Stirlingengineforum.com

Thanks for the comments.

Personally I'm rather gobsmacked.

There is a perfectly good explanation for the observation IMO, I fact, it was at least in part produced intentionally based on largely accepted thermodynamic theories and mechanical principles.

Anyway, aside from that, keep in mind this engine was kept running for hours, replenishing the hot water with fresh hot water repeatedly. Logically, with a Carnot limit of about 20% efficiency, 80% or the heat entering the engine, according to that (Carnot limit) analysis , should be passing through to the presumed top cold heat rejection plate. I would think, with that amount of heat needing to be rejected each cycle, any margin of error in the instrument should be overwhelmed. That is, the heat rejection plate should be so much hotter than ambient that the difference in temperature should be greater than the presumed margin of error by far.

As far as materials, I've used acrylic, aluminum, aerogel, styrofoam, aluminum foil backed house insulation ceramic fiber cloth...

I'm aware of the potential variations in emissivity of different materials, but again, with all these variations in heat rejection side materials and/or insulation the engine(s) do not overheat, fail to run due to heat build up behind the insulation or show an elevation in temperature.

Basically I cannot, and see no reason to dismiss the observations offhand as being within the imagined "margin of error". Or the result of instrument failure or variations in emissivity/reflectivity

The "extraordinary claim" IMO is the Carnot limit assertion that leads to the conclusion that though 80% of the heat should be passing through the engine this "waste heat" is yet undetectable.

Regardless, thank you for your responses.

Nobody wrote: ↑Sat Jul 08, 2023 12:22 am . .. Very difficult to do accurate science.

That statement, IMO is preposterous. How is this difficult?

We are basically talking about using a thermometer to measure temperature. We don't doubt the thermometer reading when someone is sick and we take their temperature, or the reading of a thermometer when we are interested in the weather. Common thermometers are quite accurate and reliable. These kind of cop-out excuses I've heard over and over on the science and physics forums are utterly ridiculous, measuring heat is just too difficult. What a crock, no disrespect but IMO that is just silly.

Tom,

The little LTD's discussed here have very low power capabilities/production. It's quite possible the temperature change is too low to measure.

Really? The ∆T is what? About 130° on the fahrenheit scale. It only takes a fraction of that to run one of these engines. According to Carnot theory the rest of the heat should be passing through as "waste heat".

Somewhere recently you said that perhaps some engines heat up the cold side. Perhaps they are just the bigger engines. More power, more heat, higher temperature swing. Easier to measure.

Generally the heat heating up the cold side of a Stirling engine of whatever size is due to heat being CONDUCTED through the engine body in a topical metal Tin can type or other metal engine, not through the gas/working fluid.

That type of heat transfer is controllable and can be largely eliminated by material choices. Stainless steel is rather non conductive, acrylic is better but can't take much heat without melting which has mostly limited experiments to small model LTD's, but really, I don't see a lot of heat being conducted to the cold side even with a metal engine heated by a propane torch.

Certainly additional more varied and better controlled experiments should be conducted by more qualified university class or whatever researchers, but none seem interested. It would be a "waste of time".

These kind of experiments should be commonplace, a high school science experiment for students, dozens of demonstration videos on YouTube, but nothing.

Where, in the past 200 years is all the empirical evidence to validate the Carnot efficiency limit?

Doing accurate science is too difficult???

Instead I see videos like this, where the guy says, "I made provision for water cooling but surprisingly it wasn't needed... The engine can run for hours on end"

About the mid-point in the video.

https://youtu.be/QcppEhp2RfA

He attributes this to "vibrations" creating a continuous flow of air.

So, how about we block that imagined cooling air flow with an aerogel blanket?

No, now the aerogel has become a conductor increasing the surface area.!!!

Personally I find these kind of dismissive explanations laughable, if not actually tragic coming from seemingly rational, educated, scientific minded individuals.

It's the kind of rationalizations I would expect from a member of a religious cult.

The whole field of thermodynamics looks more and more like a cult of personality, of course, the same could be said for some advocates of Tesla.

What has happened to objective science?

Tom Booth wrote: ↑Sat Jul 08, 2023 6:42 am
Anyway, aside from that, keep in mind this engine was kept running for hours, replenishing the hot water with fresh hot water repeatedly. Logically, with a Carnot limit of about 20% efficiency, 80% or the heat entering the engine, according to that (Carnot limit) analysis , should be passing through to the presumed top cold heat rejection plate. I would think, with that amount of heat needing to be rejected each cycle, any margin of error in the instrument should be overwhelmed. That is, the heat rejection plate should be so much hotter than ambient that the difference in temperature should be greater than the presumed margin of error by far.

Here's the thing: there is very little heat entering the engine to begin with. Have you tried estimating the heat entering your engine?

Let's assume there is no losses through the side walls or bottom of your cup and that all the energy in the water will be transferred to the heater plate of your engine. The maximum amount of heat entering the engine can easily be calculated by basic calorimetry:

- known amount of water, i.e. its mass M
- water specific heat is known, Cp
- you know the start temperature, let's call that Ti
- you can decide at what temperature you want to stop the experiment, let's call that Tf
- of course time your experiment, measure Ti and Tf and the time it took to get to Tf

Once you have those numbers laid out, we can easily calculate the amount of heat entering your engine. I think you should do it if you haven't already.

It's been a while since I used an LTD but if you're not willing or if you don't have the tools to get those measurements, maybe I will.

Another quick test you can do:

Insulate your heat rejection plate (cooler) with some kind of foam.
If you are correct the engine will run the same way. But if engine the slows down and comes to a stop quicker than without the insulation, then you will know.

stephenz wrote: ↑Sat Jul 08, 2023 11:12 am Another quick test you can do:

Insulate your heat rejection plate (cooler) with some kind of foam.
If you are correct the engine will run the same way. But if engine the slows down and comes to a stop quicker than without the insulation, then you will know.

LOL.... Ha ha!!

Sorry, but I guess you haven't been following this series of experiments.

With foam insulation over the cooler/heat rejection plate the engine only ran faster!!!

That was years ago.

My "Insulating the sink" playlist on YouTube:

https://youtube.com/playlist?list=PLpx2 ... Q9pQZzY7Eu

As I mentioned above, I was told that the reason the engine runs faster with insulation is that the insulation in direct contact with the engine actually conducts heat away faster than air, which is a very poor conductor, so the only thing accomplished by covering the cold plate with foam is to increase the surface area.

In several experiments I used an engine with an acrylic top, which is nearly as poor a conductor as air, covered with an aerogel blanket and covered that with a glass dome to prevent drafts.

BTW, if you watch the first, latest video at the top of the playlist, please note that the first engine on the steam was pre-heated as the water came up to boil, while the insulated engine was stone cold and needed time to get up to operating temperature. Also the flywheel was rubbing on the insulation.

Another factor was, the two engines were not entirely identical.

The first had a metal bottom while the insulated engine had an acrylic/plastic bottom which restricted heat input.

The engine likely kept stopping in the begining of the video because it was not getting enough heat through the acrylic bottom plate, that is, it was starving from a lack of heat rather than getting too much heat.

I ordered the two engines from Amazon at the same time. I didn't notice the difference in the bottom plates until after the experiment.

Anyway, this was the first experiment I ever tried, not really knowing what to expect, but I pretty much assumed that everybody was right and that the engine, when covered with insulation, styrofoam in this case, would slow down and stop almost immediately, and that I could then post this video showing how the engine could be brought to a stop repeatedly and reliably by blocking the flow of heat with insulation. That really was my intention, but it didn't turn out that way. Instead the engine just ran a little faster!

https://youtu.be/fFByKkGr5bE

The cup of hot water, BTW is double wall, vacuum insulated, just to retain heat and help to ensure heat went up through the engine rather than just the walls of the cup.

Tom Booth wrote: ↑Sat Jul 08, 2023 11:54 am

stephenz wrote: ↑Sat Jul 08, 2023 11:12 am Another quick test you can do:

Insulate your heat rejection plate (cooler) with some kind of foam.
If you are correct the engine will run the same way. But if engine the slows down and comes to a stop quicker than without the insulation, then you will know.

LOL.... Ha ha!!

Sorry, but I guess you haven't been following this series of experiments.

With foam insulation over the cooler/heat rejection plate the engine only ran faster!!!

That was years ago.

I may not have watched the whole series but I've watched some and even commented on it in my engine pressurization thread.
I was suggesting that the foam material you used may have been a different temperature, low enough for the engine to keep running for at least some time.

Again, if you run the calorimetry number you will see that you are dealing with very low power and as such, temperature deltas will be small, i.e. you need accurate and calibrated tools to make your measurements and more generally speaking run your experiments.

These LTD engines are designed off extremely heat sources and it doesn't take much to get them going. I think it's primarily why you are drawing these conclusions. Your data is probably well within the noise range of test setup and metrology.


Ignore the insulation experiment if you are not able to control (or at least measure) accurately the temperature of the insulator.

Either way, my point of repeating your experiment with another set of temperature measurement tools remains valid. I wouldn't understand why you wouldn't to do it, if you don't have the equipment then layout your protocol in details and I will gladly set it up for you: either you're right and your claims will have gain a significant amount of credibility in my book (and probably others' too), or you're wrong and you can focus on other interesting developments. Those engines and this cycle are fascinating and there are plenty of avenues to explore and research. Isn't that the point of these forums?

The ordering of the playlist was on "shuffle" or random, so what I said about the "first" video in the playlist may be confusing

I just switched the ordering to play the earliest video first which maybe makes more sense.

I was talking about this video, where the engine with the acrylic bottom started out cold and the aerogel blanket was rubbing against the flywheel.

https://youtu.be/WveuREfKwVg

stephenz wrote: ↑Sat Jul 08, 2023 12:43 pm

Tom Booth wrote: ↑Sat Jul 08, 2023 11:54 am

stephenz wrote: ↑Sat Jul 08, 2023 11:12 am Another quick test you can do:

Insulate your heat rejection plate (cooler) with some kind of foam.
If you are correct the engine will run the same way. But if engine the slows down and comes to a stop quicker than without the insulation, then you will know.

LOL.... Ha ha!!

Sorry, but I guess you haven't been following this series of experiments.

With foam insulation over the cooler/heat rejection plate the engine only ran faster!!!

That was years ago.

I may not have watched the whole series but I've watched some and even commented on it in my engine pressurization thread.
I was suggesting that the foam material you used may have been a different temperature, low enough for the engine to keep running for at least some time.

Again, if you run the calorimetry number you will see that you are dealing with very low power and as such, temperature deltas will be small, i.e. you need accurate and calibrated tools to make your measurements and more generally speaking run your experiments.

These LTD engines are designed off extremely heat sources and it doesn't take much to get them going. I think it's primarily why you are drawing these conclusions. Your data is probably well within the noise range of test setup and metrology.


Ignore the insulation experiment if you are not able to control (or at least measure) accurately the temperature of the insulator.

Either way, my point of repeating your experiment with another set of temperature measurement tools remains valid. I wouldn't understand why you wouldn't to do it, if you don't have the equipment then layout your protocol in details and I will gladly set it up for you: either you're right and your claims will have gain a significant amount of credibility in my book (and probably others' too), or you're wrong and you can focus on other interesting developments. Those engines and this cycle are fascinating and there are plenty of avenues to explore and research. Isn't that the point of these forums?

I have all kinds of instrumentation, but at this point there are a few problems.

One, I've worn out nearly every model engine I have, through hours and hours of experiments. The graphite pistons don't last.

Two, I rarely have time for endless experimenting, and I do mean endless. It seems nothing is ever good enough to prove meaningful. The instrumentation is faulty, the insulation is no good, the engine, the experimenter, whatever, there hardly seems any point in bothering, nothing I can do is ever going to change anyone's mind, if the experiment seems foolproof, I'll just be accused of somehow faking the video or something.

But I understand, I'm a skeptic myself. If I were only watching videos of someone else's experiments, rather than doing them myself, and believed it was impossible, I'd think it was a fake.

BTW, you say first of all that I should insulate the cold side with foam and the engine should slow down and come to a stop.

Fair enough, but I've done that experiment dozens of times and it doesn't slow down or stop the engine at all.

Then you say you've watched the videos but go on to say

I was suggesting that the foam material you used may have been a different temperature, low enough for the engine to keep running for at least some time.

What makes you think the foam, sitting in the same room the whole time or actually taped down to the top of the engine would be a different temperature or colder?

"Keep running for "some time"?

What is "some time"?

It seems clear you have not watched much because I've run several engines for hours on end with the top as insulated as possible with the best most effective insulations available, or multiple layers of insulation, acrylic, aerogel, ceramic fiber, trapped air under glass...

Yet the engine continues to run quite well, apparently indefinitely, or at least hours and hours on end.

So, you have already moved the goalpost in the course of our brief discussion. Pretty obviously have not actually given much attention to watching any videos before drawing conclusions.

stephenz wrote: ↑Sat Jul 08, 2023 11:08 am

Here's the thing: there is very little heat entering the engine to begin with. Have you tried estimating the heat entering your engine?

Let's assume there is no losses through the side walls or bottom of your cup and that all the energy in the water will be transferred to the heater plate of your engine. The maximum amount of heat entering the engine can easily be calculated by basic calorimetry:

- known amount of water, i.e. its mass M
- water specific heat is known, Cp
- you know the start temperature, let's call that Ti
- you can decide at what temperature you want to stop the experiment, let's call that Tf
- of course time your experiment, measure Ti and Tf and the time it took to get to Tf

Once you have those numbers laid out, we can easily calculate the amount of heat entering your engine. I think you should do it if you haven't already.

It's been a while since I used an LTD but if you're not willing or if you don't have the tools to get those measurements, maybe I will.

How about calculating it on the basis of the experiment where the engine is running over a steam generator for three hours

The steam is trapped under the engine in a closed column/tube so it hits the bottom of the engine, condenses, then the water droplets fall back into the boiler. This process continues for three hours.

Can you calculate anything from that?

https://youtu.be/l2XcnN6QdfA

The label on the electric steam generator has a rating of 100 watts.

I have nothing to prove, yet I am willing to do some experiments for you, just layout your protocol and I will run your experiment with instrumentation that has at least one order of magnitude better accuracy than yours. Send me links to the engine you want me to buy.

All I need to see is one thermocouple mounted to the cooler surface reporting a temperature lower than that of the ambient.


To me, that should be your only focus. Your rant on Carnot is moot compared to your observations breaking the second law. So let's focus on that first.

I took the time to provide constructive feedback on your experiment, I gave my opinion as I allowed to do that. Pardon me for having an opinion I guess. As far as I am concerned, until more thorough testing is done (by you or anybody else), I will ignore all other/secondary topics.

https://protonsforbreakfast.wordpress.c ... king-bird/

Send me links to the engine you want me to buy.

All I need to see is one thermocouple mounted to the cooler surface reporting a temperature lower than that of the ambient.


To me, that should be your only focus

Personally I think the bird meets your requirements as stated, does it not?

The engine from my video that appeared to exhibit some other form of below ambient cooling, (without involving evaporation), for an extended period of time had the piston stuck in the cylinder and the graphite piston, when I managed to punch it loose with a dowel appeared cracked.

Before that experiment the piston had been replaced, but the new piston was a very tight fit. Too tight really.

Anyway, I'm working on making repairs. While I'm at it I'm making some modifications.

I'm replacing the aluminum power cylinder and graphite piston with ones made of borosilicate glass, this cylinder and piston pair have very good clearance providing a nice airtight seal but low friction. I'm not sure if less friction will increase or decrease the apparent cooling as the work involved overcoming the additional resistance from the too tight piston may have had some influence on the apparent cooling effect.

The glass cylinder was just set in place using epoxy and will take some time to cure. After that I should be able to put the engine back together and run some tests.

No the drinking bird example certainly does not qualify to justify your own observations. edit: unless of course, you covered the top plate with a wet fabric. haha

The Stirling engine rejects waste heat through a cooler (heat sink) which has a temperature greater than that of the environment.
The drinking bird rejects heat to the environment through evaporation, to what the temperature drop of of the head is a buy product of its energy behind removed by the phase change process.

Now let me ask you this:
How is your engine altered compared to a standard LTD engine? Wouldn't a standard LTD engine be capable of exhibiting the same behavior as the engine depicted in your video?



a simple, good read: https://arxiv.org/pdf/1812.04415.pdf