ASTM F433-2002(2014)e1 Standard Practice for Evaluating Thermal Conductivity of Gasket Materials《衬垫材料的导热性评定的标准实施规程》.pdf

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1、Designation: F433 02 (Reapproved 2014)1Standard Practice forEvaluating Thermal Conductivity of Gasket Materials1This standard is issued under the fixed designation F433; the number immediately following the designation indicates the year of originaladoption or, in the case of revision, the year of l

2、ast revision.Anumber in parentheses indicates the year of last reapproval.Asuperscriptepsilon () indicates an editorial change since the last revision or reapproval.1NOTEEditorially corrected Footnote 6 in July 2014.1. Scope1.1 This practice covers a means of measuring the amountof heat transfer qua

3、ntitatively through a material or system.1.2 This practice is similar to the Heat Flow Meter Systemof Test Method C518, but modified to accommodate small testsamples of higher thermal conductance.1.3 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are

4、 for informationonly.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 determine the applica-bility of regulatory limitations prior t

5、o use.2. Referenced Documents2.1 ASTM Standards:2C518 Test Method for Steady-State Thermal TransmissionProperties by Means of the Heat Flow Meter ApparatusD2214 Test Method for Estimating the Thermal Conductiv-ity of Leather with the Cenco-FitchApparatus (Withdrawn2008)3F104 Classification System fo

6、r Nonmetallic Gasket Materi-als3. Terminology3.1 Definitions:3.1.1 thermal conductivity, k, of a solid materialthe timerate of steady heat flow, watts (or Btu/h), through a unit area,m2(or ft2), per unit temperature gradient in the directionperpendicular to an isothermal surface C/m (or F/in.). Thek

7、-factor is expressed W/mK (Btuin./hft2F).3.2 Symbols:k = thermal conductivity, W/mK (Btuin./hft2F)C = thermal conductance, W/m2K (Btu/hft2F)x = sample thickness, mm (in.)A = sample cross-sectional area, m2(ft2)q = heat flow, W (Btu/h) = heat flow transducer output, mVN = heat flow transducer calibra

8、tion constant,W/m2mV (Btu/hft2mV)N = heat flux, W/m2(Btu/hft2)T = temperature difference, C (F) or mVT1= temperature of lower sample surface,C (F) ormVT2= temperature of upper sample surface, C (F)or mVTh= temperature of HFT surface facing sample, C(F) or mVTc= temperature of upper heater surface fa

9、cingsample, C (F) or mVT = temperature, C (F) = total temperature drop across interfaces be-tween sample and adjacent surfaces, C (F) ormV = coefficient of thermal resistance at interfaces,m2K/W (hft2F/Btu) = correction constantsubscripts = unknown samplesubscriptr = known calibration sample4. Summa

10、ry of Practice4.1 The sample and the heat flow transducer (HFT) aresandwiched between two controlled heater plates. The lowerheater is set at a higher temperature than the upper plate toproduce a flow of heat through the sample. The differential ofthese two temperatures, T, sensed by thermocouples,

11、isamplified along with the electrical output, , of the HFT and isdirectly proportional to the heat flow through the sample,expressed as W/m2(Btu/hft2). See Appendix for further1This practice is under the jurisdiction ofASTM Committee F03 on Gaskets andis the direct responsibility of Subcommittee F03

12、.10 on Composite Gaskets.Current edition approved July 1, 2014. Published November 2014. Originallyapproved in 1964. Last previous edition approved in 2009 as F433 02 (2009).DOI: 10.1520/F0433-02R14E01.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Serv

13、ice at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Cons

14、hohocken, PA 19428-2959. United States1information. This recommended practice can be used formeasuring heat transfer at a hot side temperature up to 200C(392F). See Figs. 1-5.5. Significance and Use5.1 This practice is designed to compare related materialsunder controlled conditions and their abilit

15、y to maintain aminimum amount of thermal conductance. Test results shouldbe correlated with field results in order to predict heat transferproperties in particular applications.5.2 This practice may be used as a routine test when agreedupon by the user and the producer.6. Apparatus6.1 Heat Flow Tran

16、sducer (HFT), with controlled heaterplates, thermocouples, and an analog computer module.47. Test Specimen7.1 The sample size shall be a 50.8-mm (2-in.) diameterdisk 60.25 mm (60.010 in.) from 2.29 to 12.7 mm (0.090 to0.500 in.) thick.8. Conditioning8.1 Condition the cut specimens in accordance with

17、 theirclassification, as required in Classification F104.9. Procedure9.1 Test temperatures are suggested from 100 to 175C (212to 347F) or whatever is agreed upon between the producer anduser. (The guard heater is usually set at or near the averagesample temperature between the lower and upper heater

18、plates.)9.1.1 Release the compressive load, pull out the tray, andload the sample. Care must be maintained to ensure that thetray compartment is free of any foreign matter. Clean asrequired.9.1.2 Push the tray back into the chamber with a ball andplunger locking the tray into position.9.1.3 Close th

19、e test section door and switch the air control to“stack clamped.” The sample holder is now raised automati-cally until the sample is clamped in place between the upperand lower heaters. The compressive load can be adjusted bycontrolling the air pressure at the rear of the unit.Apressure of0.345 MPa

20、(50 psi) is the recommended maximum and shouldbe specified by both the producer and user to ensure repeatableresults.9.1.4 Allow from 1 to 2 h for the reading to stabilize. Readthe sample thermal conductance and temperature directly fromdigital meters on the front panel. The instrument has stabilize

21、dwhen the temperature indicated changes by no more than65 %h and the conductance indicated changes no more than62 %h.10. Report10.1 The report shall include the following:10.1.1 Sample conditioning procedure,4The sole source of supply of the apparatus known to the committee at this timeis Holometrix

22、, Inc., 25 Wiggins Avenue, Bedford, MA 017302323. If you areaware of alternative suppliers, please provide this information to ASTM Headquar-ters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend.FIG. 1 Heat Flow Meter Assembly

23、 With Water-Cooled Heat SinkFIG. 2 HFT Electrical Output and Heat Flow Section With Tem-perature SensorsF433 02 (2014)1210.1.2 Ambient temperature,10.1.3 Sample hot side temperature, Th,10.1.4 Sample cold side temperature, Tc,10.1.5 Sample temperature drop, ThTc,10.1.6 Average sample temperature, (T

24、h+ Tc)/2,10.1.7 Sample thickness, x,10.1.8 Thermal conductivity, k, and10.1.9 Compressive load.11. Precision and Bias11.1 The precision of the practice is expected to be within65%.12. Keywords12.1 comparative thermal conductance; heat flow; thermalconductanceFIG. 3 Location of Thermocouples to Produ

25、ce a Temperature Gradient Through the Test SampleFIG. 4 The Hot and Cold Sample Surface Temperature Differential Amplified with the HFT Output, Divided Electronically, and DisplayedDigitallyFIG. 5 Clarification of Fig. 4 Showing the Calibration to Obtain the Correction Constant Correct Value Before

26、Testing an UnknownSampleF433 02 (2014)13APPENDIXES(Nonmandatory Information)X1. GENERAL INFORMATIONX1.1 If a test specimen in the form of a disk is held betweentwo flat surfaces, each controlled at a different temperature, aflow of heat passes through the sample from the hot to the coldsurface. The

27、thermal conductivity is determined by the follow-ing equation:k 5qAxTW/mK# or Btuin./hft2F# (X1.1)where:q = heat flow through the sample, watt (Btu/h),A = cross-sectional area of the sample, m2(ft2),x = sample thickness, mm (in.), andT = temperature difference across the sample, C (F).X1.2 The heat

28、flow per unit area is measured with a heatflow transducer, a sensitive device producing an electricaloutput that is directly proportional to the heat flux, q/A.If theoutput of the heat flow transducer (HFT) is called than thek-factor can be calculated from:k 5 NxT(X1.2)X1.3 In this equation , T, and

29、 x can be measured bysimple means, while the calibration constant, N, can bedetermined by testing a sample of known thermal conductivity.X2. CALCULATIONSX2.1 After thermal equilibrium has been established, thevarious sensors may be read and recorded. Data reduction isdependent upon the positions of

30、the thermocouples for mea-suring the sample T, as follows:X2.1.1 If thermocouples are installed in the sample surfacethen:T 5 T12 T2mV! (X2.1)NOTE X2.1The sample thickness must be adjusted to account for thethermocouples being slightly below the surface, see Fig. 2.X2.1.2 A calibration run must firs

31、t be made using a calibra-tion standard of known thermal conductivity, kr.5This proce-dure is identical to the procedure for the unknown sample asfollows:X2.1.2.1 k-factor, unknown sample:ks5 NsxsTs(X2.2)X2.1.2.2 k-factor, known sample:kr5 NrxrTr(X2.3)X2.1.2.3 Combining the unknown and known samples

32、:ks5 krsrxsxrTrTs(X2.4)X2.1.3 If thermocouples are located permanently in thesurface adjacent to the sample, then, in accordance with Fig. 3,the T obtained by subtracting Thand Tcis not equal to the Tacross the sample itself due to contact resistance. (Acorrectionfactor can be obtained from the cali

33、bration test data.)X2.1.4 The calibration sample must have a set of thermo-couples installed in grooves in the upper and lower surfaces.During calibration the following results are obtained:kr5 NrxrTr(X2.5)where:Tr5 T12 T2(X2.6)X2.1.5 From the various thermocouple readings we cancalculate the total

34、interfacial temperature drop as follows: 5 Th2 Tc!r2 Tr(X2.7)The interfacial temperature drop, , is proportional to theheat flux, Nras follows: 5 Nr(X2.8)where is a proportionality constant and depends mostly onthe surface conditions and on the applied pressure on the teststack. It is assumed that r

35、emains essentiality constant fromtest to test so long as the applied pressure remains the same.The contact coefficient is thus obtained from Eq X2.6. 5Nr(X2.9)X2.1.6 When the unknown sample is tested, the followingdata must be recorded: s, Th,Tc, and xs. The correctedtemperature drop across the samp

36、le is as follows:Ts5 Th2 Tc!s2 Ns(X2.10)Substituting Eq X2.9 as follows:Ts5 Th2 Tc!s2 sr(X2.11)The thermal conductivity of the unknown sample is asfollows:5Borosilicate No. 7740 has been found to be a suitable reference standardmaterial. This can be purchased with the test equipment. The reference s

37、tandardused should be documented in the test report.F433 02 (2014)14ks5 NsxsTs(X2.12)Combining Eq X2.3 and Eq X2.10 we have the following:ks5 krsrxsxrTrTs(X2.13)where:Tr5 T12 T2, (X2.14)andTs5 Th2 Tc!s2 sr(X2.15)in which: 5 Th2 Tc!r2 Tr(X2.16)X2.1.7 Substitution of Eq X2.4, Eq X2.9, and Eq X2.5 weha

38、ve the following:ks5 krxsxr11 2STh2 TcT12 T2Dr1rsTh2 Tc!sT12 T2!r(X2.17)NOTE X2.2If there is no contact resistance, , Eq X2.4 goes to zeroand the Eq X2.12 assumes the same form as Eq X2.2. Also, note that thecalibration data, subscript r, needs to be obtained only once at eachtemperature level. Ther

39、mocouple readings may be kept in mV and neednot be converted to C (F) except for determining the average sampletemperature.)X2.1.8 If an analog calculator is used to obtain the unknownsample k-factor and thermocouples are installed in the samplesurface: The T signal is then obtained by connecting th

40、ethermocouples differentially; the HFT and T signals areamplified and divided electronically with the results shown ona digital volt meter (Fig. 4). The gain of the final stageamplifier can be varied to produce an output voltage equal tothe thermal conductance of the sample in any desired set ofunit

41、s. In other words, if the thermal conductance, (C=kx),of the sample is 15 Btu/hft2F, the output voltage of theanalog calculator is 15 V. Thek-factor is obtained by multiply-ing the displayed value by the sample thickness, x, measuredseparately.X2.1.9 However, the instrument first must be calibrated

42、bytesting a reference sample of known thermal conductivity.After thermal equilibrium has been established in the test stack,the C-factor is determined by taking k/xand the final gain isadjusted until the displayed value equals C.X2.1.10 If thermocouples are located permanently in thesurface adjacent

43、 to the sample, a correction must be made inthe determination of the sample Tto account for interfacialresistance. The differential of the two permanentthermocouples, (ThTc), must be reduced by a correctionfactor which is proportional to the heat flow transducer output, (see Eq X2.8). The temperatur

44、e drop across the sample is asfollows:T 5 Th2 Tc! 2 (X2.18)The analog calculator can be used to compute the C-factor ofthe sample (see Fig. 5):C 5Th2 Tc! 2 (X2.19)and the gain of the final stage amplifier can be varied to yieldthe correct value on the digital display.X2.1.11 A calibration run must b

45、e made first to obtain thecorrect value for and to adjust the final gain for the properC-factor. The reference sample must have thermocouplesinstalled in grooves in the surface. After these thermocoupleshave been connected to the T input of the calculator and thecorrection constant has been adjusted

46、 to zero (see Fig. 5).Thefinal gain must be adjusted to obtain the correct C-factor of thereference sample. Next, the permanent thermocouples areconnected to the T channel of the calculator and the correc-tion constant adjusted until the displayed C-value is the sameas before. Subsequent tests on un

47、known samples withoutthermocouples yield the correct C-factor directly on the digitaldisplay. Multiplying these C-factors by the correspondingsample thickness gives the k for each case.X3. PROPOSAL FOR INFORMATION PURPOSES ONLYX3.1 A method and apparatus has been established for useas a screening to

48、ol which can relate to the relative orders ofthermal conductivity. It is not intended for use in writingspecifications, as it cannot provide reliable results for thethermal conductivity of a material.X3.2 The device referred to is described as a heat-insulatedcopper vessel with a heavy copper plate

49、base, and a receivercontaining a mating copper plug which is also insulated. Whilethe upper plate or vessel and test sample is at a constanttemperature, heat flow through the sample is produced bymeasuring the slowly changing temperature increase of thereceiver with thermocouples. The rate of flow of heat throughthe specimen is proportional to the area and the T of the facesof the specime