Tesla valve is a fixed geometry passive check valve. It lets a fluid flow only in one direction, without moving parts.
This valve gets its name from Nikola Tesla, who invented it in 1920 and in the patent it is described as a series of eleven flow-control segments.
We’ll show you how it works using this model, very similar to the original one.
For over ten years Jaes Company has been providing industrial spare parts and offers every type of valve from leading producers.
Tesla valve is a check valve also called “non-return valve”. It belongs to the category of valves that let the flow move only in one direction.
As shown in our previous videos about hydraulic valves, most check valves, such as swing check valve, usually have a moving plug that gets activated directly by flow pressure. When fluid flows in the correct direction, the plug is open allowing the flow; whereas the plug gets back to the closing position, if the flow starts going the opposite way, impeding the reversal of the flow.
Tesla valve, instead, is a special valve, because it’s the only fixed geometry valve, which means with no moving parts.
As you can see here, when the fluid flows in the right direction, it passes mostly through the main channel with almost no deviation.
If the fluid tries to flow in the other direction we can see for instance the liquid splitting into two different ways; right after one of the flows deviates hitting the other one almost from the front. The two flows rejoin but have lost their energy and flow more slowly. This happens several times, getting the flow slower after every deviation.
Let’s do now a scientific experiment to test the correct operation of the Tesla valve!
In this controlled environment the temperature is stable at 20° C, that correspond to 68° F, at a pressure of 1013.25 hectopascal (hPa) and as a fluid we use some distilled water with colourant to better understand and see how the flow moves. With the stopwatch we’ll see how much time 250 millilitres (ml) take to flow through the valve by gravity alone, in a direction first and then in the other.
Let’s start with the direction that should be the fastest: as you can see, water flows mostly through the primary stream, zigzagging but smoothly. We did the experiment 3 times and averaged the time 250 ml of water took to pass through a Tesla valve and the result is 27 seconds.
Let’s now turn the valve upside down in order to make the water flow in the opposite direction. As you can see, when water splits most of the water flows through the secondary stream. After that, the flow rejoins flowing slightly up through the primary stream. Water keep flowing repeating this process at every stream.
We notice that it has already taken more than 27 seconds of the previous test and after 3 attempts the average time is 42 seconds.
With this experiment we’ve proved that this specific Tesla valve has a flow rate of more than 0.556 litres per minute (l/min) from one direction and a flow rate of less than 0.357 l/min from the other, hence reducing the flow rate by 35.8% changing side in the same test conditions.
It’s obvious that the Tesla valve doesn’t stop the flow completely like a normal check valve, but it can slow down the flow considerably. It’s a good option in conditions where you need to hinder a strong flow for a long period; as a matter of fact, with no moving parts less faults occur.
This valve can be used also in microfluidics, since it would be impossible to create miniscule plugs, hence gaining advantage in scalability, duration and ease of manufacture.
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