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August 31, 2013, 01:13:00 PM |
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OK...
Oil cooling does work. But unless you have a massive tank with a huge external face surface area, you will soon heat all of the oil until it is too hot to run the card at temperatures that will prolong its longevity. The problem I am referring to is not the temperature of the GPU cores or the VRM transistors themselves that you can see with GPU-Z, but other components that are usually kept passively cool like the smaller transistors and electrolytic capacitors that have maximum temps ~75-90 deg C.
If you are pumping hundreds of watts of heat into the oil, sooner or later you will need to remove that heat actively. You could get a robust pump and flow some of the oil through a heat exchanger, essentially water cooling but with oil instead of water. You could alternatively immerse some heatsinks into the top of the oil (which convenient is where the hottest oil will rise to, because of density changes in the bulk fluid).
You can't run the whole card as-is in the oil. The fan will burn out eventually because it has to work so much harder in the denser fluid. You will need to disconnect the fan and probably remove the plastic assembly, then relying on thermal gradients and density to move the oil past the hot heatsink(s) and components. Failing that, you could install some kind of low RPM stirrer to move the oil. A long time ago on one of the overclocking forums a member even had a rotating oil bath rotating 'around' a stationary motherboard+CPU+etc that was held in place from above, with great success. Sorry, I cant find the link, it was probably archived and lost.
There is a chance that the electrolytic capacitors (in the silver 'cans') will become damaged to the oil you choose. There is very little information available about this aside from the occasional anecdote. The problem is that these capacitors are not always perfectly sealed, after all they were never designed for oil immersion, and as a result the oil changes the properties of the electrolyte mixture in the capacitor and it can fail in various ways.
Another problem is that some oils will cause capacitive electrical problems in some immersed electrical components. This is exacerbated by the high frequencies that some of the components operate at on the cards, and with oil sitting across multiple contacts/pins/traces the capacitive effects can lead to instabilities.
As for cleaning oil off the components then here is my advice:
1. hang the card up by a piece of wire or leaning upright so most of the oil drips out / off
2. rinse off most of the oil with huge quantities of cheap dish washing liquid + hot water. this should remove the majority of the oil. And no, washing many kinds of computer components in water while they are off does not usually damage them so long as you are 100% sure it is completely dry before you power it up. Again the problem of unsealed electrolytic caps remains the only exception and problem here...
3. get yourself a few liters of your typical hardware-store-grade mineral turpentine (usually just $3/L...) and then immerse the card in a bath of it. It will dissolve the remaining traces of oil. It will also help remove any water, because they are completely immiscible liquids and you will see they will separate nicely from one another in the bath. If the oil you chose to use was not effectively removed with the mineral turpentine, try methylated spirits / denatured alcohol which is also very cheap.
4. Remove the card, hang it up near a powerful fan to dry for a long time.
5. your card is now back to normal, ready for new thermal interface material and heatsink / fan assembly re-installation.
I highly recommend low viscosity oils.
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