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>Posted on 3 Nov 1995 at 13:27:05 by Christopher M. Parrett

>The current model makes several "Wrong" assumptions, but we have to
>put in some numbers.

I'm not sure you are making any wrong assumptions as much as you
are doing some kind of a slam-bam fill where you ignore the final
fill pressure after the tank has cooled down.  As you calculate
the mols needed ahead of the fill, your only error in the *mix*
(barring a conceptual/programming error) stems from not knowing the
temperature in the tank.  This is so because you terminate the fill
on pressure and *not* by counting molecules.

This was the point I tried to make initially, namely that the
pressure-temperature relationship depends only on the density and
not the true volume of the tank. I.e., I can get my mixtures right
even if I fill an entire submarine just by monitoring the pressure
and temperature.  Granted I don't know the temperature but I'm patient,
I just wait a day or two before I do the pressure measurement and
I assume then that the gas is at seatemp.  Also, the bigger the tank
the smaller the surface area per kg of gas so the error gets
smaller the bigger the tank (the theoretical rise in gas temp
is more likely to be in agreement with reality).


I'll tone down my contributions now as I realize that a
slew of other complex issues and points are begging for
airtime.  At a minimum I want to be amply rewared if I
am to continue making a commercial product fly :-).

Mail me if interested.


john

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