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Bezaleel
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Quote: Originally posted by Oxirane  | | If gases are miscible, how can Uranium hexafluoride be separated by high speed gas centrifuge? In this case, any gas with density difference could be
concentrated using the same techniques? |
Yes, in principle it could.
But you can tell how not-worthwhile it is, if you consider the enormous difficulties enrichening uranium.
| Quote: Originally posted by Oxirane | | This does not apply to liquids, I suppose? If we have water and alcohol mixture and we centrifuge it, there sould be no separation, shouldn't there?
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It also applies to liquids, but the higher viscosity inhibits the effect of separation (that is weak for gases already). Put in another way: the
potential created by rotational forces in an ultracentrifuge is only small compared to the disordering force caused by thermal motion.
An utracentrifuge is not a device you can create with your neighbour's lathe and some tubing from the junk yard.
[Edited on 14-10-2014 by Bezaleel]
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careysub
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Gas centrifuges are actually complex and rather subtle systems that depend on differential thermal diffusion as well as the force gradient. Each gas
centrifuge is itself a counter-current "cascade" - a good analogy can be drawn to fractional distillation columns were there are repeated constant
condensation/evaporation cycles within the column magnifying separation.
And of course the "gee force" gradient in a gas centrifuge is on the order of 1000 gees. A thousand fold makes a difference.
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Morgan
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Tidbit
"The vortex tube was invented in 1933 by French physicist Georges J. Ranque. German physicist Rudolf Hilsch improved the design and published a widely
read paper in 1947 on the device, which he called a Wirbelrohr (literally, whirl pipe).[3] The vortex tube was used to separate gas mixtures, oxygen
and nitrogen, carbon dioxide and helium, carbon dioxide and air in 1967 by Linderstrom-Lang."
http://en.wikipedia.org/wiki/Vortex_tube
Gas Separation in the Ranque-Hilsch Vortex tube
"The conclusion is reached that the centrifugation of the air, and only that, creates the gas separation detected in the outgoing streams."
http://orbit.dtu.dk/en/publications/gas-separation-in-the-ranquehilsch-vortex-tube(4746df63-077f-4f9e-9cc2-0fa50b6c7c5d).html
[Edited on 15-10-2014 by Morgan]
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careysub
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Indeed, but note that the Hilsch vortex tubes (and related devices) do not operate due to a pseudo-gravity field but rather involve the
conservation of angular momentum among particles of different velocities or masses (depending on design and use).
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phlogiston
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| Quote: Originally posted by careysub |
And of course the "gee force" gradient in a gas centrifuge is on the order of 1000 gees. A thousand fold makes a difference. |
I think you are a few orders of magnitude off.
At a typical 90,000 rpm, assuming a rotor diameter of 5 cm, one gets 452,790 gees, almost half a million.
With a 10 cm rotor, you get 905580.
I have used 100,000 rpm centrifuges for biochemistry experiments in the past. Interesting thought I may have perhaps unknowingly gotten some isotope
separation.
-----
"If a rocket goes up, who cares where it comes down, that's not my concern said Wernher von Braun" - Tom Lehrer |
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careysub
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| Quote: Originally posted by phlogiston | | Quote: Originally posted by careysub |
And of course the "gee force" gradient in a gas centrifuge is on the order of 1000 gees. A thousand fold makes a difference. |
I think you are a few orders of magnitude off.
At a typical 90,000 rpm, assuming a rotor diameter of 5 cm, one gets 452,790 gees, almost half a million.
With a 10 cm rotor, you get 905580.
I have used 100,000 rpm centrifuges for biochemistry experiments in the past. Interesting thought I may have perhaps unknowingly gotten some isotope
separation.
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Yeah, I didn't actually look up any specs or do calculations - I was dashing off a quick post in haste.
The original Kamenev centrifuge had a radius of 0.05 m and a peripheral velocity of 320 m/sec and so generated 200,000 Gs.
Without the temperature gradient and countercurrent circulation of the gas centrifuge you probably would get very slight isotope separation effects.
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jock88
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Would you get Oxygen separating out from N at 1/2 a million gees. Surly yes.
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careysub
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He would have been centrifuging a liquid, not a gas.
Evidence of isotope separation in liquids in an ultracentrifuge seems sparse, and sparsely studied>
Here, however is one paper on the subject. They centrifuged molten indium for 100 hours at 820,000 g's and found a small but detectable a shift in
isotope concentrations between In-113 and In-115 from the bottom to the top.
Attachment: 2011_p089.pdf (401kB)
This file has been downloaded 385 times
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