What is a Trompe?

What is a Trompe?

This is the Ragged Chute hydropower plant
on the Montreal River in eastern Ontario, Canada. It doesn’t look like much from an
aerial photo, but that’s because the most interesting parts of this facility are underground:
two massive vertical shafts and large tunnel connecting the two. Before it was converted
to generate electricity, Ragged Chute was one of the world’s only water-powered compressed
air plants. Starting around 1910, this plant sold compressed air to be used in the silver
mines around Cobalt, Ontario. The way this ingenious facility harnessed the power of
water to generate compressed air with no moving parts is fascinating and its use is seeing
a small revival in modern days. Hey I’m Grady and this is Practical Engineering. On
today’s episode we’re talking about the trompe. This video is sponsored Skillshare.
Click the link in the description to get 2 free months of premium membership and explore
your creativity. More on that later. Compressed air is an excellent way to store
and transport energy. It’s not quite as convenient as electricity for homes and businesses,
which is why you don’t see air lines strung on poles throughout cities, but in certain
situations it makes a lot of sense. This is particularly true in mines, where a variety
of tools and equipment need a consistent and safe source of power. But it’s not just
pneumatic tools; Pretty much every step of the mining process – including exploration,
blasting, ventilation, smelting, and refining – makes use of compressed air as a source
of power. It’s reliable, simple, easy to transport, and often safer than the other
options because it doesn’t have the risk of sparks or explosions that come with electricity
or diesel. We normally get compressed air from… a compressor,
a device that does exactly what you’d expect: uses a mechanism to take outside air and squish
it into a tank. But, air compressors had a major disadvantage to the mining professionals
working in the early 20th century: they didn’t exist (at least not ones that were commercially
available). Also, a compressor is just an energy converter. It takes one type of energy
(usually rotational kinetic energy from a diesel or electric motor) and converts into
potential energy stored in pressurized air. You still need a source of power. So, to be
able to operate a mine using compressed air back in the day would have required both maintaining
a separate source of power and a complicated and custom piece of machinery just to keep
the tools and equipment running. You can imagine how valuable it would be to
be able to take advantage of a natural source of power – falling water – and avoid the need
for complicated machinery and moving parts. That’s exactly what a trompe provided, and
I’ve built a miniature version of one so I can show you how it works. And of course
it’s made of clear pipe so we can see exactly what’s going on inside. The first step is
the water supply. Just like hydroelectric facilities, the amount of hydraulic energy
you can convert to compressed air is based on both the height and flow rate available.
In my case, I’m using a garden hose, but most trompes built for mines or forges took
advantage of small streams or rivers. As the water enters the first vertical shaft
it passes by a series of air inlets. Because of the water’s velocity as it travels down
the shaft, the pressure at these inlets goes below atmospheric. So, the trompe “sucks”
air from outside into this vertical shaft to join the water. The turbulence and surface
tension of the flowing water entrains these bubbles of air and carries them to the bottom
of the shaft. This type of interaction between flowing water and air is fairly complicated
to characterize, and there are lots of situations in engineering where air-water interaction
can cause major problems like in spillways, control gates, and pipelines. But, in a trompe,
this is absolutely essential. Once the air-water mixture reaches the bottom
of the shaft, it enters a horizontal chamber. The purpose of this chamber is to separate
the air and water. The turbulence and velocity are reduced, allowing the entrained bubbles
to rise upwards. This air gets trapped in the collection system while the water continues
out the other side of the chamber and upwards into the second vertical shaft. The purpose
of this shaft is to give the water a way out while leaving the air behind. The height of
this shaft also determines the pressure of the trapped air. I have a video on this topic
if you want more detail, but the summary is that the pressure in a body of fluid doesn’t
depend on the volume, just the depth. So a simple riser like my second pipe here is enough
to hold pressure on the air in the collection system, compressing it just like a mechanical
compressor would. It’s pretty satisfying to see it work. I could watch this all day. Once enough air has collected in the system,
I can open the valve to use it. I should say that this is a scale demonstration, so it
doesn’t do anything of significant value unless you have a really tiny nail gun or
air drill. It’s pretty satisfying to see it work. I could watch this all day. One of the benefits of a trompe over a more
traditional air compressor is related to temperature. In technical terms, a compressor uses an adiabatic
process where a trompe compresses air isothermally. But there’s no need to get caught up in
the vocabulary. If you’re familiar with the behavior of gases, you know that (all
other things staying the same) if you compress a gas, it gets hot. And the hotter the air,
the more moisture it can hold. If you’re familiar with air tools, or just corrosion
in general, you know that moisture is one of a tool’s worst enemies. In a trompe,
however, that heat of compression gets absorbed by the water. So you end up with a much cooler
and dryer source of compressed air, which by the way, is the definition of conditioning
air, something I pay dearly for here in San Antonio, and I’m sure those miners in Canada
appreciated as well. I’m definitely not going to be powering
any of my shop tools with my little demonstration here, and it wouldn’t be a very efficient
way to do it, even if I could. If you’ve got grid power available, it makes sense to
use a compressor designed to take advantage of that. But sometimes you don’t. A trompe
can be useful in off-grid aquaponics and hydroponic systems that need aeration of the water. And,
in fact, the design of my demonstration here came from the late Bruce Leavitt, a mining
engineer who pioneered the use of small trompes for aeration and treatment of mining water
in remote locations without access to electricity. I love to see examples of ancient technology
finding new uses in our modern world. Especially in an age where renewable sources of energy
are at the top of our minds, the trompe is a really cool way to harvest the power of
water for beneficial use. I’ve you’ve been following my channel
for any length of time, I hope you’ve seen the quality of these videos improve. I try
to read every single comment that gets posted on my videos, and I’ve been surprised to
receive a lot of helpful suggestions from fans of the channel genuinely trying to help
me get better at this little hobby of mine, like you should use a fill light in addition
to your key light or you need to fix your plosives or you should add some ease to your
animations. If you don’t know what any of that stuff means, neither did I, until I started
using Skillshare, my favorite online learning community. Trying to learn a new creative
skill online often has you spending more time just curating which resources are useful,
instead of actually learning. Skillshare lets you skip through that hassle and get straight
into moving your creative journey forward, like this class by filmmaker Matty Brown about
using inexpensive tricks to make a low-budget production look great. I have a tendency to
get caught up in technical details, so I really like his free-form style that doesn’t worry
too much about gear and encourages experimentation. I’m an engineer in the truest and most stereotypical
sense, so being able to learn creative skills from people like Matty has been really empowering
to me. If you want to make 2020 a year where you explore a new skill or improve an existing
one, click the link in the description to get 2 free months of Premium Membership from
Skillshare. Thank you for watching, and let me know what you think!

100 thoughts on “What is a Trompe?

  1. Grady, well done sponsorship that is relevant to your content with a good segue. Also, fellow San Antonian, Vaminos Spurs!

  2. This is a technique to create a small vacuum also! Not a household vacuum, but a vacuum chamber that has really low air pressure. The more dense the liquid (like mercury) the greater the vacuum you can achieve. I believe Cody's Lab channel did a demonstration of this a couple of years ago.

  3. How do you determine the height of the first pipe where the hose enters? Is there an equation you can use to come up with its respective measurement?
    Secondly: I was going to ask a question about how the air could be used with respects to plants or crops, but the aeration of water example was precisely what I was looking for. Even if that setup only yields a small amount of compressed air, it should still be useful somewhere.

  4. I have grown to love that EDMish intro over the past year. My neurons get all excited that they're about to be fed yummy stuff.

  5. I'd love to hear more about how the compressed air was transported to the old mines and stored on site. Also what kind of yield theygot in the terms if volume and pressure

  6. This is probably silly but can't you just put the water at the end back into the system and make the process "perpetual'?

  7. I still dont get it. Maybe an animation would help.I usually go to other channels to try to understand what you say. … update I get it now after seeing a 1 min video about it. But still more numbers would be better. This system can be used to clean bodies of water. This is a good supplementary video. But more numbers would be appreciated of how much air does this make a min and how much water used. What is the formula. How much water comes out and it is a sold and I assume it can be narrow again? Bu the system does have a 85% lift back to the source. So does that mean 15% of the water will be air?

  8. How come every time I consider building a model of one of these hydraulic devices, you all do a video.

    Coincidence, I think not…

  9. Water in a compressed air line can turn deadly if it freezes into a plug in a train's brake line and the air past that point can't be released to apply brakes.

  10. Its people like you who have influenced me going into mechanical engineering after being out of school for 10yrs. Love your videos

  11. It would be interesting to see a mathematical breakdown of the the trompe and the recently discussed hydraulic ram pump. It's probably unreasonable to expect to build a small scale system that could generate a practical volume and pressure of compressed air, using a relatively flat water course like a stream or small river and these two mechanisms, but it might be fun to look at just how big such a system would need to be to compete with the standard, consumer-grade electric compressors

  12. Thank you for producing these very interesting videos. I appreciate your work and look forward to learning more about engineering.

  13. I love these water based things. It's also really cool to know there is a content creator from San Antonio which is where I'm at.

  14. This is so cool.. but i have to ask .. does the collapse of the bubbles won't hurt the pipe line after a while?specifically if the pipline made of metal?

  15. I have been a fan of your channel for a few years now. – love it. One question; what number Pollock is behind you? I actually own a Martha Holmes photograph of him, and it's just really nice to see someone who appreciates his art. Keep up the great work.

  16. What is the math to calculate the height to pressure output? Can you direct me to accessible reading material learn how to do it?

  17. Air compressors do not use an adiabatic process, in practice it's a polytropic process (somewhere between an isothermal and adiabatic process). Ideally, we want the process to get as close to isothermal as possible to reduce the energy required for compression. This is done by cooling the air as it's compressed, for example by a water jacket. The n value of an isothermal compression (for air) is 1.0, and 1.4 for adiabatic. The air compressor in our lab runs at ~1.2 (just to give an idea).

  18. Thanks for sharing this video. your see through model was awesome. Do you think you can post your supply list for building it. I'd love to build a bigger one. my friends ranch has 150 ft elevation change it would be awesome to aerate his stock ponds and maybe trying hooking the compressed air into some type of generator.

  19. You make great videos. I enjoy learning about the clever tools and machines that we rely on, and you do a good job of succinctly communicating things.

    You’re the sort of thing I wish my government was funding. Keep up the solid work.

  20. Sir I am seeing ur channel since long …. can u suggest some free energy system of transferring water up to a height of 100 ft …

    The requirement is we have small dam on small mullah and sufficient water can be dropped from a height of 20 ft through a 12 inch outlet and then water is required to be lifted in 4 to 6 inch pipe using hydro energy either through water wheel or pelton pump 50 percent of water may go waste in nullah is not a problem .
    I just want to shift water in large scale through water dropping

    Probably this type of some solution is required

  21. Since you really read all comments I wanna say something here.

    You're awesome and your videos are amazing!

  22. Have you ever built a protein skimmed for a reef tank? I would be curious if using a Tromp is a more efficient method of foam fractionation.

  23. Can I just take a moment to mention how incredibly informative these videos are? As soon as you mentioned the air intake on the top, I understood how it worked and thought it was absolutely ingenious.

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