Do you use nitrogen?

[mtrv]

If temp goes up, pressure goes up.

Yes, but the statement is misleading. I'm going to use common refrigerent gasses for A/C units as an example.

R-22, which has been used for many years, will be running approx. 102 psi at 60 F. , while the new replacement freon, R410A will hit approx 170 psi at 60F. This is over 1 1/2 times the pressure, for the same identical temp. Increase the R-410A temp to 120F, and it's now 350psi, versus 260+ for the R-22. Needless to say, using freon, isn't the best for pumping tires that will tend to heat up, with some use.

These same differentials apply to Nitrogen and ordinary compressed air. However, I'm not in the mood to look up the exact differentials, so that I appear to be a walking encyclopedia. In the end, the pressure increase for nitrogen, as the temp. increases, will be less for nitrogen.

At least, I believe so! And no, I'm still not going to look up the exact differences.

 

[The_Russian]

Actually he did rip apart a few other posts, not just yours, however, you are the only one who can't admit that you were wrong.

What's wrong about my first post? Nitrogen does eventually freeze. I failed to state it would turn to liquid first. Am I the only one not taking crazy pills?

Nitrogen freezes at a lower temperature. It also retains a constant pressure over large temperature changes. On top of that it does not contain moisture, unlike the ambient outside air. If outside air is pumped into an aircraft that flies above the freezing level, the moisture within the air will freeze inside the tire. This can cause an imbalance or corrosion.

Also, aircraft tires are designed to resist nitrogen permeation though the carcass.

In its context for pilot information this is correct. If we get into the science of gas laws, the paragraph can be expanded on. If A Squared had the capacity to teach instead of insult, then he would have added constructive statements. Such as, "Russian, nice post. But I would like to add a few tidbits of info".

 

[wrxpilot]

Yes, but the statement is misleading. I'm going to use common refrigerent gasses for A/C units as an example.

R-22, which has been used for many years, will be running approx. 102 psi at 60 F. , while the new replacement freon, R410A will hit approx 170 psi at 60F. This is over 1 1/2 times the pressure, for the same identical temp. Increase the R-410A temp to 120F, and it's now 350psi, versus 260+ for the R-22. Needless to say, using freon, isn't the best for pumping tires that will tend to heat up, with some use.

These same differentials apply to Nitrogen and ordinary compressed air. However, I'm not in the mood to look up the exact differentials, so that I appear to be a walking encyclopedia.

Huh??

You're talking about a refrigerant system at particular operating temperatures and pressures. A very confused analogy to inflated tires. Your initial pressure for the tires will be whatever you set it at, regardless of temp. Here's how the gas laws work:

PV=nRT

Rearranges to P/T = nR/V

We're going to look at two different states of pressure/temperature:

P1/T1 = P2/T2
(n, R, and V cancel out as they are equivalent)

Initial conditions at Jim Bob's garage for the tire filling:
T1 = 20C = 293.1K, P1 = 80 psig

Now the tire is flying around in some airplane up really high:
T2 = -40C = 228.1K, P2 = ?

P2 = P1*T2/T1 = 62 psig

Notice there is nothing whatsoever related to the gas in the ideal gas law equation (Dry air and N2 are very close to being ideal gasses).

This is starting to sound like that stupid treadmill question, except this is even more ridiculous. Read the link I put on here earlier from Ingersoll-Rand.

After some reading, the benefits from Nitrogen are:
1)Reduced loss of pressure over time due to N2 having larger molecules than O2, which is apparently permeated through the rubber.

2)Reduced pressure differentials with temperature due to the lower water vaport content of pure N2.

Here's another link:
http://www.popularmechanics.com/automotive/sub_care_clinic/1272166.html?page=2&c=y

 

[mtrv]

Huh??

You're talking about a refrigerant system at particular operating temperatures and pressures. A very confused analogy to inflated tires. Your initial pressure for the tires will be whatever you set it at, regardless of temp. Here's how the gas laws work:

It's not confusing at all. In the days before high cost refrigerants, and the decision that some could lead to global warming; it wasn't uncommon to see a semi-flat tire pumped up with freon in an emergency; should you just happen to have some around. Just count on a rapid pressure increase, as the tire temp increases in road conditions, even though the initial pressure was at the tire rated pressure of 35 psi, at the particular ambiant temp. of the moment.

Now whip out your forumula's, and find the pressure increase for a racing tire thats been super heated since it's initial inflation. I want to see exact numbers comparing nitrogen & compressed air. Do nitrogen filled tires remain more stable in psi with increased temp ranges?

edit: I need to clarify this question slightly.

Since pressure does increase with temperature, then I can assume that the nitrogen filled racing tire is going to be cooler, than an air filled tire under the same racing conditions; which is the same as saying, that the nitrogen filled tire will have less pressure increase, as the outside ambient temps rise, while the vehicles sit motionless in the noon day sun.

 

[wrxpilot]

It's not confusing at all. In the days before high cost refrigerants, and the decision that some could lead to global warming; it wasn't uncommon to see a semi-flat tire pumped up with freon in an emergency; should you just happen to have some around. Just count on a rapid pressure increase, as the tire temp increases in road conditions, even though the initial pressure was at the tire rated pressure of 35 psi, at the particular ambiant temp. of the moment.

I think what you were seeing was the Freon expanding from a very high pressure tank to the relatively low tire. Expansion requires lots of heat, so the gas was very cold inside the tire. As it was driven around, it heated up such that there was a much bigger temperature difference than if it were air.

Now whip out your forumula's, and find the pressure increase for a racing tire thats been super heated since it's initial inflation. I want to see exact numbers comparing nitrogen & compressed air. Do nitrogen filled tires remain more stable in psi with increased temp ranges?

They do apparently remain more stable than the air ones, but still follow the ideal gas law. If the air was totally dry, they would both be very similar. The benefit you're getting is dryness - though I'd be surprised if there was any more than 5-10% difference. Water vapor is a very small component of the total pressure ratio.

edit: I need to clarify this question slightly.

Since pressure does increase with temperature, then I can assume that the nitrogen filled racing tire is going to be cooler, than an air filled tire under the same racing conditions; which is the same as saying, that the nitrogen filled tire will have less pressure increase, as the outside ambient temps rise, while the vehicles sit motionless in the noon day sun.

Not sure how the nitrogen filled tire is going to be cooler, you've lost me there. The tire heat is generated from friction between the tire and the road, and it is whatever it is.

 

[mtrv]

If A Squared had the capacity to teach instead of insult, then he would have added constructive statements. Such as, "Russian, nice post. But I would like to add a few tidbits of info".

It's just a person's way, of making them feel above the rest. Someone might have a solid background in physics; while another has mastered the art of language, and will forever use words that make little sense to the common man.

Yet, in both instances, these two people can be brought to their knees, should a third person be very learned in a subject these two are faintly familiar with. It can make them feel like asses, if the subject isn't changed.

But that's how it works! Speak with total authority on a subject you know, or can look up; and then remain silent on all those many other wonders of the world that will make you consistently look like a fool.

And P.S. --- I used spell check. Missed one word, but didn't want to look too stupid. Saved by the power of the internet!

 

[A Squared]

These same differentials apply to Nitrogen and ordinary compressed air.

That's just the point, the same differentials do *not* apply. The difference between nitrogen and oxygen is about 2% up to 10 atmospheres 150 psi. The difference between nitrogen and air will be even less.

I want to see exact numbers comparing nitrogen & compressed air

I've already posted fairly exact numbers comparing nitrogen and oxygen. Dry air being a mixture of nitrogen and oxygen (mostly nitrogen) will fall someplace in between.

Do nitrogen filled tires remain more stable in psi with increased temp ranges?

Actually, the numbers I posted showed that a nitrogen filled tire would have a slightly *less* stable pressure than one filled with oxygen. Again, dry air would presumably fall someplace between nitrogen and oxygen.

 

[A Squared]

What's wrong about my first post?

You have already been told, with complete explanations what is wrong. the Thing is, you are absolutely unwilling to consider that you are wrong, so you will not actually read what I have written and attempt to understand it.

Apparently your entire though process goes something like this:

"A Squared says I am wrong, and I won't consider that I am wrong, therefore A Squared is wrong."

WHatever gets you through the night, but it a pretty poor intellectual approach to life.

Nitrogen does eventually freeze. I failed to state it would turn to liquid first. Am I the only one not taking crazy pills?

No, you're the only one not reading and understanding what others have written. I have already explained it to you several times, It's pretty simple, I will explain one more time (anlthough for the life of me I don't know why I'm bothering)

ready?

OK. Of course Nitrogen freezs, *NOBODY* said it doesn't, not me, not anyone else. That wasn't the point. The point was this: the freezing point of the various gasses which make up dry air are so low, that it is ridiculous to mention freezing point of nitrogen in the context of an tire, even a tire on a high altitude aircraft. None of the gasses in dry air will freeze at any temperature that will ever be encountered in our atmosphere.



Also you were wrong that nitrogen "retains a constant pressure over large temperature changes" It doesn't. I've explained this, I've shown you the numbers, and you don't address anything that's been said, Instead, you just repeat that you are right, without offering anything to support your words.

Again, this appears to be because your entire though process is limited to:

"A Squared says I am wrong, and I won't consider that I am wrong, therefore A Squared is wrong."

As syllogism, it is badly flawed.

 

[aucfi]

I once used compressed Nitrogen to start a Yak 52.

Its true

 

[The_Russian]

It's just a person's way, of making them feel above the rest. Someone might have a solid background in physics; while another has mastered the art of language, and will forever use words that make little sense to the common man.

Yet, in both instances, these two people can be brought to their knees, should a third person be very learned in a subject these two are faintly familiar with. It can make them feel like asses, if the subject isn't changed.

But that's how it works! Speak with total authority on a subject you know, or can look up; and then remain silent on all those many other wonders of the world that will make you consistently look like a fool.

And P.S. --- I used spell check. Missed one word, but didn't want to look too stupid. Saved by the power of the internet!

Great post! Now we are just waiting for this third person....