Re: [CAD_CAM_EDM_DRO] OT: Cubic Feet in a Compressed Gas Cylinder?

Tim Goldstein wrote:

> Totally off topic, but I though someone on the list might know how to
> figure
> this.
>
> I am looking to be able to calculate the number of cubic feet of gas
> at
> standard atmospheric pressure that are in a cylinder at any given
> time. The
> 2 scenarios are:
>
> If I know the rated capacity of a cylinder at a given pressure How do
> I
> calculate the remaining cubic feet at a different pressure. As an
> example,
> if I have a cylinder that is rated to hold 219 cubic feet at 2080 psi,
> how
> many cubic feet does it hold at 500 psi or any other pressure?
>
> If I know the internal volume of a cylinder how can I calculate the
> capacity
> in cubic feet at 100 psi? As an example, if I have a cylinder that has
> a
> calculated internal volume of 3.5 cubic feet, how much gas can it hold
> at
> 100 psi.

Assuming an ideal gas (most are VERY close) it scales linearly, relative
to absolute
pressure. So, if you know how many cubic feet the tank holds at STP,
then at
100 x that pressure, it will hold very nearly 100 x that many Cu. Ft.
So, for the above
example, at 100 PSI (gauge) that is 115 PSI absolute, therefore 115 / 15
= 7.667, and
7.667 x 3.5 = 26.833 cu Ft.

for the earlier example, you have 219 cu ft capacity at 2095 PSIA, and
the tank now is at
515 PSIA. So 515 / 2095 = .2458 of full. .2458 x 219 = 53.84 cu ft
remaining.

Jon