OL2.NOV–Aavid–SC
Fluid cooling system takes heat out of hot chips
One thing is well known about next-generation microprocessors: chips like
Intel's Pentium and Digital Equipment Corp.'s Alpha (see page 00) generate
much more heat than older microprocessors like the 386 and 486. Although a
conventional heat sink and/or fan could be used in a design, it would have
to be quite large to adequately cool such a hot-running chip–not a
desirable design practice in an age of shrinking products. Now Aavid
Engineering, a supplier of thermal products and custom cooling solutions,
believes it has an alternative–a clever, compact fluid cooling system
that resides inside the computer. Called Oasis, the cooling system was
demonstrated in a desktop PC at the recent Wescon show in San Francisco.
Oasis will allow manufacturers to retrofit existing notebook, desktop, and
tower PCs with Pentium and other advanced chips without worrying about the
heat the parts generate. At the same time, Oasis eliminates the need for
the larger, more expensive heat sinks and fans otherwise required to cool
the hot-running chips. The most notable element of Oasis is a
condenser–actually a flexible heat sink filled with Fluorinert–that
mounts either behind the display screen or in one of the PC's expansion
slots. The condenser is similar to the liquid heat sink introduced by 3M
several years ago (see Electronic Products, Jan. 1989, p. 30), but is
Aavid's own patented design. Although the size of the condenser can vary
with the cooling requirements, the one used in the demonstration PC measured
8 (L) x 10 (W) x 5/8 (H) in. Completing the closed-loop cooling system is
a pair of flexible tubes that run from the condenser to a heat-sink-like
device Aavid calls an evaporator. The evaporator, which sits atop the
microprocessor, resembles a copper or aluminum heat sink but has specially
treated surfaces designed to maximize heat transfer efficiency. In
operation, heat from the chip dissipates into the evaporator and is
absorbed by liquid coming from the condenser in one tube. The evaporator
then vaporizes the boiling liquid, which flows through the second tube
back into the condenser (see diagram). The chip in the demonstration PC
was not a Pentium, but dissipated the same power and operated at 60
degreesC. The condenser, which produced a 20 degreesC ambient air
temperature, achieved a thermal resistance of 0.8 degreesC/W. Aavid is
now looking for customers for its Oasis technology. For more information,
contact Gary Kuzmin, Aavid Engineering (Laconia, NH) at 603-528-3400, or .
–Spencer Chin
CAPTION:
In Aavid's Oasis liquid cooler, heat dissipated from the chip is absorbed
in the evaporator by Fluorinert coming from the condenser. The resultant
boiling vapor flows back into the condenser, completing the cooling system
loop.
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