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

ptengin@... wrote:

> In a message dated 08/13/2000 7:21:30 AM Hawaiian Standard Time,
> prototype@... writes:
>
> << > 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.
> >
> Depends on the gas. Helium, argon and other "ideal" gasses compress in
> linear relation to the pressure. Thus, volume is essentially proportional
> to pressure - up to a point, which bottled gas is well below.
>
> If it's oxygen, nitrogen, CO2 or most other gasses then you have a different
> problem altogether. Oxygen is fairly linear up to about five atmospheres
> (75 psia). Nitrogen and CO2 are not even close and for these you need
> either a set of gas tables or a curve fit equation to do the calculations
> you are after. >>
>
> Which reminds me, propane and Lng have a very different curve due to low
> vapor pressure. I think Freon and some of the other propellant gases have the
> similar qualities.
>
> Peter
> THRD, Inc.
>
> Don't know if attachment work or not. However attached is a short C program for common gases.

Some are linear ( pretty much constant slope but the slope may not be 1.0) others e.g. CO2 are pretty wild.

Dave


----------

/* calc non-ideal gas pressures
try using enum for gases */

#include </usr/include/stdio.h>
#include </usr/include/stdlib.h>
#include </usr/include/math.h>


main( unsigned argc , char **argv)
{
float P, R, T, V, n;
float a[5] = { 0.244, 0.03412, 1.39, 1.36, 3.59 } , b[5] = { 0.0266, 0.0237, 0.0391, 0.0318, 0.0427 };
/* where P = pressure
R = Boltzmann constant
T = temp (K)
V = volume
n = gm/mols gas
a = van der Waals (1)
b = van der Waals (2)
*/
int i;
enum gas_type { H, He, N, O, CO2 };
enum gas_type gas;


gas = CO2;
V = 22.4;
T = 273.0;
R = 0.082;

n = 10.0;
do {
P = (n*R*T)/(V-n*b[gas]) - (n*n*a[gas])/(V*V);

printf( " %f %f %f \n", n, P, P/n );
n += 10.0;
}
while( P <= 200.0 );
exit(0);
}


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