Spectral Emissivity of Anodized Aluminum and the Thermal Transmittance of Aluminum Window Frames
This paper studies the normal spectral emissivity of an anodized aluminum window frame profile, an untreated aluminum profile, and some masking tapes. The normal spectral emissivity is measured in the wavelength interval from 4.5 to 40 μm (wavenumbers 2222 cm-1 to 250 cm-1). Total emissivity values are also reported. Specimens are cut both from the edge and from the middle of the six-meter long anodized aluminum profile. Specimens facing the internal cavities (thermal break cavity and all aluminum cavity) are measured. The masking tapes are of the types used in measurements of thermal transmittance (U-value) of window frames. It is shown that the normal total emissivity is fairly constant (between 0.834 and 0.856) for exterior parts of the anodized profile and for surfaces facing the thermal break cavity. The normal total emissivity of the allaluminum internal cavities is found to vary between 0.055 and 0.82. For two of the tapes measured, the normal spectral emissivity is found to be fairly independent of wavelength for wavelengths between 6.5 and 40μm.