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Significance and Use
The methods in this practice are intended to aid in the assessment of long-term performance by comparative testing of absorptive materials. The results of the methods, however, have not been shown to correlate to actual in-service performance.
The testing methodology in this practice provides two testing methods, in accordance with Fig. 1.
4.2.1 Method A, which aims at decreasing the time required for evaluation, uses a series of individual tests to simulate various exposure conditions.
4.2.2 Method B utilizes a single test of actual outdoor exposure under conditions simulating thermal stagnation.
4.2.3 Equivalency of the two methods has not yet been established.
FIG. 1 Outline of Test Method Options
1.1 This practice covers a testing methodology for evaluating absorptive materials used in flat plate or concentrating collectors, with concentrating ratios not to exceed five, for solar thermal applications. This practice is not intended to be used for the evaluation of absorptive surfaces that are (1) used in direct contact with, or suspended in, a heat-transfer liquid, (that is, trickle collectors, direct absorption fluids, etc.); (2) used in evacuated collectors; or (3) used in collectors without cover plate(s).
1.2 Test methods included in this practice are property measurement tests and aging tests. Property measurement tests provide for the determination of various properties of absorptive materials, for example, absorptance, emittance, and appearance. Aging tests provide for exposure of absorptive materials to environments that may induce changes in the properties of test specimens. Measuring properties before and after an aging test provides a means of determining the effect of the exposure.
1.3 The assumption is made that solar radiation, elevated temperature, temperature cycles, and moisture are the primary factors that cause degradation of absorptive materials. Aging tests are described for exposure of specimens to these factors. Note 1 - For some geographic locations, other factors, such as salt spray and dust erosion, may be important. They are not evaluated by this practice.
1.4 The values stated in SI units are to be regarded as the standard.
This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
B537 Practice for Rating of Electroplated Panels Subjected to Atmospheric Exposure
E408 Test Methods for Total Normal Emittance of Surfaces Using Inspection-Meter Techniques
E434 Test Method for Calorimetric Determination of Hemispherical Emittance and the Ratio of Solar Absorptance to Hemispherical Emittance Using Solar Simulation
E772 Terminology of Solar Energy Conversion
E781 Practice for Evaluating Absorptive Solar Receiver Materials When Exposed to Conditions Simulating Stagnation in Solar Collectors With Cover Plates
E903 Test Method for Solar Absorptance, Reflectance, and Transmittance of Materials Using Integrating Spheres
G26 Practice for Operating Light-Exposure Apparatus (Xenon-Arc Type) With and Without Water for Exposure of Nonmetallic Materials (Discontinued 2001)
G90 Practice for Performing Accelerated Outdoor Weathering of Nonmetallic Materials Using Concentrated Natural Sunlight
G151 Practice for Exposing Nonmetallic Materials in Accelerated Test Devices that Use Laboratory Light Sources
G155 Practice for Operating Xenon Arc Light Apparatus for Exposure of Non-Metallic Materials
ICS Number Code 27.160 (Solar energy engineering)
UNSPSC Code 60104701(Solar collecting devices)
ASTM E744-07, Standard Practice for Evaluating Solar Absorptive Materials for Thermal Applications, ASTM International, West Conshohocken, PA, 2007, www.astm.orgBack to Top