The Hilsch tube is not often mentioned anymore. It is a T-shaped arrangement of three tubes. A gas is led in through the stem of the T. Vanes inside use centrifugal force to direct the faster moving molecules to one side, where the exit tube is bigger, and the slower ones to the thinner tube on the other side. In practice you can easily feel the difference in temperature of the two outputs. Originally the Hilsch tube was presented as a challenge to thermodynamics, like Maxwell's demon. It has been successfully explained, although I don't now remember what the explanation was. My question is this: Could the Hilsch tube be used to separate isotopes of the same element? Not to put too fine a point on it, could it be used to refine U235 from natural Uranium? Could anyone figure out how it would compare to other methods of doing this?