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“The Right to Information, The Right to Live” “Step Out From the Old to the New”

IS 3069 (1994): Glossary of terms, symbols and units

relating to thermal insulation materials [CHD 27: Thermal
Insulation]

“!ान $ एक न' भारत का +नम-ण”

Satyanarayan Gangaram Pitroda
“Invent a New India Using Knowledge”

“!ान एक ऐसा खजाना > जो कभी च0राया नहB जा सकता ह”

है”
ह
Bhartṛhari—Nītiśatakam
“Knowledge is such a treasure which cannot be stolen”
 ( Reaffirmed 2004 )

GLOSSARY OF TERMS, SYMBOLS AND

UNITS RELATING TO THERMAL
INSULATION MATERIALS
( First Revision)

UDC 662’998 : 001’4

@ BIS 1994

BUREAU OF INDIAN STANDARDS

MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG
NEW DELHI 110002

January 1994 Price Gromp 7

.
Thermal Insulation Materials Sectional Committee, CHD 027

FOREWORD

This Indian Standard was adopted by the Bureau of Indian Standards, after the draft finalized by
the Thermal Insulation Materials Sectional Committee had been approved by the Chemical
Division Council.
The thermal insulation industry in India has made considerable progress in recent years. Lately,
with the expansion of domestic market and renewed thrust on the front of energy conservation,.
an added fillip has been provided to the industry for rapid growth. This glossary is, therefore,.
being brought out to meet the growing need for unambiguous exchange of commercial and scientific
information pithin the industry, and to inculcate an increasing scientific bias in the use of terms,
indigeneous arid foreign, which are current in the thermal insulation trade. The use of this
standard over the years will help to eliminate the ambiguity and confusion arising from different.
interpretation of terms used in thermal insulation trade and industry.
This standard was first published in 1965. On the basis of the experience gained since then, the
definitions in this revision have been presented under three sections:
Section I Thermal Insulation Materials and Products;
Section II Thermal Insulation Properties; and
Section. III Heat Transfer Conditions and Associated Properties of Materials.
The scope of this standard has also been widened to define thermal insulation properties and, heat
transfer conditions and associated properties of these materials.
Technical terms and units ‘of measurements regarding thermal insulating materials, in the
temperature range - 200°C to + 1 OOO°C, have been precisely defined in the manner they are
applicable to the relevant Indian Standard. Some definitions have been further clarified by giving_
mathematical expressions, while mathematical symbols have been mentioned for some others.
These symbols shall be used as a standard practice. Special care has been taken to avoid multi-
plicity of units. Further, the units specified in this standard have been selected on the basis of
experimental aspects so that the units are commensurate with the magnitude of test results normally
obtained.
The definitions given are based on the following guiding principles:
a) Terms ending in ‘-ivity’ designate properties which do not depend on size or shape of the
component. They are specific physical properties of the material of which the component
is composed. On the other hand, the corresponding terms ending in ‘-ante’ stand for the
property of that particular component and take proper account of the size and shape as.
well as the specific physical properties of the component.
b) The words ‘hot’ and ‘cold’ refer to relatively higher or lower temperatures, when the
conditions of two or more surfaces or articles are compared.
c) The terms given refer only to homogeneous and uniform materials (and components large
enough for the irregularities to be considered as negligible ) under steady state of heat flow.
lt is assumed that dimensions of the component are large as compared with those of their
constituent particles. Materials made of several components which cannot be treated as.
homogeneous and uniform form the point of view of heat flow have been referred to as
structures.
In the preparation of this standard, considerable assistance has been derived from the following:
IS0 7345 : 1987 Thermal insulation - Physical quantities and definitions
IS0 9251 : 1987 Thermal insulation - Heat transfer conditions and properties of materials -
Vocabulary
IS0 9346 : 1987 Thermal insulation - Mass transfer - Physical quantities and definitions
BS 3533 : 1981 Glossary of thermal insulations
BS 874 ( Part 1 ) : 1986 Determining thermal insulating properties : Part 1 Introduction,,
definitions and principles of measurement
ASTM C 168 : 80a Standard definitions of terms relating to thermal insulating materials.
Should any difference exist between the definitions in this glossary and those in the standards for
the individual materials, the latter shall prevail.
The composition of the technical committee responsible for the preparation of this standard is given
in Annex A.

-___--.--
 IS 3069 : 1994

Indian Standard
GLOSSARYOFTERMS,SYMBOLSAND
UNITSRELATINGTOTHERMAL
INSULATIONMATERIALS
( First Revision)
1 SCOPE Section I - Thermal Insulation Materials
1.1 This standard defines the terms and abbre- and Products
.viations and, also covers the symbols and u&t8 Section II - Thermal Insulation Properties
used in thermal insulation industry.
Section III - Heat Transfer Conditions and
1.2 The definitions have been presented under Associated Properties of
.three sections as follows: Materials

2 DEFINITION OF TERMS

SECTION I THERMAL INSULATION MATERIALS AND PRODUCTS

A Blanket Insulation

-Air Space A relatively flat and flexible insulation in

coherent sheet form furnished in units of 8Ub-
Space between surfaces containing air. stantial area.
Aluminium Foil
Blanket Insulation Metal - Mesh
Aluminium metal in the form of a thin strip,
rolled or unrolled. Blanket insulation covered by flexible metal -
mesh facings attached on one or both sides.
Asbestos Fibre

The name given to a number of naturally Block Insulation

,occurring mineral silicates which possess a crys-
talline structure and which may be separated Rigid insulation preformed into rectangular cross
Jnto fibres ( fine filaments ). section with thickness not significantly smaller
NOTE - Asbestos fibres are not to be used in the than the other dimensions.
manufacture of thermal insulating products as
their health hazards are well known. Blowing Wool
B
Fibrous insulation material subdivided into
.Backiog Insulation granules or pellets for application or installation
by pneumatic equipment.
Insulation material which is shielded from
excessive temperature and/or abrasive condition8 Blowa Insulation
by a more heat resistant and/or protective
material. Loose fill insulation which has been applied or
installed using pneumatic equipment.
Batt
Board ( Slab or Sheet Insulation )
A portion of a mat in the form of a rectangular
piece g,:nerally between 1 m and 3 m in length A rigid insulation product of rectangular shape
.and usually supplied flat or folded.
with or without a facing with the thicknesr
significantly smaller than the other dimensions.
Binder

An additive normally consisting of an adhesive Bonded Insulation

to make possible the forming of fibrous or
powder type material into desired forms or Insulation with a suitable binder made available
shapes. in desired preformed shape.

1
IS 3069 : 1994

C forms a relatively hard, protective surface.

Calcium Silicate Cement Insulating

Insulation comprising hydrated calcium silicate A mixture of dry granular, flaky, fibrous or-
with fibres incorporated as a reinforcing agent. powdery materials that when mixed with water
develops a plastic consistency, and when dried.
Cellular Concrete in place forms a coherent covering that affords
substantial resistance to heat transmission.
Concrete containing a substantial number of
small air cells. Ceramic Flbre

Cellular Elastomeric The fibrous inorganic insulation material consis-

ting of metallic oxides which may be of silica
Insulation composed principally of natural or and alumina or a mixture of silica and other
synthetic elastomers, or both, processed to form metallic oxides.
a flexible, semi-rigid, or rigid foam whioh has a
predominantly closed-cell structure. Coating

Cellular Glass A liquid or semiliquid material that dries or-

cures to form a protective finish, suitable for
Insulation composed of glass, processed to form application to thermal insulation or other sur--
a rigid foam, having a predominantly closed- faces in thickness of 30 mils ( 0.76 mm ) or less,
cell structure. per coat.

Cellular Material Composite Insulation

A material having many cells (either open or Multilayer insulation in which each layer of
closed or both) dispersed throughout its volume. insulation has a property different from that of
the neighbouring layer.
Cellular Plastic
Cork Board
A generic term for plastics material of which
the density is reduced by the presence of nume- Preformed insulation material composed of
rous small cavities (cells ), interconnecting or granulated cork bonded by heating under
not, dispersed throughout the mass. pressure, with or without added adhesive.

Cellular Polystyrene Coverage

Insulation composed principally of polymerized The area or yield provided by a package of loose
styrene resin, processed to form a rigid foam fill insulation when applied in accordance with
having a predominately closed-cell structure. the manufacturer’s instructions to achieve a.
declared thermal performance.
Cellular Polyurethane
Covering Capacity ( for Insulating Cement )
Jnsulation composed principally of the catalyzed
reaction product of polyisocyanate and polyhy- Dry - The area covered to a specified dry thick-
droxy compounds, processed usually with ness by a specified amount of dry cement when
fluorocarbon gas to form a rigid foam having a mixed with the specified amount of water,.
predominately closed-cell structure. moulded and dried to constant weight and
specified thickness.
Celluiosic Fibre
wet - The area covered to a specified wet thick-
Insulation composed principally of cellulose ness by a specified amount of dry cement when-
fibres usually derived from paper, paperboard mixed with the specified amount of water and
stock or wood, with or without binders. moulded to specified thickness.

Cellulosic ( Cellulose ) Insulation Curved Board

A rigid product of which one cross section is.
Cellulose fibre derived from paper, paperboard rectangular and the second has the form of an
stock or wood, with or without binders. arc of an annulus of internal diameter usually,
exceeding 1 metre.
Cement Finishing
D
A mixture of dry fibrous or powdery materials,
or both, that, when mixed with water, develops Declared Thickness
a plartic consistency and, when dried in place The thickness declared by the manufacturer as..

2
 IS 3069 : 1994

that which will provide the declared thermal Flexible Insulation

# roperties.
Insulation material which is not rigid and can
Diatomaceoos Brick easily drape or take the shape of the surface on
which it is applied.
Fired insulating brick composed mainly of the
skeleton of diatoms ( cellular siliceous particles Foamed Slag Aggregate
.of microscopic size ). Furnace slag treated to produce light-weight
aggregate.
.Diatomaceoas Insulation
Foamed Slag Concrete
Insulation composed mainly of the skeletons
.of diatoms. Insulating concrete with foamed slag as
aggregate.
Diatomaceous Silica
Foamed-in-Place Insulation
Insulation composed principally of diatomaceous
earth with or without binders and which usually Insulation material sprayed or injected in a
contains reinforcing fibres. foamed liquid state which then sets into a rigid
insulating material.
E
G -
‘Expanded Clay
Glass Fibre
Light weight granular material havingan internal
cellular structure formed by expanding a clay A mineral fibre material produced predominantly
mineral by heat. from molten glass.

Expanded Polyvinyl Chloride Glass Wool

A plastic material with a substantially closed cell A wool produced from glass fibre with or with-
structure based on polymers made with vinyl out binder/resin, in various shapes, forms and
chloride expanded to form a cellular structure sizes with or without facings.
consisting substantially of closed cells.
Granulated Cork
:Expansion Joint Cork, ground or milled into granules or small
particles.
An arrangement of a joint to permit movement,
to relieve stresses caused by expansion or Granulated Wool
contraction.
Fibrous material processed mechanically to give
F modulated or granulated wool.
lFacing H
A protective or decorative or functional surface High Vacuum Insulation
applied as the outermost layer of an insulating
system. A sealed space from which the air has been
removed to produce a low pressure.
Telt
Hot Face Insulation
A flexible or semi-rigid sheet of non-woven
fibres held together by mechanical means with- Insulation which is exposed directly to hot gases
aut the USCof binders, adhesives or conforming or hot surfaces.
media.
I
Fibrous Insulations
Insulating Brick
Insulation composed of naturally occurring or
.manufactured fibres. A brick that contains a high volume ratio of air
cells to solid matrix. -
rFinishing Cement
Insulating Castable Refractory
.An insulating cement applid as the outermost
Jayer of insulating system for protective, deco- Insulating concrete containing a suitably graded
rative, or functional purpose. insulating refractory aggregate.

3
fS 3069 : 1994

Insulating Cement ( Industrial ) Lamella Product

A mixture of dry fibrous and powdery materials Mineral wool insulation in which the genera&
that, when mixed with water, develops a plastic orientation of the fibres has been rearranged to
consistency and when dried in place, forms a be perpendicular to the major surfaces.
relatively hard material to protect insulation.
Light Weight Aggregate
Insulating Concrete
Aggregate of porous granules.
a) Concrete, containing a substantial per-
centage by volume of lightweight aggre- Light Weight Concrete
gate. ( See ‘insulating Concrete’ )
b) Concrete made cellular by aeration or
foaming and may be cured by autoclaving. Loose Fill Insulation

Insulating Jacket Granules, nodules, powder or similar forms of

material designed to be installed by hand
An insulation assembly enclosed in fabric, film, pouring or blowing by pneumatic equipment.
paper or thin metal designed to fit a particular Loose Wool
shape.
Fibrous insulation in loose form normally with-
Insulating Plas t :r out a binder or precoated with a binder for
special applications.
Plaster containing a light-weight aggregate.
M
Insulating Rope
Magnesia
Rope composed of mineral fibre loosely braided
with yarn or metal wire. Insulation composed principally of basic
magnesium carbonate which incorporates fibre-
J as a reinforcing agent.

Jacket Mastic

A form of facing applied over insulation. A material of relatively viscous consistencv that
NOTE - It may be integral with the insulation, or
dries or cures to form a protective finish, s&table
field applied using sheet materials. for application of thermal insulation in thick-
nesses greater than 30 mils ( 0’76 mm ) per
L coat.

Lacing Wire Mat

Light gauge metallic wire, single or multi-strand, Flexible fibrous insulation supplied in the form.
used for lacing together adjacent edges of of rolls or batts, which may be faced but not
mattresses or of metal coverings or for securing enclosed.
insulating materials to substantially flat surfaces.
Mattress
Lags
A flexible product comprising an insulating
Preformed rigid materials for longitudinal appli- material faced on one or both sides or totally
cation to cylindrical equipment larger than those enclosed with fabric, film, paper, wire netting or
for which pipe insulation is available. expanded metal or similar covering stitched to.
the insulating material.
These are of three types:
Maximum Service Temperature
a) Plain lags have a rectangular cross section
designed for use on cylindrical vessel of The temperature at which the thermal insulation,2
such a diameter that the lags conform installed at the maximum recommended thickness
sufficiently close to the surface. will continue to perform without degradation
of necessary properties or creation of hazards.
b) Bevelled lags are similar to plain lags but
with one or more edges bevelled. Metal Mesh Blanket
c) Radiused and bevelled lags are bevelled
lags with curved faces to fit the surface of Blanket insulation covered by flexible metal::
a cylindrical vessel. mesh facings attached on one or both sides.

4
 IS 3069 : 1994

Rlicro Porous Silica Polyethylene Foam

“Silica powder in the form of porous particles, A foamed plastics material based on polymers,
the pores having dimensions comparable with derived mainly from ethylene and having a
the mean free path of the molecules of air at substantially open cell structure.
atmospheric pressure. It may optionally contain
a powder which reduces heat transfer by Polyisocyannrate Foam
radiation.
A foamed plastics material with substantially
Mill Board closed cell structure based on polymers in which
the repeated structural units in the chains are
A tough flexible board made from cellulosic mainly of the isocyanurate type.
fibre.
Polystyrene Plastic Foam
Mineral Fibre
A rigid cellular plastics material that has been
Insulation composed principally of fibres nor- expanded from polystyrene or its copolymers.
mally manufactured from rock, slag or glass. These materials are divided into two types:
Mineral Wool a) Board, expanded from expandable polys-
tyrene beads, which is moulded to shape
A wool produced from mineral fibre with or or cut from continuously or discontinu-
without binder/resin, in various shapes, forms ously produced block.
and sizes with or without facings. b) Board, produced by the continuous
extrusion process, either with or without
Mitred Joint natural surface skins.

Pipe insulation sections cut to fit around Polyurethane Foam

elbows, bends or fittings.
A rigid cellular plastics material based on poly-
N urethanes or urethane/isocyanurate polymers.

Nominal Thickness Poured Application

The thickness used for reference purposes in A manual method to install loose fill insulation.
‘specifying tolerances.
Pouring Wool
P
A granulated fibrous material for manual appli-
‘Perlite Insulation cation or pouring.
‘Natural siliceous ore expanded by heat to form Precoated Fibre
a cellular structure.
Fibrous insulation in loose form, precoated with
Perlite Plaster a binder, enabling applications like spraying,
trowelling, etc.
Plaster containing expanded perlite aggregates.
Preformed Insulation
Shenolic Foam
Insulation fabricated in such a manner that at
A rigid phenol formaldehyde cellular material least one surface of the insulation conforms to
produced from the condensation products of the shape of the surface to be insulated.
phenols and formaldehyde, such as resoles and
novolacs, together with hardeners and other Q
additives, for example, surfactants, blowing
agents, fillers, etc. Quilt

Pipe Insulation A mattress, faced on one or both sides or totally

enclosed with fabric, film or paper, stitched or
A preformed rigid or flexible product in the stapled at suitable centres.
shape of an annular cylinder or flat flexible
product for a pipe circumference. R

“Pneumatic Application Radiation Shield

,A method using air to install loose insulation. A product generally in sheet form, of low

5
IS 3069 : 1994

emissivity, used to restrict the transmiosion of Slotted Slab

radiant heat.
An insulation with a deep saw cut channel of
Reference Temperature triangular or wedge shaped cross-section so that
it can be applied to a curved surface.
A temperature selected for use as the basis for
physical property measurement and expression Spray-Applied Polyurethane Foam
of data for those materials for which the physi-
cal properties change with temperature. A rigid cellular plastics material which is
formed-in-place by the catalyzed reaction of
Reflective Insulation polyisocyanate and polyhydroxyl compounds,.
expanded with a chlorofluorocarbon.
Insulation depending for its performance upon
reduction of radiant heat transfer across air Sprayed Insulation
spaces by use of one or more surfaces of high
reflectance and low emittance. A coating of insulating material applied to a
surface by spraying.
Refractory Insulation Brick
A fired insulating brick which will withstand T
high temperatures, normally over 1 100°C.
Thermal Insulation
Rigid Insulation
A product which is intended to reduce heat
Insulating material which retains its manu- transfer through the structure against which or in
factured shape unless constrained to do which it is installed. Numerical limits can be:
otherwise. set only when the specific application is defined..

Rockwool U

Mineral wool produced predominantly from Unbounded Insulation

molten naturally occurring igneous rocks with or
without binder/resin, in various shapes, forms Insulation without binder.
and sizes. with or without facings.
Urea Formaldehyde Foam
Roll
A foamed plastics material with a substantially
Mat supplied in the form of spirally wound open cell structure based on an amino resin
cylindrical packages. made by the polycondensation of urea with
formaldehyde.
Rubber Expanded
V
Cellular rubber having closed cells and made
from a solid rubber compound ( TC-45 ). Vacuum Insulation
S A sealed evacuated space.
Sheet Insulation Vacuum Jacket
See ‘Slab Insulation’. A vacuum insulation product in the form of a
shell or jacket.
Shot
Vacuum Powder Insulation
A solid particle of rock, slag or glass which has
not been fiberized. Powder which has been sealed in an evacuated
space.
Slab Insulation

A rigid insulation product of rectangular shape Vacuum Reflective Insulation

with or without a facing, with the thickness
significantly smaller than the other dimensions. Reflecting surfaces contained in a sealed.
evacuated space.
Slag Wool
Vermiculite Insulation
A mineral wool processed predominantly from
molten slag with or without binder/resin, in A product that results from expanding or
various shapes, forms and sizes, with or without exfoliating a natural micaceous mineral by,
facings. heating.
6
 IS 3069 : 1994

W tion of bonding agent, compressed to form a

board.
Water Vaponr Barrier
Layer intended to prevent water vapour transfer. Wood Wool slab
Water Vapour Retarder ( Barrier )
Wood wool compressed and bonded with an
A material Tar system that adequately impedes inorganic cementing agent.
the transmission of water vapour under specified
conditions. Wool
Wood Fibre Board A random mass of any type of fibres having
Natural wood fibres with or without the addi- wooly consistency.

SECTION II THERMAL INSULATION PROPERTIES

A Conductance Thermal ( C )

Absorptance The time rate of heat flow through a unit area

of a body induced by a unit temperature
The ratio of the radiant flux absorbed by a body difference between the body surfaces ( W/m2.K ).
to that incident upon it.
NOTES
1 The average temperature of a surface is the area
Absorption weighted mean temperature of that surface.
Transform,ation of radiant energy to a different 2 When the defined surfaces of a mass type
form of energy by interaction with matter. thermal insulation are not of equal areas, as in the
case of thermal transmission in two radial direc-
tions or are not of uniform separation ( thick-
Absorptivity ness ), sn appropriate mean value for area and
thickness must be given.
The ratio of thermal radiation absorbed by a 3 When other modes of heat transfer are present
surface to that which is received by the surface. in addition to conduction, the apparent or effec-
It varies with the wavelengths of the radiation tive thermal conductivity is obtained by multiply-
ing the thermal conductance by the average
and, therefore, it depends on the quality of thickness.
radiation.
4 For the case where there is air nassaae
through the body, the effective thermal conductan&
Atmospheric Temperature must include details of the pressure difference
across the body. For a material or assembly where
The temperature of the ambient air measured in radiant energy opacity or transparency affects the
nature of heat transfer, the optical properties must
the shade. be given.

B 5 ‘Total’ or ‘areal’ thermal conductance are often

used as synonyms for thermal conductance.
Blackbody
Conductivity Thermal ( h )
The ideal, perfect emitter and absorber of
thermal radiation. It emits radiant energy at The time rate of heat flow through unit thickness
each wavelength at the maximum rate possible of an infinite slab of a homogeneous material in
as a consequence of its temperature and absorbs a direction perpendicular to the surface, induced
by unit temperature difference ( W/m-K ),
all incident radiance.
( mW/m. K) or ( mW/cm ‘C >.
C NOTES

Conductance Film 1 For practical purposes the lateral extent of a

slab is considered to be infinite when heat flow
laterally is less than twice of the transverse flow.
The time rate of heat flow from a unit area of a
2 A body is considered homogeneous when the
surface to its surroundings, induced by a unit above property is found by measurement to be
temperature difference between the surface and independent of sample dimensions.
the environment. 3 The property must be identified with both specific
NOTE- When the environment is a fluid ( liquid or mean temperature, as it varies with temperature,
gas ), it makes conductance also dependant upon direction and orientation of thermal transmission,
the nature of fluid motion past the surface ( lamiaar as some bodies are not isotropic with respect to the
or turbulent ) and the surface roughners ( W/m’.K ). thermal conductivity.

7
dS 3069 : 1991
4 FJ~ many thermal insulation materials, thermal blackbody at the same temperature under the
transmission occurs by a combination of different same conditions.
modes of heat transfer, and the measured property
should be referred to as an effective or apparent
thermal conductivity for the specific conditions of Emittance Hemispherical ( ln or c2n )
test ( sample thickness and orientation, environ-
ment, applied load, environmental pressure and
temperature difference ). The average directional emittance over a hemi-
spherical envelope covering a surface.
Convection Coefficient ( Film Coefficient ) (fc )
Emittance Spectral [ rh or E ( A, 8, 4 ) 1
The quantity of heat transferred by convection in
An emittance based on the radiant energy emitted
unit time to or from unit area of a surface,
per unit wavelength interval ( monochromatic
divided by the temperature difference between
radiant energy ).
.the surface and the surrounding air or other
.fluid ( W/m*K ) NOTE -Where necessary to avoid confusion,
emittance should be designated by subscrint, for
qc =fcA(b - &I>. example, E& ena, et%., ext. etc. For-most engineer-
ing purposes, the hemispherical total emittance Eht
NOTE-The quantity of heat transferred will suffi-ces.
depend on several factors, such as the velocity of
the air or other dnid, the temperature and the
roughness of the surface. Emittance Total [ et or E ( t ) ]

D An emittance that is an integrated average over

all wavelengths of radiant energy emitted.
Diffusivity Thermal ( cc ) G
Thermal conductivity divided by heat capzcity Greybody
per. unit volume. It is a characteristic property
,of the material and is used in considering tem- A body having the same spectral emittance at
perature distributions when thermal equilibrium all wavelengths.
is not established ( ma/s ).
H
E
Heat Capacity per Unit Mass ( c ) or ( Specific
Effective Ambient Temperature Heat Capacity )
For structures surrounded by air ( or other The quantity of heat required to raise the tem-
fluid ), the effective ambient temperature is a perature of unit mass by one degree ( J/kg K ).
suitably weighted mean between air ( fluid )
,temperature and the mean radiant temperature NOTE - The relevant conditions, such as tempera-
of the surroundings ( “K, “C ). For a fluid ture range and pressure, under which this quantity
is measured should be specified.
.opaque to radiation, the effective ambient tem-
perature is the same as the surrounding fluid Heat Capacity per Unit Volume ( h >
temperature.
NOTE - Significant differences might be obtained The quantity of heat required to raise the tem-
depending on the method of measurement, which perature of unit volume by one degree ( J/m3K ).
should be specified for particular application.
l\IOTE - This is equivalent to the heat capacity
per unit mass of the material multiplied by its bulk
Emissiv ity ( E ) density.

The emissivity of a surface for thermal radiation R

is the ratio of the radiation from unit area of
the surface to the radiation from unit area of a Radiance
full radiator ( ‘black-body’ for which E = I ) at
the same temperature. The rate of radiant emission per unit solid
angle and per unit projected area of a source in
,Emittance ( E ) a stated angular direction ( usually the normal )
from the surface.
The ratio of the radiant flux emitted by a speci- NOTE - The term intensity of radiation is often
men to that emitted by a blackbody at the same used as a synonym for radiance.
temperature and under the same conditions.
Radiant Flux Density
Remittance Directional [ E ( 0, 4 ) ]
The rate of radiant energy emitted from unit
The ratio of the radiance from the surface in a area of surface in all radial directions of the
particular direction to the radiance from a overspreading hemisphere.

8
 IS 3069 : 1994

Radiation Coefficient (fp ) to that which is incident on the surface.

NOTE-The reflectivity depends on the wave-
The net quantity of heat radiated in unit time length of the radiation ‘and this should, therefore,.
from unit area of a surface divided by the tem- be stated. In particular solar reflectivity
given surface usually differs in value from reflec--
for a
perature difference between the radiating surface tivity for radiation at lower temperatures.
and the surroundings with which it is exchang-
ing radiation ( W/m2K ) Resistance Thermal
qr = frA ( el- 4 >
NOTE - The radiation coefficient is a function of
The mean temperature difference, at equilibrium,
the temperature, emissivity and configuration ol the between two defined surfaces of material or a
surface and of the surrounding. construction that induces a unit heat flow rate.
through unit surface area ( ma K/W ).
Radiation Constant ( uE )
NOTES
The quantity of heat radiated in unit time from 1 Thermal resistance and thermal conductance are
unit area of the surface divided by the fourth reciprocals.
power of the absolute temperature T of the 2 See Notes 1 and 2 under ‘Conductance Thermal’.
surface. This applies only to a surface for which For insulation applied to cylinders, thermal resis-
the emitted radiation is proportional to the tance is expressed in terms of unit linear length<
of the insulation.
fourth power of the absolute temperature
( Stefen’s law ). The radiation constant is 3 For the case where there is air passage through
defined by ( W/m2 K4 ) the body, the effective resistance should include
details of pressure difference through the body.
4r = aEAT For a material or assembly where radiant energy
opacity or transparence affect the nature of heat
where u( Stefen’s constant ) is the radiation con- transfer, the optical properties should be given.
stant for a full radiator ( black-body ).
Resistivity Thermal
NOTE - The net heat gained or lost by radiation
is the difference between the heat radiated by the
body and that received by it through radiation from The temperature difference between the parallel
the surroundings. When the surroundings are black; surfaces of infinite slab of a homogeneous.
or are infinitely distant, the net gain or loss of heat material of unit thickness when a unit thermal
by radiation is given approximately by:
transmission is maintained in unit time through
a unit surface area by conduction only in a
qr = GEA T: - T:
( > direction perpendicular to the surface ( m.K/W ).
NOTES
Reflectance
1 Thermal resistivity and thermal conductivity are
The. fraction of the incident radiation upon a reciprocals.
surface that is reflected from the surface. chTr’eal,otes I, 2, 3 and 4 under ‘Conductlvlty
NOTES
1 For an opaque surface, the sum of the reflec- S
tance and the absorptance is unity at equilibrium.
2 Absorptances and reflectances are of various Shape Factor ( S)
types, as are emittances. For most engineering
purposes, the counterparts of the hemispherical
total emittance suffice. Further, the terms absorp- The shape factor of a structure is defined by the
tivity and reflectively, like emissivity, are restricted equation
to apply to materials having opaque, optically flat
surfaces. 4 = KS ( es1 - es2 )
NOTE -This quantity is useful in comparing
Reflectivity ( r ) structures of similar but not simple geometric form.

The reflectivity ofa surface for thermal radiation The shape factors for some common forms of
is the ratio of the amount of radiation reflected bodies are given in Table 1.

Table 1 Common Shape Factors

Body Shape Factors ( S) Remarks
plane slab of area A and AIL By deflnition of conductivity
thickness ‘L’
Tube or hollow cylinder length 2’73 h/log,, ( X/Y) Theoretical value ( assuming
no end losses )
External and internal radii 2x h/0.303 -
Xaod Y log (X/Y)
Hollow sphere, external and 4xXY/(X-Yy) Theoretical value
internal radii X and Y
Rectangular box of uniform A/L + 2.16 Based on experiment
wall thickness ‘L’ internal dimen- I(x+Y+z)+l*LI A = internal area
sions X, Y and, Z where each is =2(xY+Yz_tzx)
greater than l/5.
9
IS 3069 : 1994

Soaking Heat with accessories, vapour retarder and facing

required.
A test condition under which the specimen is
completely immersed in atmosphere maintained Thermal Transmittance ( II)
:at a controlled temperature.
The thermal transmission through unit area of
Solar Absorptivity (A) a given structure divided by the difference
between the effective ambient temperatures on
The ratio of the amount of solar radiation either side of the structure in ‘steady’ state’
absorbed to that which is incident on the conditions ( W/m2 K. ).
surface. NOTES
A = ( 1 -r) 1 If the structure is not a simple slab, it isnecessary
to state where the area is measured.
NOTE - For long wave length ( low temperature )
thermal radiation, that is,, from bodies near room 2 Transmittance differs from ‘conductance’ because
temperature, the absorptivity is equal to the the temperature difference is measured between
emikvity. different positions. For conductance the tempera-
ture difference is that between the faces, for
transmittance it is that between the effective
Specific Heat Capacity ambient temperatures on either side of the
structure. Thus, the thermal transmittance ( U)
See Heat Capacity per Unit Mass ( L’) of a structure involves both the thermal conductance
and the surface coe5cient.s of the structure.

Surface Coefficient ( f > Total Thermal Resistance ( l/U)

Thermal transmission per unit area to or from The sum of the surface resistances and the
a surface in contact with air or other fluid due thermal resistance of the structure itself
to convection, conduction and radiation, divided ( m2 K/W ).
by the difference between the temperature of
NOTE ,-- For a compound structure with plane
.the surface and the effective ambient tempera- and parallel faces, for example, a wall
ture in ‘steady state’ conditions [ W/( m2 K ) I. 1
-= k + + + +- +......+ f
NOTE - The value of the surface coefficient u 1 2
depends on many factors, such as the movement of
air or other fluid, the roughness and emissivity of
the surface and the temperature and nature of the Transference Thermal
surroundings.
The steady state heat flow from or to a body
Surface Resistance ( ljf > through applied thermal insulation and to or
from the external surroundings by conduction,
The reciprocal of surface coefficient ( m2 K/W ). convection and radiation. It is expressed as the
time rate of heat flow per unit area of the body
T surface per unit temperature difference between
the body surface and the external surroundings.
Thermal Insulation Transmission Heat
A material or assembly of materials used to The quantity of beat flowing through unit area
provide resistance to heat flow. due to all modes of heat transfer induced by the
prevailing conditions.
‘Thermal Insulation System
NOTE - Heat transfer may be by solid conduc-
tie?, mass transfer, gas conduction, convection and
Applied or installed thermal insulation complete radiation, either separately or in any combination.

SECTION III HEAT TRANSFER CONDITIONS AND ASSOCIATED

PROPERTIES OF MATERIALS

A) HEAT TRANSFER CONDITIONS N

Non-steady State
H
Condition for which relevant parameters vary
Heat Transfer with time.
P
Transmission of energy by thermal conduction, .
thermal convection and thermal radiation or a Periodic State
combination of these. Non-steady state in which values of the relevant

10
 IS 3069 : 1994

parameters repeat themselves at regular time D

intervals independent of initial conditions.
Degree Kelvin ( K )
S
The unit of temperature measurement on the
Steady State International Temperature Scale (n OK = n°C +
273’15 ).
Condition for which all relevant parameters do OR
not vary with time. The abbreviation used internationally for
indicating temperature interval or difference on.
T the International Temperature Scale.

Transient State Dewpoint Temperature

Non-steady state in which values of the relevant The temperature at which condensation of
parameters evolve from an initial state asymp- water vapour in a space begins for a given state
totically to either steady or periodic state. of humidity and pressure. Alternatively, the
temperature corresponding to saturation ( 100,
percent relative humidity ) for a given absolute
B) GENERAL PROPERTIES OF MATERIALS humidity at constant pressure ( OK or OC ).
AND TERMS
H
A
Heterogeneous Medium
Air Permeability
Medium in which relevant properties are a
The fluid permeability of a material where air is function of the position within the medium
the given fluid. itself due to the presence of dissimilar
constituents.
Anisotropic Medium
Homogeneous Medium
Medium in which relevant properties are a
function of direction. Medium in which relevant properties are not a
function of the position within the medium itself
but may be a function of such parameters as.
Apparent Density Under Specieed Load time, direction, temperature, etc.
The density of a fibrous or other loose material Humidity Absolute
under specified load.
The mass of water vapour per unit volume
B ( kg/ms ).
Bulk Density Humidity Relative

Refers to apparent density of powders, aggre- The ratio of the mole fraction of water vapour
gates and substances measured by allowing them present in the air to the mole fraction of water
to settle after a specified mechanical agitation vapour present in saturated air at the same
( kg/m3 1. temperature and barometric pressure. Approxi-
mately, it equals the ratio of the partial
C pressure or density of the water vapour in the
air to the saturation pressure or density,
Compressibility respectively, at the same temperature ( percent )_

The relation between deformation and applied I

mechanical pressure on a material.
Isothermal Region
Compressive Strengtb or Crushing Strength
A region is said to be at isothermal temperature
The capacity of a material to withstand when every point in that surface is at the same
mechanical pressure up to the point of fracture, temperature.
and in the case of materials which do not fail M
by shattering, the compressive strength may be Mass Density ( p )
deduced arbitrarily from a load deformation
curve. Mass divided by volume.

11
IS 3069 : 1994

NOTES R
1 For porous materials one can identify the density
of the solid material and the bulk density, and for Resilience
granular materials also the density of the
grains.
The ability of the material to recover its original
2 The symbo1 of density is ( p) and the unit is dimensions after having been subjected to
kilograms per cubic metre ( kg/m* ). deformation.
Medium Granular Loose Fill
Resistance, Abrasion
Medium comptiSing a continuous gas phase
The ability to withstand scuffing, scratching,
with solid incohefent inclusions, the shape of
rubbing or windscouriflg.
which does not have a predominant dimension.
Resistance, Freeze-Thaw
Medium Isotropic
Resistance to cycles of freezing and thawing
Medium in which relevant properties are not a
that could affect application appearance or
function of direction but may be a function of
time, performance.
the position within the medium,
temperature, etc. S
P Specific Volume ( Insulating Cements )

Porosity ( E) The volume in cubic metres of one tonne of a

cement in powder form.
Total volume of the voids ( both open and NOTE - This term is applicable only to insulating
closed ) within a porous medium divided by the elements and not to fibrous materials.
total volume of the medium.
NOTE- Porosity can either be the total porosity Specific Weigbt ( Granular and Powdered
defined by the expression E = 1 - ( p/p,) where ( p ) Materials )
is the apparent density of the material and ( ps )
is the density of the solid matrix or the apparent The mass of the material in tonnes required to
porosity determined by some experimental method.
completely fill up one cubic metre of space after
Porosity Local ( up ) thoroughly agitating in a container in a specified
manner. The size and the shape of the container
The porosity at any point within a body when as well as its details are also specified.
the volume of an element enclosing the point is
small with respect to the entire body but large Stable Medium
.enough to evaluate a meaningful average.
Medium in which relevant properties are not a
Porous Medium function of time, but may be a function of
coordinates, direction, temperature, etc.
Medium which is heterogeneous due to the
presence of finely divided solid phases and Strength, Transverse ( or Flexural )
voids.
The breaking load applied normal to the neutral
Porous Medium, Cellular axis of a beam ( kPa ).

Medium comprising a continuous solid phase T

containing cavities interconnected in such a
way that the gaseous phase is also continuous. Tensile Strength

Porous Medium, Fibrous The capacity of the material to withstand

tension up to the point of fracture ( kPa ).
Medium comprising a continuous gas phase
,with solid inclusions having length as a W
predominant dimension.
Water Vapour Diffusion
Porous Medium, Homogeneous
The process by which water vapour spreads or
Medium in which the porosity is independent moves through permeable materials caused by
of the point where the value is computed. the difference in water vapour pressure ( m*/s ).

Porous Medium, Interconnected Water Vapour Permeability

Medium comprising a continuous solid phase The time rate of water vapour transmission
containing cavities interconnected in such a through unit area of a flat material of unit
way that the gaseous phase is also continuous. thickness induced by unit vapour pressure
12
 IS 3069 : 1994

difference between two specific surfaces under Water Vapour Resistivity

specified temperature and humidity conditions
( kg/m. s. Pa ). The steady vapour pressure difference that
NOTE - Permeance is a performance evaluation induces unit time rate of vapour flow through
and not a property cf the material. unit area and unit thickness of a flat material
( or construction that acts like a homogeneous
Water Vapour Pressure body ) under specific conditions of temperature
and relative humidity at each surface
( m. s. Pa/kg ).
The pressure of water vapour at a given
NOTE - Vapour resistivity is the reciprocal of-
temperature, also the component of atmospheric vapour permeability.
pressure contributed by the presence of water
vapour ( PC ). Water Vapour Transmission Rate
Water Vapour Resistance The steady water vapour flow in unit time
through unit area of a body, normal to specific
The steady vapour pressure difference that parallel surfaces under specific condi tons of
induces unit time rate of vapour flow through temperature and humidity at each isurface
unit area of a flat homogeneous body under ( kg/s ).
specific conditions of temperature and relative
humidity at each surface ( ma. s. Pa/kg ). Wetting and Adhesion Surface
NOTE - Vapour resistance is the reciprocal of
vapour permeance. It is the arithmatic product The mutual affinity of and bonding between
of the resistivity and thickness. finish and the surface to which it is applied.

ANNEX A
( Foreword )
COMMITTEE COMPOSITION

i Thermal Insulation Materials Sectional Committee, CHD 027

‘I, Chairman
PROPB. C. RAYCHAUDHURI
B-138 Sarita Vihar, New Delhi

i Members Representing
SHRI K. N. AOARWAL Central Building Research Institute, Roorke
Shri M. P. CHITRE Indian Oil Corporation ( R & D Division ), New Delhi
SHRI SOVNATH( Alternate )
SHRI M. K. CHOKJRASIA Metallurgical and Engineering Consultants ( India ) Ltd aRanchi:
SHRI A. K. DASGUPTA Steel Authority of India Lfd, Ranchi
SHRI M. S. MUKHOPADHYAY( Alternate )
SHRI R. N. GANJOO BASF India Ltd, Bombay
SHRI B. JOSHI( Alternate )
SHRI A. K. GUPTA Hyderabad Industries Ltd, Hyderabad
SHRI AJAY GUPTA U. P. Twiga Pibreglass Ltd, New Delhi
SHRI S. BANSAL( Alternate )
SHRI G. C. PANDIT Minwool Insulation Ltd, Bombay
SHRI L. N. BADRUKA ( Alternate )
SHRI R. P. PUNI Punj Sons Pvt Ltd, New Delhi
SHRI J. K. CHOPRA( Alternate )
SHRI G. R. RAJAGOPALAN Engineers India Ltd,. New Delhi
SHRI R. V. RAMACHANDRAN Tata Consulting Engmeers, Bombay
SHRI D. PADMANABHA( AIternate )
REPRESENTATIVE Desein Consultants Pvt Ltd, New Delhi
ERP$3SE$T$TII Ministry of Energy ( Deptt of Coal ), New Delhi
Projects & Development India Ltd, Sindri
Di S: P. S. KHA~SA ( Alternate )
SHRI P. ROY Bakelite Hylam Ltd, Bombay
SHRI B. DURAI ( Alternate )
SHRI R. SACHDEVA Directorate General of Technical Development, New Delhi
SHRI K. V. SINGH ( Alternate )
SHRI R. SANKARAN BHEL, Hyderabad
SHRI S. K. KUNDU ( Alternate )
SHRI S. S. PHOGAT( Alternate )
SHRI A. SHARIP FOP Ltd, Bombay
SHRI R. SRINIVASAN( Alternate )
SHRI R. K. SIN~HAL NTPC, New Delhi
SHR! JADAV DATTA ( Alternate )
( Continued on page 14 j

13
iS 369 : 1994

( Continued from page 13 )

Members Representing
SHRI N. SRINIVAS Lloyd Insulations ( India ) Pvt Ltd, New Delhi
SHRI C. P. KHANNA ( Alternate )
SHRI NIMISHV. SURA Newlcem Products Corporation, Bombay
SHRI V. A. SURA( Alternate )
SHRI T. UDAYAKUMAR PIBCO Limited, New Delhi
SHRI A. K. SEN (Alternate )
SHRI C. V. VENKATAKRISHNAN Beardsell Ltd. Madras
SHRI V. P. WAS~N National Physical Laboratory, New Delhi
~HRI K. N. BHATNAQAR( Alternate )
DR R. K. SINOH, Director General, BIS ( Ex-officio Member )
Director ( Chem )

Member Secretary
SHRI SANJAYGUPTA
Assistant Director ( Chem ), BIS

14
Bureau of Indian Standards

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Amendments Issued Since Publication

Amend No. Date of Issue] Text Affected

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