What is a vortex tube and how does it work? A vortex tube is a device used to separate compressed air into a cold and hot stream of air; but the main question that many people have theorized is how does this device work.
In 1928 George Ranque, a French physics student stumbled upon this phenomenon on accident while he was performing experiments on a vortex type pump. During the experiment George noticed that hot air was being exhausted from one side and the other side was producing cold air. Eventually the device was forgotten about until 1945 when the German physicist, Rudolph Hilsch published a paper describing the device, eventually causing it to gain popularity and find applications in the industrial world.
The diagram bellow is one of the widely accepted explanations for the vortex tube phenomenon.
When the vortex tube is supplied with compressed air the air flow is directed into the generator that causes spin into a spiraling vortex at around 1,000,000 rpm. This spinning vortex flows down the neck of the hot tube denoted in the diagram as red. The control valve located on the end of the hot tube allows a fraction of the hot air to escape and what does not escape reverses direction and travels back down the tube in a second vortex denoted in blue. Inside of the low-pressure area of the larger outer warm air vortex, the inner vortex loses heat as it flows back to the front of the vortex and as it exits the vortex expels cold air.
The phenomenon is theorized to occur because both the hot and cold streams rotate at the same velocity and direction. This means that a particle of air in the inner vortex makes a complete revolution in the same time that a particle in the outer vortex takes to make a complete revolution. This effect is known as the principle of conservation of momentum and is the main driving force behind the vortex tube. In order for the system to stay in equilibrium air particles lose energy, in the form of heat, as they move from the outer stream to the inner stream, creating the cold air vortex that gets expelled.
If you have questions about Vortex Tubes, or would like to talk about any of the EXAIR Intelligent Compressed Air® Products, feel free to contact EXAIR and myself or any of our Application Engineers can help you determine the best solution.
Cody Biehle Application Engineer EXAIR Corporation Visit us on the Web Follow me on Twitter Like us on Facebook
A manufacturer of automotive power transmission shafts was experiencing frequent failure of high pressure plastic rollers on their spin tester. There are four rollers in a 90° array that center the shaft during spin testing. They exert a pressure of around 1,500psi onto the shaft while it’s rotating at 1,000rpm. This generates enough heat to actually melt the rubber coating on rollers, which means stopping testing (which holds up production) while they change out the rollers. Just for it to start all over again.
Thing was, they wanted to mount the Adjustable Spot Coolers where they could have access to the Temperature Control Valve, but the cold air Hose Kit wouldn’t reach the shaft. So they got a couple of extra sections of the cold air hose…they needed one section of the ‘main’ (shown circled in blue, below) to reach into the test rig’s shroud, and two sections of the ‘branch’ (circled in green) to reach to each roller.
Now, adding too much hose length will start to put line loss on the cold air flow, and it will pick up heat from the environment. But if you just need that extra foot of hose to get the job done, this generally works just fine. The extra foot or so they’ve added (5″ to the main and 6″ to each branch) has solved their problem…they haven’t had to replace a roller since the Adjustable Spot Cooler Systems were installed.
If you look into the history or even the definition of a vortex tube, you’re likely to find mention of a physicist named Rudolf Hilsch. Born December 18th, 1903, Hilsch was a German physicist, professor, and manager of the Physics Institute of the George August University of Göttingen. He received a doctorate degree by the age of 24 and spent his career furthering the advancement and understanding of numerous phenomena of physics.
Although Hilsch didn’t invent the Vortex Tube (the original inventor was a physicist by the name of Georges J. Ranque), he is entwined with their history thanks to a paper he published in 1947. According to lore, this paper significantly changed the understanding and performance capabilities of the vortex tube, eventually being marked as the precursor for identifying a vortex tube as a real potential cooling device. (I’ve made attempts to find this 1947 publication properly translated into English, but to no avail. If you have it or find it, please email it to me at LeeEvans@EXAIR.com! (Original publication in German can be found here.)
Given that vortex tubes are a known EXAIR solution, it seems reasonable that today, on Hilsch’s birthday, we give recognition to this influential physicist and his mark on thermodynamic fluid flow technology. And, although we at EXAIR are connected to Hilsch through vortex tubes, everyone alive has been influenced by his work. This is because Hilsch and a partner (physicist Robert Wichard Pohl) constructed the first semiconductor amplifier in 1938, prompting Hilsch to prove (in 1939) that solid-state electronics are possible. This work paved the way for transistor and solid-state electronics technology as we know it today. Without Hilsch and his life’s work, not only would we not have vortex tubes, we likely would have any electronic devices we use every day.
Here’s to you Rudolf Hilsch. Thank you for your work, your discoveries, and your achievements.
I know I’ve written on the topic before, but customer service isn’t just a department at EXAIR, it’s a priority. And it’s not just a top priority, it’s our only priority.
I’m reminded of the distance between a company like ours and those in other industries whenever I’m required to interact with their service departments. Rather than sound off about a bad experience, I think it’s more fitting, and becoming of our company culture, to give an example of our standard service level.
I fielded a call today from a manufacturer in Georgia. They’ve used a series of Vortex Tubes to cool their product as it moves down a conveyor line for quite some time. Process changes have resulted in greater temperatures and greater throughput, so there is a need to extend the cooling capacity to keep products up to quality. Essentially what was needed was the same product that has worked in the past, just a few more pieces. The only problem was that the model number was unknown.
After a search in our system turned up empty, it came to light that the company has changed names (perhaps more than once), and the most accurate way to determine the model number in question would be through a roll-stamped marking on the generator of the Vortex Tube.
The shop foreman and I walked through the disassembly over the phone, and realized that the Vortex Tubes have been in service for so long, that the roll-stamp had worn off. So, we took it a step further and took measurements of critical dimensions on the generator. I then cross referenced to our CAD files, and determined the unit was a 2 SCFM model 3200 series Vortex Tube. A quick email to the shop foreman gave confirmed model number, pricing, and availability.
Situations like this are a regular occurrence for everyone at EXAIR. If you’re having application difficulties and need a helping hand, we’ll be happy to add you to our list of success stories.