1、Designation: D 6744 06An American National StandardStandard Test Method forDetermination of the Thermal Conductivity of AnodeCarbons by the Guarded Heat Flow Meter Technique1This standard is issued under the fixed designation D 6744; the number immediately following the designation indicates the yea
2、r oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers a steady-state technique for t
3、hedetermination of the thermal conductivity of carbon materialsin thicknesses of less than 25 mm. The test method is useful forhomogeneous materials having a thermal conductivity in theapproximate range 1 l 30 W/(mK), (thermal resistance inthe range from 10 to 400 3 104m2K/W) over the approxi-mate t
4、emperature range from 150 to 600 K. It can be usedoutside these ranges with reduced accuracy for thicker speci-mens and for thermal conductivity values up to 60 W/(mK).NOTE 1It is not recommended to test graphite cathode materials usingthis test method. Graphites usually have a very low thermal resi
5、stance, andthe interfaces between the sample to be tested and the instrument becomemore significant than the sample itself.1.2 This test method is similar in concept to Test MethodsE 1530 and C 518. Significant attention has been paid to ensurethat the thermal resistance of contacting surfaces is mi
6、nimizedand reproducible.1.3 The values stated in SI units are regarded as standard.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and
7、determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C 518 Test Method for Steady-State Thermal TransmissionProperties by Means of the Heat Flow Meter ApparatusE 1530 Test Method for Evaluating the Resistance to Ther-mal Transmission of Mater
8、ials by the Guarded Heat FlowMeter Technique3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 average temperaturethe average temperature of asurface is the area-weighted mean temperature of that surface.3.1.2 heat flux transducer (HFT)a device that produces anelectrical output t
9、hat is a function of the heat flux, in apredefined and reproducible manner.3.1.3 thermal conductance (C)the time rate of heat fluxthrough a unit area of a body induced by unit temperaturedifference between the body surfaces.3.1.4 thermal conductivity (l), of a solid materialthe timerate of heat flow
10、, under steady conditions, through unit area,per unit temperature gradient in the direction perpendicular tothe area.3.1.5 thermal resistance (R)the reciprocal of thermalconductance.3.2 Symbols:l = thermal conductivity, W/(mK), Btuin/(hft2F)C = thermal conductance, W/(m2K), Btu/(hft2F)R = thermal re
11、sistance, m2K/W, hft2F/BtuDx = specimen thickness, mm, inA = specimen cross sectional area, m2,ft2Q = heat flow, W, Btu/hf = heat flux transducer output, mVN = heat flux transducer calibration constant,W/(m2mV), Btu/(hft2mV)Nf = heat flux, W/m2, Btu/(hft2)DT = temperature difference, C, FTg= tempera
12、ture of guard heater, C, FTu= temperature of upper heater, C, FTl= temperature of lower heater, C, FT1= temperature of one surface of the specimen, C, FT2= temperature of the other surface of the specimen, C,FTm= mean temperature of the specimen, C, Fs = unknown specimen1This test method is under th
13、e jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.05 on Properties of Fuels, Petroleum Coke and Carbon Material.Current edition approved Jan. 1, 2006. Published February 2006. Originallyapproved in 2001. Last previous edition
14、 in 2001 as D 674401.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr
15、Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.r = known calibration or reference specimeno = contacts4. Summary of Test Method4.1 A specimen and a heat flux transducer (HFT) aresandwiched between two flat plates controlled at differenttemperatures, to produce a heat flow
16、 through the test stack. Areproducible load is applied to the test stack by pneumatic orhydraulic means, to ensure that there is a reproducible contactresistance between the specimen and plate surfaces. A cylin-drical guard surrounds the test stack and is maintained at auniform mean temperature of t
17、he two plates, in order tominimize lateral heat flow to and from the stack. At steady-state, the difference in temperature between the surfacescontacting the specimen is measured with temperature sensorsembedded in the surfaces, together with the electrical output ofthe HFT. This output (voltage) is
18、 proportional to the heat flowthrough the specimen, the HFT and the interfaces between thespecimen and the apparatus. The proportionality is obtainedthrough prior calibration of the system with specimens ofknown thermal resistance measured under the same conditions,such that contact resistance at th
19、e surface is made reproducible.5. Significance and Use5.1 This test method is designed to measure and comparethermal properties of materials under controlled conditions andtheir ability to maintain required thermal conductance levels.6. Apparatus6.1 Aschematic rendering of a typical apparatus is sho
20、wn inFig. 1. The relative position of the HFT to sample is notimportant (it may be on the hot or cold side) as the test methodis based on maintaining axial heat flow with minimal heatlosses or gains radially. It is also up to the designer whether tochoose heat flow upward or downward or horizontally
21、, al-though downward heat flow in a vertical stack is the mostcommon one.6.2 Key Components of a Typical Device:6.2.1 The compressive force for the stack is to be providedby either a regulated pneumatic or hydraulic cylinder (1) or aspring loaded mechanism. In either case, means must beprovided to e
22、nsure that the loading can be varied and set tocertain values reproducibility.6.2.2 The loading force must be transmitted to the stackthrough a gimball joint (2) that allows up to 5 swivel in theplane perpendicular to the axis of the stack.6.2.3 Suitable insulator plate (3) separates the gimball joi
23、ntfrom the top plate (4).6.2.4 The top plate (assumed to be the hot plate for thepurposes of this description) is equipped with a heater (5) andcontrol thermocouple (6) adjacent to the heater, to maintain acertain desired temperature. (Other means of producing andmaintaining temperature may also be
24、used as long as therequirements under 6.3 are met.) The construction of the topplate is such as to ensure uniform heat distribution across itsface contacting the sample (8). Attached to this face (orembedded in close proximity to it), in a fashion that does notinterfere with the sample/plate interfa
25、ce, is a temperaturesensor (7) (typically a thermocouple, thermistor) that definesthe temperature of the interface on the plate side.6.2.5 The sample (8) is in direct contact with the top plateon one side and an intermediate plate (9) on the other side.6.2.6 The intermediate plate (9) is an optional
26、 item. Itspurpose is to provide a highly conductive environment to theFIG. 1 Key Components of a Typical DeviceD6744062second temperature sensor (10), to obtain an average tempera-ture of the surface. If the temperature sensor (10) is embeddedinto the face of the HFT, or other means are provided to
27、definethe temperature of the surface facing the sample, the use of theintermediate plate is not mandatory.6.2.7 Heat flux transducer (HFT) is a device that willgenerate an electrical signal in proportion to the heat fluxacross it. The level of output required (sensitivity) greatlydepends on the rest
28、 of the instrumentation used to read it. Theoverall performance of the HFTand its readout instrumentationshall be such as to meet the requirements in Section 13.6.2.8 The lower plate (12) is constructed similarly to theupper plate (4), except it is positioned as a mirror image.6.2.9 An insulator pla
29、te (16) separates the lower plate (12)from the heat sink (17). In case of using circulating fluid inplace of a heater/thermocouple arrangement in the upper and/orlower plates, the heat sink may or may not be present.6.2.10 The entire stack is surrounded by a cylindrical guard(18) equipped with a hea
30、ter (19) and a control thermocouple(20) to maintain it at the mean temperature between the upperand lower plates. A small, generally unfilled gap separates theguard from the stack. For instruments limited to operate in theambient region, no guard is required. A draft shield is recom-mended in place
31、of it.NOTE 2It is permissible to use thin layers of high conductivity greaseor elastomeric material on the two surfaces of the sample to reduce thethermal resistance of the interface and promote uniform thermal contactacross the interface area.NOTE 3The cross sectional area of the sample may be any,
32、 however,most commonly circular and rectangular cross sections are used. Mini-mum size is dictated by the magnitude of the disturbance caused bythermal sensors in relation to the overall flux distribution. The mostcommon sizes are 25 mm round or square to 50 mm round.6.3 Requirements:6.3.1 Temperatu
33、re control of upper and lower plate is to be6 0.1 C (6 0.18 F) or better.6.3.2 Reproducible load of 0.28 MPa (40 psi) has beenfound to be satisfactory for solid samples. Minimum load shallnot be below 0.07 MPa (10 psi).6.3.3 Temperature sensors are usually fine gage or smalldiameter sheath thermocou
34、ples, however, ultraminiature resis-tance thermometers and linear thermistors may also be used.6.3.4 Operating range of a device using a mean temperatureguard shall be limited to 100 C to 300 C, when usingthermocouples as temperature sensors, and 180 C to 300 Cwith platinum resistance thermometers.7
35、. Test Specimen7.1 The specimen to be tested shall be representative for thesample material. The recommended specimen configuration isa 50.8 6 0.25 mm (2 6 0.010 in.) diameter disk, havingsmooth flat and parallel faces, 6 0.025 mm (6 0.001 in.), suchthat a uniform thickness within 0.025 mm (6 0.001
36、in.) isattained in the range from 12.7 to 25.4 mm (0.5 to 1.0 in.)8. Sampling and Conditioning8.1 Cut representative test specimens from larger pieces ofthe sample material or body.8.2 Condition the cut specimens in accordance with therequirements of the appropriate material specifications, if any.9
37、. Calibration9.1 Select the mean temperature and load conditions re-quired. Adjust the upper heater temperature (Tu) and lowerheater temperature (Tl) such that the temperature difference atthe required mean temperature is no less than 30 to 35 C andthe specimen DT is not less than 3 C. Adjust the gu
38、ard heatertemperature (Tg) such that it is at approximately the average ofTuand Tl.9.2 Select at least two calibration specimens having thermalresistance values that bracket the range expected for the testspecimens at the temperature conditions required.9.3 Table 1 contains a list of several availab
39、le materialscommonly used for calibration, together with correspondingthermal resistance (Rs) values for a given thickness. Thisinformation is provided to assist the user in selecting optimumspecimen thickness for testing a material and in deciding whichcalibration specimens to use.9.4 The range of
40、thermal conductivity for which this testmethod is most suitable is such that the optimum thermalresistance range is from 10 3 104to 400 3 104m2K/W.The most commonly used calibration materials are the Pyrex7740, Pyroceram 9606, and stainless steel.9.5 Measure the thickness of the specimen to 25 m.9.6
41、 Coat both surfaces of a calibration specimen with a verythin layer of a compatible heat sink compound or place a thinlayer of elastomeric heat transfer medium on it to helpminimize the thermal resistance at the interfaces of adjacentcontacting surfaces.9.7 Insert the calibration specimen into the t
42、est chamber.Exercise care to ensure that all surfaces are free of any foreignmatter.9.8 Close the test chamber and clamp the calibration speci-men in position between the plates at the recommendedcompressive load of 0.28 MPa.9.9 Wait for thermal equilibrium to be attained. This shouldbe seen when al
43、l the temperatures measured do not drift morethan 0.1 C in 1 min. Read and record all temperatures and theoutput of the heat flux transducer.NOTE 4The time to attain thermal equilibrium is dependent upon theTABLE 1 Typical Thermal Resistance Values of Specimens ofDifferent MaterialsMaterial Approxim
44、ateThermalConductivity,W/(mK) at30CThickness,mmApproximateThermalResistance,104m2K/W at30 CPyroceram 9606A42050Pyroceram 9606A41 2Pyrex 7740AGlass 1 20 200Pyrex 7740AGlass 1 10 100Pyrex 7740AGlass 1 1 10304 Stainless Steel 14 20 14304 Stainless Steel 14 10 7VespelB0.4 2 50APyrex 7740 and Pyroceram 9
45、606 are products and trademarks of CorningGlass Co., Corning, WV.BVespel is a product of DuPont Co.D6744063thickness of the specimen and its thermal properties. Experience showsthat approximately1hisneeded for thermal equilibrium to be attained,when testing a sample with the thermal conductivity wit
46、hin the optimumoperating range of the instrument.9.10 Repeat the procedure in 9.5 to 9.9 with one or morecalibration specimens, having different thermal resistance val-ues covering the expected range for the test specimen.10. Thermal Conductivity of an Unknown Specimen10.1 Tests shall only be conduc
47、ted at a temperature in arange and under applied load conditions for which validcalibration data exists.10.1.1 When automatic control of temperature of the heatersis involved, the controller settings should be checked to ensurethat they are the same as those for the desired temperature levelfor the
48、calibration.10.2 Measure the thickness of the specimen to 25 m.10.3 Apply a thin layer of heat sink compound or place athin layer of elastomeric heat transfer medium on the surfacesof the test specimen.NOTE 5Exercise care to ensure that any material applied to thesurfaces of the specimen does not ch
49、ange its thermal properties by soakinginto it.10.4 Repeat the procedure in 9.7 to 9.9 using the testspecimen.NOTE 6Experience has indicated that for reliable measurements on asingle specimen, the minimum thickness (mm) is given by Dx $ 3l(W/(mK).10.5 Automated SystemsComputerized or otherwise auto-mated systems may require different operating steps, and mayor may not provide intermediate readings described in 9.9. Forthese devices, follow the operating and calibrating proceduresprescribed by the manufacturer.NOT
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