Helium in tires: how does it contract and expand?
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From: Dallas
From what I hear helium is a bad idea for tires. Apparently the molecules are so small that it will escape the tire much in the same way it escapes a balloon. Many racers use Nitrogen in their tires however since it resists moisture better than normal air and it does not expand and contract as much with temperature change.
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From: Longmont, CO
Mylar baloons last freakin forever - the deflation rate is almost non-existent - and it's really light. I wonder if lining the interior of the tire with mylar would reasonably allow helium to be used...
Oh, and given the gas law PV=nRT, while helium and nitrogen will have different weights under identical conditions (Pressure, Volume and Temperature), they will still have the same number of moles and will be effected by temp changes identically. (Ie, double the temp on either, and they will both double their pressure given a constant volume.)
Oh, and given the gas law PV=nRT, while helium and nitrogen will have different weights under identical conditions (Pressure, Volume and Temperature), they will still have the same number of moles and will be effected by temp changes identically. (Ie, double the temp on either, and they will both double their pressure given a constant volume.)
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From: Santa Clara
Elistan,
Wrong. PV = nkT is the ideal gas law, which is derived from first principles as the statistics of massive particles that have no potential interactions and undergo fully elastic collisions. Neither oxygen, nitrogen, nor helium are, in fact, ideal gases, and behave in only approximately the same way under pressure. Please read up on "compressibility" and "Z-factors" and how the concepts apply to gases under pressure.
However, in the range of tire pressures, say 30-50 psig, the effects of compressibility are remarkably small (negligible). For the most part, air, nitrogren, and helium all behave basically the same way in terms of pressure and density at low absolute pressures. The use of nitrogen, as has been said, is due to issues of moisture and oxidation, neither of which are desirable in a high-stress environment like a tire. The use of helium, as has been said, is contraindicted by the fact that the helium will leak directly though the tire.
- Warren
Wrong. PV = nkT is the ideal gas law, which is derived from first principles as the statistics of massive particles that have no potential interactions and undergo fully elastic collisions. Neither oxygen, nitrogen, nor helium are, in fact, ideal gases, and behave in only approximately the same way under pressure. Please read up on "compressibility" and "Z-factors" and how the concepts apply to gases under pressure.
However, in the range of tire pressures, say 30-50 psig, the effects of compressibility are remarkably small (negligible). For the most part, air, nitrogren, and helium all behave basically the same way in terms of pressure and density at low absolute pressures. The use of nitrogen, as has been said, is due to issues of moisture and oxidation, neither of which are desirable in a high-stress environment like a tire. The use of helium, as has been said, is contraindicted by the fact that the helium will leak directly though the tire.
- Warren
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From: Longmont, CO
Originally posted by chroot
However, in the range of tire pressures, say 30-50 psig, the effects of compressibility are remarkably small (negligible).
However, in the range of tire pressures, say 30-50 psig, the effects of compressibility are remarkably small (negligible).
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Gernby
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Dec 6, 2004 10:23 AM