SIST EN 62194:2006

SLOVENSKI SIST EN 62194:2006

STANDARD
februar 2006
Metoda vrednotenja toplotnih lastnosti ohišij (IEC 62194:2005)
Method of evaluating the thermal performance of enclosures (IEC 62194:2005)
ICS 31.240 Referenčna številka
SIST EN 62194:2006(en)
©  Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno

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EUROPEAN STANDARD EN 62194
NORME EUROPÉENNE
EUROPÄISCHE NORM October 2005

ICS 31.240


English version


Method of evaluating the thermal performance of enclosures
(IEC 62194:2005)


Méthode d'évaluation de la performance Verfahren zur Bewertung
thermique des enveloppes der Wärmeleistung von Gehäusen
(CEI 62194:2005) (IEC 62194:2005)






This European Standard was approved by CENELEC on 2005-09-01. CENELEC members are bound to
comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and
notified to the Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden,
Switzerland and United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Central Secretariat: rue de Stassart 35, B - 1050 Brussels


© 2005 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Ref. No. EN 62194:2005 E

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EN 62194:2005 - 2 -
Foreword
The text of document 48D/324/FDIS, future edition 1 of IEC 62194, prepared by SC 48D, Mechanical
structures for electronic equipment, of IEC TC 48, Electromechanical components and mechanical
structures for electronic equipment, was submitted to the IEC-CENELEC parallel vote and was
approved by CENELEC as EN 62194 on 2005-09-01.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2006-06-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2008-09-01
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 62194:2005 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standards indicated:
IEC 60297-2 NOTE Harmonized as HD 493.2 S1:1988 (not modified).
IEC 60721 NOTE Harmonized in EN 60721 series (not modified).
IEC 60917-2 NOTE Harmonized as EN 60917-2:1994 (not modified).
IEC 61587-1 NOTE Harmonized as EN 61587-1:1999 (not modified).
IEC 61969-1 NOTE Harmonized as EN 61969-1:2000 (not modified).
IEC 61969-2 NOTE Harmonized as EN 61969-2:2000 (not modified).
IEC 61969-3 NOTE Harmonized as EN 61969-3:2001 (not modified).
__________

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- 3 - EN 62194:2005
Annex ZA
(normative)

Normative references to international publications
with their corresponding European publications
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
NOTE Where an international publication has been modified by common modifications, indicated by (mod), the relevant
EN/HD applies.
Publication Year Title EN/HD Year
IEC 60297 Series Mechanical structures for electronic EN 60297 Series
equipment - Dimensions of mechanical
structures of the 482,6 mm (19 in) series

1) 2)
IEC 60721-2-4 - Classification of environmental conditions HD 478.2.4 S1 1989
Part 2: Environmental conditions
appearing in nature - Solar radiation and
temperature

IEC 60917 Series Modular order for the development of EN 60917 Series
mechanical structures for electronic
equipment practices

IEC 61969 Series Mechanical structures for electronic EN 61969 Series
equipment - Outdoor enclosures





1)
Undated reference.
2)
Valid edition at date of issue.

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NORME CEI
INTERNATIONALE
IEC



62194
INTERNATIONAL


Première édition
STANDARD

First edition

2005-08


Méthode d'évaluation de la performance
thermique des enveloppes

Method of evaluating the thermal
performance of enclosures

 IEC 2005 Droits de reproduction réservés  Copyright - all rights reserved
Aucune partie de cette publication ne peut être reproduite ni No part of this publication may be reproduced or utilized in any
utilisée sous quelque forme que ce soit et par aucun procédé, form or by any means, electronic or mechanical, including
électronique ou mécanique, y compris la photocopie et les photocopying and microfilm, without permission in writing from
microfilms, sans l'accord écrit de l'éditeur. the publisher.
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch Web: www.iec.ch
CODE PRIX
V
PRICE CODE
Commission Electrotechnique Internationale
International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
Pour prix, voir catalogue en vigueur
For price, see current catalogue

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62194 ¤ IEC:2005 – 3 –
CONTENTS
FOREWORD.7
INTRODUCTION . 11
1 Scope. 13
2 Normative references. 13
3 Terms, definitions, symbols and abbreviations. 15
3.1 Definition of enclosure design principles. 15
3.2 Symbols and abbreviated terms. 15
4 Flow chart for establishing the absorption factor . 19
5 Evaluation of the heat load . 21
6 Environmental conditions. 21
6.1 Outdoor applications . 21
6.2 Indoor applications. 23
7 Determination of the enclosure absorption factor . 23
7.1 Measurement set-up. 23
7.2 Calculation . 27
8 Result and presentation . 27
8.1 Comparison of different enclosure designs . 27
8.2 Heat transfer through walls . 29
8.3 Airflow between walls . 31
8.4 Results for single-wall enclosures. 33
8.5 Results for double-wall enclosures (simple method). 35
Annex A (normative) Heat transfer rate. 39
Annex B (informative) Geometric relations for solar radiation . 41
Annex C (informative) Example for single and double wall calculation. 45
Annex D (informative) Iteration method for exact results of a double wall enclosure . 49
Bibliography. 61
Figure 1 – Enclosure types. 15
Figure 2 – Flow chart for establishing the absorption factor. 19
Figure 3 – Example of measurement set-up for enclosure absorption factor. 25
Figure 4 – Heat transfer through walls . 29
Figure 5 – Airflow between walls . 33
Figure B.1 – Geometric angles for solar radiation impact . 41
Figure D.1 – Thermal model for double wall enclosure. 49
Figure D.2 – Iteration procedure for double-wall enclosures. 53

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62194 ¤ IEC:2005 – 5 –
Table 1 – Convection heat transfer coefficients. 23
Table 2 – Parameters for single-wall enclosure calculation . 35
Table 3 – Parameters for double-wall enclosure calculation (simple method) . 37
Table C.1 – Given parameters for single-wall enclosure calculation . 45
Table C.2 – Given parameters for double-wall enclosure calculation (simple method). 47
Table D.1 – Given parameters for double wall enclosure calculation . 57
Table D.2 – Starting values for iterations . 57
Table D.3 – Results after first iteration block . 57
Table D.4 – Results after second iteration block . 59

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62194 ¤ IEC:2005 – 7 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
METHOD OF EVALUATING THE THERMAL
PERFORMANCE OF ENCLOSURES
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 62194 has been prepared by subcommittee 48D: Mechanical
structures for electronic equipment, of IEC technical committee 48: Electromechanical
components and mechanical structures for electronic equipment.
The text of this standard is based on the following documents:
FDIS Report on voting
48D/324/FDIS 48D/328/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

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62194 ¤ IEC:2005 – 9 –
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in
the data related to the specific publication. At this date, the publication will be
reconfirmed;
withdrawn;
replaced by a revised edition, or
amended.

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62194 ¤ IEC:2005 – 11 –
INTRODUCTION
When installing enclosures with electronic components, the climatic conditions are very
important, as the function of the electronics is affected by the ambient temperature. Because
of heat load and solar radiation, the enclosures become hot. Since the heat transfer via the
enclosure surface is often not sufficient, a climate control unit may be required to maintain
tolerable enclosure internal conditions. For the enclosure design, the effect of the solar
radiation was either estimated via the solar constant or added with a fixed value for heat load.
Closer observation of the radiation allows for a more accurate and cost-efficient method of
enclosure thermal performance evaluation.
There are existing standards defining the environmental conditions: for outdoor enclosures,
IEC 61969-3 and EN 300 019 and, for indoor enclosures, IEC 60721, EN 300 019, and
IEC 61587-1.
Dimensional standards referred to for outdoor enclosures are IEC 61969-1 and IEC 61969-2,
and, for indoor enclosures, IEC 60297-2, EN 300 119 and IEC 60917-2.
As requested by users and manufacturers, a unified heat management property of empty
enclosures had to be developed. This standard establishes a method of thermal performance
evaluation for enclosures.

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62194 ¤ IEC:2005 – 13 –
METHOD OF EVALUATING THE THERMAL
PERFORMANCE OF ENCLOSURES
1 Scope
This International Standard provides a method of thermal performance evaluation for empty
indoor enclosures according to IEC 60917 and IEC 60297, and, for outdoor enclosures
according to IEC 61969.
This standard contains criteria to determine the thermal absorption factors relating to
– principles of enclosure design;
– internal heat load;
– sun radiation.
The enclosure absorption factor is intended to provide a common value for comparing and
selecting enclosures built in accordance with this standard.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
IEC 60297 (all parts), Dimensions of mechanical structures of the 482,6 mm (19 in) series
IEC 60721-2-4, Classification of environmental conditions – Part 2-4: Environmental condi-
tions appearing in nature  Solar radiation and temperature
IEC 60917 (all parts), Modular order for the development of mechanical structures for
electronic equipment practices
IEC 61969 (all parts), Mechanical structures for electronic equipment – Outdoor enclosures

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62194 ¤ IEC:2005 – 15 –
3 Terms, definitions, symbols and abbreviations
3.1 Definition of enclosure design principles
The enclosure design influences heat flow. The following enclosure types are defined and
illustrated in Figure 1.
A Single-wall
B Double-wall (with insulation/without insulation/with or without airflow)
C Single-wall and sun-shield
D Double-wall and sun-shield (with insulation/without insulation/with or without airflow)
A
C, D
B
IEC  1258/05
Figure 1 – Enclosure types
3.2 Symbols and abbreviated terms
2
A Area of the surfaces of the enclosure excluding the bottom in square metres (m )
A Material absorption factor
A Enclosure absorption factor
E
2
A Cross-section of the double wall in square metres (m )
W
a Wall azimuth angle
w
a Sun azimuth angle
0
c Corrective factor for double-wall calculation (simple method)
F
c Specific heat capacity of air in joules per kilogram and per kelvin (J/(kg K))
p,air
h Sun-height angle
2
k Heat transfer rate in watts per square meter and per kelvin (W/(m K))
P Heat load in watts (W)

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62194 ¤ IEC:2005 – 17 –

Q Heat transfer through enclosure walls caused by transmission in watts (W)
Tr

Q Heat transfer transported by the airflow between the double wall in watts (W)
vent
2

q Diffuse solar radiation in watts per square metre (W/m )
dif

q
Solar radiation received on horizontal surfaces in watts per square metre (global
g
2
radiation) (W/m )
2

q Specific internal heat load in watts per square metre (W/m )
i

q Solar total radiation received through the atmosphere in watts per square metre
s
2
(W/m ) (normal direction to the sun)

q Solar radiation (direct and diffuse) on the enclosure wall in watts per square metre
w
2
(W/m )
s Material thickness of material j used for the wall in metres (m)
j
T Ambient air temperature in kelvins (K)
A
T Wall temperature on the outside of the enclosure in kelvins (K)
W
t Ambient temperature in degrees Celsius (°C)
a
t Maximum ambient temperature in degrees Celsius (°C)
a,max
t Average temperature inside the enclosure in degrees Celsius (°C)
i
t Maximum allowed temperature inside the enclosure in degrees Celsius (°C)
i,max
t Air temperature between the double wall in degrees Celsius (°C)
m
t Wall temperature on the outside of the enclosure in degrees Celsius (°C)
w
t Wall temperature of the interior wall of a double-wall enclosure in degrees Celsius (°C)
wi
w Wind speed in metres per second (m/s)
w Air speed between the double wall in metres per second (m/s)
w
D Convection heat transfer coefficient outside in watts per square metre and per kelvin
ka
2
(W/(m K))
D Convection heat transfer coefficient inside in watts per square metre and per kelvin
ki
2
(W/(m K))
2
D Radiation heat transfer coefficient in watts per square metre and per kelvin (W/(m K))
rad
H Emissivity of the enclosure surface treatment
T Incident angle
O Thermal conductivity of material j used for the wall in watts per metre and per kelvin
j
(W/(m K))
3
U Density of air in kilograms per cubic metre (kg/m )
air

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62194 ¤ IEC:2005 – 19 –
4 Flow chart for establishing the absorption factor
The flow chart shown in Figure 2 describes the different steps that are necessary for the
determination of the thermal performance of the enclosure. The details of the different steps
are explained in the clauses following this chart.
Evaluation of the heat load
(see Clause 5)
Definition of the environmental conditions
(see Clause 6)
Outdoor application: Indoor application:
x Maximum ambient x Maximum ambient
  temperature   temperature
x Thermal criteria x  Thermal criteria
x Solar radiation
x Wind
Enclosure
NO
absorption
factor
known?
Determination of the enclosure
YES
absorption factor
(see Clause 7)
Result and presentation
(see Clause 8)
IEC  1259/05
Figure 2 – Flow chart for establishing the absorption factor

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62194 ¤ IEC:2005 – 21 –
5 Evaluation of the heat load
For thermal performance it is important to understand the heat load in the interior of the
enclosure. If the heat load of the installed components is unknown, the power consumption of
the installed equipment can be used for estimating the internal heat load.
P heat load in watts (W);
P
2

q specific internal heat load in watts per square metre (W/m ).
i
A
6 Environmental conditions
6.1 Outdoor applications
6.1.1 Ambient temperature limits
Understanding the ambient temperature limits is necessary for the following calculations:
t maximum ambient temperature in degrees Celsius (°C);
a,max
t maximum allowed temperature inside the enclosure in degrees Celsius (°C).
i,max
6.1.2 Solar radiation
2

The solar total radiation is indicated in W/m . It is dependent on the enclosure installation
q
s
site, the time of the day, the time of the year and on the turbidity coefficient of the
atmosphere. The Angstrom turbidity coefficient expresses the scattering and absorption of the
aerosol particles in the atmosphere. For further details, refer to IEC 60721-2-4.
The total solar radiation is composed of direct and diffused radiation. The following describes
different methods to determine the solar radiation for an enclosure by
a) measuring the solar total radiation when falling perpendicularly to one of the individual
surfaces of the enclosure;
b) measuring the global radiation at the installation site. The resulting quantity shall be
converted to the individual surfaces of the enclosure. This can be accomplished by using
the geometric relations as presented in Annex B using formula (B.2);
c) using meteorological tables. The radiation that falls perpendicularly on the enclosure
surfaces shall be determined.
The method by which the solar radiation was determined shall be established.
6.1.3 Wind
The wind speed and ambient air temperature present have an influence on the heat transfer
to the surfaces of the enclosure. If no general formula is used to determine the convection
heat transfer coefficients for outside D and inside D of the enclosure, the values indicated
ka ki
in Table 1 can be used. These values are dependent on the wind speed.

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62194 ¤ IEC:2005 – 23 –
Table 1 – Convection heat transfer coefficients
Wind speed w in m/s 0,3 0,5 1 3 5 10 20
Heat transfer coefficients
2
 outside D in W/(m K)
ka
3,3 4,5 7 15 25 38 66
2
D
 inside in W/(m K)
ki
Since the components in the enclosure may have integrated fans installed, forced air-flow is
present inside the enclosure and exceeds natural convection. If the internal airflow is known,
the values of Table 1 should be used. Otherwise, the air speed is assumed to be 1 m/s and
the convection heat transfer coefficient inside D is calculated as follows:
ki
W
D 7
ki
2
m ˜ K
6.2 Indoor applications
Ambient temperature limits for indoor application:
t maximum ambient temperature in degrees Celsius (°C);
a,max
t maximum allowed temperature inside the enclosure in degrees Celsius (°C).
i,max
7 Determination of the enclosure absorption factor
7.1 Measurement set-up
The test set-up shown in Figure 3 shall measure the enclosure absorption factor which is
acquired by measuring the largest wall. This wall has to face the South in the Northern
hemisphere and the North in the Southern hemisphere. The temperature sensor a) shall be
placed in the centre of the measured wall. A heat source shall be installed inside the
2

enclosure to simulate heat load. The heat load is chosen corresponding to q of 250 W/m .
i

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62194 ¤ IEC:2005 – 25 –
Sun
  b) Wind speed sensor
  c) Solar radiation sensor
a) Temperature sensor t
w
  d) Temperature sensor t
a
Data logger and evaluation
IEC  1260/05
Figure 3 – Example of measurement set-up for enclosure absorption factor
At steady state, the following values shall be determined:

q solar radiation (direct and diffuse) on the enclosure wall in watts per square metre
w
2
(W/m );
t ambient air temperature in degrees Celsius (°C);
a
t wall temperature on the outside of the enclosure in degrees Celsius (°C);
w
w wind speed in metres per second (m/s).
The sensors b), c) and d) shall be attached in such a way that retroactive effects of the test
specimen to the sensors are avoided.

NOTE If the global radiation q is measured, it should be converted according to Annex B using formula (B.2),
g
radiation falling perpendicularly to the wall.

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62194 ¤ IEC:2005 – 27 –
7.2 Calculation
The enclosure absorption factor is to be calculated according to

D D ˜ T  T
ka rad W A
A (1)
E
 
q  q
i w
4 4
T T
§ W · § A ·

¨ ¸ ¨ ¸
100 100
ª W º
© ¹ © ¹
˞ 5,67˜ (2)
rad « »
2
T  T
W A ¬ m ˜K¼
where
2

q is the specific internal heat load, according to 7.1, in watts per square metre (W/m )
i
(for definition, see Clause 5);

q is the solar radiation (direct and diffuse) on the enclosure wall in watts per square
w
2
meter (W/m );
T is the ambient air temperature in kelvins (K);
A
T is the wall temperature on the outside of the enclosure in kelvins (K);
W
D is the convection heat transfer coefficient outside according to Clause 6 in watts per
ka
2
square meter and per kelvin (W/(m K));
D is the radiation heat transfer coefficient in watts per square metre and per kelvin
rad
2
(W/(m K)).
If the absorption factor is determined according to formula (1), all parameters used for
conversion shall be recorded. The relevant environmental conditions are defined and may be
converted if different environmental conditions apply.
NOTE 1 New measurements are necessary when the colour of the enclosure is changed, the enclosure
absorption factor being influenced by surface colours.
NOTE 2 The reflection of the solar radiation and the emissivity H of the enclosure surface are implicitly included in
formula (1) as a result of the measurement set-up of 7.1.
NOTE 3 Temperatures indicated in degrees Celsius (°C) can be converted into kelvins (K) by means of the
following formula:
K
T 273,15 K  t ˜
K C
qC
8 Result and presentation
8.1 Comparison of different enclosure designs
Different enclosure designs can be compared by using the enclosure absorption factor
according to Clause 7. The enclosure absorption factor also contains information to evaluate
average internal temperature of the enclosure. Details are shown in 8.4 and 8.5.
A lower value for A indicates a good thermal performance of the enclosure regarding impact
E
from solar radiation. The inside temperature can be expected lower.
A higher value for A indicates the opposite.
E

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62194 ¤ IEC:2005 – 29 –
Example:
Measurements according to Clause 7 of different enclosure designs with the same
dimensions, materials and surface treatments will result in the following enclosure absorption
factors:
a) single-wall enclosure A = 0,61
E,1
b) double-wall enclosure (without insulation and without ventilation) A = 0,73
E,2
c) double-wall enclosure (with ventilation between double wall) A = 0,36
E,3
d) single-wall enclosure with sun shield A = 0,44
E,4
Result:
At A < A < A < A the inside temperatures of the different enclosures will be the same
E,3 E,4 E,1 E,2
t < t < t < t at the same solar load and same heat load.
i,3 i,4 i,1 i,2
8.2 Heat transfer through walls
For single-wall enclosures, the heat transfer through the walls shall be determined by
formula (3):

Q = k˜A˜(t -t ) (3)
Tr a i
...