ASTM_D_3464_-_96_2014.pdf

Designation:D346496(Reapproved 2014)Standard Test Method forAverage Velocity in a Duct Using a Thermal Anemometer1This standard is issued under the fixed designation D3464;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S.Department of Defense.1.Scope1.1 This test method describes the 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 sources 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,associated 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:3D1356 Terminology Relating to Sampling and Analysis ofAtmospheresD3796 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&Appa-ratus)43.Terminology3.1 For definitions of terms used in this test method,refer toTerminology D1356.4.Summary of Test Method4.1 This test method describes the operational and calibra-tion procedures necessary for the measurement of point veloc-ity and calculation of the average velocity of air or gas flows influes,ducts,or stacks utilizing a thermal anemometer.5.Significance and Use5.1 The method presented is a“short method”that may beused where contamination levels are less than 5000 ppm byweight or volume,temperatures are between 0C(32F)and65C(150F),and the humidity is not considered.The gas isconsidered as standard air and the velocity is read directly fromthe instrument.5.2 This test method is useful for determining air velocitiesin HVAC ducts,fume hoods,vent stacks of nuclear powerstations,and in performing model studies of pollution controldevices.6.Apparatus6.1 Thermal AnemometerA commercially available elec-trically operated hot sensor anemometer with direct readout.Athermal anemometer senses the cooling effect of a moving gasstream passing over an electrically heated sensor.This coolingeffect or heat transfer rate is correlated to the velocity of the gasstream.The instrument is calibrated to display a direct readoutin terms of velocity.6.2 Sensors and ProbesThere are a number of differenttypes of sensors available for thermal anemometry includingthe hot-wire sensor,the hot-film sensor,and the quartz-coatedsensor.Probes are available in many different shapes depend-ing upon application.6.3 Temperature CompensationIf the temperature of thegas stream changes during velocity measurements,the an-emometer reading will change accordingly unless a constant-temperature or“temperature-compensated”anemometer is uti-lized.This type of instrument shall be specified for mostapplications of this measurement standard.1This test method is under the jurisdiction of ASTM Committee D22 on AirQuality and is the direct responsibility of Subcommittee D22.03on AmbientAtmospheres and Source Emissions.Current edition approved April 1,2014.Published May 2014.Originallyapproved in 1975.Last previous edition approved in 2007 as D3464 96(2007).DOI:10.1520/D3464-96R14.2The boldface numbers in parentheses refer to a list of references at the end ofthis standard.3For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.4Available from American Society of Mechanical Engineers(ASME),ASMEInternational Headquarters,Two Park Ave.,New York,NY 10016-5990,http:/www.asme.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 6.3.1 Temperature-CompensatedAnemometerAtemperature-compensated anemometer has a temperature-sensing probe within the instrument sensor that automaticallycorrects errors caused by changes in temperature in the gasstream.For temperature-compensated anemometers,a changein temperature(T)of 28C(50F)typically produces an errorof 2%.6.3.2 Temperature-Uncompensated AnemometerFor a“constant-current”or uncompensated anemometer a change intemperature(T)of 28C(50F)typically produces a 25%error.For laboratory work where this type of anemometermight be preferred,the output