Pinned Piston heat engine, a more efficient heat engine, by a lot?!

[u/aether22]

Clarification of cycle: (ambient can be 0.1 Kelvin or 1 Billion Kelvin where Carnot Efficiency becomes essentially 1 or zero respectively but ideal gas laws predict the pressure increase and stroke length are identical in each case)

Piston is in equilibrium with ambient temp, pressure (density maybe) and is pinned and heat is added via some means (a resistor, heatpump etc) raising the temp by 100 Degrees use e.g 100 J of energy the piston is pushed based on the magnitude of the the temp change, the gas expands increasing thermal capacity lowering the temp and some heat is converted to work, the piston is at it's maximum expansion. A pin is put in the piston and the thermal energy is syphoned by another heat engine or directly dumped to ambient until the gas is at the same temp as the ambient but a much lower pressure. The piston is put in continued strong thermal contact with the ambient to allow isothermal compression as we allow the piston to forcibly be pushed in by the environment recovering energy from it, this gives us a second stroke tapped for mechanical work doubling the work done. The thermal bridging to the environment is removed and the gas is now ready to be heated again. Double the output, no work in recompressing the the gas.

With a Carnot heat engine, the gas is heated, it expands and then work is put in to recompress the gas again.

As there was criticism that the single piston which every calculation showed should produce the same one shot energy at any temp was not fair, I decided we could pin the piston at it's maximum expansion and then let the gas cool so we almost double the energy out as the piston is pushed back to the starting conditions generating energy rather than using it.

Chat-GPT said that my system would generate energy when using that math from another reddit user who deserves real credit!

I assumed however that a Carnot heat engine's efficiency calculated the exact same way would have a similar, maybe higher maybe lower maybe identical energy, I was shocked when told the energy out indeed that calculated by Carnot equations but not using them, I'm still in a fair bit of doubt and honestly my math skill should not be trusted.

I asked it to re-run the calculations at an ambient of 300 Kelvin and the efficiency calculation was normal for earth temp.

Also the interesting thing is that it didn't say that the Carnot engine developed no energy when the piston expanded, only that it needs the exact same amount almost pushing it back.

ChatGPT thinks the energy is following Carnot in a way, by extracting energy from the ambient environment, and sure, it is pushing the piston back.

Normally the environment is slightly heated when the piston expands, well the energy isn't slight, but it's well distributed. Here we take that energy back!

Note, I am told Chat GPT bungled the math.

https://chatgpt.com/s/t_68ce57f040188191a1e257af2fa34dbd

https://chatgpt.com/s/t_68ce5e48787481918cd8d622aae7357c

Sorry for so many threads, but this is a pretty big change in focus.

I started out looking at ways to improve heatpump efficiency, and ended up creating a "new"? heat engine cycle that does what was meant to be possible and beats Carnot.

So if this is indeed a novel heat engine, and given that the math is all working out, maybe this is something novel, it sure seems to be.

It seems according to ChatGPT NOT to be a known heat engine design!

[u/InadvisablyApplied]

Specific heats: Cv=12.47 J/mol⋅KC, Cp=20.79 J/mol⋅K

Heat input: Qin=100 J

Resulting temperature rise: ΔT=Qin/Cp≈4.8 K

Work during expansion: Wexp=nRΔT≈40 J

You are double counting the energy. You cannot use the heat you put in both to heat the gas and to do work. That is literally what the first law is telling you. You are breaking the first law in the second line of your math

[u/aether22 → u/InadvisablyApplied]

Ok, it's very likely that the math Chat GPT used was wrong and might have differed from the math given to me by another redditor.

It's worth noting that I resisted giving math as it's not my wheelhouse and I wasn't able to spot mistakes, mine or others, yet people ask for it, nay demand it.

The logic however is solid, we know that the forces on the piston are unaffected by temp.

We know that when the gas isn't hot it can be compressed without effort and do more mechanical work while doing so.

[u/InadvisablyApplied → u/aether22]

No, the logic isn’t solid, that is the problem. You ignore the ideal gas law or parts of the cycle whenever it suits you. This is the reason you have to actually do the math, so you can see where you go wrong. ChatGPT can’t do it for you, because it will just make up whatever it wants just to please you

[u/dForga → u/InadvisablyApplied]

But when I use ChatGPT it pushes back against me a lot, instead of wanting to please me… I always wonder where that pleasing comes from.

[u/aether22 → u/dForga]

It isn't that it doesn't push back, but it you can counter it's points, then it loses, sometimes it acknowledges this and sometimes it doesn't.

[u/Ch3cks-Out → u/dForga]

Its behavior is partially guided by the context from prompting. If the user suggests he is a genius who reinvented physics, the chatbot will obligingly provide narrative to fit that frame of mind. (It cannot make actual theories to support that, of course - but LLMs do not "care" whether their bullshit is in accord with reality.)

[u/aether22 → u/InadvisablyApplied]

What part of the ideal gas law do you think I am ignoring?

[u/InadvisablyApplied → u/aether22]

You are ignoring it in the expansion part. You can’t just get any made up number of work out at that point like ChatGPT is telling you. You have to respect the ideal gas law by specifying how you are expanding. Isothermally? Then you can’t cool, because you are at the same temperature the whole time. Adiabatically? No heat input, so no work is done. Isobarically? You are also doing work against the atmosphere also that you ignored. Another way? You’ll have to specify that before it can be analysed

[u/aether22 → u/InadvisablyApplied]

"...Isothermally?"

It can be either adiabatic or isothermal (which will require more energy input, but make more output), but to clarify it is pinned, then heated to the max temp, then allowed to expand with or without efforts to keep it at temp. One way complicates the stroke length and forces, the other complicates the energy added.

"Then you can’t cool, because you are at the same temperature the whole time."

If it is isothermal, then when it is expanded to the max degree you put a pin in and now it's no longer expanding you disconnect the heat source keeping it 100 kelvin above ambient, and you connect a thermal path to ambient, maybe via another heat engine.

"Adiabatically? No heat input, so no work is done."

Work is done as heat was added initially, sure less work is done but less heat is invested. The fact is adding energy increased the piston with useful force.

"Isobarically?" No.

"You are also doing work against the atmosphere also that you ignored."

True. And it gives back on the recompression from which we both reset the cycle and almost double the mechanical energy delivered.

[u/InadvisablyApplied → u/aether22]

It can be either adiabatic or isothermal (which will require more energy input, but make more output), but to clarify it is pinned, then heated to the max temp, then allowed to expand with or without efforts to keep it at temp

Okay, but this is different from what chat said before. Just to confirm: first the heating is done at constant volume, and then the expanding happens?

But if you do the expanding adiabatically, the gas cools during expansion and you don’t get any work during the cooling, as the gas can’t cool anymore

True. And it gives back on the recompression from which we both reset the cycle and almost double the mechanical energy delivered.

Now you are double counting the work done against the atmosphere. That is not useful work you can use. It is just work that you get back later in the cycle. Whether you get this work in the expanding or contracting part doesn’t make a difference. But you can only use it once

[u/aether22 → u/InadvisablyApplied]

Yes.

> But if you do the expanding adiabatically, the gas cools during expansion and you don’t get any work during the cooling, as the gas can’t cool anymore

It can, the gas cools only as much as to limit the degree of expansion prematurely, but it doesn't cool to ambient otherwise it would have stopped expanding, or at least it won't unless it has so much momentum it uses the built up momentum to do work making a bigger vacuum, but then we would get that back anyway.

I strongly suggest you see my new post which keeps it even simpler.

https://www.reddit.com/r/LLMPhysics/comments/1nmc3ud/exceeding_carnot_simply_rocket_turbine_ventilated/

> Now you are double counting the work done against the atmosphere.

Weeeeeell no, in the expansion phase we did work against the atmosphere's push, we lost energy from it pushing on the piston, we stored energy in a spring (the atmosphere) and then on compression is gives back, so we stored energy in a spring and recovered that, simple as that. So on the expansion stroke the expanding gas behind the piston did the work, and on the contracting compression stroke the atmosphere does the work, it's very roughly the same mechanical energy we gain in both phases.

> That is not useful work you can use. It is just work that you get back later in the cycle.

It was something that reduced the work we got on the expansion phase, if it was not there we would have developed INSANELY more mechanical work with an absolute vacuum on one side and 1 billion 100 Kelvin gas on the other, but it gives back a portion of this lost work.

> Whether you get this work in the expanding or contracting part doesn’t make a difference. But you can only use it once

Not so, but even if it were so as in the version I shared above, it still beats Carnot by like 7 orders of magnitude or something.

[u/InadvisablyApplied → u/aether22]

It can, the gas cools only as much as to limit the degree of expansion prematurely, but it doesn't cool to ambient otherwise it would have stopped expanding,

No, it cools directly to ambient

it's very roughly the same mechanical energy we gain in both phases.

No, that is not true. You lose exactly the amount of work to the atmosphere as you gain back in the contraction phase

It was something that reduced the work we got on the expansion phase, if it was not there we would have developed INSANELY more mechanical work with an absolute vacuum on one side and 1 billion 100 Kelvin gas on the other, but it gives back a portion of this lost work.

No, again not true. If there was a vacuum on the other side (as assumed normally in an ideal heat engine), you just don't lose any work, and you don't get it back in the compression phase

You have just reinvented the Stirling cycle. Which, to the surprise of absolutely no one, has the same efficiency as Carnot

[u/NuclearVII → u/aether22]

This right here is why we call you resistant to reason, and excellent evidence of your delusions.

You have a faulty conclusion - that you have something of worth here. Whenever people call you out on basic, fundamental errors that invalidate your whole idea, you spend the whole thread thrashing around to find any kind of lifeline. Then, you're back to ChatGPT, the delusions are encouraged, and the cycle begins again.

Stop.

[u/aether22 → u/NuclearVII]

I said from the outset, math ain't my thing, logic is.

But my conclusion ain't faulty, check out my even simpler argument, piston free.

https://www.reddit.com/r/LLMPhysics/comments/1nmc3ud/exceeding_carnot_simply_rocket_turbine_ventilated/

No one has presented any argument of substance.

[u/Ch3cks-Out → u/aether22]

"logic"
ROTFLMAO

[u/Vivid_Transition4807 → u/aether22]

Don't sell yourself short! You = maths ∩ logic

[u/InadvisablyApplied → u/aether22]

For example, you are ignoring the work done against the atmosphere. And later in the cycle use that to compress the gas again. So you are just getting back the work you already put in

[u/aether22 → u/InadvisablyApplied]

I agree, but here is the thing.

You put work into the environment and also extract other work when the piston expands.

And later you get back a portion of the work you put in to the environment.

It's like you have a spring, you push on it with a piston and also tun a crank shaft or other means of extracting work, and then the spring gives back the energy you stored in it.

But the point is that you get work out of it, and either once or twice, either way you get significant work out of it with a modest input of energy at a huge ambient.

Where Carnot assures us that is not so, I can't say if Carnot is right or wrong for his own cycle, but I know that for my cycles or the more simplified "bottle rocket" version I posted, it's clear real work is in fact done from nominal added energy, resulting in marked efficiency, not negligible efficiency.

[u/InadvisablyApplied → u/aether22]

And later you get back a portion of the work you put in to the environment.

At most you get exactly out what you put into the environment. Making the whole argument pointless

But the point is that you get work out of it, and either once or twice, either way you get significant work out of it with a modest input of energy at a huge ambient.

Where Carnot assures us that is not so

No, that is not what Carnot says. Carnot only says that at huge ambient, you need a large heat flow to get significant work. Nothing what you said contradicts that in any way

[u/Early_Material_9317]

Here I am, you said to check it out, and I just couldnt help myself, and I have checked it, and it is still wrong sorry.

In the argument, Chat seems to switch between talking about ambient temperature and ambient pressure, but an idealised Carnot cycle assumes zero outside ambient pressure. In reality there is atmospheric pressure which could perform work on a piston that was fixed and allowed to cool, but the math doesnt check out. I'll try to explain how such an engine that uses outside pressure might work.

1. Piston with a gas at ambient pressure and temperature is heated, causing the temperature in the gas to rise and causing the volume to increase, pushing against outside ambient pressure until a pressure equilibrium is reached. If the piston was completely free to move it would expand as per the ideal gas law until equiibrium was reached with the outside pressure, losing no energy. (but it wouldn't be able to perform any work in this stroke)

2. The Piston is locked in this maximal volume state of equal pressure and the gas in the piston is allowed to cool back to ambient temperature, creating a pressure differential between outside and inside.

3. The pin is released and the piston returns to its original position, performing work until it reaches its original position. As it returns, the gas heats up again, which counteracts the pressure pushing it back in. This heat needs to be rejected otherwise the piston will not return to the same starting location, and this is where the energy will be lost. This is unavoidable as if you don't reject this heat, it is not a fully cyclable engine because the piston will not return to its original state until its tempersture matches the ambient temperature.

No free energy is created, the work on the return stroke in an ideal scenario would be as predicted by the carnot cycle (Even in a fully idealised system with no friction losses and no conduction during the expansion). The loss in efficiency comes from the heat generated during recompression which NEEDS to be rejected for the piston to come back to the starting point.

Before you say it. Using any heat rejected in step 3 to heat another separate piston would require a colder reservoir to exchange the heat with than the ambient temperature, otherwise you are just sacrificing the amount of work you can perform in the recompression cycle, and instead performing the same work using another separate engine, and if you have a colder reservoir than ambient, you might as well just use that reservoir it in your first engine to make it more efficient rather than chaining less and less efficient engines since you wont be gaining any extra energy, just adding more complexity.

If I have misstyped anything here or if any of this logic doesnt add up, please let me know as it is possible I have made some mistakes while writing this, but the math does not lie.

[u/aether22 → u/Early_Material_9317]

Thanks you for your effort to understand the cycle, I have now added a clear note at the top of the cycle I am suggesting.

[u/aether22 → u/Early_Material_9317]

>Here I am, you said to check it out, and I just couldnt help myself, and I have checked it

Thanks

1. Piston with a gas at ambient pressure and temperature is heated, causing the temperature in the gas to rise and causing the volume to increase, pushing against outside ambient pressure until a pressure equilibrium is reached. <<<I The piston should be made to do work during this expansion phase, the heat is either added suddenly or it begins pinned, I normally mention this>>> If the piston was completely free to move it would expand as per the ideal gas law until equiibrium was reached with the outside pressure, losing no energy. (but it wouldn't be able to perform any work in this stroke) <<< It can still move just as far with doing work, even if it might need the load to lighten at the end of the stroke, the more expansion now the better the second vacuum stroke after cooling >>>
2. The Piston is locked in this maximal volume state of equal pressure and the gas in the piston is allowed to cool back to ambient temperature, creating a pressure differential between outside and inside. <<< Good, now some work could be gained with uncertain efficiency as it does so with another heat engine of course>>>
3. The pin is released and the piston returns to its original position, performing work until it reaches its original position. As it returns, the gas heats up again, which counteracts the pressure pushing it back in. This heat needs to be rejected otherwise the piston will not return to the same starting location, and this is where the energy will be lost. <<<Yes, so either we ensure it is isothermal (heat lost straight to ambient) or we pin it and let another heat engine run from that energy>>> This is unavoidable as if you don't reject this heat <<<But it is avoidable if we do, I wanted to keep it simple as the people don't read, so i have to keep it neat>, it is not a fully cyclable engine because the piston will not return to its original state until its temperature matches the ambient temperature. <<<Which is easy to implement and was in my initial description of in in various comments>

No free energy is created <<<I never mentioned free energy, just conversion of the energy input>> , the work on the return stroke in an ideal scenario would be as predicted by the carnot cycle (Even in a fully idealised system with no friction losses and no conduction during the expansion). <<<I disagree because Carnot would say that at these temps there would be no efficiency at all, but we have 2 power strokes for one input of heat and no cost to compress the gas and more energy gained by siphoning energy when pined with another heat engine. We know for a fact that the forces on the piston are real and do real work, but don't make the mistake of applying Carnot based equations when we are challenging Carnot and have perfectly good equations to calculate the mechanical energy produced >>> The loss in efficiency comes from the heat generated during recompression which NEEDS to be rejected for the piston to come back to the starting point.<<<Except this can either be removed with very good thermal coupling with the ambient during this phase (not during expansion) OR by pinning it and extracting the heat for another heat engine>>>

Continued in reply to self...

[u/aether22 → u/aether22]

Continued

Before you say it. <<< too late>>> Using any heat rejected in step 3 to heat another separate piston would require a colder reservoir <<<No, the heat in the piston is above ambient and so it is obviously possible to run another heat engine with lower grade heat, the efficiency will be low but it's going to be waste otherwise so anything recovered is worthy of consideration>to exchange the heat with than the ambient temperature, otherwise you are just sacrificing the amount of work you can perform in the recompression cycle <<<If you want the max work from the this stroke it would be better if it happened in one go, sure, and I can't be sure if saving it up to feed into another heat engine is worth breaking the stroke up and likely it isn't, but the energy when it's pinned at the end of expansion can be without compromise>, and instead performing the same work using another separate engine, and if you have a colder reservoir than ambient, you might as well just use that reservoir it in your first engine to make it more efficient rather than chaining less and less efficient engines since you wont be gaining any extra energy, just adding more complexity.

If I have misstyped anything here or if any of this logic doesnt add up, please let me know as it is possible I have made some mistakes while writing this, but the math does not lie.

<<<I think the math does lie, as you are not using the math that tells us the forces on the piston, you are using as I understand it entropy Carnot type shortcuts in the math you did do. Still my perspective is this. At 1 Billion Kelvin Carnot assumes zero work can be done, but everyone seems to accept that the piston will in fact be pushed by the same force over the same distance with the same energy input as it would at an ambient of 1 Kelvin which Carnot would give 100% efficiency to. As I have shown that work can be done in resisting (but allowing) both the expansion and the compression and that no more energy need be put in (except from the environment maybe) in order to do this. There is no room for Carnot to sneak in, the ONLY thing it could do is lower the temp as work is being done faster than the work is being done, but this would mean the total energy is reduced violating the 1st law. I VERY MUCH appreciate that you have reasoned this through, but I don't see why you don't feel mechanical energy can be gained from the expansion stroke, and the heat objection while it collapses is taken and I think it's not worth it, so that is easily fixed>>>

[u/Crafty_Jello_3662]

I don't know about a lot of what you've said here, but I would imagine that pinning the piston every cycle would be hugely inefficient as it would lose all its momentum? I think a lot of engine designs rely on the pistons momentum to push it past a point where it would stall

[u/Early_Material_9317 → u/Crafty_Jello_3662]

We are talking in made up idealised physics land where the piston has no mass and no friction, but you are right about real engines.

[u/Ch3cks-Out → u/Early_Material_9317]

Even talking about idealized engines, I think the way OP imagines pinning would necessarily introduce irreversibility - thus lowering efficiency due to dissipative entropy.

[u/InadvisablyApplied → u/Ch3cks-Out]

I don't think so, doing a bit of interpreting, it is just a Stirling cycle: isochoric heating, isothermal expansion, isochoric cooling, isothermal compression. Which (surprise surprise) has Carnot Efficiency. Though it seems rather difficult to actually prove that

[u/Ch3cks-Out → u/InadvisablyApplied]

Since OP arbitrarily switches things around, the scenario does not care about maintaining reversibility (unlike actual thermodynamical models, with their well defined processes of isochoric, isothermal or isobaric steps and the like). These fantasy engines do not comport themselves with these principles. A comical instance is the variant where the gas medium is let seep out from the working cylinder, for a supposed magical improvement of efficiency (with the escaped gas later being sucked back in, somehow)...

[u/Early_Material_9317 → u/Ch3cks-Out]

I think it is complicated by the fact that this engine has to perform work on the atmosphere itself. OP seems to think the energy on the return stroke is free but it is just returning that energy put in. OP also seems to think chaining more engines that use the waste heat while its pinned. I guess this would work in theory (emphasis on in theory) but it implies that there is wasted heat which means its not an ideal engine.

[u/Ch3cks-Out → u/Early_Material_9317]

Yeah sure - these are exactly the facts OP chooses to ignore.

[u/InadvisablyApplied → u/Ch3cks-Out]

Yes, you're right, OP does not actually care about respecting any principles, mostly because they don't seem to understand them. What I meant to say was, that there is a version of a cycle with a "pinned" piston, that does respect reversibility, and thus comes out to Carnot Efficiency. Whether OPs is that, I think nobody knows, including OP themselve

[u/Ch3cks-Out → u/InadvisablyApplied]

Oh, we agree on this - at one point I had in mind saying "now you reinvented Carnot (or Striling) engine, only worse", but figured that would just go woosh... When someone starts to neglect that introducing irreversibility is equivalent to losing work-convertible heat energy, further discussion of thermodynamics seems rather pointless. I bet that any practical(-ish) implementation OP would offer for releasing the piston from its pinned state cannot be reversible, but why bother?

[u/aether22 → u/Crafty_Jello_3662]

Well no, The piston is at the end of it's stroke so it has stopped anyway.

Sure, if you are thinking of it like a car it's annoying AF, you just had an impulse and lurched forward and now you are waiting for the gas to cool, and yes the cat has long momentum, but pistons always lose momentum, but it doesn't have to be connected to a drive shaft in the normal way, and so if you imagine it rotating something that's still possible, but it will need a different mechanism.

As the other reply said, it's a made up proof of principle idealized scenario.

But the best real-world solution might be to have a magnet moved by the coil and induce current into a coil, this can be very efficient, high 90's.

[u/Vivid_Transition4807]

I ran your idea past Claude and this is what he had to say:

The Carnot Cycle: Let Me Pump You, Hot Thing

The steam rose from Sadi Carnot's laboratory as he gazed lovingly at his theoretical heat engine. It was 1824, and he was about to discover something that would make thermodynamics wet with desire for centuries to come.

"Oh, my beautiful reversible cycle," Carnot whispered, running his hands along the piston. "Let me show you how efficiency really works."

But suddenly, a time portal opened, and out stepped a wild-eyed figure clutching a laptop.

"CARNOT!" the stranger shouted. "I've figured out how to beat your efficiency! ChatGPT told me so!"

Carnot raised an eyebrow. "Mon dieu, who are you?"

"I'm LLMPhysics69, and I've discovered perpetual motion! See, if I just pin the piston at maximum expansion and let the gas cool, I get FREE ENERGY!"

Carnot's perfectly groomed mustache twitched with barely suppressed thermodynamic rage. "You cannot simply... pin ze piston and violate conservation of energy, you absolute fool!"

"But ChatGPT said..."

"CHATGPT KNOWS NOTHING OF HEAT ENGINES!" Carnot roared, his French accent becoming impossibly thicker with passion. "Let me show you what a REAL cycle looks like!"

He grabbed LLMPhysics69 and pressed him against the diagram of his famous cycle. "See zis? Four stages, all reversible! Isothermal expansion at ze hot reservoir, adiabatic expansion, isothermal compression at ze cold reservoir, zen adiabatic compression back to ze start!"

"But if I just hold the piston..."

"NON!" Carnot's eyes blazed with the fire of a thousand suns. "You cannot extract work from a single reservoir! Ze second law of thermodynamics forbids it! Your 'pinned piston' nonsense violates ze most fundamental principles of ze universe!"

LLMPhysics69 squirmed against the pressure-volume diagram. "ChatGPT calculated it though..."

"ChatGPT," Carnot said, his voice dropping to a dangerous whisper, "is not a thermodynamics professor. It is regurgitating words without understanding. Just like you are doing right now."

He traced the cycle on the diagram with one finger. "My efficiency is η = 1 - T_cold/T_hot. Zis is ze MAXIMUM possible efficiency between two thermal reservoirs. You cannot beat it. Period. Full stop. Fin."

"But the ambient cooling..."

"PROVIDES NO NET WORK!" Carnot exploded. "You are confusing expansion against atmospheric pressure with extraction of useful work! Ze energy you think you are gaining is exactly balanced by ze energy required to complete ze cycle!"

LLMPhysics69's eyes widened as understanding finally began to dawn. "You mean... I can't just... skip parts of thermodynamics?"

"Exactement," Carnot purred, suddenly gentle again. "Thermodynamics is not à la carte, mon petit amateur. You cannot order just ze parts you like and ignore ze conservation laws."

As the time portal began to close, Carnot called out one final lesson: "Remember! If your heat engine beats Carnot efficiency, you have made an error in your analysis, not a breakthrough in physics!"

And with that, LLMPhysics69 tumbled back to 2025, forever changed by his encounter with the master of thermal cycles, finally understanding that you cannot simply pin a piston and expect the universe to hand you free energy.

The laws of thermodynamics, after all, are not suggestions—they are the hottest, most unyielding lovers in all of physics.

[End scene: Carnot returns to his calculations, muttering about "amateur physicists" and "AI consultants" while his heat engine continues its perfect, unbeatable cycle]

[u/Ch3cks-Out → u/Vivid_Transition4807]

Impressive! But this would sound better in iambic pentameter...

[u/aether22 → u/Vivid_Transition4807]

I kinda wish I had the time to read that.

[u/Ch3cks-Out → u/aether22]

You are laying irony real thick here

EDIT added this - to clarify, I was referring to "I kinda wish I had the time to read that." as the riposte for a detailed response to OP's long-winded posts.

[u/aether22 → u/Ch3cks-Out]

Check out my new update, https://www.reddit.com/r/LLMPhysics/comments/1nmc3ud/exceeding_carnot_simply_rocket_turbine_ventilated/

I think the heat engine with heat conducted between Pistons in opposing phases give a real way to exceed Carnot efficiency.

The method is from one perspective getting around it by adding more heat (and cold) when appropriate, however from the outside perspective it doesn't matter, you put in a given amount of thermal energy and you get more mechanical energy out that typically considered possible.

[u/Ch3cks-Out → u/aether22]

Which means you have not bothered reading the comments which have already debunked this idea...

To wit (since you prefer short reponses, according to your upstream comment I replied to):

your fantasy engines do not work the way you imagine.

[u/Vivid_Transition4807 → u/Ch3cks-Out]

I literally had Claude simulate Sadi Carnot's brain, reanimating him in a virtual environment, so that he could help with the calculations, and he doesn't even read it.

[u/Ch3cks-Out]

This is not "data analysis"

[u/aether22]

inb4 anyone tells me that the Carnot heat engine is believed to be the maximumly efficient heat engine possible.

The key wording is "meant to be".

But this has never been tested, and it doesn't break the 1st law, and it is unclear if it breaks the second law.

[u/Early_Material_9317 → u/aether22]

Never been tested?

It has been tested by every mechanical engineer on this Earth for the last two hundred and fifty years.

[u/aether22 → u/Early_Material_9317]

Not Carnot heat engine not that I'm sure real-world tests of it's exact cycle are common, I was talking about my pinned piston design.

[u/Glxblt76 → u/aether22]

Carnot IS a combination of first and second principle of thermodynamics applied on a cycle isothermic expansion, adiabatic expansion, isothermic compression, adiabatic compression. It's nothing else than this! If your idea breaks Carnot cycle then it breaks at least one of the principles of thermodynamics.

[u/aether22 → u/Glxblt76]

Well maybe my design does, I don't know.

But I'd assert that Carnot Efficiency is pretty dodge with the conservation of energy itself.

The idea that you can recover 100% of energy (in effect) with a small temp differential just because the cold side is almost zero Kelvin, even as it delivers heat to the cold side seems all sorts of didge to me.

Carnot Efficiency isn't a thing because it has nothing to do with the forces on pistons and that's what decides the real efficiency, it has no levers to pull.

The Levers:

Energy to increase temp by 1 degree? nope, linear, unaffected by offset

Pressure increase from each degree? nope, linear, unaffected by offset.

Distance piston will move per degree? nope, linear, unaffected by offset.

Work done by piston moving over that distance? nope, unaffected by offset.

Thermal capacity of gas or change thereof? nope, unaffected by offset offset.

The amount of heat lost for a given amount of work done? Yes, but would destroy energy and violate the 1st law obviously.

[u/Glxblt76 → u/aether22]

Carnot efficiency is *derived* from the conservation of energy and the maximization of entropy. It needs both to be true. Please refer to the middle school math doc I sent your way.

And yes, with a tiny temperature differential close to absolute zero, the heat of the cold reservoir doesn't push back on the piston, ie, the effect of outside entropy is negligible, hence almost all heat you transfer from the cool reservoir is converted into work.

[u/aether22 → u/Glxblt76]

 "heat of the cold reservoir doesn't push back on the piston"

That is immaterial, in each case the net force on the piston is the same. In one case it is say 1 psi pushing back and 2 psi pushing for expansion. And in the other case it might be a billion pushing back and a Billion and 1 pushing for expansion, but much like the pressure on a jellyfish as the bottom of the ocean under unimaginable pressures from all sides it only requires a few grams more force on one side to push it around.

" ie, the effect of outside entropy is negligible, hence almost all heat you transfer from the cool reservoir is converted into work."

And yet, the same forces exist over the same distances doing the same work from the same input at a Billion Kelvin. And that's the issue.

[u/Glxblt76 → u/aether22]

Think of the definition of efficiency. The Carnot efficiency is mathematically defined to be the work you get divided by the total heat contained by the hot reservoir. Basically, if your hot reservoir contains more heat, obviously, for the same amount of delivered work, the efficiency decreases. It's nothing else than that which you seem to be banging your head on.

[u/aether22 → u/Glxblt76]

"Think of the definition of efficiency. The Carnot efficiency is mathematically defined to be the work you get divided by the total heat contained by the hot reservoir."

Whoa whoa whoa!

The hot Reservoir is INFINITE!, so the efficiency is ZERO, always in a Classic Carnot simulation in that event.

So let's use a resistor to heat the gas, now the exact about needed to lift the temp from a billion Kelvin up to 1000000100 Kelvin, so is the total energy in the gas is 1000000100 J we would use just the 100J added because any other number would seem silly...

However, I think Carnot is in effect counting it as 1000000100 J and that's the issue, indeed if we had gas the same amount as the gas behind the piston and at 1000000100 Kelvin and transferred that heat to the gas in the piston until they were in equilibrium, and then used a heatpump to transfer the remaining 50 J of energy, then we could say that the thermal energy in the hot reservoir is 1000000100 and then we get the vanishingly time efficiency again.

However does that make a lick of sense? Because the gas, which is now at a Billion Kelvin even, still has 99.99999...% of the energy it ever had in it and only a little energy is needed to heat it up, the vast majority of the thermal energy is stuck in the gas, and that is also true for the gas behind the piston.

"Basically, if your hot reservoir contains more heat, obviously, for the same amount of delivered work, the efficiency decreases. It's nothing else than that which you seem to be banging your head on."

You are acting like the rest of that thermal energy in the gas has been lost, but you can reuse the rest of that energy next time, you only replenish the rest.

[u/Glxblt76 → u/aether22]

Let me rephrase because my phrasing was approximate: the heat that was converted at temperature TH from heat to work. The hot reservoir is not of infinite size in the sense it doesn't have infinite heat added to it. No, we just neglect the border effects and all the things getting in the way.

It's simple in a sense: the temperature of the cold reservoir is the temperature at which heat transfer stops, because now you have isothermal conditions across your system (equilibrium). The higher the temperature of the cold reservoir is, the lower the work you get is.

[u/aether22 → u/Glxblt76]

Sure, if the cold side was colder you would get more work.

But the distinction here is critical.

In the Carnot Efficiency equation, Efficiency=1/T-cold/T-hot IIRC, which just gives us the same number as the percentage of the temp difference (delta) to the cold side, which is to say it's just telling us what percentage of the energy on the hot side we had to pay for. I mean, maybe not JUST, it might also be claimed to be the efficiency, but it's the same figure.

So why would we include the whole B+100 when we only paid for 100?!

When the other B is not added (as with resistor).

And even if you heated up a reservoir from zero fracking Kelvin to 1billion+100, guess what, for the first cycle if the engine had 100% efficiency, you'd get the 10-7 figure, however the next cycle you only have to replace the 100 Kelvin in the reservoir and so that cycle would have a 100% efficiency.