Tom Booth

I was mistaken, Swansont made that comment on a different closed thread: 

Quote

You can ask questions and get answers about mainstream physics. That’s all.

1 hour ago, swansont said:

It’s perfectly fine to use idealized processes in one’s analysis.

And the point is that even if a process is not perfectly isothermal, it is possible to have work done by a change in pressure and volume, meaning such work is not derived from a change in temperature. 

Are we still in agreement?

I guess not.

Isothermal or not, "heat" as such is being consumed, or used up.

If you walked past a fireplace and saw logs all afame in the hearth, then came back three days later and saw what appeared to be the same logs still burning, would you conclude that wood is not consumed by fire?

It is the same with Isothermal expansion, without heat being continually added there would certainly be cooling.

There would certainly be a temperature change if heat were not added to compensate for that being converted. Right? Do you disagree?

Do you think that because there is no temperature change there is no consumption of heat? Like the apparent eternally burning log?

2 hours ago, Ghideon said:

The opening question was "According to mainstream physics: Is heat "destroyed" in a heat engine?". Do you want the answer as stated by current mainstream physics of today? Or do you want the answer as it was in mainstream physics at some specific time in the past? (Or other alternative?). Since many historical references are brought up, can you clarify?

 

That heading was due to Swansont informing me that I am only allowed to ask questions about mainstream science.

Frankly I'm not particularly interested in past/present theories per se.

This thread originated in the Lounge on the assumption we would be free to discuss "anything" freely, there at least.

But there too, the thread was locked and sent to "Trash". Though it appears that Swansont has modified his admonition to ask questions "only about mainstream science". So mainstream science it is.

However, any thoughts on the subject are OK by me.

It appeared that the Maxwell's demon thread was closed because of what I wrote in this thread:

Quote

The cold produced by a heat engine is the result of destroying the heat, so that it no longer exists.

Apparently that comment was too much for Swansont.

6 minutes ago, exchemist said:

It wasn't his theory, though.

It was Lavoisier's, which Carnot inherited as the then prevailing model and which he suspected was faulty, as some of your earlier extracts from his Appendix A showed.  

The Caloric theory predated Carnot, but I'm mainly referring to Carnot's likening heat powering a heat engine to water going over a mill wheel. As far as I'm aware that was Carnot's original conception.

2 hours ago, studiot said:

2 hours ago, Tom Booth said:

concept based on the realization that heat is energy that changes form and not an indestructible fluid.

And who, exactly, realised that and when did this Eureka moment arrive ?

I believe that (underlined) was your question you are demanding I answer. Correct?

Who was the first to realize heat is a form of energy that can be transformed?

As far as I know the realization came to many, gradually, over time, with continued experimentation.

In those unpublished writings Carnot proposed numerous additional experiments that could be or should be performed, in order to further progress, to gain more empirical data on the subject.

24 minutes ago, studiot said:

Then you shouldn't make claims you have no knowlege of and can't or won't back up.

You most definitely made claims about others than Carnot, naming several prominent workers from the past.

I've already cited the relevant quotations from Carnot, Kelvin and Maxwell previously in this thread. Other than that I'm not entirely sure what you are going on about as far as "claims".

1 hour ago, Boltzmannbrain said:

Yeah, I had a feeling this was a motivation.  Thanks for the backstory. 

More slanderous lies.

My only motivation originally was to exhibit the recorded results of some experiments.

I proposed the idea that perhaps those results could be explained on the basis of conservation of energy. Heat being transformed into work, producing a cooling effect.

These were simple observations and speculations based on basic known  principles.

Your characterization is completely  unwarranted, unfair and untrue. I'm simply trying to get at the truth, and hopefully let the experimental results tell their story and let the chips fall where they may. I have no stake in the outcome one way or the other. Except that by understanding better how these engines actually work, perhaps some improvements could be made.

28 minutes ago, studiot said:

Note again you have avoided a direct question.  (That's the line with a question mark that you quoted).

 

As I understand Carnot's crowning glory it was the realisation that

"If you have a source of heat you can obtain work from it "

or words to that effect.

 

So please provide a proper reference with all important dates, as I requested.

 

I only know of the history as described by Carnot himself in his unpublished writings.

Many many experiments were cited by Carnot as being responsible for his change of mind on the subject of the nature of heat.

Quote

 

When a hypothesis no longer suffices to explain phenomena, it should be abandoned.

This is the case with the hypothesis which regards caloric as matter, as a subtile fluid.

The experimental facts tending to destroy this theory are as follows:

(1) .... (2).... (3)... etc. etc.

 

Read it for yourself.

The term translated "caloric" seems to be in question. I'm open to the possibility this may be a mistranslation.

1 hour ago, studiot said:

And who, exactly, realised that and when did this Eureka moment arrive ?

You have been noted as castigating Carnot many times for his 'belief in caloric'

 

I don't believe I can be legitimately accused of "castigating Carnot" the man. Only the primitive theory of heat as an indestructible fluid that flows from one "reservoir" to seek out another "lower reservoir".

I admire Carnot the man, for being, perhaps the first to discard his own theory. Unfortunately the world did not have access to his later insights for many years to come.

27 minutes ago, exchemist said:

Chaleur shurely? 😄

Chauler is a verb, meaning to lime or whitewash.

Here is a link to Carnot's original: http://www.numdam.org/item/10.24033/asens.88.pdf

Chaleur just means heat and, so far as I can see, will have long predated Lavoisier''s  scientific concept of caloric. Lavoiser seems to have introduced caloric because he realised the idea of phlogiston didn't work. 

 

 

Not to negate your point necessarily. But just to be clear, the excerpts cited that use the word translated "destroyed" are from Carnot's unpublished writings which remained unknown for some time.

In the meanwhile, Carnot's successors followed his published work promoting theories Carnot himself had already abandoned as reflected in the unpublished writings.

15 minutes ago, studiot said:

I'm suprised Tom didn't go back to the realy father of thermodynamics, that ancient Greek who thought the Earth was flat and that there were four elements earth, water, air and heat (fire).

So can I quote them to promote my flat earth leanings ?

Anyway going back to retrieve quotes from Carnot an his contemporaries it is not suprising the they talekd of 'destroying' heat.
After all they thought it to be a substance.

And their word for it was caloric, which  unfortunately survives to this day in French as Chauler, Portugese and Spanish as calor, etc.

Atom was another ancient Greek concept that we now understand quite differently from the original.

So what, our knowlesdge and understanding of physics has improved over the millenia so keeping older ideas is only useful if for engineers if it provides an easy route to calculation or to historians.

What you seem to be failing to understand is that the "destruction" of heat was a NEW concept based on the realization that heat is energy that changes form and not an indestructible fluid.

7 hours ago, Lorentz Jr said:

Regular posters took the word in scare quotes at face value and kept trying to explain the conservation of energy to the O

As has been pointed out, the word in "scare quotes" traces back to Carnot and the question is basically, how should we interpret the meaning of his statement. Is it really true that when work (or "motive power" - Carnot) is produced heat is destroyed?

What exactly did Carnot and others mean by that? A fair question I think, particularly when my discussions are being shut down for the crime of simply restating conservation of energy. Experimental observations just thrown out the window, not just ignored, but  banned, ridiculed, slandered.

When one form of energy is produced, the other form of energy ceases to exist utterly. That does not violated conservation of energy, that IS conservation of energy!

Let's not butter it up and say the heat is mery rolled up, or crushed like a car in a wrecking yard, or it's parts are scattered. No, it is utterly annihilated, not just changed in shape.

It (the heat, as heat) does not linger around. No, it is gone, vanished, disappeared, and the absence of heat is cold. The heat being "destroyed" does not leave some wreckage of scattered or dispersed HEAT behind, it leaves COLD, a drop in temperature.

Well is it just SOME, heat or ALL the heat, that is another question, but certainly ALL of that portion of the heat that was converted to some other form of energy is now gone.

This very strong wording: destroyed, vanishes, ceases to exist, disappears; has been used over and over, including by the various "founding fathers" of thermodynamics, Carnot, Kelvin, Maxwell... and many of the dusty old physics books from my father's book shelf.

Is this concept obsolete? Certainly. At least I think so, in the sense that Heat is now recognized as a transfer of energy, not a thing in itself that can be created or destroyed, but IMO that does not alter the principle, does it?

Heat goes out as "work", a different form of motion. The motion belonged to the gas particles, the "working fluid" and now it belongs to the flywheel.

This IS a rather mind boggling idea or concept. The warmth in the air transformed into the rotation of cold steal, but that is simply conservation of energy, not as some in here would like to portray, the ravings of some perpetual motion "crank". If someone does not understand this basic principle of conservation of energy then they are the perpetual motion crank thinking that heat can be used to run an engine and then just continue on it's merry way through the engine to the other side.

1 hour ago, swansont said:

Not if it’s an isothermal expansion.

Fantastic.

Since for the most part an isothermal expansion is an unrealizable ideal not possible in a real engine we are pretty much in full agreement.

1 hour ago, Lorentz Jr said:

You said the temperature of the fluid drops:

As a general rule, yes. That is the principle. Isn't it? When heat is converted to work the temperature of the working fluid drops, as a matter of conservation of energy. Of course more heat can sometimes be added either simultaneously or in another cycle.

I already conceded, of course the temperature could be maintained or even increased by adding more heat as the heat is being "consumed" but that is not the question being addressed. The question is:

According to mainstream physics: Is heat "destroyed" in a heat engine?

If I might defer to the father of thermodynamics himself:

Quote

"Heat is simply motive power, or rather motion which has changed form. It is a movement among the particles of bodies. Wherever there is destruction of motive power there is, at the same time, production of heat in quantity exactly proportional to the quantity of motive power destroyed. Reciprocally, wherever there is destruction of heat, there is production of motive power."

Reflections on the Motive Power of Heat/Appendix A

 

 

Someone here seems to think his use of the term "destruction" is a mistranslation.

Quote

When work is transformed into heat or heat into work,
the 'quantity of work is dynamically equivalent to the
quantity of heat.

It has also been expressed in this way :

"When equal quantities of mechanical effect are produced by any means whatever from purely thermal sources,... equal quantities of heat are put out of existence... " (Kelvin).

This law has been confirmed in a variety of ways :

1. The experiments of Joule, Rowland, and others in generating heat by the expenditure of work.

2. The experiments of Him and others, showing that when work is done by a heat-engine heat disappears.

Henry Smith Physics for university students (Volume 2)

OK, so copyright 1904 does the copyright date invalidate the principle expressed?

Here's a good one:

Quote

when heat does work in an engine, a portion of the heat disappears.

James Clerk Maxwell. Theory of heat

56 minutes ago, Lorentz Jr said:

Your statement is correct if there's no heat source: The fluid will cool off.

Yes, if there's no other heat source compensating for the work done.

Not really. The principle is conservation of energy. The heat lost by the fluid is equal to the work it does, but the fluid's temperature is only guaranteed to drop in those specific situations where there's no external or internal heat source.

It's not a general principle, it's just an outcome that occurs in certain circumstances.

Generally speaking I have no problem with your statements and can heartily agree with the whole, except perhaps the last in part, in that I believe it IS a general principle, It is simply conservation of energy. When energy as work is taken out, an equivalent amount of heat "disappears" (so to speak). But to suggest this is just an outcome that might be avoided seems a bit disingenuous or hair splitting.

Like if I said If you put a match to the wood in a fireplace the wood will burn up.

Well no, that is only a circumstance in a particular instance where there is no additional wood available.

Wood burns, as a general principle.

As you stated: "The principle is conservation of energy. The heat lost by the fluid is equal to the work it does" that is not something that can be sidestepped, or avoided.

In general that means there will be a temperature drop barring some additional intervening circumstance such as the introduction of additional heat.

16 minutes ago, Lorentz Jr said:

Your phrasing ("Period.") suggested that there are no exceptions to your rule. @swansont was pointing out that there are plenty of exceptions, because your rule only describes the class of situations where there's no other heat source.

My statement is confined to a specific phenomenon, heat converted to work, period.

When a gas expands and does work, driving a piston in an engine there is a temperature drop in the working fluid as a consequence of the energy (work) output.

Is that not a fact?

You can add some corollaries to that, exceptions or whatever but we are talking about a basic principle.

The work output of the engine results in a temperature drop within the working fluid. I don't think it would be accurate to say adding heat would "prevent" that principle from operating. It could be compensated for but not "prevented" or "avoided" in the general accounting.

15 minutes ago, Lorentz Jr said:

Or steam engines.

? What about steam engines. That would be a different class of engine with its own complications. Latent heat of vaporization within the steam for example.

Strictly speaking, in a steam engine heat is added to the boiler not the working fluid in the cylinder, nevertheless cooling takes place in the cylinder as a consequence of work output.

13 minutes ago, studiot said:

Exactly.

and what do you think the working fluid is in a diesel engine ?

Air mostly.

27 minutes ago, studiot said:

Very clear thank you.

Clear that you have classed all combustion engines as not being heat engines.

I realize many people classify any and all engines, gas, diesel, propane etc. Internal combustion engines along with "heat engines" and it is true. These are heat engines, because the product of combustion HEAT, is what generally speaking, causes the expansion of a working fluid producing work output, but the particulars of the reaction that produces the heat is generally pretty irrelevant to the question.

For simplicities sake it might be helpful if the discussion were confined to external combustion heat engines, i.e. Stirling engines, where nothing crosses into or out of the engine other than heat and work.

Sorry for cutting you short, but my statement was in regard to a temperature drop within the working fluid due to work output. I should have been more specific in the heading, but I don't particularly want to get bogged down in debate about specific chemical reactions involved in combustion.

1 hour ago, swansont said:

 

It’s the “Period” which implies that there is nothing else. It means that no heat is transferred out, which is contrary to mainstream physics. The notion that the work is solely driven by the heat in and work out, and that these are equal, is not mainstream physics. “Work goes out, the temperature goes down. Period.” is not widely accepted.

There are examples of work without heat flow - adiabatic compression and adiabatic expansion against pressure or some other impediment, like a spring. But these are only individual steps - they are not the entirety of a heat engine. There’s no heat in or out. All there is is the work being done, which changes the internal energy.

https://en.m.wikipedia.org/wiki/Adiabatic_process#Adiabatic_free_expansion_of_a_gas

You contradict yourself saying "it's contrary to mainstream science" then proceed to give an example: "There are examples of work without heat flow - adiabatic compression and adiabatic expansion against pressure or some other impediment, like a spring."

I would simply add to that example the fact that there is a temperature drop within the working fluid.

1 hour ago, Ghideon said:

 

What does the bold part mean?

(Bold highlight by me)

Perhaps the drop in temperature can sometimes be compensated for .

If there is a simultaneous addition of heat. i.e. Isothermal expansion for example; the working fluid which would otherwise suffer a drop in temperature maintains the temperature due to additional simultaneous heat input alongside the work output. It may even increase in temperature, none of that however negates or contradicts the principle involved as far as heat being converted into work.

For every unit of work output a unit of the heat/energy input to the engine "disappears" or is subtracted from the account so to speak.

3 hours ago, swansont said:

Quoting Tom Booth:

 

In a gas, the energy is temperature dependent. So a work output results in a drop in temperature, but no "heat" went out, only "work", but the consequent drop in temperature is the same though there was not any heat transfer, only a work transfer.

A bit repetitions but clear enough.

Work performed by the "working fluid" (air or gas) in a heat engine results in a temperature drop of the working fluid.

Work goes out, the temperature goes down. Period. A basic principle, widely accepted.

Perhaps the drop in temperature can sometimes be compensated for but that does not negate the principle: conversion of heat into work results in a temperature drop within the working fluid as a consequence of the energy output.

True or not?

9 minutes ago, studiot said:

Not necessarily.

Some chemical reactions evolve or accept either work or heat or both sometimes with a temperature change, sometimes not.

You made no answer to my previous post so this is the last time I attempt to help you.

The topic is clear "in a heat engine" not a chemical reaction, so irrelevant.

7 minutes ago, Genady said:

Then, whatever you said, you didn't say it clear enough and it was open to misinterpretation

Swansont quoted one paragraph. A few sentences. What words did you personally find unclear?

6 minutes ago, Genady said:

Yes, you did. You said, that if temperature does not change, then the work is done without heat transfer. This is not so. For example, in isothermal process, a work is done, the heat is transferred from the environment to the system, and the temperature does not change.

That's not what I said at all.

Please quote my actual statements not these straw man, made up supposed twisted mischaracterizations, please.

5 minutes ago, Ghideon said:

Advice: Maybe you can ask about what established science agrees upon to be correct instead? That may allow for the discussion to progress.

Swansont is doubling down that I made an untrue, false statement. I'd like to know specifically what he has issue with. Others here don't seem to have a problem with it, "so what".

I agree, so what? I said nothing that is not accepted mainstream recognized, confirmed, experimentally verified science. AFAIK, so what exactly is Swansont's big issue with my statement.

He mistakenly, falsely, reads things into it that are not there then goes on the attack against these imagined errors in my statement. I'd very much like to know what he has an issue with, specifically.

37 minutes ago, swansont said:

I guess that’s the problem in a nutshell: You don’t see how my comments apply to what you said. But what you said wasn’t true.

[Emphasis added]

If you don't mind, please quote the specific statement, words of mine, sentence, paragraph or whatever to which you are referring by the bolded words. "what you said wasn’t true."

What specifically, in your opinion, did I say that "wasn't true". Please quote the words in my statement you consider not true. Please 

You seem to be reading things into my statement that I did not actually say at all.

1 hour ago, Genady said:

So what? Heat is not conserved. Energy is conserved. The form of energy changes. There is no confusion there.

Thank you! My point exactly.

51 minutes ago, swansont said:

Quote

In a gas, the energy is temperature dependent. So a work output results in a drop in temperature, but no "heat" went out, only "work", but the consequent drop in temperature is the same though there was not any heat transfer, only a work transfer.

Not true.

What specifically in my above statement do you consider "not true".

Your remarks here bear no  correspondence to what I actually said:

51 minutes ago, swansont said:

If energy is transferred owing to a temperature difference between objects, it’s heat. Work is energy transfer that doesn’t depend on a temperature difference.

You don’t get to change these definitions.

Also, do not confuse a temperature change in time with a temperature difference between objects.

I don't know what's confusing. I'm trying to settle the apparent concussion.

I'm simply saying, is it not true that with work output there is a lowering of the temperature of the working fluid as a result?

That is, there was no "heat" transfer, but there was energy (work) transfer.

In a gas, the energy is temperature dependent. So a work output results in a drop in temperature, but no "heat" went out, only "work", but the consequent drop in temperature is the same though there was not any heat transfer, only a work transfer.

If the quantity of heat that produced the ∆T is transformed into work, than the ∆T no longer exists.

Maybe if the word "heat" can be avoided, or more strictly defined.

Heat is technically, I think, a temperature dependent transfer of energy.

Would that be an accurate statement?

If so, then somewhat euphemistically I guess, if there are two objects in close proximity, one at a high temperature and another at a low temperature then "heat" could be said to exist between them. There can be a temperature dependent transfer of energy between the two objects.

If, by some means, we were to cool down the hotter object (lower it's temperature by taking away some of its energy) so that there is no longer a temperature difference, then there can no longer be this temperature dependent transfer of energy. "Heat" between the two objects, then, no longer exists.

By "destroying" the ∆T we have also "destroyed" the potential for there to be any temperature dependent  transfer of energy. (as a statistical average at least, there are still energy transfers but they tend to balance out or nullify each other on the whole)

Are these fair statements so far?

Heat, as a temperature dependent transfer of energy can either exist, or not exist, it could be "destroyed" or "created" by either adding or subtracting energy from one side or the other (one object or the other).

This is no violation of the first law of thermodynamics, to assert that heat as such, as a temperature dependent energy transfer, either exists, or not, can be created or destroyed as a result of human intervention or engineering.

In other words, if I operate an engine, with the addition of some heat, thus expanding the working fluid and that expansion results in the performance of work, with the consequence that the temperature of the working fluid falls returning to a state of thermal equilibrium with the surroundings as when the operation started, before heat was introduced, then it could be said that the heat, first manifest as the introduction of a temperature difference "disappeared", "vanished" or was "destroyed" in the sense that the temperatures were equalized by a non-temperature dependent transfer of energy.

A transfer of energy by expansion of a gas is not necessarily temperature dependent. Energy can be transfered into the working fluid by the application of heat, raising the temperature of the working fluid, but the transfer of work out of the working fluid also results in a drop in temperature. This "work" is a non-temperature dependent transfer of energy, and yet the temperature of the working fluid drops as a consequence, and the "heat" as a temperature dependent means of energy transfer ceases to exist, or vanishes, as there is no longer any possibility for making any temperature dependent energy transfer. The temperatures have been equalized by other means. By the transfer of energy as "work" which is not a temperature dependent energy transfer.

When a quantity of "work" is performed by the working fluid, the capacity for energy transfer via heat has been diminished in equal quantity. The temperature difference has been "destroyed" as a result of the work output.

6 hours ago, Genady said:

In my studies of thermodynamics, I have never seen such expression or its equivalents in any textbook. Then, according to the mainstream physics: No.

I could provide some references where such expressions have been used from my own reading and research. Just one example for now, but certainly not an isolated case:

Quote

SECOND LAW OF THERMODYNAMICS
Garnet's Heat Engine
Definition of terms

1. Heat engine.

A heat engine is any mechanical contrivance by means of which heat is converted into work.

Steam engines, gas engines, oil engines, hot-air engines are all forms of heat engines.

All heat engines exhibit the characteristic that heat disappears during the performance of work....

2. Cycle of operations.

In every form of heat engine the transformation of heat into work is effected by subjecting some suitable substance to a cycle of operations (expansion, compression, condensation, etc.), so arranged that the work done by the substance during the cycle is
greater than the work done on it, and useful external work is done at the expense of the heat supplied to the substance.

From the First Law of Thermodynamics the amount of work performed by the gas on external bodies during the cycle must be equal to the heat which has disappeared.

ADVANCED LECTURE NOTES ON HEAT
BY J. R. ECCLES, M.A. (Cambridge University Press, 1921)

In this case, the term "disappears" is used.

4 hours ago, swansont said:

It’s been converted to another form, just as the first law of thermodynamics describes.

 

 

Could you be more specific?

What is meant by "converted to another form" exactly?

4 hours ago, Genady said:

If I have a flat sheet of paper and then roll it into a cylinder, did the flat sheet disappear, vanish, etc.? Certainly, not.

Is that what "another form" means?

The heat is rolled up into a different shape, but is still there as a constituent part of the working fluid?