1、Designation: C 1114 06Standard Test Method forSteady-State Thermal Transmission Properties by Means ofthe Thin-Heater Apparatus1This standard is issued under the fixed designation C 1114; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revis
2、ion, 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 test method covers the determination of the steady-state thermal transmission properties of fla
3、t-slab specimens ofthermal insulation using a thin heater of uniform power densityhaving low lateral heat flow. A thin heater with low lateralthermal conductance can reduce unwanted lateral heat flow andavoid the need for active-edge guarding.1.2 This primary test method of thermal-transmission mea-
4、surement describes a principle, rather than a particular appa-ratus. The principle involves determination of the thermal fluxacross a specimen of known thickness and the temperatures ofthe hot and cold faces of the specimen.1.3 Considerable latitude is given to the designer of theapparatus in this t
5、est method; since a variety of designs ispossible, a procedure for qualifying an apparatus is given in5.3.1.4 The specimens must meet the following conditions ifthermal resistance or thermal conductance of the specimen is tobe determined by this test method2:1.4.1 The portion of the specimen over th
6、e isothermal areaof the heater must accurately represent the whole specimen.1.4.2 The remainder of the specimen should not distort theheat flow in that part of the specimen defined in 1.4.1.1.4.3 The specimen shall be thermally homogeneous suchthat the thermal conductivity is not a function of the p
7、ositionwithin the sample, but rather may be a function of direction,time, and temperature. The specimen shall be free of holes, ofhigh-density volumes, and of thermal bridges between the testsurfaces or the specimen edges.1.4.4 Test Method C 177 describes tests that can helpascertain whether conditi
8、ons of 1.4 are satisfied. For thepurposes of this test method, differences in the measurementsof less than 2 % may be considered insignificant, and therequirements fulfilled.1.5 The specimens shall meet one of the following require-ments, in addition to those of 1.4.1.5.1 If homogeneous materials as
9、 defined in TerminologyC 168 are tested, then the thermal resistivity and thermalconductivity can be determined by this test method.1.5.2 If materials which are layered or otherwise thermallyinhomogeneous are tested, thermal resistance and thermalconductance can be determined by this test method.1.6
10、 Two versions of thin-heater apparatus using the sameprinciple of the standard are described inAnnexA1 andAnnexA2. They are similar in concept but differ in size andconstruction, and hence warrant separate descriptions for eachdesign. This test method in no way limits the size of thethin-heater elem
11、ent. One of the units described uses a thinmetal foil, while the other uses a metal screen as the heatsource. The smaller, foil apparatus is designed to make rapidmeasurements of heat transmission through specimens as thinas 0.5 cm and as thick as 2 cm; however, an apparatus using afoil heater could
12、 be designed to measure much thicker mate-rials, if desired. The larger, screen apparatus is designed tomeasure specimens with thicknesses between 3 and 15 cm,where the exact limits depend on the thermal resistance of thespecimens. Both apparatuses use thermocouples for measuringtemperature, but oth
13、er temperature-sensing systems can beused.1.7 This test method covers the theory and principles of themeasurement technique. It does not provide details of construc-tion other than those required to illustrate two devices whichmeet the prescribed requirements. Detailed information isavailable in Ref
14、erences (1-23)3and the Adjunct.1.8 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 and health practices and determine the applica-bility of regulatory limitatio
15、ns prior to use.1This test method is under the jurisdiction ofASTM Committee C16 on ThermalInsulation and is the direct responsibility of Subcommittee C16.30 on ThermalMeasurement.Current edition approved Nov. 1, 2006. Published December 2006. Originallyapproved 1989. Last previous edition approved
16、2006 as C 1114 00(2006).2Further discussion on the definition of these limitations may be found in Tye,R. P., “What Property Do We Measure?,” Heat Transmission Measurements inThermal Insulations, ASTM STP 544, ASTM, 1974, pp 512.3The boldface numbers in parentheses refer to the list of references at
17、 the end ofthis test method.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.2. Referenced Documents2.1 ASTM Standards:4C 168 Terminology Relating to Thermal InsulationC 177 Test Method for Steady-State Heat Flux Measure-ments and The
18、rmal Transmission Properties by Means ofthe Guarded-Hot-Plate ApparatusC 518 Test Method for Steady-State Thermal TransmissionProperties by Means of the Heat Flow Meter ApparatusC 687 Practice for Determination of Thermal Resistance ofLoose-Fill Building InsulationC 1043 Practice for Guarded-Hot-Pla
19、te Design Using Cir-cular Line-Heat SourcesC 1044 Practice for Using a Guarded-Hot-Plate Apparatusor Thin-Heater Apparatus in the Single-Sided ModeC 1045 Practice for Calculating Thermal TransmissionProperties Under Steady-State ConditionsC 1058 Practice for Selecting Temperatures for Evaluatingand
20、Reporting Thermal Properties of Thermal Insulation5E 177 Practice for Use of the Terms Precision and Bias inASTM Test Methods2.2 ASTM Adjuncts:Descriptions of Two Types of Thin-Heater Apparatus63. Terminology3.1 Applicable terms and symbols are defined in Terminol-ogy C 168. Any terms or symbols not
21、 included in C 168 butused in this test method will be defined within the text.4. Summary of Test Method4.1 Principles:4.1.1 A thin-foil or metal-screen heating apparatus operatesin accordance with the basic concept of a unidimensional,longitudinal heat-flow technique. The heater is made suffi-cient
22、ly thin so that lateral heat flow along the plane of theheater is insignificant, and so that there is no need for isolationand separate temperature control of a guard region, exceptpossibly the control of ambient temperature.4.1.2 The low mass of the thin heater apparatus minimizesdrift error and al
23、lows the apparatus to reach steady-state in asignificantly shorter time than a typical Test Method C 177apparatus.4.1.3 It should be noted that all quantities in this procedureare determined by direct measurement. There are no arbitraryfactors requiring calibration by comparison with a standard:thus
24、, the apparatus yields results on an absolute basis.4.1.4 A properly designed heater will be sufficiently thin toreduce lateral heat flow from the central zone to an acceptablysmall level. The result is that within a central zone, one-dimensional, longitudinal flow of heat perpendicular to theheater
25、 is obtained through the specimen. Because the foil orscreen heater is very thin, the need for a gap between the innerand outer heater regions to act respectively as hot-plate andguard, is unnecessary.5. Significance and Use5.1 Factors that may influence the thermal-transmissionproperties of a speci
26、men of material are described in PracticeC 1045 and the Precision and Bias section of Test MethodC 177.5.2 Because of the required test conditions prescribed bythis test method, it shall be recognized that the thermalproperties obtained will not necessarily apply without modifi-cation to all conditi
27、ons of service. As an example, this testmethod normally provides that the thermal properties shall beobtained on specimens that do not contain moisture, althoughin service such conditions may not be realized. Even morebasic is the dependence of the thermal properties on variablessuch as mean tempera
28、ture and temperature difference.5.3 When a new or modified design of apparatus is evolved,tests shall be made on at least two sets of differing material ofknown long-term thermal stability. Tests shall be made for eachmaterial at a minimum of two different mean temperatureswithin the operating range
29、 of each. Any differences in resultsshould be carefully studied to determine the cause and then beremoved by appropriate action. Only after a successful verifi-cation study on materials having known thermal propertiestraceable to a recognized national standards laboratory shalltest results obtained
30、with this apparatus be considered toconform with this test method. Periodic checks of apparatusperformance are recommended.5.4 The thermal transmission properties of many materialsdepend upon the prior thermal history. Care must be exercisedwhen testing such specimens at a number of conditions so th
31、attests are performed in a sequence that limits such effects on theresults.5.5 Typical uses for the thin-heater apparatus include thefollowing:5.5.1 Product development and quality control applications.5.5.2 Measurement of thermal conductivity at desired meantemperatures.5.5.3 Thermal properties of
32、specimens that are moist orclose to melting point or other critical temperature (see Note1).NOTE 1Apparatus of the type covered by this test method apply to thestudy of thermal properties of specimens containing moisture because ofthe use of small temperature differences and the low thermal capacity
33、 ofthe heat source.5.5.4 Determination of thermal properties of relatively highR value insulation samples with large apparatuses. In the caseof the metal-screen heater apparatus, samples with thicknessesup to 15 cm can be measured.6. Apparatus and Specimen Preparation6.1 The simplicity of this test
34、procedure may cause veryimportant factors to be overlooked which may affect theresults. To ensure accuracy of measurements, the user of thisapparatus should know how to measure temperature and power4For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service
35、at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.5Consult Test Methods C 177, C 518, and Practice C 1045 for the correctapplication of this test method.6Available from ASTM International Headquarters. Order Adjun
36、ct No.ADJC1114.C1114062as they relate to testing of thermal resistance. It is alsonecessary that the specimens be properly selected and preparedfor evaluation.6.2 Normally, test specimens are selected in pairs from thesample lot. The specimens selected should be uniform andhomogeneous to ensure that
37、 test apparatus symmetry is main-tained. Appropriate thermal modeling may allow tests ofnonuniform specimens, such as small specimens positionedwithin larger ones, or composite or layered specimens.6.3 Test specimens shall be prepared and conditioned inaccordance with the appropriate material specif
38、ication. Theconditioning of the test specimens shall be reported.6.3.1 The surfaces of the specimens shall be prepared toensure uniform thermal contact with the heater andtemperature-controlled plates. Further details may be found inthe Specimen Preparation section of Test Method C 177.6.3.2 When ev
39、aluating compressible specimens, providemeans to maintain a definite, known test thickness. Onemethod is to insert rigid equal-length spacers made of lowthermal-conductivity material in the corners of specimens. Analternative method involves using mechanical arrangements toestablish fixed and known
40、spacing and parallelism between theheater and cold plates.6.3.3 The maximum allowable distance between the heaterand cold plates (specimen thickness) is limited by the specimenthermal resistance, the ambient temperature, and the ratio ofmeasurement area to apparatus size. The isothermal areaestablis
41、hed in the center of the heater is influenced by thesefactors. The isothermal area must be large enough to establishthe equilibrium heat flux (W/m2) through a representative areaof the specimen. References are presented which will helpguide users in determining the maximum thickness that can beused
42、for specimens in their apparatus.6.4 The distance between the heater and the cold plates mustbe adjusted to confine the specimens with pressure sufficient toensure good thermal contact between the specimens and thebounding surfaces. For rigid specimens, a pressure of 2.5 kPais recommended. For compr
43、essible specimens, see 6.3.2.7. Procedure7.1 The testing procedure includes the following steps:7.1.1 Specimen selection,7.1.2 Specimen preparation and installation, and7.1.3 Test execution.7.2 Specimen SelectionOnly those specimen selectionfactors important to the performance of the apparatus areco
44、nsidered here. Those factors dictated by the objectivesrelated to obtaining derived thermal properties are described inPractice C 1045 and material specifications. For the two-sidedmode of operation, the two specimens should be selected to beas similar in thickness and thermal characteristics as pos
45、sible.7.2.1 SizeThe maximum specimen thickness that can bemeasured to a given accuracy is dependent on several param-eters, including the size of the apparatus, thermal resistance ofthe specimen, and the accuracy desired. To maintain edge heatlosses to below about 0.5 %, the recommended maximumthick
46、ness of the specimen is one third the minimum lineardimension of the metered region, if different from the thin-heater area. For more specific quantitative information on thislimitation see Refs. (24), (25), (26), and (27).7.2.1.1 The specimen may be sized to extend beyond themetered area by a dista
47、nce sufficient to ensure one-dimensionalheat flow within the metered area.7.2.2 Homogeneity There are two potential problems indetermining the heat flux through highly inhomogeneousspecimens. One is related to the interpretation and applicationof the resulting data; it is discussed in Practice C 104
48、5. Theother is connected with the degradation in performance of theapparatus. If the specimen itself is highly inhomogeneous, thatis, the heat flux density varies appreciably over the meteredarea, several errors can be significantly increased. The tem-perature distribution of the thin heater can dev
49、iate appreciablyfrom isothermal conditions which, in turn, can cause largeuncertainties in the average temperature difference across thespecimen. The increased temperature variations of the thinheater can also lead to increased edge heat losses. Theimportance of measuring temperatures of the thin heater orspecimen surface at numerous points is greatly increased undersuch conditions.7.3 Specimen Preparation and InstallationThe specimenshall be conditioned in accordance with the appropriate mate-rial specification. The following guidelines for specimenpreparation apply when the ma
