# ISO 14505-4:2021

(Main)## Ergonomics of the thermal environment — Evaluation of thermal environments in vehicles — Part 4: Determination of the equivalent temperature by means of a numerical manikin

## Ergonomics of the thermal environment — Evaluation of thermal environments in vehicles — Part 4: Determination of the equivalent temperature by means of a numerical manikin

This document provides guidelines for extending the definition of equivalent temperature to predictive purposes and specifies a standard prediction method for the assessment of thermal comfort in vehicles using numerical calculations. Specifically, this document sets forth a simulated numerical manikin as a viable alternative to the thermal manikin for the purpose of calculating the equivalent temperature.

## Ergonomie des ambiances thermiques — Évaluation des ambiances thermiques dans les véhicules — Partie 4: Détermination de la température équivalente à l'aide d'un mannequin numérique

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INTERNATIONAL ISO

STANDARD 14505-4

First edition

2021-09

Ergonomics of the thermal

environment — Evaluation of thermal

environments in vehicles —

Part 4:

Determination of the equivalent

temperature by means of a numerical

manikin

Ergonomie des ambiances thermiques — Évaluation des ambiances

thermiques dans les véhicules —

Partie 4: Détermination de la température équivalente à l'aide d'un

mannequin numérique

Reference number

ISO 14505-4:2021(E)

©

ISO 2021

---------------------- Page: 1 ----------------------

ISO 14505-4:2021(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

CP 401 • Ch. de Blandonnet 8

CH-1214 Vernier, Geneva

Phone: +41 22 749 01 11

Email: copyright@iso.org

Website: www.iso.org

Published in Switzerland

ii © ISO 2021 – All rights reserved

---------------------- Page: 2 ----------------------

ISO 14505-4:2021(E)

Contents Page

Foreword .iv

Introduction .v

1 Scope . 1

2 Normative references . 1

3 Terms and definitions . 1

4 Symbols . 2

5 Assessment of thermal en vironments in vehicles . 4

6 Principles of assessment utilizing a numerical manikin . 4

7 Calculation method coupled with numerical manikin . 5

7.1 General . 5

7.2 Flow and thermal field around manikin . 6

7.2.1 Convective heat . 6

7.2.2 Radiant heat . 7

7.2.3 Conductive heat . 7

7.3 Calculation of heat exchange on manikin. 7

7.3.1 Structure and control of numerical manikin . 7

7.3.2 Calculation of heat exchange . 9

7.4 Calculation of h .

cal 9

7.5 Calculation outputs . 9

8 Calculation method using thermal factors .10

8.1 General .10

8.2 Flow and thermal field around manikin .10

8.2.1 Convective heat .10

8.2.2 Radiant heat .10

8.2.3 Conductive heat .11

8.3 Calculation of heat exchange .11

8.4 Calculation of h .

cal 11

8.5 Calculation outputs .11

8.5.1 General.11

8.5.2 Constant temperature mode .11

8.5.3 Constant heat flux mode.12

8.5.4 Comfort equation mode .12

Annex A (informative) Calculation via computational fluid dynamics (CFD) technique .13

Annex B (informative) Typical inputs and outputs of calculation with numerical manikin .16

Annex C (informative) Treatment of radiant heat transfer .22

Annex D (informative) Typical inputs and outputs of calculations using thermal factors .24

Annex E (informative) Calculation method of h .27

cal

Annex F (informative) Development of formulae for equivalent temperature calculations

using thermal factors .37

Bibliography .43

© ISO 2021 – All rights reserved iii

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ISO 14505-4:2021(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 of 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 www .iso .org/

iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 159, Ergonomics, Subcommittee SC 5,

Ergonomics of the physical environment.

A list of all parts in the ISO 14505 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.

iv © ISO 2021 – All rights reserved

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ISO 14505-4:2021(E)

Introduction

The interaction of convective, radiant and conductive heat exchange in a vehicle compartment or similar

confined space is highly complex. External thermal loads in combination with the air conditioning

system in a vehicle compartment create non-uniform thermal environments, which are often the

main cause of complaints of thermal discomfort. In vehicles with poor or non-existent air conditioning

systems, non-uniform thermal environments can also be created by the interaction between the

ambient climatic conditions and vehicle structures. While a subjective evaluation reflects the total

sensations of a human body, these often incur great costs while the study phase is being conducted.

Physical measurements provide detailed and accurate local information; however, these results must be

integrated in some way to predict the thermal effects on humans. Furthermore, since specific climatic

factors sometimes play a dominant role in the overall heat exchange of a human body, an evaluation

method that accounts for the relative importance of these factors is required.

This document is part of the ISO 14505 series. To meet the above-stated requirements, this document

provides calculation methods that utilize numerical simulations to assess the total thermal environment

of vehicles. The equivalent temperature, obtained from measurements taken using a thermal manikin,

is defined in ISO 14505-2. This document extends the definition of the ISO 14505 series to include

numerical evaluation when this document is used in conjunction with the equivalent temperature

defined in ISO 14505-2.

As described in ISO 14505-2, an equivalent temperature can be utilized in the assessment of vehicle

cabins and other various enclosed spaces with non-uniform environments. As is the case for

ISO 14505-2, this document can also be applied to vehicle cabins and other enclosed spaces.

This document supposes that the ISO 14505 series will be applied to various situations, such as:

— in the case of experimental facilities that are not prepared;

— in the case of prototypes that are incomplete;

— in the case of conditions that are difficult to simulate in controlled experimental settings;

— in the case that occupants are extrapolated to unknown or virtual environments.

© ISO 2021 – All rights reserved v

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INTERNATIONAL STANDARD ISO 14505-4:2021(E)

Ergonomics of the thermal environment — Evaluation of

thermal environments in vehicles —

Part 4:

Determination of the equivalent temperature by means of

a numerical manikin

1 Scope

This document provides guidelines for extending the definition of equivalent temperature to predictive

purposes and specifies a standard prediction method for the assessment of thermal comfort in vehicles

using numerical calculations. Specifically, this document sets forth a simulated numerical manikin as

a viable alternative to the thermal manikin for the purpose of calculating the equivalent temperature.

2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements 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.

ISO 13731, Ergonomics of the thermal environment — Vocabulary and symbols

ISO 14505-2, Ergonomics of the thermal environment — Evaluation of thermal environments in vehicles —

Part 2: Determination of equivalent temperature

3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 13731 and ISO 14505-2 and

the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp

— IEC Electropedia: available at http:// www .electropedia .org/

3.1

numerical manikin

virtual thermal manikin recreating a thermal manikin, or a digital model of a thermal manikin used to

calculate performance

3.2

physical manikin

real thermal manikin to measure real environment

3.3

computational fluid dynamics

CFD

simulation of a series of calculations based on specific boundary conditions and specific parameters

associated with fluid and thermal fields using discrete equations based on the Navier-Stokes/Lattice-

Boltzmann equations as well as heat transfer equations that consider convection, radiation and

conduction, and generally account for the effects of turbulent flow

© ISO 2021 – All rights reserved 1

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ISO 14505-4:2021(E)

4 Symbols

A complete list of symbols used in this document is presented in Table 1.

Table 1 — Symbols and units

Symbol Term Unit

α Solar absorptivity on clothing (skin on unclothed area) surface –

2

A Skin surface area m

2

C Convective heat loss from clothing (skin on unclothed area) surface W/m °C

f Area factor (ratio of clothed to nude area) –

cl

2

h Convective heat transfer coefficient W/m °C

c

2

h Total heat transfer coefficient in a standard environment W/m °C

cal

2

h Convective heat transfer coefficient in a standard environment W/m °C

cs

2

h Radiant heat transfer coefficient W/m °C

r

2

h Radiant heat transfer coefficient in a standard environment W/m °C

rs

2

I Thermal insulation of clothing m °C/W

cl

2

Q Total heat loss from skin surface W/m

2

Q Set value of Q at constant heat flux mode W/m

set

2

R Radiant heat loss from clothing (skin on unclothed area) surface, including effect of W/m

solar radiation

2

R Thermal insulation between core and skin assumed by comfort equation m °C/W

cr

2

R Total thermal resistance between the manikin skin surface and the environment m °C/W

t

2

S Mean solar radiation reached on clothing (skin on unclothed area) surface W/m

t Air temperature °C

a

t Air temperature at h calculation °C

aset cal

t Clothing (skin on unclothed area) surface temperature °C

cl

t Core temperature assumed by the comfort equation °C

cr

t Equivalent temperature °C

eq

t Operative temperature including the effects of solar radiation °C

o

t Mean radiant temperature °C

r

t Skin surface temperature °C

sk

t Set value of t at constant temperature mode °C

skset sk

v Air velocity m/s

a

Suffix: segment number of each body part –

n

Suffix: whole body –

whole

Symbols used in Annex E

2

A Body surface area of the manikin m

b

2

A Elemental surface area of the element i

m

ei,

2

Segmental surface area of the segment n

A m

n

B

Absorption factor of radiation from surface elements i to j –

ij,

F View factor of radiation from surface elements i to j

–

ij,

2

Total heat transfer coefficient of segment n for calibration

h

W/m K

caln,

2

h Total heat transfer coefficient of the entire manikin for calibration W/m K

calw, hole

ij, –

Variable body surface element number

2 © ISO 2021 – All rights reserved

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ISO 14505-4:2021(E)

Table 1 (continued)

Symbol Term Unit

–

Variable spatial volume element number for calculation of t

a

k

Variable body surface element number in the recurrence equation of B

ij,

m Number of body surface elements –

b

End body surface element number of segment n –

m

en,

m Start body surface element number of segment n –

sn,

–

m Number of spatial volume elements

v

m Number of wall surface elements –

w

n

Variable local segment number of the manikin –

–

n

Number of manikin segments

seg

2

Q

Heat flux of element i W/m

ei,

2

Averaged heat flux over segment n

Q W/m

n

2

Q Averaged heat flux over the entire manikin W/m

whole

2

R Thermal insulation between core and skin assumed by comfort equation m K/W

cr

2

R

Thermal insulation of element i for the comfort equation mode calculation m K/W

cr,,ei

T Averaged air temperature in the standard chamber (in Kelvins) K

a

t Averaged air temperature in the standard chamber (in Celsius) °C

a

t °C

Air temperature of the spatial volume element k

ae,,k

t

Air temperature entering the standard chamber °C

ai, n

t Core temperature assumed by the comfort equation °C

cr

t

Core temperature of element i for the comfort equation mode calculation °C

cr,,ei

t Operative temperature in the standard chamber °C

o

T Mean radiant temperature of the wall of the standard chamber (in Kelvins) K

r

t Mean radiant temperature of the wall of the standard chamber (in Celsius) °C

r

t Skin surface temperature of the manikin °C

sk

Averaged skin surface temperature of segment n

t °C

sk,n

Estimated average skin surface temperature of the segment n from the comfort

t′

°C

sk,n

equation

t

Averaged skin surface temperature of the entire manikin °C

sk,whole

T Wall surface temperature of the standard chamber (in Kelvins) K

w

t Wall surface temperature of the standard chamber (in Celsius) °C

w

u Air flow velocity in the standard chamber m/s

a

3

V Volumetric air flow rate entering the standard chamber m /s

ai, n

3

V Volume of the spatial volume element k m

ek,

3

V Volume of the spatial region in the standard chamber m

0

2

Correction amount for generated heat of segment n

ΔQ W/m

n

Threshold of difference between t′ and t for iterative convergence

Δt °C

ce sk,n sk,n

Δt Threshold of difference between t and t for iterative convergence °C

o a r

ε –

Emissivity of the surface element j

j

–

ε Emissivity of the manikin

sk

ε Emissivity of the wall of the standard chamber –

w

© ISO 2021 – All rights reserved 3

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ISO 14505-4:2021(E)

Table 1 (continued)

Symbol Term Unit

Conversion factor between the actual wall surface temperature and mean radiant –

ξ

m

temperatures

5 Assessment of thermal en vironments in vehicles

The method of assessment by equivalent temperature is defined in ISO 14505-2. The assessment

procedures in ISO 14505-2 are applicable to numerical evaluations, for which “numerical manikin” is

defined in this document. Figure 1 shows the role of this document and its relations with the other

parts of the ISO 14505 series as well as different International Standards.

Figure 1 — Role of numerical evaluation among different International Standards

6 Principles of assessment utilizing a numerical manikin

This document presents two methods for calculating the equivalent temperature. One is a calculation

method coupled with a numerical manikin, as described in Clause 7. The other is a calculation method

using thermal factors, as described in Clause 8. Either method can be used to evaluate the thermal

environment in vehicles.

The former calculation method coupled with a numerical manikin is intended for use with a simulation

tool, such as computational fluid dynamics (CFD). A numerical manikin imitates a physical manikin

to calculate the equivalent temperature. The method of calculation using thermal factors estimates

the equivalent temperature by assuming the existence of the imaginary numerical manikin. In this

method, the equivalent temperature is calculated using the thermal factors, air temperature, radiant

temperature, air velocity and solar radiation. Figure 2 shows a schematic of the two methods.

4 © ISO 2021 – All rights reserved

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ISO 14505-4:2021(E)

Figure 2 — Two methods for calculating equivalent temperature

7 Calculation method coupled with numerical manikin

7.1 General

This clause describes the framework of the calculation. To evaluate the indoor environment of a vehicle

numerically, the following issues should be considered and taken account (see Figure 3):

a) heat flow through the shell structure of the vehicle;

b) flow and thermal field in the cabin;

c) radiant field (including solar radiation) in the cabin;

d) conductive heat exchange;

e) heat balance of the thermal manikin model (numerical manikin).

This document is intended to be applied to the region around the manikin, relating to items b) and e).

The heat flow through the structure of the vehicle body is defined as suitable. This document defines

indispensable ideas concerning the above items, which will enable successful and useful calculations in

these situations. However, this document does not define any specific methods for utilization because

all methods present both advantages and disadvantages for particular problems.

Once the environmental state concerning thermal comfort in the cabin is calculated, evaluation

becomes possible. Items a) to d) give the principal local parameters of air velocity, temperature and

radiation, though some simultaneous calculation coupling with the heat balance calculation is required.

This calculation will produce a heat transfer value close to that measured using the physical manikin.

Therefore, the evaluation method described in ISO 14505-2 is applicable.

© ISO 2021 – All rights reserved 5

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ISO 14505-4:2021(E)

Key

1 outside of vehicle 5 convection

2 shell structure 6 radiation

3 interior of vehicle 7 conduction

4 thermal manikin

a

Other standards (TC22 related).

b

This document.

NOTE Evaluation of the area in contact with the seat is outside the scope of this document.

Figure 3 — Framework of heat transfer system

7.2 Flow and thermal field around manikin

7.2.1 Convective heat

The flow and thermal field in the cabin are estimated via calculations. One practical option for this is

CFD. The informative concrete contents of this method are represented in Annex A. The outputs are

the air velocity vector and air temperature in a cabin. The heat flux on the wall and surface are also

obtained through this calculation.

The primary problem in CFD calculations is the treatment of boundary conditions. This can be overcome

in practice by selecting any of the following:

a) Calculate the heat transfer on the surface of the manikin using CFD directly.

b) As a preliminary, calculate the heat transfer coefficient on the surface of the manikin using CFD.

Then calculate the flow and thermal field coupling using the heat balance calculation of the manikin.

c) Utilize the heat transfer coefficient obtained by measurement. Then calculate the flow and thermal

field coupling with the heat balance calculation of the manikin, as described in b).

d) Estimate the heat transfer coefficient using a predictive formula based on the air velocity or

temperature. Then calculate the flow and thermal field coupling using the heat balance calculation

for the manikin, as described in b).

6 © ISO 2021 – All rights reserved

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ISO 14505-4:2021(E)

7.2.2 Radiant heat

The radiant field is calculated based on the geometric condition in a cabin separated from the flow field

calculation. Regarding long-wave radiation, as a preliminary, the view factor relating to all potential

combinations between different surface elements of the wall and the manikin or human body should

be calculated. Once those factors have been obtained, the radiant heat exchange is calculated when the

temperature of a pair of surface elements is given. As stated previously, the radiant heat is involved in

the boundary conditions of the heat transfer equation, so that the temperature is calculated iteratively

until convergence. For convenience, those factors are converted to the mean radiant heat transfer

coefficient.

Short-wave radiation (solar radiation) can be treated as energy flux striking the surface. Here, the

transmission loss through the window glass should be taken into consideration. Solar radiation can be

regarded as divided into the following components:

a) direct solar radiation;

b) sky solar radiation;

c) reflection on the ground.

The solar radiant heat is also involved in the boundary conditions of the heat transfer equation. In the

case of a climate wind tunnel test performed without use of a solar lamp, it is supposed that the effects

of solar radiation are neglected. Concrete informative treatments are represented in Annex C.

7.2.3 Conductive heat

Evaluation of the contacted segment is outside the scope of this document. The conductive heat transfer

between the manikin and seat is disregarded in the calculations.

7.3 Calculation of heat exchange on manikin

7.3.1 Structure and control of numerical manikin

Figure 4 shows the theoretical structure of the numerical manikin with regard to a human-shaped one.

The centre of each segment is assumed to consist of an adiabatic core. A heat generator is equipped on

the surface of the manikin.

The shape of the manikin is defined by calculation grids for CFD, as shown in Figure 5 a). The partition

is performed to imitate an actual manikin, as in Figure 5 b). Boundary conditions are given for each

segment.

© ISO 2021 – All rights reserved 7

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ISO 14505-4:2021(E)

Key

1 adiabatic core

2 heat generator on surface

Figure 4 — Theoretical structure of numerical manikin

a) Full-body model of manikin b) Partition of surface grids (16-segment case

shown)

Key

1 head 6 forearm

2 chest 7 hand

3 back 8 thigh

4 pelvis 9 leg

5 upper arm 10 foot

Figure 5 — Surface grids for numerical calculation

8 © ISO 2021 – All rights reserved

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ISO 14505-4:2021(E)

The control model is intended to imitate a physical manikin and includes the following three operating

modes:

a) Controlled surface temperature (constant temperature mode): generally, the surface temperature

of all segments is maintained at 34 °C (see ISO 14505-2).

b) Controlled heat generation (constant heat flux mode): this method uses a metabolic rate to

represent the heat flux for all segments. An example of the metabolic rate during vehicle driving

is shown in ISO/TS 14505-1 and ISO 8996. Note that this method is less commonly used than the

other two.

c) Described by comfort equation (comfort equation mode): generally, the parameter values for all

2 [3]

segments in this mode are t = 36,4 °C and R = 0,054 m °C/W .

cr cr

7.3.2 Calculation of heat exchange

The primary problem for the heat transfer calculation is determining the appropriate treatment of

the boundary condition on the surface of the manikin. Once this has been designated, the following

treatments can be used:

a) Flow field, radiant field and heat transfer on the surface of the manikin are solved simultaneously.

The temperature distribution is calculated directly by solving for entrainment of heat in the

boundary layer; however, the convective heat transfer coefficient is not explicitly calculated. In

this case, the grid size near the surface should be small enough to resolve the heat transfer (the

boundary layer). Otherwise, a well-tuned wall function developed to calculate the heat transfer

near the solid boundary should be adopted.

b) The convective and mean radiant heat transfer

**...**

FINAL

INTERNATIONAL ISO/FDIS

DRAFT

STANDARD 14505-4

ISO/TC 159/SC 5

Ergonomics of the thermal

Secretariat: BSI

environment — Evaluation of thermal

Voting begins on:

2021-06-15 environments in vehicles —

Voting terminates on:

Part 4:

2021-08-10

Determination of the equivalent

temperature by means of a numerical

manikin

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 SUPPOR TING

DOCUMENTATION.

IN ADDITION TO THEIR EVALUATION AS

Reference number

BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-

ISO/FDIS 14505-4:2021(E)

LOGICAL, COMMERCIAL AND USER PURPOSES,

DRAFT INTERNATIONAL STANDARDS MAY ON

OCCASION HAVE TO BE CONSIDERED IN THE

LIGHT OF THEIR POTENTIAL TO BECOME STAN-

DARDS TO WHICH REFERENCE MAY BE MADE IN

©

NATIONAL REGULATIONS. ISO 2021

---------------------- Page: 1 ----------------------

ISO/FDIS 14505-4:2021(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

CP 401 • Ch. de Blandonnet 8

CH-1214 Vernier, Geneva

Phone: +41 22 749 01 11

Email: copyright@iso.org

Website: www.iso.org

Published in Switzerland

ii © ISO 2021 – All rights reserved

---------------------- Page: 2 ----------------------

ISO/FDIS 14505-4:2021(E)

Contents Page

Foreword .iv

Introduction .v

1 Scope . 1

2 Normative references . 1

3 Terms and definitions . 1

4 Symbols . 2

5 Assessment of thermal en vironments in vehicles . 4

6 Principles of assessment utilizing a numerical manikin . 4

7 Calculation method coupled with numerical manikin . 5

7.1 General . 5

7.2 Flow and thermal field around manikin . 6

7.2.1 Convective heat . 6

7.2.2 Radiant heat . 7

7.2.3 Conductive heat . 7

7.3 Calculation of heat exchange on manikin. 7

7.3.1 Structure and control of numerical manikin . 7

7.3.2 Calculation of heat exchange . 9

7.4 Calculation of h .

cal 9

7.5 Calculation outputs . 9

8 Calculation method using thermal factors .10

8.1 General .10

8.2 Flow and thermal field around manikin .10

8.2.1 Convective heat .10

8.2.2 Radiant heat .10

8.2.3 Conductive heat .11

8.3 Calculation of heat exchange .11

8.4 Calculation of h .

cal 11

8.5 Calculation outputs .11

8.5.1 General.11

8.5.2 Constant temperature mode .11

8.5.3 Constant heat flux mode.12

8.5.4 Comfort equation mode .12

Annex A (informative) Calculation via computational fluid dynamics (CFD) technique .13

Annex B (informative) Typical inputs and outputs of calculation with numerical manikin .16

Annex C (informative) Treatment of radiant heat transfer .22

Annex D (informative) Typical inputs and outputs of calculations using thermal factors .24

Annex E (informative) Calculation method of h .27

cal

Annex F (informative) Development of formulae for equivalent temperature calculations

using thermal factors .37

Bibliography .43

© ISO 2021 – All rights reserved iii

---------------------- Page: 3 ----------------------

ISO/FDIS 14505-4:2021(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 of 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 www .iso .org/

iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 159, Ergonomics, Subcommittee SC 5,

Ergonomics of the physical environment.

A list of all parts in the ISO 14505 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.

iv © ISO 2021 – All rights reserved

---------------------- Page: 4 ----------------------

ISO/FDIS 14505-4:2021(E)

Introduction

The interaction of convective, radiant and conductive heat exchange in a vehicle compartment or similar

confined space is highly complex. External thermal loads in combination with the air conditioning

system in a vehicle compartment create non-uniform thermal environments, which are often the

main cause of complaints of thermal discomfort. In vehicles with poor or non-existent air conditioning

systems, non-uniform thermal environments can also be created by the interaction between the

ambient climatic conditions and vehicle structures. While a subjective evaluation reflects the total

sensations of a human body, these often incur great costs while the study phase is being conducted.

Physical measurements provide detailed and accurate local information; however, these results must be

integrated in some way to predict the thermal effects on humans. Furthermore, since specific climatic

factors sometimes play a dominant role in the overall heat exchange of a human body, an evaluation

method that accounts for the relative importance of these factors is required.

This document is part of the ISO 14505 series. To meet the above-stated requirements, this document

provides calculation methods that utilize numerical simulations to assess the total thermal environment

of vehicles. The equivalent temperature, obtained from measurements taken using a thermal manikin,

is defined in ISO 14505-2. This document extends the definition of the ISO 14505 series to include

numerical evaluation when this document is used in conjunction with the equivalent temperature

defined in ISO 14505-2.

As described in ISO 14505-2, an equivalent temperature can be utilized in the assessment of vehicle

cabins and other various enclosed spaces with non-uniform environments. As is the case for

ISO 14505-2, this document can also be applied to vehicle cabins and other enclosed spaces.

This document supposes that the ISO 14505 series will be applied to various situations, such as:

— in the case of experimental facilities that are not prepared;

— in the case of prototypes that are incomplete;

— in the case of conditions that are difficult to simulate in controlled experimental settings;

— in the case that occupants are extrapolated to unknown or virtual environments.

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FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 14505-4:2021(E)

Ergonomics of the thermal environment — Evaluation of

thermal environments in vehicles —

Part 4:

Determination of the equivalent temperature by means of

a numerical manikin

1 Scope

This document provides guidelines for extending the definition of equivalent temperature to predictive

purposes and specifies a standard prediction method for the assessment of thermal comfort in vehicles

using numerical calculations. Specifically, this document sets forth a simulated numerical manikin as

a viable alternative to the thermal manikin for the purpose of calculating the equivalent temperature.

2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements 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.

ISO 13731, Ergonomics of the thermal environment — Vocabulary and symbols

ISO 14505-2, Ergonomics of the thermal environment — Evaluation of thermal environments in vehicles —

Part 2: Determination of equivalent temperature

3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 13731 and ISO 14505-2 and

the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp

— IEC Electropedia: available at http:// www .electropedia .org/

3.1

numerical manikin

virtual thermal manikin recreating a thermal manikin, or a digital model of a thermal manikin used to

calculate performance

3.2

physical manikin

real thermal manikin to measure real environment

3.3

computational fluid dynamics

CFD

simulation of a series of calculations based on specific boundary conditions and specific parameters

associated with fluid and thermal fields using discrete equations based on the Navier-Stokes/Lattice-

Boltzmann equations as well as heat transfer equations that consider convection, radiation and

conduction, and generally account for the effects of turbulent flow

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ISO/FDIS 14505-4:2021(E)

4 Symbols

A complete list of symbols used in this document is presented in Table 1.

Table 1 — Symbols and units

Symbol Term Unit

α Solar absorptivity on clothing (skin on unclothed area) surface –

2

A Skin surface area m

2

C Convective heat loss from clothing (skin on unclothed area) surface W/m °C

f Area factor (ratio of clothed to nude area) –

cl

2

h Convective heat transfer coefficient W/m °C

c

2

h Total heat transfer coefficient in a standard environment W/m °C

cal

2

h Convective heat transfer coefficient in a standard environment W/m °C

cs

2

h Radiant heat transfer coefficient W/m °C

r

2

h Radiant heat transfer coefficient in a standard environment W/m °C

rs

2

I Thermal insulation of clothing m °C/W

cl

2

Q Total heat loss from skin surface W/m

2

Q Set value of Q at constant heat flux mode W/m

set

2

R Radiant heat loss from clothing (skin on unclothed area) surface, including effect of W/m

solar radiation

2

R Thermal insulation between core and skin assumed by comfort equation m °C/W

cr

2

R Total thermal resistance between the manikin skin surface and the environment m °C/W

t

2

S Mean solar radiation reached on clothing (skin on unclothed area) surface W/m

t Air temperature °C

a

t Air temperature at h calculation °C

aset cal

t Clothing (skin on unclothed area) surface temperature °C

cl

t Core temperature assumed by the comfort equation °C

cr

t Equivalent temperature °C

eq

t Operative temperature including the effects of solar radiation °C

o

t Mean radiant temperature °C

r

t Skin surface temperature °C

sk

t Set value of t at constant temperature mode °C

skset sk

v Air velocity m/s

a

Suffix: segment number of each body part –

n

Suffix: whole body –

whole

Symbols used in Annex E

2

A Body surface area of the manikin m

b

2

A Elemental surface area of the element i

m

ei,

2

Segmental surface area of the segment n

A m

n

B

Absorption factor of radiation from surface elements i to j –

ij,

F View factor of radiation from surface elements i to j

–

ij,

2

Total heat transfer coefficient of segment n for calibration

h

W/m K

caln,

2

h Total heat transfer coefficient of the entire manikin for calibration W/m K

calw, hole

ij, –

Variable body surface element number

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ISO/FDIS 14505-4:2021(E)

Table 1 (continued)

Symbol Term Unit

–

Variable spatial volume element number for calculation of t

a

k

Variable body surface element number in the recurrence equation of B

ij,

m Number of body surface elements –

b

End body surface element number of segment n –

m

en,

m Start body surface element number of segment n –

sn,

–

m Number of spatial volume elements

v

m Number of wall surface elements –

w

n

Variable local segment number of the manikin –

–

n

Number of manikin segments

seg

2

Q

Heat flux of element i W/m

ei,

2

Averaged heat flux over segment n

Q W/m

n

2

Q Averaged heat flux over the entire manikin W/m

whole

2

R Thermal insulation between core and skin assumed by comfort equation m K/W

cr

2

R

Thermal insulation of element i for the comfort equation mode calculation m K/W

cr,,ei

T Averaged air temperature in the standard chamber (in Kelvins) K

a

t Averaged air temperature in the standard chamber (in Celsius) °C

a

t °C

Air temperature of the spatial volume element k

ae,,k

t

Air temperature entering the standard chamber °C

ai, n

t Core temperature assumed by the comfort equation °C

cr

t

Core temperature of element i for the comfort equation mode calculation °C

cr,,ei

t Operative temperature in the standard chamber °C

o

T Mean radiant temperature of the wall of the standard chamber (in Kelvins) K

r

t Mean radiant temperature of the wall of the standard chamber (in Celsius) °C

r

t Skin surface temperature of the manikin °C

sk

Averaged skin surface temperature of segment n

t °C

sk,n

Estimated average skin surface temperature of the segment n from the comfort

t′

°C

sk,n

equation

t

Averaged skin surface temperature of the entire manikin °C

sk,whole

T Wall surface temperature of the standard chamber (in Kelvins) K

w

t Wall surface temperature of the standard chamber (in Celsius) °C

w

u Air flow velocity in the standard chamber m/s

a

3

V Volumetric air flow rate entering the standard chamber m /s

ai, n

3

V Volume of the spatial volume element k m

ek,

3

V Volume of the spatial region in the standard chamber m

0

2

Correction amount for generated heat of segment n

ΔQ W/m

n

Threshold of difference between t′ and t for iterative convergence

Δt °C

ce sk,n sk,n

Δt Threshold of difference between t and t for iterative convergence °C

o a r

ε –

Emissivity of the surface element j

j

–

ε Emissivity of the manikin

sk

ε Emissivity of the wall of the standard chamber –

w

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ISO/FDIS 14505-4:2021(E)

Table 1 (continued)

Symbol Term Unit

Conversion factor between the actual wall surface temperature and mean radiant –

ξ

m

temperatures

5 Assessment of thermal en vironments in vehicles

The method of assessment by equivalent temperature is defined in ISO 14505-2. The assessment

procedures in ISO 14505-2 are applicable to numerical evaluations, for which “numerical manikin” is

defined in this document. Figure 1 shows the role of this document and its relations with the other

parts of the ISO 14505 series as well as different International Standards.

Figure 1 — Role of numerical evaluation among different International Standards

6 Principles of assessment utilizing a numerical manikin

This document presents two methods for calculating the equivalent temperature. One is a calculation

method coupled with a numerical manikin, as described in Clause 7. The other is a calculation method

using thermal factors, as described in Clause 8. Either method can be used to evaluate the thermal

environment in vehicles.

The former calculation method coupled with a numerical manikin is intended for use with a simulation

tool, such as computational fluid dynamics (CFD). A numerical manikin imitates a physical manikin

to calculate the equivalent temperature. The method of calculation using thermal factors estimates

the equivalent temperature by assuming the existence of the imaginary numerical manikin. In this

method, the equivalent temperature is calculated using the thermal factors, air temperature, radiant

temperature, air velocity and solar radiation. Figure 2 shows a schematic of the two methods.

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ISO/FDIS 14505-4:2021(E)

Figure 2 — Two methods for calculating equivalent temperature

7 Calculation method coupled with numerical manikin

7.1 General

This clause describes the framework of the calculation. To evaluate the indoor environment of a vehicle

numerically, the following issues should be considered and taken account (see Figure 3):

a) heat flow through the shell structure of the vehicle;

b) flow and thermal field in the cabin;

c) radiant field (including solar radiation) in the cabin;

d) conductive heat exchange;

e) heat balance of the thermal manikin model (numerical manikin).

This document is intended to be applied to the region around the manikin, relating to items b) and e).

The heat flow through the structure of the vehicle body is defined as suitable. This document defines

indispensable ideas concerning the above items, which will enable successful and useful calculations in

these situations. However, this document does not define any specific methods for utilization because

all methods present both advantages and disadvantages for particular problems.

Once the environmental state concerning thermal comfort in the cabin is calculated, evaluation

becomes possible. Items a) to d) give the principal local parameters of air velocity, temperature and

radiation, though some simultaneous calculation coupling with the heat balance calculation is required.

This calculation will produce a heat transfer value close to that measured using the physical manikin.

Therefore, the evaluation method described in ISO 14505-2 is applicable.

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ISO/FDIS 14505-4:2021(E)

Key

1 outside of vehicle 5 convection

2 shell structure 6 radiation

3 interior of vehicle 7 conduction

4 thermal manikin

a

Other standards (TC22 related).

b

This document.

NOTE Evaluation of the area in contact with the seat is outside the scope of this document.

Figure 3 — Framework of heat transfer system

7.2 Flow and thermal field around manikin

7.2.1 Convective heat

The flow and thermal field in the cabin are estimated via calculations. One practical option for this is

CFD. The informative concrete contents of this method are represented in Annex A. The outputs are

the air velocity vector and air temperature in a cabin. The heat flux on the wall and surface are also

obtained through this calculation.

The primary problem in CFD calculations is the treatment of boundary conditions. This can be overcome

in practice by selecting any of the following:

a) Calculate the heat transfer on the surface of the manikin using CFD directly.

b) As a preliminary, calculate the heat transfer coefficient on the surface of the manikin using CFD.

Then calculate the flow and thermal field coupling using the heat balance calculation of the manikin.

c) Utilize the heat transfer coefficient obtained by measurement. Then calculate the flow and thermal

field coupling with the heat balance calculation of the manikin, as described in b).

d) Estimate the heat transfer coefficient using a predictive formula based on the air velocity or

temperature. Then calculate the flow and thermal field coupling using the heat balance calculation

for the manikin, as described in b).

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ISO/FDIS 14505-4:2021(E)

7.2.2 Radiant heat

The radiant field is calculated based on the geometric condition in a cabin separated from the flow field

calculation. Regarding long-wave radiation, as a preliminary, the view factor relating to all potential

combinations between different surface elements of the wall and the manikin or human body should

be calculated. Once those factors have been obtained, the radiant heat exchange is calculated when the

temperature of a pair of surface elements is given. As stated previously, the radiant heat is involved in

the boundary conditions of the heat transfer equation, so that the temperature is calculated iteratively

until convergence. For convenience, those factors are converted to the mean radiant heat transfer

coefficient.

Short-wave radiation (solar radiation) can be treated as energy flux striking the surface. Here, the

transmission loss through the window glass should be taken into consideration. Solar radiation can be

regarded as divided into the following components:

a) direct solar radiation;

b) sky solar radiation;

c) reflection on the ground.

The solar radiant heat is also involved in the boundary conditions of the heat transfer equation. In the

case of a climate wind tunnel test performed without use of a solar lamp, it is supposed that the effects

of solar radiation are neglected. Concrete informative treatments are represented in Annex C.

7.2.3 Conductive heat

Evaluation of the contacted segment is outside the scope of this document. The conductive heat transfer

between the manikin and seat is disregarded in the calculations.

7.3 Calculation of heat exchange on manikin

7.3.1 Structure and control of numerical manikin

Figure 4 shows the theoretical structure of the numerical manikin with regard to a human-shaped one.

The centre of each segment is assumed to consist of an adiabatic core. A heat generator is equipped on

the surface of the manikin.

The shape of the manikin is defined by calculation grids for CFD, as shown in Figure 5 a). The partition

is performed to imitate an actual manikin, as in Figure 5 b). Boundary conditions are given for each

segment.

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ISO/FDIS 14505-4:2021(E)

Key

1 adiabatic core

2 heat generator on surface

Figure 4 — Theoretical structure of numerical manikin

a) Full-body model of manikin b) Partition of surface grids (16-segment case

shown)

Key

1 head 6 forearm

2 chest 7 hand

3 back 8 thigh

4 pelvis 9 leg

5 upper arm 10 foot

Figure 5 — Surface grids for numerical calculation

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ISO/FDIS 14505-4:2021(E)

The control model is intended to imitate a physical manikin and includes the following three operating

modes:

a) Controlled surface temperature (constant temperature mode): generally, the surface temperature

of all segments is maintained at 34 °C (see ISO 14505-2).

b) Controlled heat generation (constant heat flux mode): this method uses a metabolic rate to

represent the heat flux for all segments. An example of the metabolic rate during vehicle driving

is shown in ISO/TS 14505-1 and ISO 8996. Note that this method is less commonly used than the

other two.

c) Described by comfort equation (comfort equation mode): generally, the parameter values for all

2 [3]

segments in this mode are t = 36,4 °C and R = 0,054 m °C/W .

cr cr

7.3.2 Calculation of heat exchange

The primary problem for the heat transfer calculation is determining the appropriate treatment of

the boundary condition on the surface of the manikin. Once this has been designated, the following

treatments can be used:

a) Flow field, radiant field and heat transfer on the surface of the manikin are solved simultaneously.

The temperatu

**...**

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