Stirlingengineforum.com

Regarding the latest round of discussions, any extra weight presented to the piston when the starting condition is only 14.7psi will no longer allow a doubling of volume.

The more weight, the more the expansion becomes closer to Cv. This, at the sweet spot, should minimize the amount of energy needed to lift a given amount of weight.

Thankfully, a running engine is a cyclical process so we don't need to worry about a practically sized piston moving 1 meter at a time. Instead, the stroke can be kept very short, close to Cv.

Stroller wrote: ↑Wed May 22, 2024 2:51 am Your anticipated response is why I gave you your thread back, obviously.
Kindly stay away from mine.
Thank you.

You claim your example, as a Stirling cycle, is "MORE relevant to thinking about DIY Stirling engines".

It bears no resemblance to a Stirling cycle of any kind, theoretical or practical, or even the expansion leg of the cycle alone. It does not represent any part of a functional Stirling cycle at all.

I think I understand VincentG's question, but maybe not, but I assumed his query addressed some phenomenon somewhere within the ballpark of Stirling engine operation, not some made up diabatic cycle you pulled out of your hat.

BTW, you wrote "a diabatic". I assume you mean in contrast to adiabatic.

I know an ideal isothermal expansion is not fully realizable in practice, but it is at least a theoretical "ideal" that actually applies to Stirling engines, useful for modeling and simplifying calculations.

Your example is just completely off the chart. Not in the ballpark, not in the game at all.

Like usual your just inserting values in an effort to make Stirling engines look useless and non-functional.

The only thing non-functional, however, is your example

VincentG wrote: ↑Wed May 22, 2024 4:15 am

Stroller wrote: ↑Tue May 21, 2024 5:24 am
It's the action of the expanding gas "consuming" energy that I am interested in. Is internal energy really reduced when the gas expands, other than by conduction losses to the surrounding colder surfaces of the engine. And if so, how exactly?
The internal energy of the entire expanding volume isn't reduced, but the internal energy per unit volume is, because the total internal energy of the gas is spread out more, into a bigger space.
....
This statement (bold) is, or would be, a violation of conservation of energy.

Your statement is basically that energy can GO OUT from the working fluid as WORK but all the energy is still in the working fluid but just spread out more.

That would double the total amount of energy.

Say 1000 joules gone out as "work" but the same 1000 joules still in the working fluid but just spread out in a greater volume.

So the original 1000 joules has split and turned into 2000, 1000 going out as "work" and 1000 remaining but just spread out in a larger volume.

This is exactly what I would like to focus on.

So, you do not share Strollers sentiment, that the discussion should be moved in order for him to exclude me from the discussion?

Sorry for interjecting, but Strollers, apparently, intentionally overly heat soaked and heat saturated example he tries to pass off as a "more relevant" Stirling cycle was just too egregious to let stand unchallenged.

If you prefer I can butt out. You are a good critical thinker and experimentalist. You're observations have revealed aspects of Stirling engines behavior I had overlooked, so I don't want to interfere with your inquiry.

I would prefer all parties engage in the discussion.

Stroller and Fool represent the more traditional, proven, mainstream science. Tom is certainly on the fringe, along with me perhaps, just looking for answers.

This;

https://physicstasks.eu/2179/work,-pres ... -expansion

Already cited and many other similar examples, online discussions regarding isothermal expansion and the conversion of heat into work seem applicable to your question.

At least from a theoretical and mathematical perspective.

Actual "proof", such as an experimental demonstration is a bit more challenging, but I think this is covered historically in Joules experiments and the general topic of the equivalency of heat and work.

I'm not sure what you have in mind in terms of "proof", but the topic has a long history involving many experiments and proofs.

This topic of heat conversion is hardly outside "traditional, proven, mainstream science".

Well Tom you said it yourself. If the answer to my question violates the laws of thermodynamics, then it is certainly outside of tradition.

VincentG wrote: ↑Wed May 22, 2024 7:46 am Well Tom you said it yourself. If the answer to my question violates the laws of thermodynamics, then it is certainly outside of tradition.

Well, I don't know how much more mainstream you can get than an AI Overview:




There is no issue when it comes to the first law of thermodynamics.

The second law, IMO has been abused and weaponized by vested interests in ways that make it inimical to the first law, for reasons outside the realm of objective science.

The way I would phrase this, assuming the heat is not in fact destroyed, by any other means than direct thermal transfer, is that the same heat energy, if it could be recycled at 100% efficiency, would produce its equal amount of work over and over again.

VincentG wrote: ↑Wed May 22, 2024 8:46 am The way I would phrase this, assuming the heat is not in fact destroyed, by any other means than direct thermal transfer, is that the same heat energy, if it could be recycled at 100% efficiency, would produce its equal amount of work over and over again.

If you were asking me, first of all, isothermal expansion with "100% heat conversion into work" is "ideal", that is, assuming "perfect insulation", zero friction, no sound, vibration, radiation or other loses.

Never going to happen.

Also WORK output that leaves "the system" is gone. Not recoverable.

Your statement: "assuming the heat is not in fact destroyed, by any other means than direct thermal transfer" is a false assumption. I would not consider conversion of heat to work "direct thermal transfer".

It's not direct. Very indirect. Heat > expansion > pressure > velocity > gears, belts, pulleys and finally useful work output. Maybe charging batteries, inverters, who knows, thrown in as well. Lots of conversions, lots of potential loses at every turn.

Heat converted into the motion of a spinning flywheel is no longer heat. Some of the motion of the flywheel might be converted back to heat to be recycled, but there would, in reality be loses to vibration, noise, unrecoverable friction loses, thermal radiation loses.

My issue is not that 100% conversion is possible. It never is.

My contention is that the Carnot limit has no basis. It is arbitrary and without foundation.

Maybe you could get 95% conversion of heat into work. (95% of the heat "destroyed" through conversion into work).

Carnot limit says, maybe 15%

Carnot limit says: 85% ACTUAL THERMAL LOSS. Heat "flowing" to the "cold reservoir", EXCLUDING all the noise, vibration, friction, radiation etc. that would bring that down to virtually nothing.

Just ridiculous.

Add 20,000 joules and 99% is gone to the "cold reservoir"

So no, you can't produce the work from heat over and over, not even once or twice.

In being converted to work, the heat is irrevocably "used up'. GONE.

If say, you ran a generator on a Stirling engine, to light light bulbs at night, that light that energy that started out as heat, goes out into outer space, radiated into the night sky. gone forever.

Tesla never proposed a closed system, or "perpetual motion".

The "ambient heat" converted to work could not be recycled. A new supply of ambient heat would have to be taken in as the heat was converted to work.

Ultimately that heat came from the sun.

Conversion to work is not "direct thermal transfer", and it is also not "reversible", and for the most part, cannot be "recycled".

It (energy,/heat) arrives from the sun. We get to use a little while it's here, then it continues on its way to the distant galaxies.

Conversion to work is not "direct thermal transfer", and it is also not "reversible", and for the most part, cannot be "recycled".

I am not suggesting perpetual motion. I am suggesting an improbable theoretical cycle where assuming no losses, by temperature degradation or mechanical, the same internal energy can be reused.

I still have not seen any evidence or sound theory that shows the internal energy is lowered upon expansion, by any other means than losses to thermal transfer to colder bodies.

The way Stroller explained it is exactly how I see it. The internal energy per unit volume goes down with expansion, but total energy remains unchanged until it must be dumped to a cold sink.

In this way, I am more realistically suggesting that a 100% efficient heat engine dumps 100% of the supplied heat energy to a sink at a degraded temperature.

Again, I go back to my very simple question of does the isolated room reach 0k if all the rocks are lifted. Any possible method can be used inside the room to lift the rocks. There are no limitations, let your imagination run wild.

VincentG wrote: ↑Wed May 22, 2024 6:11 pm ...

In this way, I am more realistically suggesting that a 100% efficient heat engine dumps 100% of the supplied heat energy to a sink at a degraded temperature.

...

Not in my opinion. That would be a violation of conservation of energy. 100% of the supplied heat going to work AND 100% of the heat going to the sink.

Say, 2000 joules heat in

2000 joules of work done

2000 joules of heat, "degraded" or otherwise to the sink.

How does 2000 joules split itself into 2000 + 2000 = 4000 joules ?

Creation of 2000 joules from nothing.

That, in essence is Caloric theory, that heat "flows through" the engine and back out like water without loss, just at a lower (degraded) temperature.

No heat is energy. It gets "used up' or "disappears".

The absence of heat is cold.

A Stirling engine refrigerates by converting heat into work.

Nothing left to be reused.

Anyway, contrary to what "fool" suggests, that I don't report my failed experiments, in actuality nearly all my experiments are failed experiments.

I started out thinking I would demonstrate that a heat engine would overheat and stall if the heat flow out of the engine was blocked by insulation.

That's what everybody said would happen.

That demonstration was a failure. The engine not only kept running but ran at a slightly higher RPM.

All my refinements failed as well. Better insulation, more insulation, non-heat conducting cold plate, measuring the temperature rise at the cold plate, etc. etc.

Failure after failure.

VincentG wrote: ↑Wed May 22, 2024 6:11 pm ...
Again, I go back to my very simple question of does the isolated room reach 0k if all the rocks are lifted....

Ignoring realities, such as air liquifies, then freezes, before reaching 0°K making such a scenario impossible, in principle, running a heat engine using the heat in the room to lift rocks would "use up" tbe heat, cooling down tbe room, so you end up witb a cold room full of suspended rocks.

When all the rocks are dropped and hit the floor the energy would be released back into the room.

Then I guess you could start over.

Probably a hundred reasons why that wouldn't actually work in practice, but theoretically, by converting heat into work, the heat is "consumed" so the room would get colder and colder.

August Peters ice machine comes to mind:

That final paragraph seems to involve a major mis-understanding on somebody's part (possibly mine) - it certainly seems to describe an 'over-unity' machine.

MikeB wrote: ↑Thu May 23, 2024 4:59 am That final paragraph seems to involve a major mis-understanding on somebody's part (possibly mine) - it certainly seems to describe an 'over-unity' machine.

There is a somewhat strange phenomenon relating to compressed air.

If you, say, use 10,000 joules of energy to compress air it will release 10,000 joules of "waste" heat.

But you still end up with a tank full of compressed air.

Further, when the compressed air is released it produces a cooling effect. Especially if released through an air motor or turbine to do work.

If you have a use for the "waste heat" and the cooling it seems like your getting a lot of work output for free, or the heating and cooling for free.

https://web.archive.org/web/20190704133 ... /solar.htm