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1、BRITISH STANDARD BS EN ISO 12241:1998 Thermal insulation for building equipment and industrial installations Calculation Rules The European Standard EN ISO 12241:1998 has the status of a British Standard ICS 27.220; 91.120.10; 91.140.01 Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 19 12:48:02
2、 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS EN ISO 12241:1998 This British Standard, having been prepared under the direction of the Engineering Sector Board, was published under the authority of the Standards Board and comes into effect on 15 July 1998 BSI 05-1999 ISBN 0 580 29921 X National for
3、eword This British Standard is the English language version of EN ISO 12241:1998. It is identical with ISO 12241:1998. It supersedes the calculation methods given in BS 5422:1990 and BS 5970:1992 which will be amended to remove conflict with this standard, but not withdrawn. The UK participation in
4、its preparation was entrusted by Technical Committee RHE/9, Thermal insulating materials, to Subcommittee RHE/9/1, Thermal insulating materials for use above 0 C, which has the responsibility to: aid enquirers to understand the text; present to the responsible international/European committee any en
5、quiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. A list of organizations represented on this subcommittee can be obtained on request to its secretary. Cross-references At
6、tention is drawn to the fact that CEN and CENELEC Standards normally include an annex which lists normative references to international publications with their corresponding European publications. The British Standards which implement these international or European publications may be found in the
7、BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are resp
8、onsible for their correct application. 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, pages i and ii, the EN ISO title page, page 2, the ISO title page, pages ii to iv, pages
9、 1 to 36 and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Amendments issued since publication Amd. No.DateComments Licensed Copy: sheffieldun sheffieldun, na, Sun N
10、ov 19 12:48:02 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS EN ISO 12241:1998 BSI 05-1999i Contents Page National forewordInside front cover Foreword2 Forewordiv Text of ISO 122411 Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 19 12:48:02 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ii blank Li
11、censed Copy: sheffieldun sheffieldun, na, Sun Nov 19 12:48:02 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN ISO 12241 March 1998 ICS 91.120.00; 91.140.10 Descriptors: See ISO document English version Thermal insulation for building equipment and indu
12、strial installations Calculation rules (ISO 12241:1998) Isolation thermique des quipements du btiment et des installations industrielles Mthodes de calcul (ISO 12241:1998) This European Standard was approved by CEN on 1 January 1998. CEN members are bound to comply with the CEN/CENELEC Internal Regu
13、lations which stipulate the conditions for giving this European Standard the status of a national 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 E
14、uropean Standard exists 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 Central Secretariat has the same status as the official versions. CEN members are the n
15、ational standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. CEN European Committee for Standardization Comit Europen de Normalisation Europi
16、sches Komitee fr Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels 1998 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN ISO 12241:1998 E Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 19 12:48:02 GMT+00:00 2006,
17、 Uncontrolled Copy, (c) BSI EN ISO 12241:1998 BSI 05-1999 2 Foreword The text of the International Standard ISO 12241:1998 has been prepared by Technical Committee ISO/TC 163 “Thermal insulation” in collaboration with Technical Committee CEN/TC 89 “Sanitary appliances”, the secretariat of which is h
18、eld by SIS. 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 September 1998, and conflicting national standards shall be withdrawn at the latest by September 1998. According to the CEN/CENELEC Inte
19、rnal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland
20、 and the United Kingdom. Endorsement notice The text of the International Standard ISO 12241:1998 was approved by CEN as a European Standard without any modification. NOTENormative references to International Standards are listed in Annex ZA (normative). Licensed Copy: sheffieldun sheffieldun, na, S
21、un Nov 19 12:48:02 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 19 12:48:02 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN ISO 12241:1998 ii BSI 05-1999 Contents Page Forewordiv Introduction1 1Scope1 2Normative references2 3Definitions, symbols and ab
22、breviations2 3.1Physical quantities, symbols and units2 3.2Subscripts3 4Calculation methods for heat transfer4 4.1Fundamental equations for heat transfer4 4.2Surface temperature17 4.3Prevention of surface condensation19 5Calculation of the temperature change in pipes, vessels and containers19 5.1Lon
23、gitudinal temperature change in a pipe19 5.2Temperature change and cooling times in pipes, vessels and containers20 6Calculation of cooling and freezing times of stationary liquids20 6.1Calculation of the cooling time for a given thickness of insulation to prevent the freezing of water in a pipe20 6
24、.2Calculation of the freezing time of water in a pipe21 7Thermal bridges22 8Underground pipelines22 8.1Calculation of heat loss (single line)22 9Tables and Diagrams25 Annex A (informative) Comments on thermal conductivity29 Annex B (informative) Examples30 B.1Calculation of the necessary insulation
25、thicknesses for a double layered wall of a firebox30 B.2Heat flow rate and surface temperature of an insulated pipe31 B.3Temperature drop in a pipe31 B.4Temperature drop in a container32 B.5Cooling and freezing times in a pipe33 B.6Underground pipeline33 B.7Required insulation thickness to prevent s
26、urface condensation34 Annex C (informative) Bibliography35 Annex ZA (normative) Normative references to international publications with their relevant European publications36 Figure 1 Temperature distribution in a single layer wall5 Figure 2 Temperature distribution in a multi-layer wall6 Figure 3 T
27、emperature distribution in a single layer hollow cylinder7 Figure 4 Temperature distribution in a multi-layer hollow cylinder8 Figure 5 Temperature distribution in a single layer hollow sphere9 Figure 6 Temperature distribution in a multi-layer hollow sphere10 Figure 7 Temperature distribution in a
28、wall of a duct with rectangular cross section11 Figure 8 The temperature distribution for a multi-layer plane wall in relation to the thermal surface resistance and the thermal resistances of layers16 Figure 9 Underground pipe without insulation23 Figure 10 Underground pipe comprising several concen
29、tric layers,24 Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 19 12:48:02 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN ISO 12241:1998 BSI 05-1999iii Page Table 1 Selection of hcv14 Table 2 Coefficients CA and CB for approximate calculation of total exterior thermal surface coefficient14 Table
30、3 The allowed temperature difference in C between surface and ambient air for different relative humidities at the onset of dew formation25 Table 4 Additional heat losses due to components in a pipeline26 Descriptors: Thermal insulation, buildings, pipelines, fluid pipelines, pipes (tubes), equipmen
31、t, heat transfer, heat losses, rules of calculation. Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 19 12:48:02 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN ISO 12241:1998 iv BSI 05-1999 Foreword ISO (the International Organization for Standardization) is a worldwide federation of national sta
32、ndards 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 or
33、ganizations, 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. Draft International Standards adopted by the technical committees are
34、 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. International Standard ISO 12241 was prepared by Technical Committee ISO/TC 163, Thermal insulation, Subcommittee SC 2, Calculation methods. A
35、nnex A to Annex C of this International Standard are for information only. Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 19 12:48:02 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN ISO 12241:1998 BSI 05-19991 Introduction Methods relating to conduction are direct mathematical derivations from Fo
36、uriers Law of 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 which are mathematically traceable t
37、o Newtons Law 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 avai
38、lable to select 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.
39、 The equations 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 will depend on the accuracy of the input variables. This International Standard contains no guidelines for accurate measurement of an
40、y of the variables. However, it does contain guides which have proven satisfactory for estimating some of the variables for many industrial thermal systems. It should be noted that the steady-state calculations are dependent on boundary conditions. Often a solution at one set of boundary conditions
41、is not sufficient to characterize a thermal system which will operate in a changing thermal environment (process equipment operating year-round, outdoors, for example). In such cases local weather data based on yearly averages or yearly extremes of the weather variables (depending on the nature of t
42、he particular calculation) should be used 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 measure
43、ments and application 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 need for numerous calculations to proper
44、ly model thermal characteristics of any one surface. Furthermore, the heat flow through a surface at any point is a function of several variables which are not directly related to insulation quality. Among others, these variables include ambient temperature, movement of the air, roughness and emissi
45、vity of the heat flow surface, and the radiation exchange with the surroundings (often including a great variety of interest). 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
46、 corresponds to the air temperature, 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 rel
47、iable indicator of insulation 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 precise values of heat energy conservation or (in
48、sulated) surface temperature need not be assured, 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 ap
49、plications of calculating heat flow temperature drop and freezing times in pipes and other vessels. 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, assuming one-dimensional heat flow only. Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 19 12:48:02 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN ISO 12241:1998 2 BSI 05-1999 2 Normative references The following standards c