The Carnot efficiency problem

[stephenz]

Anyway that 99.62% number was based on stephenz's calculations:

viewtopic.php?f=1&t=5547&start=135#p19721

Why might this be significant?

Well, I've run engines under styrofoam, silica aerogel blankets etc. And I've been told repeatedly that these insulations are no better insulating material than air and so it makes no difference.

In this case the aluminium plate is not insulated by any potential conductive material that might carry heat away better than air.

Probably a water bath sink would generate more meaningful numbers as it has more heat capacity than aluminium and there is an accepted standard method for measuring joules of heat used to raise the temperature of water.

since the forum doesn't allow us to edit past a few minutes after posting I can't edit that post. the numbers are correct but based on your measurements which you admitted were wrong.

[VincentG]

"The difference between absorbed and rejected heat, becomes the heat that is converted to work."

That would mean the missing 83.68 joules/second of missing heat were converted into work.

That indicates an efficiency of 99.62%

Carnot efficiency given the ∆T is around about maybe 20%

So we have a discrepancy of around 80%

I know you are more intelligent than this Tom.

Most likely, only a small fraction of that heat is entering the engine, and after that the engine acts as an insulator itself, being a contained pocket of air with a foam block in the middle.

To make an accurate measurement of actual heat in vs. heat "rejected" would be very difficult.

[Tom Booth]

...
since the forum doesn't allow us to edit past a few minutes after posting I can't edit that post. the numbers are correct but based on your measurements which you admitted were wrong.

Why would you want to edit the post?

The numbers are correct? good.

The thermocouple readings were not wrong, that we know of, only the polarity.

I did a lot of research on thermocouples after my blunder, so I know what effect reversing the polarity had and why it had that effect. Here are a few references:

Thermocouples measure temperature differentials, not absolute temperatures. Two wires, each made from a different metal, are joined at the tip. This is the measuring junction. At the other end, the wires are connected to a body of a known temperature, called the reference junction. A thermocouple works by taking the difference in voltage between the two junctions, explained by the Seebeck effect

https://blog.wika.us/products/temperatu ... nt-errors/

Thermocouple Leads Reversed?
If the Leads on your thermocouple are reversed, the temperature measured will show to be varying in the opposite direction relative to ambient temperature.

https://www.temprel.com/learning/troubl ... ermocouple

Will reversing the polarity of a K thermocouple damage it?
Asked 1 year, 1 month
...
It won't be damaged.

A thermocouple is passive -- it generates a small voltage (millivolts) based on the temperature difference between its ends. The readout IC amplifies and compensates this voltage (which can be positive or negative depending on temperature) to provide a usable output.

Reversing it will generally mean that the temperature reading will be inverted (from 25 C) -- so a reversed thermocouple at 29 C will read 21 C etc.

https://electronics.stackexchange.com/q ... -damage-it

The ambient reference temperature was right. The thermocouple was not damaged by being reversed, only the direction of temperature change was reversed, so that a 1° rise in temperature was shown as a 1° fall in temperature. etc.

An efficiency of 99.62% is based on corrected results which is straightforward. The change in temperature per time interval was correct, only the direction of change was reversed.

I would, of course, not consider one suspect experiment conclusive and the experiment should certainly be repeated, many times and in many ways, but as yet, given the available data from that one experiment there is no reason to conclude that the 99.62% efficiency is inaccurate based only on the fact that the thermocouple lead polarity was reversed.

I am ordering a new set of leads asap so as to eliminate doubt but in the mean time this is the best readings we have and I don't see any reason to believe that the corrected numbers, taking the reversed polarity into account are "wrong".

[Tom Booth]

"The difference between absorbed and rejected heat, becomes the heat that is converted to work."

That would mean the missing 83.68 joules/second of missing heat were converted into work.

That indicates an efficiency of 99.62%

Carnot efficiency given the ∆T is around about maybe 20%

So we have a discrepancy of around 80%

I know you are more intelligent than this Tom.

Most likely, only a small fraction of that heat is entering the engine, and after that the engine acts as an insulator itself, being a contained pocket of air with a foam block in the middle.

To make an accurate measurement of actual heat in vs. heat "rejected" would be very difficult.

How much heat actually entered the engine is questionable, but I don't see any reason to conclude that it was necessarily a "small" or insignificant fraction.

The path from steam generator to engine was relatively short. The steam traveled up a PVC pipe fittings to a probably aluminium plate. The seales at the PVC pipe ends were good and though the water boiled continuously, no steam was escaping and the engine was not jumping or "burping" like a lid on a pot of boiling water. In other words, most of the steam was condensing and falling back down into the boiler. Certainly the heat entering the engine was some fraction of 85 joules/second from 0% to 100% beyond that is guesswork at the moment.

As far as the engine acting as an insulator once the heat is inside, IMO the heat either conducts through the engine body to no effect or it enters the working fluid causing it to expand and "do work" making the engine run.

The engine was running quite vigorously at about 400 RPM. Some unused portion of the heat was reaching the sink.

From what we know so far the percentage of heat reaching the sink was 0.38% of the 85 joules/second being generated at the boiler.

Probably not all of the remaining 99.62% was converted to work, but as I said, that is the starting point based on what information we have so far.

We can speculate based on our prejudices or we can do additional, hopefully better, more conclusive experiments.

To make an accurate measurement of actual heat in vs. heat "rejected" would be very difficult.

What's so difficult about it?

I hear this sort of thing all the time on the science forums, the throwing up of hands in frustration. Doing any real science is too difficult.

For example:

Heat experiments are always time consuming and finicky and then there is always some reason they need to be repeated (endlessly).

Reference: https://www.physicsforums.com/threads/s ... st-6372738

The problem as I see it is simply that the experimental results do not conform to what is anticipated.

An efficiency anywhere near 99.62% is simply considered inadmissable, unacceptable, a fluke, whatever.

Suddenly what everyone knows to be a heat insulator becomes a conductor, where heat might be going is a complete mystery and cannot possibly be tracked, traced or measured, all we can do is attribute the supposedly missing heat to "entropy". That magical mutable undefinable non-existent something conjured up to explain it all away.

Experiments are easy.

Changing fixed ideas about the nature of reality is next to impossible.

Like the first post earlier from "nobody":

An engine running without heat rejection would allow an over unity machine to be built. That violates the law of conservation of energy, and all of physics would be wrong. All...

I was reading some writings from Kelvin I believe some time back and it was about heat being converted into work being "destroyed" in the process rather than passing through.

He seemed to believe that a heat engine might actually run out of control and not stop until it had "destroyed" all the heat in the universe.

All I can say about that is his "universe" must have been rather small.

If it turns out that an LTD Stirling engine is 100% efficient, no, the stars are not going to fall from the sky.

[stephenz]

...
since the forum doesn't allow us to edit past a few minutes after posting I can't edit that post. the numbers are correct but based on your measurements which you admitted were wrong.

Why would you want to edit the post?

The numbers are correct? good.

The thermocouple readings were not wrong, that we know of, only the polarity.

I did a lot of research on thermocouples after my blunder, so I know what effect reversing the polarity had and why it had that effect. Here are a few references:

Because you are taking my quote out of context.
And why are you even arguing about this? You plugged in thermocouple wrong, you made a mistake, and as a consequence the temperatures you reported don't match the temperature you were trying to measure.

We knew something was wrong before you corrected yourself, I went as far as evidencing you should have seen both condensation and frost forming, which you also admitted never happened.



Then, days later you quote this post and use the numbers in there. Why? Q = M.Cp.Dt there you got the formula, use it but please keep me out of it.

[Tom Booth]

...
since the forum doesn't allow us to edit past a few minutes after posting I can't edit that post. the numbers are correct but based on your measurements which you admitted were wrong.

Why would you want to edit the post?

The numbers are correct? good.

The thermocouple readings were not wrong, that we know of, only the polarity.

I did a lot of research on thermocouples after my blunder, so I know what effect reversing the polarity had and why it had that effect. Here are a few references:

Because you are taking my quote out of context.

I don't think I have at all

My argument or "theory" is, and has been all along, that my observations and experiments of Stirling engines generally indicates to me that they "reject" a scant amount of heat to the sink, if any, that this appears to be contrary to the Carnot (so-called) efficiency formula predictions as currently taught and interpreted in academic circles, and that a typical Stirling engine is actually very near to having 100% thermal efficiency, more or less.

The experiment was intended to demonstrate some cooling effect, as seemed to be the case in previous experiments.

In previous experiments the heat source was hot water that had been boiled, not boiling water, but seeing indications of a fall in temperature I let the experiment run its course with the boiling water, though this was contrary to my own theories that to see a cooling effect would require careful "load balancing" to avoid overheating the engine.

As stated in my report here in the forum, after the experiment, I suspected something was wrong, as the apparent "below ambient cooling" seemed greater than anything I had seen previously.

I had checked the accuracy of the thermocouples several times in different ways, but had just plugged them back in before the start of the experiment. So I thought the thermocouples might have been plugged in backwards.

It's no different than if I set out on the highway and traveled several miles before realizing I was traveling East rather than West. Such a mistake does not invalidate the actual odometer readings.

You say "leave me out of it" and now seem to want to distance yourself from your own calculations, but you have asked several direct questions, so I'm answering.

And why are you even arguing about this?

That is your characterization. I'm not "arguing" at all. I was simply curious what the actual results of the experiment turned out to be. After verifying my mistake in reversing the polarity of the thermocouple and reading up on what effect this would have, my conclusion is that the error was not a fatal mistake and that my time otherwise wasted doing the experiment could be saved by correcting for the reversed polarity

This is easily done. Rather than a gradual drop in temperature below ambient, there was actually a gradual temperature rise above ambient.

The result is still a thermal efficiency very close to 100% either way. If there was an actual cooling effect we could call the engine a heat pump and the e > 1 the "COP" and nobody would complain.

You plugged in thermocouple wrong, you made a mistake, and as a consequence the temperatures you reported don't match the temperature you were trying to measure.

We knew something was wrong before you corrected yourself, I went as far as evidencing you should have seen both condensation and frost forming, which you also admitted never happened.

Obviously, with a temperature RISE above ambient there was no chance of any frost formation.

Then, days later you quote this post and use the numbers in there. Why? Q = M.Cp.Dt there you got the formula, use it but please keep me out of it.

Why use the numbers?

Why not?

This experiment using the thermocouples was at your prompting. I was content with the infrared thermometer readings, but you suggested a thermocouple would be more accurate.

You seem to wish that "YOUR" calculations should only be utilized to debunk my theory as stated above, which you apparently don't like and don't agree with, but want to forbid the use of the same calculations in an objective assessment that supports my theory.

Seems just a bit disingenuous to me.

You, me or anyone else reading the forum is free to check on the accuracy of the calculations and either agree or disagree and make corrections or adjustments or voice their opinions on the matter.

Mathematics is not at your exclusive disposal to use as ammunition against those you disagree with, as much as you seem to wish that were the case.

[stephenz]

The numbers I used were those shown on YOUR video, with the TC leads installed in reversed.
The meaning in those numbers disappeared the second you admitted making the ridiculous mistake of installing the plug wrong.
The thermocouple readings were wrong. End of story.
What else is there to add?

On this I will sign off this forum and take my studies some place else.

Good luck everyone, particularly to you Administrator.

[Tom Booth]

The numbers I used were those shown on YOUR video, with the TC leads installed in reversed.
The meaning in those numbers disappeared the second you admitted making the ridiculous mistake of installing the plug wrong.
The thermocouple readings were wrong. End of story.
What else is there to add?

On this I will sign off this forum and take my studies some place else.

Good luck everyone, particularly to you Administrator.

You volunteered to make your calculations and comment on my experiment without any prompting from me.

Now you want to restrict me from commenting on my own experiments, or responding on my own thread?

You are free to make a retraction or reassessment, but I don't agree to throwing out the baby with the bathwater.

I do agree the experiment should be done over but not that "The thermocouple readings were wrong. End of story."

It would be helpful if you could explain why the numbers (temperature change from ambient) are invalid when applied to a temperature rise rather than a temperature fall.

[matt brown]

Tom, how about some simple old world math where eff = output/input as in simply measure work out vs heat in ? No waterfall, tug o' war, or calculus req'd...

[Tom Booth]

Tom, how about some simple old world math where eff = output/input as in simply measure work out vs heat in ? No waterfall, tug o' war, or calculus req'd...

I think we've already discussed a number of perceived problems in doing that.

How to get a verifiably accurate measurement of heat "in" and work "out" being the main issue(s).

VincentG for example pointed out recently, in his estimation:

Most likely, only a small fraction of that heat is entering the engine, and after that the engine acts as an insulator itself, being a contained pocket of air with a foam block in the middle.

To make an accurate measurement of actual heat in vs. heat "rejected" would be very difficult.

How do you propose overcoming such objections?

Similar objections have been raised regarding the measurement of actual work output, or even how to define "output".

Also there seems to be some variation as far as what constitutes "work".

Some of the literature on the subject use the term "useful work", apparently making a distinction of some sort.

[matt brown]

How to get a verifiably accurate measurement of heat "in" and work "out" being the main issue(s).

As I said, the same way Road & Track would...simply measure heat supplied (fuel, electricity or whatever) and actual physical output (mini dyno or whatever). Everything else is optional: size, insulation, regen, whatever.

No worries whether Jupiter and Mars are aligned (or whatever).

[Tom Booth]

"heat supplied" could mean almost anything.

You could have a tanker full of gasoline and still have zero heat actually entering the working fluid of the engine. Straightforward but meaningless.

An LTD does little more than enough "work" to keep its flywheel turning. What is insignificant for a 500 hp gasoline engine (road and track) might be nearly the total work "output" of an LTD

Also the output of a (notoriously inefficient) mini-dyno is not the actual or potential work output of the engine itself.

[Tom Booth]

Your proposal is also side stepping or completely neglecting the primary question, or at least the most interesting and significant one IMO.

What is the actual heat transfer to the sink and is that really necessary as some kind of unavoidable "LAW".

[Tom Booth]

I would like to, and probably will, when I have the time, run a comparison using a Stirling engine freewheeling no-load, another engine running a mini-dynamo or whatever load, and see if this makes a measurable difference in the amount of heat "rejected" to a sink.

I still think that probably the best sink for measuring heat rejection would be a water bath covering the cold side, or all of the engine with an internal heating element.

Heat would be generated internally and could only be output as either mechanical work running the engine of as heat to the surrounding water bath.

Maybe something like my earlier proposal with the engine running in a vacuum chamber, but instead of that, run it in a fish bowl under water, at least the chamber containing the working fluid.

The flywheel, as the work output should, I think, be outside of above the water bath.

Resize_20230719_001006_6123.jpg (146.21 KiB) Viewed 8731 times

[Tom Booth]

A few typos I notice where I posted "of" instead of "or" due to my phone's tiny keyboard.

I do appreciate the input from stephenz as well as everyone.

As far as the calculations from my experiment. I don't know anything about the equation used but I trust that stephenz knows what he's talking about. It is only appropriate in using data to draw conclusions of any kind to reference the source of the data.

That source, stephenz in this case, is in no way responsible for any conclusions drawn by myself or others from a use, or miss use of that data.

stephenz thinks, apparently that the data should be thrown out. I disagree. We are all entitled to our own opinions and should be free to draw our own conclusions.

Perhaps stephenz feels, or felt implicated as supporting my "perpetual motion" theories or some such thing, for that I apologize, if that is the case.

In a court of law an "expert witness" is merely a source of reliable data, it is up to the jury to decide the case, and the "expert witness" may not necessarily agree with the conclusions drawn by the jury.

But I would argue, once the information is in the public forum it is out of the hands of the "expert witness".

It does not appear that anyone contests the numbers. stephenz confirmed this a second time, though being of the opinion that my error in reversing polarity nullifies everything.

At any rate, we have a new tool for evaluating future experiments.

Q = M.Cp.Dt

I have no clear idea what that represents but if it can help provide some answers I'll do some study on it and try to figure it out.

As I understand it, it has something to do with the mass and heat capacity of the aluminium cold plate?

Could it also be used in conjunction with a water bath as I have proposed above?

Unfortunately, whatever calculations I might come up with could be dismissed on the basis that I have no idea about the appropriate use and application of such an equation.

stephenz expertise could have been a valuable asset so I hope he's not serious about leaving.

I would like to know what happened to his earlier offer to run some more accurate and definitive experiments himself while claiming to have no stake in the outcome one way or the other.

The appearance I'm left with at this point is he originally "fudged" the numbers to make it appear that the apparent "cooling" was minimal.

Reversing the polarity of the thermocouples makes it then appear that the heat rejection is minimal.

We all have our biases, one way or the other, often unconscious. This is well recognized in science and why there is peer review.

That was really my main reason for bringing my experiments to the science and physics forums, for expert evaluation and correct any mistakes or oversights.

Not being able to go there, due to the moratorium on discussion of the topic of "perpetual motion" and/or "violations of the second law", it is nice to have some individuals with some scientific and/or mathematical expertise in these areas come here and I certainly welcome that.

Please prove me wrong so I can do something more productive with the rest of my life!

I've been trying to prove my theory wrong starting with the first time I placed some styrofoam insulation over the cold side of an engine, and it had an effect completely opposite to what might have been expected based on "established science".