ASTM D6744-06(2011)e1

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
´1
Designation: D6744 − 06 (Reapproved 2011)
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 (´) indicates an editorial change since the last revision or reapproval.
ε NOTE—Update wording in Notes 1–4, 6.3.2, 12.1.8, and updated notation in Section 13 editorially in August 2011.
1. Scope E1530Test Method for Evaluating the Resistance to Ther-
mal Transmission of Materials by the Guarded Heat Flow
1.1 This test method covers a steady-state technique for the
Meter Technique
determination of the thermal conductivity of carbon materials
inthicknessesoflessthan25mm.Thetestmethodisusefulfor
3. Terminology
homogeneous materials having a thermal conductivity in the
approximate range 1< λ < 30 W/(m·K), (thermal resistance in
3.1 Definitions of Terms Specific to This Standard:
−4 2
the range from 10 to 400 × 10 m ·K/W) over the approxi-
3.1.1 average temperature, n—the average temperature of a
mate temperature range from 150 to 600 K. It can be used
surface is the area-weighted mean temperature of that surface.
outside these ranges with reduced accuracy for thicker speci-
3.1.2 heat flux transducer, HFT, n—a device that produces
mens and for thermal conductivity values up to 60 W/(m·K).
an electrical output that is a function of the heat flux, in a
predefined and reproducible manner.
NOTE1—Itisnotrecommendedtotestgraphitecathodematerialsusing
thistestmethod.Graphitesusuallyhaveaverylowthermalresistance,and
3.1.3 thermal conductance, C, n—the time rate of heat flux
the interfaces between the specimen to be tested and the instrument
through a unit area of a body induced by unit temperature
become more significant than the specimen itself.
difference between the body surfaces.
1.2 This test method is similar in concept to Test Methods
3.1.4 thermal conductivity, λ, of a solid material, n—the
E1530 and C518. Significant attention has been paid to ensure
time rate of heat flow, under steady conditions, through unit
that the thermal resistance of contacting surfaces is minimized
area,perunittemperaturegradientinthedirectionperpendicu-
and reproducible.
lar to the area.
1.3 The values stated in SI units are regarded as standard.
3.1.5 thermal resistance, R, n—the reciprocal of thermal
The values given in parentheses are for information only.
conductance.
1.4 This standard does not purport to address all of the
3.2 Symbols:
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
λ = thermal conductivity, W/(m·K), Btu·in/(h·ft ·°F)
priate safety and health practices and determine the applica-
2 2
C = thermal conductance, W/(m ·K), Btu/(h·ft ·°F)
bility of regulatory limitations prior to use.
2 2
R = thermal resistance, m ·K/W, h·ft ·°F/Btu
∆x = specimen thickness, mm, in
2. Referenced Documents
2 2
A = specimen cross sectional area, m,ft
2.1 ASTM Standards:
Q = heat flow, W, Btu/h
C518Test Method for Steady-State Thermal Transmission φ = heat flux transducer output, mV
N = heat flux transducer calibration constant, W/(m ·mV),
Properties by Means of the Heat Flow Meter Apparatus
Btu/(h·ft ·mV)
2 2
Nφ = heat flux, W/m , Btu/(h·ft )
This test method is under the jurisdiction of ASTM Committee D02 on ∆T = temperature difference,° C, °F
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
T = temperature of guard heater, °C, °F
g
SubcommitteeD02.05onPropertiesofFuels,PetroleumCokeandCarbonMaterial.
T = temperature of upper heater, °C, °F
u
Current edition approved May 1, 2011. Published August 2011. Originally
T = temperature of lower heater, °C, °F
l
approved in 2001. Last previous edition in 2006 as D6744–06. DOI: 10.1520/
T = temperature of one surface of the specimen, °C, °F
D6744-06R11. 1
For referenced ASTM standards, visit the ASTM website, www.astm.org, or T = temperature of the other surface of the specimen, °C,
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
°F
Standards volume information, refer to the standard’s Document Summary page on
T = mean temperature of the specimen, °C, °F
m
the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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D6744 − 06 (2011)
important(itmaybeonthehotorcoldside)asthetestmethod
s = unknown specimen
is based on maintaining axial heat flow with minimal heat
r = known calibration or reference specimen
losses or gains radially. It is also up to the designer whether to
o = contacts
choose heat flow upward or downward or horizontally, al-
4. Summary of Test Method
though downward heat flow in a vertical stack is the most
4.1 A specimen and a heat flux transducer (HFT) are common one.
sandwiched between two flat plates controlled at different
6.2 Key Components of a Typical Device:
temperatures, to produce a heat flow through the test stack. A
6.2.1 The compressive force for the stack is to be provided
reproducible load is applied to the test stack by pneumatic or
by either a regulated pneumatic or hydraulic cylinder (1) or a
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
5. Significance and Use
plate is such as to ensure uniform heat distribution across its
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
6. Apparatus
the temperature of the interface on the plate side.
6.2.5 The sample (8) is in direct contact with the top plate
6.1 Aschematicrenderingofatypicalapparatusisshownin
Fig. 1. The relative position of the HFT to sample is not on one side and an intermediate plate (9) on the other side.
FIG. 1 Key Components of a Typical Device
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D6744 − 06 (2011)
6.2.6 The intermediate plate (9) is an optional item. Its 8.2 Condition the cut specimens in accordance with the
purpose is to provide a highly conductive environment to the requirements of the appropriate material specifications, if any.
second temperature sensor (10), to obtain an average tempera-
9. Calibration
ture of the surface. If the temperature sensor (10) is embedded
into the face of the HFT, or other means are provided to define
9.1 Select the mean temperature and load conditions re-
thetemperatureofthesurfacefacingthesample,theuseofthe
quired. Adjust the upper heater temperature (T ) and lower
u
intermediate plate is not mandatory.
heater temperature (T) such that the temperature difference at
l
6.2.7 Heat flux transducer (HFT) is a device that will
the required mean temperature is no less than 30 to 35 °C and
generate an electrical signal in proportion to the heat flux
the specimen ∆T is not less than 3 °C.Adjust the guard heater
across it. The level of output required (sensitivity) greatly
temperature(T )suchthatitisatapproximatelytheaverageof
g
depends on the rest of the instrumentation used to read it. The
T and T.
u l
overallperformanceoftheHFTanditsreadoutinstrumentation
9.2 Selectatleasttwocalibrationspecimenshavingthermal
shall be such as to meet the requirements in Section 13.
resistance values that bracket the range expected for the test
6.2.8 The lower plate (12) is constructed similarly to the
specimens at the temperature conditions required.
upper plate (4), except it is positioned as a mirror image.
9.3 Table 1 contains a list of several available materials
6.2.9 An insulator plate (16) separates the lower plate (12)
commonly used for calibration, together with corresponding
from the heat sink (17). In case of using circulating fluid in
thermal resistance (R ) values for a given thickness. This
placeofaheater/thermocouplearrangementintheupperand/or s
information is provided to assist the user in selecting optimum
lower plates, the heat sink may or may not be present.
specimenthicknessfortestingamaterialandindecidingwhich
6.2.10 The entire stack is surrounded by a cylindrical guard
calibration specimens to use.
(18) equipped with a heater (19) and a control thermocouple
(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
resistancerangeisfrom10×10 to400×10 m ·K/W.The
ambient region, no guard is required. A draft shield is recom-
most commonly used calibration materials are the Pyrex 7740,
mended in place of it.
Pyroceram 9606, and stainless steel.
NOTE 2—It is permissible to use thin layers of high conductivity grease
9.5 Measure the thickness of the specimen to 25 µm.
or elastomeric material on the two surfaces of the specimen to reduce the
9.6 Coatbothsurfacesofacalibrationspecimenwithavery
thermal resistance of the interface and promote uniform thermal contact
across the interface area. thin layer of a compatible heat sink compound or place a thin
NOTE 3—The cross sectional area of the specimen may be any,
layer of elastomeric heat transfer medium on it to help
however,mostcommonlycircularandrectangularcrosssectionsareused.
minimize the thermal resistance at the interfaces of adjacent
Minimum size is dictated by the magnitude of the disturbance caused by
contacting surfaces.
thermal sensors in relation to the overall flux distribution. The most
common sizes are 25 mm round or square to 50 mm round.
9.7 Insert the calibration specimen into the test chamber.
6.3 Requirements: Exercise care to ensure that all surfaces are free of any foreign
6.3.1 Temperature control of upper and lower plate is to be matter.
6 0.1 °C (6 0.18 °F) or better.
9.8 Close the test chamber and clamp the calibration speci-
6.3.2 Reproducible load of 0.28 MPa (40 psi) has been
men in position between the plates at the recommended
found to be satisfactory for solid specimens. Minimum load
compressive load of 0.28 MPa.
shall not be below 0.07 MPa (10 psi).
9.9 Wait for thermal equilibrium to be attained.This should
6.3.3 Temperature sensors are usually fine gage or small
be seen when all the temperatures measured do not drift more
diameter sheath thermocouples, however, ultraminiature resis-
tance thermometers and linear thermistors may also be used.
6.3.4 Operatingrangeofadeviceusingameantemperature
TABLE 1 Typical Thermal Resistance Values of Specimens of
guard shall be limited to − 100 °C to 300 °C, when using Different Materials
thermocouplesastemperaturesensors,and−180°Cto300°C
Material Approximate Thickness, Approximate
Thermal mm Thermal
with platinum resistance thermometers.
Conductivity, Resistance,
−4
W/(m·K) at 10 m ·K/W at
7. Test Specimen
30°C 30 °C
7.1 Thespecimentobetestedshallberepresentativeforthe A
Pyroceram 9606 420 50
A
sample material. The recommended specimen configuration is
Pyroceram 9606 410 25
A
Pyrex 7740 Glass 1 20 200
a 50.8 6 0.25 mm (2 6 0.010 in.) diameter disk, having
A
Pyrex 7740 Glass 1 10 100
smoothflatandparallelfaces, 60.025mm(60.001in.),such
A
Pyrex 7740 Glass 1 1 10
that a uniform thickness within 0.025 mm (6 0.001 in.) is 304 Stainless Steel 14 20 14
304 Stainless Steel 14 10 7
attained in the range from 12.7 to 25.4 mm (0.5 to 1.0 in.)
B
Vespel 0.4 2 50
A
8. Sampling and Conditioning
Pyrex 7740 and Pyroceram 9606 are products and trademarks of Corning Glass
Co., Corning, WV.
8.1 Cut representative test specimens from larger pieces of B
Vespel is a product of DuPont Co.
the sample material or body.
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D6744 − 06 (2011)
than 0.1° C in 1 min. Read and record all temperatures and the set of conditions. Once obtained, they should remain fixed for
output of the heat flux transducer. the particular settings used to attain the conditions.
NOTE 4—The time to attain thermal equilibrium is dependent upon the
NOTE 8—Since N is also determined by the particular HFTutilized, the
thickness of the specimen and its thermal properties. Experience shows
calibration should be checked occasionally to ensure that continuous
that approximately1his needed for thermal equilibrium to be attained,
heating/cycling does not affect the HFT.
when testing a specimen with the thermal conductivity within the
NOTE 9—The parameter R depends on the parallelism of the two
optimum operating range of the instrument.
surface plates and should be reproducible unless the test section is altered
mechanically in any way. If this occurs, recalibration is necessary.
9.10 Repeat the procedure in 9.5 to 9.9 with one or more
calibration specimens, having different thermal resistance val-
11.2 There are three methods of data analysis to dete
...