Pumping Liquid Nitrogen

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.

I want to pump the liquid nitrogen into a hole drilled
into the heatsinks of the CPU and GPU of a gaming PC
so I can overclock them farther than otherwise possible.
(This is for a a "just for fun" personal project, not
for work).

My question is how best to pump the liquid nitrogen.
In the past I have worked with big dewars and let them
self-pressurize with a relief valve on top and a feed
tube going to the bottom -- sort of like an aerosol
can. This doesn't look feasible in this case; the back
pressure seems like it will back up the gravity feed.
I think I need a small pump that can take the cold and
not add too much heat to the liquid nitrogen. Any ideas?

BTW, I have seven old 500 MHz. Pentium 3 systems that
are ready to be scrapped that I will be doing my
initial experiments on before deciding whether to
risk a more modern PC.

 

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?

 

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.

 

'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

"Guy Macon" <http://www.guymacon.com/> wrote in message
|
|
|
|
| I want to pump the liquid nitrogen into a hole drilled
| into the heatsinks of the CPU and GPU of a gaming PC
| so I can overclock them farther than otherwise possible.
| (This is for a a "just for fun" personal project, not
| for work).
|
| My question is how best to pump the liquid nitrogen.
| In the past I have worked with big dewars and let them
| self-pressurize with a relief valve on top and a feed
| tube going to the bottom -- sort of like an aerosol
| can. This doesn't look feasible in this case; the back
| pressure seems like it will back up the gravity feed.
| I think I need a small pump that can take the cold and
| not add too much heat to the liquid nitrogen. Any ideas?
|
| BTW, I have seven old 500 MHz. Pentium 3 systems that
| are ready to be scrapped that I will be doing my
| initial experiments on before deciding whether to
| risk a more modern PC.
|
| --
| Guy Macon
| <http://www.guymacon.com/>
|

 

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

http://www.xtremesystems.org/forums/forumdisplay.php?f=156

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:
[ http://www.physchem.co.za/Heat/Graphics/Heat42.gif ].
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.

 

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)

 

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 annoying thing on Usenet?

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.

 

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.

 

A slow cool down is needed to avoid thermal shock.

 

Somewhere on teh intarweb "Guy Macon" typed:

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.

 

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.