Tesla's Ambient Heat Engine revisted

[Tom Booth]

"Pretty obviously the elevated heat signature appearing around the power piston could only be from "work"."

Why is that?
Could the heat not come from the working fluid?

Well, maybe. How?

It's the cold side of the engine. The top of the engine in contact with the working fluid is 64 or 65°F

The power cylinder is an "island" near the middle, within this cool zone above the displacer and appears to be about 10° warmer.

Within the power cylinder is a piston moving up and down generating friction, driven by the expansion (work) of the working fluid.

The pretty obvious source of heat centered on the power piston is friction. If anything the heat generated by friction is migrating back into the cooler working fluid not coming out of it and somehow gathering around the power piston.

Heat moves, generally speaking, from hot to cold not the other way around. The power cylinder is hot surrounded by the cooler zone above the displacer.

There is some localized compression of gas in the cylinder I suppose, but that would also be the result of mechanical "work". Not likely a factor IMO.

The heat of friction and/or compression comes from the WORK done by the working fluid, sure.

I assume however you are talking about direct heat transfer from the presumably cool gas to the heat laden cylinder.

You seem to think heat can spontaneously gather in one spot, moving from cold to hot.

[Tom Booth]

One thing I haven't tried yet, I don't think, is running one of the modified LTD engines with a retrofit regenerator on ice/ambient heat.

Well, I did once and the engine froze up, or something.

Anyway, a slight modification of the drawing I posted earlier in the thread:

Compress_20240507_135720_0200.jpg (34.64 KiB) Viewed 2680 times

Now the regenerator can sequester heat at a greater ∆T

A properly constructed (layered) regenerator can return something like 95% of the heat.

In other words, you get the benefit of extra cooling with ice, increasing the temperature difference but without actually dumping heat into the ice, only into the regenerator where it can be recovered.

[VincentG]

Moving this discussion from the Essex thread, I do see the potential of a regenerator.
Let's say the regenerator is contained in a separate circuit outside the engine. Then if the regenerator is active(gas flowing through) only when the displacer is moving, and is isolated from the rest of the system with two valves during the majority of compression and expansion, I can see a great benefit to power and efficiency.

Maybe I can try this with my 60l drum engine. I'm pretty tired of messing with tiny engines lol.

[Fool]

hopefully others will verify the results with their own independent research.

I'm not looking for a "following".

Following your experiments to verify them, is different from a following. But you knew that anyway, and thought the statement sounded cool, misleading, but cool.

What I'm still trying to fathom is why your temperature IR camera, appears to have little experimental control. No known temperatures to read, ice, boiling. The hot water temperature helps, but is still an unknown. Furthermore, no data for what temperature the engine was before being introduced to hot water. Hmmm

Source Tom Booth

Resize_20230522_031849_9086.jpg (175.66 KiB) Viewed 2661 times

Screenshot_20211119-102348.jpg (48.32 KiB) Viewed 2661 times

For a real cycle to "cool" a cold plate, wouldn't the indicator diagram need to go below the isothermal line that is the room's temperature, for a significant length of time. Clearly not in any provided real indicator diagrams. Where is your indicator graph of your test showing that? Inconclusive tests lack extraordinary evidence. You have skipped to the extraordinary claims, with only so so data. We are questioning your science. Where is your mathematics predicting how much cooling (Joules) and temperature drop (Kelvin) to expect? An observation is only as good as it's math.

[Tom Booth]

...

What I'm still trying to fathom is why your temperature IR camera, appears to have little experimental control. No known temperatures to read, ice, boiling.
...

The camera was factory calibrated. I did tests when I got it. It seemed to read OK using ice, boiling water etc.

For relative temperatures, hotter, colder, the same, exact temperature readings are not all that significant anyway IMO

Compress_20240504_125427_7507.jpg (22.73 KiB) Viewed 2653 times

In this image, would it make a difference if all the readings were a few degrees higher or lower?

Why don't you address the actual significance of the power piston reading being 10° higher, relatively speaking, than the cold side temperature? Or that the cold side temperature never increases after running the engine on hot water for three hours?

Anyway, your criticisms are appreciated. I'll try to make improvements in my presentations going forward. Thanks.

[VincentG]

I'm still confused Tom. Why would the power piston NOT be warmer? Hot gas is expanding into it..

[Fool]

Your power piston cylinder appears at a higher temperature than the top of the cold plate. I can only guess why from the information recorded. Work is certainly a factor to consider. What it read before running wasn't given to me.

I would expect the top of the cold plate to not be changing temperature after three hours of running, unless recently disturbed. There may or may not be a temperature change in the top of the cold plate in the first few minutes after introducing hot water and starting it running.

The purpose of the cold plate is to have a temperature identical to ambient. Heat coming out should make it slightly higher. I don't have an answer as to why it appears not to be higher. I can only guess. You have eliminated some of my guesses already. So I'm running low on guesses.

If you have a valid experiment, and have found something unusual, you are in the 1800's wooden ship scurvy alleged cure from oranges stage. Yohan ate oranges on the last trip and was the only one that didn't get scurvy. Tom is the only person that has run a Stirling Engine with the cold side insulated, and he claims it runs faster and colder. Now we need to correlate it with numbers predicting it. I have no idea how to do that, except starting with an indicator diagram.

If I come up with a workable prediction, not likely, I will share it with you. We would probably earn a Nobel. Unless we find some other reason for it and disprove it. Then we'll just get a bunch of I told you so's. I guess I'm in the trying to disprove phase, "falsifiability". I need to retest it myself, not likely either, I still haven't built the engine I want to build from 20+ years of research, study, and pondering. Maybe this summer or fall.

I found it interesting when you peeled down the insulation and pointed at the side. Unfortunately you waved it around too much, but briefly I thought I saw hot on one side of the displacer and cold on the other, going up and down. The "chain regenerator" blocked the view too. Stable readings from that vantage point, maybe in slow or stop motion, would be fun to look at.

[Fool]

VincentG, the power piston is on the cold, plate and side. There shouldn't be any hot gas there. Right? The main things increasing the gas temperature there would be compression from the reverse stroke, and heat from friction, and atmosphere, if warmer maybe.

[VincentG]

VincentG, the power piston is on the cold, plate and side. There shouldn't be any hot gas there. Right?

I don't agree. The displacer is agitating the gas and imo the ideal model of just high pressure cold gas powering the piston is not what actually occurs.

The piston is increasing volume and I'd bet hot gas molecules are eager to fill the void.

[Fool]

That is possible. They would have a fairly long distance to travel through the cold space. They Appear to be only a few degrees warmer.

[Tom Booth]

I'm still confused Tom. Why would the power piston NOT be warmer? Hot gas is expanding into it..

Not sure how you figure "hot" gas is expanding into the power piston.

The cold gas, for the most part, is heated and expanded below the displacer as the displacer raises up and drives cold air down to be heated.

Aside from that, we can generally say the gas does not actually heat up that much, it expands as it takes in energy.

Expanding gas also tends to cool down as it expands.

At any rate, the hot gas rising up from the bottom, if we assume it does, would have to pass through the upper cold side of the displacer chamber warming the cold plate before it reached the power cylinder.

How do you figure the hot air can skip past the upper cold zone and stuff itself up into the power cylinder without first, or also transferring heat to the upper cold plate it would have to get past first?

Anyway, I just sent for a pack of new thermocouple probes.

Cheap, general purpose. Limited temperature range but I don't have the budget for the more expensive ones that work up to 2000°F

Compress_20240508_123223_3993.jpg (42.17 KiB) Viewed 2641 times

Should be fine for taking readings from an LTD under most normal operating conditions.

I also picked up a new toy from Harbor Freight while I was there the other day buying sandpaper for a woodworking project.

Compress_20240508_123730_0577.jpg (29.81 KiB) Viewed 2641 times

These tachometers are a lot less expensive than I had imagined or I would have picked one up a long time ago.

Now that I look, heck, this thing is expensive! I could have gotten a similar tachometer on eBay for under $10

Oh well.

[Tom Booth]

Maybe the engines I'm getting with the isolated pp will help to resolve the issue of how the pp is heating up?

Compress_20240505_221454_4707.jpg (16.32 KiB) Viewed 2639 times

Can the hot gas travel all the way up that metal stem without loosing heat along the way?

Also if the pp heats up while the engine is running on ice?

[Tom Booth]

In the video where I pull back the insulation, the IR image and readings seem to indicate a clear division between the hot regenerator (87°F) and cold top plate (62°F)

Compress_20240508_133713_3920.jpg (16.93 KiB) Viewed 2632 times

The power cylinder is also near the forefront of the image, but this was the first video taken within the first hour so the pp has not had time to heat up yet, whatever the cause might have been.

The graphite piston is very low friction so would take time for heat to build up that way.

[VincentG]

Not sure how you figure "hot" gas is expanding into the power piston.

The cold gas, for the most part, is heated and expanded below the displacer as the displacer raises up and drives cold air down to be heated.

Aside from that, we can generally say the gas does not actually heat up that much, it expands as it takes in energy.

Expanding gas also tends to cool down as it expands.

At any rate, the hot gas rising up from the bottom, if we assume it does, would have to pass through the upper cold side of the displacer chamber warming the cold plate before it reached the power cylinder.

How do you figure the hot air can skip past the upper cold zone and stuff itself up into the power cylinder without first, or also transferring heat to the upper cold plate it would have to get past first?

I don't literally mean "hot". The "hot" gas is trying to expand into the piston but is cooled by the displacer and cold side and cylinder, etc. In a standard engine it's probably warm gas by the time it gets there.

It's not like these little engines have valves and camshafts to isolate distinct events.

It's just one wishy-washy sequence in essentially an open chamber. The gas is free to move around. Even with the displacer fully raised, convection causes the cold gas to sink and be replaced by hot gas, which in turn is cooled, and again sinks.

It's the same thing that causes a free piston to move proportionally to the displacer position.

[VincentG]

Over the years, I've often heard of Tesla's ambient heat engine (cold hole) and blown it off as just another one of his wacky schemes (he had many). However, a recent post made me reconsider the possibility.

Which post, Matt?