1、Designation: E 905 87 (Reapproved 2007)Standard Test Method forDetermining Thermal Performance of TrackingConcentrating Solar Collectors1This standard is issued under the fixed designation E 905; the number immediately following the designation indicates the year oforiginal adoption or, in the case
2、of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of thermalperformance of tracking concentrating so
3、lar collectors that heatfluids for use in thermal systems.1.2 This test method applies to one- or two-axis trackingreflecting concentrating collectors in which the fluid enters thecollector through a single inlet and leaves the collector througha single outlet, and to those collectors where a single
4、 inlet andoutlet can be effectively provided, such as into parallel inletsand outlets of multiple collector modules.1.3 This test method is intended for those collectors whosedesign is such that the effects of diffuse irradiance on perfor-mance is negligible and whose performance can be character-iz
5、ed in terms of direct irradiance.NOTE 1For purposes of clarification, this method shall apply tocollectors with a geometric concentration ratio of seven or greater.1.4 The collector may be tested either as a thermal collec-tion subsystem where the effects of tracking errors have beenessentially remo
6、ved from the thermal performance, or as asystem with the manufacturer-supplied tracking mechanism.1.4.1 The tests appear as follows:SectionLinear Single-Axis Tracking Collectors Tested asThermal Collection Subsystems 1113System Testing of Linear Single-Axis Tracking Collectors 1416Linear Two-Axis Tr
7、acking and Point Focus CollectorsTested as Thermal Collection Subsystems 1719System Testing of Point Focus and Linear Two-AxisTracking Collectors 20221.5 This test method is not intended for and may not beapplicable to phase-change or thermosyphon collectors, to anycollector under operating conditio
8、ns where phase-change oc-curs, to fixed mirror-tracking receiver collectors, or to centralreceivers.1.6 This test method is for outdoor testing only, under clearsky, quasi-steady state conditions.1.7 Selection and preparation of the collector (samplingmethod, preconditioning, mounting, alignment, et
9、c.), calcula-tion of efficiency, and manipulation of the data generatedthrough use of this standard for rating purposes are beyond thescope of this test method, and are expected to be coveredelsewhere.1.8 This test method does not provide a means of determin-ing the durability or the reliability of
10、any collector or compo-nent.1.9 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.10 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of t
11、his standard 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:2E 772 Terminology Relating to Solar Energy Conversion2.2 Other Standard:ASHRAE 93-86, Methods of Testing to Determine
12、theThermal Performance of Solar Collectors3NOTE 2Where conflicts exist between the content of these referencesand this test method, this test method takes precedence.NOTE 3The definitions and descriptions of terms below supersedeany conflicting definitions included in Terminology E 772.3. Terminolog
13、y3.1 Definitions:3.1.1 area, absorber, ntotal uninsulated heat transfersurface area of the absorber, including unilluminated as well asilluminated portions. (E 772)3.1.2 collector, point focus, nconcentrating collector thatconcentrates the solar flux to a point. (E 772)3.1.3 collector, tracking, nso
14、lar collector that moves so asto follow the apparent motion of the sun during the day,rotating about one axis or two orthogonal axes. (E 772)1This test method is under the jurisdiction of ASTM Committee E44 on Solar,Geothermal and OtherAlternative Energy Sources and is the direct responsibility ofSu
15、bcommittee E44.05 on Solar Heating and Cooling Systems and Materials.Current edition approved March 1, 2007. Published April 2007. Originallyapproved in 1982. Last previous edition approved in 2001 as E 905 87(2001).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM
16、 Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from the American Society of Heating, Refrigerating, and AirConditioning Engineers, Inc., 1791 Tullie Circle, N.E. Atlanta, GA 30329.1
17、Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.4 concentration ratio, geometric, nratio of the collec-tor aperture area to the absorber area. (E 772)3.1.5 quasi-steady state, nsolar collector test conditionswhen the flow rate, fl
18、uid inlet temperature, collector tempera-ture, solar irradiance, and the ambient environment havestabilized to such an extent that these conditions may beconsidered essentially constant (see Section 8).3.1.6 DiscussionThe exit fluid temperature will, underthese conditions, also be essentially consta
19、nt (see ASHRAE93-86).3.2 Definitions of Terms Specific to This Standard:3.2.1 altazimuthal tracking, ncontinual automatic posi-tioning of the collector normal to the suns rays in both altitudeand azimuth.3.2.2 area, aperture (of a concentrating collector),nmaximum projected area of a solar collector
20、 modulethrough which the unconcentrated solar radiant energy isadmitted, including any area of the reflector or refractor shadedby the receiver and its supports and including gaps betweenreflector segments within a module. (E 772)3.2.3 clear-sky conditions, nrefer to a minimum level ofdirect normal
21、solar irradiance of 630 W m2(200 Btu ft2h1) and a variation in both the direct and total irradiance ofless than 64 % during the specified times before and duringeach test.3.2.4 end effects, nin linear single-axis tracking collec-tors, the loss of collected energy at the ends of the linearabsorber wh
22、en the direct solar rays incident on the collectormake a non-zero angle with respect to a plane perpendicular tothe axis of the collector.3.2.5 fluid loop, nassembly of piping, thermal control,pumping equipment and instrumentation used for conditioningthe heat transfer fluid and circulating it throu
23、gh the collectorduring the thermal performance tests.3.2.6 module, nthe smallest unit that would function as asolar energy collection device.3.2.7 near-normal incidence, nangular range from exactnormal incidence within which the deviations in thermalperformance measured at ambient temperature do not
24、 exceed62 %, such that the errors caused by testing at angles otherthan exact normal incidence cannot be distinguished fromerrors caused by other inaccuracies (that is, instrumentationerrors, etc.).3.2.8 rate of heat gain, nthe rate at which incident solarenergy is absorbed by the heat transfer flui
25、d, defined math-ematically by:Q5 mCpDta(1)3.2.9 response time, ntime required for D tato decline to10 % of its initial value after the collector is completely shadedfrom the suns rays; or the time required for Dtato increase to90 % of its value under quasi-steady state conditions after theshaded col
26、lector at equilibrium is exposed to irradiation.3.2.10 quasi-steady state, nrefers to that state of thecollector when the flow rate and inlet fluid temperature areconstant but the exit temperature changes “gradually” due tothe normal change in solar irradiance that occurs with time forclear sky cond
27、itions.3.2.10.1 DiscussionIt is defined by a set of test conditionsdescribed in 10.1.3.2.11 solar irradiance, direct, in the aperture plane,ndirect solar irradiance incident on a surface parallel to thecollector aperture plane.3.2.12 solar irradiance, total, ntotal solar radiant energyincident upon
28、a unit surface area (in this standard, the apertureof the collector) per unit time, including the direct solarirradiance, diffuse sky irradiance, and the solar radiant energyreflected from the foreground.3.2.13 thermal performance, nrate of heat flow into theabsorber fluid relative to the incident s
29、olar power on the planeof the aperture for the specified test conditions.3.3 Symbols:Aa= collector aperture area, m2(ft2).Aabs= absorber area, m2(ft2).A1= ineffective aperture area, m2(ft2).C = geometric concentration ratio Aa/Aabs, dimensionless.Cp= specific heat of the heat transfer fluid,Jkg1 C1(
30、Btu lb1F1).Es,d= diffuse solar irradiance incident on the collector aper-ture, W m2(Btu h1ft2).Es,D= direct solar irradiance in the plane of the collectoraperture, W m2(Btu h1ft2).Es,DN= direct solar irradiance in the plane normal to the sun,Wm2(Btu h1ft2).Es,2p= global solar irradiance incident on
31、a horizontal plane,Wm2(Btu h1ft2).Es,t= total solar irradiance incident on the collector aperture,Wm2(Btu h1ft2).f = focal length, m (ft).g = spacing between the effective absorbing surfaces ofadjacent modules, m (ft).K = incident angle modifier, dimensionless.L = length of reflector segment, m (ft)
32、.lr= length of receiver that is unilluminated, m (ft).m = mass flow rate of the heat transfer fluid, kg s1(lbm h1).Q= net rate of energy gain in the absorber, W (Btu h1).QL= rate of energy loss, W (Btu h1).r = overhang of the receiver past the end of the reflectors, m(ft).R (u) = ratio of the rate o
33、f heat gain to the solar powerincident on the aperture, dimensionless.s = angle which the collector aperture is tilted from thehorizontal to the equator, and is measured in a vertical N-Splane, degrees.tamb= ambient air temperature, C (F).Dta= temperature difference across the absorber, inlet tooutl
34、et, C (F).Dta,i= temperature difference across the absorber inlet tooutlet at the time of initial quasi-steady state conditions, C(F).Dta,f= temperature difference across the absorber inlet tooutlet at the time final quasi-steady state conditions arereached, C (F).Dta,T= temperature difference acros
35、s the absorber inlet tooutlet at time T, C (F).E 905 87 (2007)2tf,i= temperature of the heat transfer fluid at the inlet to thecollector, C (F).w = width of reflector segment, m (ft).b = solar altitude angle, degrees.G(u|) = end effect factor, dimensionless.d = solar declination, degrees.u = angle o
36、f incidence between the direct solar rays and thenormal to the collector aperture, degrees.u|, u= angles of incidence in planes parallel and perpen-dicular, respectively, to the longitudinal axis of the collector,degrees.ui= maximum angle of incidence at which all rays incidenton the aperture are re
37、directed onto the receiver of the samemodule, degrees.u8c= minimum angle of incidence at which radiation re-flected from one modules aperture is intercepted by thereceiver of an adjacent module, degrees.f = solar azimuth angle measured from the south, degrees.4. Summary of Test Method4.1 Thermal per
38、formance is the rate of heat gain of acollector relative to the solar power incident on the plane of thecollector aperture. This test method contains procedures tomeasure the thermal performance of a collector for certainwell-defined test conditions. The procedures determine theoptical response of t
39、he collector for various angles of incidenceof solar radiation, and the thermal performance of the collectorat various operating temperatures for the condition of maxi-mum optical response. The test method requires quasi-steadystate conditions, measurement of environmental parameters,and determinati
40、on of the fluid mass flow rate-specific heatproduct and temperature difference, Dta, of the heat transferfluid between the inlet and outlet of the collector. Thesequantities determine the rate of heat gain, mCpDta, for the solarirradiance condition encountered. The solar power incident onthe collect
41、or is determined by the collector area, its anglerelative to the sun, and the irradiance measured during the test.4.2 Two types of optical effects are significant in determin-ing the thermal performance: (1) misalignment of the focalzone with respect to the receiver due to tracking errors anderrors
42、in the redirection of the irradiance intercepted by thecollector, and (2) changes in the solar power incident on thecollector aperture due to decreased projected area (cosineresponse) and other optical losses. The first effect is accountedfor primarily in terms of the data generated for near-normali
43、ncidence thermal performance for a given collector. Thecosine response portion of the second effect is accounted for bythe determination of the solar power incident on the plane ofthe aperture. The departure of the optical response of thecollector from the cosine response is determined by obtainingt
44、he incident angle modifier data. The incident angle modifier isimportant in predicting such collector characteristics as all-daythermal performance.5. Significance and Use5.1 This test method is intended to provide test data essen-tial to the prediction of the thermal performance of a collectorin a
45、specific system application in a specific location. Inaddition to the collector test data, such prediction requiresvalidated collector and system performance simulation modelsthat are not provided by this test method. The results of this testmethod therefore do not by themselves constitute a rating
46、ofthe collector under test. Furthermore, it is not the intent of thistest method to determine collector efficiency for comparisonpurposes since efficiency should be determined for particularapplications.5.2 This test method relates collector thermal performanceto the direct solar irradiance as measu
47、red with a pyrheliometerwith an angular field of view between 5 and 6. The prepon-derance of existing solar radiation data was collected withinstruments of this type, and therefore is directly applicable toprediction of collector and system performance.5.3 This test method provides experimental proc
48、edures andcalculation procedures to determine the following clear sky,quasi-steady state values for the solar collector:5.3.1 Response time,5.3.2 Incident angle modifiers,5.3.3 Near-normal incidence angular range, and5.3.4 Rate of heat gain at near-normal incidence angles.NOTE 4Not all of these valu
49、es are determined for all collectors. Table1 outlines the tests required for each collector type and tracking arrange-ment.5.4 This test method may be used to evaluate the thermalperformance of either (1) a complete system, including thetracking subsystems and the thermal collection subsystem, or(2) the thermal collection subsystem.5.4.1 When this test method is used to evaluate the completesystem, the test shall be performed with the manufacturerstracker and associa
copyright@ 2008-2019 麦多课文库（www.mydoc123.com）网站版权所有
备案/许可证编号：苏ICP备17064731号-1