1、Designation: C168 13C168 15Standard 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 parenthe
2、ses indicates 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, and abbreviations of terms used inASTM standards pertaining to thermalinsulating materials, and to ma
3、terials associated with them.1.2 This terminology is not intended to be used to classify insulation materials as having particular properties. Rather,classification of insulation materials is to be done by the material standards themselves.1.3 This standard does not purport to address all of the saf
4、ety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D3574 Test Methods for Flexible Ce
5、llular 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 and Definitions33. Terminology3.1 Definitions:absorptance, nthe ratio of
6、the radiant flux absorbed by a body to that incident upon it.absorption, ntransformation of radiant energy to a different form of energy by interaction with matter.apparent thermal conductivity, a,ka,na thermal conductivity assigned to a material that exhibits thermal transmission byseveral modes of
7、 heat transfer resulting in property variation with specimen thickness, or surface emittance. See conductivity,thermal.DISCUSSIONThermal conductivity and resistivity are normally considered to be intrinsic or specific properties of materials and, as such, should be independent ofthickness. When nonc
8、onductive modes of heat transfer are present within the specimen (radiation, free convection) this may not be the case. To indicatethe possible presence of this phenomena (for example, thickness effect) the modifier “apparent” is used, as in apparent thermal conductivity.DISCUSSIONTest data using th
9、e “apparent” modifier must be quoted only for the conditions of the measurement. Values of thermal conductance (material C) andthermal resistance (material R) calculated from apparent thermal conductivity or resistivity, are valid only for the same conditions.DISCUSSION1 This terminology is under th
10、e jurisdiction of ASTM Committee C16 on Thermal Insulation and is the direct responsibility of Subcommittee C16.94 on Terminology.Current edition approved April 1, 2013June 1, 2015. Published May 2013July 2015. Originally approved in 1941. Last previous edition approved in 20102013 asC 168 10.C168 1
11、3. DOI:101520/C016813.DOI:101520/C016815.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 Available from Ame
12、rican National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http:/www.ansi.org.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be t
13、echnically 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 be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive,
14、PO Box C700, West Conshohocken, PA 19428-2959. United States1Test data labeled with “apparent” shall not include any equipment related measurement errors induced due to measurement attempts beyond anapparatus range or calibration.DISCUSSIONUse of the “apparent” modifier with system C or system R mea
15、surements is not permitted.apparent thermal resistivity, ra,na thermal resistivity assigned to a material that exhibits thermal transmission by several modesof heat transfer resulting in property variation with specimen thickness, or surface emittance. See resistivity, thermal.DISCUSSIONSee entire d
16、iscussion under apparent thermal conductivity.area weight, nweight per unit area for a specified sample, in units of lb/ft2 (kg/m2 ).aerogel, na homogeneous, low-density solid phase material derived from a gel, in which the liquid component of the gel hasbeen replaced with a gas.DISCUSSIONThe result
17、ing material has a porous structure with an average pore size below the mean free path of air molecules at standard atmospheric pressureand temperature.batt, nblanket insulation manufactured to dimensions as required by a specific application.blackbody, nthe ideal, perfect emitter and absorber of th
18、ermal radiation. It emits radiant energy at each wavelength at themaximum rate possible as a consequence of its temperature, and absorbs all incident radiance.blanket, nflexible insulation product, supplied rolled or flat.blanket insulation, na relatively flat and flexible insulation in coherent she
19、et form furnished in units of substantial area.blanket insulation, metal mesh, n blanket insulation covered by flexible metal-mesh facings attached on one or both sides.block insulation, nrigid insulation preformed into rectangular units.board insulation, nsemirigid insulation preformed into rectang
20、ular units having a degree of suppleness particularly related totheir geometrical dimensions.calcium silicate, ninsulation composed principally of hydrous calcium silicate, and which usually contains reinforcing fibers.cellular elastomeric, ninsulation composed principally of natural or synthetic el
21、astomers, or both, processed to form a flexible,semirigid, or rigid foam which has a predominantly closed-cell structure.cellular glass, ninsulation composed of glass processed to form a rigid foam having a predominantly closed-cell structure.cellular polyimide, ninsulation composed of the reaction
22、product in which the bonds formed between monomers duringpolymerization are essentially imide units forming a cellular structure.cellular polystyrene, ninsulation composed principally of polymerized styrene resin processed to form a rigid foam having apredominantly closed-cell structure.cellular pol
23、yurethane, ninsulation composed principally of the catalyzed reaction product of polyisocyanate and polyhydroxycompounds, processed usually with fluorocarbon gas to form a rigid foam having a predominantly closed-cell structure.cellulosic fiber, ninsulation composed principally of cellulose fibers u
24、sually derived from paper, paperboard stock, or wood, withor without binders.cement, finishing, na mixture of dry fibrous or powdery materials, or both, that when mixed with water develops a plasticconsistency, and when dried in place forms a relatively hard, protective surface.cement, insulating, n
25、a mixture of dry granular, flaky, fibrous, or powdery materials that when mixed with water develops aplastic consistency, and when dried in place forms a coherent covering that affords substantial resistance to heat transmission.cladding,nSee jacket(as related to insulation jacketing).closed cell fo
26、am, na material comprised predominantly of individual non-interconnecting cellular voids.C168 152coating, na liquid or semiliquid that dries or cures to form a protective finish, suitable for application to thermal insulation orother surfaces in thickness of 30 mils (0.76 mm) or less, per coat.condu
27、ctance, film, nthe time rate of heat flow from a unit area of a surface to its surroundings, induced by a unit temperaturedifference between the surface and the environment.DISCUSSIONThe environment is a fluid (liquids or gases). h depends on the nature of fluid motion past the surface (laminar or t
28、urbulent). (h in SI units: W/m2K).conductance, thermal, C,nthe time rate of steady state heat flow through a unit area of a material or construction induced bya unit temperature difference between the body surfaces.C5q/TA conductance (C) associated with a material shall be specified as a material C.
29、 A conductance (C) associated with a systemor construction of materials shall be specified as a system C. (C in SI units: W/m2K.) (C in inch-pound units: (Btu/h)/ft2/F = Btuh ft2F.)DISCUSSIONThe average temperature of a surface is the area-weighted temperature of that surface.DISCUSSIONWhen the surf
30、aces of a mass type thermal insulation are not of equal areas, as in the case of thermal transmission in the radial direction, or are notof uniform separation (thickness), the surface area and thickness to which the conductance is assigned must be defined.DISCUSSION“Total or “areal thermal conductan
31、ce are often used as synonyms for thermal conductance.DISCUSSIONThermal conductance and thermal resistance are reciprocals of one another.DISCUSSIONSee Discussion under resistance, thermal.conductivity, thermal, ork,nthe time rate of steady state heat flow through a unit area of a homogeneous materi
32、al induced bya unit temperature gradient in a direction perpendicular to that unit area. ( or k in SI units: (W/m2 )/(K/m) = Wm K.) ( ork in inch-pound units: (Btu/h)/ft 2/(F/ft) = Btuh ft F) or (Btu/h)/ft2/(F/in.) = Btu in./h ft2 F.) (See discussion under apparentthermal conductivity.)DISCUSSIONThe
33、rmal conductivity testing is usually done in one of two apparatus/specimen geometries: flat-slab specimens with parallel heat flux lines, orcylindrical specimens with radial heat flux lines. The operational definitions of thermal conductivity for these two cases are given as follows:Flat2slab geomet
34、ry 5QA LT (1)where:Q = heat flow rate,A = area through which Q passes, andL = thickness of the flat-slab specimen across which the temperature difference T exists.The T/L ratio approximates the temperature gradient.Cylindrical geometry 5 Q2pilT loge r2r1(2)C168 153where:1 = length,r2 = the outer rad
35、ius, andr1 = the inner radius of the cylinder.Eq 1 and Eq 2 are actually special-case simplifications of the more general definition:thermal conductivity, a tensor property defined by the tensor equation:q52T (3)where q is the heat flux vector, and T (grad T) is the temperature gradient vector. Exce
36、pt in theoretical discussions, this generalized form of thedefinition is seldom used. For experimental situations, the geometry of the testing apparatus and the specimen are chosen such that Eq 3 reduces tothe one-dimensional scalar equation:Q52A dTdu (4)where:Q = heat flow rate,A = area through whi
37、ch Q passes, = thermal conductivity, anddT/du = the temperature gradient in the direction of heat flow.At steady state, Eq 1 and Eq 2 are consistent with Eq 4 if T is sufficiently small. If T is not sufficiently small, then Eq 1 and Eq 2 define a mean thermalconductivity over the T range, and this r
38、ange in addition to the mean temperature should be stated.DISCUSSIONIf the measured thermal property indicates that other than conductive heat flows are present, as evidenced by dependence on specimen thickness, airflow, or emittance of bounding surfaces, then this definition does not apply. See als
39、o, apparent thermal conductivity.DISCUSSIONThermal conductivity and thermal resistivity are reciprocals of one another.DISCUSSIONAs an additional reference and discussion along similar lines, see the International Standard ISO 7345 Annex.corrosion retarder (as related to insulation jacketing),nSee m
40、oisture barrier (as related to insulation jacketing).coverage, nthe area to be covered per unit volume of coating to obtain specified dry thickness and desired performance.covering capacity, dry, nthe area covered to a dry thickness of 1 in. (25 mm) by 100 lb (45.4 kg) of dry cement when mixedwith t
41、he recommended amount of water, molded and dried to constant weight.covering capacity, wet, nthe area covered to a wet thickness of 1 in. (25 mm) by 100 lb (45.4 kg) of dry cement when mixedwith the recommended amount of water, and molded.density, nthe mass per unit volume of a material. ( in SI uni
42、ts: kg/m3.) ( in inch-pound units: lb/ft3.)DISCUSSIONThe term mass is used and not weight, due to the buoyancy effect of some low density closed cell insulations.density, apparent (of applied insulation), nthe mass per unit volume of in-place mass thermal insulation.dewpoint temperature, nthe temper
43、ature at which condensation of water vapor in a space begins for a given state of humidityand pressure as the vapor temperature is reduced; the temperature corresponding to saturation (100 % relative humidity) for agiven absolute humidity at constant pressure.diatomaceous silica, ninsulation compose
44、d principally of diatomaceous earth with or without binders, and which usuallycontains reinforcing fibers.diffusivity, thermal, nthe ratio of thermal conductivity of a substance to the product of its density and specific heat. (In SI units:(W/(mK)/(kg/m3)(J/(kgK) = m 2/s.) (In inch-pound units: (Btu
45、/(hrft) F)/(lb/ft3)(Btu/(lbF) = ft 2/hr)emittance, , nthe ratio of the radiant flux emitted by a specimen to that emitted by a blackbody at the same temperature andunder the same conditions.C168 154emittance, directional (; ), nthe ratio of the radiance from a surface in a particular direction to th
46、e radiance from a blackbodyat the same temperature under the same conditions.emittance, hemispherical H or (2pi) , nthe average directional emittance over a hemispherical envelope covering a surface.emittance, spectral or (; ; ), nan emittance based on the radiant energy emitted per unit wavelength
47、interval(monochromatic radiant energy).DISCUSSIONWhere necessary to avoid confusion, emittances should be designated by subscripts, for example: HT,H , N, ,HT . For most engineeringpurposes, the hemispherical total emittance HT suffices.emittance, total T or (t), nan emittance that is an integrated
48、average over all wavelengths of radiant energy emitted.facing, na thin covering adhered to the surface of insulation prior to field installation.fibrous glass, nA synthetic vitreous fiber insulation made by melting predominantly silica sand and other inorganic materials,and then physically forming t
49、he melt into fibers.DISCUSSIONCommonly referred to as fiber glass.DISCUSSIONTo form an insulation product, there are often other materials applied to the fibrous glass such as binders, oils, etc.flexible cellular material, na cellular material that will not rupture within a specified time when bent around a mandrel at aspecified uniform temperature and rate.DISCUSSIONTest Methods D3574 “Standard Test Methods for Flexible Cellular Ma
