ASTM D3464-96(2007)
(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
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.
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). 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 the standard.
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 and health practices and determine the applicability of regulatory limitations prior to use.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D3464 − 96(Reapproved 2007)
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 Department of Defense.
1. Scope 3. Terminology
1.1 This test method describes the measurement of the 3.1 For definitions of terms used in this test method, refer to
average velocity with a thermal anemometer for the purpose of Terminology D1356.
determininggasflowinastack,duct,orflue (1-5). Itislimited
4. Summary of Test Method
to those applications where the gas is essentially air at ambient
conditions and the temperature, moisture, and contaminant
4.1 This test method describes the operational and calibra-
loading are insignificant as sources of error compared to the
tion procedures necessary for the measurement of point veloc-
basic accuracy of the typical field situation.
ity and calculation of the average velocity of air or gas flows in
flues, ducts, or stacks utilizing a thermal anemometer.
1.2 The range of the test method is from 1 to 30 m/s (3 to
100 ft/s).
5. Significance and Use
1.3 The values stated in SI units are to be regarded as the
5.1 The method presented is a “short method” that may be
standard.
used where contamination levels are less than 5000 ppm by
1.4 This standard does not purport to address all of the
weight or volume, temperatures are between 0°C (32°F) and
safety concerns, if any, associated with its use. It is the
65°C (150°F), and the humidity is not considered. The gas is
responsibility of the user of this standard to establish appro-
consideredasstandardairandthevelocityisreaddirectlyfrom
priate safety and health practices and determine the applica-
the instrument.
bility of regulatory limitations prior to use.
5.2 This test method is useful for determining air velocities
in HVAC ducts, fume hoods, vent stacks of nuclear power
2. Referenced Documents
stations, and in performing model studies of pollution control
2.1 ASTM Standards:
devices.
D1356 Terminology Relating to Sampling and Analysis of
Atmospheres
6. Apparatus
D3796 Practice for Calibration of Type S Pitot Tubes
6.1 Thermal Anemometer—A commercially available elec-
2.2 Other Standards:
trically operated hot sensor anemometer with direct readout.A
ASME PTC 19.5-72Application of Fluid Meters, Sixth Ed.
thermal anemometer senses the cooling effect of a moving gas
1971 (Interim Supplement 19.5 on Instruments & Appa-
stream passing over an electrically heated sensor. This cooling
ratus)
effectorheattransferrateiscorrelatedtothevelocityofthegas
stream. The instrument is calibrated to display a direct readout
in terms of velocity.
This test method is under the jurisdiction of ASTM Committee D22 on Air
6.2 Sensors and Probes—There are a number of different
Quality and is the direct responsibility of Subcommittee D22.03 on Ambient
Atmospheres and Source Emissions.
types of sensors available for thermal anemometry including
Current edition approved April 1, 2007. Published June 2007. Originally
the hot-wire sensor, the hot-film sensor, and the quartz-coated
approved in 1975. Last previous edition approved in 2001 as D3464 - 96(2001).
sensor. Probes are available in many different shapes depend-
DOI: 10.1520/D3464-96R07.
ing upon application.
The boldface numbers in parentheses refer to the references listed at the end of
this method.
6.3 Temperature Compensation—If the temperature of the
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
gas stream changes during velocity measurements, the an-
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
emometer reading will change accordingly unless a constant-
the ASTM website.
temperature or “temperature-compensated” anemometer is uti-
Available from American Society of Mechanical Engineers (ASME), ASME
lized. This type of instrument shall be specified for most
International Headquarters, Three Park Ave., New York, NY 10016-5990, http://
www.asme.org. applications of this measurement standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D3464 − 96 (2007)
6.3.1 Temperature-Compensated Anemometer—A patterns are essentially uniform, that is, 80 to 90 % of the
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 (∆T) of 28°C (50°F) typically produces an error 9.2.1 In rectangular flues, divide the cross-sectional area
of 2 %. intoequalrectangularsubareasasshowninFig.1.Thenumber
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 (∆T) 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:
D 5 2LW/ L1W (1)
6.4 Calibration Apparatus: ~ !
e
6.4.1 Flows above 3 m/s (10 ft/s)—See Section 6, Practice
where:
D3796.
D = equivalent diameter, m (ft),
e
6.4.2 Flows below 3 m/s (10 ft/s)—See PTC 19.5-72.
L = duct length, m (ft), and
W = duct width, m (ft).
7. Calibration
If a site less than eight diameters downstream and two
7.1 For velocities in excess of 3 m/s (10 ft/s) calibrate the
diameters upstream from a flow disturbance, such as a bend,
thermal anemometer with a standard pitot tube, in accordance
expansion or contraction is used increase the number of
with Practice D3796. It is preferable to make these calibrations
sampling points in accordance with 9.2.4.
under laboratory conditions; however, where expediency
9.2.2 In circular flues divide the area concentrically as
dictates, field calibration at the sampling site is permissible.
showninFig.2.Theminimumnumberareastobeusedandthe
7.2 For velocities below 3 m/s (10 ft/s) calibrate in the
distance to the test point are shown in Table 2 or calculate as
laboratory using a calibrated orifice or nozzle in accordance
follows:
with PTC 19.5-72.
=
r 5 D ~2n 2 1!/4N (2)
n s
7.3 Calibrate the thermal anemometer for a minimum of
three velocities covering the range of velocities which are
where:
anticipated for a particular test. Calibrate an increased number
D = internal diameter of flue, cm (in.),
s
of points, typically five to seven, for the complete range of the
r = radial distance from center of flue to nth sampling
n
instrument if the anticipated test velocity range is not known.
point, cm (in.),
(Warning— If this test method is used for gases other than air,
n = nth sampling point from center of flue, and
calibrate using the test gas.)
N = number of sampling points across a diameter.
Conduct traverses across two diameter axes right angles to
8. Single-Point Velocity Measurement
each other. Again, if a site less than eight diameters down-
8.1 Velocity—The hot-wire anemometer is effective for
stream and two diameters upstream from a flow disturbance is
measuring velocities over a range from 1 m/s (3 ft/s) to 30 m/s
used, increase the number of sampling points as indicated in
(100 ft/s). Record measurements at specific points within the
9.2.4.
flue in accordance with a plan determined by the flue size.
9.2.3 When readings must be taken in an irregular-shaped
Place marks on the instrument probe or probe extension to aid
flue, divide the flue into equal areas of any shape, and measure
in locating the sampling points at w
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.