BALLISTIC CONDUCTION, Nanostructures and Stirling Engines

[vamoose]

Wasn't sure wether to put this one out there or not, but what the hell...

First have a read of these excerpts from wikipedia
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Thermal properties

Main article: Thermal properties of nanostructures
All nanotubes are expected to be very good thermal conductors along the tube, exhibiting a property known as "ballistic conduction", but good insulators laterally to the tube axis. Measurements show that a SWNT has a room-temperature thermal conductivity along its axis of about 3500 W·m−1·K−1; compare this to copper, a metal well known for its good thermal conductivity, which transmits 385 W·m−1·K−1. A SWNT has a room-temperature thermal conductivity across its axis (in the radial direction) of about 1.52 W·m−1·K−1, which is about as thermally conductive as soil. The temperature stability of carbon nanotubes is estimated to be up to 2800 °C in vacuum and about 750°C in air.

Thermal conductivity measurements

Measurements show a single-wall carbon nanotubes (SWNTs) room-temperature thermal conductivity about 3500 W/(m·K), and over 3000 W/(m·K) for individual multiwalled carbon nanotubes (MWNTs). Addition of nanotubes to epoxy resin can double the thermal conductivity for a loading of only 1%, showing that nanotube composite materials may be useful for thermal management applications.
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So - With the recent discovery of and increasing knowledge about different allotropes I wonder if anyone is attempting to use their unique properties in the field of stirling engines. Certain types of nanotubes have a surface thermal conductivity approaching a magnitude of 100 times (10000%) greater than that of an anodised aluminium surface. If one was able to 'anodise' (or coat) a metallic surface with tubes so that their tube openings were facing outwards (looking like a honeycomb) (I think that is the direction indicated, or actually it may be on their side (that would make it easier)) then you would be able to create significantly smaller, highly effective heat exchangers and regenerators and have more freedom in locating them in desirable locations relative to different stages in the cycle. (They have good temperature stability and are, from what I’ve read very structurally robust)(for such small guys they pack quite a punch)

Would it also be possible to 'dope' certain metals or surfaces with certain types of nanoparticles, or make a metal/nanoparticle 'amalgam', to improve material conductivity.

What about incorporating small particulates (nano particles, carbon nanotubes, buckyballs) into the working gas. The particles would be generally evenly dispersed due to gas turbulence and may, more effectively 'conduct' heat in or out through interaction with heat exchangers and the gas. This may change/improve the thermal properties and dynamics of the working gas.
Also the introduction of say, buckyballs into the gas could potentially have an effect of increased lubrication at rub points, acting like little ball bearings, reducing friction losses and ware.

I know its not in the realm of possibility for tyre-kickers such as myself to attempt (and pay for) such investigations, but I guess some institutions and companies can afford it and may wish to, (they may already be doing so).

Does anyone think that these potential approaches have validity, and are there any Nano Brains out there that may wish to contribute to this discussion??

vamoose


http://en.wikipedia.org/wiki/Carbon_nanotube
http://en.wikipedia.org/wiki/Thermal_pr ... structures
http://en.wikipedia.org/wiki/Phonon
http://en.wikipedia.org/wiki/Allotropes_of_carbon

[Jerry]

I hope I'm wrong here, but I think the use of nano-tubes as a metal treatment is a bit beyond a home machinist at this point in time. That being said, I definitely look forward to being able to make use of their thermal properties at some time in the hopefully not too distant future.

I know there are already some spray on applications for electrodes, but I don't think there's any manufaturer selling such a substance to the general public at this time (proprietary methods and patents will keep nanotubes tied up within industry for a while yet).

[Ian S C]

Never say never, I seem to have heard of microscopic size stirling engines, either built or being developed, theres a whole world of developements not too far away, just need the odd billion dollars for R&D, heres me I think things are getting expensive when the budget goes over $NZ10. Ian S C
Have a look at nanotechnology stirling engine on google.

[aero]

There are companies that sell commercial carbon nanotubes and have been doing so for years, if you Google carbon nanotubes and graphene you will find vendors some lab supplies some larges scale. They have been using carbon nanotubes to make tires for instance and sell them by the metric tom. However they are unlikely to send samples to a private individual but if you have a company or a school?

[fullofhotair]

Really amazing stuff.Are you familiar with Light Transmitting Concrete?It is concrete combined with optical fibers.The fibers make up only 4% of the volume.Some light actually comes throught concrete blocks. Carbon fiber comes in different forms. Ceramic matrix composite is one form.It is elastic for a ceramic and is a good thermal insulator.What if you made a cylinder out of C.M.C. and put these nanowire strands in it like they did with the concrete,but just at the cold and hot ends of a stirling engine.Super thermal conduction at the ends and insulated in the middle.

[vamoose]

Nice idea!
I do vaguely recall hearing about light transmitting concrete somewhere, now that you've reminded me. Pretty cool innovation.
Also maybe using Ceramic matrix composite as a piston (it can have a low friction coefficient in certain forms i think) with nanotubes at the end, could be a good approach of optimising regeneration at the surface and reducing unwanted heat losses to the external environment. It could also be useful in displacers and double acting pistons and engine block locations to stop wasted, hot/cold side thermal transfer through the engine chassis and components. It looks like it has some really nice mechanical properties and has the great thermal tolerance that comes with being in the ceramic family. It may also be useful in burner designs.

vamoose


http://en.wikipedia.org/wiki/Ceramic_matrix_composite
http://en.wikipedia.org/wiki/Translucent_concrete

[vamoose]

Here are some quick youtube vids that are to do with the topic..


Quick and worth a look
http://www.youtube.com/watch?v=yvAIxE3O3CU
http://www.youtube.com/watch?v=Sju4dFCZfQs
http://www.youtube.com/watch?v=NpVV-eoMIA4

A funny one from MIT. These guys must be smart, because they're definitely not actors
http://www.youtube.com/watch?v=dzwI-ZuHXtE

A little bit of a snore but I found it interesting none the less. (9 mins)
http://www.youtube.com/watch?v=S-tZsXWj3aA

I put this in for NerdyEE if he's checking out this topic, I wouldn’t call it relevant though..
http://www.youtube.com/watch?v=bPQi8WGL6IE

vamoose

[vamoose]

Nano Stirling Engine powered by Laser

Extract-
A Stirling engine in the microworld: In a normal-sized engine, a gas expands and contracts at different temperature and thus moves a piston in a cylinder. Physicists in Stuttgart have created this work cycle with a tiny plastic bead that they trapped in the focus of a laser field.

http://nanopatentsandinnovations.blogsp ... t-few.html

[vamoose]

With the use of nanoparticles the sun can create steam from water,
without raising its temperature significantly!

Another vote from me, for nanostructures... and ballistic conduction.

http://www.popsci.com/science/article/2 ... oparticles

Was not sure how to directly equate this article to stirling engines at first, but with a little imagination it starts to look pretty interesting!
vamoose