Originally Published MPMN June 2009

BREAKTHROUGHS

Cooling System for Electronic Devices Provides One-Two Punch

Bob Michaels

While overheating is a curse for electronic devices, cooling components often occupy precious tracts of device real estate and drive up energy bills. But help is on the way. Parker Hannifin Corp.’s Advanced Thermal Systems business unit has developed a two-phase cooling system that it claims offers up to twice the power density of other coolers while occupying half the space.

The two-phase system is based on the principle of latent heat of vaporization, explains Dale Thompson, Parker’s business development specialist in the company’s Climate and Industrial Controls group. “This process is what drives refrigeration and air-conditioning technology, which is a very old science. We are applying our knowledge in this area and developing a completely new application where the technology can be employed.”
Attached to the silicon chip is a heat-transfer component called a cold plate, which consists of a series of macrochannels. A vaporizable dielectric, or nonconductive, fluid flows through the system, where it boils and converts into a gas. This fluid exits the macrochannels through the cold plate as a foamy two-phase mixture. Cooling does not require the fluid to pick up heat as it passes through the channels—a process known as sensible heat. Rather, the fluid changes from a liquid to a gas in a process called latent heat, removing approximately two to four times more heat than single-phase systems.
Conventional cooling systems, Thompson remarks, rely on sensible heat transfer. “While this is a workable solution, capturing heat requires the use of more water or a chiller to create more thermal capacity between the water and the device.” This is problematic, he adds, “because there is a practical limit to how much fluid flow can be attained, and there is a delicate balance between what the design engineer wants and how much heat can be dissipated to keep the device in its thermal envelope.”
Thompson speculates that a host of medical devices and components can benefit from Parker’s cooling system, including oncology linear accelerators, laser systems, graphic processors, electron microscopes, amplifiers, power supplies, and x-ray tubes. “The electronic components in medical devices are complex and expensive, and water leaks can ruin them,” he notes. The advantage of using a dielectric fluid is that it is not reactive to such components; at ambient pressures, it becomes a gas that will not cause them harm. In addition, as a hermetically sealed unit like a refrigerator, the two-phase system does not require maintenance. And, Thompson adds, because it captures and transports heat effectively, the system may be able to eliminate the need for chillers in MRI or CAT systems.

Parker Hannifin Corp.
New Haven, IN
www.powerelectronicscooling.com
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