Tiny bubbles

Purdue University researchers have made a discovery that may lead to the development of an innovative liquid-cooling system for future computer chips.

In about three years, innovative cooling systems will be needed for personal computers. That’s because new microprocessors will generate four times more heat than their existing counterparts. And while today’s computers use fans and heat sinks containing fins to help cool the processors, the technology won’t be efficient enough to remove the heat generated by future chips.

Now, an innovative liquid-cooling system for future computer chips may provide a potential solution to the problem.

The system itself, developed by a team working at Purdue University, uses a closed loop of two vertical, parallel tubes containing a dielectric liquid – or a liquid that does not conduct electricity. The liquid flows through microchannels in a metal plate that’s touching the chip. As liquid flows through the channels, it’s heated by the chip and begins to boil, producing bubbles of vapour. The bubbles rise to the top of the tube, where they are cooled by a fan and condensed back into a liquid. The cool liquid then flows into the parallel tube and descends, creating a self-sustaining flow that eventually re-enters the microchannel plate where the process starts all over again.

The researchers had thought at first that the tiny bubbles might block the circulation of the liquid, and that small electric pumps might be needed to push the liquid through the narrow channels, increasing the cost and complexity of the system.

But they didn’t, and the result was the ‘pumpless’ liquid-cooling system that, according to Issam Mudawar, a Professor of Mechanical Engineering at the University, removes nearly six times more heat than existing miniature pumpless liquid-cooling systems.

‘We were surprised to see that the dielectric liquid forms really miniature bubbles, so they slip through really fast,’ Mudawar said. ‘The bubbles don’t block the flow, as you would expect.’

Future research will focus on testing various designs to see which configurations work best.