Search found 2 matches: Nanofluids

Searched query: +Nanofluids

by macribs
Jul 25 2015 2:21pm
Forum: E-Bike Technical
Topic: Definitive Tests on the Heating and Cooling of Hub Motors
Replies: 2098
Views: 366670

Re: Definitive Tests on the Heating and Cooling of Hub Motor

Hm ferrofluid you say. Interesting. Are there various qualities of ferrofluid or various viscose's? When I searched the forum for ferrofluid I see it mentioned briefly 5-6 years ago, does not appear any was biting.
wikipedia wrote:An external magnetic field imposed on a ferrofluid with varying susceptibility (e.g., because of a temperature gradient) results in a nonuniform magnetic body force, which leads to a form of heat transfer called thermomagnetic convection. This form of heat transfer can be useful when conventional convection heat transfer is inadequate; e.g., in miniature microscale devices or under reduced gravity conditions.

Ferrofluids are commonly used in loudspeakers to remove heat from the voice coil, and to passively damp the movement of the cone. They reside in what would normally be the air gap around the voice coil, held in place by the speaker's magnet. Since ferrofluids are paramagnetic, they obey Curie's law and thus become less magnetic at higher temperatures. A strong magnet placed near the voice coil (which produces heat) will attract cold ferrofluid more than hot ferrofluid thus forcing the heated ferrofluid away from the electric voice coil and toward a heat sink. This is an efficient cooling method which requires no additional energy input.[12]

Ferrofluids of suitable composition can exhibit extremely large enhancement in thermal conductivity (k; ~300% of the base fluid thermal conductivity). The large enhancement in k is due to the efficient transport of heat through percolating nanoparticle paths. Special magnetic nanofluids with tunable thermal conductivity to viscosity ratio can be used as multifunctional ‘smart materials’ that can remove heat and also arrest vibrations (damper). Such fluids may find applications in microfluidic devices and microelectromechanical systems (MEMS).[13]
Ferroflid how it works:


Ferrofluid
by h0tr0d
Mar 30 2014 5:09pm
Forum: E-Bike Technical
Topic: Definitive Tests on the Heating and Cooling of Hub Motors
Replies: 2098
Views: 366670

Re: Definitive Tests on the Heating and Cooling of Hub Motor

liveforphysics wrote: The moment it was full of water, the Sevcon gave a fault for "phase winding short-circuit", and wouldn't run.
For this reason and others, I'm loving more and more oil cooling...