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Vortex tube


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(In vorticity dynamics, a 'vortex-tube' is also a surface in the fluid formed by all the vortex-lines passing through a given reducible closed curve drawn in the fluid - see George Batchelor's book, section 2.6)

The vortex tube, also known as the Ranque-Hilsch vortex tube, is a heat pump with no moving parts. Pressurized gas is injected into a specially designed chamber. The chamber's internal shape, combined with the pressure, accelerates the gas to a high rate of rotation (over 1,000,000 rpm). The gas is split into two streams, one giving kinetic energy to the other, and resulting in separate flows of hot and cold gases.

The "Hilsch" Vortex Tube

Webmaster's notes:

It has recently been suggested to me that credit for this article should be given to C. L. Stong who wrote most of the "Amateur Scientist" columns for "Scientific American" magazine. I had recieved it as a copy of a copy from a friend of a friend etc... One day a bunch of years ago when this thing called the "World Wide Web" got popular, I decided to make this website. It has become surprisingly popular.

I have never actually built one of these, myself. If anyone actually DOES build one based on this information, I'd certainly love to hear about it.

I do know they are commercially available from several manufacturers. I'm sure your favorite search engine can help you find them.

THE "HILSCH" VORTEX TUBE

With nothing more than a few pieces of plumbing and a source of compressed air, you can build a remarkably simple device for attaining moderately low temperatures. It separates high-energy molecules from those of low energy. George O. Smith, an engineer of Rumson, N. I., discusses its theory and construction

The 19th century British physicist James Clerk Maxwell made many deep contributions to physics, and among the most significant was his law of random distribution. Considering. the case of a closed box containing a gas, Maxwell started off by saying that the temperature of the gas was due to the motion of the individual gas molecules within the box. But since the box was standing still, it stood to reason that the summation of the velocity and direction of the individual gas molecules must come to zero.

In essence Maxwell's law of random distribution says that for every gas molecule headed east at 20 miles per hour, there must be another headed west at the same speed. Furthermore, if the heat of the gas indicates that the average velocity of the molecules is 20 miles per hour, the number of molecules moving slower than this speed must be equaled by the number of molecules moving faster.

After a serious analysis of the consequences of his law, Maxwell permitted himself a touch of humor. He suggested that there was a statistical probability that; at some time in the future, all the molecules in a box of gas or a glass of hot water might be moving in the same direction. This would cause the water to rise out of the glass. Next Maxwell suggested that a system of drawing both hot and cold water out of a single pipe might be devised if we could capture a small demon and train him to open and close a tiny valve. The demon would open the valve only when a fast molecule approached it, and close the valve against slow molecules. The water coming out of the valve would thus be hot. To produce a stream of cold water the demon would open the valve only for slow molecules.

Maxwell's demon would circumvent the law of thermodynamics which says in essence: "You can't get something for nothing." That is to say, one cannot separate cold water from hot without doing work. Thus when physicists heard that the Germans had developed a device which could achieve low temperatures by utilizing Maxwell's demon, they were intrigued, though obviously skeptical. One physicist investigated the matter at first hand for the U. S. Navy. He discovered that the device was most ingenious, though not quite as miraculous as had been rumored.

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