Researchers at the University of Alabama Huntsville (UAH) have patented a passive cooling system for computer processors using 3M’s Fluorinert FC-72. The press release calculation has it that the passive cooler could save U.S. consumers more than $6.3 billion per year in energy costs associated with running their computer’s cooling fans.

Passive Processor Cooling System. Left to right, Nguyen Smith Wang.  Click image for the largest view.  Image Credit: UAH.

Passive Processor Cooling System. Left to right, Nguyen Smith Wang. Click image for the largest view. Image Credit: UAH.

The system, while clever, is basically a convection system circulating 3M’s Fluorinert FC-72 liquid through channels in a computer’s processor and then out to a heat sink that serves as an external radiator.

The press release has other economic claims like the passive cooler could save computer manufacturers $540 million annually in manufacturing material costs by eliminating fans and associated wiring. Energy and materials savings are based on a future in which 300 million machines are in use in the U.S.

Americans might not be hugely impressed, but Dr. James E. Smith Jr., a UAH chemical engineering professor emeritus who is working with graduate students to optimize the system pointed out there is an added global benefit to the reduction in electricity consumption.

Dr. Smith says, “If you can do this for the world, we can save a whole lot of pollution globally. Think of what could be done in China alone.” He’s right, in China just keeping up with growing electricity demand is a huge economic undertaking.

Of great interest is the Fluorinert FC-72, the 3M brand name for an electronic cooling liquid and electrical insulator. FC-72 is a colorless, odorless, biologically inert and chemically stable dielectric liquid that is nonflammable and has a boiling point at 56º C (133º F).

In the passive system’s convection cycle, heat from the computer processor vaporizes liquid FC-72. The light vapor moves to a heat exchanger, releases its heat into the environment and condenses back into the heavier liquid, then moves to a holding tank, from which the liquid travels to the processor once again to complete the cycle.

For his chemical engineering master’s thesis, student Cuong Nguyen compared the passive cooling system with traditional solid-state passive cooling and traditional fan cooling in computers running for up to 12 hours under no load and heavy load conditions. The system was tested using modified Intel Pentium 4 and Core i3 processors.

Nguyen explained, “Our system can absolutely work, and it can work for 12 hours in a stable condition.” His thesis experiments found that a near steady state 56º Celsius processor operating temperature was achieved using the system. The acceptable range of processor operating temperature is 50-90º Celsius.

“When we remove the cooling fan, it saves material costs, but it also eliminates the noise, vibration and dust contamination of fan cooling,” Nguyen says. “When you remove the dust, you remove the chance that it can build up. Build up of dust can destroy the electronic components.”

Optimized liquid passive cooling has a range of potential applications beyond home and business computers. The system could prove useful in temperature stabilization of electronic guidance and propulsion controls in outer space, as well as finding applications in efficient 21st century power delivery systems here on Earth.

Dr. Smith said, “When you look at the power transistors required for the smart grid, for example, this system could have application there, and there are other applications in that area, too. Wherever you want to make high power in a small area, that is a potential application.”

The concept looks very useful across a wide range of applications running in the temperature zone. FC-72 looks like a refrigerant with a high boiling point that hasn’t yet hit its stride. Congratulations are in order, but getting and keeping a passive cooling patent looks like it will need something really unique that isn’t discussed in the press release. Perhaps there is more to tell?


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