On Tue, 06 Jan 2004 03:24:22 -0600, Richard J Kinch
wrote:

Don Foreman writes:

I've always thought of temperature as proportional to heat content in
joules or calories times specific heat of the material holding it.

If that were always true, you couldn't have air conditioning, or an ice
cold drink.

You're right. I was thinking only of the metal in the regulator when
we said "the regulator gets cold".

However, if the regulator is colder than ambient then it is not
dissipating energy as heat. (If anything it's recovering some heat
from the environment, some of which was put there at the compressor
during compression.) If the regulator isn't losing energy to the
environment in the form of heat, then all energy coming in with the
high pressure gas must be going out with the lower-pressure gas --
so where's the loss in the regulator?