Thread: Tanks for PCP
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Old 08-30-2014, 03:47 AM   #3
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Join Date: Mar 2012
Posts: 13

The reason behind the myth is that the 97.something cu. ft, so called 'rating' is calculated with Boyle's Ideal Gas Law...which states that a volume reduction results in a proportional change in pressure....for example, halve the volume and double the pressure...infinitely. reasonable analysis tells us that air molecules take up space and this Ideal behavior can not go on forever.

The air is slightly more compressible below 3,000 psi, and right on the Ideal line at that pressure, but is less compressible above 3000 psi. By 4500 psi, is is taking up about 13% more space than the Ideal Gas Law says it should...and so if there is only 550 ci to occupy at 4500 psi, there will only be 88 standard cu ft at atmospheric pressure crammed inside it, and not the 97.something the Ideal Gas Law would indicate( assuming the foolish assumption that air behaves as an ideal gas at 4500 psi was made ). A scientist by the name of van der Waals quantified the departure from Ideal Gas Law.
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