Sandia National Laboratories has developed a new type of air-cooled heat exchanger that increases CPU efficiency, is immune to dust fouling and can cut power costs.
Heat is the great enemy of electronics. As microchips run at higher clock speeds, engineers are running up against the challenge of keeping components cool in an efficient and economical manner.
But a new cooling method developed by a researcher at Sandia National Laboratories opens the way for a variety of applications, from higher-speed chips to more power-efficient electronics and refrigeration systems. The Air Breathing Heat Exchanger, also known as the Sandia Cooler, uses a unique system of rotating fins to shunt heat away from microelectronics.
Unlike a conventional heat exchanger, which is a fixed device with cooling vanes designed to move heat away from a processor through convection, the Sandia Cooler uses rotating cooling fins attached to a shaft that conveys heat up from the processor. Movement is important because it helps reduce the boundary layer of air that clings to an object such as a heat exchanger, said the cooler’s inventor, Sandia researcher Jeff Koplow.
In a static air-cooled heat sink or cooling vane, a layer of warm air will accumulate around the device like an insulating blanket, greatly reducing its ability to conduct heat away from electronics. Although there are methods that use directed jets of air to help improve cooling by blowing away the accumulated warm air, they tend to be noisy and power-hungry, Koplow said.
The Sandia system’s high-speed rotating fins reduce the boundary layer by a factor of 10, which greatly improves cooling in a much smaller device, he said. The fins are designed to be aerodynamically efficient, which increases their ability to shed heat and reduce noise.
Koplow developed the cooler because he felt that progress in cooling systems for electronics was incremental at best. “Why is the performance of air-cooled heat exchangers so lousy?” he said.
The Sandia coolers have potential uses in a variety of cooling applications. The small high-speed cooling fans used to cool most electronics are not very efficient, Koplow said. By making the heat exchanger rotate, the fins, which are only a few inches across, can cool a processor and provide air flow in an electronics cabinet. Another advantage to the cooler is that the tiny engine that drives the fins is very power-efficient.
Moving fins are also resistant to dust, which can collect on and foul passive cooling vanes. Dust fouling is a common problem with many computers, Koplow said. As it builds up on cooling vanes, it acts as an insulator, diminishing the device’s ability to shed heat. When heat exchangers stop working efficiently, computers begin to slow down, as the processor reduces its clock speed to keep from overheating.
Besides keeping computers cool and free of dust, the Sandia Cooler technology can also be applied to systems such as air conditioners, which also suffer from dust collecting on their heat exchangers.
Air conditioning efficiency is important for data centers, where a considerable part of the power costs go toward cooling. Koplow estimated that more efficient heat exchangers for processors could drive down a data center’s power consumption by as much as 20 percent and greatly reduce noise. Making an entire building’s heating and cooling system more efficient would lead to even greater efficiencies, since up to half the power needs for server farms go to their HVAC systems, he said.
Despite its promise, Koplow cautions that the technology is still immature. One potential hurdle that must be analyzed is manufacturing. Making the fins and their motor is not very complex, but the device does spin at several thousand rotations per minute and requires tight, precise spacing for the air gap. Developing the means to produce them cheaply and in quantity remains a challenge, he said.