1、Designation: D6744 06 (Reapproved 2017)1Standard Test Method forDetermination of the Thermal Conductivity of AnodeCarbons by the Guarded Heat Flow Meter Technique1This standard is issued under the fixed designation D6744; the number immediately following the designation indicates the year oforiginal
2、 adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1NOTEUnits formatting was corrected editorially in February 2017.1. Scope1.1 Th
3、is test method covers a steady-state technique for thedetermination 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 30 W/(mK), (thermal resistance inthe range
4、from 10 to 400 104m2K/W) over the approxi-mate temperature range from 150 K 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 metho
5、d. Graphites usually have a very low thermal resistance, andthe interfaces between the specimen to be tested and the instrumentbecome more significant than the specimen itself.1.2 This test method is similar in concept to Test MethodsE1530 and C518. Significant attention has been paid to ensurethat
6、the thermal resistance of contacting surfaces is minimizedand reproducible.1.3 The values stated in SI units are regarded as standard.1.3.1 ExceptionThe values given in parentheses are forinformation only.1.4 This standard does not purport to address all of thesafety concerns, if any, associated wit
7、h its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C518 Test Method for Steady-State Thermal TransmissionProperties by
8、 Means of the Heat Flow Meter ApparatusE1530 Test Method for Evaluating the Resistance to Ther-mal Transmission of Materials by the Guarded Heat FlowMeter Technique3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 average temperature, nthe average temperature of asurface is the
9、area-weighted mean temperature of that surface.3.1.2 heat flux transducer, HFT, na device that producesan electrical output that is a function of the heat flux, in apredefined and reproducible manner.3.1.3 thermal conductance, C, nthe time rate of heat fluxthrough a unit area of a body induced by un
10、it temperaturedifference between the body surfaces.3.1.4 thermal conductivity, , of a solid material, nthetime rate of heat flow, under steady conditions, through unitarea, per unit temperature gradient in the direction perpendicu-lar to the area.3.1.5 thermal resistance, R, nthe reciprocal of therm
11、alconductance.3.2 Symbols: = thermal conductivity, W/(mK), Btuin/(hft2F)C = thermal conductance, W/(m2K), Btu/(hft2F)R = thermal resistance, m2K/W, (hft2F/Btu)x = specimen thickness, mm, (in.)A = specimen cross sectional area, m2, (ft2)Q = heat flow, W, (Btu/h) = heat flux transducer output, mVN = h
12、eat flux transducer calibration constant, W/(m2mV),Btu/(hft2mV)N = heat flux, W/m2, Btu/(hft2)T = temperature difference, C, (F)Tg= temperature of guard heater, C, (F)Tu= temperature of upper heater, C, (F)Tl= temperature of lower heater, C, (F)T1= temperature of one surface of the specimen, C, (F)T
13、2= temperature of the other surface of the specimen, C,(F)1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility ofSubcommittee D02.05 on Properties of Fuels, Petroleum Coke and Carbon Material.Current edi
14、tion approved Jan. 1, 2017. Published February 2017. Originallyapproved in 2001. Last previous edition in 2011 as D6744 06 (2011)1. DOI:10.1520/D6744-06R17E01.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of
15、ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized p
16、rinciples on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1Tm= mean temperature of the specimen, C, (F)s = unknown specimenr = kno
17、wn 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 through the test stack. Areproducible load is applied to the test stack by pneuma
18、tic 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 the two plates, in order tominimize lateral heat flow to and from the stack. At ste
19、ady-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 proportional to the heat flowthrough the specimen, the HFT and the interfaces bet
20、ween 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 the surface is made reproducible.5. Significance and Use5.1 This test method is desi
21、gned 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 shown inFig. 1. The relative position of the HFT to sample is notimportant (it may be
22、 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, al-though downward heat flow in a vertical stack is the mostcommon one.6.2 Key C
23、omponents 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 ensure that the loading can be varied and set tocertain values reproducibility.6.2.
24、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 jointfrom the top plate (4).6.2.4 The top plate (assumed to be the hot plate for thep
25、urposes 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 used as long as therequirements under 6.3 are met.) The construction of the toppla
26、te 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 notFIG. 1 Key Components of a Typical DeviceD6744 06 (2017)12interfere with the sample/plate interface, is a temperaturesens
27、or (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 item. Itspurpose is to
28、provide a highly conductive environment to thesecond 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 definethe temperature of the surface facing the sample, the use of theint
29、ermediate 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 of the instrumentation used to read it. Theoverall performance of the HF
30、Tand 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 plate (16) separates the lower plate (12)from the heat sink (17). In case of
31、 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 heater (19) and a control thermocouple(20) to maintain it at the mean temper
32、ature 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 of it.NOTE 2It is permissible to use thin layers of high conductivity gre
33、aseor elastomeric material on the two surfaces of the specimen to reduce thethermal resistance of the interface and promote uniform thermal contactacross the interface area.NOTE 3The cross sectional area of the specimen may be any,however, most commonly circular and rectangular cross sections are us
34、ed.Minimum 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 Temperature control of upper and lower plate is to be60.1 C (6 0.18 F) or better
35、.6.3.2 Reproducible load of 0.28 MPa (40 psi) has beenfound to be satisfactory for solid specimens. Minimum loadshall not be below 0.07 MPa (10 psi).6.3.3 Temperature sensors are usually fine gauge or smalldiameter sheath thermocouples, however, ultraminiature resis-tance thermometers and linear the
36、rmistors 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. Test Specimen7.1 The specimen to be tested shall be representative
37、for thesample material. The recommended specimen configuration isa 50.8 mm 6 0.25 mm (2 in. 6 0.010 in.) diameter disk,having smooth flat and parallel faces, 60.025 mm(60.001 in.), such that a uniform thickness within 0.025 mm(6 0.001 in.) is attained in the range from 12.7 mm to 25.4 mm(0.5 in. to
38、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. Calibration9.1 Select the mean temperature and load cond
39、itions 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 C to 35 Cand the specimen T is not less than 3 C. Adjust the guardheater temperature (Tg) such that it is at approximate
40、ly theaverage of Tuand 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 available materialscommonly used for calibration, together with
41、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 thermal conductivity for which this testmethod is most su
42、itable is such that the optimum thermalresistance range is from 10 104to 400 104m2K/W. Themost commonly used calibration materials are the Pyrex 7740,Pyroceram 9606, and stainless steel.9.5 Measure the thickness of the specimen to 25 m.9.6 Coat both surfaces of a calibration specimen with a verythin
43、 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.TABLE 1 Typical Thermal Resistance Values of Specimens ofDifferent MaterialsMaterial ApproximateThermalCond
44、uctivity,W/(mK) at30 CThickness,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 9606 are produ
45、cts and trademarks of Corning GlassCo., Corning, WV.BVespel is a product of DuPont Co.D6744 06 (2017)139.7 Insert the calibration specimen into the test 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 p
46、osition between the plates at the recommendedcompressive load of 0.28 MPa.9.9 Wait for thermal equilibrium to be attained. This shouldbe seen when all 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
47、time to attain thermal equilibrium is dependent upon thethickness of the specimen and its thermal properties. Experience showsthat approximately 1 h is needed for thermal equilibrium to be attained,when testing a specimen with the thermal conductivity within theoptimum operating range of the instrum
48、ent.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 conducted at a temperature in arange and under appl
49、ied 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 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
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