On Tue, 23 Dec 2003 16:34:25 -0600, Richard J Kinch wrote:
Gary Coffman writes:

Mathematically,
this has the same appearance as a dissipative resistance, but there
is *no dissipation*. Energy not used is simply retained in the tank.

Impossible.

We agree that mass flow (CFM) is conserved (equal) on either side of the
regulator.

We know: Power = CFM * pressure.

The regulator imposes: pressure (out) pressure (in).

Thus, since CFM is equal on both sides of the regulator, but pressure
decreases, there is a loss of power in the output compared to the input.

Power is not a conservative quantity. Energy is, and the energy not
released is retained in the tank. In other words, power = energy/time.
The regulator effectively changes (lengthens) the time over which a
given amount of energy is released from the tank. That does show
up as reduced output power. But power isn't what's conserved,
energy is, and it is retained in the tank until it is released.

This ends up as heat as a direct consequence of the restriction that
creates turbulence and lowers the pressure. This waste heat is mostly
added to the output flow, even though the output may be at a cooler
temperature due to expansion. Some of the power lost is hissing noise
that radiates away and also eventually becomes heat. None of this is
"visible" to the source, so it is not "simply retained in the tank".

Those parasitic losses are relatively negligible in a well designed system.

Gary