  The thermal management of an outdoor electronic enclosure can be quite
challenging due to the additional thermal load from the sun and the requirement
of having an air-sealed enclosure. It is essential to consider the effect of
solar heating loads in the design process; otherwise, it can shorten the life
expectancy of the electronic product or lead to catastrophic failure. In this
paper we analyze and compare the effectiveness of different cooling techniques
used for outdoor electronics. Various cooling techniques were compared like
special coatings and paints on the outer surface, radiation shields,
double-walled vented enclosures, fans for internal air circulation and
air-to-air heat exchangers. A highly simplified, typical outdoor system was
selected for this study measuring approximately 300x300x400 mm (WxLxH). Solar
radiation was incident on 3 sides of the enclosure. There were 8 equally spaced
PCBs inside the enclosure dissipating 12.5W each uniformly (100 watts total). A
computational fluid dynamics (CFD) model of the system was built and analyzed.
This was followed by building a mock-up of the system and conducting
experiments to validate the CFD model. It was found that some of the simplest
cooling techniques like white oil paint on the outer surface can significantly
reduce the impact of solar loads. Adding internal circulation fans can also be
very effective. Using air-to-air heat exchangers was found to be the most
effective solution although it is more complex and costly.
