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Vortex cooling / heating tubes Answered

I am currently gathering information about vortex tubes for my repulsine project.
There are plenty to choose from on a commercial base but I struggle to find any technical drawings with proper dimensions.
Several home made varities can be found as well but wither with poor performance or incomplete drawings.
So I was thinking that someone here either uses a commercial product at home or work and might be able to take some basic measurements for me?
I am most interested in the relation between inner tube diameter and lenght for the hot and cold ends as well as the size for the vortex chamber itself.
If there is an orifice used on the cold end the hole diameter would be required as well.

My aim is, based on a properly working original, to create a device that might be less efficient but can be used without a compressor.
Would like to see, correct transfer of dimensions given, a vortex tube like system was used in the repulsine.
Some old documents state that there was a "seperator" which removed "heavy air particles" and created a temperature differencial between top cone of the repulsine and the wave disks.

13 Replies

Downunder35m (author)2015-09-27

Just a little update to keep it alive:
I waste now about a roll of filament for various prototyps but still fail to get any significant temp difference between hot and cold air outlet.
The best I managed with a hyperbolic hot end and that was just 10 degrees of difference.
At this stage I tend to say that my compressor is underrated for the job, only around 6.5bar and it struggles to keep the pressure up with the tube in use.
According to the stuff on the net they start with at least 8bar and massive air volumes.
On the other hand, going small should overcome the problem as many commercial versions show.

I also came up with a slightly different theory on how these tubes actually work.
IMHO it is not a matter of spiraling air that somehow exchanges heat.
I think it is a matter of pressure differencials.
Increasing pressure increases the heat and releasing compressed air cools it down - you can check that with a small nozzle at the end of a bigger tube, the tube will cool down while the compressed air escapes.
The hot air vortex is caused by friction and the fact that the air spirals much tighter towards the end of the tube - it increases the pressure.
The cold air part is at the same level at this stage and actually just a part of the hot air stream.
When the stream is diverted at the end of the hot end, the remaining air is forced back into the hot vortex.
Inside this vortex however is a much lower pressure - the airstream cools down as is basically moves through a tiny hole into a big void.
But again, this is only my thoughts as I lack the equippment to test this ;)

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Downunder35m (author)2015-09-18

I have done some more test but can't really say I am satisfied.
The air from my compressor comes out @7bar and 36°C.
The hotend air after a lot of tweaking is about 24°, cold end 21° but the glass tube on the hot end reaches up to 60° in the first section.
Back to the drawing board to get more inlet speed and to try conduit pipe for the next hot end.
Funny how something that simple in theory can be so hard in the real world LOL

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rickharris (author)Downunder35m2015-09-19

Looks like your air speed isn't fast enough and possibly your hole is too small thus allowing cold molecules to mix in with the hot.

I would expect glass to have a higher temp then metal due to lower thermal losses, But your doing the experimentation.

Look forward to the instructable.

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rickharris (author)2015-09-18

As I said earlier I know very little practically about this but some time ago did look up the theory, As I understand:

The effect is created because hot air is less dense than cold air this results in centrifugal force forcing the cold air molecules to the outside of the rotating air stream leaving the hotter molecules nearer the center. As ambient air always contains some molecules that are more energetic than others there are always some that can be separated.

The two streams are separated by a physical barrier, essentially a washer with a small diameter hole compared to the vortex chamber diameter, such that hot molecules are driven to one side and cold to the other.

I assume the efficiency is a factor of the speed of rotation and the efficiency of the size of the separating barrier. A lower rotational speed needing a smaller barrier hole. perhaps if the hole were an iris you could tune it to the system.

What surprises me is the level of temperature difference that can be achieved.

I can't see this working at low pressure by the nature of the device itself. even high volume of air isn't going to give you the necessary high rotational speeds required to separate relatively light molecules that are at a relativly close density.

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rickharris (author)rickharris2015-09-18

Forgot my technical drawing!

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rickharris (author)rickharris2015-09-18

You kind of got my attention with this and I found these 2 Youtube presentations, one shows the worked maths to demonstrate this is possible and the other shows the air flow in a perspex tube of this kind.

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Downunder35m (author)rickharris2015-09-16

I have seen that and agree with most of the comments....
And the dimensions are far too long to be usable on a small scale.
As I said, most sites offering info about it provide educated guesswork at best.
I can create a long pipe and a vortex chamber, no problem - the problem is finding the right dimensions for the best cooling / heating.
Checking commercial ones and they are only a fraction of the lenght, yet offer a temp difference of 100° or more between cold and hot end.
The stuff made on the web (what I found so far) is lucky to make 5 or 10 degree difference.

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rickharris (author)Downunder35m2015-09-16


is only 15 cm long. Not something I have ever tried to make although I did once look up the theory out of curiosity.

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Downunder35m (author)rickharris2015-09-17

Nice find, I did not see in my searches.
Although they say 15cm on the pics it is far longer lol.
Sadly there are no dimensions or I missed that bit, will have a better read tonight with more time.
But so far I was able to at least get some baselines from my first model:
You need a lot of pressure and (at least for my model) quite a high air flow as well.
But the most important bit that was nowhere metioned is that there should be no pressure drop!
The means if you feed 6bar into the tube, the combined pressure on the outlets should be as close to this as possible.
If the pressure drop is too high the air just comes out at the same temp it went in.
So, the big problem is to modify the prototype so the speed of the incoming air is maximised while at the same time making sure the outlets are small enough to keep the inside pressure levels.
Another interesting thing was that the cold air outlet starts to work as a suction port if the hole is getting too small.
This shows the vortex inside is working as it creates a low pressure zone on it's inside :)
Once I got that bit figured out and am able to produce a temp differential of at least 20° I will try to explore options to do this without the high pressure so a normal fan or similar can be used to feed the tube.
Will get much bigger though...

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kelseymh (author)2015-09-16

I'm curious. Is this for a real project, or some wacky attempt at beating thermodynamics? I only ask because when I tried to look up "repulsine", what I got was stuff about some crackpot Nazi engineer and UFOs :-)

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Downunder35m (author)kelseymh2015-09-16

Well, you did not search good or long enough ;)
Victor Schauberger was forced to work for the Nazi dictatorship, but that was AFTER he made his greatest inventions.
So, yes it is for a real project, in fact due to a lack of easy to use info I started to experiment with my own design.
I try to get a better understanding of thing invented and proven be have worked but that were forgotten since. ;)

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kelseymh (author)Downunder35m2015-09-17

Cool! If it's something real (an actual heat engine that works efficiently without moving parts), I really look forward to reading more about it, and seeing your I'ble when it's done.

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