Meaning of "adiabatic" in Britain?

[George Jones]

I recently have discovered that the thermodynamics term "adiabatic" seem to be used slightly differently in Britain than it is in North America.

What does "adiabatic" mean in Britain?

 

[CAF123]

I was not aware of any differences in the term. In the context of thermodynamics, an adiabatic process is one in which there is no heat transfer over the system/surroundings boundary. The Oxford dictionary has a similar definition, see http://www.oxforddictionaries.com/definition/english/adiabatic .

Where did you hear about a difference?

 

[George Jones]

I am curious about how folks will respond, so, in order not to bias responses, I am going to be coy for now, and not state what I have read, but I have seen the same thing twice, once in a grad-level text.

 

[D H]

This site, http://www.damtp.cam.ac.uk/user/tong/statphys.html, has lecture notes from David Tong's "introductory course on statistical mechanics and thermodynamics given to final year undergraduates." He appears to use "adiabatic" in two different ways in the fourth part of his lecture notes, http://www.damtp.cam.ac.uk/user/tong/statphys/four.pdf.

He defines "adiabatic walls" as something that completely isolates a system from all outside influences. Then he writes about adiabatic compression and expansion in terms of a Carnot cycle. Then he writes about adiabatic processes as ones that don't exchange heat with the environment. So far, so good. It appears that there is no difference between the word adiabatic in US and UK usage.

But then he writes about adiabatic surfaces where those in the US would use the word isentropic instead. It appears that a few other UK sites also use adiabatic where we would use isentropic.

 

[CAF123]

But then he writes about adiabatic surfaces where those in the US would use the word isentropic instead. It appears that a few other UK sites also use adiabatic where we would use isentropic.

There is a quantity of interest in oceanography called, confusingly, the adiabatic lapse rate defined as $(\partial T/\partial P)_S$ even though the thermodynamic derivative is isentropic or at constant entropy. Ofcourse, the latter term is more appropriate.

 

[boneh3ad]

I've only ever heard it used one way among my American and British colleagues. Maybe it varies somewhat by field?

 

[D H]

There is a quantity of interest in oceanography called, confusingly, the adiabatic lapse rate defined as $(\partial T/\partial P)_S$ even though the thermodynamic derivative is isentropic or at constant entropy. Ofcourse, the latter term is more appropriate.

IIRC, the adiabatic lapse rate is defined as $(\partial T/\partial z)_Q$, in other words, change in temperature with elevation given no heat transfer. (Compare the environmental lapse rate, $dT/dz$ in the "real" atmosphere.)

 

[George Jones]

I was not aware of any differences in the term. In the context of thermodynamics, an adiabatic process is one in which there is no heat transfer over the system/surroundings boundary. The Oxford dictionary has a similar definition, see http://www.oxforddictionaries.com/definition/english/adiabatic .

Where did you hear about a difference?

I just found another reference ,

From the first book: 'We define a change to be adiabatic if it is both adiathermal and reversible

In his book "Cosmological Physics", John Peacock writes (Peacock's bold)

The expansion is clearly adiathermal, since the symmetry means that there can be no net heat flow through any surface. If the expansion is also reversible, then we can go one step further, because entropy change is defined in terms of the heat that flows during a reversible change. If no heat flows during a reversible change, then entropy must be conserved, and the expansion will be adiabatic.

The other reference I had in mind was

A process is called adiathermal if there is no heat flux from the surroundings during it. A process is called adiabatic if it is both adiathermal and also \Delta S = 0.

In all of these, adiathermal seems to mean what I would call adiabatic, and adiabatic seems to mean what I call isentropic.

 

[WannabeNewton]

In "Elements of Classical Thermodynamics for Advanced Students of Physics" by A.B. Pippard, who was a professor in Cambridge at the time the book was engendered (1957), the term adiabatic is used to refer to reversible adiathermal ($Q =0$) changes i.e. a quasi-static process for which $\delta Q = 0 \Leftrightarrow dS =0$. Pippard also writes in a footnote that "Some writers prefer to use adiabatic in the sense of our adiathermal, and to call our adiabatic change a reversible adiabatic or isentropic change." (p.31) so there do seem to be inconsistencies in the literature even amongst the British authors.

P.S. this is an amazing book on thermodynamics that you should definitely buy; it's quite cheap!

 

[D H]

Aha!

Here's a couple more textbooks and a journal article that use "adiathermal":

Blundell and Blundell, Concepts in Thermal Physics, Oxford University Press (2006).
McIlveen, Fundamentals of Weather and Climate, Oxford University Press (2010).
Callendar, "III. On the thermodynamical correction of the gas-thermometer." The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science 5:25 48-95 (1903).

 

[CAF123]

In his book "Cosmological Physics", John Peacock writes (Peacock's bold)

That seems to be the same John Peacock who is a professor of cosmology at the university I attend. I guess one needs to specify how they are defining their terms. For example, with that reference of the adiabatic lapse rate, a piece of follow-up text was explaining that an adiabatic process is not necessarily isentropic. So clearly here they were meaning 'adiabatic' here to mean 'adiathermal' in the terms used in those books.

 

[Philip Wood]

Edit: I've belatedly read WannabeNewton's post (above). Sorry about the repetition.

A B Pippard’s Classical Thermodynamics (1957) is an acknowledged British classic. Here are the relevant passages…

"For any system, in an adiathermal process, i.e. one performed by means of work on an otherwise isolated system, ΔU = W." (1964 ed, p 16)

"[…] we shall be closely concerned with adiabatic changes, that is reversible adiathermal changes […]" (1964 ed. p 31)

But he says in a footnote…
"Some writers prefer to use adaiabatic in the sense of our adiathermal, and to call our adiabatic change a reversible adiabatic or isentropic change."

For the little it's worth, this is my own (British) preference. I never use the word 'adiathermal'. [Maybe I'm unconsciously following the usage in that great American textbook, M W Zemansky's Heat and thermodynamics!]

Etymology doesn't support a distinction: adiabatic means "doesn't go through" and "adiathermal" means "heat doesn't [go] through"!