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Sunday, January 9, 2011

More Ranque Hilsch Vortex Tube Experiments

Another busy week has gone by and I have not had a lot of time to experiment but I did manage to do a few things with the Ranque-Hilsch Vortex Tube experimental setup I built last week. As I mentioned this setup is not intended to actually create a hot and cold flow separation but rather to try and figure out what is going on inside the tube. Specifically I am interested in how the counter flow starts at the cone valve and determine how much influence the cone valve shape has on the counter flow. With that in mind I did a few computer simulations using SolidWorks and FloXpress. SolidWorks is a parametric CAD system and FloXpress is a fluid dynamics flow simulation add on to SolidWorks. Because it's a free add on to SolidWorks and not the full version there are limitations to what it can do but the results were interesting. Check out the cool picture below!
Vortex Tube Computer Flow Simulation
The picture above is a side view of a vortex tube that I modeled in SolidWorks. The blue spaghetti wrapped around the inside is the calculated vortex airflow going around the inside of the tube. The air is entering in the upper right and flowing round and round slowly making it's way to the left side where the hot end cone valve is located. If you are not sure what I am talking about click on the Ranque-Hilsch Vortex Tube Wikipedia link and read about what a vortex tube is!
A close look at the above picture shows that there is a counter flow down the middle of the tube that is headed to the right side of the picture. This would be the cold air, or air that is being cooled. Below is another picture from a better angle of the simulation and a video of not only the computer simulation in action but also experimental tests to image the airflow! Using lasers!!

As promised below is another view of the computer simulation. You can see where the start of the counter flow starting back down the middle of the tube toward the Cold Air Hole. Click on the picture for a better view. I stopped the simulation before the tube filled up with all the blue lines to see the flow clearer. As I mentioned a full animation of both views of this simulation are included in the video at the end of this post.

Ranque-Hilsch Vortex Tube Simulation
One of the first things that I noticed about the simulation is the counter flow is rotating the same direction as the primary flow is rotating against the I.D. of the tube. This was news to me because most of the pictures that I have seen on line show it going in the opposite direction. One thing I should mention here is the free version of FloXpress that I am using only allows for one input 'port' and one output 'port'. In other words I can't simulate the gas squirting in from multiple jets and I can't have both the hot end and the cold ends of the tube open. What I did to run the simulation was make the Cold Air Hole the output and the hot end was closed off but much longer than necessary. Making the hot end long gave the air a place to go (down into the hot end) but not actually flow out the hot end. This is as close as I can get to the real world with the software that I have.
If you didn't read my fist post about this experiment HERE you should at least have a look at THIS picture of the setup. It is a clear plastic tube with a movable cone valve on one end, a cold air hole on the other. There are two air inlets at a tangent to the tube inner diameter connected to 2 small variable speed diaphragm pumps. The difference between the picture and the setup this time is I am using only one green 10mw laser with a lens in front of it to make the beam into a fan. The fan is spread into a vertical plane that bisects the tube from the cold air hole end. I used a laser because it illuminates the flow of air and smoke in the tube. Here is a video of the tube running with a the green laser and also the animated computer simulations.

What I noticed with this experiment is the flow that I see in the tube appears to match the computer simulation! Yeah! Also it takes a lot of airflow to build up a counter flow that actually escapes out the cold air hole. Without a lot of airflow the counter flow is drawn back into the primary vortex along the inner wall of the tube. I think that there are two area for improvement of the tube design. The first would be to optimize the cone valve shape to generate a strong counter flow. The second improvement would be to arrange the geometry near the cold air plate and the gas entry points to facilitate the exit of the counter flow gas. Those two things will be what I work on next.
If you have any questions please send me an email at and/or leave a comment here on the blog!


  1. I agree with you on that the design of the cone valve should be altered to optimize a strong counter flow. But would it be possible that additions to the design such as other concepts with relation to airflow and cooling could be applied...

  2. Anonymous,

    Yes I am sure that there are things that can be done. Have you seen this page:

    I have a lot of links at the bottom to various research on the web.
    Do you have any specific modifications to the tube in mind? I'd like to hear them!
    - Otto Belden

  3. Hi Otto, an amazing project! Have you tried pumping water through your tube? Is there any temp separation at all at low flow rates? I have read the paper by "R.T.Balmer on temp separation in liquids" but Mr Balmer did not include any detail regarding temp differences at different flow rates. Would a custom designed water vortex tube would work better with water than one designed for air? Would the cavatation effect also happen? I feel I will have to build one of these and investigate water flow! Thanks for your inspiring blog. Best wishes, Paul

    1. Paul,
      Thanks for checking out my blog. I have read that folks have built water vortex tubes to see if there was a temperature separation and apparently there is to a small degree.
      I'd be very interested in seeing and/or hearing about a water vortex tube if you build one. I'm happy to lend any advice that I can.
      I have done a lot of experimenting with vortex tubes, check out my other blog posts about it and let me know if you have any questions!

      - Otto

    2. Thanks for your quick reply. Your blog posts are excellent and I have been reading them thoroughly. You mention you know of people that have built water vortex tubes. If you have any links to water vortex tube resources please can you include them in your blog? I would be most grateful - I have failed to find any links to water vortex tubes. I still plan on building a vortex tube and investigating any temperature effect with water. Thanks very much, Paul

    3. Paul,
      Thanks for the compliment. I wrote a post awhile ago here:
      That was somewhat of a FAQ page based on questions that I have received about vortex tubes. At the bottom there are some links to info on the web - research papers etc... Also in the side bar of my blog under "Sites I Like" there is this link:
      That website is info from a guy that has built a few vortex tubes and he and I have chatted a bit. On the left hand side of his site there is a "links" link to a lot of info as well.

      In one of those research papers they mention experiments using water and gasses other than air. I encourage you to read them all, there is a lot of interesting information there and it becomes clear after reading them that there is room for experimentation and investigation. It doesn't appear that anyone has completely figured out how vortex tubes work, just predictions of what happens and some theories about why.

      Please keep me updated with what you are doing. I'm very interested and again if you have any questions at all please ask!

      - Otto

    4. Thanks Otto - your help and information resources are much appreciated. I will let you know how I get on. Best wishes, Paul

  4. Hello, Otto. I'm interesting for vortex tubes with water. I'd like to know is it any temperature separation with in-compressible liquids. Also I'm interesting for one-flow VT. Do you know anything about it?

    1. Thanks for the question,
      There is some research that has been done using water. Check out some of the links I mentioned in the comments above. If you don't find anything that is helpful let me know and I'll be happy to help!

      - Otto

    2. Thanks. I'm insteresting this theme about 3 years. And all links by water, I have find are Balmer and Potapov, but Potapov gives no information about temperature separation, tough it is very important, besides hi wrote about effective more 100% - it is not real.
      Last time I try to find any information about one-flow Vortex tubes and again - nothing.
      If you can find anythink else or have any information, please wrote me.
      Best Regards Andrick.

    3. Andrick,

      I'll have a look around and see what I can find in all my notes and papers. As far as I know there has not been a lot of research into VT and water but I have read some research notes about it. If I can find them I'll let you know with a comment here :-)

      - Otto

    4. It will be great. Thanks. - Andrick.

  5. I know its quite late but do you have the solid works files you worked with. I know basics in solidworks but I can't get that holes drilled up so that they are tangential to inside of pipe and at an angle.
    if possible send them to sankarram90[at]gmail[dot]com

    1. Sankar,

      I don't have the CAD files that I used for the simulation but they are easy to recreate. The trick is to sketch on a plane that is perpendicular to the axis of the cylinder then insert a cut one direction "thru all". If you need some help email me and I'll get you going with a CAD model.