ASTM C177-19e1
(Test Method)Standard Test Method for Steady-State Heat Flux Measurements and Thermal Transmission Properties by Means of the Guarded-Hot-Plate Apparatus
Standard Test Method for Steady-State Heat Flux Measurements and Thermal Transmission Properties by Means of the Guarded-Hot-Plate Apparatus
SIGNIFICANCE AND USE
5.1 This test method covers the measurement of heat flux and associated test conditions for flat specimens. The guarded-hot-plate apparatus is generally used to measure steady-state heat flux through materials having a “low” thermal conductivity and commonly denoted as “thermal insulators.” Acceptable measurement accuracy requires a specimen geometry with a large ratio of area to thickness.
5.2 Two specimens are selected with their thickness, areas, and densities as identical as possible, and one specimen is placed on each side of the guarded-hot-plate. The faces of the specimens opposite the guarded-hot-plate and primary guard are placed in contact with the surfaces of the cold surface assemblies.
5.3 Steady-state heat transmission through thermal insulators is not easily measured, even at room temperature. This is due to the fact heat transmission through a specimen occurs by any or all of three separate modes of heat transfer (radiation, conduction, and convection). It is possible that any inhomogeneity or anisotropy in the specimen will require special experimental precautions to measure that flow of heat. In some cases it is possible that hours or even days will be required to achieve the thermal steady-state. No guarding system can be constructed to force the metered heat to pass only through the test area of insulation specimen being measured. It is possible that moisture content within the material will cause transient behavior. It is also possible that and physical or chemical change in the material with time or environmental condition will permanently alter the specimen.
5.4 Application of this test method on different test insulations requires that the designer make choices in the design selection of materials of construction and measurement and control systems. Thus it is possible that there will be different designs for the guarded-hot-plate apparatus when used at ambient versus cryogenic or high temperatures. Test thickness, temperature range,...
SCOPE
1.1 This test method establishes the criteria for the laboratory measurement of the steady-state heat flux through flat, homogeneous specimen(s) when their surfaces are in contact with solid, parallel boundaries held at constant temperatures using the guarded-hot-plate apparatus.
1.2 The test apparatus designed for this purpose is known as a guarded-hot-plate apparatus and is a primary (or absolute) method. This test method is comparable, but not identical, to ISO 8302.
1.3 This test method sets forth the general design requirements necessary to construct and operate a satisfactory guarded-hot-plate apparatus. It covers a wide variety of apparatus constructions, test conditions, and operating conditions. Detailed designs conforming to this test method are not given but must be developed within the constraints of the general requirements. Examples of analysis tools, concepts and procedures used in the design, construction, calibration and operation of a guarded-hot-plate apparatus are given in Refs (1-41).2
1.4 This test method encompasses both the single-sided and the double-sided modes of measurement. Both distributed and line source guarded heating plate designs are permitted. The user should consult the standard practices on the single-sided mode of operation, Practice C1044, and on the line source apparatus, Practice C1043, for further details on these heater designs.
1.5 The guarded-hot-plate apparatus can be operated with either vertical or horizontal heat flow. The user is cautioned however, since the test results from the two orientations may be different if convective heat flow occurs within the specimens.
1.6 Although no definitive upper limit can be given for the magnitude of specimen conductance that is measurable on a guarded-hot-plate, for practical reasons the specimen conductance should be less than 16 W/(m2K).
1.7 This test method is applicable to the measurement of a wide variety of sp...
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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.
´1
Designation: C177 − 19
Standard Test Method for
Steady-State Heat Flux Measurements and Thermal
Transmission Properties by Means of the Guarded-Hot-Plate
1
Apparatus
This standard is issued under the fixed designation C177; 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
ε NOTE—Updated 2.3 editorially in February 2023.
1. Scope however, since the test results from the two orientations may be
different if convective heat flow occurs within the specimens.
1.1 This test method establishes the criteria for the labora-
tory measurement of the steady-state heat flux through flat,
1.6 Although no definitive upper limit can be given for the
homogeneous specimen(s) when their surfaces are in contact
magnitude of specimen conductance that is measurable on a
with solid, parallel boundaries held at constant temperatures guarded-hot-plate, for practical reasons the specimen conduc-
2
using the guarded-hot-plate apparatus.
tance should be less than 16 W/(m K).
1.2 The test apparatus designed for this purpose is known as
1.7 This test method is applicable to the measurement of a
a guarded-hot-plate apparatus and is a primary (or absolute)
wide variety of specimens, ranging from opaque solids to
method. This test method is comparable, but not identical, to
porous or transparent materials, and a wide range of environ-
ISO 8302.
mental conditions including measurements conducted at ex-
tremes of temperature and with various gases and pressures.
1.3 This test method sets forth the general design require-
ments necessary to construct and operate a satisfactory
1.8 Inhomogeneities normal to the heat flux direction, such
guarded-hot-plate apparatus. It covers a wide variety of appa-
as layered structures, can be successfully evaluated using this
ratus constructions, test conditions, and operating conditions.
test method. However, testing specimens with inhomogeneities
Detailed designs conforming to this test method are not given
in the heat flux direction, such as an insulation system with
but must be developed within the constraints of the general
thermal bridges, can yield results that are location specific and
requirements. Examples of analysis tools, concepts and proce-
shall not be attempted with this type of apparatus. See Test
dures used in the design, construction, calibration and opera-
Method C1363 for guidance in testing these systems.
2
tion of a guarded-hot-plate apparatus are given in Refs (1-41).
1.9 Calculations of thermal transmission properties based
1.4 This test method encompasses both the single-sided and
upon measurements using this method shall be performed in
the double-sided modes of measurement. Both distributed and
conformance with Practice C1045.
line source guarded heating plate designs are permitted. The
1.10 In order to ensure the level of precision and accuracy
user should consult the standard practices on the single-sided
expected, persons applying this standard must possess a
mode of operation, Practice C1044, and on the line source
knowledge of the requirements of thermal measurements and
apparatus, Practice C1043, for further details on these heater
testing practice and of the practical application of heat transfer
designs.
theory relating to thermal insulation materials and systems.
1.5 The guarded-hot-plate apparatus can be operated with
Detailed operating procedures, including design schematics
either vertical or horizontal heat flow. The user is cautioned
and electrical drawings, should be available for each apparatus
to ensure that tests are in accordance with this test method. In
addition, automated data collecting and handling systems
1
This test method is under the jurisdiction of ASTM Committee C16 on Thermal
connected to the apparatus must be verified as to their
Insulation and is the direct responsibility of Subcommittee C16.30 on Thermal
accuracy. This can be done by calibration and inputting data
Measurement.
sets, which have known results associated with them, into
Current edition approved Jan. 1, 2019. Published January 2019. Originally
computer programs.
approved in 1942. Last previous edition approved in 2013 as C177 – 13. DOI:
10.1520/C0177-19E01.
2
1.11 It is not practical for a test method of this type to
The boldface numbers given in parentheses refer to the list of references at the
end of this standard. establish details of de
...
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