ASTM D6744-01
(Test Method)Standard Test Method for Determination of the Thermal Conductivity of Anode Carbons by the Guarded Heat Flow Meter Technique
Standard Test Method for Determination of the Thermal Conductivity of Anode Carbons by the Guarded Heat Flow Meter Technique
SCOPE
1.1 This test method covers a steady-state technique for the determination of the thermal conductivity of carbon materials in thicknesses of less than 25 mm. The test method is useful for homogeneous materials having a thermal conductivity in the approximate range 1 30 W/(mK), (thermal resistance in the range from 10 to 400 104 m2 K/W) over the approximate temperature range from 150 to 600 K. It can be used outside these ranges with reduced accuracy for thicker specimens and for thermal conductivity values up to 60 W/(mK).
Note 1—It is not recommended to test graphite cathode materials using this test method. Graphites usually have a very low thermal resistance, and the interfaces between the sample to be tested and the instrument become more significant than the sample itself.
1.2 This test method is similar in concept to Test Methods E 1530 and C 518. Significant attention has been paid to ensure that the thermal resistance of contacting surfaces is minimized and reproducible.
1.3 The values stated in SI units are regarded as 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.
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An American National Standard
Designation:D6744–01
Standard Test Method for
Determination of the Thermal Conductivity of Anode
Carbons by the Guarded Heat Flow Meter Technique
This standard is issued under the fixed designation D6744; 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 3.1.1 average temperature—the average temperature of a
surface is the area-weighted mean temperature of that surface.
1.1 This test method covers a steady-state technique for the
3.1.2 heat flux transducer (HFT)—adevicethatproducesan
determination of the thermal conductivity of carbon materials
electrical output that is a function of the heat flux, in a
inthicknessesoflessthan25mm.Thetestmethodisusefulfor
predefined and reproducible manner.
homogeneous materials having a thermal conductivity in the
3.1.3 thermal conductance (C)—the time rate of heat flux
approximate range 1< l < 30 W/(m·K), (thermal resistance in
−4 2
through a unit area of a body induced by unit temperature
the range from 10 to 400 3 10 m ·K/W) over the approxi-
difference between the body surfaces.
mate temperature range from 150 to 600 K. It can be used
3.1.4 thermal conductivity (l), of a solid material—thetime
outside these ranges with reduced accuracy for thicker speci-
rate of heat flow, under steady conditions, through unit area,
mens and for thermal conductivity values up to 60 W/(m·K).
per unit temperature gradient in the direction perpendicular to
NOTE 1—Itisnotrecommendedtotestgraphitecathodematerialsusing
the area.
thistestmethod.Graphitesusuallyhaveaverylowthermalresistance,and
3.1.5 thermal resistance (R)—the reciprocal of thermal
the interfaces between the sample to be tested and the instrument become
conductance.
more significant than the sample itself.
3.2 Symbols:
1.2 This test method is similar in concept to Test Methods
E1530andC518.Significantattentionhasbeenpaidtoensure
that the thermal resistance of contacting surfaces is minimized l = thermal conductivity, W/(m·K), Btu·in/(h·ft ·°F)
2 2
and reproducible. C = thermal conductance, W/(m ·K), Btu/(h·ft ·°F)
2 2
R = thermal resistance, m ·K/W, h·ft ·°F/Btu
1.3 The values stated in SI units are regarded as standard.
Dx = specimen thickness, mm, in
1.4 This standard does not purport to address all of the
2 2
A = specimen cross sectional area, m,ft
safety concerns, if any, associated with its use. It is the
Q = heat flow, W, Btu/h
responsibility of the user of this standard to establish appro-
f = heat flux transducer output, mV
priate safety and health practices and determine the applica-
N = heat flux transducer calibration constant,
bility of regulatory limitations prior to use.
2 2
W/(m ·mV), Btu/(h·ft ·mV)
2 2
Nf = heat flux, W/m , Btu/(h·ft )
2. Referenced Documents
DT = temperature difference,° C, °F
2.1 ASTM Standards:
T = temperature of guard heater, °C, °F
g
C518 Test Method for Steady-State Heat Flux Measure-
T = temperature of upper heater, °C, °F
u
ments and Thermal Transmission Properties by Means of
T = temperature of lower heater, °C, °F
l
the Heat Flow Meter Apparatus
T = temperature of one surface of the specimen, °C, °F
E1530 Test Method for Evaluating the Resistance to Ther-
T = temperature of the other surface of the specimen, °C,
mal Transmission of Thin Specimens of Materials by the
°F
Guarded Heat Flow Meter Technique
T = mean temperature of the specimen, °C, °F
m
s = unknown specimen
3. Terminology
r = known calibration or reference specimen
o = contacts
3.1 Definitions of Terms Specific to This Standard:
4. Summary of Test Method
This test method is under the jurisdiction of ASTM Committee D02 on
4.1 A specimen and a heat flux transducer (HFT) are
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee
sandwiched between two flat plates controlled at different
D02.05.0E on Properties of Fuels, Petroleum Coke and Carbon Materials.
Current edition approved Dec. 10, 2001. Published February 2002.
temperatures, to produce a heat flow through the test stack. A
Annual Book of ASTM Standards, Vol 04.06.
reproducible load is applied to the test stack by pneumatic or
Annual Book of ASTM Standards, Vol 14.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D6744
hydraulic means, to ensure that there is a reproducible contact spring loaded mechanism. In either case, means must be
resistance between the specimen and plate surfaces. A cylin- provided to ensure that the loading can be varied and set to
drical guard surrounds the test stack and is maintained at a certain values reproducibility.
uniform mean temperature of the two plates, in order to
6.2.2 The loading force must be transmitted to the stack
minimize lateral heat flow to and from the stack. At steady-
through a gimball joint (2) that allows up to 5° swivel in the
state, the difference in temperature between the surfaces
plane perpendicular to the axis of the stack.
contacting the specimen is measured with temperature sensors
6.2.3 Suitable insulator plate (3) separates the gimball joint
embeddedinthesurfaces,togetherwiththeelectricaloutputof
from the top plate (4).
the HFT. This output (voltage) is proportional to the heat flow
6.2.4 The top plate (assumed to be the hot plate for the
through the specimen, the HFT and the interfaces between the
purposes of this description) is equipped with a heater (5) and
specimen and the apparatus. The proportionality is obtained
control thermocouple (6) adjacent to the heater, to maintain a
through prior calibration of the system with specimens of
certain desired temperature. (Other means of producing and
knownthermalresistancemeasuredunderthesameconditions,
maintaining temperature may also be used as long as the
suchthatcontactresistanceatthesurfaceismadereproducible.
requirements under 6.3 are met.) The construction of the top
plate is such as to ensure uniform heat distribution across its
5. Significance and Use
face contacting the sample (8). Attached to this face (or
5.1 This test method is designed to measure and compare
embedded in close proximity to it), in a fashion that does not
thermalpropertiesofmaterialsundercontrolledconditionsand
interfere with the sample/plate interface, is a temperature
their ability to maintain required thermal conductance levels.
sensor (7) (typically a thermocouple, thermistor) that defines
the temperature of the interface on the plate side.
6. Apparatus
6.2.5 The sample (8) is in direct contact with the top plate
6.1 Aschematicrenderingofatypicalapparatusisshownin
on one side and an intermediate plate (9) on the other side.
Fig. 1. The relative position of the HFT to sample is not
6.2.6 The intermediate plate (9) is an optional item. Its
important(itmaybeonthehotorcoldside)asthetestmethod
purpose is to provide a highly conductive environment to the
is based on maintaining axial heat flow with minimal heat
second temperature sensor (10), to obtain an average tempera-
losses or gains radially. It is also up to the designer whether to
ture of the surface. If the temperature sensor (10) is embedded
choose heat flow upward or downward or horizontally, al-
into the face of the HFT, or other means are provided to define
though downward heat flow in a vertical stack is the most
the temperature of the surface facing the sample, the use of the
common one.
intermediate plate is not mandatory.
6.2 Key Components of a Typical Device:
6.2.1 The compressive force for the stack is to be provided 6.2.7 Heat flux transducer (HFT) is a device that will
by either a regulated pneumatic or hydraulic cylinder (1) or a generate an electrical signal in proportion to the heat flux
FIG. 1 Key Components of a Typical Device
D6744
across it. The level of output required (sensitivity) greatly the specimen DT is not less than 3 °C.Adjust the guard heater
depends on the rest of the instrumentation used to read it. The temperature (T ) such that it is at approximately the average of
g
overallperformanceoftheHFTanditsreadoutinstrumentation T and T.
u l
shall be such as to meet the requirements in Section 13. 9.2 Selectatleasttwocalibrationspecimenshavingthermal
6.2.8 The lower plate (12) is constructed similarly to the
resistance values that bracket the range expected for the test
upper plate (4), except it is positioned as a mirror image. specimens at the temperature conditions required.
6.2.9 An insulator plate (16) separates the lower plate (12)
9.3 Table 1 contains a list of several available materials
from the heat sink (17). In case of using circulating fluid in
commonly used for calibration, together with corresponding
placeofaheater/thermocouplearrangementintheupperand/or
thermal resistance (R ) values for a given thickness. This
s
lower plates, the heat sink may or may not be present.
information is provided to assist the user in selecting optimum
6.2.10 The entire stack is surrounded by a cylindrical guard
specimenthicknessfortestingamaterialandindecidingwhich
(18) equipped with a heater (19) and a control thermocouple
calibration specimens to use.
(20) to maintain it at the mean temperature between the upper
9.4 The range of thermal conductivity for which this test
and lower plates.Asmall, generally unfilled gap separates the
method is most suitable is such that the optimum thermal
−4 −4 −2
guard from the stack. For instruments limited to operate in the
resistance range is from 10 3 10 to 400 3 10 m ·K/W.
ambient region, no guard is required. A draft shield is recom-
The most commonly used calibration materials are the Pyrex
mended in place of it.
7740, Pyroceram 9606, and stainless steel.
9.5 Measure the thickness of the specimen to 25 µm.
NOTE 2—It is permissible to use thin layers of high conductivity grease
or elastomeric material on the two surfaces of the sample to reduce the 9.6 Coatbothsurfacesofacalibrationspecimenwithavery
thermal resistance of the interface and promote uniform thermal contact
thin layer of a compatible heat sink compound or place a thin
across the interface area.
layer of elastomeric heat transfer medium on it to help
NOTE 3—The cross sectional area of the sample may be any, however,
minimize the thermal resistance at the interfaces of adjacent
most commonly circular and rectangular cross sections are used. Mini-
contacting surfaces.
mum size is dict
...
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