PRESS-NEWS.org - Press Release Distribution
PRESS RELEASES DISTRIBUTION

Magnetic nanoparticles could aid heat dissipation

2013-11-20
(Press-News.org) Contact information: Sarah McDonnell
s_mcd@mit.edu
617-253-8923
Massachusetts Institute of Technology
Magnetic nanoparticles could aid heat dissipation 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 tends to cause the particles to clump together — possibly forming a chainlike structure on the side of the tube closest to the magnet, disrupting the flow there, and increasing the local temperature gradient.

While the idea has been suggested before, it had never been proved in action, Hu says. "This is the first work we know of that demonstrates this experimentally," she says.

Such a system would be impractical for application to an entire cooling system, she says, but could be useful in any system where hotspots appear on the surface of cooling pipes. One way to deal with that would be to put in a magnetic fluid, and magnets outside the pipe next to the hotspot, to enhance heat transfer at that spot.

"It's a neat way to enhance heat transfer," says 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."

While heat transfer can be enhanced in other ways, such as by simply pumping the cooling fluid through the system faster, such methods use more energy and increase the pressure drop in the system, which may not be desirable in some situations.

There could be numerous applications for such a system, Buongiorno says: "You can think of other systems that require not necessarily systemwide cooling, but localized cooling." For example, microchips and other electronic systems may have areas that are subject to strong heating. New devices such as "lab on a chip" microsystems could also benefit from such selective cooling, he says.

Going forward, Buongiorno says, this approach might even be useful for fusion reactors, where there can be "localized hotspots where the heat flux is much higher than the average."

But these applications remain well in the future, the researchers say. "This is a basic study at the point," Buongiorno says. "It just shows this effect happens."

### The team also included Thomas McKrell, a research scientist in MIT's Department of Nuclear Science and Engineering, and Elham Doroodchi, Behdad Moghtaderi, and Reza Azizian of the University of Newcastle in Australia.

The work was supported by the University of Newcastle, Granite Power Ltd., the Australian Research Council, and King Saud University in Saudi Arabia.

Written by David L. Chandler, MIT News Office


ELSE PRESS RELEASES FROM THIS DATE:

Carnegie Mellon computer searches web 24/7 to analyze images and teach itself common sense

2013-11-20
Carnegie Mellon computer searches web 24/7 to analyze images and teach itself common sense NEIL program labels images, learns associations with minimal help from people PITTSBURGH—A computer program called the Never Ending Image Learner (NEIL) is running 24 hours ...

USF researchers show invasive sparrows immune cells sharpen as they spread

2013-11-20
USF researchers show invasive sparrows immune cells sharpen as they spread TAMPA, Fla. (Nov. 20, 2013) - When invasive species move into new areas, they often lose their natural enemies, including the microbes that make them sick. But new research ...

Solar-powered battery woven into fabric overcomes hurdle for 'wearable electronics'

2013-11-20
Solar-powered battery woven into fabric overcomes hurdle for 'wearable electronics' Though some people already seem inseparable from their smartphones, even more convenient, wearable, solar-powered electronics could be on the way soon, woven into clothing ...

Insomnia linked to mortality risk

2013-11-20
Insomnia linked to mortality risk Researchers associate some insomnia symptoms with higher mortality risk in men Boston, MA - Insomnia, the most common sleep disorder, affects up to one-third of the population in the United States. In new findings, ...

Reducing the salt in bread without losing saltiness, thanks to a texture trick

2013-11-20
Reducing the salt in bread without losing saltiness, thanks to a texture trick Want to make bread taste pleasantly salty without adding more salt? Change the bread's texture so it is less dense, say scientists. They report in ACS' Journal of Agricultural ...

Introducing solid foods while continuing to breast feed could prevent child allergies

2013-11-20
Introducing solid foods while continuing to breast feed could prevent child allergies Introducing solid food with breast milk after the 17th week of birth could reduce food allergies in babies, according to University of Southampton research. The research, ...

Hormone therapy could enhance the therapeutic effect of head and facial bone grafts

2013-11-20
Hormone therapy could enhance the therapeutic effect of head and facial bone grafts Bone grafts, which are used to treat head injuries and birth defects, still pose major medical challenges, but scientists are reporting progress toward a new hormone therapy ...

Dismantling Syria's chemical weapons in the midst of war

2013-11-20
Dismantling Syria's chemical weapons in the midst of war Syria no longer has the capacity to produce new chemical weapons en masse, but arms control experts caution that what remains is the more difficult job of destroying the existing stockpile in the midst ...

EORTC head & neck cancer trial shows assessing HRQOL is valuable to both patients and their doctors

2013-11-20
EORTC head & neck cancer trial shows assessing HRQOL is valuable to both patients and their doctors In Europe in 2012, there were an estimated 39,900 new cases of laryngeal cancer and 99,600 new cases of oral cavity and pharyngeal cancers (Feraly ...

New research gives clues of antibiotic use and resistance in US children's hospitals

2013-11-20
New research gives clues of antibiotic use and resistance in US children's hospitals Findings coincide with CDC's Get Smart Week CHICAGO (November 20, 2013) – Two studies published in the December issue of Infection Control and Hospital Epidemiology ...

LAST 30 PRESS RELEASES:

Older teens who start vaping post-high school risk rapid progress to frequent use

Corpse flowers are threatened by spotty recordkeeping

Riding the AI wave toward rapid, precise ocean simulations

Are lifetimes of big appliances really shrinking?

Pink skies

Monkeys are world’s best yodellers - new research

Key differences between visual- and memory-led Alzheimer’s discovered

% weight loss targets in obesity management – is this the wrong objective?

An app can change how you see yourself at work

NYC speed cameras take six months to change driver behavior, effects vary by neighborhood, new study reveals

New research shows that propaganda is on the rise in China

Even the richest Americans face shorter lifespans than their European counterparts, study finds

Novel genes linked to rare childhood diarrhea

New computer model reveals how Bronze Age Scandinavians could have crossed the sea

Novel point-of-care technology delivers accurate HIV results in minutes

Researchers reveal key brain differences to explain why Ritalin helps improve focus in some more than others

Study finds nearly five-fold increase in hospitalizations for common cause of stroke

Study reveals how alcohol abuse damages cognition

Medicinal cannabis is linked to long-term benefits in health-related quality of life

Microplastics detected in cat placentas and fetuses during early pregnancy

Ancient amphibians as big as alligators died in mass mortality event in Triassic Wyoming

Scientists uncover the first clear evidence of air sacs in the fossilized bones of alvarezsaurian dinosaurs: the "hollow bones" which help modern day birds to fly

Alcohol makes male flies sexy

TB patients globally often incur "catastrophic costs" of up to $11,329 USD, despite many countries offering free treatment, with predominant drivers of cost being hospitalization and loss of income

Study links teen girls’ screen time to sleep disruptions and depression

Scientists unveil starfish-inspired wearable tech for heart monitoring

Footprints reveal prehistoric Scottish lagoons were stomping grounds for giant Jurassic dinosaurs

AI effectively predicts dementia risk in American Indian/Alaska Native elders

First guideline on newborn screening for cystic fibrosis calls for changes in practice to improve outcomes

Existing international law can help secure peace and security in outer space, study shows

[Press-News.org] Magnetic nanoparticles could aid heat dissipation