Tesla's "Ambient Heat Engine" Experiment

[Tom Booth]

After 12 hours, still running as I get up this morning.

I thought the heavy condensation in line with the flywheel was worth making a recording of.

https://youtu.be/-7zntz8kwIk

Going to bed last night I shut off the fan in the kitchen, so there was very little air movement all night, except where it was being disturbed by the flywheel.

I'm thinking to add fins to the flywheel to increase air circulation. But I'm not going to halt the experiment for that. Next time.

As seen in the video, I left the insulation off the top when I gave up waiting for the engine to stop and went to bed.

I did not want to take a chance that the engine would not have enough heat and stop running prematurely while I slept.

[Yorky]

I am following this with interest.

After 12 hours run time, did you note the condition of the Ice, frozen /part melted

[Sockmonkey]

12 hours of run time really emphasizes the sheer efficiency of the Stirling.

[Tom Booth]

I am following this with interest.

After 12 hours run time, did you note the condition of the Ice, frozen /part melted

I didn't want to introduce heat under the engine any more than necessary.

After 31 hours, when the engine seemed to be slowing down a little I checked and nearly all the ice had melted by that time.

I closed it back up and the engine continued running for two more hours. After that it would no longer start and the ice was completely melted. The engine probably continued running for a while on just cold water.

I repeated the experiment but without running the engine, just letting the engine sit on the cup of ice but not starting it.

The ice melted in 28 hours.

Apparently the engine, while running on ice, managed in some way to prevent the ice from melting as fast as with the engine not running.

That is a five hour difference.

Also, the conditions for the second part of the experiment, with the engine not running, were IMO probably favorable to the ice lasting longer.

The heat wave was ending and ambient temperatures were a little cooler by then.

I had added additional insulation durring the running phase. The ice had the advantage of that extra insulation from the start during the second phase.

If anything the results were probably skewed so that the difference in melting time probably would have been more if all conditions were absolutely identical.

But, I'm not drawing any hard conclusions until the results are shown to be repeatable.
.

[Tom Booth]

I had suspected that the ice would last longer while being used to run a Stirling engine, but there were some surprises.

During the "control"; leaving the engine on ice without running it; after just 10 hours, the engine had become so thoroughly cold that it refused to run at all.

I did, previous to making the video, have the engine covered with additional insulation. I did this with the running engine also but the running engine did not stop running with the insulation on top. I assume that was due to friction in the cylinder etc. adding some heat to the top of the engine. The flywheel contributing to air flow, etc.

Not running, under the insulation, the idle engine completely lost its temperature differential and would not run.

https://youtu.be/41d6kIHLK7M

So after that I left the insulation on top of the engine off for a few hours, then when I tried to see if the engine would start, something else strange happened:

https://youtu.be/fnxC8hymFLU

Apparently the evaporation of condensation that had accumulated on the cylinder caused cooling of the cylinder, (which was already thoroughly cold, near freezing, from sitting on ice without running.)

The piston froze up in the cylinder!

Froze up with ice, from evaporative cooling! At least that is how it seemed, unless someone has some alternative explanations.

[Tom Booth]

This video shows the degree of melting of the ice after 32 hours.

https://youtu.be/lFhUkzHRbWo

By that time I put part of an old aluminum appliance outlet on the engine to draw more heat down. The engine ran for another hour after that.

I still have three more kits. I think all that I ordered finally came. When I get two identical engines put together I want to run (and not run) the engines on ice concurrently just to eliminate any variables I couldn't control in a consecutive run, like varying weather conditions, humidity, time of day, etc.

Aside from using plastic bolts to cut down on heat transfer through the engine bolts, I want to make additional modifications to try to increase the run time.

These are not really proper Stirling engines with regenerators. I think adding heat regeneration would increase run time considerably.

I also, now that I know about it, want to try and do something with the rather copious water condensation.

Somehow collect the condensing water and utilize it for evaporative cooling.

As it is, water condenses and just stays on top and evaporates. The heat of condensation and of evaporation just cancel each other.

If water condensation can be allowed to run off as it accumulates, it could drip down to the lower cold plate on top of the ice. Then if it evaporates, the cooling effect will do some good, refrigerating the ice instead of the piston and cylinder.

That could probably be accomplished by making the top plate of the engine dome shaped on the upper side so that water condensation can run off and down to some collection tray surrounding the underside of the engine.

If it can freeze the piston, perhaps it can help make the ice last longer.

It seems, if it could be utilized in some way, evaporating water can draw off ten times more heat than the refrigerants used in the evaporator of a household refrigerator or heat pump.

[Tom Booth]

This chart includes many of the common household refrigerants:

https://www.engineeringtoolbox.com/amp/ ... d_147.html

Down at the bottom of the chart is water at 970 btu's/lb.

As I understand it, the same number also represents the amount of heat released during condensation. But without some re-design of the engine, all that potential energy is just canceling itself out by condensing and evaporating at the same time, on the same side of the engine.

I guess there are reasons water is not more often used as a refrigerant. It generally evaporates well above the target temperature for a refrigerator or freezer, but for harnessing the energy of ambient heat, it quit possibly could work just fine.

Until now, if anything, I had always looked at water condensation as a nuisance issue that could cause problems for this Tesla ambient heat engine theory.

Water in a very cold running engine would freeze and block pipes and such, and would have to be taken out. Tesla was trying to go for cryogenic cold temperatures. That would require "dry" air, even CO2 (dry ice) is a problem at such cold temperatures.

[Tom Booth]

I have a plan for additional simple modifications for one of these Stirling engine kits.

1. I may add some plumbing Teflon tape at the seals. Teflon is not only good as a sealant, but it is also a heat barrier.

Teflon tape

IMG_20200729_081316112_crop_40_resize_48.jpg (50.64 KiB) Viewed 12833 times

2. Add Regenerator

I was planning on putting holes through the thin styrofoam for ports where steel wool could be stuffed in, but having tried this method previously I found that it presents several difficulties.

It causes irreversible damage to the displacer. The steel wool is difficult to keep in place without some kind of retaining screens, which adds to the weight and bulk. The steel wool has to be packed in tight, or it will come loose and fall out, whereas it really needs to be light and thin for good air flow and to be effective as a Regenerator.

So I came up with a less damaging method for adding a regenerator that would attach the steel wool securely with little added weight, and that could also be removed and replaced if necessary, while leaving the original displacer intact.

The double sided tape used for sticking plastic window insulation on windows in the winter is extremely thin.

The displacer that came with the engine really has excess clearance, so there is room to simply use this window tape to stick some wisps of fine steel wool around the perimeter of the displacer, which is the "port" through which the air is already moving.

Along with the other modifications already described and implemented previously: nylon instead of steel bolts, added insulation and so forth, I think we may see some very surprising results.

If the engine already runs faster and longer, apparently, without transferring much, if any heat to the sink, (see the end of the Stirling engine thermodynamics thread), what might be the result after these additional modifications?

I have an idea, but the proof of the pudding is in the eating as they say.

[Tom Booth]

Oh, and one additional possible modification.

Taking the laminar flow Stirling idea, where, theoretically, the narrow port or washer results in a high velocity jet intended to impact the piston with a little more force and also reduce heat input into the cylinder while not compromising power, by converting pressure into velocity. Lots of "what ifs" but a reduction in the size of the piston port opening could also be done in such a way that the "washer" or whatever is used can be added and removed or modified without making changes to the original structure of the engine.

[Bumpkin]

Tom Booth said: "I guess there are reasons water is not more often used as a refrigerant. It generally evaporates well above the target temperature for a refrigerator or freezer, but for harnessing the energy of ambient heat, it quit possibly could work just fine."

There was This thread:
viewtopic.php?f=1&t=1133&hilit=Barton+engine
It was just talk and I never looked further into it, but I can't see why it wouldn't be possible. And for the nay-sayers, no it's not "free energy" any more than solar panels or windmills.
Bumpkin

[Tom Booth]

Tom Booth said: "I guess there are reasons water is not more often used as a refrigerant. It generally evaporates well above the target temperature for a refrigerator or freezer, but for harnessing the energy of ambient heat, it quit possibly could work just fine."

There was This thread:
viewtopic.php?f=1&t=1133&hilit=Barton+engine
It was just talk and I never looked further into it, but I can't see why it wouldn't be possible. And for the nay-sayers, no it's not "free energy" any more than solar panels or windmills.
Bumpkin

It might work, but, yeah, it has solar or whatever heat input, so, it needs "fuel" or a heat source to boil the water, and overall, seems a cumbersome way to utilize steam.

But what about something like a diesel engine, fire piston, that uses the "heat of compression" to make the steam?

If it were "open cycle" taking in fresh air with each gulp, that's already solar heated air.

I'd be interested to see what would actually happen if someone just put a drop of water in the bottom of one of these fire pistons and gave it a slam.

https://youtu.be/-39wmSBO2FM

I was reading a patent where something similar to a fire piston was used to transfer the heat of compression to a Regenerator matrix of some kind where the heat was retained or conducted away for use elsewhere, so maybe where you mentioned the "flash point" problem:

You can't steam water by injecting it into compression-heated air, because the pressure also raises the flash point.

Could that be avoided somehow with multiple cylinders?

[Bumpkin]

"Could that be avoided somehow with multiple cylinders?"
When I was a kid I found it incredible that I was the only one smart enough to see that if you would inject water instead of diesel you'd have a lot cheaper fuel. My dad finally got my head pounded straight, but when I was twelve we took a trip that went through Yellowstone Park and did the usual tourist thing, watching "Old Faithful." It got me to thinking about the working principle of geysers and how it could apply to an ambient-heat engine. That concept eventually discarded steam and simplified to resemble a basic thermal lag engine. I made a few models that didn't do anything but waste time, but considering my modeling skill, that doesn't prove or disprove anything.
Bumpkin

[Tom Booth]

That's the wonderful thing about childhood. A child's vision is clear, they haven't yet had blinders strapped on by "education".

I think the comparison of the geyser with a thermal lag engine is good food for thought.

Still a kid at heart I see. Wonderful.

I'd love to work on building some such water fueled engine.

In a way, I would say it takes advantage of phase change, which was the general theme of the Leidenfrost heat engine thread. viewtopic.php?f=1&t=2667

I'm still anxious to try a little butane in an LTD Stirling running on ice.

I still have a soda bottle in the freezer with a bit of liquid butane condensed in the bottom, and I marvel at how rapidly the bottle expands the second I take it out of the freezer. The fluid vaporizes and disappears rapidly.

Apparently butane is not so difficult to contain with the right material It has remained trapped in the soda bottle for weeks now.

I figure phase change is phase change regardless of the fluid used or it's boiling point.

Thanks for the wonderful story from your childhood, I love it!

I made a few models...

Do you still have these models? Or drawings or anything?

[Bumpkin]

For some reason the geyser got me wondering if you could compress air, draw the heat off for steam elsewhere, then recover power expanding the air, which would then be colder and would reheat from the ambient or simply be exhausted. Expanding couldn't get back all of the power used in compressing, since the cooled air would be lower pressure, but the heat gained at the other end would balance the loss. So in a theoretical perfectly efficient friction-free steam engine it still hasn't accomplished anything but move energy around - but it demonstrates the concept of a heat engine producing it's own cold side and drawing energy from ambient temperature. It's not in any way similar to perpetual motion schemes because external energy is used. I'm sure there's nothing original in the notion of making a "cold hole" to harvest energy and it probably predates Tesla back to the first understanding of air engines,

I haven't pursued an ambient engine since taking on family obligations over twenty years ago, and the last model eventually went to scrap. Since then I discovered how much it resembled certain thermal lag engines and decided I was probably on the wrong track anyway. I'm not likely to get back to it, but I still believe it does not violate thermodynamic "laws" to use only ambient heat to produce power. The Barton engine comes close, but its principle of producing power by cooling air relies on humidifying it, so the ambient supply is limited to a finite weather range and also needs a water supply.. Here's an example of the same humidifying principle applied in an entirely different way:

https://www.popularmechanics.com/scienc ... on-engine/

Bumpkin

[Tom Booth]

After doing this experiment:

https://youtu.be/fFByKkGr5bE

I thought, well, a few things. If the engine ran better with some insulation on top, would it run better yet with even more?

But there isn't much room, but what if I replaced the aluminum cold plate with plexiglass?

Also, maybe the aluminum was also sinking heat because it is such a tiny engine and uses so little heat, perhaps the aluminum itself was enough of a sink even insulated. That's speculation on the science forum anyway.

https://www.scienceforums.net/topic/122 ... /#comments

So, I just finished cutting out this plexiglass top:

IMG_20200803_164342250_crop_96_resize_85.jpg (45.53 KiB) Viewed 12738 times

We'll see how it goes. Any predictions?

Thermal conductivity of aluminum is 237

Thermal conductivity of plexiglass (acrylic) 0.17

https://en.m.wikipedia.org/wiki/List_of ... uctivities

More than 1000x less conductive.