ASTM D3464-96(2023)
(Test Method)Standard Test Method for Average Velocity in a Duct Using a Thermal Anemometer
Standard Test Method for Average Velocity in a Duct Using a Thermal Anemometer
SIGNIFICANCE AND USE
5.1 The method presented is a “short method” that may be used where contamination levels are less than 5000 ppm by weight or volume, temperatures are between 0 °C (32 °F) and 65 °C (150 °F), and the humidity is not considered. The gas is considered as standard air and the velocity is read directly from the instrument.
5.2 This test method is useful for determining air velocities in HVAC ducts, fume hoods, vent stacks of nuclear power stations, and in performing model studies of pollution control devices.
SCOPE
1.1 This test method describes the measurement of the average velocity with a thermal anemometer for the purpose of determining gas flow in a stack, duct, or flue (1-5).2 It is limited to those applications where the gas is essentially air at ambient conditions and the temperature, moisture, and contaminant loading are insignificant as sources of error compared to the basic accuracy of the typical field situation.
1.2 The range of the test method is from 1 to 30 m/s (3 to 100 ft/s).
1.3 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for information only and are not considered standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
Relations
Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D3464 − 96 (Reapproved 2023)
Standard Test Method for
Average Velocity in a Duct Using a Thermal Anemometer
This standard is issued under the fixed designation D3464; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript 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. Scope 2.2 Other Standards:
ASME PTC 19.5-72 Application of Fluid Meters, Sixth Ed.
1.1 This test method describes the measurement of the
1971 (Interim Supplement 19.5 on Instruments & Appa-
average velocity with a thermal anemometer for the purpose of
2 ratus)
determining gas flow in a stack, duct, or flue (1-5). It is limited
to those applications where the gas is essentially air at ambient
3. Terminology
conditions and the temperature, moisture, and contaminant
3.1 For definitions of terms used in this test method, refer to
loading are insignificant as sources of error compared to the
Terminology D1356.
basic accuracy of the typical field situation.
1.2 The range of the test method is from 1 to 30 m/s (3 to
4. Summary of Test Method
100 ft/s).
4.1 This test method describes the operational and calibra-
1.3 The values stated in SI units are to be regarded as
tion procedures necessary for the measurement of point veloc-
standard. The values given in parentheses after SI units are
ity and calculation of the average velocity of air or gas flows in
provided for information only and are not considered standard.
flues, ducts, or stacks utilizing a thermal anemometer.
1.4 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the 5. Significance and Use
responsibility of the user of this standard to establish appro-
5.1 The method presented is a “short method” that may be
priate safety, health, and environmental practices and deter-
used where contamination levels are less than 5000 ppm by
mine the applicability of regulatory limitations prior to use.
weight or volume, temperatures are between 0 °C (32 °F) and
1.5 This international standard was developed in accor-
65 °C (150 °F), and the humidity is not considered. The gas is
dance with internationally recognized principles on standard-
considered as standard air and the velocity is read directly from
ization established in the Decision on Principles for the
the instrument.
Development of International Standards, Guides and Recom-
5.2 This test method is useful for determining air velocities
mendations issued by the World Trade Organization Technical
in HVAC ducts, fume hoods, vent stacks of nuclear power
Barriers to Trade (TBT) Committee.
stations, and in performing model studies of pollution control
devices.
2. Referenced Documents
2.1 ASTM Standards:
6. Apparatus
D1356 Terminology Relating to Sampling and Analysis of
6.1 Thermal Anemometer—A commercially available elec-
Atmospheres
trically operated hot sensor anemometer with direct readout. A
D3796 Practice for Calibration of Type S Pitot Tubes
thermal anemometer senses the cooling effect of a moving gas
stream passing over an electrically heated sensor. This cooling
1 effect or heat transfer rate is correlated to the velocity of the gas
This test method is under the jurisdiction of ASTM Committee D22 on Air
Quality and is the direct responsibility of Subcommittee D22.03 on Ambient
stream. The instrument is calibrated to display a direct readout
Atmospheres and Source Emissions.
in terms of velocity.
Current edition approved Jan. 1, 2023. Published February 2023. Originally
approved in 1975. Last previous edition approved in 2014 as D3464 – 96 (2014).
6.2 Sensors and Probes—There are a number of different
DOI: 10.1520/D3464-96R23.
types of sensors available for thermal anemometry including
The boldface numbers in parentheses refer to a list of references at the end of
this standard.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Available from American Society of Mechanical Engineers (ASME), ASME
Standards volume information, refer to the standard’s Document Summary page on International Headquarters, Two Park Ave., New York, NY 10016-5990, http://
the ASTM website. www.asme.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D3464 − 96 (2023)
the hot-wire sensor, the hot-film sensor, and the quartz-coated 9.2 To determine the average velocity in a flue it is
sensor. Probes are available in many different shapes depend- necessary to record several velocities. This is true even if the
ing upon application.
flow does not vary with time. Velocities in any flue cannot be
assumed to be uniform across any large cross-sectional area.
6.3 Temperature Compensation—If the temperature of the
However, in any single subarea, one may assume a constant
gas stream changes during velocity measurements, the an-
rate of change of velocity over the area with average velocity
emometer reading will change accordingly unless a constant-
at the centroid of this area. Determine the number of points and
temperature or “temperature-compensated” anemometer is uti-
their locations, at which velocities are to be recorded in
lized. This type of instrument shall be specified for most
accordance with commonly accepted practices when gas flow
applications of this measurement standard.
patterns are essentially uniform, that is, 80 to 90 % of the
6.3.1 Temperature-Compensated Anemometer—A
temperature-compensated anemometer has a temperature- measurements are greater than 10 % of the maximum flow. In
sensing probe within the instrument sensor that automatically all cases, divide the effective inside area of the flue into a
corrects errors caused by changes in temperature in the gas number of equal areas, and record the gas velocity at the
stream. For temperature-compensated anemometers, a change centroid of each of these areas.
in temperature (ΔT) of 28 °C (50 °F) typically produces an
9.2.1 In rectangular flues, divide the cross-sectional area
error of 2 %.
into equal rectangular subareas as shown in Fig. 1. The number
6.3.2 Temperature-Uncompensated Anemometer—For a
of areas to be used depends on the flow pattern and flue size.
“constant-current” or uncompensated anemometer a change in
Use Table 1 to find the minimum number of areas when
temperature (ΔT) of 28 °C (50 °F) typically produces a 25 %
sampling at least eight equivalent diameters downstream and
error. For laboratory work where this type of anemometer
two equivalent diameters upstream from the nearest flow
might be preferred, the output data shall be corrected for
disturbance, such as a bend, expansion or contraction. The
temperature changes in the gas stream.
equivalent diameter can be determined as follows:
6.4 Calibration Apparatus:
D 5 2LW/~L1W! (1)
e
6.4.1 Flows above 3 m/s (10 ft/s)—See Section 6, Practice
where:
D3796.
6.4.2 Flows below 3 m/s (10 ft/s)—See PTC 19.5-72.
D = equivalent diameter, m (ft),
e
L = duct length, m (ft), and
7. Calibration
W = duct width, m (ft).
7.1 For velocities in excess of 3 m/s (10 ft/s) calibrate the
If a site less than eight diameters downstream and two
thermal anemometer with a standard pitot tube, in accordance
diameters upstream from a flow disturbance, such as a bend,
with Practice D3796. It is preferable to make these calibrations
expansion or contraction is used increase the number of
under laboratory conditions; however, where expediency
sampling points in accordance with 9.2.4.
dictates, field calibration at the sampling site is permissible.
9.2.2 In circular flues divide the area concentrically as
7.2 For velocities below 3 m/s (10 ft/s) calibrate in the
shown in Fig. 2. The minimum number areas to be used and the
laboratory using a calibrated orifice or nozzle in accordance
distance to the test point are shown in Table 2 or calculate as
with PTC 19.5-72.
follows:
7.3 Calibrate the thermal anemometer for a minimum of
r 5 D = 2n 2 1 /4N (2)
~ !
n s
three velocities covering the range of velocities which are
anticipated for a particular test. Calibrate an increased number
where:
of points, typically five to seven, for the complete range of the
D = internal diameter of flue, cm (in.),
s
instrument if the anticipated test velocity range is not known.
r = radial distance from center of flue to nth sampling
n
(Warning—If this test method is used for gases other than air,
point, cm (in.),
calibrate using the test gas.)
n = nth sampling point from
...
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