1、Designation: C168 15aC168 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 parenth
2、eses 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 m
3、aterials 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 sa
4、fety 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.1.4 This international standard was developed in accordance with internation
5、ally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D3574 Test Me
6、thods 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 and Definitions33. Terminology3.1 Definitions:absorp
7、tance, nthe ratio of 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 transmissi
8、on byseveral modes of 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 o
9、fthickness. When nonconductive 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.DISCUSS
10、ION1 This terminology is under the jurisdiction of ASTM Committee C16 on Thermal Insulation and is the direct responsibility of Subcommittee C16.94 on Terminology.Current edition approved Oct. 15, 2015June 1, 2017. Published October 2015June 2017. Originally approved in 1941. Last previous edition a
11、pproved in 2015 asC168 15.C168 15a. DOI:101520/C016815A.DOI:101520/C0168-17.2 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 th
12、e ASTM website.3 Available from American 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 previ
13、ous version. Becauseit may not be technically 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 Int
14、ernational, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1Test data using the “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 th
15、ermal conductivity or resistivity, are valid only for the same conditions.DISCUSSIONTest 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 s
16、ystem C or system R measurements 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
17、.DISCUSSIONSee entire discussion 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 ga
18、s.DISCUSSIONThe resulting 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 emit
19、ter and absorber of thermal 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 insu
20、lation in coherent sheet form furnished in units of substantial area.blanket insulation, metal mesh, nblanket 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 p
21、reformed into rectangular 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 na
22、tural or synthetic elastomers, 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 comp
23、osed of the reaction 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 s
24、tructure.cellular polyurethane, 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
25、of cellulose fibers usually 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.
26、C168 172cement, insulating, na 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 insulat
27、ion jacketing).closed cell foam, na material comprised predominantly of individual non-interconnecting cellular voids.coating, 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
28、 less, per coat.conductance, 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
29、surface (laminar or turbulent). (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 speci
30、fied as a material C. 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.DI
31、SCUSSIONWhen the surfaces 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 “a
32、real” thermal conductance 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
33、of a homogeneous material induced bya unit temperature gradient in a direction perpendicular to that unit area. ( or k in SI units: (W/m2)/(K/m) = Wm K.) ( or kin inch-pound units: (Btu/h)/ft2/(F/ft) = Btuh ft F) or (Btu/h)/ft2/(F/in.) = Btu in./h ft2 F.) (See discussion under apparentthermal conduc
34、tivity.)DISCUSSIONThermal 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 fol
35、lows:Flat2slab geometry 5QA LT (1)where:Q = heat flow rate,A = area through which Q passes, andC168 173L = 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)where:1 = leng
36、th,r2 = the outer radius, 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
37、gradient vector. Except 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
38、,A = area through which 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 th
39、e T range, and this range 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 do
40、es not apply. See also, 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 insulat
41、ion jacketing),nSee moisture 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 ce
42、ment when mixedwith the 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
43、material. ( in SI units: 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 tem
44、perature, nthe temperature 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.C168 174diatomaceou
45、s silica, ninsulation composed 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
46、.) (In inch-pound units: (Btu/(hrft) F)/(lb/ft3)(Btu/(lbF) = ft2/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.emittance, directional (; ), nthe ratio of the radiance from a surface in a parti
47、cular direction to the 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
48、per unit wavelength 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 t
49、hat is an integrated 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 the melt into fibers.DISCUSSIONCommonly referred to as fiber glass.DISCUSSIONTo form an insulation product, there are often ot
