On Tue, 06 Jan 2004 04:04:40 -0600, Richard J Kinch wrote:
Gary Coffman writes:

Now try it without the regulator. You can't do it as many times,
because energy stored in the tank has been *wasted* at each fill,
ie the pressure in the cylinder and tank equalize each time you
open the fill valve even though that's more energy than you *need*
to lift the weight one foot, and that excess energy is lost when you
vent the cylinder. This is a clear case where the *absence* of a
regulator wastes energy. It is in fact the *usual* case.

You are correct that with-the-regulator beats without-the-regulator, but
compressing-the-air-to-50-psi-to-start-with beats them both, which is to
say, if mechanical efficiency is the figure of merit, then a regulator on a
high-pressure supply is wasteful compared to an unregulated source at the
application pressure.

It isn't the regulator which is wasteful. The energy loss is in the compressor
you're asking to pump to a higher tank pressure. And no surprise, it is the
compressor which gets hot as it does so. *That's* where the energy loss in
your scenario occurs, not in the regulator. The regulator itself has nearly
zero loss, as my example of drawing down a filled tank to supply a load
shows.

Gary