ISO/FDIS 14505-4

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
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ISO/FDIS 14505-4:2021(E)
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© ISO 2021

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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 ...................................................................................................................................................................................

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 .................................................................................................................................................................................

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

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

using thermal factors ....................................................................................................................................................................................37

Bibliography .............................................................................................................................................................................................................................43

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

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

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

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

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 conditions that are difficult to simulate in controlled experimental settings;

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

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.

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

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

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

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

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

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

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

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

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

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.

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):

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

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.

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

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

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

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

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

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

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.

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

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 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

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

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

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

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

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

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