New Water Cooling

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A new water-cooling system for computer chips has been developed that incorporates a clever pump with no moving parts. The system, developed by Californian start-up company Cooligy, aims to silently solve the problem that the faster chips get, the hotter they become.

In the near future, the chips in high-speed laptops and desktop PCs will generate so much heat that traditional air cooling systems will struggle to cope. Simply increasing the speed of the fans used will increase the noise they make and the risk of mechanical failure. So a number of companies are now working on systems that use water to draw heat away.

The computer industry's rule of thumb, Moore's Law, predicts that the speed of the central processing unit in a computer doubles every 18 months. "And as we go from one generation of CPUs to another, the heat dissipated by these chips doubles as well," says Cooligy's Andy Keane.

Some water-based cooling systems already exist. Hitachi announced a water-cooled Pentium IV laptop in February 2002, while in May 2003 NEC released what it claimed was the world's first mass-produced water-cooled desktop PC. Some laptops also use pipes containing methanol or other liquids to transfer heat away from the CPU by convection.

Electro-osmosis

What makes Cooligy's approach different is that it uses a pump relying on electro-osmosis to move the water, meaning it has no moving parts and is silent. The pump was developed by mechanical engineer Ken Goodson at Stanford University.

It consists of a disc of glass two millimetres thick and five centimetres in diameter. This is riddled with little tubes, about one micron in diameter, which pass from one flat side of the disc to the other.

Applying an electric charge across the disc interacts with charged layers on the surface of the pores and causes ions to migrate. These drag water molecules along in the process, creating a flow.

Goodson's experiments have produced a flow rate of 200 millilitres per minute. Keane says this would be enough to cool chips that radiate 120 watts of heat per square centimetre, with hotspots of up to 500 watts. In comparison, Intel's Centrino chip dissipates 35 watts.

However, others are cautious about the idea. "I don't like mixing water and electricity," says Paul Lee, at QuietPC in North Yorkshire, England, a company that specialises in PC noise elimination. "Even if all the technical details are ironed out, I think it will be five years at least before fans are replaced. They are still the cheapest option."

source: New scientist