ASTM C1114-00

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Designation: C 1114 – 00
Standard Test Method for
Steady-State Thermal Transmission Properties by Means of
the Thin-Heater Apparatus
This standard is issued under the fixed designation C1114; 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.
1. Scope of less than 2% may be considered insignificant, and the
requirements fulfilled.
1.1 Thistestmethodcoversthedeterminationofthesteady-
1.5 The specimens shall meet one of the following require-
state thermal transmission properties of flat-slab specimens of
ments, in addition to those of 1.4.
thermalinsulationusingathinheaterofuniformpowerdensity
1.5.1 If homogeneous materials as defined in Terminology
having low lateral heat flow. A thin heater with low lateral
C168 are tested, then the thermal resistivity and thermal
thermalconductancecanreduceunwantedlateralheatflowand
conductivity can be determined by this test method.
avoid the need for active-edge guarding.
1.5.2 If materials which are layered or otherwise thermally
1.2 This primary test method of thermal-transmission mea-
inhomogeneous are tested, thermal resistance and thermal
surement describes a principle, rather than a particular appa-
conductance can be determined by this test method.
ratus. The principle involves determination of the thermal flux
1.6 Two versions of thin-heater apparatus using the same
across a specimen of known thickness and the temperatures of
principleofthestandardaredescribedinAnnexA1andAnnex
the hot and cold faces of the specimen.
A2. They are similar in concept but differ in size and
1.3 Considerable latitude is given to the designer of the
construction, and hence warrant separate descriptions for each
apparatus in this test method; since a variety of designs is
design. This test method in no way limits the size of the
possible, a procedure for qualifying an apparatus is given in
thin-heater element. One of the units described uses a thin
5.3.
metal foil, while the other uses a metal screen as the heat
1.4 The specimens must meet the following conditions if
source. The smaller, foil apparatus is designed to make rapid
thermalresistanceorthermalconductanceofthespecimenisto
measurements of heat transmission through specimens as thin
be determined by this test method :
as 0.5 cm and as thick as 2 cm; however, an apparatus using a
1.4.1 The portion of the specimen over the isothermal area
foil heater could be designed to measure much thicker mate-
of the heater must accurately represent the whole specimen.
rials, if desired. The larger, screen apparatus is designed to
1.4.2 The remainder of the specimen should not distort the
measure specimens with thicknesses between 3 and 15 cm,
heat flow in that part of the specimen defined in 1.4.1.
where the exact limits depend on the thermal resistance of the
1.4.3 The specimen shall be thermally homogeneous such
specimens. Both apparatuses use thermocouples for measuring
that the thermal conductivity is not a function of the position
temperature, but other temperature-sensing systems can be
within the sample, but rather may be a function of direction,
used.
time, and temperature. The specimen shall be free of holes, of
1.7 This test method covers the theory and principles of the
high-density volumes, and of thermal bridges between the test
measurementtechnique.Itdoesnotprovidedetailsofconstruc-
surfaces or the specimen edges.
tion other than those required to illustrate two devices which
1.4.4 Test Method C177 describes tests that can help
meet the prescribed requirements. Detailed information is
ascertain whether conditions of 1.4 are satisfied. For the
available in References (1-23) and the Adjunct.
purposes of this test method, differences in the measurements
1.8 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
ThistestmethodisunderthejurisdictionofASTMCommitteeC16onThermal responsibility of the user of this standard to establish appro-
Insulation and is the direct responsibility of Subcommittee C16.30 on Thermal
priate safety and health practices and determine the applica-
Measurement.
bility of regulatory limitations prior to use.
Current edition approved Oct. 10, 1998. Published January 2001. Originally
published as C1114–89. Last previous edition C1114–98.
Further discussion on the definition of these limitations may be found in Tye,
R. P., “What Property Do We Measure?,” Heat Transmission Measurements in Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
Thermal Insulations, ASTM STP 544, ASTM, 1974, pp 5–12. this test method.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
C 1114
2. Referenced Documents dimensional, longitudinal flow of heat perpendicular to the
heater is obtained through the specimen. Because the foil or
2.1 ASTM Standards:
screen heater is very thin, the need for a gap between the inner
C168 Terminology Relating to Thermal Insulating Materi-
and outer heater regions to act respectively as hot-plate and
als
guard, is unnecessary.
C177 Test Method for Steady-State Heat Flux Measure-
ments and Thermal Transmission Properties by Means of
5. Significance and Use
the Guarded-Hot-Plate Apparatus
5.1 Factors that may influence the thermal-transmission
C518 Test Method for Steady-State Heat Flux Measure-
ments and Thermal Transmission Properties by Means of properties of a specimen of material are described in Practice
C1045 and the Precision and Bias section of Test Method
the Heat Flow Meter Apparatus
C687 PracticeforDeterminationoftheThermalResistance C177.
5.2 Because of the required test conditions prescribed by
of Loose-Fill Building Insulation
C1043 Practice for Guarded-Hot-Plate Design Using Cir- this test method, it shall be recognized that the thermal
properties obtained will not necessarily apply without modifi-
cular Line-Heat Sources
C1044 PracticeforUsingtheGuarded-Hot-PlateApparatus cation to all conditions of service. As an example, this test
intheOne-SidedModetoMeasureSteady-StateHeatFlux method normally provides that the thermal properties shall be
and Thermal Transmission Properties obtained on specimens that do not contain moisture, although
C 1045 Practice for Calculating Thermal Transmission in service such conditions may not be realized. Even more
Properties from Steady-State Heat Flux Measurements basic is the dependence of the thermal properties on variables
C1058 Practice for Selecting Temperatures for Reporting such as mean temperature and temperature difference.
and Evaluating Thermal Properties of Thermal Insulation 5.3 Whenanewormodifieddesignofapparatusisevolved,
tests shall be made on at least two sets of differing material of
NOTE 1—Consult Test Methods C177, C518, and Practice C1045 for
knownlong-termthermalstability.Testsshallbemadeforeach
the correct application of this test method.
material at a minimum of two different mean temperatures
E177 Practice for Use of the Terms Precision and Bias in
within the operating range of each. Any differences in results
ASTM Test Methods
should be carefully studied to determine the cause and then be
2.2 ASTM Adjuncts:
removed by appropriate action. Only after a successful verifi-
Descriptions of Two Types of Thin-Heater Apparatus
cation study on materials having known thermal properties
traceable to a recognized national standards laboratory shall
3. Terminology
test results obtained with this apparatus be considered to
3.1 Applicable terms and symbols are defined in Terminol-
conform with this test method. Periodic checks of apparatus
ogy C168. Any terms or symbols not included in C168 but
performance are recommended.
used in this test method will be defined within the text.
5.4 The thermal transmission properties of many materials
depend upon the prior thermal history. Care must be exercised
4. Summary of Test Method
when testing such specimens at a number of conditions so that
4.1 Principles:
testsareperformedinasequencethatlimitssucheffectsonthe
4.1.1 Athin-foil or metal-screen heating apparatus operates
results.
in accordance with the basic concept of a unidimensional,
5.5 Typical uses for the thin-heater apparatus include the
longitudinal heat-flow technique. The heater is made suffi-
following:
ciently thin so that lateral heat flow along the plane of the
5.5.1 Product development and quality control applications.
heater is insignificant, and so that there is no need for isolation
5.5.2 Measurement of thermal conductivity at desired mean
and separate temperature control of a guard region, except
temperatures.
possibly the control of ambient temperature.
5.5.3 Thermal properties of specimens that are moist or
4.1.2 The low mass of the thin heater apparatus minimizes
close to melting point or other critical temperature (see Note
drift error and allows the apparatus to reach steady-state in a
2).
significantly shorter time than a typical Test Method C177
NOTE 2—Apparatusofthetypecoveredbythistestmethodapplytothe
apparatus.
study of thermal properties of specimens containing moisture because of
4.1.3 It should be noted that all quantities in this procedure
the use of small temperature differences and the low thermal capacity of
are determined by direct measurement. There are no arbitrary
the heat source.
factors requiring calibration by comparison with a standard:
5.5.4 Determination of thermal properties of relatively high
thus, the apparatus yields results on an absolute basis.
R value insulation samples with large apparatuses. In the case
4.1.4 Aproperly designed heater will be sufficiently thin to
of the metal-screen heater apparatus, samples with thicknesses
reduce lateral heat flow from the central zone to an acceptably
up to 15 cm can be measured.
small level. The result is that within a central zone, one-
6. Apparatus and Specimen Preparation
6.1 The simplicity of this test procedure may cause very
Annual Book of ASTM Standards, Vol 04.06.
important factors to be overlooked which may affect the
Annual Book of ASTM Standards, Vol 14.02.
Order PCN:12–311140–61 from ASTM Headquarters. results. To ensure accuracy of measurements, the user of this
C 1114
apparatusshouldknowhowtomeasuretemperatureandpower heater area. For more specific quantitative information on this
as they relate to testing of thermal resistance. It is also limitation see Refs. (24), (25), (26), and (27).
necessarythatthespecimensbeproperlyselectedandprepared
7.2.1.1 The specimen may be sized to extend beyond the
for evaluation.
meteredareabyadistancesufficienttoensureone-dimensional
6.2 Normally, test specimens are selected in pairs from the
heat flow within the metered area.
sample lot. The specimens selected should be uniform and
7.2.2 Homogeneity— There are two potential problems in
homogeneous to ensure that test apparatus symmetry is main-
determining the heat flux through highly inhomogeneous
tained. Appropriate thermal modeling may allow tests of
specimens. One is related to the interpretation and application
nonuniform specimens, such as small specimens positioned
of the resulting data; it is discussed in Practice C1045. The
within larger ones, or composite or layered specimens.
other is connected with the degradation in performance of the
6.3 Test specimens shall be prepared and conditioned in
apparatus. If the specimen itself is highly inhomogeneous, that
accordance with the appropriate material specification. The
is, the heat flux density varies appreciably over the metered
conditioning of the test specimens shall be reported.
area, several errors can be significantly increased. The tem-
6.3.1 The surfaces of the specimens shall be prepared to
perature distribution of the thin heater can deviate appreciably
ensure uniform thermal contact with the heater and
from isothermal conditions which, in turn, can cause large
temperature-controlled plates. Further details may be found in
uncertainties in the average temperature difference across the
the Specimen Preparation section of Test Method C177.
specimen. The increased temperature variations of the thin
6.3.2 When evaluating compressible specimens, provide
heater can also lead to increased edge heat losses. The
means to maintain a definite, known test thickness. One
importance of measuring temperatures of the thin heater or
method is to insert rigid equal-length spacers made of low
specimensurfaceatnumerouspointsisgreatlyincreasedunder
thermal-conductivity material in the corners of specimens.An
such conditions.
alternative method involves using mechanical arrangements to
7.3 Specimen Preparation and Installation—The specimen
establishfixedandknownspacingandparallelismbetweenthe
shall be conditioned in accordance with the appropriate mate-
heater and cold plates.
rial specification. The following guidelines for specimen
6.3.3 The maximum allowable distance between the heater
preparationapplywhenthematerialspecificationisincomplete
andcoldplates(specimenthickness)islimitedbythespecimen
or unavailable. In general, the surfaces of the specimen should
thermal resistance, the ambient temperature, and the ratio of
be prepared to ensure uniform thermal contact with the thin
measurement area to apparatus size. The isothermal area
heater and the cooling plates.
established in the center of the heater is influenced by these
7.3.1 Compressible Specimens—Also, for compressible
factors. The isothermal area must be large enough to establish
specimensthesurfacesoftheuncompressedspecimensmaybe
the equilibrium heat flux (W/m ) through a representative area
comparatively rough so long as these undulations essentially
of the specimen. References are presented which will help
vanish under test compression. Under more extreme condi-
guide users in determining the maximum thickness that can be
tions, it may be necessary to smooth the specimen surfaces to
used for specimens in their apparatus.
achieve better specimen contact. If the apparent thermal
6.4 Thedistancebetweentheheaterandthecoldplatesmust
conductivity of the contact void is greater than that of the
beadjustedtoconfinethespecimenswithpressuresufficientto
specimen, the measured R value will be smaller than the R
ensure good thermal contact between the specimens and the
valuethatwouldbeobtainedifthevoidswereabsent.Thismay
bounding surfaces. For rigid specimens, a pressure of 2.5 kPa
often be the case at higher temperatures where radiant heat
is recommended. For compressible specimens, see 6.3.2.
transfer predomina
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