Designing
an enclosure for electronic equipment looks simple - after all, "it's just a
box." In reality, though, enclosures present a long list of challenges.
Among
other things, components have to be protected from temperature and moisture and
physical damage. Users must be safe, too. Not only safe, but satisfied. So that
means noise and vibration are also issues.
Of
course, many designers will adopt an off the shelf enclosure and then add minor
modifications as needed. This approach usually makes sense from a cost
perspective and can produce satisfactory results if you carefully consider all
the tradeoffs involved.
One
of those tradeoffs is cooling. In most
cases, there are considerable cost pressures favoring a smaller and denser
packaging within an enclosure. Small saves weight, saves shelf space, pleases
users, and can even save cost. However,
in the process of getting small, cooling can become more difficult. Components can get blocked from the flow of
cooling air and it can sometimes be difficult to find space and an appropriate
location for a cooling fan.
However,
effective cooling is a necessity.
Components such as power suppliers and processor chips generate
significant amounts of heat and are often sensitive to high temperatures.
Increases
in temperature - even as little as 10 degrees -- can sharply reduce the life of
semiconductor based components. Furthermore, the ability to hold component
makers to their warranty may depend on maintaining reasonable operating
temperatures. Woe to the company that has field failures due to something as
simple as failing to provide enough cooling capacity!
Some
of the factors that influence the success of enclosure cooling include:
- The
ability of heat to dissipate within the enclosure
- Ability of air to flow freely to and from the
outside.
- Contamination from dust and other substances
- Consistent air flow to all components.
One
simple technique is to simply improve "housekeeping." Cable electrical requirements come first, of
course, but often cables can be routed to reduce their negative impact on air
flow.
In
fact, anything that can aid natural convection should be considered since this
is "free" and can dissipate a significant portion of the heat in an enclosure.
When
it comes to fans there are many options in terms of size and location within
the enclosure. Because of the wide variation in enclosure configuration, no
standard best practices have emerged.
However, the specific capabilities of the fan should be carefully
weighed against the needs of the environment because the selection of the right
fan can make or break the overall thermal performance of the enclosure.
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