ASTM C1044 - 24

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Designation: C1044 −24
Standard Practice for
Using a Guarded-Hot-Plate Apparatus or Thin-Heater
Apparatus in the Single-Sided Mode
1
This standard is issued under the ﬁxed designation C1044; 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. Scope
1.1 This practice covers the determination of the steady-
state heat ﬂow through the meter section of a specimen when
a guarded-hot-plate apparatus or thin-heater apparatus is used
in the single-sided mode of operation.
1.2 This practice provides a supplemental procedure for use
in conjunction with either Test Method C177 or C1114 for
testing a single specimen. This practice is limited to only the
single-sided mode of operation, and, in all other particulars, the
requirements of either Test Method C177 or C1114 apply.
NOTE 1—Test Methods C177 and C1114 describe the use of the
guarded-hot-plate and thin-heater apparatus, respectively, for determining
steady-state heat ﬂux and thermal transmission properties of ﬂat-slab
specimens. In principle, these methods cover both the double- and
single-sided mode of operation, and at present, do not distinguish between
the accuracies for the two modes of operation. When appropriate, thermal
transmission properties shall be calculated in accordance with Practice
C1045.
1.3 This practice requires that the cold plates of the appa-
ratus have independent temperature controls. For the single-
sided mode of operation, a (single) specimen is placed between
the hot plate and the cold plate. Auxiliary thermal insulation, if
needed, is placed between the hot plate and the auxiliary cold
plate. The auxiliary cold plate and the hot plate are maintained
at the same temperature. The heat ﬂow from the meter plate is
assumed to ﬂow only through the specimen, so that the thermal
transmission properties correspond only to the specimen.
NOTE 2—The double-sided mode of operation requires similar speci-
mens placed on either side of the hot plate. The cold plates that contact the
outer surfaces of these specimens are maintained at the same temperature.
The electric power supplied to the meter plate is assumed to result in equal
heat ﬂow through the meter section of each specimen, so that the thermal
transmission properties correspond to an average for the two specimens.
1.4 This practice does not preclude the use of a guarded-
hot-plate apparatus in which the auxiliary cold plate is either
larger or smaller in lateral dimensions than either the test
specimen or the cold plate.
NOTE 3—Most guarded-hot-plate apparatus are designed for the double-
sided mode of operation (1).
2
Consequently, the cold plate and the
auxiliary cold plate are the same size and the specimen and the auxiliary
insulation will have the same lateral dimensions, although the thicknesses
need not be the same. Some guarded-hot-plate apparatus, however, are
designed speciﬁcally for testing only a single specimen that is either larger
or smaller in lateral dimensions than the auxiliary insulation or the
auxiliary cold plate.
1.5 This practice is suitable for use for both low- and
high-temperature conditions.
1.6 This practice shall not be used when operating an
apparatus in a double-sided mode of operation with a known
and unknown specimen, that is, with the two cold plates at
similar temperatures so that the temperature differences across
the known and unknown specimens are similar.
1.7 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 appro-
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
1.8 This international standard was developed in accor-
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
3
C168 Terminology Relating to Thermal Insulation
3
C177 Test Method for Steady-State Heat Flux Measure-
ments and Thermal Transmission Properties by Means of
the Guarded-Hot-Plate Apparatus
C518 Test Method for Steady-State Thermal Transmission
Properties by Means of the Heat Flow Meter Apparatus
C1045 Practice for Calculating Thermal Transmission Prop-
erties Under Steady-State Conditions
1
This practice 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 March 1, 2024. Published March 2024. Originally
approved in 1985. Last previous edition approved in 2020 as C1044 – 16 (2020).
DOI: 10.1520/C1044-24.
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 service@astm.org. 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
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

C1114 Test Method for Steady-State Thermal Transmission
Properties by Means of the Thin-Heater Apparatus
2.2 BIPM Standard:
4
BIPM JCGM 100: 2008 Evaluation of measurement data –
Guide to the expression of uncertainty in measurement
(GUM)
3. Terminology
3.1 Deﬁnitions—For deﬁnitions of terms used in this
practice, refer to Terminology C168. For deﬁnitions of terms
relating to the guarded-hot-plate apparatus or thin-heater ap-
paratus refer to Test Methods C177 or C1114, respectively.
3.2 Deﬁnitions of Terms Speciﬁc to This Standard:
3.2.1 auxiliary cold plate, n—the plate that provides an
isothermal boundary at the outside surface of the auxiliary
insulation.
3.2.2 auxiliary insulation, n—thermal insulation used in
place of a second test specimen, when the single-sided mode of
operation is used (syn. dummy specimen).
3.2.3 cold plate, n—the plate that provides an isothermal
boundary at the cold surface of the specimen.
3.2.4 double-sided mode, n—operation of the apparatus,
such that the heat input to the meter plate ﬂows equally through
two specimens, each specimen placed on either side of the hot
plate (see also single-sided mode).
3.2.5 gap, n—separation between the meter plate and guard
plate, usually ﬁlled with a gas or thermal insulation.
3.2.6 guard plate, n—the outer (rectangular or circular) ring
of the guarded hot plate, that encompasses the meter plate and
promotes one-dimensional heat ﬂow normal to the meter plate.
3.2.7 guarded hot plate, n—an assembly, consisting of a
meter plate and a co-planar, concentric guard plate, that
provides the heat input to the specimen(s).
3.2.8 meter plate, n—the inner (rectangular or circular) plate
of the guarded hot plate, that provides the heat input to the
meter section of the specimen(s).
3.2.9 meter section, n—the portion of the specimen (or
auxiliary insulation) through which the heat input to the meter
plate ﬂows under ideal guarding conditions.
3.2.10 single-sided mode, n—operation of the apparatus
such that essentially all of the heat input to the meter plate
ﬂows through a specimen placed on one side of the hot plate
(see also double-sided mode).
3.2.11 thin heater, n—an assembly, consisting of an unpar-
titioned thin-screen heater or thin-foil, that provides the heat
input to the specimen(s).
3.3 Symbols—The symbols used in this practice have the
following signiﬁcance. The prime (') denotes quantities asso-
ciated with the auxiliary insulation used to control heat from
the other side of the hot plate.
3.3.1 A—meter section area normal to heat ﬂow, m
2
.
3.3.2 C'—thermal conductance of auxiliary insulation,
W/(m
2
•K).
3.3.3 Q—heat ﬂow rate through meter section of specimen,
W.
3.3.4 Q'—heat ﬂow rate through meter section of auxiliary
insulation, W.
3.3.5 Q
m
—power input to meter plate, W.
3.3.6 T
c
—surface temperature of cold plate, K.
3.3.7 T'
c
—surface temperature of auxiliary cold plate, K.
3.3.8 T
h
—surface temperature of hot plate in contact with
specimen, K.
3.3.9 T'
h
—surface temperature of hot plate in contact with
auxiliary insulation, K.
4. Signiﬁcance and Use
4.1 This practice provides a procedure for operating the
apparatus so that the heat ﬂow, Q', through the meter section of
the auxiliary insulation is small; determining Q'; and, calculat-
ing the heat ﬂow, Q, through the meter section of the specimen.
4.2 This practice requires that the apparatus have indepen-
dent temperature controls in order to operate the cold plate and
auxiliary cold plate at different temperatures. In the single-
sides mode, the apparatus is operated with the temperature of
the auxiliary cold plate maintained at the same temperature of
the hot plate face adjacent to the auxiliary insulation.
NOTE 4—In principle, if the temperature difference across the auxiliary
insulation is zero and there are no edge heat losses or gains, all of the
power input to the meter plate will ﬂow through the specimen. In practice,
a small correction is made for heat ﬂow, Q', through the auxiliary
insulation.
4.3 The thermal conductance, C’, of the auxiliary insulation
shall be determined from one or more separate tests using
either Test Method C177,C1114, or as indicated in 5.4. Values
of C’ shall be checked periodically, particularly when the
temperature drop across the auxiliary insulation less than 1 %
of the temperature drop across the test specimen.
4.4 This practice is used when it is necessary to determine
the thermal properties of a single specimen. For example, the
thermal properties of a single specimen are used to calibrate a
heat-ﬂow-meter apparatus for Test Method C518.
5. Procedure for Single-Sided Mode of Operation
5.1 Refer to Fig. 1 for a schematic diagram of the single-
sided mode of operation of the guarded-hot-plate apparatus.
NOTE 5—The schematic diagram for a thin-heater apparatus (not
shown) is similar, except the hot plate is much thinner and is not
partitioned by a gap.
5.2 Follow the procedure of either Test Method C177 or
C1114 with the following modiﬁcations.
5.3 Select a rigid or semi-rigid material for the auxiliary
insulation having a low thermal conductance so that heat gains
or losses from the face of the meter plate in contact with the
auxiliary insulation will be small. The thickness and lateral
conductance of the auxiliary insulation shall be small to avoid
signiﬁcant effects on the heat transfer through the meter section
of the auxiliary insulation due to heat transfer at the edge of the
auxiliary insulation.
NOTE 6—The inﬂuence of edge effects for a particular apparatus and
test conﬁguration is determined experimentally as described in Test
4
Available from BIPM, https://www.bipm.org/en/.
C1044 − 24
2

Method C177 or by computation using one of the procedures referenced
in Test Method C177 or described by Peavy and Rennex (2).
5.4 Determine C’ of the auxiliary insulation over the tem-
perature range of interest using one of the following proce-
dures: (1) Test Method C177 or C1114 in a separate test setup
for a matched pair of similar specimens; or (2) in-situ as
described in Annex A1.
5.4.1 In the ﬁrst instance, using either Test Method C177 or
C1114, a matched pair of similar specimens is required so that
either single specimen subsequently is suitable for use as the
auxiliary insulation.
5.4.2 In the second instance using in-situ as described in
Annex A1, successive tests are required, one with a small
temperature difference across the test specimen and one with a
small temperature difference across the auxiliary insulation.
NOTE 7—In 5.4 the user is not required to determine values for C’ for
every test that will be conducted. Rather, determine C’as a function of
temperature over the temperature range of interest so that a corresponding
regression curve is developed for subsequent testing.
5.5 When using a compressible material as the auxiliary
insulation, determine C’either at the same thickness as that
used in the single-sided mode of operation or compressed to (at
least) two slightly different thicknesses, thus allowing interpo-
lation for the thickness actually used in the single-sided mode
of operation.
5.5.1 For an apparatus without a separate provision for
determining the individual thicknesses of the two specimens on
opposite sides of the hot plate, place three or more low-
conductance rigid spacers near the outer periphery of the guard
plate between the hot plate and the surface of the auxiliary cold
plate.
5.5.2 Compute the effective thickness of the test specimen
by subtracting the thickness of the rigid spacers (corrected for
thermal expansion, if necessary) from the thickness that is
determined for the test specimen plus the auxiliary insulation.
In this case, the separate tests of thermal conductance accord-
ing to 5.4.2 shall be conducted with rigid spacers.
5.6 Maintain the cold plate at the required temperature T
c
.
Provide power input to the hot plate to attain the required
temperature T
h
on the hot side of the test specimen.
5.7 Maintain the temperature T'
c
as closely as practical to
the temperature T'
h
.
5.8 Establish thermal steady-state conditions in accordance
with either Test Method C177 or C1114.
5.9 Acquire the required test data and determine A, Q
m
, T
h
,
T'
h
,and T'
c
in accordance with either Test Method C177 or
C1114.
6. Calculation
6.1 Calculate the heat ﬂow through the auxiliary insulation
as follows:
Q'5C'A
~
T'
h
2T'
c
!
(1)
where:
C’is the thermal conductance of the auxiliary insulation at a
temperature corresponding to (T'
h
+ T'
c
)/2, as obtained accord-
ing to 5.4.
6.2 Calculate the heat ﬂow through the specimen as follows:
Q5Q
m
2Q' (2)
6.3 Use the value of Q, thus obtained to calculate steady-
state thermal transmission properties, in accordance with either
Test Method C177 or C1114. When appropriate, consult
Practice C1045 to calculate steady-state thermal transmission
properties. For reference, calculation equations are provided in
Appendix X1.
7. Sources of Experimental Error
7.1 Errors in the determination of Q, are introduced from
several sources, including measurement of the power input Q
m
FIG. 1 Diagram Illustrating Single-Sided Mode of Operation of the Guarded-Hot-Plate Apparatus
C1044 − 24
3

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摘要：

ASTM C1044 - 24 是一项由美国材料与试验协会发布的最新版本标准，专门用于热流计法测量稳态热传递特性的标准化测试程序。该标准详细规定了在实验室条件下通过热流传感器测定建筑材料、隔热层及复合构件热阻与导热系数的操作流程、设备校准要求及数据计算方法，旨在确保不同测试机构间结果的可比性与重复性。适用于建筑节能评估、工业保温材料性能验证及科研领域中的热物理参数分析，尤其对满足国际建筑规范与能效标准具有重要参考价值。用户可通过该标准获取精确的热传递数据，优化材料选择与建筑热工设计，降低能源消耗

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