RESULTS==CAN Nitrogen be used in place of CA in Steyr Air

[Steve Swartz]

But the gas constant is different for different gases (hmmm . . . then we should call it the "gas variable?" anyhow).

Pure Nitrogen has better (not by much) characteristics than "mixed atmosphere." Especially if the "mixed atmosphere" contains water vapor.

I think it's much ado about nothing- unless, of course, you have a problem finding a reliable source of dry air.

Steve

[bubba_zenetti]

Walter wrote:
Race car drivers often use Nitrogen in their tires because it does not expand when temperatures increase.

I assume that race car drivers have somehow been able to invalidate the laws of physics -- the last time I did gas equations, it was still PV=nRT and that applies to all gasses. (What this says is pressure time volume is equal to a constant times temperature; temperature goes up, then pressure and/or volume must increase, too.)

Best,

Joe

you would be correct. nitrogen does expand just like any other gas when subjected to heat. however the rate of expansion on nitrogen is far less than our mixed atmophere. this is why race car drivers use it becuase the amount of heat required to make it expand to the point where pressue in the tires change noticably is much higher than the amount needed to make a normal atmopheric mix expand. this temprature is a bit beyond the temprature of the tires when they are fully warmed up.

the same goes for suspensions. the nitrogen sac in a gas charged shock or damper is less prone to drastic pressure increases from heat keeping damping control more consistant.

filling a pre charged air pistol with nitrogen would mean that the pressure in the vessle would be more stable under heat. however with most air pistols of this type, there is some sort of regulator that keeps the pressure from each shot the same(so i have been told) so it may not be of any benifit to use it for that purpose.

[iow]

For those who might not know , nitrogen , rather than CA is also now commonly used as the propellant to charge & recharge certain types of fire extinguishers ( eg. water or foam ). Therefore all decent fire equipment servicing companies will carry it , so nitrogen is not that difficult to obtain.

Len

[RobStubbs]

I seem to recall that was the original issue. The guy could get hold of nitrogen but compressed air was almost impossible for him to get.

Rob.

[Guest]

you forgot the crucial assumption when pv=nrt is used. the gas must be ideal.

for a real gas it would mean low pressures and high temperature. both of which do not apply to air in a cylinder. so the equation is invalid and if used would not be able to predict anything accurately.

[ChrisL]

I see very few advantages to move to N2, except:

-availability in particular cases
-slightly more efficient (due to lower density)
-if pure, by definition dryer than air
-perhaps less corrosive due to lack of oxygen

Ar should be slightly less efficien than air, due to the slightly higher density, and the consequent lower velocity of sound.

But I think the issue in AP is consistent velocity, and while muzzle veocities may change using a different gas, I think it's an illusion to believe that there is much to be gained using a different gas.

BTW, apart from Argon, the others definitely are not Ideal Gases, so PV=nRT is only an approximation...

My 2 cts.