oSIST prEN 18208:2025

SLOVENSKI STANDARD
01-september-2025
Enofazni toplotni izmenjevalniki tekočina-tekočina - Preskusni postopek za
določanje zmogljivosti
Liquid-to-liquid single-phase heat exchangers - Test procedure for determining
performance
Einphasen-flüssig/flüssig Wärmetauscher - Prüfverfahren zur Bestimmung der
Leistungskriterien
Echangeurs monophasiques liquide/liquide - Procédure d'essai pour la détermination de
la performance
Ta slovenski standard je istoveten z: prEN 18208
ICS:
27.060.30 Grelniki vode in prenosniki Boilers and heat exchangers
toplote
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
EUROPEAN STANDARD
NORME EUROPÉENNE
EUROPÄISCHE NORM
July 2025
ICS 27.060.30
English Version
Liquid-to-liquid single-phase heat exchangers - Test
procedure for determining performance
Echangeurs monophasiques liquide/liquide - Einphasen-flüssig/flüssig Wärmetauscher -
Procédure d'essai pour la détermination de la Prüfverfahren zur Bestimmung der Leistungskriterien
performance
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, Türkiye 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
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 18208:2025 E
worldwide for CEN national Members.

Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Symbols and abbreviations . 8
5 Performance of liquid-to-liquid heat exchangers . 10
5.1 Typical quantities . 10
5.1.1 Derived quantities . 10
5.1.2 Rated conditions . 10
5.2 Hydraulic performance . 12
5.3 Thermal performance . 12
5.3.1 Energy balance . 12
5.3.2 Heat transfer rate . 14
5.3.3 Heat transfer coefficients . 14
5.3.4 Heat transfer surface . 14
5.3.5 Analytical calculation methods . 15
6 Test principle . 21
6.1 Test procedures . 21
6.1.1 Test bench acceptance criteria . 21
6.1.2 Test acceptance criteria . 23
6.1.3 Test conditions . 25
6.2 Measurements and instrumentation . 26
6.2.1 General. 26
6.2.2 Measurements . 26
6.2.3 Acceptable amplitude of fluctuations . 27
6.2.4 Overall uncertainties . 27
6.2.5 Liquid quality . 29
6.3 Test analysis . 29
6.3.1 General. 29
6.3.2 Transposition of new/replacement heat exchanger test results to reference conditions . 30
6.3.3 Transposition of tests results from heat exchangers already in use under reference
conditions . 31
6.4 Test report . 33
Annex A (informative) Calculation of thermal performance uncertainty k.A.F. according to LMTD
method . 34
Annex B (informative) Test report template . 35
Annex C (informative) Example of test . 37
Bibliography . 44

European foreword
This document (prEN 18208:2025) 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.
Introduction
This document is designed to support a series of European standards dedicated to heat exchangers.
This document provides manufacturers and users with the information needed to present the
thermohydraulic performance characteristics of a heat exchanger. These characteristics form the basis
for evaluating the state of a heat exchanger, whether it is new/a replacement, or already in operation.
This document also provides a performance-based acceptance test procedure for a liquid-to-liquid single-
phase heat exchanger (sensor calibration, acknowledgement of uncertainties, standardization of physical
properties of liquids) and the possible transpositions under various rated conditions.
The customer's technical specification, referred to in this document, defines or adapts the level of
tolerance. It also defines thermal performance acceptance criteria. Examples are provided in Annex C.
Underlying assumption of this document is that the liquid is a Newtonian fluid in turbulent conditions.
This document may be adapted for other liquids or conditions, as agreed by parties involved in the
performance test.
1 Scope
This document defines the general terms and the calculations used to determine the thermohydraulic
performance of heat exchangers. It includes the general test procedure and related theories.
This document is intended to be used for acceptance-testing heat exchangers in test facilities such as
laboratories, manufacturer test facilities and final installation site.
This document specifies three acceptance levels:
— level 1 for minimum tolerances;
— level 2 for nominal tolerances;
— level 3 for maximum tolerances;
This document constitutes an application-specific standard in line with EN 305 and EN 306.
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 247, Heat exchangers — Terminology
EN 305, Heat exchangers — Definitions of performance of heat exchangers and the general test procedure
for establishing performance of all heat exchangers
EN 306, Heat exchangers — Methods of measuring the parameters necessary for establishing the
performance
EN ISO 5167 (all parts), Measurement of fluid flow by means of pressure differential devices inserted in
circular cross-section conduits running full
ISO/TR 12767, Measurement of fluid flow by means of pressure differential devices — Guidelines on the
effect of departure from the specifications and operating conditions given in ISO 5167
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 247 and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp/
— IEC Electropedia: available at https://www.electropedia.org/
3.1
liquid
any type of liquid, such as water, used to transfer thermal energy (heat)
Note 1 to entry: There can be a combination of two or more types of liquids, all in the same phase state (single-
phase liquid).
3.2
primary liquid
hottest liquid, which serves as a heat source
3.3
secondary liquid
coolest liquid, which serves as a heat sink
3.4
mixture
liquid with two or more elements, all in the same phase state
3.5
heat exchanger
device designed to transfer heat between two physically separated liquids
3.7
thermohydraulic performance of a heat exchanger
heat exchanger thermohydraulic performance that can be established by measuring, or can be calculated
using measured parameters, and is expressed according to one or more of the following elements:
— temperature of primary/secondary liquid;
— flow rate of primary/secondary liquid;
— pressure of primary/secondary liquid;
— temperature difference;
— heat transfer coefficient;
— heat transfer rate transferred by primary liquid / captured by secondary liquid;
— pressure drops;
— fouling factors.
Note 1 to entry: These elements are identified per EN 305 and may be established by measuring per EN 306.
3.8
heat exchanger categories
classification of heat exchanger types based on design criteria, physical criteria, or a mix of the two
3.9
heating
temperature increase of a secondary liquid that does not change its phase state
3.10
cooling
temperature decrease of a primary liquid that does not change its phase state
3.11
fouling
deposit of a layer of unwanted materials entailing/causing resistance to the heat transfer
3.12
plugging
obstruction of one or more openings/channels in a heat exchanger where no primary or secondary liquid
can circulate, resultin
...