On Mon, 12 Jan 2004 00:08:32 -0600, Richard J Kinch
wrote:

Don Foreman writes:

There is
no work done on the atmosphere until the air leaves the system at
point of use.

If it is expanding out of a regulator, the volume must be displaced
*somewhere*, either in the "system" or out of it or some of both. If
the "system" includes, say, another expanding reservoir (an expanding
air cylinder or balloon), then the work is done on the atmosphere
although the air is still in the "system".

If the "system" ends in an ordinary tool with an exhaust port, then,
yes, the extra expansion energy is not all disspated as heat but partly
as work against the atmosphere (which globally just got bigger by that
much volume).

That works the same with or without a regulator.

I therefore submit that available energy
lost in the regulator is converted to heat (albeit at lower
temperature because there has been expansion).

Uh, that was my point. Friction, turbulence, sonic noise, all end up as
heat. In theory you could have a perfect regulator that emitted no
noise or turbulence, that worked entirely on friction, something like a
perfectly muffled turbine air motor coupled to a brake.

The brake would get hot and dissipate to ambient while the regulator
does not. A regulator does work almost entirely on viscous friction,
The question continues to be where the energy goes since the regulator
does not get not. To get it right you must deal with entropy and
available energy. Any irreversale process, by definition, involves
an increase in entropy. Expansion of air thru an orifice as in a
regulator is definitely an irreversable process so entropy is
increased. That's where the energy goes: out the exhaust port as
heat energy unavailable for doing useful work. It is NOT lost in
the regulator, total energy is preserved, but the regulator does
increase entropy and therefore reduces available energy downstream.

Bottom line is less power to the tool. I just wanted to understand
why. I think I do now so I'll shut up. I've learned a lot here.