1、Designation: C 168 08aStandard Terminology Relating toThermal Insulation1This standard is issued under the fixed designation C 168; 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
2、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, andabbreviations of terms used in ASTM standards pertaining tothermal insulating materials, and to materi
3、als 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.2. Referenced Documents2.1 ASTM Standards:E 456 Terminology Relatin
4、g to Quality and StatisticsE 2282 Guide for Defining the Test Result of a Test Method2.2 ISO Standard:ISO 7345 Thermal InsulationPhysical Quantities andDefinitions23. Terminology3.1 Definitions:absorptance, nthe ratio of the radiant flux absorbed by abody to that incident upon it.absorption, ntransf
5、ormation of radiant energy to a differentform of energy by interaction with matter.apparent thermal conductivity, la, ka, na thermal con-ductivity assigned to a material that exhibits thermal trans-mission by several modes of heat transfer resulting inproperty variation with specimen thickness, or s
6、urface emit-tance. See conductivity, thermal.DISCUSSIONThermal conductivity and resistivity are normally con-sidered to be intrinsic or specific properties of materials and, as such,should be independent of thickness. When nonconductive modes ofheat transfer are present within the specimen (radiatio
7、n, 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.DISCUSSIONTest data using the “apparent” modifier must be quotedonly for the conditions of the measure
8、ment. 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 labeled with “apparent” shall not include anyequipment related measurement errors induced due t
9、o 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 resistivityassigned to a material that exhibits thermal transmission byseveral modes of heat tra
10、nsfer resulting in property variationwith specimen thickness, or surface emittance. See resistiv-ity, thermal.DISCUSSIONSee entire discussion under apparent thermal conduc-tivity.area weight, nweight per unit area for a specified sample, inunits of lb/ft2(kg/m2).aerogel, na homogeneous, low-density
11、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 path of air molecules at standardatmospheric pressure and temperature.batt, nblanket insul
12、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
13、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, n blanket insulation cov-ered by flexible metal-mesh facings attached on one or bothsides.block i
14、nsulation, nrigid insulation preformed into rectangu-lar units.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 Sept. 1, 2008. Published September 2008. Originallyappr
15、oved in 1941. Last previous edition approved in 2008 as C 168 08.2Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United
16、States.board insulation, nsemirigid insulation preformed intorectangular units having a degree of suppleness particularlyrelated to their geometrical dimensions.calcium silicate, ninsulation composed principally of hy-drous calcium silicate, and which usually contains reinforc-ing fibers.cellular el
17、astomeric, 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 processed toform a rigid foam having a predominantly closed-cells
18、tructure.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 principally ofpolymerized styrene resin processed to form a rigi
19、d 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 foam having a predominantly closed-cellstructure.cellulosic
20、 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 develops aplastic consistency, and when dried in place for
21、ms 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 affords substantial resistanceto heat transmission.closed cell
22、 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 application to thermal insula-tion or other surfaces in thickness of 30 mils (0.76 mm) orless, per coat.conductance
23、, 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 environment is a fluid (liquids or gases). h dependson the nature of fluid motion past the surface (laminar or turbulen
24、t). (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 between the body surfaces.C 5 q/DTA conductance (C) associated with a material shall bespecified as a material C. A con
25、ductance ( C) associated with asystem 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.)DISCUSSIONThe average temperature of a surface is the area-weighted temperature of that surface.DISCUSSIONWhen the surfaces of
26、 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 thickness to which the conductance is assigned must be defined.DISCUSSION“Total or “areal thermal conductance are of
27、ten usedas synonyms for thermal conductance.DISCUSSIONThermal conductance and thermal resistance are recip-rocals of one another.DISCUSSIONSee Discussion under resistance, thermal.conductivity, thermal, l or k, nthe time rate of steady stateheat flow through a unit area of a homogeneous materialindu
28、ced by a unit temperature gradient in a directionperpendicular to that unit area. (l or k in SI units: (W/m2)/(K/m) = W/m K.) (l or k in inch-pound units: (Btu/h)/ft2/(F/ft) = Btu/h ft F) or (Btu/h)/ft2/(F/in.) = Btu in./h ft2F.)(See discussion under apparent thermal conductivity.)DISCUSSIONThermal
29、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. Theoperational definitions of thermal conductivity for these two cases aregiven as follows:Flat2slab geometry l5QAL
30、DT(1)where:Q = heat flow rate,A = area through which Q passes, andL = thickness of the flat-slab specimen across which thetemperature difference DT exists.The DT/L ratio approximates the temperature gradient.Cylindrical geometry l5Q2plDTloger2r1(2)where:1 = length,r2= the outer radius, andr1= the in
31、ner radius of the cylinder.Eq 1 and Eq 2 are actually special-case simplifications of themore general definition:thermal conductivity, la tensor property defined by thetensor equation:q 5 2lDT (3)where q is the heat flux vector, and D T (grad T)isthetemperature gradient vector. Except in theoretical
32、 discussions,this generalized form of the definition is seldom used. ForC 168 08a2experimental situations, the geometry of the testing apparatusand the specimen are chosen such that Eq 3 reduces to theone-dimensional scalar equation:Q 52AldTdu(4)where:Q = heat flow rate,A = area through which Q pass
33、es,l = 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 D Tis sufficiently small. If DT is not sufficiently small, then Eq 1and Eq 2 define a mean thermal conductivity over the DTrange, and this range in
34、 addition to the mean temperatureshould be stated.DISCUSSIONIf the measured thermal property indicates that otherthan conductive heat flows are present, as evidenced by dependence onspecimen thickness, air flow, or emittance of bounding surfaces, thenthis definition does not apply. See also, apparen
35、t thermal conductiv-ity.DISCUSSIONThermal conductivity and thermal resistivity are recip-rocals of one another.DISCUSSIONAs an additional reference and discussion along similarlines, see the International Standard ISO 7345 Annex.coverage, nthe area to be covered per unit volume of coatingto obtain s
36、pecified dry thickness and desired performance.covering capacity, dry, nthe area covered 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 thicknes
37、sof 1 in. (25 mm) by 100 lb (45.4 kg) of dry cement whenmixed with the recommended amount of water, and molded.density,r, nthe mass per unit volume of a material. (r in SIunits: kg/m3.) (r in inch-pound units: lb/ft3.)DISCUSSIONThe term mass is used and not weight, due to thebuoyancy effect of some
38、low density closed cell insulations.density, apparent (of applied insulation), nthe mass 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 temperatur
39、e is reduced;the temperature corresponding to saturation (100 % relativehumidity) for a given absolute humidity at constant pressure.diatomaceous silica, ninsulation composed principally ofdiatomaceous earth with or without binders, and whichusually contains reinforcing fibers.diffusivity, thermal,
40、nthe ratio of thermal conductivity of asubstance to the product of its density and specific 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 black
41、body at the sametemperature and under the same conditions.emittance, directional (u; f), nthe 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 (2p), nthe average direc-tional em
42、ittance over a hemispherical envelope covering asurface.emittance, spectral lor (l; u;f ), nan emittance basedon the radiant energy emitted per unit wavelength interval(monochromatic radiant energy).DISCUSSIONWhere necessary to avoid confusion, emittances shouldbe designated by subscripts, for examp
43、le: HT,Hl, Nl, ul,HT. Formost engineering purposes, the hemispherical total emittance HTsuffices.emittance, total Tor (t), nan emittance that is anintegrated average over all wavelengths of radiant energyemitted.facing, na protective or decorative (or both) surface appliedas the outermost layers of
44、an insulation system.fibrous glass, nA synthetic vitreous fiber insulation made bymelting predominantly silica sand and other inorganic ma-terials, and then physically forming the melt into fibers.DISCUSSIONCommonly referred to as fiber glass.DISCUSSIONTo form an insulation product, there are often
45、othermaterials applied to the fibrous glass such as binders, oils, etc.graybody, na body having the same spectral emittance at allwavelengths.glass fiber, nfiber manufactured as continuous filament frommolten glass, normally used for reinforcement, tissue ortextiles.glass wool, nSee fibrous glass.he
46、at flow; heat flow rate, Q, nthe quantity of heat trans-ferred to or from a system in unit time. (Q in SI units: W.) (Qin inch-pound units: Btu/h.)DISCUSSIONSee heat flux for the areal dependence.DISCUSSIONThis definition is different than that given in sometextbooks, which may use Q,orq to represen
47、t heat flow rate. The ISOdefinition uses F.heat flux, q, nthe heat flow rate through a surface of unitarea perpendicular to the direction of heat flow.(q in SI units: W/m2)(q in inch-pound units: Btu/h/ft2= Btu/h ft2)DISCUSSIONThis definition has been used as heat flux density, ordensity of heat flo
48、w rate (defined as areal density of heat flow rate byISO).heat flux transducer, HFT, na device containing a thermo-pile (or equivalent) that produces an output which is afunction of the heat flux.DISCUSSIONIn the past this device may also have been known as aheat flow meter, heat flux meter, heat fl
49、ow sensor, or heat flux sensor.DISCUSSIONThe HFT output may also be a function of meantemperature, attachment, application, and environmental situation.homogeneous material, na material in which relevantproperties are not a function of the position within thematerial.C 168 08a3DISCUSSIONHomogeneity depends on the scale of the volumeelement used to examine the material. The purposes of Committee C16are best suited if a macroscopic viewpoint is taken such that thestandard insu
