ASTM C1371-15(2022)
(Test Method)Standard Test Method for Determination of Emittance of Materials Near Room Temperature Using Portable Emissometers
Standard Test Method for Determination of Emittance of Materials Near Room Temperature Using Portable Emissometers
SIGNIFICANCE AND USE
5.1 Surface Emittance Testing:
5.1.1 Heat transfer from a surface by radiation transfer is reduced if the surface of a material has a low emittance. Since the controlling factor in the use of insulation is sometimes condensation control or personnel protection, it is important to understand that a low emittance will change the surface temperature of a material. One possible criterion in the selection of these materials is the question of the effect of aging on the surface emittance. If the initial low surface emittance of a material is not maintained during service, then the long-term value of the material is diminished.
5.1.2 This test method provides a means for comparative periodic testing of low emittance surfaces in the field. In this way the effects of aging on the reflective properties can be monitored.
5.1.3 This test method determines the total hemispherical emittance with a precision of better than ±0.02 units.(1) The emittances of the calibration standards shall have been obtained from accurate independent measurements of total hemispherical emittance. This test method shall not be used for specimens that are highly anisotropic or transparent to infrared radiation. This test method also shall not be used for specimens with significant thermal resistance (see 7.3.4).
5.1.4 Once a reliable emittance measurement has been determined, the value is available to be used to calculate radiative heat flow from the subject surface. For example, if the temperature of the surface, T1, and the temperature of the surroundings, T2, are known, then the radiative heat flow, Qrad, is given by:
where A is the area of the surface, and either A is assumed to be much smaller than the area of the surroundings or the emittance of the surroundings is assumed to be unity. This radiative heat flow when combined with convective and conductive heat flows provides the total heat flow from the surface (a method for calculating total heat flow is described in Practic...
SCOPE
1.1 This test method covers a technique for determination of the emittance of opaque and highly thermally conductive materials using a portable differential thermopile emissometer. The purpose of the test method is to provide a comparative means of quantifying the emittance of materials near room temperature.
1.2 This test method does not supplant Test Method C835, which is an absolute method for determination of total hemispherical emittance, or Test Method E408, which includes two comparative methods for determination of total normal emittance. Because of the unique construction of the portable emissometer, it can be calibrated to measure the total hemispherical emittance. This is supported by comparison of emissometer measurements with those of Test Method C835 (1).2
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this 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: C1371 − 15 (Reapproved 2022)
Standard Test Method for
Determination of Emittance of Materials Near Room
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Temperature Using Portable Emissometers
This standard is issued under the fixed designation C1371; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
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2.1 ASTM Standards:
1.1 Thistestmethodcoversatechniquefordeterminationof
the emittance of opaque and highly thermally conductive C168Terminology Relating to Thermal Insulation
C680Practice for Estimate of the Heat Gain or Loss and the
materials using a portable differential thermopile emissometer.
The purpose of the test method is to provide a comparative Surface Temperatures of Insulated Flat, Cylindrical, and
Spherical Systems by Use of Computer Programs
means of quantifying the emittance of materials near room
temperature. C835Test Method for Total Hemispherical Emittance of
Surfaces up to 1400°C
1.2 This test method does not supplant Test Method C835,
E177Practice for Use of the Terms Precision and Bias in
which is an absolute method for determination of total hemi-
ASTM Test Methods
spherical emittance, orTest Method E408, which includes two
E408Test Methods for Total Normal Emittance of Surfaces
comparative methods for determination of total normal emit-
Using Inspection-Meter Techniques
tance. Because of the unique construction of the portable
E691Practice for Conducting an Interlaboratory Study to
emissometer, it can be calibrated to measure the total hemi-
Determine the Precision of a Test Method
spherical emittance. This is supported by comparison of
emissometer measurements with those of Test Method C835
3. Terminology
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(1).
3.1 Definitions—For definitions of some terms used in this
1.3 The values stated in SI units are to be regarded as
test method, refer to Terminology C168.
standard. No other units of measurement are included in this
3.2 Definitions of Terms Specific to This Standard:
standard.
3.2.1 diffuse surface—a surface that emits or reflects equal
radiation intensity, or both, in all directions (2).
1.4 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
3.2.2 emissive power—the rate of radiative energy emission
responsibility of the user of this standard to establish appro-
per unit area from a surface (2).
priate safety, health, and environmental practices and deter-
3.2.3 emissometer—an instrument used for measurement of
mine the applicability of regulatory limitations prior to use.
emittance.
1.5 This international standard was developed in accor-
3.2.4 Lambert’s cosine law—the mathematical relation de-
dance with internationally recognized principles on standard-
scribing the variation of emissive power from a diffuse surface
ization established in the Decision on Principles for the
asvaryingwiththecosineoftheanglemeasuredawayfromthe
Development of International Standards, Guides and Recom-
normal of the surface (2).
mendations issued by the World Trade Organization Technical
3.2.5 normal emittance—the directional emittance perpen-
Barriers to Trade (TBT) Committee.
dicular to the surface.
3.2.6 radiative intensity—radiative energy passing through
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an area per unit solid angle, per unit of the area projected
ThistestmethodisunderthejurisdictionofASTMCommitteeC16onThermal
Insulation and is the direct responsibility of Subcommittee C16.30 on Thermal normal to the direction of passage, and per unit time (2).
Measurement.
Current edition approved May 1, 2022. Published June 2022. Originally
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approved in 1997. Last previous edition approved in 2015 as C1371–15. DOI: For referenced ASTM standards, visit the ASTM website, www.astm.org, or
10.1520/C1371-15R22. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
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Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof Standards volume information, refer to the standard’s Document Summary page on
this standard. the ASTM website.
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C1371 − 15 (2022)
NOTE 1—(a) Emissometer measuring head on high-emittance standard during calibration, showing heat sink and cable to readout device. (b) Bottom
view of emissometer measuring head showing high- and low-emittance detector elements. The diameter of the emissometer measuring head is
...
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