Ned Simmons wrote:
In article ,
says...
On Sat, 27 Dec 2003 00:50:14 -0600, Richard J Kinch
wrote:


In general, regulation of *any power source* implies an inherent
waste versus the unregulated source: electrical power, compressed
air power, motive power, water behind a dam, etc.

So, if you draw 1 gallon of water a minute through a valve at the
base of a dam, the other 999,999,999,999,999 gallons in the
reservoir are wasted. Obviously not true at all. You use what you
use, the rest stays in the reservoir (with all of its potential
energy intact) until you need it.


Another faulty analogy. Since water is essentially
incompressible, the capacity of the water behind a dam to
do mechanical work is almost entirely due to its potential
energy -- its elevation in a gravitational field.

It's easy to demonstrate, without resorting to
thermodynamics, that air expanding thru a regulator loses
some of its capacity to do mechanical work, and that energy
does *not* remain in the air behind the regulator.

Explaining where the energy goes requires thermo.

Ned Simmons

I don't understand why this is not clear to everyone here. Which has more
energy- one liter of 200 psi gas or two liters of 100 psi gas? Can you do
any work going from one state to the other? In one direction you can, as
long as you don't just waste it with a regulator.

Putting it another way, as you compress a given volume of gas, does it have
more potential energy the more you compress it? Of course it does, so isn't
there a loss as it expands through a regulator?

The IR site makes it clear that it is inefficient to create higher pressure
than necessary and regulate it down. I believe this thread was started with
a reference to air for an HVLP gun. Using a high pressure compressor and an
HVLP conversion regulator is an extremely inefficient way to run an HVLP
gun. This can be confirmed by comparing the power use of low pressure
turbines and the compressor/regulator setup needed to duplicate the low
pressure, high volume needed.