On Thu, 08 Jan 2004 01:13:24 -0600, Richard J Kinch
wrote:

Don Foreman writes:

If energy
out = energy in, then there's no net loss at the regulator.

Sez who? The "loss" is in the conversion of some of the useful-energy-in
into waste-heat-out and entropy-out. Whether this waste heat stays in
the regulator to raise its temperature, versus being carried downstream,
doesn't change the fact that the regulator directly caused the waste.

Remember that part of the loss is also in the form of work performed on the
ambient atmosphere, not heat.

What waste? Heat is still energy. If the downstream air is colder
than ambient then heat is not lost by conduction or radiation to
ambient, so that energy is still in the downstream gas.

Maybe we're getting closer to understanding, though. We've agreed
that a certain amount (mass) of air is compressed, and some heat is
lost in that process. Compression to higher pressure results in more
work being converted to heat (usually lost) at the compressor or in
the reservoir as that air cools by conduction to ambient -- and
perhaps a little radiation as well. But what about after that, as
in from just before the regulator to point of exhaust? I think that
was the original question.

Adding heat from the regulator to the air downstream of the
compressor will raise it's temperature above what it would otherwise
be, hence it's volume at regulated pressure, so less high-pressure air
will be required per unit volume of air at regulated pressure.

However, air exhausting to atmosphere from the point of use will
carry heat with it, the amount of heat depending on it's temperature.
The warmer the exhaust gas is (even if below ambient temp), the more
heat (hence energy) is lost by that route. Maybe *that's* where the
thus-far unaccounted-for energy goes.

I'll admit to being a bit disappointed that you, with your impressive
academic credentials, didn't clear this up many messages ago. It was
said somewhere along the line that I am incredibly stubborn. That's
true. I don't care a bit about "winning the argument" or "being
the one that's right" but I'm admittedly stubborn as hell about
persisting until I understand and continuing to question "expert
exhortations" until I understand. I have the greatest respect
for those who will teach and share, am not a bit impressed with
wizards who may know but can't or won't help others to know and
understand as well.

Perhaps my age is showing?