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Re: [Phys-l] Reversible versus quasi-static processes (was Re: PV question)

On 01/24/2010 11:43 AM, John Mallinckrodt wrote:


Definition: A system undergoes a quasistatic process if and only if
no dissipation (or entropy production) occurs within the system.

I don't buy it.

"Static" has a well-established technical meaning.

"Quasistatic" has heretofore meant "almost static"
... which seems sensible and unsurprising. This
definition has always worked for me, and I cannot
imagine why anybody would propose any change, let
alone a highly counterintuitive change.

If you want an example of a physical process that
is quasistatic but clearly dissipative, consider
Joule-Thomson expansion through a porous plug.


It seems to me that the confusion arises as a result of a very common
failure to be clear about 1) the central role of dissipation and
entropy production and ...

We agree that in addition to the usual amazing
amount of confusion about basic thermodynamics,
there is an amazing-squared amount of confusion
about irreversible processes.

Dissipation happens.

Any serious theory of thermodynamics must include
irreversible thermodynamics.