Tesla's "Ambient Heat Engine" Experiment

[Tom Booth]

I like your theories!
I do agree with the cooling by expansion part. It would take a lot of testing to get it right though. Especially for it to be a closed cycle. Because if it doesn't cool down enough you end up with continually hotter and hotter cycles. And there isn't very much separation of zones in a rotor, the cold side will heat up pretty fast as well, just from conduction.

Well...

I suppose that could be a problem, but there are materials with very low heat conductivity. Also,

Well, take this experiment I did recently:

https://youtu.be/LG09AXAjpio?si=l2rEo6Pib-XARWlA

Exactly why, I'm not entirely certain, but I'm heating the hot side of the engine almost continuously with a propane torch. That's about 3,500° F.

Styrofoam has a melting temperature of less than 500° F

I don't think the expansion side (power cylinder) ever got anywhere near hot enough to melt the Styrofoam, but at any rate, however hot it may have gotten, INSULATED, with no external cooling, the engine kept on running. The heat never built up enough to melt the Styrofoam, if it ever built up at all, which it seems never happened.

After making that video, I removed the Styrofoam and the power cylinder still felt cool to the touch.

So... To me that looks like by expansion cooling alone (including conversion of heat to "work"), that is, with no external cooling, the engine was able to maintain a temperature difference of at least a few thousand degrees, seemingly indefinitely.

My personal opinion, based on a lot of observations and experiments, is that these engines act like heat pumps or a vapor/compression/expansion refrigeration system.

While expanding into the power cylinder, the working fluid is becoming cold enough to absorb heat away from the cylinder walls in the same way the expanding gas (refrigerant) passing through an expansion valve draws heat away from the walls of the evaporator tubing.

144037528_s.jpg (67.54 KiB) Viewed 11656 times

So if some heat is conducted, if cooling is actually taking place, the little bit of heat that might be conducted across a mostly non-conductive medium might be inconsequential.

...
I would love to find a way to run one rotor inside another. As that would solve a few issues for my plan. So if you have any thoughts on that I'd be happy to hear/read them.

Not sure what you mean or what the purpose of that would be.

[Jack]

Well if you're thinking of turning that drawing into a rotary design you'll have to run a rotor inside a rotor.

[Tom Booth]

Well if you're thinking of turning that drawing into a rotary design you'll have to run a rotor inside a rotor.

Well,...

That might be possible.

There was a patent or patent application for a two stage duel rotary vane compressor

Patent-of-a-two-stage-dual-vane-compressor-3.png (101.79 KiB) Viewed 11624 times

But what I had in mind was not that, but similar in that the vanes would be "shared" and the vanes would travel in a grove, but what I drew would look like a break rotor with the vane guide a disk in the center of a stationary rotor, rather than a circle, and with the vanes sliding from side to side rather than in and out from center.

Similar to a cylindrical or barrel cam:

zylindernutkurve1.gif (544.24 KiB) Viewed 11624 times

Imagine my drawing wrapped around a cylinder similar to the above gif but the vanes traveling in the grove and cylinder stationary.

duel-vane-engine.jpg (558.43 KiB) Viewed 11617 times

[VincentG]

Tom could you perform the same test with the engine not running and observe the temperature of the expansion side? Seems like a really simple way to get conclusive results.

[Tom Booth]

Tom could you perform the same test with the engine not running and observe the temperature of the expansion side? Seems like a really simple way to get conclusive results.

Conclusive of what?

I mean, if the piston isn't moving, no heated air is going much of anywhere, to heat anything or otherwise.

Anyway, why not? It could be done, just kind of seems like apples to oranges, though I did some similar experiments with LTD engines running and not running on ice (ambient heat), which ended up getting me banned from the physics forum.

Logically, I would think what I say here would also be true of an LTD. That is, if you have an LTD engine just sitting on a cup of ice, the ambient heat from above should reach the ice more slowly. The displacer is an insulator and just sitting there covering the ice keeping it cold. Not running, the engine is just a lid on an ice chest keeping the outside hot air away, so the ice should melt more slowly.

With the engine running, on the other hand, the warm ambient air in the top is constantly being exchanged with the cool air below the displacer. That would be like lifting the lid on an ice chest up and down fanning the ice with the warm ambient air. So, the ice should melt faster when used to run the engine.

However, IF the engine is actually actively converting the ambient heat into mechanical work and/or acting as a heat pump expanding the air and taking heat away from the cold side, or somehow preventing the heat from ever reaching the cold side (in spite of the active and continuous fanning or circulation of the air by the displacer), well, maybe, just maybe, the ice used to run an LTD engine would stay cold longer, but I would think, for that to happen, the engine would have to be causing some cooling by some means or other.

Spoiler alert!

https://www.physicsforums.com/threads/s ... ne.991714/

In this case though, with a high temperature thermal lag (or whatever) type engine, there is no displacer to either insulate or "fan" with hot air, the power cylinder area.

What theory would we be testing?

I think it would be worth doing, and could be interesting, but I don't think the results would be as clear cut as with the LTD running or not running on ice.

If the power piston chamber heats up in the not-running engine, is that due to conduction or convection? Would any hot air move into the power cylinder at all?

Of course, if the power cylinder actually cooled down to some sub-ambient temperature, (with the engine running) that would be pretty extraordinary.

[VincentG]

Conduction of heat alone in a stationary engine would eventually heat up the expansion side to "X" temperature, while running the engine would eventually reach "Y" temperature.

While I do think the running of the engine can provide cooling, that would be an important variable in the test.

[Jack]

Well if you're thinking of turning that drawing into a rotary design you'll have to run a rotor inside a rotor.

Well,...

That might be possible.

There was a patent or patent application for a two stage duel rotary vane compressor

Patent-of-a-two-stage-dual-vane-compressor-3.png

But what I had in mind was not that, but similar in that the vanes would be "shared" and the vanes would travel in a grove, but what I drew would look like a break rotor with the vane guide a disk in the center of a stationary rotor, rather than a circle, and with the vanes sliding from side to side rather than in and out from center.

Similar to a cylindrical or barrel cam:

zylindernutkurve1.gif

Imagine my drawing wrapped around a cylinder similar to the above gif but the vanes traveling in the grove and cylinder stationary.


duel-vane-engine.jpg

That patent is a nice idea, but mechanically very difficult to do. Volumes of the chambers would be different to each other, vanes wear and don't seal anymore, not to mention trying to just get it to work with bearing placement. I'm struggling with this exact problem at the moment.

The barrel idea has similar mechanical issues. Sealing being the most difficult one as you just introduced more sealing surfaces. And probably the barrel will still have to be the turning part, to get the work onto an axle to be useable.
But it might be that I'm just missing something.
I saw you mention in another thread somewhere how scientist are blind to new ways. It's a human problem in general, one that I suffer from as well. Once you turn in one direction it's very difficult to see the other direction.

[Tom Booth]

...
The barrel idea has similar mechanical issues. Sealing being the most difficult ...

Yes, I get the impression that is a problem with rotary vane devices generally. I have some virtually new, hardly ever used air tools that I found were rotary vane, and basically the air goes straight through until they get up to speed and the centrifugal force starts to create a positive seal.

My side winder rotor would not be able to take advantage of centrifugal force so the sidewall tolerances would have to be, quite likely, impossibly close and non-contact, no friction, like a NASA Stirling. But those things run for decades with no wear but that's probably not possible to achieve with a rotary vane design.

Still, my 2001 Ford Ranger pickup truck IC engine likely has many more high friction, high wear parts but still runs great after more than 20 years.

[Jack]

Another thing I later realised is that the barrel idea creates force in the length of the axle, which has to be translated to across the axle. That always creates more friction and loss.

I found the whole patent you were talking about and it seems they talk about a second version that's very promising. I'm exploring that further.

[Tom Booth]

The design I drew was literally off the top of my head so who knows if it's even possible. According to classical thermodynamics, no.

Well, actually I'm not sure about that. From what I understand the Carnot limit is supposed to apply to reciprocating engines where the piston needs to reverse course and return to TDC.

Now I'm wondering if there could be ports open to atmosphere, making it functionally an "atmospheric engine" similar to a flame licker, but with ports rather than a valve.

Another thought regarding friction. The ferrofluid seal came to mind.

The idea of a Ferrofluid piston seal was floated in here a while back

viewtopic.php?f=1&t=5477&p=18034

and I had plans to experiment with that, but the bottle of Ferrofluid is still sitting on the shelf in my shop so far, But I noticed now that Ferrofluid "o-rings" are actually being used industrially already and there are companies currently fashioning "custom" Ferrofluid seals for various applications. I couldn't locate anything involving Ferrofluid in a rotary vane type application, but for a closed cycle, hermetically sealed engine, that seems quite feasible, the stuff cannot go anywhere.

Magnetized vanes "lubricated" with Ferrofluid, or vanes with a magnetic strip along the edges.

Ferrofluid used in Stirling engines, a few videos:

https://youtu.be/21WzdjqAG0s?si=3Ymw8goaJHKeKsj4

https://youtu.be/3Uh0pBJ5QW0?si=8AdXY17cOlPDhF2n

[Tom Booth]

That gives me another idea.

I've been struggling for, seems like years, to come up with a good design for an "adjustable" air spring.

What kind of tensioner to use? How to make it work over various levels of pressurization? How to keep the air-spring piston positioned and centered?

Magnets and Ferrofluid!

Something like this:

Resize_20231209_133833_3821.jpg (160.56 KiB) Viewed 10929 times

The hair thin passage through the center of the piston is for pressure equalization.

The half round objects are the magnets embedded in the piston and cylinder walls that hold the ferrofluid in place creating a perfect frictionless seal and also keep the piston properly positioned regardless of the level of pressurization.