Carnot efficiency does not apply to Stirling engines

[Tom Booth]

Do you think breaking the Carnot Limit is also a violation of the 2nd law of thermodynamics?

In the special case of two reservoirs, Tн and Tх, we take heat Q from the heater, do work A and transfer (Q-A) to the refrigerator. Clausius inequality:
Q/Tн - (Q-A)/Tх ≤ 0 , we transfer, rewrite: A/Q ≤ 1 - Tх/Tн = (Tн - Tх)/Tн

The problem with all that is it's based on Caloric (heat engine as a water wheel) theory where temperature is viewed as a measure of a fluid.

Let's say Th = 600 and Tc = 300 (you have TX but Tc seems more logical to me c=cold)

Relate that to a bottle of liquid.

300 is 1/2 a bottle
600 is a full bottle

Let's say you start with 300 (bottle half full) we add 300 joules of heat.

The bottle is now full. 600

To use "all the heat" and empty the bottle we will need to remove 600 joules.

This is, among other things inconsistent in terms of how heat is defined.

Today, in modern science heat is defined as a transfer of energy. 

So, we start out with 300. The bottle half full. We TRANSFER 300 joules to fill the bottle.

We start at equilibrium.

It is 300 degrees K both inside and outside the bottle (i.e. engine).
We supply 300 joules.

That raises the temperature to 600, which is 300 above ambient (equilibrium)

So now the lame brained thermodynamicists tell me In order to use "all the heat" I need to use and/or "reject" all 600 joules, (empty the bottle).

We did not TRANSFER 600 joules of "heat" into the bottle. 300 were already there, we only transfered 300 which added up to 600 total, but the 300 that was already present is not "heat" by definition. It was never transfered.

What kind of lunacy is it to say that if we supply(transfer) 300 joules into an engine we have to convert 600 of those added joules into work for 100% efficiency.

Or if we use all of the 300 joules supplied by converting those 300 joules into work output that is only 50% efficiency because we are "rejecting" the remaining 300 joules. (That are just sitting at equilibrium with the surroundings).

It's difficult for me to fathom how such utter irrational nonsense manages to perpetuate itself down through history in the form of a mathematical equation without anyone noticing its based on a complete fallacy.

Heat is not a fluid. A heat engine is not a water wheel. Temperature is not a measure of a volume of a fluid.

[Tom Booth]

Hey Tom, I followed you in here. I'm still on the fence about all this and still want to discuss both "sides" equally. Can't do that on the Stirling engine forum, bit of a one sided story now.
And fool's little victory post doesn't sit right with me.

Anyway, hope you don't mind. I'm here to participate in the discussion and want to try and find out things for myself. With every respect to your opinions and findings. Because intuitively your story adds up better than the official story.

My focus is pretty narrow at this point, and I'm not overly interested in much if any further discussion. From here on out, I'm primarily interested in the design and construction of various engines, Stirling and/or Nitinol, based on what I've learned or tentatively concluded based on previous experiments and observations.

Primarily, I think these facts have been fairly well demonstrated:

A Stirling heat engine does not necessarily need to transfer ANY of the input heat through the engine to a "cold reservoir'.

A Stirling engine probably does not operate by intercepting a "flow" of heat traveling "through" the working fluid like a river as imagined in the classical model at all, Rather a Stirling heat engine is or in every respect appears to be a "damped, driven oscillator". As such, the heat input needs to be introduced at a 90° offset to the reciprocating mass in order to maintain a harmonic (resonant) oscillation at maximum possible amplitude.

https://youtu.be/aZNnwQ8HJHU

IMO, this theory or view of how a Stirling type heat engine operates is outside the realm of classical heat engine theory.

At any rate, I'm generally aware of the goings on at the Stirling engine forum, so if you direct a question to me there on that forum I'm able to respond there, as well as here.

We can see how it goes, but I think you may find that this is not the forum for fence sitters or for long drawn out disputes or debates. At this point, for me, that would be an utter waste of time and energy and would delay further progress.


As I said, my focus is on Stirling type heat engines. Pretty clearly, I think, other types of heat engine, such as a 4 cycle internal combustion engine, are not "oscillators", but operate by brute force internal explosions.

A Stirling engine has no mass flow passing through to carry with it any "latent heat". So the classical formulas and equations, PV diagrams and so forth IMO simply do not apply to a Stirling engine.

Some back on the Stirling engine forum simply cannot step outside that old classical framework so where I'm going is simply incomprehensible.

Unfortunately the classical view has a stranglehold and IMO has been responsible for holding back development of the Stirling engine for over a century.

Time to move on.

[Jim Mac]

I think you may find that this is not the forum for fence sitters or for long drawn out disputes or debates. At this point, for me, that would be an utter waste of time and energy and would delay further progress.

Tom is correct on the above statement.  This is not the place for debates.   Tom is a moderator of his board here and has the authority to make the decision on how his topics are steered.  Including what posts get moderated. 

I look forward to following Tom's work and builds.  And any attempts to deter investigations go against the purpose of this site.

[Jack]

Fair enough. Maybe I used the wrong words.
I'm not looking to dispute or debate. Just talk about and try to understand.
I don't plan to stick to just talking either.

Because I wanted to understand I started reading a lot of old posts by Tom on a few forums. The more I read, the more I felt like the engine I'm planning to build is based on similar principles or ideas. And as far as I understand the Carnot limit, I think my idea might break it too.

[Tom Booth]

Fair enough. Maybe I used the wrong words.
I'm not looking to dispute or debate. Just talk about and try to understand.
I don't plan to stick to just talking either.

Because I wanted to understand I started reading a lot of old posts by Tom on a few forums. The more I read, the more I felt like the engine I'm planning to build is based on similar principles or ideas. And as far as I understand the Carnot limit, I think my idea might break it too.

IMO, the so-called "Carnot Limit" equation is spurious. It uses the Kelvin scale which did not exist when Carnot lived. I don't think Carnot himself would have endorsed it either, given his later "unpublished" journal musings.

So, without context, how is this sliding scale temperature ratio to be interpreted?

Personally I see at least two possibilities. But as the so-called "Carnot Limit" is currently interpreted by academia at large today, most engines in existence today,  Stirling engines in particular, already far exceed the Carnot Limit.

Take this passage for example:

"The same result can be obtained by measuring the waste heat of the engine. For example, if 200 joules is put into the engine, and observe 120 joules of waste heat, then 80 joules of work must have been done, giving 40% efficiency".

https://energyeducation.ca/encyclopedia/...efficiency

I'm pretty sure you can see where I'm going with this.

Our friend "fool" on the Stirling engine forum does not admit such an approach to be a legitimate metric for determining efficiency. That's his opinion.

Anyway, you are already a member here so why not just start a topic about your project. If you've been reading old forums I've frequented, you must already have your fill of my opinions.

[Tom Booth]

It is curious how my simple question regarding the actual origin and presumed verification of the Carnot efficiency limit equation ALWAYS, for ten years or so now, goes unanswered:

https://www.sciforums.com/threads/origin...th.166462/

These are, I think, legitimate questions are they not?

Origin and verification of e=(Th-Tc)/Th

Tom Booth
Registered Member
Saturday at 4:06 AM

Can anyone tell me where this formula originated and how it was verified? (With citations, please).

Thanks in advance

Tom

https://www.sciforums.com/threads/origin...th.166462/


Such a foundational scientific principle should have some known contextual origin and history. Some record of empirical verification and testing of some kind, like virtually all other accepted principles in science.

The actual textual origin would presumably include the context for how this temperature ratio was originally interpreted. Otherwise we have simply a temperature difference.

In what way was this temperature difference originally considered to be in any way related to engine efficiency? What was the original theory behind it? Who formulated this equation? Are there examples of how it was intended to be used by whomever actually originated it, and why is it attributed to Carnot?

It uses the Kelvin temperature scale which did not exist in Carnot's lifetime.

How was it verified that such a temperature ratio placed a hard limit on engine  efficiency in the way it is currently believed?

Why is such information not more readily available, if it exists at all?

I think these are valid questions, but whenever I make such an inquiry, all I seem to get is snide remarks and attacks on my character and personal motives.

Without answers to such basic questions, what is the actual value of such a formula as this, which by all appearances is nothing more or less than Carnot's Caloric theory based, heat as a waterfall theories, now known to have been erroneous and now considered obsolete.

If we are to keep this formula around, should it not at least be subject to some kind of modern standards of empirical validation?

I thought so.

So I did a few simple experiments to get some ideas about the quantity of "waste heat" being "rejected" through the cold side of my Stirling engines.

By the calculations of that formula the waste heat should be about 5 times more than the heat utilized to run the engine, or heat converted to mechanical motion.

Instead I found virtually none at all. Actually, at times the instrument readings indicated a temperature drop of a degree or two at the presumed "heat rejection" site, or cold (ambient) side of my engines.

This is all on video:

https://youtube.com/playlist?list=PLpx2I...0Ive2y-kHB

https://youtube.com/playlist?list=PLpx2I...Apy0xbvFzr

Could it be these are actually the only experiments that have ever been conducted in an effort to verify the Carnot efficiency limit "LAW"?