1、Designation: C168 10C168 13Standard 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:2E456 Terminology Relating to Quali
5、ty 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 the radiant flux absorbed by a body to that incident upon it.absorption, ntransformation
6、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 heat transfer resulting in property variation with specimen thickness, or surface emitta
7、nce. 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 nonconductive modes of heat transfer are present within the specimen (radiation, free convect
8、ion) 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 the “apparent” modifier must be quoted only for the conditions of the measurement. Values o
9、f 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 the jurisdiction of ASTM Committee C16 on Thermal Insulation and is the direct responsibili
10、ty of Subcommittee C16.94 on Terminology.Current edition approved Jan. 1, 2010April 1, 2013. Published February 2010May 2013. Originally approved in 1941. Last previous edition approved in 20082010 asC 168 08a. DOI:101520/C016810.C 168 10. DOI:101520/C016813.2 For referencedASTM standards, visit the
11、ASTM 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 American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY
12、 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 technically possible to adequately depict all changes accurately, ASTM recommends t
13、hat 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, PO Box C700, West Conshohocken, PA 19428-2959. United States1Test data labeled wit
14、h “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 measurements is not permitted.apparent thermal resistivity, ra,na thermal resistivity
15、 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 discussion under apparent thermal conductivity.area weight, nweight per unit area f
16、or 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 resulting material has a porous structure with an average pore size below the mean free
17、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 thermal radiation. It emits radiant energy at each wavelength at themaximum rate pos
18、sible 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 sheet form furnished in units of substantial area.blanket insulation, metal mesh, n b
19、lanket 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 rectangular units having a degree of suppleness particularly related totheir geometrical
20、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 elastomers, or both, processed to form a flexible,semirigid, or rigid foam which has
21、 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 product in which the bonds formed between monomers duringpolymerization are essent
22、ially 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 polyurethane, ninsulation composed principally of the catalyzed reaction product of p
23、olyisocyanate 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 usually derived from paper, paperboard stock, or wood, withor without binders.cemen
24、t, 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, na mixture of dry granular, flaky, fibrous, or powdery materials that when mixed wi
25、th water develops aplastic consistency, and when dried in place forms a coherent covering that affords substantial resistance to heat transmission.cladding,nSee jacket.jacket(as related to insulation jacketing).closed cell foam, na material comprised predominantly of individual non-interconnecting c
26、ellular voids.C168 132coating, 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.conductance, film, nthe time rate of heat flow from a unit area of a surface to
27、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 turbulent). (h in SI units: W/m2K).conductance, thermal, C,nthe time rate of
28、 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. A conductance (C) associated with a systemor construction of materials sha
29、ll be specified as a system 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 a mass type thermal insulation are not of equal areas, as in the c
30、ase 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 conductance are often used as synonyms for thermal conductance.DISCUSSIONThermal co
31、nductance 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 material induced bya unit temperature gradient in a direction perpendicular to t
32、hat unit area. ( or k in SI units: (W/m2 )/(K/m) = W/m K.) ( or kin inch-pound units: (Btu/h)/ft 2/(F/ft) = Btu/h ft F) or (Btu/h)/ft2/(F/in.) = Btu in./h ft2 F.) (See discussion under apparentthermal conductivity.)DISCUSSIONThermal conductivity testing is usually done in one of two apparatus/specim
33、en 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 geometry 5QA LT (1)where:Q = heat flow rate,A = area through which Q passes, a
34、ndL = 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 133where:1 = length,r2 = the outer radius, andr1 = the inner radius of the cylinder.Eq 1 and Eq 2 are actually
35、 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. Except in theoretical discussions, this generalized form of thedefinition is
36、 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 which Q passes, = thermal conductivity, anddT/du = the temperature gradient
37、 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 range in addition to the mean temperature should be stated.DISCUSSIONIf t
38、he 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 also, apparent thermal conductivity.DISCUSSIONThermal conductivity and ther
39、mal 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 moisture barrier (as related to insulation jacketing).coverage, nthe area
40、 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 the recommended amount of water, molded and dried to constant weight.cove
41、ring 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 units: kg/m3.) ( in inch-pound units: lb/ft3.)DISCUSSIONThe term mass is us
42、ed 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 temperature at which condensation of water vapor in a space begins for a given
43、 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 composed principally of diatomaceous earth with or without binders, and which u
44、suallycontains 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/(hrft) F)/(lb/ft3)(Btu/(lbF) = ft 2/hr)emittance, , nthe ratio of the r
45、adiant flux emitted by a specimen to that emitted by a blackbody at the same temperature andunder the same conditions.C168 134emittance, directional (; ), nthe ratio of the radiance from a surface in a particular direction to the radiance from a blackbodyat the same temperature under the same condit
46、ions.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 interval(monochromatic radiant energy).DISCUSSIONWhere necessary to avoi
47、d confusion, emittances should be designated by subscripts, for example: HT, ,H , N, , ,HT . For most engineeringpurposes, the hemispherical total emittance HT suffices.emittance, totaltotal T or (t), nanT or (t),nan emittance that is an integrated average over all wavelengths of radiantenergy emitt
48、ed.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 the melt into fibers.DISCUSSIONCommonly referred to a
49、s fiber glass.DISCUSSIONTo form an insulation product, there are often other materials applied to the fibrous glass such as binders, oils, etc.graybody, na body having the same spectral emittance at all wavelengths.glass fiber, nfiber manufactured as continuous filament from molten glass, normally used for reinforcement, tissue or textiles.glass wool,nSee fibrous glass.heat flow; heat flow rate, Q,nthe quantity of heat transferr
