Tesla's "Ambient Heat Engine" Experiment

[Tom Booth]

The one way to see if it actually works is to build it, and try it out.
Ian S C

Very True.

I like the engine you posted earlier:



I was wondering what it cost to build. Including time, material and any necessary workshop equipment etc.

[Ian S C]

Tom, that one cost me the price of the 12 nylon screws used to hold the top and bottom plates together. The plates were made from 2 frying pans found in a rubbish skip, the top one is 5 mm thick, and the bottom one 3 mm. The flywheel was made from the pan used for the top plate, the spokes are bits of old bike spokes. The power piston is 1" diameter, and made of cast iron as is the cylinder. The displacer is a foam plastic disc, and the displacer cylinder is a bit of plastic drain pipe. My usual motors are high temp ones, and I make them to see how much power I can get out of them.

To get power out of any type of machine you must put in that amount of power plus enough to cover inefficiency, you can't get anything from nothing.
Ian S C

[Tom Booth]

I can't imagine turning some old frying pans into a Stirling Engine without some kind of machine shop.

[Ian S C]

If you are going to get serious about building hot air motors (or any motor, or model) you need at least the use of a lathe, unless you are only going to build tin can motors. The most important thing is imagination.

Ian S C

[Tom Booth]

For anyone who might be interested, I have found myself with a few weeks of free time, so I have been working on building, or trying to build the combined Stirling engine / Vuilleumier heat pump, or Tesla "self acting" heat engine described earlier.

It is intended as a "Stirling Engine" with a second regenerative displacer that should function as a heat pump, or Stirling cooler.

I know, according to the traditional interpretation of the second law of thermodynamics, a "Self Acting Engine" operating on the heat from a single uniform "reservoir" of heat, or put another way, heat from the ambient environment, is "impossible", but I'm not so sure.

Tesla believed it could be done, but before he could finish work on it, someone burned down his workshop.

I think I understand what it was Tesla was trying to do, and to my knowledge, it has never been tried, if anyone ever understood what it was he was doing.

Anyway, I'll be working on it over the next few weeks. Right now, I have the two displacers glued and clamped to attach the connecting rods.

[Tom Booth]

Interestingly, after I started working on this around Christmas, the design based on a cookie tin, I came across this video where someone built a Stirling using the same cookie tin.

He is supplying a lot of heat from a gas stove to run the thing though. Getting a similar engine to run on ice and ambient heat will no doubt be a challenge, if not an impossibuility.

https://youtu.be/ViqQ1YXCpHY

[Tom Booth]

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Well, I got something put together finally

IMG_20200115_113045571_resize_2.jpg (108.1 KiB) Viewed 18774 times

Haven't. Been able to get it to run though. Not even with bags full of scalding hot water from the tea kettle on top and ice below.

I've exhausted all the simple possibilities as far as what might be wrong. Simple as far as things I can check and fix, friction, air leaks, timming adjustments.

It shows virtually no sign whatsoever of any internal pressure changes when cranked by hand, even with ice and boiling water.

It has a diaphragm piston made from a latex gloves.

With the connecting rod disconnected, cranked by hand, the diaphragm doesn't expand or move or do anything. Even with ice and boiling water, cranking with a power drill attached to the crank.

I'm baffled, how that is even possible? I've never had an engine that did not at least TRY to move the piston or diaphragm a little, no matter how crudely slapped together. A plastic bottle with a balloon warmed by a hand shows more action.

I'm actually rather fascinated by this result. Or utter lack of result.

The top of the engine did, almost immediately, get very cold, when I first tried to get it going, sitting on ice. But the ice showed no evidence of .melting.

Even after cranking by hand for 20 minutes or so, with near boiling water on top, the ice did not show any melting..

So I'm thinking maybe it was acting as a heat pump, keeping the ice cold, but I don't know. A VM heat pump works by pressure variations. This shows no real dissernable pressure differentials. Even with ice and boiling water.

I'm somewhat mystified.

[Tom Booth]

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No, the displacers did not fall off.

[Tom Booth]

This first attempt is far from ideal in just about every way possible, but it was cheap and easy to put together. No parts needed machining anyway.

The engine body conducts too much heat. The floppy styrofoam displacers were too thin, and, well, floppy.

The connecting rods were too flexible, bendy and soft and tended to kink and bind.

Yet, while cranking the engine by hand, if I looked very very closely, I thought I saw the diaphragm rising and falling, just a little. The movement was so slight, it could possibly be my imagination, vibration, the engine shaking slightly.

I know that isn't much, but I don't feel I can really rule out this idea working without giving it a fair trial. The temperature difference between ice and boiling water is not really great in the realm of heat engines typically running on a flame at some 1000 degrees or whatever.

What makes me want to go to the trouble of building a better model is, the rise and fall of the diaphragm was in time. That is, it expanded at the right time, at the power stroke and contracted when it was supposed to at the return phase. The movement was so slight, though, it was barely noticeable.

Anyway, people often fail in a first attempt at building a working engine and this thing is unusual, and perhaps impossible. So I'm not throwing in the towel just yet, though it looks like the second law of thermodynamics has won the first round.

[Tom Booth]

I picked up some supplies today in order to have another go at it.

I found a nice clear plastic canister/lazy Susan sort of thing for the engine body. The plastic should not conduct so much heat away, before it has a chance to do anything. I found some more rigid displacer body material that should hold up and do its job better, and some stainless steel telescoping campfire forks for displacer connecting rods.

I think these items should make for some potential improvements in this "do nothing" engine. If it is ever going to be capable of doing anything.

Any well built LTD Stirling should be able to run between ice and boiling water.

The last one, though far from well built, might actually have tried to do something, if I wasn't imagining things.

A plastic canister that doesn't conduct away heat, connecting rods that don't bend and bind or leak air. More rigid displacers. Should, in theory, resolve some obvious issues.

I also picked up some aluminum plate from the machine shop for the heat exchangers and some Teflon, or some kind of plastic bolts to hold it together, so there really won't be anything to conduct much heat away other than the air in the chamber. As it should be.

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[Tom Booth]

Just a brief update. Progress on the engine has been slow, and completely stalled, with the world gone mad as of late, but as things appear to be gradually returning to some semblance of normalcy, my plans are to spend more time on this experiment.

The rigid foam displacers have been shaped to fit, along with the heat exchanger plates. Much more to go on this, but for those interested, I wanted to make it known I haven't abandoned the project.

[Tom Booth]

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It's been years since I proposed this experiment. Finally, I'm getting around to it. Or, I should say, I feel it is worth the investment and I'm in a position to afford spending the time and money.

I found this relatively inexpensive commercial LTD engine that advertises it can run on ice.

https://www.ecrater.com/p/32908969/stir ... gIwoPD_BwE

So I'm ordering two.

Ideally, I'd probably do better with the more expensive and well made kontix:

https://www.stirlingengine.co.uk/d.asp? ... gecurrency

But, at a cost of about $450 for a pair, I'll give the less expensive option a try to begin with.

This is not any effort to run a "Self-Acting Engine" exactly, but just a test to see if there is anything to the theory that; because a running heat engine is actively converting heat into some other form of energy, a running engine should transfer LESS heat than an idle engine.

I believe, in the case of a steam engine, Steam does come out of the engine much cooler than it went in. Cooler than the direct steam out of the boiler, because, the heat has been converted into work in driving the engine and its attached load. So, why should this principle not also hold true for a Stirling engine running on ambient heat rather than steam?

The ambient heat drives the Stirling engine running on ice, so logically(?), as air inside the engine is transferred to the cold side, the temperature of the air should be closer to the temperature of the ice, having lost some heat, which has been converted to work. As illustrated in this diagram:

heatengine.gif (4.42 KiB) Viewed 11135 times

http://labman.phys.utk.edu/phys221core/ ... gines.html

Does this actually make sense though?

[Tom Booth]

Dewar flasks, like these can be rather expensive:

https://www.tequipment.net/Scilogex/SS1 ... ?rrec=true

But for the purposes of this experiment, some of these stainless, double walled, vacuum insulated mugs should do (under $10 at Walmart):

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If it can keep a drink cold for 18 hours, what about a solid block of ice? Should be fine for comparison purposes.

[Sockmonkey]

You get work out of heat by giving it somewhere to go and making it do something for you in order to get there. You can compare it to a water wheel in that way. It's usually easiest to make a hot spot and use the environment as the cool place the heat tries to flow through. Lower pressure also counts as "colder" in that the heat can now occupy more volume.

[Tom Booth]

You get work out of heat by giving it somewhere to go and making it do something for you in order to get there. You can compare it to a water wheel in that way. It's usually easiest to make a hot spot and use the environment as the cool place the heat tries to flow through. Lower pressure also counts as "colder" in that the heat can now occupy more volume.

That certainly does represent the conventional wisdom.

Tesla, though, was not exactly conventional. He was certainly familiar with what everybody knew about heat engines, the second law of thermodynamics and all that, but he had a different idea about how heat engines work, and to my knowledge, his ideas have never been adequately put to the test. As for Tesla, he wrote: "a misfortune befell me in the burning of my laboratory, which crippled my labors", but I think he left behind enough information to move things forward today, if his theory was correct.

More than anything, I would say; heat in a heat engine is like the kinetic energy of billiard balls on a pool table:

Translational_motion.gif (398 KiB) Viewed 11115 times

The idea is not so much giving these hot molecules somewhere to go but rather giving them something that they can hit and move.

If a ball strikes a solid immovable object it bounces off retaining its kinetic energy. But if it hits something that can move, the energy is transferred to the other object. In the case of a heat engine, the moveable object is the piston. The "heat" or kinetic energy, transferred to the piston, does not need anywhere else to go.

Tesla wrote in that regard: "But let us reflect a moment. Heat, though following certain general laws of mechanics, like a fluid, is not such; it is energy which may be converted into other forms of energy ... If the process of heat-transformation (in a heat engine) were absolutely perfect, no heat at all would arrive at the low level (or heat sink), since all of it would be converted into other forms of energy."

Think of the piston being hit by little billiard balls on both sides. Heat the gas on one side and the kinetic energy of the air molecules increases, knocking the piston out, but as each molecule hits it loses its "internal energy" and gets "cold", stops moving, but other fast moving "hot" molecules continue to hit the piston, also loosing energy, until there is equalization of energy on both sides, but the piston, having momentum continues moving, and more molecules continue to strike it and loose energy, causing the gas in the engine to become even colder, again creating an imbalance, which allows molecules outside the engine to knock the piston back inward. It seems, ALL of the heat added to the gas in the engine has been lost, and then some! The heat does not flow through the engine, rather, now more heat must be added to repeat the cycle.

That was Tesla's basic argument, that heat is not REALLY a fluid, therefore it does not REALLY need a "sink" to flow into.

There does need to be an initial temperature difference though. Why? because there must be some way of adding heat in order to create an imbalance to start the piston moving, but once moving, the heat does not need to flow through the engine into the sink, so a Stirling engine running on ice does not add heat to the ice. Rather heat is added to the engine to push the piston as previously described. The heat is converted into the kinetic motion of the piston, which might be further transformed into electricity, if the engine is driving an electric generator. The heat has been transformed into a different form of energy, now more heat can be added to continue the cycle, but no heat has been transferred to the ice!

Your description is certainly familiar to me, and is the generally recognized and accepted way that Stirling engines are supposed to work. But I think that maybe Tesla was right, and everyone else, for the past 200 years has been wrong.