Pumping Liquid Nitrogen

External Since: Dec 27, 2007 Posts: 1

>So where does the pressure come from?

The loquid N2 boiling off.

>Maybe with a seperate expansion chamber and keen connections, but offhand,
>it doesn't work: internal pressure is internal pressure.

You put one end of a pipe down into the liquid. The other end
goes up above the tank you want to get the N2 into. There
is a lid on the storage tank that is sealed against the outside
of the pipe.

The internal pressure will push the liquid up into the pipe.
(If there isn't enough pressure, the weight of the column
of N2 will ballance the pressure and nothing will flow.)

The inside of the pipe is a hole through the wall of the
storage tank.

--
These are my opinions, not necessarily my employer's. I hate spam.

External Since: Dec 20, 2007 Posts: 25

mrdarrett RemoveThis @gmail.com wrote:

>Guy Macon <http://www.guymacon.com/> wrote:
>
>> 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.
>
>How about pushing the liquid nitrogen instead of pumping it?
>
>Imagine an insulated chamber, half-filled with liquid nitrogen, having
>a lid with two holes. One hole is for the nitrogen output tube, which
>goes all the way from the lid down to within say 1/8 inch from the
>bottom of the chamber. The other hole is for the input tube, which is
>just a short tube. This is where you blow.
>
>Now you just need a way to blow measured amounts of gas into the short
>tube, pushing the liquid nitrogen up the output tube.
>
>Compressed air tank with a needle valve... aquarium pump... CO2 gun
>cylinders... ?

I believe that the back pressure would stop the LN2 generator from
putting any LN2 into the dewar flask. The above scheme cannot
result in liquid going out of the output tube at a higher pressure
than the liquid coming in to the input tube, and thuse is not
actually a pump.

--
Guy Macon
<http://www.guymacon.com/>