Talk:Reversible process (thermodynamics)

message: In at least one textbook I've seen (Engineering Thermodynamics by Cengel and Boles), they use two terms to discuss reversibility: totally reversible and internally reversible. The Wikipedia article here is only the "totally reversible" half of the equation. Internally reversible is given a similar definition, but without the requirement that the reverse path must be done without the environment changing. The upshot is that an internally reversible path is basically any path that can be drawn on a P-V diagram because it's in thermal equilibrium the whole time (as opposed to a "free expansion", for example). 
That may be useful to add to this article--that some people refer to what's presented in this article as being "totally reversible", and that there's sometimes a separate "internally reversible" condition.
Johncolton (talk) 21:47, 19 September 2012 (UTC)
replies: text: I agree. Do you mean Thermodynamics, An Engineering Approach by Çengel and Boles? Reading the book (5e), I think internally reversible is the same as quasi-static, but the book doesn't state it that clearly; "The quasi-equilibrium process is an example of an internally reversible process." Yodo9000 (talk) 18:47, 8 November 2022 (UTC)
thread_title:  Totally reversible vs. internally reversible 

message: In here, it says:
" Reversible processes are a means of allowing entropy to be a state function, where a state function is something that does not rely on the pathway that it took to determine its quantitative value. "
In irreversible process, it says:
" However, because entropy is a state function, the change in entropy of a system is the same whether the process is reversible or irreversible. "
Entropy is strong in this one  — Preceding unsigned comment added by 78.162.22.9 (talk) 06:14, 19 March 2014 (UTC)
thread_title:  Inconsistency: allow entropy to be a state function OR allow process to be irreversible??????? 

message: Following Klaus Schmidt-Rohr's  which described the process as being done on the surrounding rather than the system, I thought I'd open up a discussion here. I already edited the page in a manner that somewhat reverts this, but still leaves a reference to the surrounding, as I think the main focus in any process is the system (by definition of what we call the system). Would be happy for input.
Kwikwag (talk) 14:27, 5 May 2016 (UTC)
replies: text: I agree with Klaus Schmidt-Rohr's edit. He did not actually say that the process is done on the surroundings, and in fact the process involves changes in both system and surroundings. What he did say is that the reversal of process direction is due to a small change in the surroundings rather than of the system. Actually the direction of a process can be reversed by either type of change: for example if initially the system pressure is 1.000 atm and the external pressure is 0.999 atm, then we have an expansion which can changed to a contraction either by changing the system to 0.998 atm or by changing the external pressure to 1.001 atm. However what is of interest is reversing the direction at the given state of the system, which is accomplished only by changing the external pressure. Therefore I believe the word surroundings is required after infinitesimal changes in some property of the.  Dirac66 (talk) 20:47, 5 May 2016 (UTC)
thread_title:  Change to system or surroundings 

message: In the first paragraph, "Since it would take an infinite amount of time for the reversible process to finish, perfectly reversible processes are impossible."
I do not see anywhere prior to that statement the supporting claim or explanation that it would take an "infinite amount of time".  Why would it?  How do we know that it would?  The timing of this process needs to be established before this claim -- which lacking any context appears absurd -- can be made.  — Preceding unsigned comment added by 70.89.176.249 (talk) 01:29, 22 February 2020 (UTC)
thread_title:  It would?  Why?