in.),rn= radial distance from center of flue to nth samplingpoint, cm (in.),n = n
17、th sampling point from center of flue, andN = number of sampling points across a diameter.Conduct traverses across two diameter axes right angles toeach other. Again, if a site less than eight diameters down-stream and two diameters upstream from a flow disturbance isused, increase the number of sam
18、pling points as indicated in9.2.4.9.2.3 When readings must be taken in an irregular-shapedflue, divide the flue into equal areas of any shape, and measurethe parameters at the centroid of each area.9.2.4 Increase the number of sampling points when sam-pling less than eight diameters downstream and t
19、wo diametersupstream from any flow disturbance. When only four to sixdiameters of straight duct are available, double the number ofpoints. Sampling sites less than four diameters downstreamfrom any flow disturbance are special cases, and each caseshall be determined on its own merits in the field. W
20、heresampling sites are less than two diameters downstream fromany flow disturbances, reasonable accuracy with this typemeasurement cannot be expected and another method fordetermining stack gas velocity should be used.FIG. 1 Traverse Positions for Rectangular FlueD 3464 96 (2001)29.3 Changing Flow C
21、onditionsIf the flow rate changesmoderately during the test period, continuously monitor thischange by measuring the velocity at a single point and relatingthis velocity to the total flow obtained during a fairly stableperiod. Determine the point of approximate average velocityduring stable flow con
22、ditions and locate a fixed probe at thispoint for reference during the period of changing flow. Theaverage velocity in a flue is then equal to the average velocityduring a stable run multiplied by the ratio of the velocity at thereference point to the velocity at the reference point during thestable
23、 run.uavg5 us!avgur/ us! (3)where:uavg= average flue gas velocity, m/s (ft/s),ur= flue gas velocity at reference point, m/s (ft/s),(us) = velocity at reference point during stable run, m/s(ft/s), and(us)avg= average flue gas velocity during stable run, m/s(ft/s).10. Set-up Procedures10.1 Number of T
24、raverse PointsSelect traverse points asindicated in 9.2-9.2.4.10.2 Preparation of Probe or Probe HolderA simplemethod for marking off the probe or probe holder for use intaking a velocity traverse is as follows:10.2.1 Slide the probe all the way through the sampling portuntil the tip touches the far
25、 wall of the flue and is aligned inaccordance with the manufacturers instructions. Using a chinamarker or other suitable means, mark the probe at a pointimmediately adjacent to the sampling port fitting.10.2.2 Slide the probe out of the port until the tip is evenwith the inner wall of the stack. Aga
26、in mark it at a pointimmediately adjacent to the sampling port fitting.10.2.3 The distance between the two lines is the internaldiameter of the stack (Ds). Mark the centerline halfwaybetween these two points.10.2.4 Mark the traverse points on the probe after referringto Table 2, or use Eq 1. (It is
27、advisable to mark the traversepoints in one manner and the centerline and end points in adifferent manner.)10.2.5 Determine the velocity only at the traverse points andnot at the centerline or at the walls. This method allows for wallthickness, breach fittings, etc., so that only the internal dimen-
28、sions are considered.10.3 Assembling EquipmentIf the length of the probe isinsufficient to make a valid traverse of the duct, it will benecessary to attach the probe to a pipe or pole to extend itseffective length. This effective length is the limiting factor onthe size of the ducts that can be meas
29、ured.NOTE 1As this method becomes acceptable, it is anticipated thatprobes of adequate length will be available for most cases where this“short” method applies.10.4 InsertionAlign the probe so that it is parallel to theduct walls and faces the gas stream. Seal the breach around theprobe to prevent a
30、ir from leaking into or out of the duct. Theprobe can now be moved to each point on the traverse plan.10.5 Measurement Record the velocity where applicableat each traverse point.11. Precision and Bias11.1 Velocities of 0.025 to 5 m/s (0.08 to 17 ft/s) giveaccuracies better than 6 20 % and above 10 m
31、/s (33 ft/s), theaccuracy becomes 6 10 % or better (6).12. Keywords12.1 air velocity; anemometer; atmospheres; gas velocity;hot wire anemometer; measurements; pitot tube; thermal an-emometerTABLE 1 Minimum Number of Measurements forRectangular DuctsCross Sectional Area ofSampling Sites m2(ft2)Number
32、 ofMeasurementsLess than 0.2 (2) 40.2 to 2.3 (2 to 25) 12Greater than 2.3 (25) 20FIG. 2 Traverse Positions for Round FlueTABLE 2 Location of Traverse Points in Circular Stacks(Percent of Stack Diameter From Inside Wall to Traverse Point)TraversePointNumberon aDiameterNumber of Traverse Points on a D
33、iameter24681012141618202241 14.6 6.7 4.4 3.2 2.6 2.1 1.8 1.6 1.4 1.3 1.1 1.12 85.4 25.0 14.6 10.5 8.2 6.7 5.7 4.9 4.4 3.9 3.5 3.23 75.0 29.6 19.4 14.6 11.8 9.9 8.5 7.5 6.7 6.0 5.54 93.3 70.4 32.3 22.6 17.7 14.6 12.5 10.9 9.7 8.7 7.95 85.4 67.7 34.2 25.0 20.1 16.9 14.6 12.9 11.6 10.56 95.6 80.6 65.8
34、35.6 26.9 22.0 18.8 16.5 14.6 13.27 89.5 77.4 64.4 36.6 28.3 23.6 20.4 18.0 16.18 96.8 85.4 75.0 63.4 37.5 29.6 25.0 21.6 19.49 91.8 82.3 73.1 62.5 38.6 30.6 26.2 23.010 97.4 88.2 79.9 71.7 61.8 38.9 31.5 27.211 93.3 85.3 78.0 70.4 61.2 39.3 32.312 97.9 90.1 83.1 76.4 69.4 60.7 39.813 94.3 87.5 81.2
35、 75.0 68.5 60.214 98.2 91.5 85.4 79.6 73.8 67.715 95.1 89.1 83.5 78.2 72.816 98.4 92.5 87.1 82.0 77.0171819202122232495.698.690.393.396.198.785.488.491.394.096.598.980.683.986.889.592.194.596.898.9D 3464 96 (2001)3REFERENCES(1) Fingerson, L. M., “Parameter for Comparing Anemometer Response,”Symposiu
36、m on Turbulence in Liquids, University of Missouri, Rolla,MO, Oct 4 to 6, 1972 (available as Technical Bulletin TB-6, fromThermo-Systems, Inc., 2500 Cleveland Avenue North, St. Paul, MN55113).(2) Ackeret, J., Fluid Mechanics of Internal Flow, Elsevier Publishing Co.1967, pp. 126.(3) Fluid Meters, Th
37、eir Theory and Application, The American Society ofMechanical Engineers, New York, NY 6th Edition, 1971, pp. 105107.(4) Benson, J. M., “Survey of Thermal Devices for Measuring Flow,”Paper 2-1-213, Symposium on FlowIts Measurement and Control inScience and Industry, Pittsburgh, PA, May 10 to 14, 1971
38、.(5) Burton, C. L., “Quantitation of Stack Gas Flow,” Journal of AirPollution Control Association, Vol 22, 1972, pp. 631635.(6) ASHRAE Handbook of Fundamentals, American Society of Heating,Refrigeration, and Air Conditioning Engineers, 1719 Tullie Circle,N.E., Atlanta, GA 30329 (1986) SI Edition, Ch
39、apter 13-86,“ Measure-ments and Instruments.”ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, an
40、d the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revisi
41、on of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you sh
42、ouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).D 3464 96 (2001)4
