[Xentry333]

I have a (relatively) simple question. Lets say we have an empty gas tank and we start filling it with a nitrogen. At some point (saturation), part of the nitrogen gas in the tank will turn into liquid and from then on, the pressure inside tank will not increase anymore, right? At what exact pressure will this happen, if we take into account the temperature of surroundings is 20C or 293K? I am interested in this because I need to know how strong the gas tank needs to be to fill it with liquid nitrogen. Thanks!

[curiouscat]

I have a (relatively) simple question. Lets say we have an empty gas tank and we start filling it with a nitrogen. At some point (saturation), part of the nitrogen gas in the tank will turn into liquid

No. Wrong. At room temperature no matter how high the pressure gets, you'll never liquefy N2. You are above Tc.

I am interested in this because I need to know how strong the gas tank needs to be to fill it with liquid nitrogen.

Please don't. You are risking disaster. You need a cryogenic dewar not a gas tank.

[magician4]

you can't have liquid nitrogen at or near room temperature:  critical temperature of nitrogen is  -146.9 °C (126.20 K )

regards

Ingo

[Tom1337]

I have a (relatively) simple question. Lets say we have an empty gas tank and we start filling it with a nitrogen. At some point (saturation), part of the nitrogen gas in the tank will turn into liquid

No. Wrong. At room temperature no matter how high the pressure gets, you'll never liquefy N2. You are above Tc.

I am interested in this because I need to know how strong the gas tank needs to be to fill it with liquid nitrogen.

Please don't. You are risking disaster. You need a cryogenic dewar not a gas tank.

I see, thanks. I tought that every gas turns into liquid if you rise the pressure enough.

Anyway, I have a tank that holds 12.6KG of R134a gas ... how much nitrogen can I fill in it without risk of explosion? The tank can handle max 47BAR or so.

[Tom1337]

you can't have liquid nitrogen at or near room temperature:  critical temperature of nitrogen is  -146.9 °C (126.20 K )

regards

Ingo

... so only gases that have critical point above room temperature can be "liquified" by raising pressure at room temperature?

[curiouscat]

Anyway, I have a tank that holds 12.6KG of R134a gas ... how much nitrogen can I fill in it without risk of explosion? The tank can handle max 47BAR or so.

Short answer: You can't

Long academic answer: ~2kg I suppose (risking an explosion still if ideal gas assumptions are wrong ). How big is the tank? (I assumed ~50 Litres)

Again, please don't put liquid N2 in a gas tank.

[Tom1337]

The tank has a capacity of 12.3 litres.

[magician4]

you can't have liquid nitrogen at or near room temperature:  critical temperature of nitrogen is  -146.9 °C (126.20 K )

regards

Ingo

... so only gases that have critical point above room temperature can be "liquified" by raising pressure at room temperature?

exactly


regards

Ingo

[curiouscat]

The tank has a capacity of 12.3 litres.

 ~600 gms says ideal gas law. But I really wouldn't risk it.

[Tom1337]

The tank has a capacity of 12.3 litres.

 ~600 gms says ideal gas law. But I really wouldn't risk it.

OK, I will try to put between 600 and 700 grams and see what happens. Thanks a lot!

[curiouscat]

OK, I will try to put between 600 and 700 grams and see what happens. Thanks a lot!

Boy, you are remarkably brave to trust your life to some quick calculation  I did. Have you considered the consequences of P rising above 47 bar? 

Well, at least wait for someone else on  here to chime in.

Does your cylinder have an operating relief disk / valve at least? What if the liq. N2 freezes it shut. What if the thermal shock causes a crack? Brittle fracture? What's your MOC? Do you realize how cold liq N2 is? How do you propose to fill liq. through a gas connector? (unless your tank was designed for liq. filling)

The  saftey part of my brain says "Never fill liquid into a gas cylinder", but if you want to still try go ahead. It's your explosion. 

[Tom1337]

Well, I'm sure that the tank has some "extra space" above that 47 bar ... and no, there is no relief valve, but I don't believe anything could go wrong, so I will go for it ...

[magician4]

please DOOOOOOOOON'T !


no such experiments with compressed gases storage!

use a certified bottle exclusively, a respective armature and all the bells an whistles...

... else you might be in a s**tload of trouble if anything went wrong

regards

Ingo

[curiouscat]

Well, I'm sure that the tank has some "extra space" above that 47 bar ... and no, there is no relief valve, but I don't believe anything could go wrong, so I will go for it ...

What code allows a 47 bar cylinder to be made without a relief valve? Maybe I am wrong.

The more I read this, the more I'm convinced you are playing with disaster.

[Tom1337]

Oh, come on, it can't be *THAT* dangerous. Besides, you never learn anything if you don't try something new.