Tom Booth

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

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? 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: Apparently that comment was too much for Swansont.

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.

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 In those unpublished writings Carnot proposed numerous additional experiments that could be or should be performed, in order to further progress, to gain more empirical data on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

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

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.

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.

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.

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.

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. 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: Someone here seems to think his use of the term "destruction" is a mistranslation. OK, so copyright 1904 does the copyright date invalidate the principle expressed? Here's a good one:

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.

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. ? 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. Air mostly.

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.

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.

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.