Magnetically Stimulated Fluid Flow Patterns Offer Strategy for Heat Transfer Problems
Sandia National Laboratories researchers Jim Martin and Kyle Solis have discovered how to harness magnetic fields to create vigorous, organized fluid flows in particle suspensions. Fluid flow is a necessary phenomenon in everything from reactors to cooling engines in cars. The magnetically stimulated flows offer an alternative when heat transfer is difficult because they overcome natural convection limits. Martin and Solis also demonstrated a heat transfer valve that could potentially control the temperature of computer processors. The two researchers make fluids move by adding a small amount of magnetic platelets to a liquid and applying modest, uniform alternating current (AC) magnetic fields. The phenomenon, which they've termed isothermal magnetic advection, has shown very good results for noncontact heat transfer, and would be useful for cooling microsystems and cooling in microgravity.
Transcript
00:00:00 [Music] research in this laboratory has focused on the effect of magnetic fields on uh fluids and in particular we're interested in the effects of time dependent magnetic fields not just a simple static magnetic field but a magnetic field that has three orthogonal or mutually perpendicular components and each one of these components oscillates
00:00:23 so that the magnetic field goes back and forth the fluids are simple liquids to which we've added a small amount of magnetic particles think a very very very small magnetic confetti in fact when we apply these magnetic fields uh in some appropriate way to these fluids we can stimulate very vigorous uh flow actually can create fluid flow lates now fluid flow is an important aspect of
00:00:46 Technology it's uh it's necessary in giant reactors it's necessary in in wine making it's uh used in nuclear reactors it's used to cool the engine in your car there are many applications where uh having fluids flow vigorously is an important uh part of solving some sort of problem now typically making fluid flow is done with some sort of pump that uses an impel or some kind of mechanical
00:01:10 uh force on the on the fluid and really just shoving it around in some controlled way what's remarkable about this technology is we're not making any kind of contact with the fluid at all rather the magnetic fields are are are indirectly creating fluid flow and in fact the fluid flow patterns that we create are very surprising have very unique SYM symmetries is the type of
00:01:31 emergent Behavior Uh that's similar to the emergent behavior that behaviors that occur in nature such as the murmurations of flocks of Starlings or other such processes here in this uh roughly 1in square glass cuvette we have the uh magnetic platelets that uh we mentioned earlier and as you can see using this permanent magnet they are uh rather responsive so you can see how
00:01:52 they shift around inside the cells we move the magnet so now we'll be adding some uh solvent to this uh platelets uh now and in this case today we're just using some isopropanol it's a good benign solvent uh any low viscosity solvent would work aquous uh Solutions water other alcohols so um typically we just add enough that will bring the uh volume traction of platelets up to a
00:02:20 couple percent so now with our uh prepared suspension we'll just go ahead and place it in the center of the triail uh Helotes magnet assembly and then we can see what kind of float patterns we can [Music] get so now uh We've shown you how how vigorously fluids can uh flow when stimulated by this triaxial magnetic
00:02:57 field um this is already shown to have uh enormous applications for heat and mass transfer we've actually been able to create a thermal valve where we can where we can control the transfer of heat in a fluid by a factor of 100 we can essentially reduce uh heat transfer to almost nothing and we can make heat transfer within the fluid extremely large so for example we could cool some
00:03:19 kind of micro device some sort of high power chip we could allow allow it to heat up very quickly by blocking heat transfer let it come to equilibrium and then transfer the heat away as NE necessary in order to maintain a constant temperature [Music]