阳极氧化在辐射散热中的作用(alumina anodized impact)

英文论文。学习一下。

alumina anodized impact.pdf (410.88 KB)

Spectral Emissivity of Anodized Aluminum and the Thermal Transmittance of Aluminum Window Frames
Arild Gustavsen, Associate Professor, Paul Berdahl, Physicist,


KEYWORDS: Spectral emissivity, Anodized aluminum, Masking tape, Fenestration, Window frames, Thermal
transmittance.

SUMMARY:
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 40 μm.

1. Introduction
Heat transfer in building sections is a combined process involving conduction, convection and radiation.
Conduction takes place in solid materials while convection and radiation take place both at the exterior surfaces and in the internal cavities of building sections. Radiation heat transfer depends on the emissivity of building sections, the temperature differences between the surfaces within building sections, and on the temperature differences between the exterior faces of building sections and the exterior environment. Since the temperature difference usually can not be controlled to reduce heat transfer through building sections the emissivity is the parameter that needs to be reduced to minimize radiation heat transfer effects.