EN ISO 12241-2008 en Thermal insulation for building equipment and industrial installations - Calculation rules《建筑设备和工业装置的热绝缘 计算规则》.pdf

1、BS EN ISO12241:2008ICS 27.220; 91.120.10; 91.140.01NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBRITISH STANDARDThermal insulation forbuilding equipmentand industrialinstallations Calculation rules (ISO12241:2008)This British Standardwas published under theauthority of the S

2、tandardsPolicy and StrategyCommittee on 31 May 2009 BSI 2009ISBN 978 0 580 56728 5Amendments/corrigenda issued since publicationDate CommentsBS EN ISO 12241:2008National forewordThis British Standard is the UK implementation of EN ISO 12241:2008.It is identical to ISO 12241:2008. It supersedes BS EN

3、 ISO 12241:1998which is withdrawn.The UK participation in its preparation was entrusted to TechnicalCommittee B/540, Energy performance of materials components andbuildings.A list of organizations represented on this committee can be obtained onrequest to its secretary.This publication does not purp

4、ort to include all the necessary provisionsof a contract. Users are responsible for its correct application.Compliance with a British Standard cannot confer immunityfrom legal obligations.EUROPEAN STANDARDNORME EUROPENNEEUROPISCHE NORMEN ISO 12241June 2008ICS 91.140.01; 91.120.10 Supersedes EN ISO 1

5、2241:1998 English VersionThermal insulation for building equipment and industrialinstallations - Calculation rules (ISO 12241:2008)Isolation thermique des quipements de btiments et desinstallations industrielles - Mthodes de calcul (ISO12241:2008)Wrmedmmung an haus- und betriebstechnischenAnlagen -

6、Berechnungsregeln (ISO 12241:2008)This European Standard was approved by CEN on 1 May 2008.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date li

7、sts and bibliographical references concerning such nationalstandards may be obtained on application to the CEN Management Centre or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the respo

8、nsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as theofficial versions.CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,France, Germany, Greece, Hungary, Icela

9、nd, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMIT EUROPEN DE NORMALISATIONEUROPISCHES KOMITEE FR NORMUNGManagement Centre: rue de Stass

10、art, 36 B-1050 Brussels 2008 CEN All rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN ISO 12241:2008: EBS EN ISO 12241:2008EN ISO 12241:2008 (E) 3 Foreword This document (EN ISO 12241:2008) has been prepared by Technical Committee ISO/TC 163

11、“Thermal performance and energy use in the built environment“ in collaboration with Technical Committee CEN/TC 89 “Thermal performance of buildings and building components” the secretariat of which is held by SIS. This European Standard shall be given the status of a national standard, either by pub

12、lication of an identical text or by endorsement, at the latest by December 2008, and conflicting national standards shall be withdrawn at the latest by December 2008. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN and/or CENE

13、LEC shall not be held responsible for identifying any or all such patent rights. This document supersedes EN ISO 12241:1998. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belg

14、ium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. Endorsement notice

15、 The text of ISO 12241:2008 has been approved by CEN as a EN ISO 12241:2008 without any modification. BS EN ISO 12241:2008ISO 12241:2008(E) ISO 2008 All rights reserved iiiContents Page Foreword iv Introduction v 1 Scope . 1 2 Normative references . 1 3 Terms, definitions and symbols 1 3.1 Terms and

16、 definitions. 1 3.2 Definition of symbols . 2 3.3 Subscripts . 3 4 Calculation methods for heat transfer 3 4.1 Fundamental equations for heat transfer. 3 4.2 Surface temperature. 14 4.3 Prevention of surface condensation. 17 4.4 Determination of total heat flow rate for plane walls, pipes and sphere

17、s 20 5 Calculation of the temperature change in pipes, vessels and containers 21 5.1 Longitudinal temperature change in a pipe . 21 5.2 Temperature change and cooling times in pipes, vessels and containers 22 6 Calculation of cooling and freezing times of stationary liquids 22 6.1 Calculation of the

18、 cooling time for a given thickness of insulation to prevent the freezing of water in a pipe. 22 6.2 Calculation of the freezing time of water in a pipe 24 7 Determination of the influence of thermal bridges . 25 7.1 General. 25 7.2 Calculation of correction terms for plane surfaces 26 7.3 Calculati

19、on of correction terms for pipes 26 8 Underground pipelines. 27 8.1 General. 27 8.2 Calculation of heat loss (single line) without channels 27 8.3 Other cases . 29 Annex A (normative) Thermal bridges in pipe insulation 30 Annex B (informative) Projecting thermal bridges of roughly constant cross-sec

20、tion 33 Annex C (informative) Examples 38 Bibliography . 45 BS EN ISO 12241:2008ISO 12241:2008(E) iv ISO 2008 All rights reservedForeword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing Interna

21、tional 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

22、ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical

23、committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to t

24、he 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. ISO 12241 was prepared by Technical Committee ISO/TC 163, Thermal performance and energy use in the built environment, Subco

25、mmittee SC 2, Calculation methods. This second edition cancels and replaces the first edition (ISO 12241:1998), which has been technically revised, including methods to determine the correction terms for thermal transmittance and linear thermal transmittance for pipes that are added to the calculate

26、d thermal transmittance to obtain the total thermal transmittance to calculate the total heat losses for an industrial installation. BS EN ISO 12241:2008ISO 12241:2008(E) ISO 2008 All rights reserved vIntroduction Methods relating to conduction are direct mathematical derivations from Fouriers law o

27、f heat conduction, so international consensus is purely a matter of mathematical verification. No significant difference in the equations used in the member countries exists. For convection and radiation, however, there are no methods in practical use that are mathematically traceable to Newtons law

28、 of cooling or the Stefan-Boltzman law of thermal radiation, without some empirical element. For convection in particular, many different equations have been developed, based on laboratory data. Different equations have become popular in different countries, and no exact means are available to selec

29、t between these equations. Within the limitations given, these methods can be applied to most types of industrial, thermal-insulation, heat-transfer problems. These methods do not take into account the permeation of air or the transmittance of thermal radiation through transparent media. The equatio

30、ns in these methods require for their solution that some system variables be known, given, assumed or measured. In all cases, the accuracy of the results depends on the accuracy of the input variables. This International Standard contains no guidelines for accurate measurement of any of the variable

31、s. However, it does contain guides that have proven satisfactory for estimating some of the variables for many industrial thermal systems. lt should be noted that the steady-state calculations are dependent on boundary conditions. Often a solution at one set of boundary conditions is not sufficient

32、to characterize a thermal system that operates in a changing thermal environment (process equipment operating year-round, outdoors, for example). In such cases, it is necessary to use local weather data based on yearly averages or yearly extremes of the weather variables (depending on the nature of

33、the particular calculation) for the calculations in this International Standard. In particular, the user should not infer from the methods of this International Standard that either insulation quality or avoidance of dew formation can be reliably assured based on minimal, simple measurements and app

34、lication of the basic calculation methods given here. For most industrial heat flow surfaces, there is no isothermal state (no one, homogeneous temperature across the surface), but rather a varying temperature profile. This condition suggests the requirement for numerous calculations to properly mod

35、el thermal characteristics of any one surface. Furthermore, the heat flow through a surface at any point is a function of several variables that are not directly related to insulation quality. Among others, these variables include ambient temperature, movement of the air, roughness and emissivity of

36、 the heat flow surface, and the radiation exchange with the surroundings (which often vary widely). For calculation of dew formation, variability of the local humidity is an important factor. Except inside buildings, the average temperature of the radiant background seldom corresponds to the air tem

37、perature, and measurement of background temperatures, emissivities and exposure areas is beyond the scope of this International Standard. For these reasons, neither the surface temperature nor the temperature difference between the surface and the air can be used as a reliable indicator of insulatio

38、n performance or avoidance of dew formation. Clauses 4 and 5 of this International Standard give the methods used for industrial thermal insulation calculations not covered by more specific standards. In applications where it is not necessary to assure precise values of heat energy conservation or (

39、insulated) surface temperature, or where critical temperatures for dew formation are either not approached or not a factor, these methods can be used to calculate heat flow rates. Clauses 6 and 7 of this International Standard are adaptations of the general equation for specific applications of calc

40、ulating heat flow temperature drop and freezing times in pipes and other vessels. Annexes B and C of this International Standard are for information only. BS EN ISO 12241:2008BS EN ISO 12241:2008INTERNATIONAL STANDARD ISO 12241:2008(E) ISO 2008 All rights reserved 1Thermal insulation for building eq

41、uipment and industrial installations Calculation rules 1 Scope This International Standard gives rules for the calculation of heat-transfer-related properties of building equipment and industrial installations, predominantly under steady-state conditions. This International Standard also gives a sim

42、plified approach for the treatment of thermal bridges. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (includ

43、ing any amendments) applies. ISO 7345, Thermal insulation Physical quantities and definitions ISO 9346, Hygrothermal performance of buildings and building materials Physical quantities for mass transfer Vocabulary ISO 10211, Thermal bridges in building construction Heat flows and surface temperature

44、s Detailed calculations ISO 13787, Thermal insulation products for building equipment and industrial installations Determination of declared thermal conductivity ISO 23993, Thermal insulation for building equipment and industrial installations Determination of design thermal conductivity 3 Terms, de

45、finitions and symbols 3.1 Terms and definitions For the purposes of this document, the terms and definitions given in ISO 7345, ISO 9346, ISO 13787 and ISO 23993 apply. BS EN ISO 12241:2008ISO 12241:2008(E) 2 ISO 2008 All rights reserved3.2 Definition of symbols Symbol Definition Unit A area m2artem

46、perature factor K3C thickness parameter (see 4.2.2) m Crradiation coefficient W/(m2K4) cpspecific heat capacity at constant pressure kJ/(kgK) D diameter m, mmd thickness m, mmH height m h surface coefficient of heat transfer W/(m2K) l length m m mass kg m mass flow rate kg/h P perimeter m q density

47、of heat flow rate W/m2qdlinear density of heat flow rate for ducts W/m qllinear density of heat flow rate W/m R thermal resistance m2K/W Rdlinear thermal resistance of ducts mK/W Rllinear thermal resistance mK/W Rlelinear thermal surface resistance mK/W Rssurface resistance of heat transfer m2K/W Rs

48、phthermal resistance for hollow sphere K/W tfrfreezing time h tvcooling time h twptime until freezing starts h T thermodynamic temperature K U thermal transmittance W/(m2K) Ullinear thermal transmittance W/(mK) Usphthermal transmittance for hollow sphere W/K UBthermal transmittance of thermal bridge

49、 W/(m2K) UBadditional term corresponding to installation-related and/or irregular insulation-related thermal bridges W/(m2K) UTtotal thermal transmittance for plane wall W/(m2K) UT,ltotal linear thermal transmittance W/(mK) UT,sphtotal thermal transmittance for hollow sphere W/K v air velocity m/s BS EN ISO 12241:2008ISO 12241:2008(E) ISO 2008 All rights reserved 3Symbol Definition Unit z, y correction terms for irregular insulation-related thermal bridges z*, y* correction terms for installation-related thermal b