ASTM C168-05

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Designation:C168–05
Standard Terminology Relating to
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Thermal Insulation
This standard is issued under the fixed designation C 168; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
attempts beyond an apparatus range or calibration.
1. Scope
DISCUSSION—Useofthe“apparent”modifierwithsystem Corsystem
1.1 This standard provides definitions, symbols, units, and
R measurements is not permitted.
abbreviations of terms used in ASTM standards pertaining to
apparent thermal resistivity, r , n—a thermal resistivity
thermal insulating materials, and to materials associated with
a
assigned to a material that exhibits thermal transmission by
them.
several modes of heat transfer resulting in property variation
2. Referenced Documents
with specimen thickness, or surface emittance. See resistiv-
ity, thermal.
2.1 ISO Standard:
ISO 7345 Thermal Insulation—Physical Quantities and
DISCUSSION—Seeentirediscussionunder apparent thermal conduc-
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Definitions
tivity.
3. Terminology batt, n—blanket insulation manufactured to dimensions as
required by a specific application.
3.1 Definitions:
blackbody, n—the ideal, perfect emitter and absorber of
absorptance, n—the ratio of the radiant flux absorbed by a
thermal radiation. It emits radiant energy at each wavelength
body to that incident upon it.
at the maximum rate possible as a consequence of its
absorption, n—transformation of radiant energy to a different
temperature, and absorbs all incident radiance.
form of energy by interaction with matter.
blanket, n—flexible insulation product, supplied rolled or flat.
apparent thermal conductivity, l , k , n—a thermal con-
a a
blanket insulation, n—a relatively flat and flexible insulation
ductivity assigned to a material that exhibits thermal trans-
in coherent sheet form furnished in units of substantial area.
mission by several modes of heat transfer resulting in
blanket insulation, metal mesh, n— blanket insulation cov-
property variation with specimen thickness, or surface emit-
ered by flexible metal-mesh facings attached on one or both
tance. See conductivity, thermal.
sides.
block insulation, n—rigid insulation preformed into rectangu-
DISCUSSION—Thermal conductivity and resistivity are normally con-
lar units.
sidered to be intrinsic or specific properties of materials and, as such,
should be independent of thickness. When nonconductive modes of
board insulation, n—semirigid insulation preformed into
heat transfer are present within the specimen (radiation, free convec-
rectangular units having a degree of suppleness particularly
tion) this may not be the case. To indicate the possible presence of this
related to their geometrical dimensions.
phenomena (for example, thickness effect) the modifier “apparent” is
calcium silicate, n—insulation composed principally of hy-
used, as in apparent thermal conductivity.
drous calcium silicate, and which usually contains reinforc-
DISCUSSION—Test data using the “apparent” modifier must be quoted
ing fibers.
only for the conditions of the measurement. Values of thermal conduc-
tance (material C) and thermal resistance (material R) calculated from cellular elastomeric, n—insulation composed principally of
apparent thermal conductivity or resistivity, are valid only for the same
natural or synthetic elastomers, or both, processed to form a
conditions.
flexible, semirigid, or rigid foam which has a predominantly
DISCUSSION—Test data labeled with “apparent” shall not include any
closed-cell structure.
equipment related measurement errors induced due to measurement
cellular glass, n—insulation composed of glass processed to
form a rigid foam having a predominantly closed-cell
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structure.
This terminology is under the jurisdiction of ASTM Committee C16 on
Thermal Insulation and is the direct responsibility of Subcommittee C16.94 on cellular polyimide, n—insulation composed of the reaction
Terminology.
product in which the bonds formed between monomers
Current edition approved June 1, 2005. Published June 2005. Originally
during polymerization are essentially imide units forming a
approved in 1941. Last previous edition approved in 2003 as C 168 – 03.
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cellular structure.
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C168–05
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cellular polystyrene, n—insulation composed principally of perpendicular to that unit area. (l or k in SI units: (W/m )/
polymerized styrene resin
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