1、Designation: E744 07 (Reapproved 2015)Standard Practice forEvaluating Solar Absorptive Materials for ThermalApplications1This standard is issued under the fixed designation E744; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the
2、year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers a testing methodology for evaluat-ing absorptive materials used in flat plate or concentr
3、atingcollectors, with concentrating ratios not to exceed five, forsolar thermal applications. This practice is not intended to beused for the evaluation of absorptive surfaces that are (1) usedin direct contact with, or suspended in, a heat-transfer liquid,(that is, trickle collectors, direct absorp
4、tion fluids, etc.); (2)used in evacuated collectors; or (3) used in collectors withoutcover plate(s).1.2 Test methods included in this practice are propertymeasurement tests and aging tests. Property measurement testsprovide for the determination of various properties of absorp-tive materials, for e
5、xample, absorptance, emittance, and ap-pearance. Aging tests provide for exposure of absorptivematerials to environments that may induce changes in theproperties of test specimens. Measuring properties before andafter an aging test provides a means of determining the effectof the exposure.1.3 The as
6、sumption is made that solar radiation, elevatedtemperature, temperature cycles, and moisture are the primaryfactors that cause degradation of absorptive materials. Agingtests are described for exposure of specimens to these factors.NOTE 1For some geographic locations, other factors, such as saltspra
7、y and dust erosion, may be important. They are not evaluated by thispractice.1.4 The values stated in SI units are to be regarded as thestandard.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this stand
8、ard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2B537 Practice for Rating of Electroplated Panels Subjectedto Atmospheric ExposureE408 Test Methods for Total Normal Emittance o
9、f SurfacesUsing Inspection-Meter TechniquesE434 Test Method for Calorimetric Determination of Hemi-spherical Emittance and the Ratio of SolarAbsorptance toHemispherical Emittance Using Solar SimulationE772 Terminology of Solar Energy ConversionE781 Practice for Evaluating Absorptive Solar ReceiverMa
10、terials When Exposed to Conditions Simulating Stag-nation in Solar Collectors With Cover PlatesE903 Test Method for Solar Absorptance, Reflectance, andTransmittance of Materials Using Integrating SpheresG26 Practice for Operating Light-Exposure Apparatus(Xenon-Arc Type) With and Without Water for Ex
11、posureof Nonmetallic Materials (Discontinued 2001) (With-drawn 2000)3G90 Practice for Performing Accelerated Outdoor Weather-ing of Nonmetallic Materials Using Concentrated NaturalSunlightG151 Practice for Exposing Nonmetallic Materials inAccel-erated Test Devices that Use Laboratory Light SourcesG1
12、55 Practice for Operating Xenon Arc Light Apparatus forExposure of Non-Metallic MaterialsNOTE 2In previous editions, G26 was referenced for xenon arcexposure. It has been replaced with Practices G151 and G155, theperformance based standards, which cover the same apparatus used inPractice G26. The la
13、tter had described very specific designs used forxenon arc exposure.3. Terminology3.1 Refer to Teminology E772 for terminology relating tosolar energy conversion.1This practice is under the jurisdiction of ASTM Committee E44 on Solar,Geothermal and OtherAlternative Energy Sources and is the direct r
14、esponsibility ofSubcommittee E44.05 on Solar Heating and Cooling Systems and Materials.Current edition approved March 1, 2015. Published April 2015. DiscontinuedFebruary 2002 and reinstated as E744-07. Last previous edition approved in 2007 asE744-07. DOI: 10.1520/E0744-07R15.2For referenced ASTM st
15、andards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.
16、Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14. Significance and Use4.1 The methods in this practice are intended to aid in theassessment of long-term performance by comparative testingof absorptive materials. The results of the me
17、thods, however,have not been shown to correlate to actual in-service perfor-mance.4.2 The testing methodology in this practice provides twotesting methods, in accordance with Fig. 1.4.2.1 MethodA, which aims at decreasing the time requiredfor evaluation, uses a series of individual tests to simulate
18、various exposure conditions.4.2.2 Method B utilizes a single test of actual outdoorexposure under conditions simulating thermal stagnation.4.2.3 Equivalency of the two methods has not yet beenestablished.5. Test Specimens5.1 Test specimens shall consist of the complete absorbermaterial including coa
19、tings or layers and specific substrateswhere applicable.5.2 The specimens shall be prepared in accordance withprocedures and conditions used (or expected to be used) incommercial practice or in accordance with the recommenda-tions of the coatings or material supplier.NOTE 3Results may vary due to co
20、ating substrate interactions.NOTE 4Some absorbers may not have discreet coatings or layers, forexample, pigmented materials.6. Conditioning6.1 Specimens shall be measured and tested as receivedwithout additional processing or preconditioning.7. Test Methods7.1 Property Measurement TestsPerform all p
21、ropertymeasurement tests at room temperature unless otherwise speci-fied.7.1.1 Solar AbsorptanceTest in accordance with TestMethod E903, unless otherwise specified.NOTE 5The spectral reflectance curves from which solar absorptanceis calculated are often a more sensitive indicator of the onset of abs
22、orbermaterials degradation than integrated solar absorptance values. This isespecially true for changes occurring in spectral regions where there is alimited amount of energy in the solar spectrum, for example, in the nearinfrared region.7.1.2 EmittanceTest in accordance with Test MethodsE434 or E40
23、8, unless otherwise specified.7.1.3 AppearanceTest in accordance with Practice B537,unless otherwise specified.7.2 Environmental Exposure.7.2.1 Outdoor Exposure Under Simulated StagnationConditionsExpose test specimens for a minimum period of12 months (Note 6) using Practice E781.NOTE 6It may be des
24、irable to continue exposures of test specimensbeyond the time period recommended to obtain additional rate data or toobtain data on mechanisms of degradation.7.2.2 Outdoor Exposure Using Fresnel ConcentrationExpose test specimens to direct sunlight reflected from theFresnel concentrators described i
25、n Practice G90. Test speci-mens shall be mounted in a manner similar to that shown inFig. 2. The cooling of the test specimens shall be adjusted tomaintain the absorber specimens at stagnation temperatures.Refer to Cycle 3 of Practice G90 for details of the water sprayoperating procedure.NOTE 7The s
26、pectral transmission characteristics of the cover(s) usedFIG. 1 Outline of Test Method OptionsE744 07 (2015)2in a solar collector will control the amount and spectral distribution of thesolar radiation reaching the absorber surface. For this reason, testingshould be performed with the glazings to be
27、 used in the actual collectorinstalled between the light source and the absorber surface, or with theworst-case configuration possible. When solar simulators are used, thelight source should be filtered to match the solar spectrum.7.2.3 Xenon Arc ExposureExpose test specimens to radia-tion from a fi
28、ltered xenon arc lamp in accordance with theconditions stipulated in Table 1.7.2.4 Effect of Elevated TemperaturesExpose test speci-mens to heat aging for a period of 500 h at the stagnationtemperature to which they will be exposed in actual service.NOTE 8The maximum service temperature will normall
29、y be obtainedwhen the collector is receiving its maximum level of solar radiation andthe heat transfer fluid is not flowing through the collector. Data onstagnation temperatures are normally available from collector manufac-turers. Stagnation temperature data for flat plate collectors are included i
30、nthe National Bureau of Standards (NBS) Technical Note 1187.47.2.5 Effect of MoistureExpose test specimens for 30 daysat 90 6 5Cand95+5%relative humidity.NOTE 9Research has indicated that the degradation caused by this testcan be considerably more severe than the degradation occurring in 3 yearsof o
31、utdoor exposure in full-size solar collectors for some absorbermaterials.7.2.6 Effect of Thermal CyclingExpose test specimens to30 cycles of heating and cooling with each cycle consisting ofthe following steps:7.2.6.1 Heat for7hatthestagnation temperature to whichthey will be exposed in actual servi
32、ce (see Note 5).7.2.6.2 Cool to room temperature over a 30-min period.7.2.6.3 Cool at 10C for 16 h.7.2.6.4 Warm to room termperature over a 30-min period.NOTE 10The humidity maintained during this warming process shallbe such that moisture condenses on the surfaces of the test specimens.7.2.7 Offgas
33、singRelease of volatiles from the absorbermaterial, in some cases, may be a significant factor that canaffect the transmittance of a cover plate, or the properties of theabsorber itself, or both.Agenerally applicable procedure is notpresently available to evaluate effects of offgassing products. Iti
34、s essential, however, that this factor be recognized.8. Test Procedure8.1 Select either Method A (see 8.2) or Method B (see 8.3),in accordance with Fig. 1.8.2 Method A (Laboratory Exposure):8.2.1 Select five sets of test specimens for each absorbermaterial to be evaluated. Each set shall consist of
35、at least threeidentical test specimens.4NBS Technical Note 1187, “Performance Criteria for Solar Heating andCooling Systems in Commercial Buildings,” available from Superintendent ofDocuments, U.S. Government Printing Office, Washington, DC 20402.NOTE 1Film Cover: Polytetrafluoroethylene.NOTE 2Absor
36、ber Test Specimen: 7.5 6.1 cm.NOTE 3Aluminum Pan: 11.5 6.5 2 cm. Interior painted black and baked at 230C for 24 h.FIG. 2 Accelerated Exposure Absorber Mini-BoxTABLE 1 Exposure Test ConditionsNOTE 11330 12 h = 5556 day,0.52 W/(m2 nm) at 340 nm for 1330 h = 2490 kJ/(m2 nm) at 340nm,0.49 W/(m2 nm) at
37、340 nm for 1330 h = 2298 kJ/(m2 nm) at 340nm,0.50 W/(m2 nm) at 340 nm for 1330 h = 2394 kJ/(m2 nm) at 340nm.Total UV irradiance from xenon controlled at 0.5 W/(m2 nm) at 340 nmis 55.5 W/m2. Hourly TUV exposure is 198 kJ/m21330 h 198 kJ/m2h = 263 MJ/m2.Radiation source Xenon ArcASTM Practice G151 and
38、 G155Filters DaylightIrradiance at 340 nm, W/(m2 nm) 0.50 0.02AUninsulated black panel temperature 90 2.5CAChamber air temperature 62 2CARelative humidity, % 50 5/saturationA,BRadiant Exposure at 340 nm, kJ/(m2 nm) 2394 30CExposure interval, h 1330 12Exposure program, min 40 light, 20 light and wate
39、r spray onfront of specimen, 40 light, 60 darkwith water spray on back ofspecimenAThe operational fluctuations are allowable deviations from the specified set pointsfor irradiance, temperature and relative humidity during equilibrium operation.They do not imply that the user is allowed to program a
40、set point higher or lowerthan that specified. If the operational fluctuations are greater than the maximumallowable after the equipment has stabilized, discontinue the test and correct thecause of the problem before continuing.BLight on condition without water spray/light off (dark) conditions with
41、back panelrack spray.CProvides total UV (300-400 nm) radiant exposure equal to approximately 50 % ofthe average yearly amount available at Miami, FL. Previous versions of thestandard stated that 1330 h exposure in the xenon arc device is equivalent to ayear in Miami, FL. It was based on an incorrect
42、 assumption of exposure toradiation 100 % of the time due to neglect of the dark time and it also neglectedadjustment for differences in the spectral regions measured in the xenon arcdevice and Miami. Test results cannot be extrapolated to simulate a full yearexposure in Miami because of non lineari
43、ty of degradation with exposure for manymaterials.E744 07 (2015)38.2.2 Determine the absorptance and emittance of the speci-mens in accordance with 7.1.1 and 7.1.2. Also document theappearance of the specimens in accordance with 7.1.3.8.2.3 Store Set 5 specimens (controls) at ambient laboratorycondi
44、tions.8.2.4 Expose Set 1 specimens in accordance with 7.2.4.8.2.5 Expose Set 2 specimens in accordance with 7.2.6.8.2.6 Expose Set 3 specimens in accordance with 7.2.5.8.2.7 Expose Set 4 specimens in accordance with one of theexposures described in 7.2.2 and 7.2.3.8.2.8 Determine absorptance and emi
45、ttance and documentappearance as described in 8.2.2.8.3 Method B (Outdoor Exposure):8.3.1 Select two sets of test specimens for each absorbermaterial to be evaluated. Each set shall consist of at least threeidentical test specimens.8.3.2 Determine the absorptance and emittance of the speci-mens in a
46、ccordance with 7.1.1 and 7.1.2. Also document theappearance of the specimens in accordance with 7.1.3.8.3.3 Store the Set 2 specimens (controls) at ambient labo-ratory conditions.8.3.4 Expose Set 1 specimens in accordance with 7.2.1.8.3.5 Determine absorptance and emittance and documentappearance as
47、 described in 8.3.2.9. Report9.1 The report shall include the following:9.1.1 Complete identification of the absorber materialtested.9.1.2 Identification of which Method, A or B, was used. IfMethod B was used, the report shall include data required byPractice E781.9.1.3 Complete identification of th
48、e substrate(s) used forabsorber coatings, including composition and thickness.9.1.4 Complete identification of and spectral transmissioncharacteristics of cover plate material used in 7.2.1 or 7.2.2.9.1.5 Method of preparing test specimens.9.1.6 Length of time of exposure in 7.2.2 or 7.2.3.9.1.7 Ide
49、ntification of filters used in 7.2.3.9.1.8 Temperatures used in the exposures described in 7.2.2,7.2.3, 7.2.4, 7.2.5, and 7.2.6.Also heating and cooling rates andnumber of cycles used in 7.2.6.9.1.9 Moisture conditions used in the exposure described in7.2.5.9.1.10 Number of specimens tested.9.1.11 Test results (absorptance, emittance, and appearance)before and after aging (mean and range) for exposed specimensand for controls.9.1.12 Documentation of instrument and procedures usedfor determining absorptance, emittance,
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