Is Carnot efficiency valid?

[studiot]

1 hour ago, Tom Booth said:

You seem to have all your ducks in a row ready to post an entire treatise on the subject from start to finish, that is neither appropriate nor necessary. If you want to play the headmaster of your own thermodynamics course I would suggest you start your own thread on the subject. The focus here is very narrow: Is the so-called Carnot efficiency formula valid or applicable to a Stirling engine, and is it falsifiable: can it be tested experimentally.

 

Quite Frankly, Tom, there are plenty of other members that are more rewarding to talk to than you are so my focus of attention has shifted away from yourself.

[Tom Booth]

1 minute ago, studiot said:

 

Quite Frankly, Tom, there are plenty of other members that are more rewarding to talk to than you are so my focus of attention has shifted away from yourself.

That's fine, but this is not the lounge room for idle chatter or endless off topic banter, or a treatise on the Studiot theory of thermodynamics, or the Tom Booth theory for that matter.

As far as I'm concerned the thread can wander where it will, but just please stop whining if I fail to respond to posts irrelevant to the topic I'm interested in focusing on.

21 hours ago, studiot said:

@Tom Booth  you might like to reflect on why neither heat nor work can be considered to be properties.

Relevance?

Is that my "thought for the day" or what's your point exactly?

[Ghideon]

One reason for me to ask questions and try to get into the details about your hypotheses and your possible explanations is to find possible improvements in the experiments. For instance if ice was crucial to the experiment I would suggest various ways to get repetitive results from that. If low temperature is the thing that actually is required I intuitively try to simplify how to cool the things instead of how to manage the ice. And maybe if the problem is to get the engines staring when cold side is at ambient temperature that can be managed as well.

It all serves to remove variable things that others could have problems to repeat or that may be tricky to reproduce in your setup. None of these requires an explanation of the result before running the experiment but it helps to create a setup that have fewer sources of errors while at the same time does not introduce bias regarding the hypothesis. 

 

7 hours ago, Tom Booth said:

Your point?

Why do you have to ask; isn't it obvious since you know thermodynamics?

(And I will not try to explain; you asked me not to:)

7 hours ago, Tom Booth said:

BTW, I appreciate the concern, but generally speaking people can stop trying to teach me about fundamental thermodynamics.

 

Edited February 6, 2023 by Ghideon
spelling

[Tom Booth]

On 2/4/2023 at 2:29 PM, swansont said:

On 2/4/2023 at 12:26 PM, Tom Booth said:

It certainly appears that the increased ∆T results in increased efficiency.

That’s the only variable that changed. And work increased from zero to some nonzero value, so there is no arguing about the increase in efficiency

It's not "the only" variable that changed. Room for expansion work has increased also as a result.

It may be that this increased contraction/expansion space accounts for better engine performance (performance of more expansion work) rather than a more rapid or voluminous "flow" of a  magical  caloric/heat to the non-existent  "cold reservoir".

The problem in running tests has been the probable inadequacy of insulation and the insulation acting as a heat conductor rather than an impediment.

That's why I'm rather excited about Ghideons suggestion. It has the potential for virtually, if not entirely eliminating a wild variable.

 

[joigus]

On 2/4/2023 at 6:26 PM, Tom Booth said:

It certainly appears that the increased ∆T results in increased efficiency.

 

It not only "appears to." It does. And Carnot's formula tells you why. So much more so the closest your design is to Carnot's unattainable chimaera.

Heat pump, or refrigerator have different definitions for efficiency, as efficiency is after all, an anthropocentric definition, as shown by the fact that for refrigerators and heat pumps --if I remember correctly--, work, instead of heat source, is what you put in, and thereby appears in the denominator. This, so I understood, was hinted at by Seth in a previous post.

[Tom Booth]

1 hour ago, joigus said:

It not only "appears to." It does. And Carnot's formula tells you why. So much more so the closest your design is to Carnot's unattainable chimaera.

Heat pump, or refrigerator have different definitions for efficiency, as efficiency is after all, an anthropocentric definition, as shown by the fact that for refrigerators and heat pumps --if I remember correctly--, work, instead of heat source, is what you put in, and thereby appears in the denominator. This, so I understood, was hinted at by Seth in a previous post.

Did you read my later full response?

There is no debate about the increase in efficiency but rather what the actual cause might be.

The cold applied is the primary cause, but I'm suggesting that there might be a secondary cause that explains the increased efficiency without resorting to the heat "flow through to the sink" (or cold reservoir) concept.

The cold might just provide more "bounce space" for expansion work.

I mean, if I might make an appeal to logic, and common sense, if heat is the fuel for a heat engine how does dumping additional "fuel" to a now colder sink improve performance?

In a Stirling or other "pure" heat engine the heat is a consumable; an actual fuel for the engine. One that "disappears" with no residual "waste" product.

Edited February 6, 2023 by Tom Booth

[sethoflagos]

3 hours ago, Tom Booth said:

If you do not want to read or respond to posts in an intelligent and constructive way, or make some contribution towards the objectives proposed, why not go waste your time elsewhere and bother someone else with your inanities.

You pretty obviously know absolutely nothing about how a real Stirling engine operates, but if you are going to mislead people I do feel it is within my place here to point out the errors and inaccuracies in your statements as compared with reality.

What you posted about the Stirling engine cycle bears no resemblance to either Robert Stirling's original invention or any subsequent models or modifications.

Compression of the working fluid results in heat not cold. It's elementary thermodynamics.

Yet those best placed to make a fortune if there were any merit to your ideas decided that you were unemployable.

And judging by the way you persistently misrepresent what I and others have actually posted here, perhaps they were having issues with your honesty too.

Edited February 6, 2023 by sethoflagos

[exchemist]

3 hours ago, Tom Booth said:

LOL...

You equate physical LAW with traffic rules and regulations? You really are in sorry shape. In need of a dose of reality, lost in idealizations and abstractions. If the book says, it must be true.

Yes you do need to run the traffic light if someone is alleging it's actually IMPOSSIBLE! if you are going to test the claim. 

Ah, but the trouble is that, in your mounting hysteria, you are not reading what I posted.

All I said was that if an engine were, somehow, to achieve a greater efficiency than the limit predicted by the Carnot formula, then it would break one of the laws of thermodynamics.  That is a true statement that requires no testing, as it is just a matter of applying the 2nd law of thermodynamics to Carnot's cycle, i.e. simply an exercise in theory.      

[Tom Booth]

3 minutes ago, exchemist said:

Ah, but the trouble is that, in your mounting hysteria, you are not reading what I posted.

All I said was that if an engine were, somehow, to achieve a greater efficiency than the limit predicted by the Carnot formula, then it would break one of the laws of thermodynamics.  That is a true statement that requires no testing, as it is just a matter of applying the 2nd law of thermodynamics to Carnot's cycle, i.e. simply an exercise in theory.      

A theory is just a theory. To establish it as a reality requires testing in reality, not another "exercise in theory".

[joigus]

22 minutes ago, Tom Booth said:

The cold applied is the primary cause, but I'm suggesting that there might be a secondary cause that explains the increased efficiency without resorting to the heat "flow through to the sink" (or cold reservoir) concept.

Have you read my previous comments? Irreversible work is, to all intents and purposes, indistinguishible from heat in any caloric analyses a couple of seconds after it's been delivered. It's not stored in the form of gravitational potential energy, charge in a capacitor, pressure in a gas, etc. All forms of work that can be 'given back' by the system. It must be included, as @sethoflagos shrewdly pointed out if I understood him correctly, as TdS=T(dS_{irreversible work}+dS_{heat exchange}) to the effects of every conceivable energy balance. If you take Carnot's efficiency formulae --any of them; heat engine, heat pump, refrigerator or José Carreras ("the other one"), irreversible work should be considered as heat, rather than work, as every Carnot recipe only speak of 'work' in the sense of 'reversible work,' not what you bluntly are calling 'work.'

This is, of course, just an educated guess by yours truly, as I've never been brave enough to try to tell anything about an ungodly mess of pumps and fans, and Stirlings, and so on as concerns Carnot's analysis. I wouldn't even know how to begin. Does this go in the denominator? You know...

As you're not distinguishing with any care the difference between irreversible and reversible work, and not taking any calorimetric measures, it's like trying to describe a platypus to a person that's willingly blindfolded and keeps telling you such thing cannot exist.

It all sounds to me like 'sumfin fishy's goin' on, there ain't no platypus."

I'm incapable of following your train of thought. There you are. I hope that clarifies the question as to why I can't clarify the question.

[Tom Booth]

21 minutes ago, sethoflagos said:

Yet those best placed to make a fortune if there were any merit to your ideas decided that you were unemployable.

And judging by the way you persistently misrepresent what I and others have actually posted here, perhaps they were having issues with your honesty too.

As far as any potential employment, I have no idea what your talking about.

How do you feel you were misrepresented?

4 minutes ago, joigus said:

Have you read my previous comments? Irreversible work is, to all intents and purposes, indistinguishable from heat in any caloric analyses a couple of seconds after it's been delivered. It's not stored in the form of gravitational potential energy, charge in a capacitor, pressure in a gas, etc. All forms of work that can be 'given back' by the system. It must be included, as @sethoflagos shrewdly pointed out if I understood him correctly, as TdS=T(dS_{irreversible work}+dS_{heat exchange}) to the effects of every conceivable energy balance. If you take Carnot's efficiency formulae --any of them; heat engine, heat pump, refrigerator or José Carreras ("the other one"), irreversible work should be considered as heat, rather than work, as every Carnot recipe only speak of 'work' in the sense of 'reversible work,' not what you bluntly are calling 'work.'

This is, of course, just an educated guess by yours truly, as I've never been brave enough to try to tell anything about an ungodly mess of pumps and fans, and Stirlings, and so on as concerns Carnot's analysis. I wouldn't even know how to begin. Does this go in the denominator? You know...

As you're not distinguishing with any care the difference between irreversible and reversible work, and not taking any calorimetric measures, it's like trying to describe a platypus to a person that's willingly blindfolded and keeps telling you such thing cannot exist.

It all sounds to me like 'sumfin fishy's goin' on, there ain't no platypus."

I'm incapable of following your train of thought. There you are. I hope that clarifies the question as to why I can't clarify the question.

Hmmm...

Work output counts for nothing?

If my Stirling engine drives a generator that lights up a village, powers machinery etc. We should recon that "irreversible" work output as waste heat?

Well that solves the problem I guess. Every work output will resolve back into heat eventually. Lightbulbs, toasters, radiant heaters, cloths dryers, microwave ovens etc. all produce heat. So we can subtract all that from the efficiency. That should balance things out nicely.

 

[swansont]

2 hours ago, Tom Booth said:

It's not "the only" variable that changed. Room for expansion work has increased also as a result.

Room for expansion work, whatever you mean by that, is not a variable. The capacity for work increased, since it was zero and then it had some value.

2 hours ago, Tom Booth said:

It may be that this increased contraction/expansion space accounts for better engine performance (performance of more expansion work) rather than a more rapid or voluminous "flow" of a  magical  caloric/heat to the non-existent  "cold reservoir".

Who said anything about caloric? 

There’s more heat flow. Curious that it depends on the temperature difference.

If there’s no heat flow, then the ice shouldn’t melt because of the hot water. Are you willing to make that argument?

2 hours ago, Tom Booth said:

The problem in running tests has been the probable inadequacy of insulation and the insulation acting as a heat conductor rather than an impediment.

I’d say it’s running the wrong tests.

You’re not running the tests that would falsify your conjecture.

 

[joigus]

40 minutes ago, Tom Booth said:

Work output counts for nothing?

 

Not exactly... Sorry I wasn't very careful.

There are further comments I'd like to make. It's all to do with efficiency actually being based a man-centred definition as roughly \( \eta=\frac{\textrm{output}}{\textrm{input}} \). If your input is pure 'work' --like in a refrigerator, electrical work--, you really don't care that much whether it's reversible or irreversible. It goes in the denominator of any reasonable definition of efficiency. If it's part of the 'internal definition of the cycles, it must always be reversible (meaning a form of energy that's stored in your system and can be given back.) If your output is pure work, it doesn't matter much whether it's reversible or irreversible either. It goes in the numerator in any reasonable definition of efficiency. After all, you don't care that much that your fan's energy, after it's hit your face and cooled it, gets lost in the air. It't important, though, to keep track of where it goes.

Internal work, the work that's invested in making the engine cycle on, that one must be reversible. I'm finding difficult to distinguish what kind of engine this is, and so what efficiency formula has to be applied.

If there are internal pieces of irreversible work/heat throughput, it could be a nightmare to analise in terms of Carnot's logic.

@Ghideon perhaps has been able to understand you better. He certainly has tried harder than anybody to follow your logic.

I'm trying to guess as I go, and draw some diagrams to clarify my own ideas and remember everything that could be involved or be relevant. And read everything that's been said.

I wouldn't dream of proving Carnot wrong though. Carnot's reasoning is what it is. And it's so simple and incontrovertible that I can see no way how it could be wrong.

Edited February 6, 2023 by joigus
minor correction

[Tom Booth]

4 minutes ago, swansont said:

Room for expansion work, whatever you mean by that, is not a variable.

How it that not a variable?

I explained briefly what I mean already, but to elaborate: There is a ceiling and a floor. Obviously if you make something colder and it contracts, lowering the floor, creating more distance between the floor (maximum contraction) and ceiling (maximum expansion) you have provided more room for expansion, which is the actual source of power output (conversion of heat into work).

I could elaborate further if you still don't get it but that might involve posting some video.

[joigus]

6 minutes ago, joigus said:

I wouldn't dream of proving Carnot wrong though. Carnot's reasoning is what it is. And it's so simple and incontrovertible that I can see no way how it could be wrong.

Also, as pointed out above, no experimental exception to it has been found.

[Tom Booth]

15 minutes ago, swansont said:

Who said anything about caloric? 

I surmise it to be the basic unconscious assumption behind concepts such as heat "flow", "reservoir", etc. Use of such phraseology conjures up images of a fluid flow.

[swansont]

6 minutes ago, Tom Booth said:

How it that not a variable?

It’s not an independent variable. Not a state variable that, in principle, can be directly controlled in an experiment.

5 minutes ago, Tom Booth said:

I surmise it to be the basic unconscious assumption behind concepts such as heat "flow", "reservoir", etc. Use of such phraseology conjures up images of a fluid flow.

Speak for yourself. You’re the only one who brings it up. Everyone else has shown they understand heat to be exactly as defined: energy being transferred owing to a temperature difference. Something that you’ve shown no indication of measuring, or any interest in measuring, even though it’s at the crux of the matter.

16 minutes ago, Tom Booth said:

explained briefly what I mean already, but to elaborate: There is a ceiling and a floor. Obviously if you make something colder and it contracts, lowering the floor, creating more distance between the floor (maximum contraction) and ceiling (maximum expansion) you have provided more room for expansion, which is the actual source of power output (conversion of heat into work).

How does the system “know” about this floor if no heat flows to it?

[Tom Booth]

22 minutes ago, swansont said:

If there’s no heat flow, then the ice shouldn’t melt because of the hot water. Are you willing to make that argument?

If the ice could be completely isolated from the surrounding ambient heat so that any heat reaching the ice MUST pass through the engines working fluid That would certainly simplify measurements. That is the point of Ghideon's excellent suggestion (or "rhetorical question").

Heat flow via the heat engine to the ice if present could be more easily determined.

Of course 100% elimination of all avenues of heat transfer other than the working fluid inside the engine is probably unrealizable. There must of course be an engine body of some sort which might conduct some small amount of heat etc. But such unwanted transfers could much more easily be reduced to an absolute minimum with the engines sharing the "sink" between themselves, literally between the engines. The heat would then have to be transfered through one engine or the other in order to reach the ice. This eliminated the issue about the potential conductivity of the insulation. There wouldn't:t be any.

I would be willing to say that at a minimum, with the two engine arrangement Ghideon proposed, the ice should melt eventually, but MUCH much much more slowly.

If there is heat transfer, than 2 engines both transferring heat to the ice simultaneously would double the heat input and the ice should melt much more rapidly, relative with some control.

For the ice to NEVER melt would mean there must be some heat transfer in the opposite direction out of the ice rather than into it. I do not rule out that possibility, as, as I've said before, I've seen some evidence that the Stirling engine behaves similarly to a Vuilleumier machine, pulling heat from both the hotter and the less hot ("cold") heat exchangers, (or top and bottom plates).

[Ghideon]

3 minutes ago, Tom Booth said:

If the ice could be completely isolated from the surrounding ambient heat so that any heat reaching the ice MUST pass through the engines working fluid That would certainly simplify measurements.

And without ice as a complicating factor? 

 

[Tom Booth]

53 minutes ago, swansont said:

I’d say it’s running the wrong tests.

You’re not running the tests that would falsify your conjecture.

My experiments have not been designed to test any speculations on my part. They have been designed to test the Carnot efficiency theorem as, for example, outlined in a previous post.

https://www.scienceforums.net/topic/128644-is-carnot-efficiency-valid/?do=findComment&comment=1228730

 

8 minutes ago, Ghideon said:

And without ice as a complicating factor? 

 

That would probably be preferable.

But some form of initial cold would be necessary.

There are a variety of ways of accomplishing that. Options have already been discussed.

[swansont]

8 minutes ago, Tom Booth said:

My experiments have not been designed to test any speculations on my part. They have been designed to test the Carnot efficiency theorem as, for example, outlined in a previous post.

As part if this you have speculated, rather strenuously, that you think that no heat is rejected in a heat engine. That all of the heat is converted to work. But you haven’t measured any of these energies.

[Tom Booth]

1 hour ago, swansont said:

It’s not an independent variable. Not a state variable that, in principle, can be directly controlled in an experiment.

So?

The ice (or other cold object) i.e. ∆T is an independent variable, the "bounce space" is one of the dependent variables under examination, if only theoretical at this point.

 

Time for me to take a break from this.

Sorry about any unanswered responses. I will get back to them.

Edited February 6, 2023 by Tom Booth

[swansont]

2 hours ago, Tom Booth said:

So?

The ice (or other cold object) i.e. ∆T is an independent variable, the "bounce space" is one of the dependent variables under examination, if only theoretical at this point.

So any change in behavior of the engine is a direct result of decreasing the temperature of the cold reservoir.

The ice melted, so obviously heat was flowing to it. What remains is determining if that happened just because of the ambient environment. I suggested an experiment to determine this.

 

[iNow]

2 hours ago, swansont said:

I suggested an experiment to determine this.

Yeah, but that was like 14 entire pages ago. Statute of limitations likely applies to evaded counterpoints. 

[Tom Booth]

9 hours ago, Ghideon said:

Why do you have to ask; isn't it obvious since you know thermodynamics?

(And I will not try to explain; you asked me not to:)

Did you read the clip from the video transcript I posted?

I've seen the video and dozens of others just like it.

Feel free to post what you want, you're my hero, but I started this thread on the Stirling Engine Forum in 2010:

 https://stirlingengineforum.com/viewtopic.php?f=1&t=478

The basic stuff the people in here keep trying to educate me on I was studying some time prior to that.

Is there something specifically you want me to get out of that video?

The second law? LOL

Here's another thread on the Physics forum you might find interesting, there was a "Studiot" there at the time trying to have that thread locked down as well.

https://www.physicsforums.com/threads/assumed-violation-of-physics-heat-vs-work.667129/

That was 2013

You should probably be able to find me on half a dozen other similar threads on all kinds of forums debating the 2nd so-called "LAW".

1 hour ago, iNow said:

Yeah, but that was like 14 entire pages ago. Statute of limitations likely applies to evaded counterpoints. 

Evaded by whom. Such experiments I've already uploaded years ago comparing ice melting under running vs. idle engines to see what difference it might make.

But I certainly have no objections to doing more/better experiments along those lines.

Petitioning against scientific inquiry, great platform there. I'm sure you've got everybody's vote!

4 hours ago, swansont said:

So any change in behavior of the engine is a direct result of decreasing the temperature of the cold reservoir.

The ice melted, so obviously heat was flowing to it. What remains is determining if that happened just because of the ambient environment. I suggested an experiment to determine this.

 

What's your suggestion for an experiment. I'm starting to like you better and better Swansont! Great idea! What are the details of your suggestion?