ASTM D7896-2014 1595 Standard Test Method for Thermal Conductivity Thermal Diffusivity and Volumetric Heat Capacity of Engine Coolants and Related Fluids by Transient Hot Wire Liqu.pdf

1、Designation: D7896 14Standard Test Method forThermal Conductivity, Thermal Diffusivity and VolumetricHeat Capacity of Engine Coolants and Related Fluids byTransient Hot Wire Liquid Thermal Conductivity Method1This standard is issued under the fixed designation D7896; the number immediately following

2、 the designation indicates the year 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 () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method cove

3、rs the use of a transient hot wireliquid thermal conductivity method and associated equipment(the System) for the determination of thermal conductivity,thermal diffusivity and volumetric heat capacity of aqueousengine coolants, non-aqueous engine coolants, and relatedfluids. The System is intended f

4、or use in a laboratory.1.2 The System directly measures thermal conductivity andthermal diffusivity without the requirement to input anyadditional properties. Volumetric heat capacity is calculated bydividing the thermal conductivity by the thermal diffusivity ofthe sample measured.1.3 This test met

5、hod can be applied to any aqueous ornon-aqueous engine coolants or related fluid with thermalconductivity in the range of 0.1 to 1.0 W/mK.1.4 This test method excludes fluids that react with plati-num.1.5 The range of temperatures applicable to this test methodis 20 to 100C.1.6 This test method requ

6、ires a sample of approximately 40mL.1.7 The System may be used without external pressurizationfor any fluid having a vapor pressure of 33.8 kPa (4.9 psia) orless at the test temperature.1.8 For a fluid having a vapor pressure greater than 33.8 kPa(4.9 psia) at the test temperature, external pressuri

7、zation isrequired (see Annex A2).1.9 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.9.1 ExceptionInch-pound units are provided in 1.7, 1.8,4.1, 7.8, and A2.1 for information.1.10 This standard does not purport to address all

8、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 to use.2. Referenced Documents2.1 ASTM Standards:2D1176 Practice for Sam

9、pling and Preparing Aqueous Solu-tions of Engine Coolants orAntirusts for Testing PurposesE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 Definitions of Thermal Related Units:3.1.1 density (),nthe mass per unit volume of a sub-stance

10、under specific conditions of pressure and temperature.Unit: kg/m3.3.1.2 specific heat capacity (Cp),nthe amount of heatrequired to raise the temperature of a unit mass of material by1C. See Annex A1. Unit: J/(kgK).3.1.3 thermal conductivity (),nrate of heat flow understeady conditions through unit a

11、rea, per unit temperaturegradient in the direction perpendicular to the area. Unit:W/mK.3.1.4 thermal diffusivity (),na measure of the ability of asubstance to transmit a difference in temperature. Unit: m2/s.3.1.5 volumetric heat capacity (VHC),nthe amount ofheat required to raise the temperature o

12、f a unit volume ofmaterial by 1C. Volumetric heat capacity is the thermalconductivity of a material divided by its thermal diffusivity.Unit: J/m3K.3.2 Definitions of Terms Specific to This Standard:3.2.1 transient hot wire method, na method for measure-ment of thermal properties wherein a thin wire

13、is immersed in1This test method is under the jurisdiction of ASTM Committee D15 on EngineCoolants and Related Fluids, and is the direct responsibility of SubcommitteeD15.22 on Non-Aqueous Coolants.Current edition approved Feb. 1, 2014. Published June 2014. DOI: 10.1520/D7896-14.2For referenced ASTM

14、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.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocke

15、n, PA 19428-2959. United States1a liquid specimen that is contained in a sampling cell. Aninstant of current is sent through the wire, heating both the wireand specimen. Immediately afterward, the resistance of thewire is measured with respect to time, while the wire cools. Atemperature-time profile

16、 of the specimen is produced and fromthis profile, thermal properties are determined.3.2.1.1 dry bath, na temperature control peripheral with acentral heating well that receives the sampling cell containingthe liquid specimen for providing temperatures above ambient.3.2.1.2 heat exchanger and circul

17、ator, na temperaturecontrol peripheral consisting of a refrigerated/heated circulatorfor heating and cooling that is connected to a heat exchanger.The heat exchanger has a central well that receives thesampling cell containing the liquid specimen, for providingtemperatures above and below ambient.3.

18、2.1.3 liquid, nrefers to the engine coolant or relatedfluid sample.4. Summary of Test Method4.1 A fluid to be tested is placed inside the sampling cellassembly that is part of the System apparatus. The temperaturewithin the sampling cell assembly is regulated by the use of atemperature control perip

19、heral. Regardless of the testtemperature, the sample and the System sensor are allowed toequilibrate to approximately the same temperature. The sam-pling cell assembly may be pressurized by up to a gaugepressure of 241 kPa (35 psig). The sensor, a thin platinum wire,is immersed in the liquid test sa

20、mple. A current is introducedinto the wire over the short test time of 0.8 s that heats both thewire and the liquid sample. The temperature of the wire and theresistance of the wire decay rapidly once the current isremoved. The resistance of the wire is measured with respect totime and a temperature

21、 versus time profile for the liquid sampleis created. From the temperature versus time profile, thethermal conductivity and thermal diffusivity of the liquidspecimen are determined. Volumetric heat capacity is deter-mined by dividing the measured thermal conductivity by themeasured thermal diffusivi

22、ty of the specimen.5. Significance and Use5.1 This test method covers the measurement of thermalproperties for engine coolants (aqueous or non-aqueous) andrelated fluids.5.2 With each single measurement, the thermal conductivity() and thermal diffusivity () are measured directly, andvolumetric heat

23、capacity (VHC) is determined by the relation-ship:VHC 5 (1)5.3 The test method is transient and requires only a smallamount of specimen and a short duration of time (0.8 s) to runa measurement. These attributes minimize heat convection inthe liquid.5.4 The brief application of current to the sensor

24、wire addsvery little heat to the test specimen and ten repetitive tests maybe applied at 30-s intervals without causing any significantconvection or temperature drift.6. Apparatus6.1 Transient Hotwire Liquid Thermal Conductivity Mea-surement System:NOTE 1The descriptions and instructions contained h

25、erein are basedupon familiarity with the ThermTest, Inc. THW Lambda Transient HotWire Liquid Thermal Conductivity Meter.3Other equivalent systems maybe suitable for this application.6.1.1 The apparatus for the test method (Fig. 1) consists ofa sampling cell assembly with platinum wire sensor inserte

26、d,and a controller containing a microprocessor. Unless themeasurements are to be made at ambient temperature, theapparatus also includes a temperature control peripheral (eithera dry bath or heat exchanger and circulator type). In a typicalimplementation of the System, a personal computer is used fo

27、rconvenience and greater flexibility in operation, and softwaresupplied by the manufacturer provides the user interface,control of test sequencing, data acquisition, and options for3http:/.Shown are the controller connected to the platinum-wire sensor with the sensor residing in the sampling cell, a

28、long with the liquid specimen. For non-ambienttemperature readings, the sampling cell inserts into a temperature control peripheral (not shown). The computer downloads data from the controller for storage and forthe creation of spreadsheets and reports.FIG. 1 Transient Hot Wire Liquid Thermal Conduc

29、tivity ApparatusD7896 142working with test results in a spreadsheet program. Specificoperating instructions are provided in the equipment manuals.6.2 Transient Hot Wire Sampling Cell Assembly:6.2.1 Fig. 2 shows details of the sampling cell assembly.Fig. 3 shows what the hot wire sensor actually look

30、s like.7. Specimen and Test Preparations7.1 The sampling cell must be clean and dry before theliquid to be tested is introduced into it.7.2 If the liquid to be tested is aqueous and dilutions arerequired, follow the procedures of Practice D1176 for propersample preparation.7.3 If the liquid to be te

31、sted is non-aqueous, the liquidspecimen is tested directly, without any changes or dilutions.Shake or stir the liquid to assure that it is homogeneous.7.4 If the liquid to be tested is non-aqueous, it should beassumed to be hygroscopic and its exposure to ambient airshould be as brief as possible.7.

32、5 Introduce approximately 40 mL of sample into thesampling cell. Importantmake sure that the liquid level is 3to 4 mL below the threads that are clearly marked on the innerwall of the sampling cell. This allows room for possiblethermal expansion of the specimen while heating without anyspillage or o

33、verflow, yet ensures full immersion of the sensor.7.6 With the sample introduced, lower the sensor into thesampling cell. Remove any trapped air bubbles near theinterface of the sensor and specimen.Air bubbles can introduceerrors and significantly degrade the resulting thermal propertiesmeasurement.

34、 Tap the sampling cell to dislodge any airbubbles, and then screw the sensor onto the sampling cell.7.7 Refer to Annex A2 to determine if pressure needs to beadded to the sampling cell. If pressure is required, follow themanufacturers instructions with regard to the introduction ofpressurization gas

35、es.7.8 Pressure of up to 241 kPa (35 psig) psi may be appliedto the sampling cell assembly. An inert gas (from an argon ornitrogen tank) is introduced into the sampling cell assemblythrough a pressure regulator. The level of pressure introducedis manually controlled and set to the desired level for

36、themeasurement. (WarningUse care when applying pressure tothe cell, and ensure the proper regulator is used for the intendedpressure range and type of inert gas to be used. See theoperating manual supplied with the equipment for moreinformation on applying pressure to the sampling cell.)8. Procedure

37、8.1 An ambient temperature measurement should be madeprior to proceeding with actual sample measurements. Oncecomplete, the controller is balanced and ready for use.8.2 When testing at other than ambient temperature, followthe instructions in the operating manual provided with thetemperature control

38、 equipment.8.3 Perform ten repetitive measurements of the thermalproperties of the test specimen:8.3.1 Set the measurement temperature and specify tenthermal property measurements to be made at that temperature.8.3.2 When the measurement temperature is reached, tenmeasurements will be automatically

39、performed at 30-s inter-vals. The results will be displayed on the computer monitor andcan be stored according to the System software.8.4 Refer to the Systems operating manual for furtherinstructions on equipment settings, taking and storingmeasurements, and exporting data files to spreadsheet soft-

40、ware.9. Report9.1 The report of the results of each test shall include thefollowing information with all data to be reported in SI unitsunless otherwise specified.The sampling cell holds the liquid sample and receives the hot wire sensor. The platinum resistance thermometer continuously measures the

41、 specimen temperature.The platinum hot wire and the system electronics measure the thermal conductivity and thermal diffusivity of the specimen.FIG. 2 Sampling Cell AssemblyD7896 1439.1.1 Date (mo./day/year) and time that each specimenmeasurement in the report was made.9.1.2 Temperature of each spec

42、imen test, C.9.1.3 Thermal conductivity, W/mK.9.1.4 The average of the ten thermal conductivity testiterations, W/mK.9.1.5 Thermal diffusivity, m2/s report as 106m2/s.9.1.6 The average of the ten thermal diffusivity testiterations, m2/s report as 106m2/s.9.1.7 Volumetric heat capacity, J/m3K, comput

43、ed as: (ther-mal conductivity) / (thermal diffusivity) report as kJ/m3K.9.1.8 The average of the ten volumetric heat capacitycalculations, J/m3K report as kJ/m3K.10. Precision and Bias410.1 The precision of this test method is based on aninterlaboratory study that was conducted in 2013. A singlelabo

44、ratory participated in this study, testing five liquids forthermal conductivity, thermal diffusivity and volumetric heatcapacity. Every “test result” represents an individual determi-nation. The laboratory reported ten replicate test results foreach liquid, 150 results total. Except for the use of o

45、nly onelaboratory, Practice E691 was followed for the design andanalysis of the data; the details are given in ASTM ResearchReport No. RR:D15-1034.10.1.1 Repeatability (r)The difference between repetitiveresults obtained by the same operator in a given laboratoryapplying the same test method with th

46、e same transient hot wirethermal conductivity measurement system under constant op-erating conditions on identical test material within shortintervals of time would, in the long run, in the normal andcorrect operation of the test method, exceed the repeatabilitylimits (r) shown in Tables 1-3 only in

47、 one case in 20.10.1.2 Reproducibility limits cannot be calculated from asingle laboratorys results.10.1.3 Any judgment in accordance with statement 10.1.1would normally have an approximate 95 % probability of beingcorrect, however the precision statistics obtained in this ILSmust not be treated as

48、exact mathematical quantities which areapplicable to all circumstances and uses. The limited numberof laboratories reporting replicate results essentially guaranteesthat there will be times when differences greater than predictedby the ILS results will arise, sometimes with considerablygreater or sm

49、aller frequency than the 95 % probability limitwould imply. Consider the repeatability limit as a generalguide, and the associated probability of 95 % as only a roughindicator of what can be expected.4Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D15-1034. ContactASTM CustomerService at serviceastm.org.FIG. 3 Close-Up of the Transient Hot Wire SensorTABLE 1 Thermal Conductivity (W/mK)AveragexRepeatabilityStandard DeviationsrRepeatabilityLim