1、Designation: E 2584 07Standard Practice forThermal Conductivity of Materials Using a ThermalCapacitance (Slug) Calorimeter1This standard is issued under the fixed designation E 2584; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision,
2、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 practice describes a technique for the determinationof the apparent thermal conductivity, la, of mat
3、erials. It is forsolid materials with apparent thermal conductivities in theapproximate range 0.02 la 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
4、been foundspecifically useful in testing fire resistive materials that are both reactiveand undergo significant dimensional changes during a high temperatureexposure.1.2 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of t
5、he 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:2C 1113 Test Method for Thermal Conductivity of Refracto-ries by Hot Wire (Platinum Resistance Thermometer
6、Tech-nique)D 2214 Test Method for Estimating the Thermal Conduc-tivity of Leather with the Cenco-Fitch ApparatusE 220 Test Method for Calibration of Thermocouples ByComparison TechniquesE 230 Specification and Temperature-Electromotive Force(EMF) Tables for Standardized ThermocouplesE 457 Test Metho
7、d for Measuring Heat-Transfer Rate Usinga Thermal Capacitance (Slug) CalorimeterE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 Definitions:3.1.1 thermal conductivity, lthe time rate of heat flow,under steady conditions, through unit
8、 area, per unit temperaturegradient in the direction perpendicular to the area.3.1.2 apparent thermal conductivity, lawhen other modesof heat transfer (and mass transfer) through a material arepresent in addition to thermal conduction, the results of themeasurements performed according to this pract
9、ice will repre-sent the apparent or effective thermal conductivity for thematerial tested.3.2 Symbols: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
10、 = heat flow, WT = absolute temperature, KTinnerSSS= mean temperature of the stainless steel slug, KTouterSPEC= mean temperature of outer (exposed) specimensurfaces, KTmeanSPEC= mean temperature of specimen, KDT = temperature difference across the specimen, given by(TouterSPEC TinnerSSS), K,l = ther
11、mal conductivity, W/(mK)la= apparent thermal conductivity, W/(mK)rSPEC= bulk density of specimen being tested, kg/m33.3 Subscripts/Superscripts:SPEC = material specimen being evaluatedSSS = stainless steel slug (thermal capacitance transducer)4. Summary of Practice4.1 Principle of OperationIn princi
12、ple, a slug of ther-mally conductive 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. When the outer surface ofthis assembly is exposed to a temperat
13、ure 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 its specific heat capacity. With theknowledge of these propert
14、ies, the rate of temperature rise of1This practice is under the jurisdiction of ASTM Committee E37 on ThermalMeasurements and is the direct responsibility of Subcommittee E37.05 on Thermo-physical Properties.Current edition approved Sept. 1, 2007. Published November 2007.2For referenced ASTM standar
15、ds, 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 Harbor Drive, PO Box C700, West Conshohocken, PA
16、19428-2959, United States.Copyright by ASTM Intl (all rights reserved); Fri Oct 31 01:42:58 EST 2008Downloaded/printed byGuo Dehua (CNIS) pursuant to License Agreement. No further reproductions authorized.the slug is in direct proportion to the heat flux entering it. Thus,under these conditions, the
17、 slug becomes a flux-gaugingdevice. From this measured flux, along with the measuredthermal gradient across 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
18、reversed. Still, from the measuredflux and thermal gradient, the apparent thermal conductivitycan be calculated.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
19、due to:4.2.1 Thickness non-uniformity of the outer layer.4.2.2 Inhomogeneity (chemical or microstructural) 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 (thermo-couples), etc. that are unavoidable parts
20、of a practical embodi-ment.4.2.5 Delamination of the specimen from the slugs surface(gap formation).NOTE 2The 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, be
21、comingprobably the most important source of uncertainty in the measurement.For low-density porous materials, 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 conf
22、igurations, a few of which are listedbelow:4.3.1 For pipe (tubular) insulations, a cylindrical slug is tobe used. 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
23、material covering:4.3.2.1 Both large faces of the slab, with the edges heavilyinsulated.4.3.2.2 One large face 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 sandwic
24、h testspecimen is prepared consisting of twin specimens of thematerial, of known mass and known and nominally identicalthickness, between which is sandwiched a stainless steelthermal capacitance transducer (slug) of known mass. Theentire sandwich is placed between two (high temperature)metal retaini
25、ng plates, and the bolts holding the configurationtogether are tightened with a torque not to exceed 1 kgm, tomaintain 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 s
26、pecimens versus time are measured during thecourse of multiple heating and cooling cycles. Under steady-state (constant rate) heating or cooling conditions, the apparentthermal conductivity is derived from the measured temperaturegradients across the two specimens, the measured rate oftemperature in
27、crease/decrease of the steel slug, and the knownmasses and specific heat capacities of the specimens and thestainless steel slug. In principle, the test apparatus is similar tothe Cenco-Fitch apparatus (1)3that is employed in Test MethodD 2214 for determining the thermal conductivity of leather.Meas
28、uring the heat transfer through a material by using athermal capacitance transducer is similar to the approach that isemployed for measuring heat-transfer rates in Test MethodE 457.4.4.2 Single Specimen (One-Sided)Similarly to the above,one unknown specimen is placed on one side of the slug andanoth
29、er known specimen (buffer) of extremely high thermalresistance is placed on the other side. In this instance, the 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 th
30、e slugthrough this face are negligible.5. Significance and Use5.1 This practice is useful for testing materials in general,including composites and layered types.5.2 The practice is especially useful for materials whichundergo significant reactions and/or local dimensional changesduring exposure to
31、elevated temperatures and thus are difficultto evaluate using existing standard test methods such as TestMethod C 1113.5.3 Performing the test over multiple heating/cooling cyclesallows an assessment of the influence of reactions, phasechanges, and mass transfer of reactions gases (e.g., steam) onth
32、e thermal performance.NOTE 3This method has been found to be especially applicable totesting fire resistive 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 tempe
33、rature service. Dimensions of the steel slug andthe holes to be drilled for temperature sensor insertion areprovided in Fig. 1. These dimensions and configuration areused for expediency in further discussion, without the intent ofposing restrictions on other sizes or configurations, or hinder-ing th
34、e 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 specimens sh
35、all 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 the tem
36、perature sensors.3The boldface numbers in parentheses refer to the list of references at the end ofthis standard.E2584072Copyright by ASTM Intl (all rights reserved); Fri Oct 31 01:42:58 EST 2008Downloaded/printed byGuo Dehua (CNIS) pursuant to License Agreement. No further reproductions authorized.
37、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 the anticipated temperat
38、ure range, have a very lowl, 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. Typi-cally, these materials exhibi
39、t a room temperature thermalconductivity as low as 0.02 W/(mK) and a thermal conduc-tivity 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 temperature controlled enviro
40、nment 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 test. Typically, the
41、 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 ramps. For example, th
42、efollowing temperature setpoints (versus time) have been suc-cessfully employed in the past: 538C after 45 min, 704C after70 min, 843C after 90 min, 927C after 105 min, and 1010Cafter 2 h.6.4 Temperature Sensors:6.4.1 There shall be a minimum of three temperaturesensors to be inserted into the pre-
43、drilled holes in the stainlesssteel slug. The multiple sensors are useful to indicate thevalidity of one-dimensional heat transfer through the speci-men(s) to the steel slug. Temperature sensors may also bemounted in milled grooves on the exterior surface of thespecimens, one sensor per specimen. Wh
44、en 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 reasonable topostulate that the surface temperature of the slug is identical toits mean t
45、emperature. When comparatively high thermal con-ductivity specimens are used, it is practical to embed atemperature sensor near to or on the slugs surface.FIG. 1 Schematic of AISI 304 Stainless Steel Slug CalorimeterE2584073Copyright by ASTM Intl (all rights reserved); Fri Oct 31 01:42:58 EST 2008Do
46、wnloaded/printed byGuo Dehua (CNIS) pursuant to License Agreement. No further reproductions authorized.6.4.3 Any sensor possessing adequate accuracy may be usedfor temperature measurement. Type K or Type N thermo-couples are normally employed. Their small size and ease ofmanufacturing are distinct a
47、dvantages. The sensors simplymust fit into the holes present in the thermal capacitancecalorimeter, where they can be easily inserted during theassembly of the configuration within the temperature-controlled environment.6.4.4 When thermocouples are employed, a constant tem-perature reference shall a
48、lways be provided for all coldjunctions. This reference can be an ice-cold slurry, a constanttemperature zone box, or an integrated cold junction compen-sation (CJC) sensor.All thermocouples shall be fabricated fromeither calibrated thermocouple wire or from wire that has beencertified by the suppli
49、er to be within the limits of errorspecified in Table 1 of Specification E 230. Thermocouples canbe calibrated as described in Specification E 220.6.5 Data Acquisition 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 minute for example) intervals. As examples, data may beacquired using a thermocouple input module or a voltmeter/mult
