Is Carnot efficiency valid?

[iNow]

49 minutes ago, Tom Booth said:

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

Hyperbolic much?

[Tom Booth]

12 minutes ago, iNow said:

Hyperbolic much?

You tell me.

He (Swansont) just made the suggestion now, not "14 pages ago", we don't even know the details of his proposal.

Unless you were joking of course.

[iNow]

I never joke in threads this productive. 

[Tom Booth]

12 hours ago, Ghideon said:

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.

You are able to adopt an idea with a "what if" attitude and think, what would we have to do to see if this is true or not. That's a great quality.

There is nothing special about ice. It's just a handy way to create a temperature differential on the cheap. I've got some in the freezer here in my kitchen so I use it, but pretty obviously I think, anything cold or hot (or both) will do to create a ∆T. You can go above or below ambient (or both).

I think the rate at which ice melts also makes a good gauge or measure for comparison testing.

Here's an example of some previous experiments along those lines:

https://www.physicsforums.com/threads/should-ice-take-longer-to-melt-when-used-to-run-a-heat-engine.991714/

There were also some posted in this forum, but that thread was locked:

But if I mention it I'll get banned again I suppose. Speaking of the 2nd law.

________

I've done experiments attempting to measure or determine the "flow" of heat "through" the engine in every way I could think of.

With heat applied, cold applied, ice, propane torch whatever.

One thing I haven't tried is the arangement you suggested. Two engines with the cold sides back to back. Brilliant idea!

The other way around might be interesting too. Sandwich the heat source between two engines. Makes measurement so much easier. The heat cannot dissipate to the surrounding ambient without going through one or the other of the engines. Very clean data should be obtainable.

Edited February 7, 2023 by Tom Booth

[exchemist]

13 hours ago, Tom Booth said:

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

I said: "And yes, an engine rejecting less waste heat than the prediction of the Carnot efficiency limit would violate a physical "law" of the universe."

To which you responded: "Where is your experimental proof of this?

That is a stupid response. The Second Law of thermodynamics is - so far as we can tell - a physical law of the universe and the Carnot limit results directly from it. Ergo an engine rejecting less heat that the Carnot limit would violate a law of the universe. It's not a matter of experiment. It's a matter of definition.   

4 hours ago, Tom Booth said:

 

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

 

Trouble is, you are not engaged in "scientific enquiry". If only you were. You have an idée fixe, which you have had for a decade now. You spend your time doing pisspot "experiments" in your garage in a hopelessly unscientific way, while determinedly refusing to learn basic science and instead scrabbling around for bizarre and inconsistent justifications for your refusal to accept the Second Law of Thermodynamics.

You are tilting at windmills.

 

[Tom Booth]

2 hours ago, exchemist said:

I said: "And yes, an engine rejecting less waste heat than the prediction of the Carnot efficiency limit would violate a physical "law" of the universe."

To which you responded: "Where is your experimental proof of this?

That is a stupid response. The Second Law of thermodynamics is - so far as we can tell - a physical law of the universe and the Carnot limit results directly from it. Ergo an engine rejecting less heat that the Carnot limit would violate a law of the universe. It's not a matter of experiment. It's a matter of definition.   

Trouble is, you are not engaged in "scientific enquiry". If only you were. You have an idée fixe, which you have had for a decade now. You spend your time doing pisspot "experiments" in your garage in a hopelessly unscientific way, while determinedly refusing to learn basic science and instead scrabbling around for bizarre and inconsistent justifications for your refusal to accept the Second Law of Thermodynamics.

You are tilting at windmills.

 

It's not a "physical LAW" if a physical experiment demonstrates it can be violated. 1800's style "scientific" [sic] "LAW" [sic] proclamations are no longer considered a form of valid scientific inquiry.

2 hours ago, exchemist said:

Trouble is, you are not engaged in "scientific enquiry".

"You" me (Tom Booth) did not propose an experiment. Swansont proposed an experiment.

I for one would like to hear exactly what he had in mind, but he was shut down.

I suppose next you'll be calling him Sancho Ponza

I guess that's appropriate

Some dragon.

Edited February 7, 2023 by Tom Booth

[exchemist]

53 minutes ago, Tom Booth said:

It's not a "physical LAW" if a physical experiment demonstrates it can be violated. 1800's style "scientific" [sic] "LAW" [sic] proclamations are no longer considered a form of valid scientific inquiry.

"You" me (Tom Booth) did not propose an experiment. Swansont proposed an experiment.

I for one would like to hear exactly what he had in mind, but he was shut down.

I suppose next you'll be calling him Sancho Ponza

I guess that's appropriate

Some dragon.

This is a muddle. Stating what a physical law says is - obviously - not a piece of "enquiry". It's a statement of the conclusions of enquiries.

The Second Law of Thermodynamics is a conclusion put forward as a result of scientific enquiry. As previously stated, it has been found, in the course of some 150 years of science and engineering, to be something that is always obeyed, and there has been a very detailed statistical model of how it arises for over a century.

You claim to have studied it for years, yet it is plain you do not even understand the relevant concepts, such as entropy, still less its origin in the statistical behaviour of molecules. You seem to think you can override a century and half of experience and theory by futzing around with toy machines and doing your experiments sufficiently badly as to obscure what is happening.

That is tilting at windmills.     

[Tom Booth]

On 1/26/2023 at 12:05 PM, swansont said:

The gas at the end is colder than the gas before the piston moves. The cold reservoir heats up. If you disagree, then where does the energy come from that appears as mechanical work?

Just going back and looking through your past posts for your experiment proposal, and came across this.

I don't think I answered that question directly, or maybe I did, but I'm not sure I understood the question at the time.

I've been reading about and talking about conversion of heat into work for so many years now it's inconceivable to me that anyone with a knowledge of general thermodynamics does not understand this basic concept.

That the heat input is converted to work is a given, is it not?

It's just a question of how much is converted, but obviously "the energy that appears as mechanical work" is derived from the energy that originally entered the working fluid as HEAT.

That anyone here with any kind of scientific background could even ask such a question is almost inconceivable to me.

It is a well established fact that a heat engine converts heat into mechanical work.

The heat does not turn the engine as it flows through to the sink to produce work like a water wheel.

The heat is, or becomes the work output and the heat, as such vanishes.

It is a bit difficult to wrap your head around, but when heat is converted to work in a heat engine the heat vanishes. The heat has gone out as work. What is left behind is COLD, which is what we perceive or measure as an absence of heat.

When the heat goes out of the working fluid as work, the working fluid looses heat dropping in temperature, becoming cold.

If the heat also continued on to the sink, that would be a violation of conservation of energy.

Edited February 7, 2023 by Tom Booth

[studiot]

8 hours ago, Tom Booth said:

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

That was 2013

 

Thank you for reminding me of that thread.

 

Here are a couple of references from that thread (my highlighting)

Do they sound familiar?

 

Quote

Tom you seem to have written a lot without saying anything at all. What is the point of your posts? That heat isn't a fluid? That's pretty obvious. Was there some other point you wanted to make? Please elaborate if so. It appears as if you just want to argue what a reservoir is when we already have a perfectly good definition and description of one.

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

 

 

Quote

A device that uses a heat pump to create a temperature difference to drive a heat engine, achieving a positive energy output is a violation of the 2nd law of thermodynamics: a type 2 perpetual motion machine. We don't do perpetual motion machines here. Thread locked.

Reference: https://www.physicsforums.com/threads/assumed-violation-of-physics-heat-vs-work.667129/page-3

 

Edited February 7, 2023 by studiot

[sethoflagos]

6 hours ago, Tom Booth said:

I've done experiments attempting to measure or determine the "flow" of heat "through" the engine in every way I could think of.

And after so many years what do you have to show for all this effort but lame excuses for your failure to produce one single testable data point to back up your wild claims.

 Compare with the test results presented in the attachment.

Hirata et al..pdf

[swansont]

9 hours ago, Tom Booth said:

What's your suggestion for an experiment

You can go back and read it.

[Tom Booth]

2 hours ago, swansont said:

You can go back and read it.

Still looking.

In the mean time, would it be possible to get a response, or could someone actually commit to an opinion regarding how the percentage arrived at by means of the  Carnot efficiency formula is to be properly applied in a real world scenario? Or alternatively, how it is to be interpreted as an upper ceiling (or whatever name anyone might want to call it) on efficiency for any given situation?

Maybe there are more, but I've encountered at least two ways of viewing this percentage in my studies on the subject:

Given a ∆T with the temperatures as follows 68°F (cold), 200°F (hot) works out to 20.01%

This seems like a realistic example. We have some water at a constant simmer under the engine with an ambient temperature of 68°F

Both hot and cold source are effectively infinite. We keep the steamer going continuously and the ambient atmosphere is effectively infinite.

Mathematically this 20% arrived at works out as 20% of the absolute temperature scale. This is not just true of the two temperatures I have selected by some remarkable coincidence. It is true of any two arbitrary numbers plugged into the equation. I'm not of course saying that the percentage is always 20%

The percentage is always representative of the low temperature subtracted from the high temperature and the "efficiency" is the ∆T. The temperature difference on the absolute scale. Always.

At absolute zero, of course efficiency is 100% because the temperature difference is 100% of the temperature scale from the highest to the lowest temperature.

If we take the temperatures 4°K and 0°K for example, our "hot air" engine will be 100% efficient though no air and no gas, not even helium can exist as a gas at 4°K

We could take a high temperature of 5 trillion degrees C where nothing can exist but a quark-gluon plasma or some such and 0°K as our sink and the efficiency of our engine is again 100%

Can we actually test the accuracy of this formula at these extreme scales? Probably not. 

So returning to a more realistic scale that at least can be tested experimentally, in theory, what does the 20% actually represent in practical terms?

We know, factually, it is simply the temperature difference calculated as a percentage.

Of course, I've dropped the decimal,just so we have a nice round number.

Allegedly, so some of the literature on the subject, textbooks etc.relate, this temperature difference comprising in itself 20% of the absolute temperature tells us something more than just the temperature difference on the absolute temperature scale, but what exactly?

As I see it we have two options, but which is correct, or can they both be reconciled in some logical way?

I'll get into more detail when I have time.

I have sent away for an "upside down" Stirling engine to run some tests as suggested by Ghideon's "rhetorical question"

This is just something to do in the mean time. Get our facts and definitions straight. What is it exactly we are supposed to be testing? What does the 20.01% actually represent in real terms as far as actual heat input and heat and work output?

 

And I would suggest we confine the discussion to Stirling type hot air/gas engines where only heat and work cross the system boundary, just to keep things simple. I.e. no fluids like steam, gasoline, diesel fuel, gas or air etc.

[Ghideon]

10 hours ago, Tom Booth said:

I think the rate at which ice melts also makes a good gauge or measure for comparison testing.

I disagree, there are too many unknown variables.

 

10 hours ago, Tom Booth said:

Sandwich the heat source between two engines. Makes measurement so much easier. The heat cannot dissipate to the surrounding ambient without going through one or the other of the engines. Very clean data should be obtainable.

 I don't see how that experiment helps you debunk established theories.

28 minutes ago, Tom Booth said:

how it is to be interpreted as an upper ceiling (or whatever name anyone might want to call it) on efficiency for any given situation?

I'll take a look at this later!

[Tom Booth]

At the start of our setup, we have ambient air, and everything else, the steamer machine, water, engine etc. all at (approximately) thermal equilibrium at 68°F (20°C, 293.25°K)

Carnot efficiency, of course is zero.

Now we plug in our "infinite" heat source  the water simmers at 212°F but cools down a bit on its way up to contact the engine. (I'm at a fairly high elevation here though, so the boiling point is likely a bit lower than 212°F)

I've selected a fairly reasonable temperature, (I think) as the high temperature in our calculations a bit below boiling (212°F) at an even 200°F (93.3°C, 366.5°K)

Mostly I'm just taking a reasonable (realistic) set of temperatures that works out to an even 20% Carnot efficiency.

In reality 200°F for the heat input is probably a bit high. I'm still working on ways of attaching temperature probes for more accurate readings.

I did ask for opinions regarding where exactly the readings should be taken but got no response.

There are 4 probes on one thermometer and 1 additional probe on my multimeter, then there is the thermal camera that can reveal spot temperature.

I did install all new batteries in these devices and this seems to have largely resolved most of the slight discrepancies in the readings to within a few degrees 

Edited February 7, 2023 by Tom Booth

[swansont]

On 2/5/2023 at 6:38 PM, Tom Booth said:

It is quite typical of Stirling engines to take some time to reach operating temperature and have a few false starts if not yet warm enough

I just checked mine; boiled water and poured it into a coffee mug, put the engine on top and it started up after 10 seconds.

[Tom Booth]

45 minutes ago, swansont said:

I just checked mine; boiled water and poured it into a coffee mug, put the engine on top and it started up after 10 seconds.

OK.

And?

Was it's flywheel also dragging on some loose Aerogel insulation? Does your engine have a magnetic displacer?

I agree the experiment was less than perfect in many ways, but once the problems were resolved, such as the insulation rubbing on the flywheel, the engine ran for another 3 hours. My phone ran out of video memory storage and cut out after about 2 hours but my understanding is without "continual cooling" the engine should not be able to complete a single revolution.

I did, as I said earlier, trim away the insulation fibers that were rubbing on the flywheel and made some other changes. This time the engine started up and continued running more easily.

That was also video recorded if you care to look at it.

Edited February 7, 2023 by Tom Booth

[exchemist]

4 minutes ago, Tom Booth said:

OK.

And?

Was it's flywheel also dragging on some loose Aerogel insulation? Does your engine have a magnetic displacer?

I agree the experiment was less than perfect in many ways, but once the problems were resolved, such as the insulation rubbing on the flywheel, the engine ran for another 3 hours. My phone ran out of video memory storage and cut out after about 2 hours but my understanding is without "continual cooling" the engine should not be able to complete a single revolution.

I did, as I said earlier, trim away the insulation fibers that were rubbing on the flywheel and made some other changes. This time the engine started up and continued running more easily.

That was also video recorded if you care to look at it.

Your videos are a waste of time. This has been explained to you before.

[Tom Booth]

There is also an old video of my attempts to start the same engine without insulation, and nothing rubbing on the flywheel. It had a few false starts also.

The magnet has to be able to lift the displacer, which is a bit more of a job than just having the displacer attached directly to the crank.

This was 9 months ago: the only "temperature reading" taken was with my fingers. The top of the acrylic engine body remained cool to the touch in my subjective estimation. So it stayed at least below body temperature if it felt cool to the touch.

 

30 minutes ago, exchemist said:

Your videos are a waste of time. This has been explained to you before.

Well, how about just sticking with the math for now then.

Do you have any problems with my calculations or statements in the two previous posts?

Here: 

 

And here:

https://www.scienceforums.net/topic/128644-is-carnot-efficiency-valid/?do=findComment&comment=1228952

 

[swansont]

Quick experiment. Heat up water for coffee mug, also chill some water to put on top plate. Get engine running, pour a little water on top plate and also on counter. The water on the cold reservoir plate clearly warmed up faster than the water only subject to ambient air.

17.3 degrees after a minute or so; you can already see some warming at the edges. 24.8 after about four minutes. The ambient pool looks basically unchanged. Picture with my FLIR thermal imager phone attachment

 

[Tom Booth]

Just a few observations, not intended to be confrontational. Very glad to see someone else doing some experiments, thank you!

1)Curious about the ambient temperature.

2)Material the countertop is made of. (Conductivity compared with engine.)

3) it appears the six or so metal bolts are intact which hold the engine together and could act as heat conductors.

4) Convection of hot air transferring heat between lower and upper plates outside of the engine.

Not trying to be argumentative but the bolts and convective air currents both outside the engine's working fluid could potentially account for at least some of the difference.

Also the countertop, if of a less heat conductive material than the engines heat exchanger might absorb ambient heat more slowly, therefore transferring heat to the water at a slower rate. Of course if aluminum or copper or something could conduct heat to the water more quickly.

Thank you!

There seems to be some especially hot "hot spots" around at least some of the bolts. Unless maybe that is the cup handle? But at least two other such lesser apparent hot spots seem to coincide with the bolt arrangement.

[TheVat]

As a gawker, looking in here and haven't read the 15 pages, have to ask: what, besides expensive cogeneration, are Stirling engines good for?  Using external heat, as opposed to IC, to pressurize a gas and turn that heat into work seems pretty inefficient.  That's why we don't drive steam cars.  If I have a car and it's winter, then my waste heat can go simply to heating the cabin via a simple diversion of coolant.  But nobody is using that waste heat to power a Stirling.

Also I don't understand "transferring heat" the way OP is saying it.   Heat is kinetic energy.  Energy is transferred.  Higher kinetic energy molecules are transferring energy to lower kinetic energy molecules on the other side of a barrier.  Entropy.  A slow process, would seem like.  The external heat needs lots of time for energy to transfer to the inside of the engine.   Where would the wait be worthwhile??

 

 

[swansont]

16 minutes ago, TheVat said:

Also I don't understand "transferring heat" the way OP is saying it. 

The OP is fixated on the outdated idea of caloric.

 

16 minutes ago, TheVat said:

 Heat is kinetic energy.  Energy is transferred. 

Heat is not kinetic energy.

Heat is the transfer of energy owing to a temperature difference. This can happen via radiation, conduction or convection.

The thermal energy of a body is related to kinetic energy of constituent atoms or molecules, which we associate with temperature. But two objects at the same temperature will have not heat transfer between them, despite having vibrational KE

51 minutes ago, Tom Booth said:

Just a few observations, not intended to be confrontational. Very glad to see someone else doing some experiments, thank you!

1)Curious about the ambient temperature.

Not particularly relevant, as it’s the same for both samples. Room temperature.

51 minutes ago, Tom Booth said:

2)Material the countertop is made of. (Conductivity compared with engine.)

Higher than air, to be sure, so it would tend to warm the water faster than air would.

51 minutes ago, Tom Booth said:

3) it appears the six or so metal bolts are intact which hold the engine together and could act as heat conductors.

Which might heat the edge of the water but not the center

51 minutes ago, Tom Booth said:

4) Convection of hot air transferring heat between lower and upper plates outside of the engine.

Again, this would affect the edge, not the center.

51 minutes ago, Tom Booth said:

Not trying to be argumentative but the bolts and convective air currents both outside the engine's working fluid could potentially account for at least some of the difference.

Only some? It needs to account for all of it if your assertion is correct.

 

51 minutes ago, Tom Booth said:

Also the countertop, if of a less heat conductive material than the engines heat exchanger might absorb ambient heat more slowly, therefore transferring heat to the water at a slower rate. Of course if aluminum or copper or something could conduct heat to the water more quickly.

The counter was at ambient temperature before the water was added. As I noted, that should heat the water faster.

 

51 minutes ago, Tom Booth said:

Thank you!

There seems to be some especially hot "hot spots" around at least some of the bolts. Unless maybe that is the cup handle? But at least two other such lesser apparent hot spots seem to coincide with the bolt arrangement.

You are free to replicate this, as you have repeatedly been invited to do.

[sethoflagos]

26 minutes ago, TheVat said:

As a gawker, looking in here and haven't read the 15 pages, have to ask: what, besides expensive cogeneration, are Stirling engines good for?  Using external heat, as opposed to IC, to pressurize a gas and turn that heat into work seems pretty inefficient.  That's why we don't drive steam cars.  If I have a car and it's winter, then my waste heat can go simply to heating the cabin via a simple diversion of coolant.  But nobody is using that waste heat to power a Stirling.

Also I don't understand "transferring heat" the way OP is saying it.   Heat is kinetic energy.  Energy is transferred.  Higher kinetic energy molecules are transferring energy to lower kinetic energy molecules on the other side of a barrier.  Entropy.  A slow process, would seem like.  The external heat needs lots of time for energy to transfer to the inside of the engine.   Where would the wait be worthwhile??

Much of what you say is correct which is why they got ignored for over a century.

Compared to IC engines, they're more amenable to renewable energy resources (such as solar collectors etc); they can be very quiet; and as static devices they're quite competitive in cost with IC up to ~100 kW.

 

[TheVat]

2 minutes ago, swansont said:

 

Heat is not kinetic energy.

Heat is the transfer of energy owing to a temperature difference. This can happen via radiation, conduction or convection.

 

Thanks, I clumsily expressed that in two sentences so left "transfer of" out of first one.  Nor did I mean to imply energy transfer after temps have equalized. 

And this....

 

33 minutes ago, TheVat said:

Higher kinetic energy molecules are transferring energy to lower kinetic energy molecules on the other side of a barrier. 

I guess that should be "lower average kinetic energy."  Write in haste, repent at leisure.

2 minutes ago, sethoflagos said:

Compared to IC engines, they're more amenable to renewable energy resources (such as solar collectors etc); they can be very quiet; and as static devices they're quite competitive in cost with IC up to ~100 kW.

Ahh.  Did not know that last bit.  You've all sent me off to do some reading.  Thanks.  (And I can see the use with thermal solar, yes.  Where your heat source is, by definition, external.   And the setup is static.)

[Tom Booth]

30 minutes ago, swansont said:

You are free to replicate this, as you have repeatedly been invited to do

That would be difficult (exactly)  since you were unresponsive regarding some of the parameters.

Anyway I already have, many times, except for modifications: replacing highly conductive metal bolts, insulating air passages between the plates and so forth to eliminate extraneous variables.

Some of your conclusions seem questionable. A metal heat exchanger doesn't conduct heat under water sitting directly on top of it, only to the extremities. Heat at the edge of a .metal plate remains only at the edge. No difference in conductivity between the metal of a heat exchanger and a countertop of some other, possibly non-heat conducting material, to name a few off the top of my head.

Oh, did you suggest heat conducted by metal bolts to a metal plate remains completely localized

Transfer of heat between air and metal vs air and another material is no different.

If everyone is satisfied your results are conclusive I guess we can wrap it up. The lunatic, tin foil hat, perpetual motion crank has been proven wrong. Case cosed.