Originally Posted by Powergeek*_*
1. I have access to my school science departments LN2 tank, which one of the teachers can get filled for free or for very very cheap ($10). I'm not sure exactly how big it is but I would guess 3 gallons.
2. I AM NOT COOLING A RAD, I WANT TO COOL THE OIL, WITH THE RAD FILLED WITH LN2
3. I was thinking about the possibility of having a on/off valve on one end and a gas relief valve on the other end. Since the nitrogen gas is still very cold and is not completely useless until the temp gets hotter (maybe around -50c), that being the time where I would open the valve and refill the rad.
4. In order to use #4 (which I thin has great potential), I need to incorporate this into putting the computer in mineral oil (since I am supposed to be doing this a chemistry project).
(1) Nothing is free--N2 is fairly cheap though
. But 3 gallons of liquid nitrogen at a time likely wouldn't last long at all, especially when trying to get things set up properly initially--how easy is it to get it refilled?
(2) Cooling the oil with the rad filled with the N2 would likely just freeze the oil around the rad unless you have a fan system set up in the oil--frozen chunks of immobile oil around the rad won't do much to cool the rest of the oil, so you'll definitely want forced convection in the oil with fans, and you'll want to ensure good oil flow around the heatsinks for the hot components of the system. But you could probably get similar and cheaper results if you just pipe ice-cooled water through the rad to cool the oil instead of N2. Also, putting a rad in the oil to cool the oil isn't as preferable as actively pumping the oil through a chilling device (like a rad) and then back into the oil bath. You could set up a heat-exchanger where you submerge a rad in something like ice-cooled water and pump the oil through the rad--it would be much more efficient at cooling the oil than submerging a cooling element in the oil. (and of course, you could use something other than ice-cooled water to cool the oil--but nothing so cold that could freeze the oil, which LN2 could do).
(3) Putting an on/off valve on the rad and filling it with liquid nitrogen then closing the valve would result in the rad exploding, or at best blowing the valve apart since the liquid will be vaporizing in the rad as it warms up.
(4) What results are you hoping for for your project? Because the mineral oil doesn't have to be cold to properly cool a computer--just have enough heat removed from the oil so the components don't get too hot. Probably just using an air-radiator and pumping the oil through the rad should work okay. But I think it's more difficult to cool oil as efficiently as it is to cool something else, like water (i.e. it requires the oil to be piped through a longer rad to remove as much heat as a similar amount of water). But don't quote me on that last part.
Sounds like a fun project.