prEN ISO 9288

Thermal insulation - Heat transfer by radiation - Physical quantities and definitions (ISO/DIS 9288:2021)

This document defines physical quantities and other terms in the field of thermal insulation relating to heat transfer by radiation.

Wärmeschutz - Wärmeübertragung durch Strahlung - Physikalische Größen und Definitionen (ISO/DIS 9288:2021)

Isolation thermique - Transfert de chaleur par rayonnement - Grandeurs physiques et définitions (ISO/DIS 9288:2021)

Le présent document définit des grandeurs physiques et d’autres termes du domaine de l’isolation thermique liés au transfert de chaleur par rayonnement.

Toplotna izolacija - Prenos toplote s sevanjem - Fizikalne količine in definicije (ISO/DIS 9288:2021)

General Information

• Status: Not Published
• ICS: 01.060 - Quantities and units
• ICS: 27.220 - Heat recovery. Thermal insulation
• Technical Committee: CEN/TC 89 - Thermal performance of buildings and building components
• Ref Project: oSIST prEN ISO 9288:2022 - Thermal insulation — Heat transfer by radiation — Physical quantities and definitions (ISO/DIS 9288:2021)

RELATIONS

• Revised: EN ISO 9288:1996 - Thermal insulation - Heat transfer by radiation - Physical quantities and definitions (ISO 9288:1989)
• Effective Date: 29-Sep-2021

Standards Content (sample)

SLOVENSKI STANDARD
oSIST prEN ISO 9288:2022
01-februar-2022

Toplotna izolacija - Prenos toplote s sevanjem - Fizikalne količine in definicije

(ISO/DIS 9288:2021)

Thermal insulation — Heat transfer by radiation — Physical quantities and definitions

(ISO/DIS 9288:2021)
Wärmeschutz - Wärmeübertragung durch Strahlung - Physikalische Größen und
Definitionen (ISO/DIS 9288:2021)

Isolation thermique — Transfert de chaleur par rayonnement — Grandeurs physiques et

définitions (ISO/DIS 9288:2021)
Ta slovenski standard je istoveten z: prEN ISO 9288
ICS:
01.060 Veličine in enote Quantities and units
27.220 Rekuperacija toplote. Heat recovery. Thermal
Toplotna izolacija insulation
91.120.10 Toplotna izolacija stavb Thermal insulation of
buildings
oSIST prEN ISO 9288:2022 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN ISO 9288:2022
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oSIST prEN ISO 9288:2022
DRAFT INTERNATIONAL STANDARD
ISO/DIS 9288
ISO/TC 163 Secretariat: SIS
Voting begins on: Voting terminates on:
2021-12-02 2022-02-24
Thermal insulation — Heat transfer by radiation —
Physical quantities and definitions

Isolation thermique — Transfert de chaleur par rayonnement — Grandeurs physiques et définitions

ICS: 01.060; 27.220
This document is circulated as received from the committee secretariat.
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENT AND APPROVAL. IT IS
ISO/CEN PARALLEL PROCESSING
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 9288:2021(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION. © ISO 2021
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oSIST prEN ISO 9288:2022
ISO/DIS 9288:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on

the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below

or ISO’s member body in the country of the requester.
ISO copyright office
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CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
© ISO 2021 – All rights reserved
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oSIST prEN ISO 9288:2022
ISO/DIS 9288:2021(E)
Contents

Foreword ................................................................................................................................................................ iv

Introduction ........................................................................................................................................................... v

1 Scope ................................................................................................................................................................. 1

2 Normative references ................................................................................................................................. 1

3 Terms and definitions ................................................................................................................................ 1

4 Terms related to surfaces either receiving, transferring or emitting a thermal radiation

...................................................................................................................................................................... 3

5 Terms related to surfaces emitting a thermal radiation ............................................................... 5

6 Terms related to opaque or semi-transparent surfaces receiving a thermal radiation .... 8

7 Terms related to a semi-transparent medium receiving a thermal radiation —

Combined conduction and radiation heat transfer ................................................................ 12

Bibliography ....................................................................................................................................................... 19

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oSIST prEN ISO 9288:2022
ISO/DIS 9288:2021(E)
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. Each 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, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO

collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see /www.iso.org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following

URL: www.iso.org/iso/foreword .html.

This document was prepared by Technical Committee ISO/TC 163, Thermal performance and energy use

in the built environment.

This second edition of ISO 9288 cancels and replaces the first edition (ISO 9288:1989), which has been

technically revised.

This edition includes the following significant changes with respect to the previous edition:

— title of ISO/TC 163 corrected (Foreword);
—delete the unit where two units existed;
—add the mean of d and d (7.15);
—add the formula numbers.
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Introduction

This document is intended to be used in conjunction with other vocabularies related to thermal insulation.

These include:

— ISO 7345, Thermal performance of buildings and building elements — Physical quantities and definitions

— ISO 9229, Thermal insulation — Vocabulary

— ISO 9251, Thermal insulation — Heat transfer conditions and properties of materials — Vocabulary

— ISO 9346, Hygrothermal performance of buildings and building materials — Physical quantities for mass

transfer — Vocabulary
© ISO 2021 – All rights reserved v
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oSIST prEN ISO 9288:2022
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Thermal insulation — Heat transfer by radiation — Physical
quantities and definitions
1 Scope

This document defines physical quantities and other terms in the field of thermal insulation relating to

heat transfer by radiation.
2 Normative references

The following standard contains provisions which, through reference in this text, constitute provisions

of this International Standard. At the time of publication, the edition indicated was valid. All standards

are subject to revision, and parties to agreements based on this International Standard are encouraged

to investigate the possibility of applying the most recent edition of the standard indicated below.

Members of IEC and ISO maintain registers of currently valid International Standards.

— ISO 7345, Thermal performance of buildings and building elements — Physical quantities and

definitions
3 Terms and definitions
3.1
thermal radiation

Electromagnetic radiation emitted at the surface of an opaque body or inside an element of a semi-

transparent volume.

The thermal radiation is governed by the temperature of the emitting body and its radiative

characteristics. It is interesting from a thermal viewpoint when the wavelength range falls between 0, l

μm and 100 μm (see figure 1).
2 1
-0.1μm ~ 100μm
-0.1μm ~ 3μm
4 3 2 1 0 -1 -2 -3
10 10 10 10 10 10 10 10
Wavelength(μm)
11 12 13 14 15 16 17
10 10 10 10 10 10 10
υ Frequency(s )
-0.7μm ~ 1000μm -0.14μm ~ 10 μm
-0.4μm ~ 0.7μm
3 4 5
Key
1— Solar radiation.
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2— Thermal radiation. 3—
Infrared.
4— Visible.
5— Ultraviolet.
Figure 1 — Electromagnetic wave spectrum
3.2
heat transfer by radiation

Energy exchanges between bodies (apart from one another) by means of electromagnetic waves.

These exchanges can occur when the bodies are separated from one another by vacuum or by a

transparent or a semi-transparent medium. To evaluate these radiation heat exchanges it is necessary to

know how opaque and semi-transparent bodies emit, absorb and transmit radiation as a function of their

nature, relative position and temperature.
3.3
Classification of the physical terms associated with thermal radiation

Physical terms associated with thermal radiation are classified according to two criteria:

— spectral distribution
— spatial distribution (directional) of the radiation.
These physical terms are:

total, if they are related to the entire spectrum of thermal radiation (this designation can be considered

as implicit);

spectral or monochromatic, if they are related to a spectral interval centred on the wavelength A;

hemispherical, if they are related to all directions along which a surface element can emit or receive

radiation;

directional, if they are related to the directions of propagation defined by a solid angle around the defined

direction.
3.4
Classification of materials in relation with radiative transfer

Opaque medium: Medium which does not transmit any fraction of the incident radiation.

The absorption, emission, reflection of radiation can be handled as surface phenomena.

Semi-transparent medium: Medium in which the incident radiation is progressively attenuated inside the

material by absorption or scattering, or both.

The absorption, scattering and emission of radiation are bulk (volume) phenomena.

The radiative properties of an opaque or semi-transparent medium are generally a function of the

spectral and directional distribution of incident radiation and of the temperature of the medium.

Note 1 to entry: Thermal insulating materials are generally semi-transparent media.

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4 Terms related to surfaces either receiving, transferring or emitting a thermal
radiation
4.1
radiant heat flow rate; radiant flux

Heat flow rate emitted, transferred or received by a system in form of electromagnetic waves.

Note 1 to entry: This is a total hemispherical quantity.
Note 2 to entry: Unit: W.
4.2
total intensity
Radiant heat flow rate divided by the solid angle around the direction 𝛥:
𝜕𝜙
𝐼 = (1)
𝜕𝛺
Note 1 to entry: Unit: W/sr.
4.3
total radiance

Radiant heat flow rate divided by the solid angle around the direction 𝛥 and the projected area normal to

this direction :
∂ Φ
𝐿 = (2)
∂Ω ∂(𝐴 cos 𝜃)
Note 1 to entry: Unit: W/(m ⋅ sr).
4.4
spectral radiant heat flow rate

Radiant heat flow rate divided by the spectral interval centred on the wavelength λ:

𝜕𝜙
𝜙 = (3)
𝜕𝜆
Note 1 to entry: Unit: W/m.
4.5
spectral intensity
𝛺𝜆
Total intensity divided by the spectral interval centred on the wavelength λ:
𝜕𝐼
𝐼 = (4)
Ω𝜆
𝜕𝜆
Note 1 to entry: Unit: W/(sr ⋅ m).
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4.6
spectral radiance
Total radiance divided by the spectral interval centred on the wavelength λ:
𝜕𝐿
𝐿 = (5)
𝛺𝜆
𝜕𝜆
( )
Note 1 to entry: Unit: W/ m ⋅ sr .
Note 2 to entry:

1 Each spectral term 𝐴 is related to the corresponding total term 𝐴 by a relation of the type

𝜕𝐴 ∞
𝐴 = 𝑜𝑟 𝐴 = 𝐴 𝑑𝜆 (6)
𝜆 𝜆
𝜕𝜆

Each directional term 𝐴 is related to the corresponding hemispherical term 𝐴 by a relation of the type

𝜕𝐴
𝐴 = 𝑜𝑟 𝐴 = 𝐴 𝑑Ω (7)
Ω Ω
Ω=4𝜋
𝜕Ω
And
𝜕 𝐴 ∞
𝐴 = 𝑜𝑟 𝐴 = ∫ ∫ 𝐴 𝑑λdΩ
Ωλ 𝛺𝜆
Ω=4𝜋 0
𝜕Ω𝜕𝜆
(8)

2 Total radiance and spectral radiance are oriented quantities (vectors) defined in each point of space where

radiation exists (see figure 3), moreover their values are independent of the particular surface used to define them.

Sources which radiate with constant 𝐿 (see 4.3) are called isotropic or diffuse.

Intensities are again oriented quantities but belong to a surface (see figure 2).

Radiant flows (total or spectral) are not oriented quantities and belong to a surface.

4.7
spectral radiant density of heat flow rate vector
𝑞⃗⃗⃗⃗⃗⃗⃗⃗
𝑟,𝜆
⃗⃗⃗
𝑞⃗⃗⃗⃗⃗⃗⃗⃗ = 𝐿 Δ 𝑑Ω (9)
𝑟,𝜆 Ωλ
Ω=4𝜋
Note 1 to entry: Unit: W/m .
4.8
total radiant density of heat flow rate vector
𝑞⃗⃗⃗⃗⃗
⃗⃗⃗
𝑞⃗⃗⃗⃗⃗ = 𝐿 Δ 𝑑Ωdλ (10)
∫ ∫
𝑟 Ωλ
0 Ω=4𝜋
Note 1 to entry: Unit: W/m .
4.9
spectral radiant density of heat flow rate(in the direction 𝒏⃗⃗⃗)
𝑟,𝜆𝑛
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𝑞 = 𝑛⃗⃗ ⋅ 𝑞⃗⃗⃗⃗⃗⃗⃗⃗ = ∫ 𝐿 𝛥 ⋅ 𝑛⃗⃗𝑑𝛺 (11)
𝑟,𝜆𝑛 𝑟,𝜆 𝛺𝜆
𝛺=4𝜋
Note 1 to entry: Unit: W/m .
4.10
forward component of the spectral radiant density of heat flow rate
𝑟,𝜆𝑛
𝑞 = 𝑛⃗⃗ ⋅ 𝑞⃗⃗⃗⃗⃗⃗⃗⃗ = 𝐿 𝛥 ⋅ 𝑛⃗⃗𝑑𝛺 (12)
𝑟,𝜆 𝛺𝜆
𝑟,𝜆𝑛
𝛺=2𝜋
Note 1 to entry: Unit: W/m .
4.11
backward component of the spectral radiant density of heat flow rate
𝑟,𝜆𝑛
𝑞 = 𝑛⃗⃗ ⋅ 𝑞⃗⃗⃗⃗⃗⃗⃗⃗ = − 𝐿 𝛥 ⋅ 𝑛⃗⃗𝑑𝛺 (13)
𝑟,𝜆𝑛 𝑟,𝜆 𝛺𝜆
𝛺=2𝜋
⃗⃗⃗
When Δ ⋅ 𝑛⃗⃗ < 0
( )
Note 1 to entry: Unit: W/ m .
Note 2 to entry:
1 We can express 𝑞 𝑏y the following expression:
𝑟,𝜆
+ −
𝑞 = 𝑞 − 𝑞 (14)
𝑟,𝜆 𝑟,𝜆 𝑟,𝜆
𝑛 𝑛 𝑛

2 In combined unidirectional conduction and radiation heat transfer along a direction 𝑛⃗⃗, we have

𝑞⃗⃗⃗⃗⃗ = 𝑞⃗⃗⃗⃗⃗⃗⃗⃗⃗⃗ + 𝑞⃗⃗⃗⃗⃗⃗⃗⃗ (15)
𝑛 𝑐𝑑,𝑛 𝑟,𝑛
where
𝑞⃗⃗⃗⃗⃗ is the density of heat flow rate as defined in ISO 7345: 2018, 3.1.3;
𝑞⃗⃗⃗⃗⃗⃗⃗⃗⃗⃗ is the density of heat flow rate by conduction;
𝑐𝑑,𝑛
𝑞⃗⃗⃗⃗⃗⃗⃗⃗⃗⃗ is the density of heat flow rate by conduction;
𝑐𝑑,𝑛
𝑞⃗⃗⃗⃗⃗⃗⃗⃗ is the total radiant density of heat flow rate vector;
𝑟,𝑛

𝑞⃗⃗⃗⃗⃗ can be determined experimentally with the guarded hot plate or heat flow meter method.

5 Terms related to surfaces emitting a thermal radiation
5.1
emission

Process in which heat (from molecular agitation in gases or atomic agitation in solids, etc.) is transformed

into electromagnetic waves.
5.2
total excitance
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Radiant heat flow rate emitted by a surface divided by the area of the emitting surface:

𝜕𝜙
+ −
𝑀 = = 𝑞 𝑜𝑟 𝑞 (16)
𝑟 𝑟
𝜕𝐴

Note 1 to entry: 𝑀 is the areal density of the heat flow rate in each point of an emitting surface. It is a total

hemispherical quantity.
Note 2 to entry: Unit: W/m .
5.3
spectral excitance
Total excitance divided by the spectral interval, centred on the wavelength 𝜆:
𝜕𝑀
+ −
𝑀 = = 𝑞 𝑜𝑟 𝑞 (17)
𝑟,𝜆 𝑟,𝜆
𝜕𝜆
Note 1 to entry: Unit: W/m .
5.4
black body (full radiator or Planck radiator)

The black body is one that absorbs all the incident radiation for all wavelengths, directions and

polarizations.

At a given temperature, for each wavelength it emits the maximum thermal energy (maximum spectral

excitance). For this reason and because rigorous laws define its emission, the emission of real bodies is

compared with that of the black body.
Note 1 to entry: Terms related to black body bear a superscript notation (°).
5.5
black body total excitance
It is expressed by the Stefan-Boltzmann law:
𝑜 4
𝑀 = 𝜎𝑇 (18)
Where
2 4
𝜎 is equal to 5,67 × 10 W (m ⋅ K );
𝑇 is the absolute temperature of the black body.
Note 1 to entry: Unit: W/m .
5.6
black body spectral excitance

It is expressed by Planck's law which relates 𝑀 to the wavelength 𝜆 and to the absolute temperature of

the black body:
𝐶 𝜆
𝑜 1
𝑀 = (19)
𝑒𝑥𝑝(𝐶 ⁄𝜆⋅𝑇)−1
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Where
2 16 2
𝐶 = 2𝜋ℎ𝑐 = 3,741 × 10 W m ;
1 0
𝐶 = ℎ 𝑐 𝑘 = 0,014 388 m ⋅ K.
2 0

ℎ and 𝑘 are, respectively, the Planck constant and the Boltzmann constant, 𝑐 is the speed of

electromagnetic waves in vacuum.
( )
A curve 𝑀 = f 𝜆 wi
...