1、Designation: E2584 14Standard Practice forThermal Conductivity of Materials Using a ThermalCapacitance (Slug) Calorimeter1This standard is issued under the fixed designation E2584; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, th
2、e 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 practice describes a technique for the determinationof the apparent thermal conductivity, a, of materia
3、ls. It is forsolid materials with apparent thermal conductivities in theapproximate range 0.02 a 2 W/(mK) over the approxi-mate temperature range between 300 K and 1100 K.NOTE 1While the practice should also be applicable to determiningthe thermal conductivity of non-reactive materials, it has been
4、foundspecifically useful in testing fire resistive materials that are both reactiveand undergo significant dimensional changes during a high temperatureexposure.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 This standa
5、rd 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 to use.2. Referenced Documents2.1 AST
6、M Standards:2C1113 Test Method for Thermal Conductivity of Refracto-ries by Hot Wire (Platinum Resistance ThermometerTechnique)D2214 Test Method for Estimating the Thermal Conductiv-ity of Leather with the Cenco-FitchApparatus (Withdrawn2008)3E177 Practice for Use of the Terms Precision and Bias inA
7、STM Test MethodsE220 Test Method for Calibration of Thermocouples ByComparison TechniquesE230 Specification and Temperature-Electromotive Force(EMF) Tables for Standardized ThermocouplesE457 Test Method for Measuring Heat-Transfer Rate Usinga Thermal Capacitance (Slug) CalorimeterE691 Practice for C
8、onducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 Definitions:3.1.1 thermal conductivity, the time rate of heat flow,under steady conditions, through unit area, per unit temperaturegradient in the direction perpendicular to the area.3.1.2 apparent thermal
9、 conductivity, awhen other modesof heat transfer (and mass transfer) through a material arepresent in addition to thermal conduction, the results of themeasurements performed according to this practice will repre-sent the apparent or effective thermal conductivity for thematerial tested.3.2 Symbols:
10、A = specimen area normal to heat flux direction, m2Cp= specific heat capacity, J/(kgK)F = heating or cooling rate, (K/s)L = thickness of a specimen (slab) in heat transfer direc-tion, mM = mass, kgQ = heat flow, WT = absolute temperature, KTinnerSSS= mean temperature of the stainless steel slug, KTo
11、uterSPEC= mean temperature of outer (exposed) specimensurfaces, KTmeanSPEC= mean temperature of specimen, KT = temperature difference across the specimen, given by(TouterSPEC TinnerSSS), K = thermal conductivity, W/(mK)a= apparent thermal conductivity, W/(mK)SPEC= bulk density of specimen being test
12、ed, kg/m33.3 Subscripts/Superscripts:SPEC = material specimen being evaluatedSSS = stainless steel slug (thermal capacitance transducer)1This practice is under the jurisdiction of ASTM Committee E37 on ThermalMeasurements and is the direct responsibility of Subcommittee E37.05 on Thermo-physical Pro
13、perties.Current edition approved Feb. 15, 2014. Published March 2014. Originallyapproved in 2007. Last previous edition approved in 2010 as E2584 10. DOI:10.1520/E2584-14.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Ann
14、ual 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 Conshohocken, PA 19428-2959. United
15、 States14. Summary of Practice4.1 Principle of OperationIn principle, a slug of thermallyconductive metal, capable of withstanding elevatedtemperatures, is surrounded with another material of a uniformthickness (the specimen) whose thermal conductivity is sub-stantially lower than that of the slug.
16、When the outer surface ofthis assembly is exposed to a temperature above that of theslug, heat will pass through the outer layer, causing a tempera-ture rise in the slug itself. The temperature rise of the slug iscontrolled by the amount and rate of heat conducted to itssurface (flux), its mass, and
17、 its specific heat capacity. With theknowledge of these properties, the rate of temperature rise ofthe slug is in direct proportion to the heat flux entering it. Thus,under these conditions, the slug becomes a flux-gaugingdevice. From this measured flux, along with the measuredthermal gradient acros
18、s the outer (specimen) layer, the apparentthermal conductivity of the specimen can be calculated. Whenthe heat source is removed, during natural cooling, the direc-tion of the heat flow will be reversed. Still, from the measuredflux and thermal gradient, the apparent thermal conductivitycan be calcu
19、lated.4.2 Boundary ConditionsThe ideal model describedabove is based on heat flow toward the slug, perpendicularly tothe specimen, and always through the specimen. Deviatingfrom ideality can be due to:4.2.1 Thickness non-uniformity of the outer layer.4.2.2 Inhomogeneity (chemical or microstructural)
20、 of theouter layer.4.2.3 Parasitic paths through cracks, gaps or other mechani-cally induced paths.4.2.4 Parasitic paths through wires, sheaths(thermocouples), etc., that are unavoidable parts of a practicalembodiment.4.2.5 Delamination of the specimen from the slugs surface(gap formation).NOTE 2The
21、 user of this method should be very aware of the fact thatthe contact resistance between the specimen(s) and the slug may notalways be neglected, and in some cases may be even significant, becomingprobably the most important source of uncertainty in the measurement.For low-density porous materials,
22、however, it was found that, generally,the contact resistance between the specimen(s) and the slug may beneglected.4.3 ConfigurationsThis method lends itself to many pos-sible geometrical configurations, a few of which are listedbelow:4.3.1 For pipe (tubular) insulations, a cylindrical slug is tobe u
23、sed. End faces are to be blocked with insulation.4.3.2 For flat plate stock (insulating boards, bulk materials,etc.), a rectangular shaped slug is considered most practical,with the specimen material covering:4.3.2.1 Both large faces of the slab, with the edges heavilyinsulated.4.3.2.2 One large fac
24、e of the slab, with the other face andthe edges heavily insulated.4.4 OperationFor simplicity, only the rectangular em-bodiment is described below:4.4.1 Twin Specimens (Double-Sided)A sandwich testspecimen is prepared consisting of twin specimens of thematerial, of known mass and known and nominally
25、 identicalthickness, between which is sandwiched a stainless steelthermal capacitance transducer (slug) of known mass. Theentire sandwich is placed between two (high temperature)metal retaining plates, and the bolts holding the configurationtogether are tightened with a torque not to exceed 1 kgm, t
26、omaintain a slight compressive load on the specimen. Theassembled specimen is placed in a temperature-controlledenvironment and the temperatures of the steel slug and exposedsurfaces of the specimens versus time are measured during thecourse of multiple heating and cooling cycles. Under steady-state
27、 (constant rate) heating or cooling conditions, the apparentthermal conductivity is derived from the measured temperaturegradients across the two specimens, the measured rate oftemperature increase/decrease of the steel slug, and the knownmasses and specific heat capacities of the specimens and thes
28、tainless steel slug. In principle, the test apparatus is similar tothe Cenco-Fitch apparatus (1)4that is employed inTest MethodD2214 for determining the thermal conductivity of leather.Measuring the heat transfer through a material by using athermal capacitance transducer is similar to the approach
29、that isemployed for measuring heat-transfer rates in Test MethodE457.4.4.2 Single Specimen (One-Sided)Similarly to the above,one unknown specimen is placed on one side of the slug andanother known specimen (buffer) of extremely high thermalresistance is placed on the other side. In this instance, th
30、e outersurface of the buffer may be heated at the same time as theother side, just like in case of a twin specimen, or may be leftunheated if it can be established that heat losses from the slugthrough this face are negligible.5. Significance and Use5.1 This practice is useful for testing materials
31、in general,including composites and layered types.5.2 The practice is especially useful for materials whichundergo significant reactions or local dimensional changes, orboth, during exposure to elevated temperatures and thus aredifficult to evaluate using existing standard test methods suchas Test M
32、ethod C1113.5.3 Performing the test over multiple heating/cooling cyclesallows an assessment of the influence of reactions, phasechanges, and mass transfer of reactions gases (for example,steam) on the thermal performance.NOTE 3This method has been found to be especially applicable totesting fire re
33、sistive materials.6. Apparatus6.1 Thermal Capacitance (Slug) Calorimeter:6.1.1 The steel slug shall be manufactured from AISI 304stainless steel or any other well characterized material ofproper temperature service. Dimensions of the steel slug andthe holes to be drilled for temperature sensor inser
34、tion areprovided in Fig. 1. These dimensions and configuration areused for expediency in further discussion, without the intent of4The boldface numbers in parentheses refer to the list of references at the end ofthis standard.E2584 142posing restrictions on other sizes or configurations, or hinder-i
35、ng the adaptation of other engineering solutions.6.1.2 Two high temperature metal retaining plates, nomi-nally of size 200 by 200 mm, shall be employed to hold thetwin specimens, steel slug, and surrounding guard insulation inplace and under a slight compression.6.1.3 The steel slug and twin specime
36、ns shall be surroundedon all sides by an appropriate high temperature insulation,nominally of 25 mm thickness. Three holes shall be drilledthrough the section of insulation that covers the top of the slugin direct line with the corresponding milled holes in the steelslug to allow for insertion of th
37、e temperature sensors.6.2 Insulation Materials:6.2.1 A large variety of materials exists for providing theguard insulation that surrounds the stainless steel slug andspecimens. Several factors must be considered during selectionof the most appropriate insulation. The insulation must bestable over th
38、e anticipated temperature range, have a very low, and be easy to handle, cut, and insert holes. In addition, theinsulation should not contaminate system components, it musthave a low toxicity, and it should not conduct electricity. Ingeneral, microporous insulation boards are employed.Typically, the
39、se materials exhibit a room temperature thermalconductivity as low as 0.02 W/(mK) and a thermal conductiv-ity of less than 0.04 W/(mK) at 1073 K. These values aremuch lower than those of typical materials that can be testedusing this method.6.3 Temperature-Controlled Environment:6.3.1 The temperatur
40、e controlled environment shall consistof an enclosed volume in which the temperature can becontrolled during heating and monitored during (natural)cooling. The heating units shall be capable of supplyingsufficient energy to achieve the temperatures required for theevaluation of the materials under t
41、est. Typically, the heatedenvironment ranges in temperature between room temperatureand 1000C during the course of a single heating/cooling cycle.6.3.2 One example would be a temperature-controlled fur-nace with an electronic control system that allows the program-ming of one or more temperature ram
42、ps. For example, thefollowing temperature setpoints (versus time) have been suc-cessfully employed in the past: 538C after 45 min, 704Cafter 70 min, 843C after 90 min, 927C after 105 min, and1010C after 2 h.6.4 Temperature Sensors:6.4.1 There shall be a minimum of three temperaturesensors to be inse
43、rted into the pre-drilled holes in the stainlesssteel slug. The multiple sensors are useful to indicate theFIG. 1 Schematic of AISI 304 Stainless Steel Slug CalorimeterE2584 143validity of one-dimensional heat transfer through the speci-men(s) to the steel slug. Temperature sensors may also bemounte
44、d in milled grooves on the exterior surface of thespecimens, one sensor per specimen. When this is not possible,the exposed face of the specimen may be assumed to have atemperature equal to the measured temperature of thetemperature-controlled environment.6.4.2 For the purposes of this test, it is r
45、easonable topostulate that the surface temperature of the slug is identical toits mean temperature. When comparatively high thermal con-ductivity specimens are used, it is practical to embed atemperature sensor near to or on the slugs surface.6.4.3 Any sensor possessing adequate accuracy may be used
46、for temperature measurement. Type K or Type N thermo-couples are normally employed. Their small size and ease ofmanufacturing are distinct advantages. The sensors simplymust fit into the holes present in the thermal capacitancecalorimeter, where they can be easily inserted during theassembly of the
47、configuration within the temperature-controlled environment.6.4.4 When thermocouples are employed, a constant tem-perature reference shall always be provided for all coldjunctions. This reference can be an ice-cold slurry, a constanttemperature zone box, or an integrated cold junction compen-sation
48、(CJC) sensor.All thermocouples shall be fabricated fromeither calibrated thermocouple wire or from wire that has beencertified by the supplier to be within the limits of errorspecified in Table 1 of Specification E230. Thermocouples canbe calibrated as described in Test Method E220.6.5 Data Acquisit
49、ion SystemWhile manual acquisition ofthe data is possible, for convenience, increased reliability, andavoidance of transcription errors, it is recommended that anappropriate data acquisition system be employed to automati-cally monitor all of the temperature sensors at regular (1 minfor example) intervals. As examples, data may be acquiredusing a thermocouple input module or a voltmeter/multimetersystem. In the latter case, the measured signals shall beconverted to temperatures using the appropriate tables fromSpecification E230.7. Hazards7.1 I
