Pumping Liquid Nitrogen

Let me be the first to say, "that's going to be cool." :-) Mike

It would be easier to deal with the boiloff gas - it's still at 77K. Do you actually need the LN2?

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Dirk

http://www.transcendence.me.uk/ - Transcendence UK
Remote Viewing classes in London

The only thing that comes to mind is pumps used for liquid fuel rockets.

D from BC

CPU cooling with liquid nitrogen

D from BC

What's the temperature spec on the CPU you will be using? Odds are that it won't deal with LN2 temperatures well.

Consider the heat capacity of LN2 (include the heat of vaporization) compared to that of H2O. For the complexity of what you propose to do, LN2 won't buy you much more than a good heat exchanger/radiator setup.

Also, keep in mind that in an enclosed space (your mom's basement? ;-)) the nitrogen gas will displace air and asphyxiate the user if not properly ventilated.

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Paul Hovnanian     mailto:Paul@Hovnanian.com
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ASCII stupid question, get a stupid ANSI!

'Guy Macon' wrote, in part: | I have been offered a small (about the size of a water | cooler) liquid nitrogen generator at an attractive | price. It generates four and a half liters per day, | using a gravity feed to keep a half liter dewar filled. _____

You could just Google a search string that includes [ overclocking CPU liquid Nitrogen ] and get over 94,000 hits. Most (if not all) these Rube Goldberg devices just build a tank around the CPU heatsink, fill the tank with liquid Nitrogen and let it boil off as it may. For actually pumping liquid nitrogen you could contact NASA for a few tips... especially safety tips.

Taking a flyer with a Pentium III is hardly worth the effort.

One possibility for a more or less continuously operating cooler would be to use the boil-off of liquid nitrogen to chill an anti-freeze mixture (propylene glycol & water ~ 50:50 should be good to below - 40) that you could then pump through a more or less stock CPU water block.

Phil Weldon

There is a whole forum devoted to LN2 and dry ice here. Maybe someone here will have an answer.

Paul

That's wonderful; how are you going to deal with frost? Where's this water gonna go when it melts?

You can use a simple piston pump for the actual pumping. The motor should be connected via a very long non conducting rod.

The construction of the pump can use Teflon parts where things need to slide and silicone parts where a little springiness is needed.

The idea, however is quite insane. The thermal stress will break things in the computer.

You could be shooting yourself in the foot. I think the self pressuring with a dip tube in the flask is the way to go. Back pressure? Where is that coming from? Plan to regulate the boil off at the outlet of the Pentium heat sink?

The gas is much less dense than liquid to it should get through the heat sink without much back pressure .

The foot wound - check the low temp specs on the Pentium before you go all out on this. Transistor gain goes way down at cryogenic temperatures.

Yup. The latent heat of evaporation for Nitrogen is 198.3 Joules per gram at one atmosphere, while the the specific heat capacity for nitrogen is only 1.006 Joules per gram per degree Kelvin. Also, liquids conduct heat far better than gasses.

I don't have an uploadable cooling curve for nitrogen at hand, but take a look at the cooling curve for water: [

]. The portion of the curve labled D shows that the energy needed to go from 99.99 degrees C to 100.01 degrees C is much larger than from 0.01 degrees C to 99.99 degrees C. This is typical of boiling liquids.

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Guy Macon

Others have done it without any problems. Semiconductors as a rule do not mind LN2 temperatures as long as you avoid thermal shock and icing. Besides, overclockers pretty much expect to lose a few if they push the envelope.

It will buy me minus 196 degrees, and others who have tried it have reported a stable system with a 3GHz. CPU overclocked to 5GHz.

Nope. that's for systems with a *source* of nitrogen. A nitrogen generator takes as much out of the room air as the boiling nitrogen puts back in. (I would ventalate it anyway, but for the opposite reason; to avoid any Oxygen concentration around the generator)

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Guy Macon

A: Because it messes up the order in which people normally read text.

Q: Why is top-posting such a bad thing?

A: Top-posting.

Q: What is the most annoy>For actually pumping liquid nitrogen you could contact NASA

You are talking to the person who taught the cryogenic safety classes for Parker Hannifin on the space shuttle

17 inch disconnect project -- under contract with NASA.

You prefer I ruin a few Core Duos while I experiment?

I don't want minus 40. I want minus 196.

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Guy Macon

Frost comes from condensation. Condensation comes from moisture in the air (humidity). Boiling liquid Nitrogen produces a gas that has no moisture in it -- it is completely dry -- and will fill the enclosure if I make it so that all fans recirculate instead on exhausting.

I will have to worry about the outside of the case dripping, though. I wouldn't want it to drip on to the internal circuitry.

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Guy Macon

A slow cool down is needed to avoid thermal shock.

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Guy Macon

Ohhh! Original.

You come into our house asking advice and act like this? Good luck with that.

And you're asking your questions here because all those contacts you made are ob holiday?

Sure, with the money you made from a morning's teaching cryogenic safety classes you could ruin a few Core Quads. After all, you can afford a liquid nitrogen generator, what's a few hundred bucks worth of CPUs? Trying it with a PIII is like learning to drag-race in a pedal-car.

Well Mr. Cryo-teacher, be sure to let us know how it works out for you. Or not.

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TTFN,

Shaun.

Experience designing the 17 inch wide valve that connects the external tank to the space shuttle doesn't apply much to the problem of finding a small, cheap pump for less than a liter per hour of liquid nitrogen.

The word "taught" is past tense. I no longer work for Parker. The Jamboree Blvd. plant closed down quite some time ago.

If I was thinking of trying something that could burn out my expensive drag racer, I might very well try it on a few pedal cars first. Even if I could afford to destroy multiple race cars.

"Arguing with anonymous strangers on the Internet is a sucker's game because they almost always turn out to be -- or to be indistinguishable from -- self-righteous sixteen-year-olds possessing infinite amounts of free time." -Neil Stephenson, _Cryptonomicon_

*plonk*

Notwithstanding the "it's _TOO_ cold!" warnings, if you own your own house, you could use plain ol' gravity feed - just put the generator on the floor above the comp, with a very tall dewar between.

Of course, that depends on whether modifying the house is cheaper than a(an?) LN2 pump. ;-)

Good Luck! Rich

Yup, gravity feed was exactly my thinking as I read through this thread. Let me just add:

Keep the liquid nitrogen BELOW eyelevel. Think about not only spills, but drops spattering about. (Imagine grease or water in a hot frying pan. That's what liquid nitrogen does when it hits "hot" room temperature objects).

Mark

p.s. that being said, I will mention that I violated the "eye level rule" back in grad school. The main point is to be careful while still having fun.