The Tesla Valve

Be it known that I, Nikola Tesla, a citizen of the United States, residing at New York, in the country and State of New York, have invented certain new and useful Improvements in Valvular Conduits of which the following is a full, clear and exact description.

Above is the first sentence of a little known patent filed by Nikola Tesla in 1916 for a device that has since been referred to as a Tesla valve. I figured as I’ve spent the last 2 weeks working on adapting this design, the very least I could do is make sure to acknowledge the original inventor.

As I mentioned in my post a few weeks ago, my current project (VADR) is to develop a breath sensor that will work in tandem with other breath collection technologies. When I started on the project, I had envisaged simply sticking a sensor to the inside of a breathing tube using some kind of high-tech ‘tape’.

However, as I researched the chemistry and developed the design of the sensor systems, I realised that I would need to have the sensor encased in some kind of static chamber that would hold the breath sample for a number of seconds.

My first ideas to create a kind of trap seemed, clunky.

When i'm randomly sketching ideas I am not at my most artistic
When i’m randomly sketching ideas I am not at my most artistic

So I moved on, to thinking about creating something that would not trap the breath, but simply impede it enough to get a stable reading.

There are real drawings from what I was trying to work this out.
There are real drawings from when I was trying to work this out.

After a few half-hearted attempts, I quickly realised that I was woefully under-qualified to design a new flow system and anything I made was going to require many, many iterations. So I did what any scientist does and tried Google, searching for a ‘valve with no moving parts’. Which gave me a hit from a scientist’s second favourite website, Wikipedia – on something called a Tesla Valve.

Tesla valve
All the little numbers have captions which I was was going to replicate but then I realised that he called 4 & 5 ‘nipples’ and I couldn’t stop giggling

A Tesla valve uses what is now known as the Conda effect – which is the tendency of a flow to follow the nearest wall. Each of the looping offshoots divides the flow and also creates back pressure on the remaining flow.

The overall effect this creates is that any fluid or gas passing in the ‘wrong’ direction will require greater pressure than in the ‘right’ direction.

This kind of flow control is perfect for my application. I need the flow to pass into a chamber over my sensor and then out of the device and carry on down the breath sampling tube. When the person stops blowing, their breath would be preferentially retained in the chamber.

The valve only works in one direction, so I have not stopped all air movement from the chamber, but as I only need to retain a sample of the breath for a matter of 10-20s this should be more than sufficient to get stable results.

Using the dimensions from Tesla’s patent, I very carefully translated his drawings to a drawing package via a process called ‘tracing’. I then scaled up the 2D drawing to have a tube size which would match a breathing tube. Then (as I showed in my live stream video) I translated this 2D drawing to a 3D structure that was suitable for 3D printing.

Tesla cut off

You can also get a better idea of the 3D-ness of it from this little funky animation I made yesterday. The video below also includes an animation of the flow within the system.

Through the miracle of 3D printing, I’ve had this design made already and I did some quick testing – and it does work. The pressure difference isn’t quite as much as I’d like it to be. There is a difference between blowing into the two paths but it’s very small. But I’ve done some reading and I’m sure that v0.2 will be much improved!

As project VADR is funded by the Research Councils (public money) I feel quite strongly about openness – so if anyone wants to play with this themselves, they can download the STL file HERE. Like everything else in project VADR I’ll keep you updated as I change and improve the design.

5 Comments for “The Tesla Valve”

nb

says:

Wonder if a bundle of these could provide enough one way air flow to be used on the intake of pulse jet engine instead of mechanical flap valves?

Donald M.

says:

Just to let you know, “nipple” is the proper term for a pipe protrusion. In gas engineering, at the curb of a person’s residence is a shutoff valve called a “curb cock.” You can giggle some more before continuing…

In many different disciplines of engineering and manufacturing are a bunch of terms where they don’t mean what they mean in polite society. For instance, less “funny” but worth noting, is in ship building; a “floor” is a vertical surface and a deck is a horizontal surface that we would normally call a floor. Yet again, elsewhere in a ship, a vertical surface is more commonly called a bulkhead. A toilet is called a head, and as in most of architecture, a water fountain is called a bubbler. There are many other terms that are more and less “suggestive,” and some industry terms quite contradict another industries terms, or definitions.

My point is, just wait until you have to use some of these terms in front of a female fellow worker, like I did. And if you start giggling then, you might expect a trip to human resources where you will get written up and have to go through weeks of sexual harassment, like I did. My point is, best to get over the giggles now.

However, your development for a one way valve and it’s application is interesting.

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