BS EN ISO 877-3:2018 pdf free

BS EN ISO 877-3:2018 pdf free.Plastics – Methods of exposure to solar radiation
Fresnel-reflecting solar concentrating devices operate most effectively at locations that receive at least 3 500 h of sunshine per year and where the average daytime relative humidity is less than 30 %.ASTM G90 provides requirements for the exposure site’s average ratio of direct solar radiation to global normal solar radiation.
NOTE In regions that receive 3500 h of solar radiation and where the average daytime relative humidity is less than 30 %, the average ratio of direct solar radiation to global normal solar radiation is at least 0,75. Areas that meet these criteria have a minimum diffuse component of solar radiation (sky radiation). The use of reflecting solar concentrator devices in regions of moderate to high diffuse solar irradiance will substantially reduce the amount of UV radiation at the specimen target board. Moderate to high levels of humidity and urban aerosols result in scattering of the direct component of solar radiation so that ultraviolet radiation is scattered into the hemispherical sky dome and is not available to be focused by the mirrors on to the specimen target board. This is shown in Figure 3. In addition, the use of reflecting solar concentrator devices in regions of moderate to high diffuse solar irradiance can give different stability rankings for materials compared to exposures conducted in accordance with ISO 877-2 because of the differences in UV radiation.
Solar concentrating devices are equipped with a blower to cool the specimens. Specimen temperatures for most materials are typically 10 °C higher than the maximum temperature which would be reached if an identical specimen was exposed directly to solar radiation (without concentration) at normal incidence at the same time.
If more precise control of specimen temperature is required, the temperature of a black or white panel,the temperature of a black or white standard thermometer, the temperature of a particular specimen,the air temperature or the temperature indicated by a remote sensor may be monitored and used as an input to control the specimen temperature. If used, report the controlled temperature and any observed deviations in the test report.BS EN ISO 877-3 pdf free download.