ASTM C1371-15

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 and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 28-Feb-2015
• ICS: 17.200.10 - Heat. Calorimetry
• Technical Committee: C16 - Thermal Insulation
• Drafting Committee: C16.30 - Thermal Measurement

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: C1371 − 15
Standard Test Method for
Determination of Emittance of Materials Near Room
1
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 Spherical Systems by Use of Computer Programs
C835Test Method for Total Hemispherical Emittance of
1.1 Thistestmethodcoversatechniquefordeterminationof
Surfaces up to 1400°C
the emittance of opaque and highly thermally conductive
E177Practice for Use of the Terms Precision and Bias in
materials using a portable differential thermopile emissometer.
ASTM Test Methods
The purpose of the test method is to provide a comparative
E408Test Methods for Total Normal Emittance of Surfaces
means of quantifying the emittance of materials near room
Using Inspection-Meter Techniques
temperature.
E691Practice for Conducting an Interlaboratory Study to
1.2 This test method does not supplant Test Method C835,
Determine the Precision of a Test Method
which is an absolute method for determination of total hemi-
spherical emittance, orTest Method E408, which includes two
3. Terminology
comparative methods for determination of total normal emit-
3.1 Definitions—For definitions of some terms used in this
tance. Because of the unique construction of the portable
test method, refer to Terminology C168.
emissometer, it can be calibrated to measure the total hemi-
3.2 Definitions of Terms Specific to This Standard:
spherical emittance. This is supported by comparison of
3.2.1 diffuse surface—a surface that emits or reflects equal
emissometer measurements with those of Test Method C835
2
radiation intensity, or both, in all directions (2).
(1).
3.2.2 emissive power—the rate of radiative energy emission
1.3 The values stated in SI units are to be regarded as
per unit area from a surface (2).
standard. No other units of measurement are included in this
3.2.3 emissometer—an instrument used for measurement of
standard.
emittance.
1.4 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the 3.2.4 Lambert’s cosine law—the mathematical relation de-
responsibility of the user of this standard to establish appro- scribing the variation of emissive power from a diffuse surface
priate safety and health practices and determine the applica- asvaryingwiththecosineoftheanglemeasuredawayfromthe
bility of regulatory limitations prior to use. normal of the surface (2).
3.2.5 normal emittance—the directional emittance perpen-
2. Referenced Documents
dicular to the surface.
3
2.1 ASTM Standards:
3.2.6 radiative intensity—radiative energy passing through
C168Terminology Relating to Thermal Insulation
an area per unit solid angle, per unit of the area projected
C680Practice for Estimate of the Heat Gain or Loss and the
normal to the direction of passage, and per unit time (2).
Surface Temperatures of Insulated Flat, Cylindrical, and
3.2.7 spectral—having a dependence on wavelength; radia-
tion within a narrow region of wavelength (2).
1
ThistestmethodisunderthejurisdictionofASTMCommitteeC16onThermal
3.2.8 specular surface—mirrorlike in reflection behavior
Insulation and is the direct responsibility of Subcommittee C16.30 on Thermal
(2).
Measurement.
Current edition approved March 1, 2015. Published June 2015. Originally
3.3 Symbols:
ε1
approved in 1997. Last previous edition approved in 2010 as C1371-04a(2010) .
3.3.1 For standard symbols used in this test method, see
DOI: 10.1520/C1371-15.
2 Terminology C168. Additional symbols are listed here:
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
this standard.
α=total absorptance, dimensionless
3
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
α =spectral absorptance, dimensionless
λ
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
ε = total emittance of the high-emittance calibration
Standards volume information, refer to the standard’s Document Summary page on hi
the ASTM website. standard, dimensionless
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

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C1371 − 15
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 about 50
mm and the detector elements are recessed about 3 mm into the
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
´1
Designation: C1371 − 04a (Reapproved 2010) C1371 − 15
Standard Test Method for
Determination of Emittance of Materials Near Room
1
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. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1
ε NOTE—Section 5.1.4 was editorially revised in January 2011.
1. Scope
1.1 This test method covers a technique for determination of the emittance of typical 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 opaque, highly thermally conductive materials near room temperature as a parameter in evaluating
temperatures, heat flows, and derived thermal resistances of materials.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
2
supported by comparison of emissometer measurements with those of Test Method C835 (1).
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 and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
3
2.1 ASTM Standards:
C168 Terminology Relating to Thermal Insulation
C680 Practice for Estimate of the Heat Gain or Loss and the Surface Temperatures of Insulated Flat, Cylindrical, and Spherical
Systems by Use of Computer Programs
C835 Test Method for Total Hemispherical Emittance of Surfaces up to 1400°C
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E408 Test Methods for Total Normal Emittance of Surfaces Using Inspection-Meter Techniques
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
3. Terminology
3.1 Definitions—For definitions of some terms used in this test method, refer to Terminology C168.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 diffuse surface—a surface that emits or reflects equal radiation intensity, or both, in all directions (2).
3.2.2 emissive power—the rate of radiative energy emission per unit area from a surface (2).
3.2.3 emissometer—an instrument used for measurement of emittance.
3.2.4 Lambert’s cosine law—the mathematical relation describing the variation of emissive power from a diffuse surface as
varying with the cosine of the angle measured away from the normal of the surface (2).
3.2.5 normal emittance—the directional emittance perpendicular to the surface.
1
This test method is under the jurisdiction of ASTM Committee C16 on Thermal Insulation and is the direct responsibility of Subcommittee C16.30 on Thermal
Measurement.
Current edition approved Nov. 1, 2010March 1, 2015. Published January 2011June 2015. Originally approved in 1997. Last previous edition approved in 20042010 as
ε1
C1371 - 04a.C1371 - 04a(2010) . DOI: 10.1520/C1371-04AR10E01.10.1520/C1371-15.
2
The boldface numbers in parentheses refer to the list of references at the end of this standard.
3
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
C1371 − 15
3.2.6 radiative intensity—radiative energy passing through an area per unit solid angle, per unit of the area projected normal
to the direction of passage, and per unit time (2).
3.2.7 spectral—having a dependence on wavelength; radiation within a narrow region of wavelength (2).
3.2.8 specular surface—mirrorlike in reflection behavior
...