CAMBRIDGE, MA -- Cooling systems generally rely on water pumped through pipes to remove unwanted heat. Now, researchers at MIT and in Australia have found a way of enhancing heat transfer in such systems by using magnetic fields, a method that could prevent hotspots that can lead to system failures. The system could also be applied to cooling everything from electronic devices to advanced fusion reactors, they say.
The system, which relies on a slurry of tiny particles of magnetite, a form of iron oxide, is described in the International Journal of Heat and Mass Transfer, in a paper co-authored by MIT researchers Jacopo Buongiorno and Lin-Wen Hu, and four others.
Hu, associate director of MIT's Nuclear Reactor Laboratory, says the new results are the culmination of several years of research on nanofluids nanoparticles dissolved in water. The new work involved experiments where the magnetite nanofluid flowed through tubes and was manipulated by magnets placed on the outside of the tubes.
The magnets, Hu says, "attract the particles closer to the heated surface" of the tube, greatly enhancing 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 behaves just like water, with no change in its cooling properties. But with the magnets, the heat transfer coefficient is higher, she says in the best case, about 300 percent better than with plain water. "We were very surprised" by the magnitude of the improvement, Hu says.
Conventional methods to increase heat transfer in cooling systems employ features such as fins and grooves on the surfaces of the pipes, increasing their surface area. That provides some improvement in heat transfer, Hu says, but not nearly as much as the magnetic particles. Also, fabrication of these features can be expensive.
The explanation for the improvement in the new system, Hu says, is that the magnetic field te
|Contact: Sarah McDonnell|
Massachusetts Institute of Technology