ASTM D6744-06(2011)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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