The Impact of Anodization on the Thermal Performance of Passively Cooled Electronic Enclosures Made of Die-cast Aluminum

Natural convection and thermal radiation from anodized die-cast aluminum enclosures designed for the application of high power density battery chargers are investigated experimentally. Several sample enclosures are prepared using the two most commonly available types of anodization: i) Type II-black; and ii) Type III-clear. The enclosures are then tested in a customized natural convection - thermal radiation test chamber. Total emittance of bare and anodized surface is measured using Fourier Transform Infrared Reflectometer (FTIR) spectroscopy. The results show that the total hemispherical emissivity of die-cast aluminum sample surface can be significantly improved from 0.14 to 0.92 after anodizing. More importantly, anodization can lead to a considerable reduction in thermal resistance (up to 14.7%) compared to the identical untreated enclosures. Because of the unique surface morphology of anodized die-cast aluminum, it is also observed that the same improvement of thermal emissivity as well as overall thermal performance can be achieved by either types of anodization.