1、Designation: C1043 06 (Reapproved 2010)Standard Practice forGuarded-Hot-Plate Design Using Circular Line-HeatSources1This standard is issued under the fixed designation C1043; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the yea
2、r 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 covers the design of a circular line-heat-source guarded hot plate for use in accordance with TestM
3、ethod C177.NOTE 1Test Method C177 describes the guarded-hot-plate apparatusand the application of such equipment for determining thermal transmis-sion properties of flat-slab specimens. In principle, the test methodincludes apparatus designed with guarded hot plates having eitherdistributed- or line
4、-heat sources.1.2 The guarded hot plate with circular line-heat sources isa design in which the meter and guard plates are circular plateshaving a relatively small number of heaters, each embeddedalong a circular path at a fixed radius. In operation, the heatfrom each line-heat source flows radially
5、 into the plate and istransmitted axially through the test specimens.1.3 The meter and guard plates are fabricated from acontinuous piece of thermally conductive material. The platesare made sufficiently thick that, for typical specimen thermalconductances, the radial and axial temperature variation
6、s in theguarded hot plate are quite small. By proper location of theline-heat source(s), the temperature at the edge of the meterplate can be made equal to the mean temperature of the meterplate, thus facilitating temperature measurements and thermalguarding.1.4 The line-heat-source guarded hot plat
7、e has been usedsuccessfully over a mean temperature range from 10to + 65C, with circular metal plates and a single line-heatsource in the meter plate. The chronological development ofthe design of circular line-heat-source guarded hot plates isgiven in Refs (1-9).21.5 This practice does not preclude
8、 (1) lower or highertemperatures; (2) plate geometries other than circular; (3)line-heat-source geometries other than circular; (4) the use ofplates fabricated from ceramics, composites, or other materials;or (5) the use of multiple line-heat sources in both the meterand guard plates.1.6 The values
9、stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.7 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
10、 and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3C168 Terminology Relating to Thermal InsulationC177 Test Method for Steady-State Heat Flux Measure-ments and Thermal Transmission Properties by Means ofthe Guarded
11、-Hot-Plate ApparatusC1044 Practice for Using a Guarded-Hot-PlateApparatus orThin-Heater Apparatus in the Single-Sided ModeE230 Specification and Temperature-Electromotive Force(EMF) Tables for Standardized Thermocouples2.2 ASTM Adjuncts:Line-Heat-Source Guarded-Hot-Plate Apparatus43. Terminology3.1
12、DefinitionsFor definitions of terms and symbols usedin this practice, refer to Terminology C168. For definitions ofterms relating to the guarded-hot-plate apparatus refer to TestMethod C177.3.2 Definitions of Terms Specific to This Standard:3.2.1 gap, na separation between the meter plate andguard p
13、late, usually filled with a gas or thermal insulation.3.2.2 guard plate, nthe outer ring of the guarded hot platethat encompasses the meter plate and promotes one-dimensional heat flow normal to the meter plate.1This practice is under the jurisdiction of ASTM Committee C16 on ThermalInsulation and i
14、s the direct responsibility of Subcommittee C16.30 on ThermalMeasurement.Current edition approved Sept. 1, 2010. Published January 2011. Originallyapproved 1985. Last previous edition approved in 2006 as C1043 06. DOI:10.1520/C1043-06R10.2The boldface numbers in parentheses refer to a list of refere
15、nces at the end ofthis practice.3For referenced ASTM 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.4Available from ASTM Headquar
16、ters. Order Adjunct: ADJC1043.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.3 guarded hot plate, nan assembly, consisting of ameter plate and a co-planar, concentric guard plate, thatprovides the heat input to the specimens.3.2
17、.4 line-heat-source, na thin or fine electrical heatingelement that provides uniform heat generation per unit length.3.2.5 meter area, nthe mathematical area through whichthe heat input to the meter plate flows normally under idealguarding conditions into the meter section of the specimen.3.2.6 mete
18、r plate, nthe inner disk of the guarded hot platethat contains one or more line-heat sources embedded in acircular profile and provides the heat input to the meter sectionof the specimens.3.2.7 meter section, nthe portion of the test specimen (orauxiliary insulation) through which the heat input to
19、the meterplate flows under ideal guarding conditions.4. Significance and Use4.1 This practice describes the design of a guarded hot platewith circular line-heat sources and provides guidance indetermining the mean temperature of the meter plate. Itprovides information and calculation procedures for:
20、 (1) con-trol of edge heat loss or gain (Annex A1); (2) location andinstallation of line-heat sources (Annex A2); (3) design of thegap between the meter and guard plates (Appendix X1); and(4) location of heater leads for the meter plate (Appendix X2).4.2 A circular guarded hot plate with one or more
21、 line-heatsources is amenable to mathematical analysis so that the meansurface temperature can be calculated from the measuredpower input and the measured temperature(s) at one or moreknown locations. Further, a circular plate geometry simplifiesthe mathematical analysis of errors resulting from hea
22、t gains orlosses at the edges of the specimens (see Refs (10, 11).4.3 In practice, it is customary to place the line-heatsource(s) in the meter plate at a prescribed radius such that thetemperature at the outer edge of the meter plate is equal to themean surface temperature over the meter area. Thus
23、, thedetermination of the mean temperature of the meter plate canbe accomplished with a small number of temperature sensorsplaced near the gap.4.4 A guarded hot plate with one or more line-heat sourceswill have a radial temperature variation, with the maximumtemperature differences being quite small
24、 compared to theaverage temperature drop across the specimens. Providedguarding is adequate, only the mean surface temperature of themeter plate enters into calculations of thermal transmissionproperties.4.5 Care must be taken to design a circular line-heat-sourceguarded hot plate so that the electr
25、ic-current leads to eachheater either do not significantly alter the temperature distri-butions in the meter and guard plates or else affect thesetemperature distributions in a known way so that appropriatecorrections can be made.4.6 The use of one or a few circular line-heat sources in aguarded hot
26、 plate simplifies construction and repair. Forroom-temperature operation, the plates are typically of one-piece metal construction and thus are easily fabricated to therequired thickness and flatness. The design of the gap is alsosimplified, relative to gap designs for distributed-heat-sourcehot pla
27、tes.4.7 In the single-sided mode of operation (see PracticeC1044), the symmetry of the line-heat-source design in theaxial direction minimizes errors due to undesired heat flowacross the gap.5. Design of a Guarded Hot Plate with Circular Line-Heat Source(s)5.1 GeneralThe general features of a circul
28、ar guarded-hot-plate apparatus with line-heat sources are illustrated in Fig.1. For the double-sided mode of operation, there are twospecimens, two cold plates, and a guarded hot plate with a gapbetween the meter and guard plates.The meter and guard platesare each provided with one (or a few) circul
29、ar line-heatsources.FIG. 1 Schematic of a Line-Heat-Source Guarded-Hot-Plate ApparatusC1043 06 (2010)25.2 SummaryTo design the meter and guard plates, usethe following suggested procedure: (1) establish the specifica-tions and priorities for the design criteria; (2) select anappropriate material for
30、 the plates; (3) determine the dimen-sions of the plates; (4) determine the type, number, andlocation of the line-heat source(s); (5) design the supportsystem for the plates; and (6) determine the type, number, andlocation of the temperature sensors.5.3 Design CriteriaEstablish specifications for th
31、e fol-lowing parameters of the guarded hot-plate apparatus: (1)specimen diameter; (2) range of specimen thicknesses; (3)range of specimen thermal conductances; (4) characteristics ofspecimen materials (for example, stiffness, mechanical com-pliance, density, hardness); (5) range of hot-side and cold
32、-sidetest temperatures; (6) orientation of apparatus (vertical orhorizontal heat flow); and (7) required measurement precision.NOTE 2The priority assigned to the design parameters depends on theapplication. For example, an apparatus for high-temperature may neces-sitate a different precision specifi
33、cation than that for a room-temperatureapparatus. Examples of room-temperature apparatus are available in theadjunct.45.4 MaterialSelect the material for the guarded hot plateby considering the following criteria:5.4.1 Ease of FabricationFabricate the guarded hot platefrom a material that has suitab
34、le thermal and mechanicalproperties and which can be readily fabricated to the desiredshapes and tolerances, as well as facilitate assembly.5.4.2 Thermal StabilityFor the intended range of tempera-ture, select a material for the guarded hot plate that isdimensionally stable, resistant to oxidation,
35、and capable ofsupporting its own weight, the test specimens, and accommo-dating the applied clamping forces without significant distor-tion. The coefficient of thermal expansion must be known inorder to calculate the meter area at different temperatures.5.4.3 Thermal ConductivityTo reduce the (small
36、) radialtemperature variations across the guarded hot plate, select amaterial having a high thermal conductivity. For cryogenic ormodest temperatures, it is recommended that a metal such ascopper, aluminum, silver, gold or nickel be selected. Forhigh-temperature (up to 600 or 700C) use in air, nicke
37、l or asingle-compound ceramic, such as aluminum oxide, aluminumnitride, or cubic boron nitride is recommended.5.4.4 Heat CapacityTo achieve thermal equilibriumquickly, select a material having a low volumetric heat capacity(product of density and specific heat). Although aluminum,silver, and gold, f
38、or example, have volumetric heat capacitieslower than copper, as a practical matter, either copper oraluminum is satisfactory.NOTE 3Heat capacity is particularly important when acquiring testdata by decreasing the mean temperature. Since the meter plate, for mostdesigns, can only lose heat through t
39、he test specimens, the meter plate maycool quite slowly.5.4.5 Thermal EmittanceTo achieve a uniform, high ther-mal emittance, select a plate material that will accept a suitablesurface treatment. The treatment should also provide goodoxidation resistance. For modest temperatures, various highemittan
40、ce paints can be used for copper, silver, gold, or nickel.For aluminum, a black anodized treatment provides a uni-formly high emittance. For high-temperature, most ceramicshave an inherently high thermal emittance and nickel and itsalloys can be given a fairly stable oxide coating. In any case,the t
41、hermal emittance should not change significantly withaging.5.5 Guarded-Hot-Plate DimensionsSelect the geometri-cal dimensions of the guarded hot plate to provide an accuratedetermination of the thermal transmission properties.NOTE 4The accurate determination of thermal transmission proper-ties requi
42、res that the heat input to the meter plate flows normally throughthe specimens to the cold plates. One-dimensional heat flow is attained byproper selection of the diameter of the meter plate relative to the diameterof the guard plate while also considering (1) the specimen thermalconductivities; (2)
43、 specimen thicknesses; (3) edge insulation; and, (4)secondary guarding, if any.5.5.1 Meter Plate DiameterThe diameter shall be largeenough so that the meter section of the specimens is statisti-cally representative of the material. Conversely, the diameterneeds to be sufficiently smaller than the di
44、ameter of the guardplate so that adequate guarding from edge heat losses can beachieved (see 5.5.2).NOTE 5The first requirement is particularly critical for low-densityinsulations that may be inhomogeneous. The second requirement isnecessary in order to provide adequate guarding for the testing of t
45、hespecimen materials and thicknesses of concern.5.5.2 Guard Plate DiameterUse Annex A1 to determineeither the diameter of the guard plate for a given meter platediameter, or the diameter of the meter plate for a given guardplate diameter. Specifically, determine the combinations ofdiameters of the m
46、eter plate and guard plate that will berequired so that the edge-heat-loss error will not be excessivefor the thickest specimens, with the highest lateral thermalconductances. If necessary, calculate the edge heat loss fordifferent edge insulation and secondary-guarding conditions.NOTE 6For example,
47、 when testing relatively thin specimens ofinsulation, it may be sufficient to maintain the ambient temperature atessentially the mean temperature of the specimens and to use minimaledge insulation without secondary guarding. However, for thicker con-ductive specimens, edge insulation and stringent s
48、econdary guarding maybe necessary to achieve the desired test accuracy.5.5.3 Guarded-Hot-Plate ThicknessThe thickness shouldbe large enough to provide proper structural rigidity, and havea large lateral thermal conductance, thus minimizing radialtemperature variations in the plate. Conversely, a lar
49、ge thick-ness will increase the heat capacitance of the plate and thusadversely affect the (rapid) achievement of thermal equilib-rium, and reduce the thermal isolation between the meter plateand the guard plate.5.5.4 Gap WidthThe gap shall have a uniform width suchthat the gap area, in the plane of the surface of the guarded hotplate, shall be less than 3 % of the meter area. In any case, thewidth of the gap shall not exceed the limitations given in TestMethod C177. The width of the gap is a compromise betweenincreasing the separation in order to re
