Solar reflectance

It has been known for some time that the color of fabrics and the types of dyes used can be important factors in determining the solar reflectance of fabrics (15., l6). However, color of fabrics in apparel has no effect on the loss of body heat since the color of a fabric has a small effect on its surface emittance (16). Other factors such as fiber orientation and length, yarn twist, and fabric structure also influence the infrared and visible reflection properties of various fabrics (17). In a recent study, the various radiant properties of textiles measured at the peak emission wavelength of sunlight (0.6 urn), were found to approach constant values of absorptivity (0.67), absorptance (0.33), transmissivity (0.0), and reflectivity (0.33) at infinite superficial density (3.) ... 

PREDICTING MAXIMUM FIELD SERVICE TEMPERATURES FROM SOLAR REFLECTANCE. MEASUREMENTS OF VINYL... 

Vinyl products continue penetrating Western US markets. Vinyl products may show unacceptable heat distortion when installed in Western environments even after demonstrating a long tradition of acceptable heat build performance in Eastern US environments. Amethodology for predicting maximum field service temperatures from solar reflectance measurements is presented. Solar reflectance data (ASTM E-903 and E-892), field measurement data and a predictive model for a variety of vinyl systems are shown. This methodology may be used in addition to ASTM D-4803 and is not limited to vinyl materials. 2 refs. 

Hardcastle III, H., Predicting Maximum Field Service Temperatures from Solar Reflectance Measurements of... 

J. Vitko Jr., J. E. Shelby, Abstr. Solar Reflective Materials Workshop, 1980 (Sand 79-8754). 

Silver, because of its high solar specular reflectance is the best candidate for mirror surfaces in the space station solar dynamic power system(8). Silver is also the most reactive material known toward atomic oxygen. Uncoated silver rapidly degrades on exposure (Fig. 6). P2 coated silver mirrors in contrast, show only a slight loss of solar specular reflectance on exposure of up to one week. The fractional loss of the solar reflectance extrapolated to 1000 hours of ashing time (about forty years in LEO) was only 0.025. 

The coatings provided excellent protection to various substrates. P2 protected silver mirror was estimated to lose only 2.5 % of its initial solar reflectance when extrapolated to 1000 hours ashing time. For the poly(carborane siloxane) P2 coating, the mass loss rate of Kapton was reduced to half that of the best commercial coating. 

Once the sun s irradiance and material s optical properties are integrated at each wavelength, the total of reflected solar energy may be summed resulting in a single number denoted as total percent solar reflectance for the air mass used. Percent solar absorptance is then calculated ... 

It is the value of percent solar reflectance and the calculated percent solar absorptance that is powerful in predicting a materials propensity for heat build. 

For opaque materials such as a rigid vinyl, colors with high solar reflectance will remain cooler than colors with low solar reflectance under the same environmental conditions. 

Consider the risks involved with selling products which measure below the critical solar reflectance characterized in the previous step. The critical solar absorptance value of 40% became a clear design criteria for current and new color product offerings in this system. 

The complex three-layer membrane of Bangkok Airport s membrane roof is illustrated in Fig. 12.9. Here and as explained before, the high and lasting solar reflection of 70% of the outer waterproof PTFE/glass layer is also an important feature. To improve the acoustic properties of the roof, an additional middle layer has been included which consists of a cable net covered with transparent polycarbonate (PC) sheets. This, in conjunction with the translucent inner membrane liner, acts as a baffle. Figure 12.10 provides an interior view of the concourses with the innovative membrane envelope. 

Ti02 particles in HDPE matrix aid the polymer chains in crystalhzing into more perfect and thermally stable lamella. The number of nucleation sites is dramatically increased and the crystal size decreased. The solar reflectance was related to the degree of crystallinity, the spherulite size of HDPE, refractive index, and distribution of Ti02 particles in HDPE matrix. The ratile Ti02 increased the total solar reflectance from 28.2 to 51.1%. ... 

Solar reflectance is a property improved by actions in nsually oposite direction becanse additives are designed to deny tight the right of passage throngh the material. Nncleating agent can improve solar reflectance of materials. For example, tnalonic acid added to PP matrix increased NIR reflectance from 12.8 to 16.9%, whereas sorbitol increased NIR reflectance to 17.6% and solar reflectance to 15.2%. The carboxylate... 

The ciystalline polymer has higher refractive index than the amorphous polymer of the same composition. The refractive index is a dominat factor determining solar reflectivity. In a certain temperature range the refractive index changes due to a phase transition change. For example, during solid-liquid phase transition the refiactive index of paraffins changes by 0.07 to 0.10. ... 

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