Sandia Air-Bearing Heat Exchanger starts cooling revolution

Incredible progress announced for processor cooling, as Sandia takes their cutting-edge heatsink design for a spin.

In a surprising announcement, the trusty heatsink has been declared obsolete by researchers at Sandia National Laboratories. Heatsinks and fans are not efficient enough to be practical if processing performance is to increase, claim Sandia researchers, and as an alternative they're offering a brand-new design – the Sandia Cooler.

The imaginatively-named Sandia Cooler comes with a much more descriptive technical name; the "Air-Bearing Heat Exchanger", and aims to defeat the classic "Fin Fan Heat Sink" (FFHS) grip on electronic component cooling.

Conceptually the idea is solid; traditional FFHS heatsinks involve a large array of fins and a fan that blows air across them. Heat is transferred from fins to atmosphere by this moving air in a process called diffusion, and thus the hot component is cooled. But this traditional technique has been used for forty years with very few innovations, and is marred by one large problem – hot air 'sticks' to the fins, and creates a large barrier that prevents efficient heat exchange, even with high-RPM fans.

In addition to inefficient heat exchange comes the problem of dust, referred to as 'heatsink fouling' by Sandia researchers in their very detailed whitepaper (PDF), which accumulates within FFHS fins and reduces the effectiveness over time without constant maintenance. The fan remains relatively dust-free due to its constant motion.

Sandia's Air-Bearing Heat Exchanger sidesteps the FFHS heat exchange and dust problems by combining the two functions of heatsink and fan; creating in effect a spinning heatsink. A large base plate mates with the heat load (in this case a processor) and rests underneath the impeller platen, separated by a 0.03mm layer of air. Described in the whitepaper as a "hydrodynamic gas bearing", it's similar to the effect used in an air hockey table, and is the main effect in keeping hard drive discs stable.

Mounted to the impeller platen are the cooling fins and a brushless DC motor which spins at several thousand RPM, drawing cool air through the centre and then expelling it to the sides of the device. It uses centrifugal forces to reduce the air barrier over the fins by up to ten times, offering hugely increased cooling performance. The Air-Bearing Heat Exchanger does not require heatpipes due to the exceptionally short path between base plate and cooling fins, resulting in increased efficiency per square inch.

"The Sandia device architecture circumvents the poor efficiency of small, high-speed fans by using the mechanical work provided by the motor to directly generate relative motion between the heat exchanger structure and the surrounding air." – Whitepaper, pg11

Sandia claims that their first prototype has a thermal resistance of only 0.2C/W compared to a typical FFHS at 0.6-0.8C/W, a threefold decrease, and researchers believe that "a 2nd generation prototype could readily achieve a thermal resistance of ~0.1 C/W in a device of the same size."

It's also exceptionally cheap to manufacture, as "the heat-sink-impeller is a monolithic structure that could be fabricated by die-casting", the whitepaper claims. Interestingly the paper mentions that the power consumption of the device is slightly higher than a FFHS per RPM, and the presence of a shroud makes no impact on cooling performance.

This device has the potential to revolutionise the consumer PC market, but also offers huge potential savings for the IT industry – it can be used with air conditioner compressors to reduce energy bills, or any other device that requires quiet, reliable cooling. Sandia forecasts that if "Air Bearing Heat Exchanger technology proves amenable to size scaling, it has the potential to decrease overall electrical power consumption in the U.S. by more than seven percent."

An airconditioner's copper compressor coil with Sandia device mounted.

While the Sandia device has not made it to full-scale production, the company is searching for investors and continues work on its second prototype Air-Bearing Heat Exchanger. We cannot wait.