BS EN 12898-2001 Glass in building - Determination of the emissivity《建筑物玻璃 辐射能力的测定》.pdf

1、BRITISH STANDARD BS EN 12898:2001 Glass in building Determination of the emissivity The European Standard EN 12898:2001 has the status of a British Standard ICS 81.040.20 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBS EN 12898:2001 This British Standard, having been prepare

2、d under the direction of the Sector Committee for Building and Civil Engineering, was published under the authority of the Standards Committee and comes into effect on 15 April 2001 BSI 04-2001 ISBN 0 580 37308 8 National foreword This British Standard is the official English language version of EN

3、12898:2001. The UK participation in its preparation was entrusted by Technical Committee B/520, Glass and glazing in building, to Subcommittee B/520/4, Properties and glazing methods, which has the responsibility to: A list of organizations represented on this subcommittee can be obtained on request

4、 to its secretary. Cross-references The British Standards which implement international or European publications referred to in this document may be found in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the

5、BSI Standards Electronic Catalogue. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. aid e

6、nquirers to understand the text; present to the responsible European committee any enquiries 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. Summary of pages This document compr

7、ises a front cover, an inside front cover, the EN title page, pages 2 to 13 and a back cover. The BSI copyright date displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. Date CommentsEUROPEANSTANDARD NORMEEUROPENNE EUROPISCHENORM EN1289

8、8 January2001 ICS81.040.20 Englishversion GlassinbuildingDeterminationoftheemissivity VerredanslaconstructionDterminationdelmissivit GlasimBauwesenBestimmungdesEmissionsgrades ThisEuropeanStandardwasapprovedbyCENon1January2001. CENmembersareboundtocomplywiththeCEN/CENELECInternalRegulationswhichstip

9、ulatetheconditionsforgivingthisEurope an Standardthestatusofanationalstandardwithoutanyalteration.Uptodatelistsandbibliographicalreferencesconcernings uchnational standardsmaybeobtainedonapplicationtotheManagementCentreortoanyCENmember. ThisEuropeanStandardexistsinthreeofficialversions(English,Frenc

10、h,German).Aversioninanyotherlanguagemadebytra nslation undertheresponsibilityofaCENmemberintoitsownlanguageandnotifiedtotheManagementCentrehasthesamestatusasthe official versions. CENmembersarethenationalstandardsbodiesofAustria,Belgium,CzechRepublic,Denmark,Finland,France,Germany,Greece, Iceland,Ir

11、eland,Italy,Luxembourg,Netherlands,Norway,Portugal,Spain,Sweden,SwitzerlandandUnitedKingdom. EUROPEANCOMMITTEEFORSTANDARDIZATION COMITEUROPENDENORMALISATION EUROPISCHESKOMITEEFRNORMUNG ManagementCentre:ruedeStassart,36B1050Brussels 2001CEN Allrightsofexploitationinanyformandbyanymeansreserved worldw

12、ideforCENnationalMembers. Ref.No.EN12898:2001EPage2 EN12898:2001 Contents Page Foreword3 1Scope 4 2Symbols 4 3Termsanddefinitions 4 4Briefoutlineoftheproceduretodeterminecorrectedemissivity 6 5Spectralnormalreflectanceandtransmittancemeasurements6 6Calculationoftotalnormalreflectance,correctedemissi

13、vityandtotalnormaltransmittance.8 7Diffusereflectancemeasurements . 9 8Testreport 9 AnnexA(normative)Tablesfordeterminingtotalnormalreflectanceandtotalcorrectedemissivity 11 AnnexB (informative)Procedurestoimprovetheaccuracyofspectralnormalreflectance measurements .12 Bibliography .13Page3 EN12898:2

14、001 Foreword ThisEuropeanStandardhasbeenpreparedbyTechnicalCommitteeCEN/TC129“Glassinbuilding“, thesecretariatofwhichisheldbyIBN. ThisEuropeanStandardshallbegiventhestatusofanationalstandard,eitherbypublicationofan identicaltextorbyendorsement,atthelatestbyJuly2001,andconflictingnationalstandardssha

15、llbe withdrawnatthelatestbyJuly2001. AccordingtotheCEN/CENELECInternalRegulations,thenationalstandardsorganizationsofthe followingcountriesareboundtoimplementthisEuropeanStandard:Austria,Belgium,CzechRepublic, Denmark,Finland,France,Germany,Greece,Iceland,Ireland,Italy,Luxembourg,Netherlands, Norway

16、,Portugal,Spain,Sweden,SwitzerlandandtheUnitedKingdom.Page4 EN12898:2001 1Scope ThisEuropeanStandardspecifiesaprocedurefordeterminingtheemissivityatroomtemperatureof thesurfacesofglassandcoatedglass. Theemissivityisnecessaryfortakingintoaccountheattransferbyradiationfromsurfacesatthe standardtempera

17、tureof283KinthedeterminationoftheUvalueandofthetotalsolartransmittance ofglazingaccordingto 1 to 5 . Theprocedure,beingbasedonspectrophotometricregularreflectancemeasurementsatnearnormal incidenceonnoninfraredtransparentmaterials,isnotapplicabletoglazingcomponentswithatleast oneofthefollowingcharact

18、eristics: a)withroughorstructuredsurfaceswheretheincidentradiationisdiffuselyreflected; b)withcurvedsurfaceswheretheincidentradiationisregularlyreflectedatanglesunsuitableto reachthedetectorwhileusingregularreflectanceaccessories; c)infraredtransparent. However,itmaybeappliedwithcautiontoanyglazingc

19、omponentprovideditssurfacesareflatand nondiffusing(see3.6)anditisnoninfraredtransparent(see3.7). 2Symbols totalcorrectedemissivityat283K n totalnormalemissivityat283K E readingofthespectrophotometerwiththesampleplacedonthesamplesupportofthe reflectanceaccessory E 0 theinstrumentreadingwithoutplacing

20、anythingonthesamplesupport E st theinstrumentreadingwiththereferencemirrorreplacingthesample R n totalnormalreflectanceat283K R n ( ) spectralnormalreflectance R n,st spectralnormalreflectanceofthereferencemirror T n ( ) spectralnormaltransmittance T n totalnormaltransmittanceat283K 3Termsanddefinit

21、ions ForthepurposesofthisEuropeanStandard,thefollowingtermsanddefinitionsapply: 3.1infrared 5 mto50 mspectralrange. 3.2 emissivity ratiooftheenergyemittedbyagivensurfaceatagiventemperaturetothatofaperfectemitter(black bodywithnormalandcorrectedemissivity=1,0)atthesametemperature.Page5 EN12898:2001 N

22、OTETwodifferentdefinitionsofemissivityshouldtheoreticallybeusedtodescriberadiation exchangebetween: a)glasssurfacesfacingeachotherinmultipleglazing(effectiveemissivity) b)aglasssurfacefacingaroom(hemisphericalemissivity). However,inpracticenumericaldifferenceswerefoundtobenegligiblysmall(see 6 ).Thu

23、s correctedemissivity isusedtodescribebothtypesofheatexchangewithaclose approximation. 3.3 regular(specular)reflectance reflectanceaccordingtothelawsofgeometricaloptics,withoutdiffusion. 3.4 diffusereflectance reflectancenotcontaininganyregularcomponent,duetoroughsurfacesand/ortransparentmaterials c

24、ontaininginhomogeneousparticles. 3.5 hemisphericalreflectance thesumofregularanddiffusereflectance. 3.6 nondiffusingglazingcomponent glazingcomponentwithadiffusereflectance,measuredatthenearinfraredwavelengthof2m, 0,05(seeclause7). NOTEThepurposeofthismeasurementistoensurethatthesampleisnondiffusing

25、inthe measurementrange.Diffusereflectancemeasurementsintheinfraredrangearedifficultto perform. 3.7 noninfraredtransparentglazingcomponent glazingcomponentwithatotalnormaltransmittanceat283K,measuredspectrophotometrically, 0,05. 3.8 referencemirror referencematerialwhosespectralregularreflectanceistr

26、aceabletoastandardmaterialcertifiedbya metrologicallaboratory.Page6 EN12898:2001 4Briefoutlineoftheproceduretodeterminecorrectedemissivity Theprocedurefordeterminingthecorrectedemissivityofcoatedglasssurfacesincludesthefollowing steps: a)thespectralregularreflectanceofanoninfraredtransparentglazingc

27、omponentatnearnormal incidence,R n ( ),shallbedeterminedwithaninfraredspectrophotometerintherange (5to50)m(seeclause5); b)totalnormalreflectanceat283K, R n ,shallbecalculatedusingtheintegrationprocedure specifiedinclause6fromthecorrespondingspectralreflectancevaluesmeasuredaccordingto stepa); c)tota

28、lnormalemissivity, n ,shallbecalculatedfromthetotalnormalreflectanceasspecified inclause6; d)thecorrespondingcorrectedemissivity, ,shallbedeterminedbymultiplyingnormalemissivity bytheratio, / n ,giveninTableA.2. NOTE1Thecorrectedemissivity,calculatedfromthenormalemissivitywiththehelpofa multiplicati

29、vecorrectionfactor,takesintoaccounttheeffectoftheangulardistributionof emissivityintheheattransfercalculationsofglazingaccordingto 1 to 5 . NOTE2Boththenormalandthecorrectedemissivityaretotalemissivitiesat283K,i.e.they areintegratedovertherelevantspectralrangeusingasaweightingfunctionPlancks radiati

30、onfunctionforablackbodyat283K(see 7 ). Foruncoatedsodalimeglasssurfacesorforsodalimeglasssurfaceswithcoatingswhichhaveno effectsontheemissivitythecorrectedemissivitytobeusedinthecalculationsspecifiedin 1 to 5 shallbe0,837(see 8 ).Forallotherglazingmaterialsorcomponentsitshallbemeasured. NOTE3Withrea

31、sonableconfidence = 0,837canbeusedforuncoatedborosilicateglass andglassceramics(see 8 ). NOTE4Fortemperaturesincludedintherange253to313Kemissivityisnotstrongly dependentonthetemperature(see 8 and 9 ). 5Spectralnormalreflectanceandtransmittancemeasurements 5.1Samplepreparation Sampleswithasizesuitabl

32、eforbeinginsertedintothesamplecompartmentorplacedonthe reflectanceaccessoryshallbeobtainedbycuttingordrilling.Indoingso,careshallbetakentoensure thattheportionofthecoatedsurfaceprobedbytheinstrumentbeamisfreeofdamageoranysurface contamination. Theproceduresrecommendedbytheproducerforstoringthesample

33、sandcleaningtheirsurfaces shallbefollowed. Thesampleshallbesupportedinasuitablewaytoensurethatthemeasuringspotduring transmittanceandreflectancemeasurementsfallsonaflatpart.Page7 EN12898:2001 5.2Spectralnormalreflectancemeasurements Thespectralregularreflectancecurveofthesampleatnearnormalincidenceb

34、etween(5and50)m shallbedeterminedwithaninfraredspectrophotometerequippedwithaspecularreflectance accessoryatnearnormalincidence. 5.2.1Testapparatus Thefollowingequipmentshallbeusedforthemeasurements: aspectrophotometercoveringthespectralrange5 mto50 m; areferencemirror(freeofsurfacescratchesandconta

35、mination,see 7 , 9 and 10 )whose spectralregularreflectanceatnearnormalincidence R n,st ( )shallbetraceabletoastandard materialcertifiedbyametrologicallaboratory; aspecularreflectanceaccessoryconsistingofasuitablearrayofmirrorsandasamplesupport. Whentheaccessoryisplacedinthesamplecompartmentofthespe

36、ctrophotometerandthe sample(orreferencemirror)placedonthesamplesupport,theinstrumentbeamreachesthe detectorafterbeingspecularlyreflectedonthesurfaceofthesample(referencemirror)atan angleofincidence 10. 5.2.2Measurement Thespectralregularreflectancecurveofthesampleatnearnormalincidenceshallbedetermin

37、edwith therelativemethod.Thefollowingmeasurementsarerequiredtodeterminethespectralnormal reflectanceofthesample R n ( i )ateachwavelength i reportedinTableA.1: E theinstrumentreadingwiththesampleplacedonthesamplesupportofthereflectance accessory; E st theinstrumentreadingwiththestandardreplacingthes

38、ample; E 0 theinstrumentreadingwithoutplacinganythingonthesamplesupport. Ateachwavelength i thesamplereflectance R n ( i )shallbecalculatedasfollows: i st n, 0 st 0 i n R E E E E R (1) with R n,st ( i )=spectralnormalreflectanceofthereferencemirroratthewavelength i . NOTEMetrologicallaboratoriesdete

39、rminetheabsolutereflectancebycomparingtheenergy ofthebeamreflectedfromthesampletothatoftheincidentbeamorwiththehelpofadouble reflectionaccessorycalled“VW”or“Strongtype”(see 10 ).Commercialversionsofsuch devicesexistbuttheirconstructionisfarshortofthecarefullayoutoftheoriginalversion.Their accuracyis

40、criticallydependentonalignmentandbeamcharacteristics(sizeanddivergence)Page8 EN12898:2001 andisdifficulttocontrolinconjunctionwithcommercialspectrophotometers.Theyshouldbe usedonlywithgreatcautionandunderthesupervisionofametrologicallaboratory. 5.2.3Accuracy Theaccuracyisestimatedtobeoftheorderof0,0

41、2,expressedasabsoluteuncertaintyofregular reflectance(see 7 ). NOTEInannexBinformationonprocedurestoimprovethemeasurementaccuracyisgiven. 5.3Transmittancemeasurements Glazingcomponentsincludingatleastoneglassplatearenotinfraredtransparentanddonotrequest transmittancemeasurement. Forglazingcomponents

42、notincludingglassorcoatedglassthespectralregulartransmittancecurveof thesampleatnormalincidencebetween5mand50mshallbedeterminedwithaninfrared spectrophotometerbyplacingitinthesamplecompartmentperpendicularlytothebeam. 6Calculationoftotalnormalreflectance,correctedemissivityandtotalnormaltransmittanc

43、e 6.1Totalnormalreflectance Totalnormalreflectance, R n ,atatemperatureof283Kshallbedeterminedfromthespectral reflectancecurvebytakingthemathematicalaverageofspectralreflectance, R n ( ),measuredatthe 30wavelengths( i )giveninTableA.1. 30 i 1 i i n n R 30 1 R (2) SuchwavelengthsareselectedatthecentreofwavelengthintervalsforwhichtheenergyofPlancks radiationfunctionforablackbodyat283Kisconstant(see 7 ). 6.2Emissivity Totalnormalemissivity n at283Kisgivenby n n 1 R (3) NOTE1Theuncertaintyr