1、Designation: C1043 06 (Reapproved 2010) C1043 16Standard 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
2、, 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 practice covers the design of a circular line-heat-source guarded hot plate for use in accordance w
3、ithTest Method C177.NOTE 1Test Method C177 describes the guarded-hot-plate apparatus and the application of such equipment for determining thermal transmissionproperties of flat-slab specimens. In principle, the test method includes apparatus designed with guarded hot plates having either distribute
4、d- or line-heatsources.1.2 The guarded hot plate with circular line-heat sources is a design in which the meter and guard plates are circular plateshaving a relatively small number of heaters, each embedded along a circular path at a fixed radius. In operation, the heat from eachline-heat source flo
5、ws radially into the plate and is transmitted axially through the test specimens.1.3 The meter and guard plates are fabricated from a continuous piece of thermally conductive material. The plates are madesufficiently thick that, for typical specimen thermal conductances, the radial and axial tempera
6、ture variations in the guarded hotplate are quite small. By proper location of the line-heat source(s), the temperature at the edge of the meter plate can be is madeequal to the mean temperature of the meter plate, thus facilitating temperature measurements and thermal guarding.1.4 The line-heat-sou
7、rce guarded hot plate has been used successfully over a mean temperature range from 10 to + 65C, withcircular metal plates and a single line-heat source in the meter plate. The chronological development of the design of circularline-heat-source guarded hot plates is given in Refs (1-9).21.5 This pra
8、ctice does not preclude (1) lower or higher temperatures; (2) plate geometries other than circular; (3)line-heat-source geometries other than circular; (4) the use of plates fabricated from ceramics, composites, or other materials; or(5) the use of multiple line-heat sources in both the meter and gu
9、ard plates.1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to
10、establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:3C168 Terminology Relating to Thermal InsulationC177 Test Method for Steady-State Heat Flux Measurements and Thermal Transmission Properti
11、es by Means of theGuarded-Hot-Plate ApparatusC1044 Practice for Using a Guarded-Hot-Plate Apparatus or Thin-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
12、Apparatus41 This practice is under the jurisdiction ofASTM Committee C16 on Thermal Insulation and is the direct responsibility of Subcommittee C16.30 on Thermal Measurement.Current edition approved Sept. 1, 2010March 1, 2016. Published January 2011March 2016. Originally approved in 1985. Last previ
13、ous edition approved in 20062010 asC1043 06.C1043 06 (2010). DOI: 10.1520/C1043-06R10.10.1520/C1043-16.2 The boldface numbers in parentheses refer to a list of references at the end of this practice.3 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service
14、at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.4 Available from ASTM Headquarters. Order Adjunct: ADJC1043.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an
15、indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to
16、be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13. Terminology3.1 DefinitionsFor definitions of terms and symbols used in this practice, refer to Terminology C168. For definitions of termsrelating t
17、o the guarded-hot-plate apparatus refer to Test Method C177.3.2 Definitions of Terms Specific to This Standard:3.2.1 gap, na separation between the meter plate and guard plate, usually filled with a gas or thermal insulation.3.2.2 guard plate, nthe outer ring of the guarded hot plate that encompasse
18、s the meter plate and promotes one-dimensionalheat flow normal to the meter plate.3.2.3 guarded hot plate, nan assembly, consisting of a meter plate and a co-planar, concentric guard plate,plate that providesthe heat input to the specimens.3.2.4 line-heat-source, na thin or fine electrical heating e
19、lement that provides uniform heat generation per unit length.3.2.5 meter area, nthe mathematical area through which the heat input to the meter plate flows normally under ideal guardingconditions into the meter section of the specimen.3.2.6 meter plate, nthe inner disk of the guarded hot plate that
20、contains one or more line-heat sources embedded in a circularprofile and provides the heat input to the meter section of the specimens.3.2.7 meter section, nthe portion of the test specimen (or auxiliary insulation) through which the heat input to the meter plateflows under ideal guarding conditions
21、.4. Significance and Use4.1 This practice describes the design of a guarded hot plate with circular line-heat sources and provides guidance indetermining the mean temperature of the meter plate. It provides information and calculation procedures for: (1) control of edgeheat loss or gain (AnnexA1); (
22、2) location and installation of line-heat sources (AnnexA2); (3) design of the gap between the meterand 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 line-heat sources is amenable to mathematical analy
23、sis so that the meansurface temperature can be is calculated from the measured power input and the measured temperature(s) at one or more knownlocations. Further, a circular plate geometry simplifies the mathematical analysis of errors resulting from heat gains or losses atthe edges of the specimens
24、 (see Refs (10, 11).4.3 In practice, it is customary to place the line-heat source(s) The line-heat source(s) is (are) placed in the meter plate at aprescribed radius such that the temperature at the outer edge of the meter plate is equal to the mean surface temperature over themeter area. Thus, the
25、 determination of the mean temperature of the meter plate can be is accomplished with a small number oftemperature sensors placed near the gap.4.4 A guarded hot plate with one or more line-heat sources will have a radial temperature variation, with the maximumtemperature differences being quite smal
26、l compared to the average temperature drop across the specimens. Provided guarding isadequate, only the mean surface temperature of the meter plate enters into calculations of thermal transmission properties.4.5 Care mustshall be taken to design a circular line-heat-source guarded hot plate so that
27、the electric-current leads to eachheater either do not significantly alter the temperature distributions in the meter and guard plates or else affect these temperaturedistributions in a known way so that appropriate corrections can be made.are applied.4.6 The use of one or a few circular line-heat s
28、ources in a guarded hot plate simplifies construction and repair. Forroom-temperature operation, the plates are typically of one-piece metal construction and thus are easily fabricated to the requiredthickness and flatness. The design of the gap is also simplified, relative to gap designs for distri
29、buted-heat-source hot plates.4.7 In the single-sided mode of operation (see Practice C1044), the symmetry of the line-heat-source design in the axialdirection minimizes errors due to undesired heat flow across the gap.5. Design of a Guarded Hot Plate with Circular Line-Heat Source(s)5.1 GeneralThe g
30、eneral features of a circular guarded-hot-plate apparatus with line-heat sources are illustrated in Fig. 1. Forthe double-sided mode of operation, there are two specimens, two cold plates, and a guarded hot plate with a gap between the meterand guard plates. The meter and guard plates are each provi
31、ded with one (or a few) circular line-heat sources.5.2 SummaryTo design the meter and guard plates, use the following suggested procedure: (1) establish the specifications andpriorities for the design criteria; (2) select an appropriate material for the plates; (3) determine the dimensions of the pl
32、ates; (4)determine the type, number, and location of the line-heat source(s); (5) design the support system for the plates; and (6) determinethe type, number, and location of the temperature sensors.5.3 Design CriteriaEstablish specifications for the following parameters of the guarded hot-plate app
33、aratus: (1) specimendiameter; (2) range of specimen thicknesses; (3 ) range of specimen thermal conductances; (4) characteristics of specimenmaterials (for example, stiffness, mechanical compliance, density, hardness); (5) range of hot-side and cold-side test temperatures;(6) orientation of apparatu
34、s (vertical or horizontal heat flow); and (7) required measurement precision.C1043 162NOTE 2The priority assigned to the design parameters depends on the application. For example, an apparatus for high-temperature maywillnecessitate a different precision specification than that for a room-temperatur
35、e apparatus. Examples of room-temperature Technical data and designdrawings for two line-heat-source guarded-hot-plate apparatus are available in the adjunct.45.4 MaterialSelect the material for the guarded hot plate by considering the following criteria:5.4.1 Ease of FabricationFabricate the guarde
36、d hot plate from a material that has suitable thermal and mechanical propertiesand which can be is readily fabricated to the desired shapes and tolerances, as well as facilitate assembly.5.4.2 Thermal StabilityFor the intended range of temperature, select a material for the guarded hot plate that is
37、 dimensionallystable, resistant to oxidation, and capable of supporting its own weight, the test specimens, and accommodating the appliedclamping forces without significant distortion. The coefficient of thermal expansion mustshall be known in order to calculate themeter area at different temperatur
38、es.5.4.3 Thermal ConductivityTo reduce the (small) radial temperature variations across the guarded hot plate, select a materialhaving a high thermal conductivity. For cryogenic or modest temperatures, it is recommended that select a metal such as copper,aluminum, silver, gold or nickel be selected.
39、 nickel. For high-temperature (up to 600 or 700C) use in air, select nickel or asingle-compound ceramic, such as aluminum oxide, aluminum nitride, or cubic boron nitride is recommended.nitride.5.4.4 Heat CapacityTo achieve thermal equilibrium quickly, select a material having a low volumetric heat c
40、apacity (productof density and specific heat).Although aluminum, silver, and gold, for example, have volumetric heat capacities lower than copper,as a practical matter, either copper or aluminum is satisfactory.NOTE 3Heat capacity is particularly important when acquiring test data by decreasing the
41、mean temperature. Since the meter plate, for most designs,can only lose heat through the test specimens, the meter plate may cool quite slowly.5.4.5 Thermal EmittanceTo achieve a uniform, high thermal emittance, select a plate material that will accept a suitablesurface treatment. The treatment shou
42、ldshall also provide good oxidation resistance. For modest temperatures, various highemittance paints can be are used for copper, silver, gold, or nickel. For aluminum, a black anodized treatment provides a uniformlyhigh emittance. For high-temperature, most ceramics have an inherently high thermal
43、emittance and nickel and its alloys can begiven emittance. Nickel and its alloys form a fairly stable oxide coating. In any case, the thermal emittance should not changesignificantly with aging.coating at higher temperatures.5.5 Guarded-Hot-Plate DimensionsSelect the geometrical dimensions of the gu
44、arded hot plate to provide an accuratedetermination of the thermal transmission properties.NOTE 3The accurate determination of thermal transmission properties requires that the heat input to the meter plate flows normally through thespecimens to the cold plates. One-dimensional heat flow is attained
45、 by proper selection of the diameter of the meter plate relative to the diameter of theguard plate while also considering (1) the specimen thermal conductivities; (2) specimen thicknesses; (3) edge insulation; and, (4) secondary guarding,if any.5.5.1 Meter Plate DiameterThe diameter shall be large e
46、nough so that the meter section of the specimens is statisticallyrepresentative of the material. Conversely, the diameter needs to be sufficiently smaller than the diameter of the guard plate so thatadequate guarding from edge heat losses can be achieved (see 5.5.2).NOTE 5The first requirement is pa
47、rticularly critical for low-density insulations that may be inhomogeneous. The second requirement is necessary inorder to provide adequate guarding for the testing of the specimen materials and thicknesses of concern.FIG. 1 Schematic of a Line-Heat-Source Guarded-Hot-Plate ApparatusC1043 1635.5.1 Me
48、ter Plate and Guard Plate DiameterDiametersUse Annex A1 to determine either the diameter of the guard platefor a given meter plate diameter, or the diameter of the meter plate for a given guard plate diameter. Specifically, determine thecombinations of diameters of the meter plate and guard plate th
49、at will be required so that the edge-heat-loss error will not beexcessive for the thickest specimens, with the highest lateral thermal conductances. If necessary, calculate the edge heat loss fordifferent edge insulation and secondary-guarding conditions.NOTE 4For example, when testing relatively thin specimens of insulation, it may be sufficient to maintain the ambient temperature at essentially themean temperature of the specimens and to use minimal edge insulation without secondary guarding. However, for thicker conductive specimens, edgeinsu
