can liquid nitrogen be reliable?

[jonyutah]

just wondering if anyone has seen or heard of a closed liquid nitrogen system? Like phase change. I realize that it is very impracticle. In theory can it be done? what would it take?

[Phant0m51]

I think you'd need some way to keep the liquid nitrogen from heating up to room temperature or higher. Liquid nitrogen won't just stay cold. Take a cube of ice and put it in a sealed cup. It'll melt. Same thing with liquid nitrogen, it'll get warm.

If you had the machines to keep liquid nitrogen that cold, you wouldn't need liquid nitrogen for your computer...

[bigben2k]

Liquid nitrogen is made by compressing nitrogen, then letting the liquid cool to room temp (it gets hot). Then by releasing the pressure, it becomes cold very fast, hence liquid nitrogen.

And yeah, if you had that compressor, you wouldn't need liquid nitrogen.

[pHaestus]

I use instruments all the time whose detectors are liquid N2 cooled, and I believe that ICP instruments usually have a direct feed to a pressurized liquid N2 tank for cooling. I dunno if a special permit is required to get tanks delivered to your home or not though

[hydrogen18]

there is a plus side, releasing nitrogen into the air is helpful to the enviroment I beleive, as it speeds along the human interrupted nitrogen cycle in the wilderness. But why cant nitrogen be used like any other refrigerant?

[Zhentar]

Because of the extreme temperatures involved. Its boiling point is way too low, so the pressure and such required is impractical.

[pHaestus]

77K's not too bad.

[jonyutah]

how much compression are we talking about here to change nitrogen from gas to liquid? at room temperature I assume.

[sevisehda]

I'm not postive on this but I think its about 1500 PSI.

[jonyutah]

how in the world am i going to produce 1500psi? Let alone inside a case. Anything short of a controlled explosion will not produce that much presure. maybe the presure from a small nuclear reaction within my case. i could store the resultant gas in a titanium case slowly letting out 1500psi as i needed it over the course of the next 10 years! i just need to top up on plutonium and uranium every 10 years or so and im set. SAFTY might be a small factor to contend with as a leak would most likely lead to the the destruction of Calgary and my untimely demise. Still a small price to pay for a the ultimate cooler.:shrug:

OK seriously though, is there a way to store liquid nitrogen until ready to use? maybe a valve controlled by a thermostat to reintroduce more into the system as needed?

[utabintarbo]

Originally posted by jonyutah
.... i could store the resultant gas in a titanium case slowly letting out 1500psi as i needed it over the course of the next 10 years! i just need to top up on plutonium and uranium every 10 years or so and im set. SAFTY might be a small factor to contend with as a leak would most likely lead to the the destruction of Calgary and my untimely demise. Still a small price to pay for a the ultimate cooler.:shrug:

...

There's always antimatter!

[Zhentar]

I'd imagine antimatter would also lead to his and his city's untimely demise.

Not to mention building a particle accelerator would be kinda expensive....

[N8]

I order and use thousands of gallons of LN here at work all the time. The pressure containers that they are stored in have an active venting system. The LN evaporates ALL THE TIME, even when under pressure, and you HAVE to have a venting system otherwise the holding tank will explode violently. LN cannot be used in a closed loop for these reasons. After time, the LN will totally evaporate out of the venting system, even if I never take any liquid out.

The whole reason LN even works to cool anything down is because of the nature of this reaction.


Let me end this LN discussion, and hopefully any other LN questions for the rest of eternity with this statement:

"Forget about LN as an everyday coolant unless you have thousands of dollars and the time to spend on replenishing and refilling containers every couple of hours. LN is only useful for time limited experimentation."

I will not waste my time responding to any questions regarding the usage of LN at this point.

[jonyutah]

guess i'll get to work on that particle accelerator:shrug:

[bigben2k]

Originally posted by jonyutah
how in the world am i going to produce 1500psi?

(the following is meant as a joke, OK!)

Given that a refrigerator compressor can reach 300 psi, you can hook 5 of them up in series, pray to your prefered deity that nothing is going to blow, and walk away very quietly.

When it blows (and it will), you won't need any AC in the house for several hours, possibly a whole day. Your PC will be permafrosted.

[jonyutah]

I think while im building my particle accelerator I can work on a a mater-antimater containment field and get some warp engines to power my rig. anyone know where I can pick up dilithium crystals?

[ezlid]

Originally posted by jonyutah
what would it take?

Only $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$ $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$ $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$ $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$ $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$ $$$$$$$$$$.

Crap, you're in Canada. $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$ $$

That will do it - lol

And when you build it you can have a sperm bank and body repository on the side to cover the ongoing cost of cooling your $1000 - er .. $1200 computer. lol

[redleader]

there is a plus side, releasing nitrogen into the air is helpful to the enviroment I beleive, as it speeds along the human interrupted nitrogen cycle in the wilderness. But why cant nitrogen be used like any other refrigerant?

The Earth's atmosphere is almost all Nitrogen with a little oxygen and traces of water + CO2 + Argon. The nitrogen cycle refers to ionic nitrogen + hydrogen compounds like ammonium nitrate needed by plants.

Anyway LN2 is pretty cheap stuff. Chem majors throw the stuff around because its virtually worthless. It is, however, difficult to store which makes it impractical for us to use

[mfpmax]

Originally posted by ezlid


Crap, you're in Canada. $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$ $$

Got it wrong...Canadians would require more money

[hydrogen18]

i didnt know LN2 evaporates even when sealed...is this because of its molecular size allowing it to vent thru its container? Anyhow bigben2k has given me a cool idea, whats the freezing temp of mineral oil?

[sevisehda]

If your thinking about another submerged system think about flourinert. Mineral Oil has been known to disolve some PCBs over time. Also its gets very thick at cold tempertures.

[Cathar]

Grrr - delayed double post...

[Cathar]

Stirling Cycle engines? Using a Helium gas charge they can obtain fantastically low temperatures very efficiently.

[Alchemy]

Originally posted by hydrogen18
i didnt know LN2 evaporates even when sealed...is this because of its molecular size allowing it to vent thru its container?

No. LN2, like most things, does not diffuse through stainless steel at an appreciable rate.

It's vented because the pressure required to keep nitrogen liquid at room temperature is so high I can't even find documentation for it - possibly into tens of thousands or millions of psi. Possibly more. Most gas cylinders are charged to about 3000 psi.

So you can't just put LN2 in a tank and let it sit there - no matter how well-insulated, it will warm to room temperature eventually. But you can vent it, keeping the tank around a few dozen psi (I don't know what they're rated, but I know it's not much above atmospheric pressure) so that a little bit of nitrogen will constantly evaporate. This reduces pressure as well as cools the remaining liquid (and as we've tossed around here, a little bit of evaporation will transfer a *lot* of heat) which keeps the LN2 at a very low temperature despite the heat being tranferred to it from the outside.

I assume there's significant insulation between the inner and outer steel walls to reduce this heat transfer, but I don't know for sure as I've never built one. If you could put the LN2 in a perfectly insulated container you could keep it at 77 K and never lose any. But you can't, which is why LN2 containers are vented.

I've used 400 liter cylinders in my lab, which I assume had price tags around $10,000 to $50,000 - I never cared to ask. Smaller LN2 cylinders can be found here:

http://www.simpleshop.net/catalog.mv?3540

Happy shopping.

Alchemy