1、Designation: C168 17Standard Terminology Relating toThermal Insulation1This standard is issued under the fixed designation C168; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses ind
2、icates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This standard provides definitions, symbols, units, andabbreviations of terms used in ASTM standards pertaining tothermal insulating materials, and to materials
3、 associated withthem.1.2 This terminology is not intended to be used to classifyinsulation materials as having particular properties. Rather,classification of insulation materials is to be done by thematerial standards themselves.1.3 This standard does not purport to address all of thesafety concern
4、s, 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.1.4 This international standard was developed in accor-dance with internationally rec
5、ognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D3574 Test Methods
6、for Flexible Cellular MaterialsSlab,Bonded, and Molded Urethane FoamsE456 Terminology Relating to Quality and StatisticsE2282 Guide for Defining the Test Result of a Test Method2.2 ISO Standard:ISO 7345 Thermal InsulationPhysical Quantities andDefinitions33. Terminology3.1 Definitions:absorptance, n
7、the ratio of the radiant flux absorbed by abody to that incident upon it.absorption, ntransformation of radiant energy to a differentform of energy by interaction with matter.apparent thermal conductivity, a, ka, na thermal conduc-tivity assigned to a material that exhibits thermal transmis-sion by
8、several modes of heat transfer resulting in propertyvariation with specimen thickness, or surface emittance. Seeconductivity, thermal.DISCUSSIONThermal conductivity and resistivity are normally con-sidered to be intrinsic or specific properties of materials and, as such,should be independent of thic
9、kness. When nonconductive modes ofheat transfer are present within the specimen (radiation, free convec-tion) this may not be the case. To indicate the possible presence of thisphenomena (for example, thickness effect) the modifier “apparent” isused, as in apparent thermal conductivity.DISCUSSIONTes
10、t data using the “apparent” modifier must be quotedonly for the conditions of the measurement. Values of thermal conduc-tance (material C) and thermal resistance (material R) calculated fromapparent thermal conductivity or resistivity, are valid only for the sameconditions.DISCUSSIONTest data labele
11、d with “apparent” shall not include anyequipment related measurement errors induced due to measurementattempts beyond an apparatus range or calibration.DISCUSSIONUse of the “apparent” modifier with system C or systemR measurements is not permitted.apparent thermal resistivity, ra, na thermal resisti
12、vityassigned to a material that exhibits thermal transmission byseveral modes of heat transfer resulting in property variationwith specimen thickness, or surface emittance. Seeresistivity, thermal.DISCUSSIONSee entire discussion under apparent thermal conduc-tivity.area weight, nweight per unit area
13、 for a specified sample, inunits of lb/ft2(kg/m2).aerogel, na homogeneous, low-density solid phase materialderived from a gel, in which the liquid component of the gelhas been replaced with a gas.DISCUSSIONThe resulting material has a porous structure with anaverage pore size below the mean free pat
14、h of air molecules at standardatmospheric pressure and temperature.1This terminology is under the jurisdiction of ASTM Committee C16 onThermal Insulation and is the direct responsibility of Subcommittee C16.94 onTerminology.Current edition approved June 1, 2017. Published June 2017. Originallyapprov
15、ed in 1941. Last previous edition approved in 2015 as C168 15a.DOI:101520/C0168-17.2For 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 pa
16、ge onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was develo
17、ped in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1batt, nblanket insul
18、ation manufactured to dimensions asrequired by a specific application.blackbody, nthe ideal, perfect emitter and absorber ofthermal radiation. It emits radiant energy at each wavelengthat the maximum rate possible as a consequence of itstemperature, and absorbs all incident radiance.blanket, nflexib
19、le insulation product, supplied rolled or flat.blanket insulation, na relatively flat and flexible insulationin coherent sheet form furnished in units of substantial area.blanket insulation, metal mesh, nblanket insulation cov-ered by flexible metal-mesh facings attached on one or bothsides.block in
20、sulation, nrigid insulation preformed into rectangu-lar units.board insulation, nsemirigid insulation preformed into rect-angular units having a degree of suppleness particularlyrelated to their geometrical dimensions.calcium silicate, ninsulation composed principally of hy-drous calcium silicate, a
21、nd which usually contains reinforc-ing fibers.cellular elastomeric, ninsulation composed principally ofnatural or synthetic elastomers, or both, processed to form aflexible, semirigid, or rigid foam which has a predominantlyclosed-cell structure.cellular glass, ninsulation composed of glass processe
22、d toform a rigid foam having a predominantly closed-cellstructure.cellular polyimide, ninsulation composed of the reactionproduct in which the bonds formed between monomersduring polymerization are essentially imide units forming acellular structure.cellular polystyrene, ninsulation composed princip
23、ally ofpolymerized styrene resin processed to form a rigid foamhaving a predominantly closed-cell structure.cellular polyurethane, ninsulation composed principally ofthe catalyzed reaction product of polyisocyanate and poly-hydroxy compounds, processed usually with fluorocarbongas to form a rigid fo
24、am having a predominantly closed-cellstructure.cellulosic fiber, ninsulation composed principally of cellu-lose fibers usually derived from paper, paperboard stock, orwood, with or without binders.cement, finishing, na mixture of dry fibrous or powderymaterials, or both, that when mixed with water d
25、evelops aplastic consistency, and when dried in place forms a rela-tively hard, protective surface.cement, insulating, na mixture of dry granular, flaky,fibrous, or powdery materials that when mixed with waterdevelops a plastic consistency, and when dried in placeforms a coherent covering that affor
26、ds substantial resistanceto heat transmission.cladding, nSee jacket (as related to insulation jacketing).closed cell foam, na material comprised predominantly ofindividual non-interconnecting cellular voids.coating, na liquid or semiliquid that dries or cures to form aprotective finish, suitable for
27、 application to thermal insula-tion or other surfaces in thickness of 30 mils (0.76 mm) orless, per coat.conductance, film, nthe time rate of heat flow from a unitarea of a surface to its surroundings, induced by a unittemperature difference between the surface and the environ-ment.DISCUSSIONThe env
28、ironment is a fluid (liquids or gases). h dependson the nature of fluid motion past the surface (laminar or turbulent). (hin SI units: W/m2K).conductance, thermal, C, nthe time rate of steady state heatflow through a unit area of a material or construction inducedby a unit temperature difference bet
29、ween the body surfaces.C 5 q/TA conductance (C) associated with a material shall bespecified as a material C. A conductance (C) associated witha system or construction of materials shall be specified as asystem C.(C in SI units: W/m2K.) (C in inch-pound units:(Btu/h)/ft2/F = Btu h ft2F.)DISCUSSIONTh
30、e average temperature of a surface is the area-weighted temperature of that surface.DISCUSSIONWhen the surfaces of a mass type thermal insulation arenot of equal areas, as in the case of thermal transmission in the radialdirection, or are not of uniform separation (thickness), the surface areaand th
31、ickness to which the conductance is assigned must be defined.DISCUSSION“Total” or “areal” thermal conductance are often usedas synonyms for thermal conductance.DISCUSSIONThermal conductance and thermal resistance are recip-rocals of one another.DISCUSSIONSee Discussion under resistance, thermal.cond
32、uctivity, thermal, or k, nthe time rate of steady stateheat flow through a unit area of a homogeneous materialinduced by a unit temperature gradient in a directionperpendicular to that unit area. ( or k in SI units: (W/m2)/(K/m) = W m K.) ( or k in inch-pound units: (Btu/h)/ft2/(F/ft) = Btu h ft F)
33、or (Btu/h)/ft2/(F/in.) = Btu in./h ft2F.) (Seediscussion under apparent thermal conductivity.)DISCUSSIONThermal conductivity testing is usually done in one oftwo apparatus/specimen geometries: flat-slab specimens with parallelheat flux lines, or cylindrical specimens with radial heat flux lines. The
34、operational definitions of thermal conductivity for these two cases aregiven as follows:Flat 2 slab geometry 5QALT(1)where:Q = heat flow rate,A = area through which Q passes, andL = thickness of the flat-slab specimen across which thetemperature difference T exists.The T/L ratio approximates the tem
35、perature gradient.C168 172Cylindrical geometry 5Q2lTloger2r1(2)where:1 = length,r2= the outer radius, andr1= the inner radius of the cylinder.Eq 1 and Eq 2 are actually special-case simplifications of the more generaldefinition:thermal conductivity, a tensor property defined by the tensor equation:q
36、 52T (3)where q is the heat flux vector, and T (grad T) is the temperature gra-dient vector. Except in theoretical discussions, this generalized form ofthe definition is seldom used. For experimental situations, the geometryof the testing apparatus and the specimen are chosen such that Eq 3reduces t
37、o the one-dimensional scalar equation:Q 52AdTdu(4)where:Q = heat flow rate,A = area through which Q passes, = thermal conductivity, anddT/du = the temperature gradient in the direction of heatflow.At steady state, Eq 1 and Eq 2 are consistent with Eq 4 if T is sufficientlysmall. If T is not sufficie
38、ntly small, then Eq 1 and Eq 2 define a meanthermal conductivity over the T range, and this range in addition to themean temperature should be stated.DISCUSSIONIf the measured thermal property indicates that otherthan conductive heat flows are present, as evidenced by dependence onspecimen thickness
39、, air flow, or emittance of bounding surfaces, thenthis definition does not apply. See also, apparent thermal conductiv-ity.DISCUSSIONThermal conductivity and thermal resistivity are recip-rocals of one another.DISCUSSIONAs an additional reference and discussion along similarlines, see the Internati
40、onal Standard ISO 7345 Annex.corrosion retarder (as related to insulation jacketing), nSeemoisture barrier (as related to insulation jacketing).coverage, nthe area to be covered per unit volume of coatingto obtain specified dry thickness and desired performance.covering capacity, dry, nthe area cove
41、red to a dry thicknessof 1 in. (25 mm) by 100 lb (45.4 kg) of dry cement whenmixed with the recommended amount of water, molded anddried to constant weight.covering capacity, wet, nthe area covered to a wet thicknessof 1 in. (25 mm) by 100 lb (45.4 kg) of dry cement whenmixed with the recommended am
42、ount of water, and molded.density, nthe mass per unit volume of a material. ( in SIunits: kg/m3.) ( in inch-pound units: lb/ft3.)DISCUSSIONThe term mass is used and not weight, due to thebuoyancy effect of some low density closed cell insulations.density, apparent (of applied insulation), nthe mass
43、perunit volume of in-place mass thermal insulation.dewpoint temperature, nthe temperature at which conden-sation of water vapor in a space begins for a given state ofhumidity and pressure as the vapor temperature is reduced;the temperature corresponding to saturation (100 % relativehumidity) for a g
44、iven absolute humidity at constant pressure.diatomaceous silica, ninsulation composed principally ofdiatomaceous earth with or without binders, and whichusually contains reinforcing fibers.diffusivity, thermal, nthe ratio of thermal conductivity of asubstance to the product of its density and specif
45、ic heat. (InSI units: (W/(mK)/(kg/m3)(J/(kgK) = m2/s.) (In inch-pound units: (Btu/(hrft) F)/(lb/ft3)(Btu/(lbF) = ft2/hr.)emittance, , nthe ratio of the radiant flux emitted by aspecimen to that emitted by a blackbody at the sametemperature and under the same conditions.emittance, directional (; ), n
46、the ratio of the radiancefrom a surface in a particular direction to the radiance froma blackbody at the same temperature under the sameconditions.emittance, hemispherical Hor (2), nthe average direc-tional emittance over a hemispherical envelope covering asurface.emittance, spectral or (; ; ), nan
47、emittance based onthe radiant energy emitted per unit wavelength interval(monochromatic radiant energy).DISCUSSIONWhere necessary to avoid confusion, emittances shouldbe designated by subscripts, for example: HT, H, N, , HT. Formost engineering purposes, the hemispherical total emittance HTsuffices.
48、emittance, total Tor (t), nan emittance that is anintegrated average over all wavelengths of radiant energyemitted.facing, na thin covering adhered to the surface of insulationprior to field installation.fibrous glass, nA synthetic vitreous fiber insulation made bymelting predominantly silica sand a
49、nd other inorganicmaterials, and then physically forming the melt into fibers.DISCUSSIONCommonly referred to as fiber glass.DISCUSSIONTo form an insulation product, there are often othermaterials applied to the fibrous glass such as binders, oils, etc.flexible cellular material, na cellular material that will notrupture within a specified time when bent around a mandrelat a specified uniform temperature and rate.DISCUSSIONTest Methods D3
