FprEN 308

Heat exchangers - Test procedures for establishing performance of air to air heat recovery components

This document specifies methods to be used for testing of air-to-air heat recovery components (HRC). The main purpose of the HRC is to exchange heat between exhaust air and supply air in order to save energy, which results in
—   preheat or heat, and/or
—   precool or cool
supply air in ventilation systems or air conditioning systems. Optionally HRC can exchange air humidity between exhaust and supply air. The HRC contains the heat exchangers and all necessary features and auxiliary devices for the exchange of sensible heat and (if available) air humidity between exhaust air and supply air. The HRC will be installed in casings or ducts. If fans are part of the test unit, the effect of the fan power on the measured values will be corrected.
This document specifies procedures and input criteria required for tests to determine the performance of a HRC at one or several test conditions, each of them with continuous and stationary air flows, air temperatures and humidities at both inlet sides. Three different test types are covered:
—   Test type A, Laboratory testing of HRC installed in test casings (A1) or a HRC sections (A2);
—   Test type B, Laboratory testing of HRC installed in non-residential ventilation units  in design configuration;
—   Test type C, On-site (field) testing of HRC in non-residential ventilation units (C1) or a HRC sections (C2) in operation configuration.
This document is applicable to recuperators, regenerators, and HRC with intermediary heat transfer medium.
This document prescribes test methods for determining:
1)   the temperature and humidity efficiency,
2)   the pressure drop of exhaust air and supply air sides,
3)   possible internal leakages; exhaust air transfer ratio (EATR) and outdoor air correction factor (OACF),
4)   external leakages and
5)   auxiliary energy used for the operation of the HRC.
HRC using heat pumps are not covered by this document.

Wärmeaustauscher - Prüfverfahren zur Bestimmung der Leistungskriterien von Luft/Luft-Wärmerückgewinnungsanlagen

Dieses Dokument legt Verfahren für die Prüfung von Luft-Luft-Wärmerückgewinnungskomponenten (HRC) fest. Der Hauptzweck der HRC besteht in dem Wärmeaustausch zwischen Fortluft und Zuluft, um Energie zu sparen. Dies führt zu
—   Vorerwärmung oder Erwärmung und/oder
—   Vorkühlung oder Kühlung von
Zuluft in Belüftungssystemen oder Klimaanlagen. Optional kann die HRC Luftfeuchtigkeit zwischen Fortluft und Zuluft austauschen. Die HRC enthält die Wärmeaustauscher und alle notwendigen Funktionen und Hilfsgeräte für den Austausch sensibler Wärme und (sofern verfügbar) Luftfeuchtigkeit zwischen Fortluft und Zuluft. Die HRC wird in Gehäusen oder Kanälen installiert. Wenn Ventilatoren Teil des Prüfgeräts sind, wird die Auswirkung der Ventilatorenleistung auf die Messwerte korrigiert.
Dieses Dokument legt Verfahren und Eingangskriterien für Prüfungen zur Bestimmung der Leistung einer HRC bei einer oder mehreren Prüfbedingungen fest, jeweils mit kontinuierlichen oder stationären Luftströmen, Lufttemperaturen und Feuchtewerten an beiden Eingangsseiten. Drei verschiedene Prüfarten werden behandelt:
—   Prüfart A, Laborprüfung von in Prüfgehäusen (A1) oder HRC-Abschnitten (A.2) installierten HRC;
—   Prüfart B, Laborprüfung von in Nichtwohnungsbelüftungsgeräten  in Bemessungskonfiguration installierten HRC;
—   Prüfart C, Vor-Ort-Prüfung (Feldprüfung) von HRC in Nichtwohnungsbelüftungsgeräten (C1) oder HRC-Abschnitten (C2) in Betriebskonfiguration.
Dieses Dokument gilt für Rekuperatoren, Regeneratoren und HRC mit intermediärem Wärmeübertragungsmedium.
Dieses Dokument schreibt Prüfverfahren für die Bestimmung:
1)   des Temperatur- und Feuchtewirkungsgrads;
2)   des Druckabfalls auf der Fortluft- und Zuluftseite;
3)   möglicher Innenleckage, des Fortluftübertragungsverhältnisses (EATR) und des Außenluft-korrekturfaktors (OACF);
4)   von Außenleckage und
5)   der für den Betrieb der HRC verwendeten Hilfsenergie vor.
HRC, die Wärmepumpe verwenden, werden in diesem Dokument nicht behandelt.

Échangeurs thermiques - Procédures d'essai pour la détermination de la performance des composants de récupération de chaleur air/air

Le présent document précise les méthodes à utiliser pour les essais sur les composants de récupération de chaleur air-air (HRC). L'objectif principal du HRC est d'échanger la chaleur entre l'air extrait et l'air neuf afin d'économiser l'énergie, ce qui se traduit par
—   le préchauffage ou chauffage, et/ou
—   le pré-refroidissement ou refroidissement
de l'air fourni dans les systèmes de ventilation ou de climatisation. Le cas échéant, les HRC peuvent échanger de l'humidité de l'air entre l'air extrait et l'air neuf. Le HRC contient les échangeurs thermiques et l'ensemble des fonctions et dispositifs auxiliaires nécessaires à l'échange de chaleur sensible et (si disponible) d'humidité de l'air entre l'air extrait et l'air neuf. Les HRC seront installés dans des enveloppes ou des conduits. Si les ventilateurs font partie de l'unité d'essai, l'effet de la puissance du ventilateur sur les valeurs mesurées sera corrigé.
Le présent document précise les procédures et les critères d'entrée requis pour les essais visant à déterminer la performance d'un HRC dans une ou plusieurs conditions d'essai, chacune d'entre elles ayant des flux d'air, des température et taux d'humidité de l'air continus et stationnaires des deux côtés d'entrée. Trois types d'essais différents sont traités :
—   Type d'essai A, essais en laboratoire du HRC installé dans des enveloppes d'essai (A1) ou dans des sections (A2) de HRC ;
—   Type d'essai B, essais en laboratoire du HRC installé dans des unités  de ventilation non résidentielles en configuration de conception ;
—   Essai de type C, essai sur site (sur le terrain) du HRC dans des unités de ventilation non résidentielles (C1) ou dans des sections (C2) de HRC en configuration de fonctionnement.
Le présent document s'applique aux récupérateurs, régénérateurs et HRC avec fluide intermédiaire.
Le présent document décrit des méthodes d'essai pour déterminer :
1)   le rendement en température et en humidité,
2)   la chute de pression côtés air extrait et air neuf,
3)   les fuites internes éventuelles ; le rapport de transfert d'air extrait (EATR) et le facteur de correction d'air extérieur (OACF),
4)   les fuites externes, et
5)   l'énergie auxiliaire utilisée pour le fonctionnement du HRC.
Les HRC utilisant des pompes à chaleur ne sont pas couverts par le présent document.

Prenosniki toplote - Preskusni postopki za ugotavljanje lastnosti naprav za prenos toplote zrak/zrak in dimni plini/zrak

General Information

• Status: Not Published
• ICS: 27.060.30 - Boilers and heat exchangers
• Technical Committee: CEN/TC 110 - Heat exchangers
• Drafting Committee: CEN/TC 110/WG 6 - Revision of EN 308
• Current Stage: 6055 - CEN Ratification completed (DOR) - Publishing
• Due Date: 13-Sep-2021
• Completion Date: 13-Sep-2021
• Mandate: M/BC/CEN/87/5 - Standardization request concerning heat exchangers
• Ref Project: kSIST FprEN 308:2021 - Heat exchangers - Test procedures for establishing performance of air to air and flue gases heat recovery devices

RELATIONS

• Revised: EN 308:1997 - Heat exchangers - Test procedures for establishing performance of air to air and flue gases heat recovery devices
• Effective Date: 15-May-2019

Standards Content (sample)

SLOVENSKI STANDARD
oSIST prEN 308:2020
01-maj-2020

Prenosniki toplote - Preskusni postopki za ugotavljanje lastnosti naprav za prenos

toplote zrak/zrak in dimni plini/zrak

Heat exchangers - Test procedures for establishing performance of air to air and flue

gases heat recovery devices

Wärmetauscher - Prüfverfahren zur Bestimmung der Leistungskriterien von Luft-Luft-

Wärmrückgewinnungs-komponenten

Echangeures thermique - Procedures d’essai pour la determination de la performance

des recuperateurs de chaleur air/air
Ta slovenski standard je istoveten z: prEN 308
ICS:
27.060.30 Grelniki vode in prenosniki Boilers and heat exchangers
toplote
oSIST prEN 308:2020 en,fr,de

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

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oSIST prEN 308:2020
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oSIST prEN 308:2020
DRAFT
EUROPEAN STANDARD
prEN 308
NORME EUROPÉENNE
EUROPÄISCHE NORM
May 2020
ICS Will supersede EN 308:1997
English Version
Heat exchangers - Test procedures for establishing
performance of air to air and flue gases heat recovery
devices

Echangeures thermique - Procedures d'essai pour la Wärmetauscher - Prüfverfahren zur Bestimmung der

determination de la performance des recuperateurs de Leistungskriterien von Luft-Luft-

chaleur air/air Wärmrückgewinnungs-komponenten

This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee

CEN/TC 110.

If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations

which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other

language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC

Management Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,

Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and

United Kingdom.

Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are

aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without

notice and shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2020 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 308:2020 E

worldwide for CEN national Members.
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oSIST prEN 308:2020
prEN 308:2020 (E)
Contents Page

European foreword ...................................................................................................................................................... 4

Introduction .................................................................................................................................................................... 5

1 Scope .................................................................................................................................................................... 6

2 Normative references .................................................................................................................................... 6

3 Terms and definitions ................................................................................................................................... 7

3.1 Air categories ................................................................................................................................................... 7

3.2 Thermal performance characteristics .................................................................................................... 8

3.3 Leakage and mass flow ............................................................................................................................... 12

3.4 Pressure ........................................................................................................................................................... 16

3.5 General terms and definitions ................................................................................................................. 17

3.6 Categories of heat recovery components ............................................................................................. 18

3.7 Test types ......................................................................................................................................................... 20

3.8 Uncertainty of measurement .................................................................................................................... 22

3.8.1 Expression of uncertainty .......................................................................................................................... 22

4 Symbols and abbreviations ....................................................................................................................... 23

4.1 Symbols ............................................................................................................................................................ 23

4.2 Subscripts ........................................................................................................................................................ 25

4.3 Abbreviations ................................................................................................................................................. 26

5 Test requirements ........................................................................................................................................ 26

5.1 Specification of the HRC .............................................................................................................................. 26

5.2 Precision classes ........................................................................................................................................... 26

5.3 Measurement equipment ........................................................................................................................... 27

5.3.1 Uncertainties of probes and measurement instruments ............................................................... 27

5.3.2 Temperature measuring plane ................................................................................................................ 28

5.3.3 Measurement of pressure drop and pressure differences ............................................................ 30

5.3.4 Determination of the air flow rates ........................................................................................................ 30

5.4 Test in laboratory ......................................................................................................................................... 31

5.4.1 General.............................................................................................................................................................. 31

5.4.2 Atmospheric pressure ................................................................................................................................. 31

5.4.3 Ambient conditions ...................................................................................................................................... 31

5.4.4 Test casings ..................................................................................................................................................... 32

5.5 Leakages ........................................................................................................................................................... 33

5.5.1 General.............................................................................................................................................................. 33

5.5.2 Internal leakage test .................................................................................................................................... 33

5.6 Specific HRC categories ............................................................................................................................... 33

5.6.1 Category HRC2a ............................................................................................................................................. 33

6 Test procedures ............................................................................................................................................. 34

6.1 General.............................................................................................................................................................. 34

6.1.1 Overview .......................................................................................................................................................... 34

6.1.2 Leakage test .................................................................................................................................................... 34

6.1.3 Pressure drop test ........................................................................................................................................ 37

6.1.4 Conditions for leakage and pressure drop measurements ........................................................... 37

6.1.5 Efficiency test ................................................................................................................................................. 38

6.1.6 Calculation of the efficiency ...................................................................................................................... 43

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6.2 Test type A ....................................................................................................................................................... 46

6.2.1 Preparation of the HRC ............................................................................................................................... 46

6.2.2 Leakage test .................................................................................................................................................... 46

6.2.3 Pressure drop tests ...................................................................................................................................... 48

6.2.4 Efficiency test ................................................................................................................................................. 48

6.2.5 Calculation of the efficiency ...................................................................................................................... 49

6.3 Test type B ....................................................................................................................................................... 49

6.3.1 Setting of the AHU ......................................................................................................................................... 49

6.3.2 Setting of the design operation point .................................................................................................... 49

6.3.3 Leakage test .................................................................................................................................................... 51

6.3.4 Pressure drop test ........................................................................................................................................ 52

6.3.5 Efficiency test ................................................................................................................................................. 52

6.3.6 Calculation of the efficiency ...................................................................................................................... 52

6.4 Test type C ....................................................................................................................................................... 52

6.4.1 Preparation of the HRC ............................................................................................................................... 52

6.4.2 Leakage test .................................................................................................................................................... 53

6.4.3 Efficiency tests ............................................................................................................................................... 53

6.4.4 Pressure drop test ........................................................................................................................................ 54

7 Test Results ..................................................................................................................................................... 54

7.1 Description of HRC concept, geometry and features ....................................................................... 54

7.1.1 General ............................................................................................................................................................. 54

7.1.2 Face air velocity ............................................................................................................................................. 54

7.1.3 Plate heat exchanger ................................................................................................................................... 54

7.1.4 Rotary HRC ...................................................................................................................................................... 55

7.1.5 HRC with intermediary heat transfer medium .................................................................................. 55

7.1.6 Other constructions ..................................................................................................................................... 55

7.2 Leakage............................................................................................................................................................. 55

7.3 Efficiency .......................................................................................................................................................... 56

7.3.1 Temperature and humidity efficiency .................................................................................................. 56

7.3.2 Electric power input and speed ............................................................................................................... 56

7.3.3 Heat balance and precision class ............................................................................................................ 56

7.4 Pressure drop ................................................................................................................................................ 56

7.5 Other indications .......................................................................................................................................... 57

7.6 Reporting of values and precision .......................................................................................................... 57

7.7 Test report ...................................................................................................................................................... 58

Annex A (informative) Testing equipment ......................................................................................................... 59

Annex B (informative) Deviation of different humidity definitions .......................................................... 66

Annex C (normative) Uncertainty of measurement ........................................................................................ 67

Annex D (informative) Estimation of EATR ........................................................................................................ 72

Annex E (normative) Simplified test setup for static internal leakage .................................................... 74

Annex F (informative) Alternative method for OACF measurement ......................................................... 75

Annex G (informative) Overviews of test procedures .................................................................................... 77

Bibliography ................................................................................................................................................................. 81

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oSIST prEN 308:2020
prEN 308:2020 (E)
European foreword

This document (prEN 308:2020) has been prepared by Technical Committee CEN/TC 110 “Heat

exchangers”, the secretariat of which is held by DIN.
This document is currently submitted to the CEN Enquiry.
This document will supersede EN 308:1997.

This edition includes the following significant technical changes with respect to EN 308:1997:

— Scope: flue gas heat recovery devices are no more included.

— In addition to laboratory tests of heat recovery components (HRC), laboratory tests for HRC fitted

into air handling units and on-site tests of HRC are defined.
— Different precision classes for tests are defined.

— Leakage testing has been refined. Exhaust air transfer ration (EATR) and outdoor air correction

factor (OACF) are implemented.

— Correction of the sensible and latent efficiency due to leakages and bad heat balance are

implemented.

— Several terms and definitions are changed, e.g. categories of heat recovery components.

EN 13053 refers to EN 308 regarding the test setup and the test procedure. EN 13053 is a standard

harmonized with the Commission Regulation (EU) 12353/2014 [6].
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oSIST prEN 308:2020
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Introduction

This document specifies methods for the performance testing of air-to-air heat recovery components

(HRC) used in ventilation systems. This document does not contain any information on air handling

units, ductwork and components of air distribution, which are covered by other European Standards.

The document applies for laboratory and in on-site testing. Further it applies to different purposes of

tests, which can be e.g. certification of products, acceptance of installed products, market surveillance

or quality tests of manufacturers. These different applications do not require the same precision of

measurements results. Therefore, different precision classes are defined. Table 1 gives informative

examples for the application of the different test types and precision classes. For low quality products,

low quality installations and/or simplified testing, a ‘not classified’ precision class can occur for all test

types.

Table 1 — Examples for the application of the different test types and precision classes

Examples for the application for precision class
Test Type
Precision class P1 Precision class P2 Precision class P3 not classified
(high precision) (medium precision) (low precision)

Test type A — certification of — internal tests, e.g. for — special test points — not intended

products R&D under extreme use
HRC installed in a test
conditions
casing or HRC-section — quality tests before
market launch — test of functionality
Tested in laboratory

Test type B — test under ideal — certification of — internal tests, e.g. — not intended

conditions with products for R&D use
HRC installed in an AHU
high-quality
— quality tests before — test of functionality
Tested in laboratory
products
market launch
Test type C — not intended use, — test under ideal — typical test — test of
but possible under conditions in real conditions in real functionality
HRC installed in an AHU
ideal conditions systems systems
or in duct work of an
with high-quality
installed ventilation
products and
system
laboratory-like test
Tested on-site
equipment

The HRC is installed in an AHU (air handling unit) by the manufacturer of the AHU.

Customers and manufacturers are free to define the aspired precision class for testing of their products,

but it will be taken into account that the available precision class depends on the test conditions, the

HRC itself, the measurement equipment and the environment conditions.

This document is one of a series of European Standards dedicated to heat exchangers.

NOTE 1 Testing procedure of residential ventilation units, RVU’s, is covered by EN 13141-7 and EN 13141-8.

NOTE 2 EN 13053 deals with non-residential ventilation units, NRVU’s, specifically Air Handling Units (AHU’s).

For testing of the heat recovery, EN 13053 refers to EN 308.
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oSIST prEN 308:2020
prEN 308:2020 (E)
1 Scope

This document specifies methods to be used for testing of air-to-air heat recovery components (HRC).

The main purpose of the HRC is to exchange heat between exhaust air and supply air in order to save

energy, which results in
— preheat or heat, and/or
— precool or cool

supply air in ventilation systems or air conditioning systems. Optionally HRC can exchange air humidity

between exhaust and supply air. The HRC contains the heat exchangers and all necessary features and

auxiliary devices for the exchange of sensible heat and (if available) air humidity between exhaust air

and supply air. The HRC will be installed in casings or ducts. If fans are part of the test unit, the effect of

the fan power on the measured values will be corrected.

This document specifies procedures and input criteria required for tests to determine the performance

of a HRC at one or several test conditions, each of them with continuous and stationary air flows, air

temperatures and humidities at both inlet sides. Three different test types are covered:

— Test type A, Laboratory testing of HRC installed in test casings (A1) or a HRC sections (A2);

— Test type B, Laboratory testing of HRC installed in non-residential ventilation units in design

configuration;

— Test type C, On-site (field) testing of HRC in non-residential ventilation units (C1) or a HRC sections

(C2) in operation configuration.

This document is applicable to recuperators, regenerators, and HRC with intermediary heat transfer

medium.
This document prescribes test methods for determining:
1) the temperature and humidity efficiency,
2) the pressure drop of exhaust air and supply air sides,

3) possible internal leakages; exhaust air transfer ratio (EATR) and outdoor air correction factor

(OACF),
4) external leakages and
5) auxiliary energy used for the operation of the HRC.
HRC using heat pumps are not covered by this document.
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.

EN 1886, Ventilation for buildings - Air handling units - Mechanical performance
Definition according Commission Regulation (EU) No 1253/2014 [6]
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oSIST prEN 308:2020
prEN 308:2020 (E)

EN 13053:2019, Ventilation for buildings - Air handling units - Rating and performance for units,

components and sections
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

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

— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at http://www.iso.org/obp
3.1 Air categories
3.1.1
exhaust air inlet
air to be exhausted from the application, before entering the HRC
Note 1 to entry: In ventilation systems, this air is usually called extract air.
Note 2 to entry: See Figure 1.
Key
11 Exhaust air inlet
12 Exhaust air outlet
21 Supply air inlet
22 Supply air outlet
HRC Heat recovery component
C Casing

NOTE Figure 1 shows the definition of the air flow categories in heat recovery components (HRC).

Figure 1 — Air categories
3.1.2
exhaust air outlet

air in exhaust condition, intended to be blown back to the environment, after leaving the HRC

Note 1 to entry: See Figure 1.
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oSIST prEN 308:2020
prEN 308:2020 (E)
3.1.3
supply air inlet
air intended for the application, before entering the HRC

Note 1 to entry: In ventilation systems, this air is usually called outdoor air. Sometimes this air does not come

directly from outdoor (preheated space, ground heat exchanger, etc.)
Note 2 to entry: See Figure 1.
3.1.4
supply air outlet
air intended for the application, after leaving the HRC
Note 1 to entry: See Figure 1.
3.2 Thermal performance characteristics
3.2.1
temperature efficiency
t,efy

transfer of sensible heat from exhaust to supply air, with correction of the temperature increase of the

supply air outlet caused by the EATR and a correction in case of a bad heat balance

Note 1 to entry: The determination is according to 6.1.6.

Note 2 to entry: This term shall be used to describe the performance characteristic of a HRC for sensible heat.

Note 3 to entry: No definitions of temperature efficiency on the exhaust-air side are included. If data on the

exhaust-air side is required, conditions can be calculated by heat and mass balances, considering leakage and

EATR.

Note 4 to entry: The temperature efficiency depends on the mass flow and on the mass flow ratio between the

supply air flow and the exhaust air flow.
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3.2.2
temperature gross efficiency
t,gro

temperature difference on the supply air side divided by the temperature difference between exhaust

air inlet and supply air inlet

Note 1 to entry: The temperature gross efficiency is calculated as in Formula (1).

θθ−
22 21
η = (1)
t,gro
θθ−
11 21
where
θ is temperature of exhaust air inlet, in °C;
θ is temperature of supply air inlet, in °C;
θ is temperature of supply air outlet, in °C.

Note 2 to entry: The temperature gross efficiency does not regard internal or external leakages or heat flow

through the casing. The temperatures θ , θ and θ can differ from measured values, see 6.1.6.2.

11 21 22

Note 3 to entry: In Regulation (EU) 1253/2014 [6], the same equation is used. There, the definition is called

‘thermal efficiency of a non-residential HRS (η )’ and shall be measured under dry reference conditions, with

t_nrvu

balanced mass flows, an indoor-outdoor air temperature difference of 20 K, excluding thermal heat gain from fan

motors and from internal leakages.
3.2.3
temperature net efficiency
t,net

net transfer of sensible heat from exhaust to supply air, with correction of the temperature change of

the supply air outlet caused by the EATR
Note 1 to entry: The temperature net efficiency is calculated as in Formula (2).
θθ−⋅EATR
22 11
1− EATR
η = (2)
t net
θθ−
11 21
where
EATR
is exhaust air transfer ratio;
θ is temperature of exhaust air inlet, in °C;
θ is temperature of supply air inlet, in °C;
θ is temperature of supply air outlet, in °C.

Note 2 to entry: The temperature net efficiency does not regard external leakages or heat flow through the casing.

The temperatures θ , θ and θ can differ from measured values, see 6.1.6.2.
11 21 22

Note 3 to entry: Temperature net efficiency calculation is required if EATR is determined (see 5.5.2)

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3.2.4
temperature effectiveness
t,efs

temperature gross efficiency, multiplied with the ratio of the mass flow rate of supply air outlet to the

minimum mass flow rate of supply outlet or exhaust air inlet
Note 1 to entry: The temperature effectiveness is calculated as in Formula (3).
q ⋅θθ−
( )
m22 22 21
η = (3)
t,efs
q ⋅θθ−
( )
m,min 11 21
where
is mass flow rate of supply air outlet, in kg/s
m22

is minimum mass flow rate, either of supply air outlet or exhaust air inlet, in kg/s

m,min
q = min qq,
( )
m,min m22 m11
θ is temperature of exhaust air inlet, in °C
θ is temperature of supply air inlet, in °C
θ is temperature of supply air outlet, in °C

Note 2 to entry: The temperature effectiveness describes the ratio of the effective sensible heat transfer from the

exhaust air side to the supply air side compared with the theoretical possible sensible heat transfer.

3.2.5
humidity efficiency
x,efy

transfer of latent heat from exhaust to supply air, with correction of the humidity change of the supply

air outlet caused by the EATR and a correction in case of a bad heat balance
Note 1 to entry: The humidity efficiency is de
...