According to a news release from the Massachusetts Institute of Technology, magnetic nanoparticles could aid heat dissipation. Cooling systems typically depend on water pumped through pipes to eliminate unwanted heat. Researchers at MIT and in Australia discovered a method of improving heat transfer in such systems by utilizing magnetic fields, a technique that could keep system failures from happening. The system could potentially cool everything from electronic devices to advanced fusion reactors.

The system depends on a slurry of small particles of magnetite, a type of iron oxide.

According to Lin-Wen Hu, associate director of MIT’s Nuclear Reactor Laboratory, the findings are the climatic stage of many years of research on nanofluids. The new research involved experiments where the magnetite nanofluid moved through the tubes and was maneuvered by magnets located on the outside of the tubes.

Hu notes that the magnets “attract the particles closer to the heated surface” of the tube, significantly improving the transfer of heat from the fluid, through the walls of the tube, and into the outside air. Without the magnets in place, the fluid acts just like water, with no alteration in its cooling features. “We were very surprised” by the amount of improvement, Hu posits.

Normal techniques to raise heat transfer in cooling systems make use of features like fins and groves on the surfaces of the pipes, augmenting their surface area. That offers some enhancement in heat transfer, but no nearly as much as the magnetic particles. Plus, production of these features can be costly.

The reason for the betterment in the novel system is that the magnetic field tends to result in the particles clumping together — likely developing a chainlike structure on the side of the tube nearest to the magnet, upsetting the flow there, and raising the local temperature gradient.

“This is the first work we know of that demonstrates this experimentally,” Hu notes.

She adds that this system could be valuable in any system where hotspots emerge on the surface of cooling pipes. One method of handling that would be to insert a magnetic fluid, and magnets outside the pipe next to the hotspot, to improve heat transfer at that spot.

“It’s a neat way to enhance heat transfer,” notes Jacopo Buongiorno, an associate professor of nuclear science and engineering at MIT. “You can imagine magnets put at strategic locations,” and if those are electromagnets that can be switched on and off, “when you want to turn the cooling up, you turn up the magnets, and get a very localized cooling there.”

This technique could even be helpful for fusion reactors, where there can “localized hotspots where the heat flux is much higher than the average,” according to Buongiorno.

Other methods of improving heat transfer, like moving the cooling fluid through the system more rapidly, utilize more energy and augment the pressure drop in the system.

The study’s findings are described in International Journal of Heat and Mass Transfer.