Re: entropy - motivation for definition

[Bob LaMontagne <rlamont@POSTOFFICE.PROVIDENCE.EDU>]

For lack of time, I'll just give a quick example:
Isentropic flow of an incompressible fluid. A simple
analysis of the entropy flow equation for a control volume
gives that the work done by a pump driving the fluid is the
sum flow work (v delta p), kinetic energy change and
potential energy change. That's a use of entropy that
hardly fits a statistical mechanics approach. I don't think
this really qualifies as something an engineer doesn't
"need" to know.

 From meteorology: The  Potential Temperature of a parcel of
air is an isentropic parameter. Statistical analysis
doesn't give insight into this quantity - traditional Q/T
does.

Again, I have no problem with using statistical mechanics,
my comment was simply about using techniques appropriate to
the audience. To decide as physicists that our way is the
only way to do things smacks of arrogance.

Bob at PC

*********** REPLY SEPARATOR  ***********

On 4/5/2004 at 12:43 PM John Denker wrote:

> Bob LaMontagne wrote:
> > A minor protest here!
> > Teaching thermodynamics to engineers (vs. physicists)
> > solely by using statistical mechanics may be an
interesting
> > exercise, but I'm not sure it helps them understand the
> > thermodynamics of ductwork. If you're teaching a service
> > course to engineers or chemists you have to respect the
> > needs of your audience.
>
> 1) Who said anything about "solely"?
>
> 2) The "ductwork" remark seems over-the-top.  The folks
who
> do ductwork don't need to know anything about entropy in
> particular or thermodynamics in general.  Knowing that
> energy is conserved and heat is a form of energy is more
> than they "need" to know, and hardly counts as
thermodynamics.
> So maybe they shouldn't be taking the course at all.
>
> 3) What sort of "engineers" are we talking about?
Forsooth,
> civil engineers can build bridges without knowing anything
about
> thermo.  So maybe they shouldn't be taking the course
either.
> 4) One can easily prove (by exhibiting examples) that it
is
> sometimes possible to have a long career in academic
chemistry
> without having any real understanding of what entropy is.
So
> evidently some chem majors don't "need" to study thermo at
all.
> 5) I can *show* people entropy in the form of a tray full
of
> coins, having one bit of entropy per particle (i.e. 5.76
> joules per kelvin per mole).  If you're going to do thermo
> at all, this is the easy way to get started.
>
> 6) Rather than a "minor protest", could we please have
some
> constructive suggestions as to what should be taught to
whom,
> and how it should be taught?