Timeline for In the isothermal expansion phase of a Carnot cycle, why does the gas expand?
Current License: CC BY-SA 4.0
9 events
| when toggle format | what | by | license | comment | |
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| Jan 16, 2020 at 15:04 | vote | accept | JPM | ||
| Jan 16, 2020 at 15:00 | comment | added | Bob D | @JPM Bottom line is you do need a temperature difference for heat transfer. It is because of this that the Carnot efficiency based on no difference in temperature represents an upper limit that in actuality can never be reached. | |
| Jan 16, 2020 at 14:44 | comment | added | JPM | Indeed. I am studying the developments from Carnot through Clapeyron to Mayer, Clausius, Thomson (Lord Kelvin), and Joule. When Thomson still accepted caloric, he had “let the piston rise” and “the piston is allowed to rise,” sounding as if he thought it just would. I don’t see him change that after he accepted Joule’s kinetic theory. And though he does use calculus, I don’t see him discuss any infinitesimal temperature difference there. — All these guys were still thinking of real steam engines they saw around them. It’s remarkable what progress they made while still figuring things out. | |
| Jan 16, 2020 at 13:11 | comment | added | Bob D | To quote from an MIT website “What makes his accomplishments all the more remarkable is the fact that the nature of heat itself was not understood until long after Carnot’s death. At the time of his research, scientists still subscribed to the later discredited “caloric” theory of heat, which held that an invisible fluid of that name carried heat from one object to another.” | |
| Jan 16, 2020 at 13:10 | comment | added | Bob D | @JPM Your link is an excerpt from his book "Reflections on the Motive Power of Fire". I have a pdf copy. Fascinating reading. But if you read the rest you will find Carnot and his contemporaries did not know that heat is energy transfer due solely to temperature difference. | |
| Jan 16, 2020 at 1:20 | comment | added | JPM | en.wikisource.org/wiki/… | |
| Jan 16, 2020 at 0:30 | comment | added | Bob D | @JPM I really don't think Carnot actually meant heat transfer could occur if the air is EXACTLY "at the same temperature as a body A". But please cite your reference in order that I can see it in the exact context of your quote. | |
| Jan 15, 2020 at 23:41 | comment | added | JPM | It looks like much of my problem is the difference between what Carnot himself wrote in 1824 and how we (should) think of it. He has: “The air becomes by such contact of the same temperature as the body A . . . . The piston gradually rises . . . . The body A is all the time in contact with the air, which is thus kept at a constant temperature during the rarefaction.” He makes no use of integral calculus. | |
| Jan 15, 2020 at 20:54 | history | answered | Bob D | CC BY-SA 4.0 |