Is Carnot efficiency valid?

[Tom Booth]

9 hours ago, Ghideon said:

I disagree, there are too many unknown variables.

 

 I don't see how that experiment helps you debunk established theories.

I'll take a look at this later!

I agree ice may not be ideal, why the next experiment will be using temperature probes. But it is possible, I think, to get by with ice if all the variables associated with it are kept constant. Kept in the same freezer, removed at the same time, distilled water without contaminants, same measured quantities of water used to make uniform ice cubes, etc.

With a hot object between two engines, with nowhere to go except out as either work OR heat, through the engines working fluid and virtually nowhere else?

Think.

It won't necessarily overturn anything. It could absolutely confirm the amount of heat output predicted by the C. Efficiency equation. As I've said many times, I'm not trying to prove or debunk anything one way or the other. Just trying to get to the objective truth. I want to know how Stirling engines actually operate so some improvements can be made, if possible.

On the other hand if their is zero waste heat or even a refrigerating effect at the sink, (outside surface of the two engines) that should be quite easy to determine as well.

If one of those ceramic heaters is used between the engines and no heat ever appears on the ambient sides after hours of continuous running what would we conclude from that?

Edited February 8, 2023 by Tom Booth

[Tom Booth]

4 hours ago, swansont said:

5 hours ago, Tom Booth said:

Not trying to be argumentative but the bolts and convective air currents both outside the engine's working fluid could potentially account for at least some of the difference.

Only some? It needs to account for all of it if your assertion is correct

What is being investigated is the Carnot efficiency limit, not any wild speculating on my part.

At the ∆T in your experiment. What would the expected % of waste heat going to the "cold reservoir" be?

Did you say boiled water and ice?

There is a somewhat wild variable thrown in there, an additional heat source (ambient all around, temperature undisclosed) but neglecting that and being very generous, you've got what 27% efficiency?

So my hypothesis is that the Carnot formula might not be totally accurate and may be underestimating actual efficiency.

Does that not mean then that at an absolute minimum, 73% of your heat from the hot water needs to be passing through to the top of the engine? (The percentage Increasing as the cup of hot water cools down and efficiency drops)

So your "It (heat conducted through the bolts etc.) needs to account for ALL OF IT" is not actually true.

Anything less than 73% heat transport to the sink would invalidate the Carnot efficiency formula. Is that not correct?

Edited February 8, 2023 by Tom Booth

[Tom Booth]

7 hours ago, swansont said:

You are free to replicate this, as you have repeatedly been invited to do.

Actually, your setup is somewhat novel. I suppose I could,... Well "replicate" may be the wrong word.

I have two of these acrylic top engines. I could run one on a cup of hot water with ice on top, one on a cup of hot water also with ice on top but not running.

As these acrylic engines have no bolts that eliminates all extraneous variables I believe. Do you agree?

The circumstance of ice on your countertop is very far from having all variables identical aside from the one variable in question.

Under the ice we will have the engines and the cups of hot water and the table.

The two cups can be heated up together in the microwave perhaps, to avoid having one cup cool down slightly while the other is being poured.

Have I forgotten anything?

Do you agree to this setup?

The only variable will be engine #1 running and engine #2 not running.

Would this be a fair and reasonable comparison?

Perhaps I should manually work the flywheel back and forth on the non-running engine so the displacer does not act too much as an insulator sitting idle on the bottom of the non-running engine, or should we give it that advantage?

Edited February 8, 2023 by Tom Booth

[Tom Booth]

If I were for example, to place one ice cube directly on the table, and another ice cube over a cup of hot water perched on a metal scaffold, the scaffold consisting of two metal plates connected together by metal posts, what would be the result?

I would think the same result as seen in this experiment (by our esteemed Swansont). The ice perched above the cup of hot water, thermally connected to that "hot reservoir" by a metal scaffold would, of course be expected to melt before the ice cube merely sitting on a table with no heat source whatsoever below it.

What does this experiment tell us about what influence the engine running may or may not have on the ice one way or the other?

IMO nothing as too many variables are not held constant, not controlled or entirely unknown (in this case apparently intentionally withheld i.e.: conductivity of the countertop, as if the material and conductivity of the object a piece of ice is sitting upon has no influence)

[studiot]

11 hours ago, swansont said:

Heat is not kinetic energy.

Heat is the transfer of energy owing to a temperature difference. This can happen via radiation, conduction or convection.

The thermal energy of a body is related to kinetic energy of constituent atoms or molecules, which we associate with temperature. But two objects at the same temperature will have not heat transfer between them, despite having vibrational KE

An admirable summary of the most important points about the nature and source of heat, including the often missed point about transfer being dependent upon transfer difference. +1

 

I would just like to add one further often missed point, about radiation.

Conduction and convection are well enough described by molecules jiggling about. But where does radiation fit in - there are no molecules carrying it ?

Well where there are molecules in motion there are also electrons in motion.
Electrons are charged particles in local EM fields and such charged particles in motion emit photonic radiation,

 

[Tom Booth]

If anyone is interested, what I would consider my best guess at how a Stirling engine actually operates is this:

When I first started learning about how to build a Stirling engine, an experienced model Stirling engine builder told me that the way be determined the throw of the piston, that is; the distance it should travel between TDC and BDC was to heat up the engine to whatever heat source is going to be used with the displacer down (covering the hot side, preventing heat from being transfered to the working fluid) then manually lift the displacer. The working fluid will then take in heat and expand, then watch how far the piston travels in the cylinder The piston has not yet been attached to the crankshaft or flywheel. Make the throw or the piston a little longer .

He didn't explain exactly why. At the time I could not conceive of any good reason for making the distance the piston traveled MORE than it wanted to travel. I'm not sure he knew why. Some things are learned as a result of trial and error. Perhaps all he knew was that it works; to make the piston go a little further out than it "wants" to go naturally.

Now I believe I have figured out WHY that works.

To begin with, the engine is at thermal equilibrium with itself and the environment; then heat is introduced; then the gas expands and does work driving the piston. The gas transfers the energy of the expansion work to the piston. As the piston moves out it accelerates gaining momentum.

Now once the energy that was added is all transfered to the piston, the gas has cooled back down to the original temperature.

The piston, however must travel a little further. It accomplishes this using the stored up energy that was just transfered to the piston.

This "extra" distance the piston has to travel means that the working fluid will be mechanically expanded while simultaneously continuing to transfer additional energy to the piston.

Why does the gas still transfer energy? Because the piston is still moving and the expanding gas is still pushing it. The working fluid inside the engine "knows" nothing regarding the atmospheric pressure on the other side of the piston, so it is still doing "work", still pushing the piston, still loosing heat. In effect, the gas is undergoing a refrigeration process, the gas is being expanded.

Rather than acting as a heat engine; due to the extra distance the piston has to travel as a result of its own stored up momentum; the engine has become a Stirling heat pump or cooler. An expansion engine.

The working fluid undergoes a rapid decline in temperature and drop in pressure.

Now atmospheric pressure drives the piston back inward and the process repeats.

There is no "heat transfer" through the engine. No need for a sink.

The engine itself effects its own cooling, which allows the piston to return under atmospheric pressure.

Edited February 8, 2023 by Tom Booth

[swansont]

6 hours ago, Tom Booth said:

Actually, your setup is somewhat novel. I suppose I could,... Well "replicate" may be the wrong word.

I have two of these acrylic top engines. I could run one on a cup of hot water with ice on top, one on a cup of hot water also with ice on top but not running.

As these acrylic engines have no bolts that eliminates all extraneous variables I believe. Do you agree?

The circumstance of ice on your countertop is very far from having all variables identical aside from the one variable in question.

Under the ice we will have the engines and the cups of hot water and the table.

The two cups can be heated up together in the microwave perhaps, to avoid having one cup cool down slightly while the other is being poured.

Have I forgotten anything?

Do you agree to this setup?

No. Having hot water in the non-running engine does not test what is under contention, unless you are also asserting that there is no heat transfer across the engine while not running. And that’s ridiculous.

 

6 hours ago, Tom Booth said:

The only variable will be engine #1 running and engine #2 not running.

Would this be a fair and reasonable comparison?

No.

The test is whether heat is transferred to the cold side while the engine is running. You claim there is none. The only thing that would heat the cold side should be ambient air.
 

 

 

13 hours ago, Tom Booth said:

That would be difficult (exactly)  since you were unresponsive regarding some of the parameters.

Some details don’t affect the result. You don’t need to replicate the exact temperatures, since we aren’t trying to quantify the result. Only show that heat is transferred, since you predict that the value is zero.

 

13 hours ago, Tom Booth said:

Anyway I already have, many times, except for modifications: replacing highly conductive metal bolts, insulating air passages between the plates and so forth to eliminate extraneous variables.

Some of your conclusions seem questionable. A metal heat exchanger doesn't conduct heat under water sitting directly on top of it, only to the extremities. Heat at the edge of a .metal plate remains only at the edge. No difference in conductivity between the metal of a heat exchanger and a countertop of some other, possibly non-heat conducting material, to name a few off the top of my head.

Oh, did you suggest heat conducted by metal bolts to a metal plate remains completely localized

I showed a thermal image. It shows the temperature profile and would display a temperature gradient if one existed. But you can see that the water near the center is heated as well.

 

 

10 hours ago, Tom Booth said:

What is being investigated is the Carnot efficiency limit, not any wild speculating on my part.

No, that’s not what I was testing.

You claimed that no heat is sent to the cold reservoir. My experiment was done to show that this is not true.

 

10 hours ago, Tom Booth said:

At the ∆T in your experiment. What would the expected % of waste heat going to the "cold reservoir" be?

It’s more than zero, which rebuts your claim.

 

10 hours ago, Tom Booth said:

Did you say boiled water and ice?

The water on top and on the counter was cold, not ice. The temperature displayed by the thermal image shows this.

 

10 hours ago, Tom Booth said:

There is a somewhat wild variable thrown in there, an additional heat source (ambient all around, temperature undisclosed) but neglecting that and being very generous, you've got what 27% efficiency?

I wasn’t measuring the efficiency.

 

10 hours ago, Tom Booth said:

So my hypothesis is that the Carnot formula might not be totally accurate and may be underestimating actual efficiency.

Does that not mean then that at an absolute minimum, 73% of your heat from the hot water needs to be passing through to the top of the engine? (The percentage Increasing as the cup of hot water cools down and efficiency drops)

So your "It (heat conducted through the bolts etc.) needs to account for ALL OF IT" is not actually true.

It’s true in regard to your claim that no heat is rejected by this engine

 

 

[Tom Booth]

54 minutes ago, swansont said:

No, that’s not what I was testing

Then your experiment is off topic. 

This topic here: Is Carnot efficiency valid?

Regardless of what you were testing your experiment is terribly flawed in the ways pointed out as you have not replicated the conditions I have  clearly specified for making the observations I reported on.

Perhaps, if you want to investigate that, you should start a new thread on the subject but you would need to clean up your methodology which demonstrated an extreme incompetence.

[swansont]

1 hour ago, Tom Booth said:

Then your experiment is off topic. 

You made the claim in this thread, and it’s apparently part of your Carnot efficiency argument. 

Quote

Perhaps, if you want to investigate that, you should start a new thread on the subject but you would need to clean up your methodology which demonstrated an extreme incompetence.

As I said, you are free to do your own experiment, but since it will obviously undermine your position, I can see why you might hesitate to do it.

As a proof-of-principle experiment, I think it’s fine. If I was quantifying the effect it would require more care. I’ll leave it to others to assess my competence. 

[Tom Booth]

11 minutes ago, swansont said:

You made the claim in this thread, and it’s apparently part of your Carnot efficiency argument. 

As I said, you are free to do your own experiment, but since it will obviously undermine your position, I can see why you might hesitate to do it.

As a proof-of-principle experiment, I think it’s fine. If I was quantifying the effect it would require more care. I’ll leave it to others to assess my competence. 

The first prerequisite for replicating any experiment I've conducted, as I've mentioned previously, is to eliminate any metal heat conducting parts that might transfer heat between the hot and cold plates (i.e. begin by replacing the metal bolts, if present, with non-heat conducting bolts) otherwise it is the near equivalent of trying to test an electrical resistor with six conductors bridging the gap.

You've conducted a strawman experiment that completely ignores this first prerequisite, among the several other conditions I've already outlined.

[swansont]

3 minutes ago, Tom Booth said:

The first prerequisite for replicating any experiment I've conducted,

I was not trying to replicate an experiment you had conducted.

I was doing an experiment that you had not conducted, but probably should have.

 

[Bufofrog]

1 hour ago, Tom Booth said:

but you would need to clean up your methodology which demonstrated an extreme incompetence.

How ironic.

[Tom Booth]

The relevant Heat transfer through a heat engine under investigation is that heat entering into or passing through the working fluid and only the working fluid, which means eliminating, as far as possible, all other avenues for heat transfer. You made no attempt whatsoever in that direction as evidenced by the luminous glow of the "hot spots" on your model

30 minutes ago, swansont said:

As I said, you are free to do your own experiment, but since it will obviously undermine your position, I can see why you might hesitate to do it.

There is no hesitancy on my part to conduct experiments. That's an obvious mischaracterization. 

7 minutes ago, swansont said:

I was not trying to replicate an experiment you had conducted.

I was doing an experiment that you had not conducted, but probably should have.

 

Well I'm glad to see some kind of effort being put into this but you seem completely unable or unwilling to entertain any criticism of your methodology. If your intention is to prove this experimenter wrong, there should at least be some effort put into understanding the protocol of my experiments.

 

 

[swansont]

1 hour ago, Tom Booth said:

The relevant Heat transfer through a heat engine under investigation is that heat entering into or passing through the working fluid and only the working fluid, which means eliminating, as far as possible, all other avenues for heat transfer. You made no attempt whatsoever in that direction as evidenced by the luminous glow of the "hot spots" on your model

As I said, if the heat transfer was solely from the bolts, there would be an obvious temperature gradient toward the middle. We don’t see that - we see a fairly uniform temperature profile, consistent with heat being transferred through the whole plate.

 

1 hour ago, Tom Booth said:

There is no hesitancy on my part to conduct experiments. That's an obvious mischaracterization. 

I suggested this experiment on Jan 28, and it took about 10 minutes to complete. You’ve spent more time trying to come up with ways to explain away the results. You’ve apparently spent zero time doing this experiment.

 

1 hour ago, Tom Booth said:

Well I'm glad to see some kind of effort being put into this but you seem completely unable or unwilling to entertain any criticism of your methodology. If your intention is to prove this experimenter wrong, there should at least be some effort put into understanding the protocol of my experiments.

I’m not trying to replicate your experiments, and I’ve already noted how useful I find your videos and experiments. I’m trying show that one of your claims is wrong, which you could have made without videos or experiments. Since you have thus far not done some form of this experiment, I went ahead and did it.

[Tom Booth]

53 minutes ago, swansont said:

As I said, if the heat transfer was solely from the bolts, there would be an obvious temperature gradient toward the middle. We don’t see that - we see a fairly uniform temperature profile, consistent with heat being transferred through the whole plate

Sure Looks like a temperature gradient to me.

White hot at the bolts transitioning through yellow, orange,violet, purple,to nearly black.

[Ghideon]

1 hour ago, Tom Booth said:

Sure Looks like a temperature gradient to me.

You seem to cherry pick the first picture? What about the picture that show the experiment at a later state? 

 

Edited February 8, 2023 by Ghideon

[Tom Booth]

 

2 hours ago, Ghideon said:

You seem to cherry pick the first picture? What about the picture that show the experiment at a later state? 

 

You do realize that if the top plate is continuously heated so is the working fluid every time it is shunted up or down.

I try to get it through my thick head that not everybody lives and breaths Stirling engines every day the way I have for the last 15 years or so, so these things are not readily apparent

I'll try drawing a picture. Hopefully that will make things clear.

If effectively you have six heating elements distributed around the cold plate, along with hot convective air currents, that is inevitably also heating the cold expanded working fluid above the displacer.

The working fluid is constantly in motion so the heat gets washed out, distributed more evenly as time goes on.

 

Edited February 8, 2023 by Tom Booth

[exchemist]

11 minutes ago, Tom Booth said:

 

You do realize that if the top plate is continuously heated so is the working fluid every time it is shunted up or down.

I try to get it through my thick head that not everybody lives and breaths Stirling engines every day the way I have for the last 15 years or so, so these things are not readily apparent

I'll try drawing a picture. Hopefully that will make things clear.

If effectively you have six heating elements distributed around the cold plate, along with hot convective air currents, that is inevitably also heating the cold expanded working fluid above the displacer.

The working fluid is constantly in motion so the heat gets washed out, distributed more evenly as time goes on.

 

Again, not answering the question but instead introducing another irrelevant distraction. 

-1. 

 

[swansont]

It probably took longer to draw those pictures than it would to do the experiment with your engine that has the insulated bolts.

[Tom Booth]

12 minutes ago, exchemist said:

Again, not answering the question but instead introducing another irrelevant distraction. 

-1. 

 

What question.

And how is what I illustrated "irrelevant"

You folks seem to have no comprehension of heat distribution in a Stirling engine. Don't know what more I could do to make it any clearer.

The heat from the bolts is heating the top plate as well as the air inside the engine below it.

The cold expanded air is forced upward directly impacting those hot zones around the perimeter every cycle.

4 minutes ago, swansont said:

It probably took longer to draw those pictures than it would to do the experiment with your engine that has the insulated bolts.

That would not be "replicating" your experiment, which is crap.

I've already done experiments of that sort, with nylon bolts.

Edited February 8, 2023 by Tom Booth

[swansont]

3 hours ago, Tom Booth said:

The heat from the bolts is heating the top plate as well as the air inside the engine below it.

How is the bolded part possible, if, as you claim, the engine doesn’t reject heat to the cold reservoir?

3 hours ago, Tom Booth said:

That would not be "replicating" your experiment

I didn’t say replicate. I said do it with your setup.

 

Quote

I've already done experiments of that sort, with nylon bolts.

“of that sort”? You measured the temperature rise of a cold reservoir that starts below ambient, with a control to assess the heat absorbed from the ambient surroundings? 

 

[Tom Booth]

4 hours ago, swansont said:

How is the bolded part possible, if, as you claim, the engine doesn’t reject heat to the cold reservoir?

What is "the engine"?

Carnot limit says "IMPOSSIBLE" for ANY engine to get better than Carnot efficiency (calculated from the ∆T) "rejecting" no less than the reciprocal.

So a little model Stirling on a 20% efficiency supposedly MUST "reject" the other 80% to the cold side or could not complete a single revolution or a single cycle.

I've done some common sense modifications to reduce heat loss like replacing the heat conducting bolts, changing the throw of the piston in some cases, adjusting the timing/advance, maybe incorporate a small regenerator and so forth, and have had engines run for long durations with no measurable heat transferring to the cold sink side whatsoever. Supposedly that should NOT be possible.

Some kits give a lot of leeway as far as how the engine is assembled, so sometimes you see these engine behave in strange ways.

Experienced model builders know how to build an engine from scratch, turning the cylinders on a metal lathe so I'm basically talking about customized engines constructed by experienced machinists not some imported piece of junk that can barely run no matter what you do to it.

To put it bluntly: your engine is garbage and your experiment is garbage. You are in no way an experienced and knowledgeable engine mechanic or machinist capable of building or putting together a machine that would display any of the unusual characteristics observed in any of my experiments.

If you would like to see at least some hit of the possibilities you would have to get out a screwdriver and pair of pliers and maybe a hand drill and go to the hardware store and make some modifications on that silly little engine.

I've tried to be encouraging but you have been rude, arrogant, pompous, disrespectful, insulting, and you name it. You and your little band of hecklers.

So "the engine" no, not "the" engine, not just any engine you happen to pick up on Amazon.

A properly built and/or if necessary, modified engine.

You are not going to see the phenomenon I've been writing about and video recording if you refuse to make some minor modifications to your piece of crap engine.

Or you could watch my videos, but you don't like videos.

If you won't listen and are just intentionally avoiding everything I say should be or needs to be done just in an effort to try to prove me wrong with your so-called crap, straw man experiment I don't see much point in wasting much more time here debating your pile of horse shit so-called experiment.

Edited February 9, 2023 by Tom Booth

[Ghideon]

Side note while I wait answers to some previous questions:

On 2/7/2023 at 6:25 AM, Tom Booth said:

The other way around might be interesting too. Sandwich the heat source between two engines.

Have you thought of combining the two types of arrangements? It is probably too mechanically complicated to be useful or realisable but may trigger further ideas: Arrange an even number of Stirling engines in a "Stirling Ring"; hot against hot and cold against cold in a circle. In this thought experiment, what could be the result when applying your ideas?

[exchemist]

12 hours ago, Tom Booth said:

What question.

And how is what I illustrated "irrelevant"

 

The question in the post to which you were responding, of course. This was (just to remind you): "What about the picture that show the experiment at a later state? " 

The diagrams and stuff you posted instead of answering it were irrelevant, because they were trying (as usual) to change the subject, instead of answering the question that had been asked. 

Every time we get close to evidence that does not fit your preconceptions, you duck the issue and hastily veer off, with a smokescreen of more fiddly details of your experimental setup.  

I do not believe you are responding in good faith.

[studiot]

20 hours ago, Tom Booth said:

This topic here: Is Carnot efficiency valid?

 

Yes indeed, yet you have never actively discussed that topic.

Just added a few sentences here and there pouring scorn on the idea.

Just as you poured scorn on my diagram.

 

So let me ask you this.

Suppose you actually had a perfect Carnot engine and and a second engine that was more efficient that the Carnot one.

What would happen if you thermally connected both engines between the same pair of heat sinks with the more efficient one generating a mechanical work output from the available heat. But with the Carnot engine reversed (remember that the fundamental principle of a Carnot engine is that it is fully reversible) so that work generated by the efficient engine was used to drive the reversed Carnot engine to move heat from the cold sink to the hot sink  ?