1、 ASHRAESTANDARD PROJECT COMMITTEE74-1988Stephen J. Treado, ChairmanRichard W. DixonTamami KusudaLouis FMasonickASHRAESTANDARDS COMMITTEE 1987-88Byron W. Engen, ChairmanDon G. Virgin, Vice ChairmanF. Leslie BrownDavid R. ConoverCharles E. DorganErnest C. DowlessTamami KusudaRalph D. LahmonR. Michael
2、MartinDennis E. MillerJim L. Heldenbrand, Manager of StandardsSPECIAL NOTEWilliam R. McCluneyGeorge PReed, 111Robert L. Van DyckHerbertPhillipsJulian E. SjordalHarold E. StraubKevin Y. TeichmanWilliam K. ThomasA. Grant WilsonJohn 1. WoodworthGeorgeS. YamamotoDavid S. Butler, COHans O. Spauschus, EXO
3、This National Voluntary Consensus Standard wasdeveloped under the auspices of the American Society ofHeating, RefrigeratingandAir-Conditioning Engineers(ASHRAE).Consensusisdefinedas“substantial agree-mentreachedbyconcernedinterestsaccordingtothejudgrnentofadulyappointedauthority, afteraconcertedatte
4、mpt at resolving objections. Consensus implies much more thanthe concept ofasingle majority but notnecessarily unanimity.“ Thisdefinitionisaccording totheAmerican National Standards Institue (ANSI)ofwhichASHRAE is a member.ASHRAE obtains consensus through participation of its national and internatio
5、nal members, associatedsocieties and public review.ASHRAE Standardsare prepared bya ProjectCommittee appointed specifically for the purpose ofwritingtheStandard.TheProjectCommitteeChairmanand Vice-ChairmanmustbemembersofASHRAE; whileothermembersmayor may notbe members, all mustbetechnically qualifie
6、d inthesubjectareaofthe Standard.Everyeffort is made to balance theconcerned interests on all ProjectCommittees.The Manager ofStandards of ASHRAE should be contacted for:a. interpretation of thecontents ofthisStandard.b. participation in the next reviewofthe Standard.c. offeringconstructive criticis
7、mfor improvingthe Standard,d. permission to reprint portions of theStandard.ASHRAE INDUSTRIAL ADVERTISING POLICYON STANDARDSASHRAEStandardsareestablishedtoassistindustryandthepublicbyoffering auniformmethodoftestingfor ratingpurposes, bysuggestingsafepracticesindesigningand installingequipment, bypr
8、oviding pro-perdefinitonsofthis equipmentand by providing otherinformation whichmayservetoguidetheindustry.ThecreationofASHRAEStandardsisdetermined bytheneedforthem, andconformancetothem iscom-pletely voluntary.In referringtothisStandardandin markingof equipmentandin advertising, noclaim shall be ma
9、de,either stated or implied, that theproduct has been approved by ASHRAE.DISCLAIMERASHRAE usesitsbest effortsto promulgate standardsfor the benefitofthe public in light of available in-formationandacceptedindustrypractices. However;ASHRAE doesnotguarantee, certifyor assurethesafetyorperformance of a
10、ny products, componentsor systemstested, designed, installed or operatedin accordancewith ASHRAEs standards or that any testsconducted under its standards will be non-hazardous orfreefrom risk.CONTENTSSections Page1. Purpose . . ., . . . . . . . . . . . . . . . . ., . . . . . . . . . . . . . . . . .
11、 . .32. Scope . . . . . . ., ., . . . . . ., . ., . , . . . . .33. Definitions . ., . . , . . . , . . . . . . . . . . . . . . . ., . . . . . 4. Apparatus . . ., . , . . . . . ., . . . . . ., . . . . . . . ., ., . . 5. Test Specimens , . ., . . . . . . . . . . . . . . . ., . . ., . , . . . . . ., . .
12、 . . . , . . . . . . . . . .86, Testing Procedure , . . . . . , . . . . . . . . . . . . . . . ., . . . , ., . , . . . . . , . , . . . . . . . . . . .97, Reporting Test Results . ., . . ., . . . . . . . ., . . . . . . . . . . . ., . . . . . . ., . ., . . . . . ., . . . . . . .118. Precision (2) sensi
13、tivity that is isotropicexceptfor the usual cosine response with incident angle; and (3)output linear to within 201o from 0 to 1000 W/mz orcalibrationcurvesaccurate to within 2010 over the sameranage. Additional desirable characteristics are relativelyshort-timeconstants ofafew secondsand good tempe
14、ra-ture stability.4.3.3.2 The pyranometer shall be located so that thesensing thermopile (not the dome) is centered approxi-mately2in. (50mm) below theplaneoftherimofthebox.Although the pyranometers have a 180 view angle, whenplaced as described the field angle to the midpoint of theedges ofthe test
15、 specimen is approximately 157, while tothe diagonal ofthe specimen it is 164.4.3.3.3 Forpyranometers withthermal control shieldshaving high reflectance (e.g., the Eppley P.S.P orequivalent) it is important that the reflection from thepyranometerback toward thesheet material under test beminimized.T
16、hiscanbe donebycoveringthe shieldwith a nonreflec-ting material orbymounting the pyranometer outside theenclosure with only the dome and sensor element projec-tingintothebox. Mountingthepyranometeroutside oftheenclosure alsoreduces the heating load andcoolingrequire-ments for the pyranometer.* 3M EC
17、P244 or ECP91 reflective filmsorequivalent, plateglass, ormirrored acrylic have been found acceptable for this.* Asprayed coatingofNextel blockvelvet(101-C10)available from3MCompany; Parsons Blackavailable fromEppley Laboratories, Newport,Rl;Krylon Flat Black;orequivalent, have all been foundsatisfa
18、ctory forthispurpose. Also,alining of opaque blackvelvet clothsuch as availablefrom photographic suppliers is suitable.ASHRAE STANDARD 74-1988rFLR -.51A. Specularmirror, 500 mm x 50mm.B. Nonreflecting, black bottom. Nontransmittinglouvers ormultiplelayersofgrill cloththat allowaircirculationintothe
19、enclosure are preferable.C. Pyranometer.D. Support shelf for pyranometer. The height oftheshelf will depend on the pyranometer used.E. Semicircular disk 538 mm diameter out of 3/4-in.plywood.F. Semicircular tracker with scale.G. Lip of flange turned up 20 mm to help supportspecimens.H. 50 mm flange
20、bent out ofsheet metal or cut fromwood. Top surfaceispainted black to preventlightentering enclosureduetomultiple refelctionsfromaround thespecimen edges.J. Standard2x2wood framing, 75 mmlong (bottomto center of hole).K. Rectangular, 3/4-in. plywood, 500 x 75 mm.L. %i-in.x 2-in. carriage bolt withwi
21、ng nut and washer.M. 3/4-in. from pipe.N. U-bolts.P. Primarytrackingaxis, alignedparallel toearthsaxisof rotation. The axis shall make ananglewith thevertical equaltothelocallatitudeand pointtowardthe North Star.Q. C-clamp attached to arm to lock equatorial angleduring measurement.R. Vertical suppor
22、t postapproximately 1 m long. Madefrom standard 2 x 6 lumber.Fig. l Apparatus consisting of enclosure, detector, and equatorial mount which has been found acceptable for measuring solartransmittanceofsheetmaterials.Themajority ofthepieces arecutfromstandard 2x4, 2x6and3/4-in. plywoodconstructionmate
23、rials.6 ASHRAE STANDARD 74-1988I. Semicircle with scaleA) Semicircle with 143 mm radius cut out of150x300mm pieceof /2- to 3/4-in. plywood.B) Tape with 1 cm scale attached to inside ofsemicircle.C) Thin opaque sheet (preferably metal) with3 mm aperature centered above semicircle.-a displacementofthe
24、 light beam comingthrough the aperature of 1 cm onthecir-cumference ofthe semicircle equals 4misalignment. This tracker is convenientfor determining angles for offnormalin-cidencemeasurements.II. 12.7 mm (/z-in.) ID pipe by 195 mm (7.67-in.)long.- realign when direct beam from thesolardiskno longer
25、traverses thepipe.III. 9 mm diameterrod by 500mmlongcenteredon80 mm diameterwhite disk.-realign when shadow ofrod falls outside ofwhite disk.Fig. 2 Alignmentdevicesforenclosure. Thedimensions arechosento provide 4limits ondeviations fromnormal to thesun. InB and Ccare must be taken to mount the rod
26、orpipe perpendicular to the surface of the enclosure.ASHRAE STANDARD 74-1988 74.4 Instrumentationfor ProcedureD, directmeasurementofluminoustransmittance.The apparatusto beused inthisstandard practice shall be as described in 4.3, with theexceptionthatthesensing elementof4.3.3 shallbereplacedbythe s
27、ensing elementdescribed as follows:4.4.1 The sensing element shall be a photometer (illu-minance meter) consistingofasuitableradiationdetector(such as a silicon photovoltaic device or multiplierphototube), a phototopic filter, and a diffusing element.The filter shall bedesigned sothatthespectral res
28、ponseofthe photometer veryclosely matches thatofthe standardhuman observer, as specifiedbythe C.I.E. photopicspec-tral luminousefficiency functionfound in Reference. Theresponse ofthe photometer at wavelengthX, divided byitsresponse at 555nm,shalldepart fromthespectral luminousefficiencyofthe standa
29、rd human observeratwavelength Aby no morethan2% forallwavelengths between 390and750nm. Photometerresponse shallbeessentiallyzeroout-side this range.The response of the photometer to uniform, col-limated incident radiation at an angle 8 of incidence indegrees, divided byitsresponse at normal incidenc
30、e (B =zerodeg)shall depart fromthecosineof0byno morethan0/18 percent*Thediffusing elementanddetectorelectronicsshallbedesigned sothatthe voltage(orcurrent) output ofthe sen-soris proportional to hemispherical illuminance incidentupon it. Thephotometershall be located inside theboxsothat its entrance
31、aperture(thediffusingelement)iscenteredapproximately2in. (50 mm) belowtheplaneoftherim ofthe box. Other instructions of4.3 shall be closelyfollowed.4.5 Instrumentation for Procedure E, direct reflectancemeasurements.4.5.1 Enclosure.Samples of non-rigid materialsbeingtested forreflectancein the open
32、sunshine shall besupported on the enclosuredescribed in4.3. Opaquesamplesmaybesupported onanalternativeplate or frameworkcapableofmaintainingsam-ple flatness. The enclosure or alternativesupport shall becapable ofpositioning the sensing element in theapprox-imatecenteroftheplaneareaofthe sampleand f
33、rom2to6 in. (50to 300mm) away fromit, and shall be capable ofpointing the normal ofthe specimen toward the sun.4.5.2 TrackingAtrackingmechanismshall beprovidedasdescribedin 4.3.2.4.5.3 Sensor4.5.3.1 Theprimarysensing element for the measure-mentofradiant reflectanceshallbeapyranometermeetingthespeci
34、fications of4.3.3 withtheadditionalprovisionthatthephysicaldimensions ofthis pyranometershall be small*Photometers containing so-called cosine-response diffusing attachmentsand available from Photo Research (Division ofKollmorgan Corp)Burbank, CA; International Light, Inc., Newburyport, MA; Optronic
35、Laboratories, Orlando, FL;Textronix;Beaverton, OR;andGammaScien-tific, Inc., San Diego, CA;orequivalenthavebeenfoundsatisfactory forthispurpose. Otherphotometers may be pared with the size ofthe sample and the distance ofthe sensor from it.4.5.3.2 The secondary sensing element shall be asilicon phot
36、ovoltaicdetector arranged formeasurementofthe millivolt drop across a low resistance resistor in serieswiththe detectororbyadirect measurement oftheshort-circuit. current with a low impedance ammeter. Since thespectral responseofthistype detector is nonuniform overthespectral range ofsolarradiation,
37、 results obtained withits use will be most accurate for materials whose spectralreflectance does not vary appreciablyoverthe solarspec-trum. Accuracy will decrease as the spectral reflectancebecomes more nonuniform.4.3.3.3 Spectral response. Ifthe secondarysensoristobe used formeasurementsofsamples
38、havingstronglyvary-ing spectral reflectance overtherange from380to 1100nm,itshall becquippedwitha “radiometric“ or “flat-responsecorrecting filterwhich renders thespectralresponse ofthedetector/filtercombinationuniform to within l0% overthespectralrangefrom400to 900run. Ifthesensoristobeused for mea
39、surements ofphotometricreflectance, itshallmeet the specifications given in 4.4.1.4.5.3.4 Angular Response. Theresponse ofthe sensorto uniform, collimated incident radiation atan angle B ofincidence in degrees, divided byits response at normalin-cidence(0 = zerodeg), shall departfrom thecosineofB by
40、no more than 8/18* percent.5. TEST SPECIMENS5.1 Specimens forwall mounting spheres (Procedure A)5.1.1 Thesize oftest specimens required depends onthedimensions of the integrating sphere. For wall mountedspheres, the specimen must be large enough to cover theaperture of the sphere. There is no limit
41、on maximumdimension. For patterned samples, either the specimenshallbelargeenough to make a numberofmeasurementsoverdifferent areas, or severalspecimens representing thedifferent areas of the material shall be used.5.1.2 Opaquespecimens shall have at leastonesurfacethatis essentially planeoveran are
42、alarge enough tocoverthe aperture ofthe sphere.5.1.3 Transparent and slightly translucent specimensshall have two surfaces that are essentially plane andparallel. Inorder to reducelight scatteredout theedges oftranslucent specimen, the minimumdistance between theedgeofthe beam and the edge of the ap
43、erture shallbe 10times the thickness of the specimen.5.1.4 Thetransmittanceofhighly scatteringtranslucentsamples is not easilymeasured with an integrating sphereinstrument, because a significant portion ofthe incidentflux will be scattered outside the aperture. For suchmaterials, procedure Cofthis m
44、ethod is preferred.Note. Ifsuch a samplemust be measured, theedge lossescan be greatly reduced by using a circular sample ofdiameter slightlylessthanthat oftheaperture, andcoatingthe edge with silver, using the wet mirror process. Alter-natively small stops can be cemented to the edges of theASHRAE
45、STANDARD74-1988sample, so that it can be suspended in the aperture withabout halfdfits thicknessextendingoutside theaperture.5.2 Specimensfor Edwards Sphere (Procedure A).Theareaofthespecimenshallbelimited to0.01 ofthesur-face areaofthe sphere.5.3 Specimens forProcedures Cand DThe test specimens sha
46、ll be not less than 26 x 26 in.(0.66 x 0.66m). Caremust betakento preventlightleaksattheedges,especially ifthecross-sectionalshapeisnotflator ifthespecimen is patterned. Aspecimenlargeenoughtoallowtranslationacross thepyranometerorphotometerby at least one period of the shape or patternis required.3
47、.4 Specimensfor Procedure E.Test specimens for procedure shall be as described in 3.3,withtheadditionalrequirementthatthesmallestdimensionin theplaneofthesampleshall exceedeighttimesthespac-ing ofthe sensor from the sample (see 6.5.4)6. TESTING PROCEDURE6.1 Procedure A. Spectralradianttransmittance
48、orreflec-tanceusing an integrating sphere spectroradiometer.6.1.1 Calibration. Calibrate linearity and wavelengthscales ofthe spectrophotometers as recommended by themanufacturer orin accordance withASTM E275.9 Checkon calibration annually.6.1.2 Measurement.Correctionfor 100% andzero lineerrors.6.1.
49、2.1 Record 100% andzerolinecurvesat leasttwicea day during testing.Note.- Variationsin signal from thetwo beamsare normal,usually wavelength dependent, and give rise to nonideal100% lines. Similarly beam cross talk, light scattering orleaks, and detector noise giverise to a nonideal zero line.These effects produce errors inthe measured ratio of theflux reflected by thespecimenand the workingstandard.6.1.2.2 Forsphereswith separate sampleand referenceports, record t
