Fool wrote: ↑Fri Dec 15, 2023 2:31 pm
Tom, your quote of Carnot;
actual consumption of caloric but to its transportation from a warm body to a cold body
Specifically: from warm to cold...
Warm aka high energy
Cold aka low energy
Even water at the top of a water wheel has more energy, potential energy, internal energy, than the water at the bottom of the water wheel. But it's the mass, heigh and
gravity combination that represents it. Water is not converted to work. Neither is heat. Pressure and temperature are converted to work by way of volume change. Temperature is an indication of internal energy (bank balance), not heat. Heat is like a paycheck, or bill.
Potential energy is converted to work. And even that is not 100% convertible. Loss of height to drop into the bucket, and loss of height to drop out of the bucket.
You appear to be putting too much literalism into Carnot's analogy. All analogies fall apart when expanded into areas where they are invalid.
Heat is converted to internal energy, similar to raising water to give it more potential. Rasing the temperature of the working fluid by adding heat. To move between adiabatic lines, requires more energy at higher a temperature than at lower a temperature.
I think a better analogy would be gravitational acceleration. Higher temperature higher acceleration. The down side of a water wheel would have a higher potential than the up side. The downside would do more work higher temperature than the work need to raise the water back up, low temperature. Expansion verses compression. The gas stays in the water wheel. But it is still just an absurd comparison, "analogy".
The second law comes from observation and mathematics, and is not arbitrary. I wish it were arbitrary, the law of gravity too.
...
First of all you misquoted Carnot by way of omission. It isnn't "actual consumption of caloric" but 'The production of motive power is therefore due in steam engines
NOT to actual consumption of caloric but to its transportation from a warm body to a cold body".
You also misrepresent his position by saying: "Carnot's analogy".
He makes clear, IMO, that he is not making an analogy, but states: "the motive power of heat depends also on the quantity of caloric used, and
on what may be termed, on what in fact we will call, the height of its fall,
that is to say, the difference of temperature of the
bodies between which the exchange of caloric is
made"
The carnot efficiency equation results are "in fact" nothing more or less than the difference in temperature. How could any statement be framed more literally?
You make metion of "gravity".a couple times, highlighted above.
Things fall, not as a consequence of their own internal energy, do they? But as a consequence of an external force; gravity?
What is the force akin to gravity that compels heat to "flow" or to use your "analogy"
accelerate towards cold?
I my observations of various thermal phenomena, no such force exists.
Heat from my wood stove, warming the air around it, results in the hot air rising to the ceiling where it pretty much stays without calling upon the agency of a ceiling fan to drive it down. Warm water stays near the surface of the water. I've been swimming many times. The surface is warmer by the sun but the depths remain frigid, even through the night, while the water stays warm on the surface.
In my experience heat can be quite unruly and stubborn keeping to itself rather than rushing to some cold I might be attempting to heat up.
The force of gravity on the other hand is swift, acts quickly and predictably in one direction: down.
Heat does not fall straight down to a lower colder level. The random motion and collisions of gas particles, hot, cold or whatever travel willy nilly in any and all directions, no force compels them to travel one way or another like water is compelled by gravity to flow downward.
Water is not converted to work. Neither is heat.
Are you contradicting yourself now?
Earlier, not too much earlier, but just recently you wrote:
"The caloric/heat coming out of the bottom of a Carnot Engine contains less energy than that going in the top, as depicted by a change in temperature, as Carnot plainly explained in his papers. This is a result of being converted to work, and corresponding temperature drop. Lower entropy."
Now I'm confused, was that you expressing your own viewpoint or were you paraphrasing Carnot's plain explanation.
Or maybe just a case of whatever Tom says, say the opposite, because we don't really care about getting to the truth so much as just proving Tom wrong, or proving Carnot right.
At any rate the "clear explanation" seems a bit muddled IMO, a shifting sand of contradictions.
An engine is at best 20% efficient, whatever heat is supplied in Joules, only 20% can be converted, or, well, now no heat is converted, temperature is converted. Don't ask me how that works.
Anyway, 80% of the heat is "rejected" to the "cold reservoir". This is supposed to be an absolute, a LAW.
Heat cannot transfer between two things that are the same temperature and certainly not from colder to hotter, "spontaneously". So, logically for any heat to be "rejected" the cold side of the engine must always be at a higher temperature than the surroundings, if the engine is running.
Theories, opinions and absurd analogies and comparisons aside, how do we explain a heat engine that continues to run with absolutely no temperature increase on the cold side at all, with the path of the heat assumed to be leaving the cold side blocked by the best NASA type silicon aerogel, thermocouple, infrared readings ad so forth, sometimes showing instead a slight lowering of the temperature at the cold side.
One person in here, goofy, a guy with pretty impressive credentials says he has carried out some such experiments as well, and has encouraged others to do the same.
I guess that's something for all my years in here ranting and raving.
Do an actual experiment?
Nope, never, a waste of time.
You say:
The second law comes from observation and mathematics, and is not arbitrary
Really?
What observation?
This?:
try asking yourself, "why, in 200 years, no one has come even close to the efficiency of (Th -Tc)/Tc, let alone ne beat it?"
How can you beat a dictum? As VincentG wrote: "You can't beat a mathematical formula using the same formula"
If the ∆T is X then the Carnot efficiency is Y.
To make that assertion that "in 200 years, no one has come even close to the efficiency of (Th -Tc)/Tc, let alone ne beat it" you would need not only an iron clad reliable means of measuring the efficiency of any engine, it would also require that every engine ever built actually have its efficiency accurately measure by some alternative means.
Efficiency aside, where might the heat actually be going if such a large percentage most absolutely be "rejected". How does this "waste heat" manage to hide so well, remaining undetectable? How does it manage to penetrate any and all forms of insulation with no rise in temperature at the cold side of the engine?
It's very difficult to do good science
Oh how often I've head that on the physics forums.
Any REAL phenomenon is the stuff of high school demonstrations.
Water boils in a vacuum.
Easy peasy
https://youtu.be/I5mkf066p-U?si=r14vz2ypBgebyy2Q
Who has ever demonstrated the validity of the Carnot equation.
Not necessary, it's like a perfect circle! Just obvious, or science is really really hard.
No, actually, it's not that hard. It does take SOME actual effort though.