Contact: Kambiz Vafai, (614) 292-6560
Written by Pam Frost (614) 292-9475 [email protected]
NEW DESIGN WILL HELP COOL MICROELECTRONICS MORE EFFICIENTLY
COLUMBUS, Ohio -- As microelectronics pack more high-powered
computer chips into ever-shrinking spaces, cooling these
devices becomes more difficult. Ohio State University
researchers have developed a heat sink, or cooling system,
that is more efficient than current designs.
In simulations, a microelectronic circuit using the new heat
sink design heated up only about one third as much as a
circuit using a conventional heat sink. Makers of
computers, lasers, and other devices may benefit from the
new design.
Kambiz Vafai, professor of mechanical engineering, and
graduate student Lu Zhu improved upon a conventional heat
sink design. Called a micro-channel heat sink, this early
design circulated coolants such as water through a network
of tiny tubes to absorb heat from electronics, much like the
coolant system in an automobile cools an engine. Vafai and
Zhu's two-layered micro-channel design doubles the number of
tubes, which measure only one-sixteenth of an inch in diameter.
"Micro-channels are useful for electronics because they
provide a great deal of cooling, and multiplying the number
of channels allows coolant to penetrate much more
effectively into the system," said Vafai.
The new design solves some problems of the old one. For
instance, to make such small tubes remove a large amount of
heat, manufacturers were forced to pump coolant through them
at high pressure, which required a large power supply and
bulky packaging.
Vafai and Zhu found that if they layered an identical second
bed of cooling channels on top of the first, they could
dissipate more heat and eliminate the need for a bulky power
supply. In the two-layer heat sink design, coolant flows
through micro-channels directly next to a heat source, into
a heat exchanger, then through the second layer of micro-
channels.
The Ohio State researchers modeled the cooling properties of
the two-layer heat sink on computer, and compared the
results to that of a conventional single-layer heat sink.
They began both models with a hypothetical microelectronic
circuit starting at an ambient temperature of approximately
77 F. The conventional, one-layer heat sink allowed the
circuit's temperature to increase 27 F, while the new, two-
layer heat sink allowed an increase of only 9 F -- about one
third as much.
"By designing this two-layer structure, we haven't
significantly complicated the manufacturing process, but
we've substantially eliminated the problems associated with
the one-layer micro-channels," said Vafai.
He said the design may cost a little more to manufacture
than traditional heat sinks, but the cost would decrease if
it were mass-produced.
Vafai said the new heat sink could cool all sorts of high-
tech devices such as computers, lasers, diodes, and mirrors
in sensitive optical equipment. He added that he got the
idea for the new design from his related research in the
flow of fluids through porous media.
"One can look at a micro-channel heat sink as a pseudo-
porous structure, only more organized. In an extremely
porous medium, coolant bathes an object and pulls away a
tremendous amount of heat. So, to a certain extent, our
design takes advantage of that knowledge and increases the
number of channels to increase the heat transfer."
So if two layers of channels are better than one, then why
not stack three or four, or more?
"Our results open up the possibility of adding more layers
of channels, but that may not be necessary. With just the
two layers we've achieved most of the cooling we wanted to
achieve," said Vafai.
Vafai has filed a patent application for the design, and
several companies have inquired about commercializing the
technology. Vafai said he can't estimate when the
technology will be available to the general public until the
patent process is finished and commercialization begins.
These results appeared in a recent issue of the
International Journal of Heat and Mass Transfer. The work
was partially funded by the Department of Energy and by a
grant from Italy for international exchange with Universita
delgi studi Federico II.
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