Explaining how a Vortex Tube works

In summary, a vortex tube is a device that separates a compressed air stream into hot and cold streams. This is achieved by creating a standing acoustic wave within the vortex tube, where warmer air is pushed towards the outlet nozzle and colder air is pushed towards the middle or back of the tube. This rotation of air also affects the frequency of the acoustic wave. The effectiveness of a vortex tube can be verified experimentally and it can still work with an additional insulated central tube for the return flow. This study also confirms the role of "acoustic streaming" in the process.
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rentier
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I have an interesting(IMHO) approach to explaining how the vortex tube works.
There are a few explanations on wiki, but not a simple and convincing final one.
https://en.wikipedia.org/wiki/Vortex_tube

Normally a vortex tube, that runs well, howls very loud.
It is a kind of aerodynamically peculiarly shaped, twisted and folded "flute" (tangential air inflow, etc.), i.e. standing acoustic wave. If we have an outlet nozzle at the anti-node, more air comes out at higher pressure, adiabatically compressed, i.e. warm, and in periods of lower air pressure, there is less flow of the colder air. I.e. on average, more warmer air comes through.
Therefore the remaining air that flows further (or back, in the middle) is net colder.
The rotation, the spiral-shaped flow, essentially increases the length of the "flute", i.e. affects frequency.

(this could be verified experimentally in a linear assembly, I think.)

  • Is it a sane approach?
  • Does a vortex tube work, if the return flow goes through an additional insulated central tube? (guess yes)
 
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1. How does a Vortex Tube create hot and cold air?

A Vortex Tube works by separating compressed air into two streams, one hot and one cold. The compressed air enters the tube and is forced to spin rapidly, creating a vortex. The vortex causes the air to separate into two streams, with the hot air moving towards the center and the cold air moving towards the outer wall of the tube.

2. What causes the temperature difference between the hot and cold air streams?

The temperature difference is caused by the Law of Conservation of Energy. As the compressed air spins in the tube, it loses energy through friction, causing the hot air to become even hotter and the cold air to become even colder.

3. How does the Vortex Tube control the temperature of the air streams?

The Vortex Tube has an adjustable valve that controls the amount of compressed air entering the tube. By adjusting this valve, the speed of the vortex and the temperature difference between the hot and cold air streams can be controlled.

4. What are the main applications of Vortex Tube technology?

Vortex Tubes are commonly used in industrial settings for spot cooling, such as cooling electronic components or machinery. They can also be used for heating, drying, and even refrigeration in certain applications.

5. Are there any limitations or drawbacks to using a Vortex Tube?

One limitation of Vortex Tubes is that they are not very energy efficient, as they require a large amount of compressed air to produce a small amount of hot and cold air. They also cannot produce extremely low temperatures, making them unsuitable for certain applications. Additionally, they can be noisy and require regular maintenance to ensure proper functioning.

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