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AIRFLOW & COOLING
Given how important thermal
design is to achieving low noise levels, it's quite impressive that there is
almost no visual evidence of thermal design: No fan grills, no wide-open (or
even restricted) intakes, and no visible heatsinks. The evidence is there if
you look for it, but even then the surface area of the intakes and exhaust vents
is shockingly small. No doubt the low-power Core Duo around which the iMac is
based helps keep heat down a bit, but even then it's surprising how little airflow
there seems to be.
Most of the bottom serves as an intake, but the intake grill is quite restrictive...
The main intake is located on the bottom, where more of the thick plastic casing
has been cut away to reveal a thin (but restrictive) metal grill. The amount
of air flowing through the system must be very small, since no airflow could
be felt at the bottom even with the system running full tilt.
There is another small opening in the center of the back panel ... but is
it an intake or a speaker?
There is another small vent on the back panel, but no airflow could be felt
here either.
The slim white strip at the top is the only point of exhaust.
The exhaust vent is a thin indented strip that runs across the top of the back
panel. To a casual observer, it appears to be part of the system's cosmetic
design. Only the slight trickle of hot air that we could feel drifting from
it betrayed its true function. Even so, the amount of air passing through the
system is probably not much more than would be achieved with convection alone.
In addition to the small amount of airflow, some cooling is also provided by
direct conduction. As a heatsink material, the plastic exterior has nothing
on copper or aluminum, but there is enough surface area that it probably helps
a little. In this respect it is like a laptop, which also dissipate heat through
plastic. The back of the screen got quite warm to the touch, confirming that
some heat was being transferred in this way.
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