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>Posted on 21 Jun 1995 at 16:41:23 by AHDNN1A.DDRAKE01@ed*.co*

Good stuff deleted.

>... I.. don't think everything came out real clear.
As long as we are nitpicking:

I don't like the analogy to liquids because they come with additional
propeties like surface tension etc. A shaving blade can float practically
forever on water (the thermodynamic system is stuck in what is called
a metastable state): there isn't enough thermal energy available to
disturb the system out of the metastable state. Thermodyanamics
says that the system will reach equilibrium but it makes no gurantee
as to when it will happen. It could take forever.

>But time and agitation helps the "blending" process.
The question is though does rolling a tank qualify as agitation ?
For a dilute gas certainly not.  For a liquid yes. (Do remember though
that centrifuges are used to separate materials, not mix them :-) ).

I really don't know the relative importance with respect to mixing
of the disturbances due to the fill, rolling and the everpresent
thermal motion. My own feeling is that any reasonable fillrate will
cause way more mixing inside than both of the others.  However,
I know that by the time the fill hits 300 atm the gas is far from
ideal (pV=nRT) so maybe it takes on a souplike behaviour as far
as mixing goes at some fill pressure.

If I was outright wrong, which I might be, I would have expected
to see a few instances of the measured level of pO2 to drop
with time.  I am unaware of any data suggesting this has happened.

>Rolling tanks for 5 minutes does help.
Have you actually compared the numbers for a large number of fills ?

Now it is possible that the existing gas in the tank remain cold
for a while and lie low due to this.  If this is so it seems to me
the problem would be greatly reduced if the tanks were filled
"upside-down" (or rolled afterwards :-) ).

john
cc015012@br*.br*.ed*

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