Fans — System effects and system effect factors

This document deals with the likely degradation of air performance of fans tested in standardized airways in accordance with ISO 5801 when compared with the performance of fans tested under actual site conditions. It deals with the performance of a number of generic types of fan and fittings. The results given are intended as guidelines and only provide trends, as the system effect depends on the exact geometry of the fan and disturbing component. The test data presented in this document are taken from an extensive experimental program conducted 20 years ago by NEL (National Engineering Laboratory, UK), mainly on axial and centrifugal fans. Data are also taken from several research projects financially supported by ASHRAE, some of them being carried out in the AMCA laboratory in Chicago, as well as from results published previously by individual fan manufacturers.

Ventilateurs — Effet système et facteurs d’effet système

Le présent document traite de la dégradation probable de la performance aéraulique des ventilateurs soumis à essai sur circuits standards conformément à l'ISO 5801 par rapport aux performances de ventilateurs soumis à essai dans des conditions réelles sur site. Il traite des performances d'un certain nombre de ventilateurs et de composants génériques. Les résultats obtenus constituent des lignes directrices et ne fournissent que des tendances, car l'effet système dépend de la géométrie exacte du ventilateur et du composant perturbateur. Les données présentées dans le présent document sont issues d'un vaste programme expérimental mené il y a 20 ans par le laboratoire national britannique pour l'ingénierie (NEL), principalement sur des ventilateurs axiaux et centrifuges. Les données sont aussi tirées de plusieurs projets de recherche financés par l'ASHRAE, dont certains sont menés dans le laboratoire de l'AMCA à Chicago, ainsi que de résultats publiés par des fabricants de ventilateurs individuels.

General Information

Status
Published
Publication Date
06-Sep-2020
Technical Committee
Current Stage
9092 - International Standard to be revised
Completion Date
15-Aug-2023
Ref Project

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TECHNICAL ISO/TR
REPORT 16219
First edition
2020-09
Fans — System effects and system
effect factors
Ventilateurs — Effet système et facteurs d’effet système
Reference number
ISO/TR 16219:2020(E)
©
ISO 2020

---------------------- Page: 1 ----------------------
ISO/TR 16219:2020(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2020
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 2020 – All rights reserved

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ISO/TR 16219:2020(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and symbols . 1
4 Origin of fan system effects . 2
5 Definitions of system effect factor (SEF) . 4
5.1 Inlet SEF . 4
5.2 Outlet system effect . 6
6 Examples of inlet SEF . 9
6.1 Introduction . 9
6.2 Axial fans .10
6.2.1 Experimental setups .10
6.2.2 Results .15
6.3 Centrifugal and mixed-flow fans .17
6.3.1 Experimental setups .17
6.3.2 Results .24
7 Examples of outlet SEF .30
7.1 Axial fans .30
7.1.1 General.30
7.1.2 Experimental setups .30
7.1.3 Results .30
7.2 Centrifugal and mixed-flow fans .32
7.2.1 Experimental setups .32
7.2.2 Results .33
8 Reducing system effects .34
8.1 General .34
8.2 Inlet effects .34
8.2.1 General.34
8.2.2 Non-uniform flow . .35
8.2.3 Swirl or vorticity .36
8.2.4 Inlet blockage . . .36
8.3 Outlet effects .39
8.3.1 General.39
8.3.2 Insufficient duct length .39
8.3.3 Outlet obstruction . .40
8.3.4 Non-uniform flow . .40
8.4 Examples of the effects of poor inlet and outlet connections .43
9 Conclusions .44
Annex A (informative) Basic principles on fan performance representation .45
Annex B (informative) Fan system calculation .73
Bibliography .83
© ISO 2020 – All rights reserved iii

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ISO/TR 16219:2020(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 117, Fans.
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 2020 – All rights reserved

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ISO/TR 16219:2020(E)

Introduction
ISO 5801 provides the information for accurately measuring the performance of fans when tested
under standardised laboratory conditions. The ducting where specified ensures a fully developed
symmetrical velocity profile at the fan inlet. There may also be sufficient straight ducting at the fan
outlet to ensure efficient conversion of the distorted velocity profile at the fan outlet to a measurable
stable and homogeneous profile at the measuring station.
This document shows how fan performance is affected by both inlet and outlet connections to it.
System designers must not only look at the ideal performance curve and calculated system pressure
drop but also take into account the losses at the entry and exit points of the fan. These are described in
the document.
The concept of the system effect factor (SEF) was introduced to the fan industry by AMCA in 1973.
Since its inception it has become widely accepted worldwide. In more recent years it has been realized
that the SEF depends not only on the fan type and the fitting geometry but also on the fan design and
manufacturing. Some less efficient fans may sometimes be less sensitive to system effect induced by
poor inlet flow conditions than more efficient fans of the same type.
Furthermore, the origin of the system effect induced by a fitting at the fan inlet is different from the
one due to the same fitting located on the fan outlet. That is why two different definitions of SEF are
proposed in this document according to whether the appurtenance is at the fan inlet or fan discharge.
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TECHNICAL REPORT ISO/TR 16219:2020(E)
Fans — System effects and system effect factors
1 Scope
This document deals with the likely degradation of air performance of fans tested in standardized
airways in accordance with ISO 5801 when compared with the performance of fans tested under actual
site conditions. It deals with the performance of a number of generic types of fan and fittings. The
results given are intended as guidelines and only provide trends, as the system effect depends on the
exact geometry of the fan and disturbing component.
The test data presented in this document are taken from an extensive experimental program conducted
20 years ago by NEL (National Engineering Laboratory, UK), mainly on axial and centrifugal fans.
Data are also taken from several research projects financially supported by ASHRAE, some of them
being carried out in the AMCA laboratory in Chicago, as well as from results published previously by
individual fan manufacturers.
2 Normative references
There are no normative references in this document.
3 Terms, definitions and symbols
No terms and definitions are listed in this document.
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/
The following symbols are used:
Symbol Description SI units I-P units
2 2
A Fan outlet area m ft
2
C System effect (SE) coefficient (see 5.2) Dimensionless Dimensionless
p Conventional pressure loss (see 5.2) Pa in. wg
C
p Fan pressure Pa in. wg
f
p Fan dynamic pressure (see Clause 4) Pa in. wg
fd
p Fan static pressure Pa in. wg
fs
p System effect (see 5.2) Pa in. wg
SE
Additional pressure loss due to non-uni-
p Pa in. wg
SEo
form flow (see 5.2)
3
q Volume flow rate of the fan m /s cfm
V1
S System effect factor Dimensionless Dimensionless
EF
3 0,5
ξ Loss coefficient (see 5.1) (m /s)/(Pa )
3 2
ρ Density of air kg/m lbm/ft
3 2
ρ Standard air density kg/m lbm/ft
std
NOTE  The term “fan dynamic pressure” or “dynamic pressure” is used throughout this document and is
equivalent to the term “velocity pressure” as used in some countries.
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ISO/TR 16219:2020(E)

4 Origin of fan system effects
Manufacturers’ fan performance ratings are mostly based on tests carried out in a laboratory under
ideal conditions. Ideal conditions refer to uniform, swirl-free air velocity profiles at fan inlet and outlet,
like those of the test rigs described in ISO 5801 and AMCA 210. In ‘real life’ fan installations, such ideal
conditions may not be present due to improper connection of the fan to the system. Such improper
connections include obstacles at fan inlets and outlets that alter the aerodynamic characteristics of the
fan and lead to deficient performance in relation to catalogue ratings, even when the system pressure
losses have been estimated accurately. The term “system effect” is a measure of this degradation of fan
performance.
The origin of system effect is different at fan outlet and at fan inlet. At the fan outlet, for example in
the case of an improperly connected outlet fitting such as an elbow, damper or duct branch, the system
effect is linked to less-than-optimum non-uniform flow profiles induced by the fan at the entrance to
the fitting (Figure 1). This degraded flow will create more pressure loss across the fitting than would
be the case when measuring the fitting loss assuming uniform homogeneous flow profiles or when
[14]
estimating it from standard handbooks such as the ASHRAE Handbook of Fundamentals .
When the fitting is at the fan inlet, for example an elbow or a fan inlet duct/box (Figure 2), the velocity
profiles at the inlet to the fitting may be uniform and the fitting pressure loss as measured or estimated
from standard handbooks may be valid. However, the flow patterns at the fan inlet (or fitting outlet)
may be disturbed with the presence of a vortex, spin or vena-contracta. This less than optimum flow
condition at fan inlet caused by the fitting will lead to a reorganization of the flow inside the impeller
and therefore a deterioration of fan performance in relation to catalogue ratings. Not only the fan curve
may be affected by this disturbing obstacle but also sometimes, but not always, the fan power curve. A
companion document will be drafted at a later date to show the influence of the inlet obstacles on the
fan power curve for the same configurations of fans and fittings as in this document.
In both cases, the resulting air flow of the fan-system combination deteriorates, but for distinct
physical reasons. For this reason, two different definitions and treatment of fan system effect are
incorporated, depending on whether the fitting is at the fan inlet or fan outlet. It is also recognized
that in some situations, obstacles very close to fan discharge (e.g. side walls at a short distance of a
plenum fan impeller as shown in Figure 20) may also deteriorate fan performance in the same manner
as components located at fan inlet.
Key
1 axial fan
Figure 1 — Non-uniform velocity profiles at fan outlet
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ISO/TR 16219:2020(E)


a
Impeller rotation.
Figure 2 — Vortex at fan inlet
An ideal connection to a fan would be one which results in a velocity distribution across the fan inlet
connection plane which is relatively uniformly distributed and without appreciable swirl component,
as shown in Figure 3.

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ISO/TR 16219:2020(E)

a
a) Ideal p distribution b) Good p distribution
d d
b
c) Satisfactory p distribution
d

Key
p mean dynamic pressure of the duct flow
d
a
Also satisfactory for flow into fan inlets, but may be unsatisfactory for flow into inlet boxes, may produce swirl
in boxes.
b
More than 75 % of p readings greater than p /10 (unsatisfactory for flow into fan inlets of inlet boxes).
d dmax
Figure 3 — Ideal fan connections
5 Definitions of system effect factor (SEF)
5.1 Inlet SEF
With a component at the fan inlet, the SEF is defined as the relative airflow drop Δq /q along a given
v1 v1
system line as shown in Figure 4. In this figure, the solid curve and the dotted line curve are the static
pressure curves without and with system effect, respectively. The curve with system effect is obtained
by adding the pressure loss of the fitting for each flow rate increment, when it may be measured or
estimated from guidebooks (e.g. IDEL'CIK), to the static pressure of the fan + inlet fitting combination.
This procedure allows for the assessment of the installation effect related to the degradation of the fan
curve itself without accounting for the pressure loss of the fitting.
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ISO/TR 16219:2020(E)

To quantify the system effect on the whole fan curve, the quantity Δq /q is plotted versus the system
V1 V1
1)
resistance coefficient ξ=qp/ (p being the fan static pressure at q ) in Figure 5.
fs V1
V1 fs
The SEF for a given fan + inlet fitting configuration is the average of Δq /q over the ξ range, presented
V1 V1
as a percentage in the results. Δq /q is positive when the flow with the inlet fitting is lower than that
V1 V1
of the free inlet configuration.
Key
q volume flow rate of the fan
V1
p fan pressure
fs
1 fan curve without system effect
2 fan curve with system effect
3 system line
Figure 4 — Definition of q and Δq on a given system line
V1 V1
1) q is either in cfm or m³/s while p is either in in. wg or Pa.
V1 fs
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ISO/TR 16219:2020(E)

Key
Δq /q relative flow drop in volume flow rate of the fan
V1 V1
ξ system resistance coefficient
1 system effect curve
Figure 5 — Example of relative flow drop Δq /q versus system resistance coefficient ξ
V1 V1
Clause 6 describes various situations resulting in inlet system effects.
5.2 Outlet system effect
Outlet system effect is a measure of the pressure losses across fan outlet appurtenances such as an
outlet duct, elbow, volume control damper, duct branch or plenum, due to non-uniform outlet flow
induced by the fan and improper outlet connections.
Most fans, for applications requiring systems connected at their outlets, are tested and rated for
performance with an outlet duct 2 to 3 ‘equivalent duct diameter’ long. The outlet duct helps control the
diffusion of the outlet flow and establish a uniform velocity profile (Figure 6). In most cases, it is not
practical for the fan manufacturer to supply this duct as part of the fan, but rated performance will not
be achieved unless a comparable duct is included in system design.
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ISO/TR 16219:2020(E)

Key
1 centrifugal fan
2 cutoff
3 blast area
4 outlet area
5 discharge duct
6 axial fan
7 25 % effective duct length
8 50 % effective duct length
9 75 % effective duct length
10 100 % effective duct length
Figure 6 — Velocity profiles at fan outlet
The techniques documented to estimate pressure losses of a fitting such as an elbow or the published
pressure drop performance from a manufacturer of a fitting such as a damper are based upon uniform
approach velocity profiles. The pressure loss so estimated is referred to as the ‘conventional pressure
loss’ across the fitting. Unless uniform approach velocity profile is ensured, there will be additional
pressure losses across these fittings. Outlet system effect is used to estimate the actual pressure loss
across the fitting in a given installation.
Clause 7 describes various situations resulting in outlet system effects. The total outlet system effect,
p (Pa), for a given situation (fitting) is defined as:
SE
p = p + p
SE c SEo
where
p is conventional pressure loss (Pa);
c
p is additional pressure loss due to non-uniform flow (Pa).
SEo
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ISO/TR 16219:2020(E)

p can be expressed as a function of flow by the following formula:
SEo
p = C × p
SEo fd2
where
2
p is dynamic pressure at fan outlet 0,5*ρ*(q /A ) ;
fd2 V1 2
3
q is fan airflow rate, m /s;
V1
2
A is fan outlet area in m ;
2
C is system effect coefficient;
3
ρ is air density in kg/m .
The outlet system effect p at each flow rate q must be added to the design system curve to obtain
SE V1
the actual system curve (Figure 7).
The system effect coefficient C is averaged over the fan curve to obtain what is called the outlet SEF in
Clause 7.
P – P = fitting conventional pressure drop at design flow
B A
P – P = outlet system effect, p , at design flow
C B SEo
P – P = fitting conventional pressure drop at actual flow
E D
P – P = outlet system effect, p , at actual flow
F E SEo

8 © ISO 2020 – All rights reserved

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ISO/TR 16219:2020(E)

Key
q fan volume flow rate
V
P fan pressure
1 fan catalogue pressure-flow curve
2 actual system curve
3 system curve with fitting conventional pressure drop
4 system curve without conventional pressure drop and no allowance for system effect
5 design pressure
6 actual flow
7 design flow
Figure 7 — Modification of design system curve due to outlet system effect
In some cases the conventional pressure loss p cannot be estimated or is not relevant, like for instance
c
with side walls close to the impeller of a plenum fan in the example of 7.2.2.2. In this case the system
effect is due to the disturbed flow in the impeller induced by the proximity of the walls.
6 Examples of inlet SEF
6.1 Introduction
Examples of inlet system effect are taken from different dedicated research programs carried out since
the 1990s. The National Engineering Laboratory (NEL) in the UK performed an extensive experimental
study on nine different types of fans and six ductwork fittings at the fan inlet. A summary of the test
configurations and main results obtained is given in References [3] and [4]. Otherwise, several research
programs have been financially supported by ASHRAE in which the tests were performed mainly by
AMCA to quantify the SEF on:
[5]
— a backward inclined/airfoil centrifugal fan – ASHRAE Research Project 1216-RP ;
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ISO/TR 16219:2020(E)

[6]
— a forward curved centrifugal fan – ASHRAE Research Project 1272-RP ;
[7]
— two airfoil centrifugal plenum fans – ASHRAE Research Project 1420-TRP ;
[8]
— three sizes of propeller fans of the same series – ASHRAE Research Project 1223-RP .
Finally, a test was done more recently by AMCA on a forward curved centrifugal fan with an inlet 90°
segmented elbow at various orientations.
6.2 Axial fans
6.2.1 Experimental setups
6.2.1.1 NEL
All the tests were performed on a ductwork of D = 630 mm, where D is the duct diameter. A layout of
the test ductwork with a bend connected to the fan inlet is shown in Figure 8. The distance between the
inlet fitting and the fan is varied from 0D, as in Figure 8 to 2D.
Details of the experimental program and measurement procedure are given in Reference [4] and
private reports. The test data used in the present analysis are the performance curves of the fan alone
and fan + inlet fitting and the measured pressure losses of the fittings. All the fan curves, initially based
on total pressure, were transformed into static pressure curves by subtracting the dynamic pressure at
the fan outlet according to ISO 5801.
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ISO/TR 16219:2020(E)

Key
1 test fan and fitting
2 throttle
3 auxiliary boost fan
4 silencers
5 flow measurement nozzle
6 flow measurement and control section
7 outlet duct
8 inlet duct
SOURCE Based on content from National Engineering Laboratory (NEL) Fan Connected Ductwork Study for
FETA (FET001) February 1992, reproduced with permission from the Fan Manufacturers Association, FETA UK.
Figure 8 — Test rig for determination of installation effect — Fitting at fan inlet
Table 1 gives the main characteristics of the axial fans tested by NEL while Figure 9 shows views of the
fans, including centrifugal fans. Figure 10 presents sketches of the fittings that were connected to the
fan inlet (or outlet) via transition elements.
They include:
a) rectangular/circular transition, section 800 × 400 → D = 630 mm, length 950 mm;
b) short square bend 90°, section 630 × 630, curvature radius 100 mm;
c) square mitred bend 90°, section 630 × 630, with guide vanes;
d) circular five-piece segmented bend, D = 630 mm;
e) rectangular to rectangular box fitting, section 800 × 400, length 2 400 mm;
f) rectangular splitter silencer, section 800 × 400, length 1 200 mm;
g) banjo connector, section 1 260 × 630, length 1 890 mm.
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ISO/TR 16219:2020(E)

Table 1 — Main characteristics of the axial fans tested by NEL
Fan Fan type Blade setting Hub/tip ratio Speed
° rpm
1 tubeaxial 24 0,223 1 440
2 tubeaxial 30 0,223 1 440
3 vaneaxial 24 0,389 1 440
4 vaneaxial 32 0,389 1 440
5 tubeaxial 24 0,389 2 900
6 tubeaxial 32 0,389 2 900
NOTE  All the fans have a diameter of 630 mm.
SOURCE: Based on content from National Engineering Laboratory (NEL) Fan Connected Ductwork Study
for FETA (FET001) February 1992, reproduced with permission from the Fan Manufacturers Association,
FETA UK.
SOURCE Based on content from National Engineering Laboratory (NEL) Fan Connected Ductwork Study for
FETA (FET001) February 1992, reproduced with permission from the Fan Manufacturers Association, FETA UK.
Figure 9 — Views of the NEL test fans
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ISO/TR 16219:2020(E)

Key
1 short square bend 90°
2 square mitred bend 90°
3 circular five-piece segmented bend
4 rectangular/circular transition
5 rectangular splitter silencer
6 banjo connector
7 rectangular to rectangular box fitting
SOURCE Based on content from National Engineering Laboratory (NEL) Fan Connected Ductwork Study for
FETA (FET001) February 1992, reproduced with permission from the Fan Manufacturers Association, FETA UK.
Figure 10 —
...

RAPPORT ISO/TR
TECHNIQUE 16219
Première édition
2020-09
Ventilateurs — Effet système et
facteurs d’effet système
Fans — System effects and system effect factors
Numéro de référence
ISO/TR 16219:2020(F)
©
ISO 2020

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ISO/TR 16219:2020(F)

DOCUMENT PROTÉGÉ PAR COPYRIGHT
© ISO 2020
Tous droits réservés. Sauf prescription différente ou nécessité dans le contexte de sa mise en œuvre, aucune partie de cette
publication ne peut être reproduite ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique,
y compris la photocopie, ou la diffusion sur l’internet ou sur un intranet, sans autorisation écrite préalable. Une autorisation peut
être demandée à l’ISO à l’adresse ci-après ou au comité membre de l’ISO dans le pays du demandeur.
ISO copyright office
Case postale 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Genève
Tél.: +41 22 749 01 11
E-mail: copyright@iso.org
Web: www.iso.org
Publié en Suisse
ii © ISO 2020 – Tous droits réservés

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ISO/TR 16219:2020(F)

Sommaire Page
Avant-propos .iv
Introduction .v
1 Domaine d'application . 1
2 Références normatives . 1
3 Termes, définitions et symboles . 1
4 Origine des effets système des ventilateurs . 2
5 Définitions du facteur d’effet système (SEF) . 4
5.1 SEF à l'aspiration . 4
5.2 Effet système au refoulement . 6
6 Exemples de SEF à l’aspiration. 9
6.1 Introduction . 9
6.2 Ventilateurs axiaux .10
6.2.1 Installations expérimentales .10
6.2.2 Résultats .15
6.3 Ventilateurs centrifuges et hélico-centrifuges .17
6.3.1 Installations expérimentales .17
6.3.2 Résultats .24
7 Exemples de SEF au refoulement .29
7.1 Ventilateurs axiaux .29
7.1.1 Généralités .29
7.1.2 Installations expérimentales .29
7.1.3 Résultats .29
7.2 Ventilateurs centrifuges et hélico-centrifuges .31
7.2.1 Installations expérimentales .31
7.2.2 Résultats .32
8 Réduction des effets système .33
8.1 Généralités .33
8.2 Effets à l’aspiration .33
8.2.1 Généralités .33
8.2.2 Écoulement non uniforme .34
8.2.3 Giration ou tourbillon .35
8.2.4 Obstruction à l’aspiration . .36
8.3 Effets au refoulement .38
8.3.1 Généralités .38
8.3.2 Longueur de conduit insuffisante .38
8.3.3 Obstacle au refoulement .39
8.3.4 Écoulement non uniforme .39
8.4 Exemples d’effets dus à de mauvais raccordements à l'aspiration et au refoulement .42
9 Conclusions .43
Annexe A (informative) Principes de base relatifs à la représentation de la performance
des ventilateurs .44
Annexe B (informative) Calcul du système de ventilation.76
Bibliographie .87
© ISO 2020 – Tous droits réservés iii

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ISO/TR 16219:2020(F)

Avant-propos
L'ISO (Organisation internationale de normalisation) est une fédération mondiale d'organismes
nationaux de normalisation (comités membres de l'ISO). L'élaboration des Normes internationales est
en général confiée aux comités techniques de l'ISO. Chaque comité membre intéressé par une étude
a le droit de faire partie du comité technique créé à cet effet. Les organisations internationales,
gouvernementales et non gouvernementales, en liaison avec l'ISO participent également aux travaux.
L'ISO collabore étroitement avec la Commission électrotechnique internationale (IEC) en ce qui
concerne la normalisation électrotechnique.
Les procédures utilisées pour élaborer le présent document et celles destinées à sa mise à jour sont
décrites dans les Directives ISO/IEC, Partie 1. Il convient, en particulier, de prendre note des différents
critères d'approbation requis pour les différents types de documents ISO. Le présent document a été
rédigé conformément aux règles de rédaction données dans les Directives ISO/IEC, Partie 2 (voir www
.iso .org/ directives).
L'attention est attirée sur le fait que certains des éléments du présent document peuvent faire l'objet de
droits de propriété intellectuelle ou de droits analogues. L'ISO ne saurait être tenue pour responsable
de ne pas avoir identifié de tels droits de propriété et averti de leur existence. Les détails concernant
les références aux droits de propriété intellectuelle ou autres droits analogues identifiés lors de
l'élaboration du document sont indiqués dans l'Introduction et/ou dans la liste des déclarations de
brevets reçues par l'ISO (voir www .iso .org/ brevets).
Les appellations commerciales éventuellement mentionnées dans le présent document sont données
pour information, par souci de commodité, à l’intention des utilisateurs et ne sauraient constituer un
engagement.
Pour une explication de la nature volontaire des normes, la signification des termes et expressions
spécifiques de l'ISO liés à l'évaluation de la conformité, ou pour toute information au sujet de l'adhésion
de l'ISO aux principes de l’Organisation mondiale du commerce (OMC) concernant les obstacles
techniques au commerce (OTC), voir www .iso .org/ avant -propos.
Le présent document a été élaboré par le comité technique ISO/TC 117, Ventilateurs.
Il convient que l’utilisateur adresse tout retour d’information ou toute question concernant le présent
document à l’organisme national de normalisation de son pays. Une liste exhaustive desdits organismes
se trouve à l’adresse www .iso .org/ fr/ members .html.
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ISO/TR 16219:2020(F)

Introduction
L’ISO 5801 fournit des informations permettant de mesurer de manière fiable les performances des
ventilateurs soumis à des essais dans des conditions de laboratoire normalisées. Le conduit, lorsqu’il
est spécifié, garantit un profil de vitesses symétrique développé à l'aspiration du ventilateur. Il peut
également y avoir une longueur droite de conduit suffisante au refoulement du ventilateur pour assurer
une conversion efficace du profil de vitesses déformé au refoulement du ventilateur en un profil stable
et homogène mesurable à la section de mesurage.
Le présent document montre comment les composants raccordés à l'aspiration et au refoulement ont un
effet sur les performances du ventilateur. Les concepteurs du système doivent non seulement étudier la
courbe idéale de performance et la perte de pression calculée du système, mais aussi prendre en compte
les pertes aux points d'entrée et de sortie du ventilateur. Celles-ci sont décrites dans le document.
Le concept de facteur d'effet système (SEF) a été introduit dans l'industrie des ventilateurs par l'AMCA
en 1973. Depuis sa création, il est devenu largement accepté dans le monde entier. Ces dernières années,
on s'est rendu compte que le SEF dépend non seulement du type de ventilateur et de la géométrie de
raccordement, mais aussi de la conception et de la fabrication du ventilateur. Certains ventilateurs
moins efficaces peuvent parfois être moins sensibles à l'effet système induit par de mauvaises conditions
d’écoulement à l’aspiration que d'autres ventilateurs plus efficaces de même type.
Par ailleurs, l'origine de l'effet système induit par un composant raccordé à l’aspiration du ventilateur
est différente de celle due au même composant raccordé au refoulement du ventilateur. C'est pourquoi
deux définitions différentes du SEF sont proposées dans le présent document selon que l'accessoire est
placé à l'aspiration ou au refoulement du ventilateur.
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RAPPORT TECHNIQUE ISO/TR 16219:2020(F)
Ventilateurs — Effet système et facteurs d’effet système
1 Domaine d'application
Le présent document traite de la dégradation probable de la performance aéraulique des ventilateurs
soumis à essai sur circuits standards conformément à l’ISO 5801 par rapport aux performances de
ventilateurs soumis à essai dans des conditions réelles sur site. Il traite des performances d’un certain
nombre de ventilateurs et de composants génériques. Les résultats obtenus constituent des lignes
directrices et ne fournissent que des tendances, car l'effet système dépend de la géométrie exacte du
ventilateur et du composant perturbateur.
Les données présentées dans le présent document sont issues d'un vaste programme expérimental
mené il y a 20 ans par le laboratoire national britannique pour l’ingénierie (NEL), principalement sur
des ventilateurs axiaux et centrifuges. Les données sont aussi tirées de plusieurs projets de recherche
financés par l'ASHRAE, dont certains sont menés dans le laboratoire de l'AMCA à Chicago, ainsi que de
résultats publiés par des fabricants de ventilateurs individuels.
2 Références normatives
Le présent document ne contient aucune référence normative.
3 Termes, définitions et symboles
Aucun terme n’est défini dans le présent document.
L’ISO et l’IEC tiennent à jour des bases de données terminologiques destinées à être utilisées en
normalisation, consultables aux adresses suivantes:
— ISO Online browsing platform: disponible à l’adresse https:// www .iso .org/ obp
— IEC Electropedia: disponible à l’adresse http:// www .electropedia .org/
Les symboles suivants sont utilisés:
Symbole Description Unités SI Unités I-P
2 2
A Section de sortie du ventilateur m ft
2
C Coefficient d’effet système (SE) (voir 5.2) Sans dimension Sans dimension
p Perte de pression conventionnelle (voir 5.2) Pa in. wg
C
p Pression du ventilateur Pa in. wg
f
Pression dynamique du ventilateur (voir
p Pa in. wg
fd
Article 4)
p Pression statique du ventilateur Pa in. wg
fs
p Effet système (voir 5.2) Pa in. wg
SE
Perte de pression supplémentaire due à
p Pa in. wg
SEo
un écoulement non uniforme (voir 5.2)
3
q Débit-volume du ventilateur m /s cfm
V1
S Facteur d'effet système Sans dimension Sans dimension
EF
NOTE  Les expressions “pression dynamique du ventilateur” ou “pression dynamique” sont utilisés dans
tout le présent document et sont équivalents à “pression de vitesse” utilisé dans certains pays.
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ISO/TR 16219:2020(F)

Symbole Description Unités SI Unités I-P
3 0,5
ξ Coefficient de perte de pression (voir 5.1) (m /s)/(Pa )
3 2
ρ Masse volumique de l'air kg/m lbm/ft
3 2
ρ Masse volumique de l’air normal kg/m lbm/ft
std
NOTE  Les expressions “pression dynamique du ventilateur” ou “pression dynamique” sont utilisés dans
tout le présent document et sont équivalents à “pression de vitesse” utilisé dans certains pays.
4 Origine des effets système des ventilateurs
Les évaluations de performances des ventilateurs des fabricants reposent principalement sur des essais
menés en laboratoire dans des conditions idéales. Les conditions idéales font référence à des profils de
vitesses d'air uniformes et sans giration à l'aspiration et au refoulement du ventilateur, comme ceux
des bancs d’essai décrits dans l’ISO 5801 et l’AMCA 210. Dans les installations “réelles” de ventilateurs,
de telles conditions idéales peuvent ne pas se présenter en raison d'un mauvais raccordement du
ventilateur au système. Ces mauvais raccordements comprennent les obstacles à l'aspiration et au
refoulement du ventilateur qui modifient les caractéristiques aérodynamiques du ventilateur et
entraînent des baisses de performances par rapport aux valeurs nominales du catalogue, même lorsque
les pertes de pression du système ont été estimées avec précision. Le terme “effet système” est une
mesure de cette dégradation des performances du ventilateur.
L'origine de l'effet système est différente à l’aspiration du ventilateur et à son refoulement. Au refoulement
du ventilateur, par exemple en cas de mauvais raccordement d’un composant au refoulement comme le
raccordement d’un coude, d’un registre ou d’un conduit secondaire, l'effet système est lié à des profils
d'écoulement non uniformes non optimaux induits par le ventilateur à l'entrée du composant (Figure 1).
Cet écoulement dégradé crée une perte de pression dans le composant, supérieure à celle qui serait
mesurée en supposant des profils d'écoulement homogènes et uniformes ou si cette perte de pression
[14]
était estimée à partir de la littérature standard telle que l’ASHRAE Handbook of Fundamentals .
Lorsque le composant est placé à l'aspiration du ventilateur, par exemple un coude ou un conduit/une
boîte à l'aspiration (Figure 2), les profils de vitesses à l'entrée du composant peuvent être uniformes
et la perte de pression de celui-ci mesurée ou estimée à partir de la littérature standard, peut être
valable. Cependant, les écoulements à l'aspiration du ventilateur (ou au refoulement du composant)
peuvent être perturbés par la présence d'un tourbillon, d'un tournoiement ou d'une région contractée.
Cette condition d'écoulement non optimale à l'aspiration du ventilateur due au composant aboutit à
une réorganisation de l'écoulement à l'intérieur de la roue et par conséquent à une détérioration des
performances du ventilateur par rapport aux valeurs nominales du catalogue. La courbe du ventilateur
peut être affectée par cet obstacle perturbateur tout comme ce peut être le cas aussi, parfois mais pas
de manière systématique, pour sa courbe de puissance. Un document d’accompagnement sera rédigé
ultérieurement pour montrer l'influence des obstacles à l'aspiration sur la courbe de puissance du
ventilateur avec les mêmes configurations de ventilateurs et de composants que celles utilisées dans le
présent document.
Dans les deux cas, le débit résultant de la combinaison ventilateur-système se détériore, mais pour des
raisons physiques distinctes. Pour cette raison, deux définitions et un traitement différents de l'effet
système d’un ventilateur sont ici fournis, selon la position du composant raccordé, à l'aspiration ou au
refoulement du ventilateur. Il est également reconnu que dans certaines situations, des obstacles très
proches du refoulement du ventilateur (par exemple, des parois latérales situées à proximité d'une roue
de ventilateur centrifuge de plénum comme illustré dans la Figure 20) peuvent également détériorer
les performances du ventilateur comme le feraient des composants situés à l'aspiration du ventilateur.
2 © ISO 2020 – Tous droits réservés

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ISO/TR 16219:2020(F)

Légende
1 ventilateur axial
Figure 1 — Profils de vitesses non-uniformes au refoulement d’un ventilateur

a
Rotation de la roue.
Figure 2 — Tourbillon à l’aspiration du ventilateur
Le raccordement idéal d’un ventilateur serait celui qui permettrait une distribution relativement
uniforme des vitesses dans tout le plan du composant raccordé à l’aspiration du ventilateur, sans
composante giratoire perceptible comme indiqué à la Figure 3.
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ISO/TR 16219:2020(F)

a
a) Distribution p idéale b) Bonne distribution p
d d
b
c) Distribution p satisfaisante
d
Légende
p pression dynamique moyenne de l’écoulement du conduit
d
a
Distribution satisfaisante aussi pour l’écoulement aux aspirations des ventilateurs, mais insuffisante pour
l’écoulement dans les boîtes à l'aspiration, peut entraîner des tourbillons dans les boîtes.
b
Plus de 75 % des relevés de p supérieurs à p /10 (non satisfaisant pour l’écoulement à l’aspiration des
d dmax
boîtes à l’aspiration).
Figure 3 — Raccordements idéaux d’un ventilateur
5 Définitions du facteur d’effet système (SEF)
5.1 SEF à l'aspiration
Avec un composant raccordé à l’aspiration, le SEF est défini comme la chute relative du débit Δq /q
v1 v1
le long d’une courbe du système donné comme illustré à la Figure 4. Dans cette figure, la courbe pleine
et la courbe en pointillés représentent respectivement les courbes de pression statique sans et avec
effet système. La courbe avec effet système est obtenue en ajoutant la perte de pression du composant
pour chaque accroissement du débit, lorsqu’il peut être mesuré ou estimé à partir de la littérature
(par exemple, IDEL'CIK), à la pression statique de la combinaison ventilateur + composant raccordé à
l'aspiration. Cette procédure permet d'évaluer l'effet de l'installation lié à la dégradation de la courbe du
ventilateur elle-même sans tenir compte de la perte de pression du composant.
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ISO/TR 16219:2020(F)

Pour quantifier l'effet système sur l'ensemble de la courbe du ventilateur, la valeur Δq /q est reportée
V1 V1
en fonction du coefficient de résistance du système ξ=qp/ (p étant la pression statique du
fs
V1 fs
1)
ventilateur à q ) à la Figure 5.
V1
Le SEF pour une configuration donnée ventilateur + composant raccordé à l'aspiration est la moyenne
de Δq /q sur l’étendue ξ, présentée en pourcentage dans les résultats. Δq /q est positive lorsque le
V1 V1 V1 V1
débit avec le composant raccordé à l’aspiration est inférieur à celui de la configuration à aspiration libre.
Légende
q débit-volume du ventilateur
V1
p pression statique du ventilateur
fs
1 courbe du ventilateur sans effet système
2 courbe du ventilateur avec effet système
3 tracé du système
Figure 4 — Définition de q et de Δq sur une courbe du système donnée
V1 V1
1) q est soit en cfm ou en m³/s tandis que p est soit en in. wg ou en Pa.
V1 fs
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ISO/TR 16219:2020(F)

Légende
Δq /q chute relative de l’écoulement du débit-volume dans le ventilateur
V1 V1
ξ coefficient de résistance du système
1 courbe d’effet système
Figure 5 — Exemple de chute relative de l’écoulement Δq /q en fonction du coefficient
V1 V1
de résistance du système ξ
L’Article 6 décrit différentes situations menant à des effets système à l’aspiration.
5.2 Effet système au refoulement
L'effet système au refoulement est une mesure des pertes de pression des accessoires situés au
refoulement du ventilateur tels qu'un conduit de refoulement, un coude, un registre de réglage du débit,
un conduit secondaire ou un plénum, en raison d'un écoulement au refoulement non uniforme induit
par le ventilateur et des raccordements inappropriés au refoulement.
La plupart des ventilateurs, pour les applications nécessitant des systèmes raccordés à leur sortie, sont
soumis à essai et évalués pour leur performance avec un conduit de refoulement d’une longueur égale
à 2 à 3 fois celle du “diamètre de conduit équivalent”. Le conduit de refoulement permet de contrôler
la diffusion de l’écoulement au refoulement et d'établir un profil de vitesses uniforme (Figure 6). La
plupart du temps, il n'est pas pratique pour le fabricant de ventilateur de fournir ce type de conduit avec
le ventilateur, toutefois, la performance nominale ne sera pas atteinte à moins qu’un conduit comparable
ne soit inclus dans la conception du système.
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ISO/TR 16219:2020(F)

Légende
1 ventilateur centrifuge
2 arrêt
3 section de passage d'air
4 section de sortie
5 conduit de refoulement
6 ventilateur axial
7 25 % de la longueur effective du conduit
8 50 % de la longueur effective du conduit
9 75 % de la longueur effective du conduit
10 100 % de la longueur effective du conduit
Figure 6 — Profils de vitesses au refoulement d’un ventilateur
Les techniques documentées visant à estimer les pertes de pression d'un composant tel qu'un coude ou
les performances de perte de pression données par le fabricant d'un composant, pour un registre par
exemple, sont basées sur des profils de vitesses d'amont uniformes. La perte de pression ainsi estimée
est appelée la “perte de pression conventionnelle” dans le raccord. À moins que le profil de vitesses
d'amont uniformes ne soit garanti, ces composants subissent des pertes de pression additionnelles.
L'effet système au refoulement est utilisé pour estimer la perte réelle de pression du composant pour
une installation donnée.
L’Article 7 décrit différentes situations menant à des effets système au refoulement. L'effet système
total au refoulement, p (Pa), pour une situation donnée (composant) est défini de la manière suivante:
SE
p = p + p
SE c SEo

p est la perte de pression conventionnelle (Pa);
c
p est la perte de pression additionnelle due à un écoulement non uniforme (Pa).
SEo
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ISO/TR 16219:2020(F)

p peut être exprimée en fonction de l’écoulement par la formule suivante:
SEo
p = C × p
SEo fd2

2
p est la pression dynamique au refoulement du ventilateur 0,5*ρ*(q /A ) ;
fd2 V1 2
3
q est le débit du ventilateur, m /s;
V1
2
A A est la section de sortie du ventilateur, en m ;
2
C est le coefficient d'effet système;
3
ρ est la masse volumique de l’air en kg/m .
L’effet système au refoulement p à chaque débit q doit être ajouté à la courbe du système de
SE V1
conception pour obtenir la courbe réelle du système (Figure 7).
Le coefficient d'effet système C est moyenné tout au long de la courbe du ventilateur pour obtenir ce que
l’on a appelé à l’Article 7 le SEF au refoulement.
P – P = perte de pression conventionnelle du composant au débit de conception
B A
P – P = effet système au refoulement, p , au débit de conception de conception
C B SEo
P – P = perte de pression conventionnelle du composant au débit réel
E D
P – P = effet système au refoulement, p , au débit réel
F E SEo

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ISO/TR 16219:2020(F)

Légende
q débit-volume du ventilateur
V
P pression du ventilateur
1 courbe débit-pression catalogue du ventilateur
2 courbe de perte de pression réelle du système
3 courbe du système avec perte de pression conventionnelle du composant
4 courbe du système sans perte de pression conventionnelle du composant et sans calcul d’effet système
5 pression de conception
6 débit réel
7 débit de conception
Figure 7 — Modification de la courbe de perte de pression du système en raison de l’effet
système au refoulement
Dans certains cas, la perte de pression conventionnelle p ne peut pas être estimée ou n'est pas
c
pertinente, comme par exemple avec des parois latérales situées à proximité de la roue d'un ventilateur
centrifuge de plénum dans l'exemple donné en 7.2.2.2. Dans ce cas, l'effet système est dû à la perturbation
de l’écoulement dans la roue induite par la proximité des parois.
6 Exemples de SEF à l’aspiration
6.1 Introduction
Des exemples d'effets système à l'aspiration sont tirés de différents programmes de recherche dédiés
menés depuis les années 1990. Le laboratoire national britannique pour l’ingénierie (NEL) au Royaume-
Uni a réalisé une étude expérimentale approfondie sur neuf types de ventilateurs et six composants
raccordés à l'aspiration du ventilateur. Un résumé des configurations d’essai et des principaux résultats
obtenus est donné dans les références bibliographiques [3] et [4]. Par ailleurs, plusieurs programmes de
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ISO/TR 16219:2020(F)

recherche ont été financés par l'ASHRAE, avec des essais réalisés dans leur majorité par l'AMCA, pour
quantifier le SEF pour:
[5]
— un ventilateur centrifuge à pales inclinées vers l'arrière - projet de recherche ASHRAE 1216-RP ;
[6]
— un ventilateur centrifuge à pales courbées vers l'avant - projet de recherc
...

TECHNICAL ISO/TR
REPORT 16219
First edition
Fans — System effects and system
effect factors
Ventilateurs — Effet système et facteurs d’effet système
PROOF/ÉPREUVE
Reference number
ISO/TR 16219:2020(E)
©
ISO 2020

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ISO/TR 16219:2020(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2020
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 PROOF/ÉPREUVE © ISO 2020 – All rights reserved

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ISO/TR 16219:2020(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and symbols . 1
4 Origin of fan system effects . 2
5 Definitions of system effect factor (SEF) . 4
5.1 Inlet SEF . 4
5.2 Outlet system effect . 6
6 Examples of inlet SEF . 9
6.1 Introduction . 9
6.2 Axial fans .10
6.2.1 Experimental setups .10
6.2.2 Results .15
6.3 Centrifugal and mixed-flow fans .17
6.3.1 Experimental setups .17
6.3.2 Results .24
7 Examples of outlet SEF .30
7.1 Axial fans .30
7.1.1 General.30
7.1.2 Experimental setups .30
7.1.3 Results .30
7.2 Centrifugal and mixed-flow fans .32
7.2.1 Experimental setups .32
7.2.2 Results .33
8 Reducing system effects .34
8.1 General .34
8.2 Inlet effects .34
8.2.1 General.34
8.2.2 Non-uniform flow . .35
8.2.3 Swirl or vorticity .36
8.2.4 Inlet blockage . . .36
8.3 Outlet effects .39
8.3.1 General.39
8.3.2 Insufficient duct length .39
8.3.3 Outlet obstruction . .40
8.3.4 Non-uniform flow . .40
8.4 Examples of the effects of poor inlet and outlet connections .43
9 Conclusions .44
Annex A (informative) Basic principles on fan performance representation .45
Annex B (informative) Fan system calculation .73
Bibliography .83
© ISO 2020 – All rights reserved PROOF/ÉPREUVE iii

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ISO/TR 16219:2020(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 117, Fans.
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.
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ISO/TR 16219:2020(E)

Introduction
ISO 5801 provides the information for accurately measuring the performance of fans when tested
under standardised laboratory conditions. The ducting where specified ensures a fully developed
symmetrical velocity profile at the fan inlet. There may also be sufficient straight ducting at the fan
outlet to ensure efficient conversion of the distorted velocity profile at the fan outlet to a measurable
stable and homogeneous profile at the measuring station.
This document shows how fan performance is affected by both inlet and outlet connections to it.
System designers must not only look at the ideal performance curve and calculated system pressure
drop but also take into account the losses at the entry and exit points of the fan. These are described in
the document.
The concept of the system effect factor (SEF) was introduced to the fan industry by AMCA in 1973.
Since its inception it has become widely accepted worldwide. In more recent years it has been realized
that the SEF depends not only on the fan type and the fitting geometry but also on the fan design and
manufacturing. Some less efficient fans may sometimes be less sensitive to system effect induced by
poor inlet flow conditions than more efficient fans of the same type.
Furthermore, the origin of the system effect induced by a fitting at the fan inlet is different from the
one due to the same fitting located on the fan outlet. That is why two different definitions of SEF are
proposed in this document according to whether the appurtenance is at the fan inlet or fan discharge.
© ISO 2020 – All rights reserved PROOF/ÉPREUVE v

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TECHNICAL REPORT ISO/TR 16219:2020(E)
Fans — System effects and system effect factors
1 Scope
This document deals with the likely degradation of air performance of fans tested in standardized
airways in accordance with ISO 5801 when compared with the performance of fans tested under actual
site conditions. It deals with the performance of a number of generic types of fan and fittings. The
results given are intended as guidelines and only provide trends, as the system effect depends on the
exact geometry of the fan and disturbing component.
The test data presented in this document are taken from an extensive experimental program conducted
20 years ago by NEL (National Engineering Laboratory, UK), mainly on axial and centrifugal fans.
Data are also taken from several research projects financially supported by ASHRAE, some of them
being carried out in the AMCA laboratory in Chicago, as well as from results published previously by
individual fan manufacturers.
2 Normative references
There are no normative references in this document.
3 Terms, definitions and symbols
No terms and definitions are listed in this document.
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/
The following symbols are used:
Symbol Description SI units I-P units
2 2
A Fan outlet area m ft
2
C System effect (SE) coefficient (see 5.2) Dimensionless Dimensionless
p Conventional pressure loss (see 5.2) Pa in. wg
C
p Fan pressure Pa in. wg
f
p Fan dynamic pressure (see Clause 4) Pa in. wg
fd
p Fan static pressure Pa in. wg
fs
p System effect (see 5.2) Pa in. wg
SE
Additional pressure loss due to non-uni-
p Pa in. wg
SEo
form flow (see 5.2)
3
q Volume flow rate of the fan m /s cfm
V1
S System effect factor Dimensionless Dimensionless
EF
3 0,5
ξ Loss coefficient (see 5.1) (m /s)/(Pa )
3 2
ρ Density of air kg/m lbm/ft
3 2
ρ Standard air density kg/m lbm/ft
std
NOTE  The term “fan dynamic pressure” or “dynamic pressure” is used throughout this document and is
equivalent to the term “velocity pressure” as used in some countries.
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4 Origin of fan system effects
Manufacturers’ fan performance ratings are mostly based on tests carried out in a laboratory under
ideal conditions. Ideal conditions refer to uniform, swirl-free air velocity profiles at fan inlet and outlet,
like those of the test rigs described in ISO 5801 and AMCA 210. In ‘real life’ fan installations, such ideal
conditions may not be present due to improper connection of the fan to the system. Such improper
connections include obstacles at fan inlets and outlets that alter the aerodynamic characteristics of the
fan and lead to deficient performance in relation to catalogue ratings, even when the system pressure
losses have been estimated accurately. The term “system effect” is a measure of this degradation of fan
performance.
The origin of system effect is different at fan outlet and at fan inlet. At the fan outlet, for example in
the case of an improperly connected outlet fitting such as an elbow, damper or duct branch, the system
effect is linked to less-than-optimum non-uniform flow profiles induced by the fan at the entrance to
the fitting (Figure 1). This degraded flow will create more pressure loss across the fitting than would
be the case when measuring the fitting loss assuming uniform homogeneous flow profiles or when
[14]
estimating it from standard handbooks such as the ASHRAE Handbook of Fundamentals .
When the fitting is at the fan inlet, for example an elbow or a fan inlet duct/box (Figure 2), the velocity
profiles at the inlet to the fitting may be uniform and the fitting pressure loss as measured or estimated
from standard handbooks may be valid. However, the flow patterns at the fan inlet (or fitting outlet)
may be disturbed with the presence of a vortex, spin or vena-contracta. This less than optimum flow
condition at fan inlet caused by the fitting will lead to a reorganization of the flow inside the impeller
and therefore a deterioration of fan performance in relation to catalogue ratings. Not only the fan curve
may be affected by this disturbing obstacle but also sometimes, but not always, the fan power curve. A
companion document will be drafted at a later date to show the influence of the inlet obstacles on the
fan power curve for the same configurations of fans and fittings as in this document.
In both cases, the resulting air flow of the fan-system combination deteriorates, but for distinct
physical reasons. For this reason, two different definitions and treatment of fan system effect are
incorporated, depending on whether the fitting is at the fan inlet or fan outlet. It is also recognized
that in some situations, obstacles very close to fan discharge (e.g. side walls at a short distance of a
plenum fan impeller as shown in Figure 20) may also deteriorate fan performance in the same manner
as components located at fan inlet.
Key
1 axial fan
Figure 1 — Non-uniform velocity profiles at fan outlet
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a
Impeller rotation.
Figure 2 — Vortex at fan inlet
An ideal connection to a fan would be one which results in a velocity distribution across the fan inlet
connection plane which is relatively uniformly distributed and without appreciable swirl component,
as shown in Figure 3.

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a
a) Ideal p distribution b) Good p distribution
d d
b
c) Satisfactory p distribution
d

Key
p mean dynamic pressure of the duct flow
d
a
Also satisfactory for flow into fan inlets, but may be unsatisfactory for flow into inlet boxes, may produce swirl
in boxes.
b
More than 75 % of p readings greater than p /10 (unsatisfactory for flow into fan inlets of inlet boxes).
d dmax
Figure 3 — Ideal fan connections
5 Definitions of system effect factor (SEF)
5.1 Inlet SEF
With a component at the fan inlet, the SEF is defined as the relative airflow drop Δq /q along a given
v1 v1
system line as shown in Figure 4. In this figure, the solid curve and the dotted line curve are the static
pressure curves without and with system effect, respectively. The curve with system effect is obtained
by adding the pressure loss of the fitting for each flow rate increment, when it may be measured or
estimated from guidebooks (e.g. IDEL'CIK), to the static pressure of the fan + inlet fitting combination.
This procedure allows for the assessment of the installation effect related to the degradation of the fan
curve itself without accounting for the pressure loss of the fitting.
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To quantify the system effect on the whole fan curve, the quantity Δq /q is plotted versus the system
V1 V1
1)
resistance coefficient ξ=qp/ (p being the fan static pressure at q ) in Figure 5.
fs V1
V1 fs
The SEF for a given fan + inlet fitting configuration is the average of Δq /q over the ξ range, presented
V1 V1
as a percentage in the results. Δq /q is positive when the flow with the inlet fitting is lower than that
V1 V1
of the free inlet configuration.
Key
q volume flow rate of the fan
V1
p fan pressure
f
1 fan curve without system effect
2 fan curve with system effect
3 system line
Figure 4 — Definition of q and Δq on a given system line
V1 V1
1) q is either in cfm or m³/s while p is either in in. wg or Pa.
V1 fs
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Key
Δq /q relative flow drop in volume flow rate of the fan
V1 V1
ξ system resistance coefficient
1 system effect curve
Figure 5 — Example of relative flow drop Δq /q versus system resistance coefficient ξ
V1 V1
Clause 6 describes various situations resulting in inlet system effects.
5.2 Outlet system effect
Outlet system effect is a measure of the pressure losses across fan outlet appurtenances such as an
outlet duct, elbow, volume control damper, duct branch or plenum, due to non-uniform outlet flow
induced by the fan and improper outlet connections.
Most fans, for applications requiring systems connected at their outlets, are tested and rated for
performance with an outlet duct 2 to 3 ‘equivalent duct diameter’ long. The outlet duct helps control the
diffusion of the outlet flow and establish a uniform velocity profile (Figure 6). In most cases, it is not
practical for the fan manufacturer to supply this duct as part of the fan, but rated performance will not
be achieved unless a comparable duct is included in system design.
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Key
1 centrifugal fan
2 cutoff
3 blast area
4 outlet area
5 discharge duct
6 axial fan
7 25 % effective duct length
8 50 % effective duct length
9 75 % effective duct length
10 100 % effective duct length
Figure 6 — Velocity profiles at fan outlet
The techniques documented to estimate pressure losses of a fitting such as an elbow or the published
pressure drop performance from a manufacturer of a fitting such as a damper are based upon uniform
approach velocity profiles. The pressure loss so estimated is referred to as the ‘conventional pressure
loss’ across the fitting. Unless uniform approach velocity profile is ensured, there will be additional
pressure losses across these fittings. Outlet system effect is used to estimate the actual pressure loss
across the fitting in a given installation.
Clause 7 describes various situations resulting in outlet system effects. The total outlet system effect,
p (Pa), for a given situation (fitting) is defined as:
SE
p = p + p
SE c SEo
where
p is conventional pressure loss (Pa);
c
p is additional pressure loss due to non-uniform flow (Pa).
SEo
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p can be expressed as a function of flow by the following formula:
SEo
p = C × p
SEo fd2
where
2
p is dynamic pressure at fan outlet 0,5*ρ*(q /A ) ;
fd2 V1 2
3
q is fan airflow rate, m /s;
V1
2
A is fan outlet area in m ;
2
C is system effect coefficient;
3
ρ is air density in kg/m .
The outlet system effect p at each flow rate q must be added to the design system curve to obtain
SE V1
the actual system curve (Figure 7).
The system effect coefficient C is averaged over the fan curve to obtain what is called the outlet SEF in
Clause 7.
P – P = fitting conventional pressure drop at design flow
B A
P – P = outlet system effect, p , at design flow
C B SEo
P – P = fitting conventional pressure drop at actual flow
E D
P – P = outlet system effect, p , at actual flow
F E SEo

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Key
q fan volume flow rate
V
P fan pressure
1 fan catalogue pressure-flow curve
2 actual system curve
3 system curve with fitting conventional pressure drop
4 system curve without conventional pressure drop and no allowance for system effect
5 design pressure
6 actual flow
7 design flow
Figure 7 — Modification of design system curve due to outlet system effect
In some cases the conventional pressure loss p cannot be estimated or is not relevant, like for instance
c
with side walls close to the impeller of a plenum fan in the example of 7.2.2.2. In this case the system
effect is due to the disturbed flow in the impeller induced by the proximity of the walls.
6 Examples of inlet SEF
6.1 Introduction
Examples of inlet system effect are taken from different dedicated research programs carried out since
the 1990s. The National Engineering Laboratory (NEL) in the UK performed an extensive experimental
study on nine different types of fans and six ductwork fittings at the fan inlet. A summary of the test
configurations and main results obtained is given in References [3] and [4]. Otherwise, several research
programs have been financially supported by ASHRAE in which the tests were performed mainly by
AMCA to quantify the SEF on:
[5]
— a backward inclined/airfoil centrifugal fan – ASHRAE Research Project 1216-RP ;
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[6]
— a forward curved centrifugal fan – ASHRAE Research Project 1272-RP ;
[7]
— two airfoil centrifugal plenum fans – ASHRAE Research Project 1420-TRP ;
[8]
— three sizes of propeller fans of the same series – ASHRAE Research Project 1223-RP .
Finally, a test was done more recently by AMCA on a forward curved centrifugal fan with an inlet 90°
segmented elbow at various orientations.
6.2 Axial fans
6.2.1 Experimental setups
6.2.1.1 NEL
All the tests were performed on a ductwork of D = 630 mm, where D is the duct diameter. A layout of
the test ductwork with a bend connected to the fan inlet is shown in Figure 8. The distance between the
inlet fitting and the fan is varied from 0D, as in Figure 8 to 2D.
Details of the experimental program and measurement procedure are given in Reference [4] and
private reports. The test data used in the present analysis are the performance curves of the fan alone
and fan + inlet fitting and the measured pressure losses of the fittings. All the fan curves, initially based
on total pressure, were transformed into static pressure curves by subtracting the dynamic pressure at
the fan outlet according to ISO 5801.
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Key
1 test fan and fitting
2 throttle
3 auxiliary boost fan
4 silencers
5 flow measurement nozzle
6 flow measurement and control section
7 outlet duct
8 inlet duct
SOURCE Based on content from National Engineering Laboratory (NEL) Fan Connected Ductwork Study for
FETA (FET001) February 1992, reproduced with permission from the Fan Manufacturers Association, FETA UK.
Figure 8 — Test rig for determination of installation effect — Fitting at fan inlet
Table 1 gives the main characteristics of the axial fans tested by NEL while Figure 9 shows views of the
fans, including centrifugal fans. Figure 10 presents sketches of the fittings that were connected to the
fan inlet (or outlet) via transition elements.
They include:
a) rectangular/circular transition, section 800 × 400 → D = 630 mm, length 950 mm;
b) short square bend 90°, section 630 × 630, curvature radius 100 mm;
c) square mitred bend 90°, section 630 × 630, with guide vanes;
d) circular five-piece segmented bend, D = 630 mm;
e) rectangular to rectangular box fitting, section 800 × 400, length 2 400 mm;
f) rectangular splitter silencer, section 800 × 400, length 1 200 mm;
g) banjo connector, section 1 260 × 630, length 1 890 mm.
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Table 1 — Main characteristics of the axial fans tested by NEL
Fan Fan type Blade setting Hub/tip ratio Speed
° rpm
1 tubeaxial 24 0,223 1 440
2 tubeaxial 30 0,223 1 440
3 vaneaxial 24 0,389 1 440
4 vaneaxial 32 0,389 1 440
5 tubeaxial 24 0,389 2 900
6 tubeaxial 32 0,389 2 900
NOTE  All the fans have a diameter of 630 mm.
SOURCE: Based on content from National Engineering Laboratory (NEL) Fan Connected Ductwork Study
for FETA (FET001) February 1992, reproduced with permission from the Fan Manufacturers Association,
FETA UK.
SOURCE Based on content from National Engineering Laboratory (NEL) Fan Connected Ductwork Study for
FETA (FET001) February 1992, reproduced with permission from the Fan Manufacturers Association, FETA UK.
Figure 9 — Views of the NEL test fans
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Key
1 short square bend 90°
2 square mitred bend 90°
3 circular five-piece segmented bend
4 rectangular/circular transition
5 rectangular splitter silencer
6 banjo connector
7 rectangular to rectangular box fitting
SOURC
...

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