EN ISO 7345:1995
(Main)Thermal insulation - Physical quantities and definitions (ISO 7345:1987)
Thermal insulation - Physical quantities and definitions (ISO 7345:1987)
Defines physical quantities used in the field of thermal insulation, i.a. quantity of heat, heat flow rate, density of heat flow rate, thermal conductivity, thermal resistance, thermal transmittance, heat capacity, thermal diffusivity, thermal effusivity etc., and gives the corresponding symbols and units.
Wärmeschutz - Physikalische Größen und Definitionen (ISO 7345:1987)
Diese Internationale Norm definiert physikalische Größen aus dem Bereich des Wärmeschutzes und enthält die entsprechenden Symbole und Einheiten. ANMERKUNG: Da der Anwendungsbereich dieser Internationalen Norm auf den Bereich des Wärmeschutzes beschränkt ist, unterscheiden sich einige der in Abschnitt 2angegebenen Definitionen von den Definitionen in ISO 31/4 "Größen und Wärmeeinheiten". Diese Begriffe sind mit einem Stern gekennzeichnet.
Isolation thermique - Grandeurs physiques et définitions (ISO 7345:1987)
La présente Norme internationale définit les grandeurs physiques utilisées dans le domaine de l'isolation thermique, et donne les unités et symboles correspondants.
NOTE -- Étant donné que l'objet de la présente Norme internationale est limité à l'isolation thermique, certaines définitions données au chapitre 2 différent de celles données dans l'ISO 31/4, Grandeurs et unités de chaleur. Pour identifier de telles différences, un astérisque a été inséré avant le terme concerné.
Toplotna izolacija - Fizikalne količine in definicije (ISO 7345:1987)
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
01-december-1997
7RSORWQDL]RODFLMD)L]LNDOQHNROLþLQHLQGHILQLFLMH ,62
Thermal insulation - Physical quantities and definitions (ISO 7345:1987)
Wärmeschutz - Physikalische Größen und Definitionen (ISO 7345:1987)
Isolation thermique - Grandeurs physiques et définitions (ISO 7345:1987)
Ta slovenski standard je istoveten z: EN ISO 7345:1995
ICS:
01.060 9HOLþLQHLQHQRWH Quantities and units
27.220 Rekuperacija toplote. Heat recovery. Thermal
Toplotna izolacija insulation
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
ISO
INTERNATIONAL STANDARD
Second edition
INTERNATIONAL ORGANIZATION FOR STANDARDIZATION
ORGANISATION INTERNATIONALE DE NORMALISATION
MEXAYHAPOfiHAfl OPTAHM3A~MR l-l0 CTAH,lJAPTM3A~MM
Thermal irkulation - Physical quantities
and definitions
Grandeurs ph ysiques et dbfinitions
lsola tion thermique -
Reference number
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of
national Standards bodies (ISO member bodies). The work of preparing International
Standards is normally carried out through ISO technical committees. Esch member
body interested in a subject for which a technical committee has been established has
the right to be represented on that committee. International organizations, govern-
mental and non-governmental, in liaison with ISO, also take part in the work.
Draft International Standards adopted by the technical committees are circulated to
the member bodies for approval before their acceptance as International Standards by
the ISO Council. They are approved in accordance with ISO procedures requiring at
least 75 % approval by the member bodies voting.
International Standard ISO 7345 was prepared by Technical Committee ISO/TC 163,
Thermal insula tion .
This second edition cancels and replaces the first edition (ISO 7345 : 1985) ; clauses 0
and 3 are new.
Users should note that all International Standards undergo revision from time to time
and that any reference made herein to any other International Standard implies its
latest edition, unless otherwise stated.
0 International Organkation for Standardization, 1987
Printed in Switzerland
ii
ISO 7345 : 1987 (E)
Page
Contents
. . . . . 1
0 Introduction .
................................... . . . . . 1
1 Scope and field of application
. . . . . 1
2 Physical quantities and definitions .
3 Energy Performance of buildings .
Symbols and units for other quantities. .
5 Subscripts .
Annex
Concept of thermal conductivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . .
Ill
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INTERNATIONAL STANDARD ISO 7345 : 1987 (E)
- Physical quantities
Thermal insulation
and definitions
0 Introduction
This International Standard forms part of a series of vocabularies related to thermal insulation.
The series will include
ISO 7945, Thermal insulation - Ph ysical quan tities and definitions.
ISO 9251, Thermal insulation - Heat transfer conditions and properties of materials - Vocabulary.
ISO 9346, Thermal insulation - Mass transfer - Ph ysical quan tities and definitions.
ISO 9229, Thermal insulation - Thermal insulating materials and products - Vocabulary. l1
ISO 9288, Thermal insula tion - Heat transfer b y radia tion - Ph ysical quan tities and definitions. 1 )
1 Scope and field of application
This International Standard defines physical quantities used in the field of thermal insulation, and gives the corresponding Symbols
and units.
NOTE - Because the scope of this International Standard is restricted tothermal insulation, some of the definitions given in clause 2 differ from those
given in ISO 31/4, Quantities and units of heat. To identify such differentes an asterisk has been inserted before the term concerned.
Quantity
Unit
2 Physical quantities and definitions
J
2.1 heat; quantity of heat
Q
@ w
2.2 heat flow rate: Quantity of heat transferred to or from a System divided by time:
dQ
@=-----
dt
W/m2
2.3 density of heat flow rate: Heat flow rate divided by area :
d@
4 -
=cL4
NOTE - The word “density” should be replaced by “surface density” when it may be confused with “linear
density” (2.4).
1) In preparation.
ISO7345:1987 (E)
Quantity Unit
2.4 linear density of heat flow rate: Heat flow rate divided by length: Wlm
d@
41 = y-
A.
2.5 thermal conductivity: Quantity defined by the following relation: W/(m- Kl
4”
-4 grad T
NOTE - A rigorous treatment of the concept of thermal conductivity is given in the annex, which also deals
with the application of the concept of thermal conductivity to porous isotropic or anisotropic materials and
the influence of temperature and test conditions.
r
2.6 thermal resistivity: Quantity defined by the following relation: (rnm K)/W
gradT= -r-q
NOTE - A rigorous treatment of the concept of thermal resistivity is given in the annex.
2.7 *thermal resistance: 1) Temperature differente divided by the density of heat flow rate in R (rn2a K)/W
the steady state condition:
Tl - *z
R=
NOTES
For a plane layer for which the concept of thermal conductivity applies, and when this property is
constant or linear with temperature (see the annex):
d
RZ---
A
where d is the thickness of the layer.
These definitions assume the definition of two reference temperatures, Tl and 7’2, and the area through
which the density of heat flow rate is uniform.
Thermal resistance tan be related either to the material, structure or surface. If either 7j or T2 is not the
temperature of a solid surface, but that of a fluid, a reference temperature must be defined in each specific
case (with reference to free or forced convection and radiation from surrounding surfaces, etc.).
When quoting values of thermal resistance, Tl and T2 must be stated.
2 “Thermal resistance” should be replaced by “surface thermal resistance” when it may be confused with
“linear thermal resistance” (2.8).
2.8 *linear thermal resistance : ‘1 Temperature differente divided by the linear density of (rn- KVW
RI
heat flow rate in the steady state condition:
Tl - T2
R, =
NOTE - This assumes the definition of two reference temperatures, TI and Tz, and the length along which
the linear density of heat flow rate is uniform.
If within the System either Tl or T2 is not the temperature of a solid surface, but that of a fluid, a reference
temperature must be defined in each specific case (with reference to free or forced convection and radiation
from surrounding surfaces, etc.).
When quoting values of linear thermal resistance, Tl and T2 must be stated.
1) In ISO 31/4, “thermal resistance” is called “thermal insulance” or “coefficient of thermal insulation”, with the Symbol M.
ISO 7345 : 1987 (E)
Quantity
Unit
h
29 . surface coefficient of heat transfer: Density of heat flow rate at a surface in the steady W/(m2- K)
state divided by the temperature differente between that surface and the surroundings:
NOTE - This assumes the definition of the surface through which the heat is transferred, the temperature of
the surface, Ts, and the ambient temperature, Ta (with reference to free or forced convection and radiation
from surroundkg surfaces, etc.).
2.10 thermal conductance: Reciprocal of thermal resistance from surface to surface under
A W/(m2- K)
conditions of uniform density of heat flow rate:
AE----
R
“Thermal conductance” should be replaced by “surface thermal conductance” when it may be
NOTE -
confused with “linear thermal conductance” (2.11).
linear thermal conductance: Reciprocal of linear thermal resistance from surface to
2.11 W/(m-K)
sut-face under conditions of uniform linear density of heat flow rate:
A, = -
RI
2.12 thermal transmittance: Heat flow rate in the steady state divided by area and by the u W/(m2- K)
temperature differente between the surroundings on each side of a System:
Qb
u=
(T, - T2)A
This assumes the definition of the System, the two reference temperatures, Tl and Tz, and other
boundary conditions.
2 “Thermal transmittance” should be replaced by “surface thermal transmittance” when it may be con-
fused with “linear thermal transmittance” (2.13).
3 The reciprocal of the thermal transmittance is the total thermal resistance between the surroundings on
each side of the System.
2.13 linear thermal transmittance: Heat flow rate in the steady state divided by length and W/(m-K)
by the temperature differente between the surroundings on each side of a System:
u, =
(T, - Tz) I
This assumes the definition of the System, the two reference temperatures, Tl and T2, and other
boundary conditions.
2 The reciprocal of the linear thermal transmittance is the total linear thermal resistance between the sur-
roundings on each side of the System.
C
2.14 heat capacity: Quantity defined by the equation: J/K
NOTE - When the temperature of a System is increased by dTas a result of the addition of a small quantity
of heat dQ, the quantity dQldT is the heat capacity.
ISO 7345 : 1987 (E)
Quantity Unit
2.15 specific heat capacity: Heat capacity divided by mass. C J/kgmK)
2.15.1 specific heat capacity at constant pressure
J/kgmK)
cP
2.15.2 specific heat capacity at constant volume
J/kg-K)
2.16 *thermal diffusivity: Thermal conductivity d
...
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