1、| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | BRITISH STANDARD BS EN 305 : 1997 ICS 27.0
2、60.30 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW Heat exchangers Definitions of performance of heat exchangers and the general test procedure for establishing performance of all heat exchangersBS EN 305 : 1997 This British Standard, having been prepared under the directio
3、n of the Engineering Sector Board, was published under the authority of the Standards Board and comes into effect on 15 July 1997 BSI 1997 The following BSI references relate to the work on this standard: Committee reference RHE/30 ENV 305 ISBN 0 580 27624 4 Amendments issued since publication Amd.
4、No. Date Text affected Committees responsible for this British Standard The preparation of this British Standard was entrusted to Technical Committee RHE/30, Heat exchangers, upon which the following bodies were represented: British Refrigeration Association Building Services Research and Informatio
5、n Association Federation of Environmental Trade Associations HEVAC Association Water Heaters Manufacturers AssociationBS EN 305 : 1997 BSI 1997 i Contents Page Committees responsible Inside front cover National foreword ii Foreword 2 Text of EN 305 3ii BSI 1997 BS EN 305 : 1997 National foreword Thi
6、s British Standard has been prepared by Technical Committee RHE/30 and is the English language version of EN 305 : 1997 Heat exchangers Definitions of performance of heat exchangers and the general test procedure for establishing performance of all heat exchangers, published by the European Committe
7、e for Standardization (CEN). EN 305 : 1997 was produced as a result of international discussions in the UK took an active part. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover,
8、 pages i and ii, the EN title page, pages 2 to 14, an inside back cover and a back cover.CEN European Committee for Standardization Comite Europe en de Normalisation Europa isches Komitee fu r Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels 1997 Copyright reserved to CEN members Ref
9、. No. EN 305 : 1997 E EUROPEAN STANDARD EN 305 NORME EUROPE ENNE EUROPA ISCHE NORM January 1997 ICS 27.060.30 Supersedes ENV 305 : 1990 Descriptors: Heat transfer, heat exchangers, definitions, thermodynamic properties, tests, information English version Heat exchangers Definitions of performance of
10、 heat exchangers and the general test procedure for establishing performance of all heat exchangers Echangeurs thermiques De finitions de la performance des e changeurs thermiques et proce dure ge ne rale dessai pour la de termination de la performance de tous les e changeurs thermiques Wa rmeaustau
11、scher Begriffe und allgemeine Festlegungen bei der Pru fung zur Leistungsbestimmung This European Standard was approved by CEN on 1996-12-27. 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 nat
12、ional standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in a
13、ny other language made by translation under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Ice
14、land, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.Page 2 EN 305 : 1997 BSI 1997 Foreword This European Standard has been prepared by Technical Committee CEN/TC 110, Heat exchangers, the secretariat of which is held by BSI. This European St
15、andard supersedes ENV 305 : 1990. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by July 1997, and conflicting national standards shall be withdrawn at the latest by July 1997. According to the CEN/
16、CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and
17、 the United Kingdom. Contents Page Foreword 2 Introduction 3 1 Scope 3 2 Normative references 3 3 Symbols and abbreviations 3 3.1 Roman letters 3 3.2 Greek letters 3 3.3 Subscripts 4 4 Definitions and meaning of performance 4 4.1 Basic terms 4 4.2 Parameters characterizing heat exchangers 5 4.3 Ener
18、gy balance 5 4.4 Heat transfer coefficients 5 4.5 Heat transfer surface 6 5 Performance parameters 6 5.1 Characteristic entities 6 5.2 Ratios 8 6 General information on test procedures 11 6.1 Introduction 11 6.2 Test conditions 12 6.3 Test procedure 12 Annexes A (informative) Energy balance 13 B (in
19、formative) Heat transfer coefficients 13Page 3 EN 305 : 1997 BSI 1997 1) Kelvin (K) is used for absolute temperature and temperature difference. Introduction This European Standard is one of a series of European Standards dedicated to heat exchangers. This standard provides the manufacturer with inf
20、ormation for presenting performance characteristics for a heat exchanger in varying operating situations. These characteristics form the basis for determination of the exchangers condition, both when it is new and after having been in operation for some time. This standard also supplies the purchase
21、r of the heat exchanger with the information necesary for specifying and selecting the product which best meets his needs. This standard is also intended to be used in connection with type approval testing to serve as a source of information for certification, if required. 1 Scope This European Stan
22、dard specifies general terms and calculations used in determining performance of heat exchangers including related theory and general test procedure. This European Standard applies to heat exchangers classified according to the general arrangement of heat transfer specified by heat transfer surface
23、types of 4.1 and 4.2 of prEN 247 : 1996. This European Standard applies when referenced by the various branch application standards. The specific application European Standards shall be the prime reference documents. 2 Normative references This European Standard incorporates by dated or undated refe
24、rence, provisions from other publications. These normative references are cited at the appropriate places in the text and the publications are listed below. For dated references, any subsequent amendments or revisions to these publications only apply to this European Standard when incorporated in it
25、 by amendment or revision. For undated references the latest edition of the publication referred to applies. prEN 247 : 1996 Heat exchangers Terminology 3 Symbols and abbreviations 3.1 Roman letters Symbol Quantity Units A heat transfer surface area m 2 c specific heat capacity J/(kgK) C cleanliness
26、 factor F correction factor for LMTD h specific enthalpy J/kg H enthalpy J k overall heat transfer coefficient W/(m 2 K) LMTD logarithmic mean temperature difference K NTU number of heat transfer units p pressure Pa P heat power W q rate of flow kg/s, m 3 /s R resistance (thermal) (m 2 K)/W T absolu
27、te temperature K 1) SM surface margin % t temperature C y ratio of specific heat capacity ratings 3.2 Greek letters a heat transfer coefficient W/(m 2 K) d wall thickness m difference e efficiency (fin) h efficiency (thermal) l thermal conductivity W/(mK) r density kg/m 3Page 4 EN 305 : 1997 BSI 199
28、7 3.3 Subscripts 1 primary side 2 secondary side 11 inlet conditions on primary side 12 outlet conditions on primary side 21 inlet conditions on secondary side 22 outlet conditions on secondary side av average c clean d dynamic f fouling fin finned i inlet loss loss of heat m mass max. maximum (theo
29、retical) min. minimum M mechanical o outlet op operational p pressure s static t temperature T thermal v volume W wall tot total 4 Definitions and meaning of performance 4.1 Basic terms For the purposes of this standard, the following definitions apply. 4.1.1 fluid Water, air, steam or any liquid, g
30、as or vapour used for transfer of thermal energy (heat). Two or more types of fluid may be combined and solid particles may be present. 4.1.2 primary fluid The warmer fluid (heat source). 4.1.3 secondary fluid The cooler fluid (heat sink). 4.1.4 mixture Fluid including two or more components in the
31、same state of phase. 4.1.5 two-phase (multi-phase) fluid Fluid including one or more components in different state of phase. 4.1.6 heat exchanger A device designed to transfer heat between two physically separated fluids. 4.1.7 condenser Heat exchanger in which vapour is liquified by removal of heat
32、. 4.1.8 evaporator Heat exchanger in which liquid is vaporized by absorbing heat from the medium being cooled. 4.1.9 series-produced heat exchanger Heat exchanger assembled from volume manufactured parts and which conforms to a specific duty at stated conditions. 4.1.10 heat exchanger performance Th
33、ermal performance of a heat exchanger is its capacity expressed in terms of some or all of the following items: heat flow rate; fluid flow rate; temperature; temperature difference; pressure drop; heat transfer coefficient; that can be determined by measurement or calculated from measured parameters
34、. 4.1.11 categories of heat exchanger Classification of heat exchanger types based on design criteria of physical criteria or both. The categories of heat exchanger in this standard are classified according to the general arrangement of heat transfer specified by heat transfer surface types in 4.1 o
35、f prEN 247 : 1996. 4.1.12 recuperative heat exchange Heat transfer from the primary fluid to a secondary fluid, either direct through a wall or indirect through an intermediate medium. 4.1.13 regenerative heat exchange Heat transfer from the primary fluid to the secondary fluid by means of mass accu
36、mulating heat which the two fluids flow through alternatively. 4.1.14 heating Raising the temperature of a secondary fluid without changing its state of phase. 4.1.15 cooling Lowering the temperature of a primary fluid without changing its state of phase.Page 5 EN 305 : 1997 BSI 1997 4.1.16 condensi
37、ng Liquefying a vapour by removing latent heat. 4.1.17 boiling Vaporizing a liquid by supplying latent heat. 4.1.18 melting Liquefying a solid by supplying heat. 4.1.19 solidifying Phase change in a liquid to solid state by removing heat. 4.1.20 fouling Deposition of a layer of unwanted material of
38、low thermal conductivity on the heat exchanger surface. 4.1.21 pressure drop Loss in total pressure between the inlet and the outlet including channels for flow distribution to and from the heat transfer surface. 4.1.22 standard inlet point The inlet point considered most representative of each heat
39、 exchanger is chosen by the manufacturer or according to the condition for the installation. 4.1.23 standard outlet point The outlet point considered most representative of each heat exchanger is chosen by the manufacturer or according to the condition for the installation. 4.2 Parameters characteri
40、zing heat exchangers 4.2.1 Derived parameters When using this standard as a basis for reporting of performance, the parts contained in the European Standards for various branch applications shall be used. Table 1. Parameters used in reporting of performance Name of parameters Designation Clause refe
41、rred to Pressure drop Dp 5.1.2.3 Logarithmic mean temperature difference LMTD 5.1.4.1 Terminal temperature difference Dt o 5.1.4.2 Overall heat transfer coefficient k 5.1.5.1 Fouling resistance R f 5.1.6a) Heat transfer surface margin SM 5.1.6b) Cleanliness factor C f 5.1.6c) Heat power P 5.1.5 Numb
42、er of heat transfer units NTU 5.2.2 Temperature efficiency h t 5.2.1.3 4.2.2 Operating conditions The performance parameters of the heat exchanger shall be defined at operating conditions such as: temperature (inlet and/or outlet temperature of primary and secondary fluids); flowrate (mass flow of p
43、rimary and secondary fluids and any intermediate flows necessary); pressure (inlet of primary and secondary fluids); pressure drop (of primary and secondary fluids); type of media; physical properties and chemical composition of the fluids involved (at standard inlet and/or outlet points); clean or
44、fouled heat transfer surfaces; demands on auxiliary equipment (e.g. vents, level controls, pumps, fans, etc.); demands on environment (e.g. ambient temperature, humidity, pollution, etc.); operating frequency (for regenerative heat exchangers). 4.2.3 Rating The performance of the heat exchanger shal
45、l be referred to the rating condition of the operating conditions. In order to predict or project the performance at other operating conditions, relevant data may be presented in the form of curves, tables or equations. 4.2.4 Test condition A condition where the system has been stabilized and reprod
46、ucible values are attainable. For detailed information on stability criteria, reference is made to the relevant chapters in the European Standard on methods of measurement and the European Standards on various branch applications of this European Standard. 4.3 Energy balance A balance comparing tota
47、l energy input and total energy output of a heat exchanger. This balance should be included in all tests on heat exchangers to verify measured results. The comparison should agree within limits specified for each particular application. For detailed equations, see annex A. 4.4 Heat transfer coeffici
48、ents Heat transfer shall be characterized by different types of heat transfer coefficients, expressing the rate of heat flow per unit heat transfer surface area and unit temperature difference. Heat transfer coefficients shall be given separately for the primary and secondary flows or as an overall
49、heat transfer coefficient. The overall heat transfer coefficient combines the effects of convection, conduction and radiation between the two flows and the heat transfer surface of the heat exchanger.Page 6 EN 305 : 1997 BSI 1997 2) Heat is transferred from a higher to a lower temperature level in accordance with the second thermodynamic law. The significance of this is that the temperature difference is the driving force. If no temperature difference exists no heat transfer will oc
