ASTM C835-01
(Test Method)Standard Test Method for Total Hemispherical Emittance of Surfaces up to 1400°C
Standard Test Method for Total Hemispherical Emittance of Surfaces up to 1400°C
SCOPE
1.1 This calorimetric test method covers the determination of total hemispherical emittance of metal and graphite surfaces and coated metal surfaces up to approximately 1400°C. The upper-use temperature is limited only by the characteristics (for example, melting temperature, vapor pressure) of the specimen and the design limits of the test facility. This test method has been demonstrated for use up to 1400°C.
1.2 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. For specific hazard statements, see Section 7.
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Designation: C 835 – 01
Standard Test Method for
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Total Hemispherical Emittance of Surfaces up to 1400°C
This standard is issued under the fixed designation C835; 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 (e) indicates an editorial change since the last revision or reapproval.
−8 2 4
1. Scope
= 5.669 310 W/m ·K ,
Q = heat flow rate, W,
1.1 This calorimetric test method covers the determination
T = temperature of heated specimen, K,
oftotalhemisphericalemittanceofmetalandgraphitesurfaces 1
T = temperature of bell jar inner surface, K,
2
and coated metal surfaces up to approximately 1400°C. The
A = surface area of specimen over which heat generation
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upper-usetemperatureislimitedonlybythecharacteristics(for
2
is measured, m ,
example,meltingtemperature,vaporpressure)ofthespecimen
2
A = surface area of bell jar inner surface, m ,
2
and the design limits of the test facility. This test method has
F = the gray body shape factor, which includes the effect
been demonstrated for use up to 1400°C.
of geometry and the departure of real surfaces from
1.2 This standard does not purport to address all of the
blackbody conditions, dimensionless, and
safety concerns, if any, associated with its use. It is the
2
Pa = absolute pressure, pascal (N/m ). One pascal is
responsibility of the user of this standard to establish appro-
equivalent to 0.00750 mm Hg.
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use. For specific hazard
4. Summary of Test Method
statements, see Section 7.
4.1 Astrip specimen of the material, approximately 13 mm
wide and 250 mm long, is placed in an evacuated chamber and
2. Referenced Documents
is directly heated with an electric current to the temperature at
2.1 ASTM Standards:
which the emittance measurement is desired. The power
C168 Terminology Relating to Thermal Insulating Materi-
dissipated over a small central region of the specimen and the
2
als
temperature of this region are measured. Using the Stefan-
E230 Temperature-Electromotive Force (EMF) Tables for
Boltzmannequation,thispowerisequatedtotheradiativeheat
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Standardized Thermocouples
transfer to the surroundings and, with the measured tempera-
E691 Practice for Conducting an Interlaboratory Study to
ture, is used to calculate the value of the total hemispherical
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Determine the Precision of a Test Method
emittance of the specimen surface.
3. Terminology
5. Significance and Use
3.1 Definitions—The terms and symbols are as defined in
5.1 The emittance as measured by this test method can be
Terminology C168 with exceptions included as appropriate.
used in the calculation of radiant heat transfer from surfaces
3.2 Symbols:
that are representative of the tested specimens, and that are
within the temperature range of the tested specimens.
5.2 This test method can be used to determine the effect of
e = error in the variable i, 6 %,
i
service conditions on the emittance of materials. In particular,
e = total hemispherical emittance of heated specimen,
1
the use of this test method with furnace exposure (time at
dimensionless,
e = total hemispherical emittance of bell jar inner sur- temperature) of the materials commonly used in all-metallic
2
face, dimensionless, insulationscandeterminetheeffectsofoxidationonemittance.
s = Stefan-Boltzmann constant,
5.3 The measurements described in this test method are
conducted in a vacuum environment. Usually this condition
will provide emittance values that are applicable to materials
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used under other conditions, such as in an air environment.
ThistestmethodisunderthejurisdictionofASTMCommitteeC16onThermal
Insulation and is the direct responsibility of Subcommittee C16.30 on Thermal
However, it must be recognized that surface properties of
Measurements.
materials used in air or other atmospheres may be different. In
Current edition approved Nov. 10, 2001. Published January 2002. Originally
addition, preconditioned surfaces, as described in 5.2, may be
published as C835–76. Last previous edition C835–00.
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Annual Book of ASTM Standards, Vol 04.06. altered in a vacuum environment because of vacuum stripping
3
Annual Book of ASTM Standards, Vol 14.03.
of absorbed gases and other associated vacuum effects. Thus,
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Annual Book of ASTM Standards, Vol 14.02.
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C 835
emittancesmeasuredundervacuummayhavevaluesthatdiffer other readout, vacuum system, and specimen holders. A
from those that exist in air, and the user must be aware of this schematic of
...
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