I am glad you asked that.
As you should know by now, passive 2-phase immersion cooling is one of the most elegant ways to cool. Now compare that process using 3M Novec Engineered Fluids with their low boiling points (ie. 34C or 49C) with a simple mineral oil bath, which is thick and greasy (oil is a high viscosity fluid) and doesn’t boil. It performs better than air, but due to its physical limitations it will never get close to evaporative cooling (aka “phase change cooling”, “2-phase cooling” or “multi phase cooling”) we use in our systems with Novec fluids.
One of the great advantages of passive 2-phase immersion cooling is to reduce mechanical infrastructure, while oil actually adds new points of failures to the equation (see our more formal FAQ here). Our tanks are literally silent, dust free, and don’t have any moving parts. We don’t have pump stations next to our tanks, and no oil means we don’t need secondary containment tanks around or under the tanks due to safety regulations. Did I mention that Novec is non-flammable and used as green fire extinguisher at really important data centers (stock exchange)? Or operating theaters, where you don’t want a sprinkler system to go off during surgery?
If you have immersed a motherboard with CPU into an oil bath, you probably realized that without pumping and moving the oil, it doesn’t take very long for the CPU to overheat. While oil is somewhat better at transferring heat than air, it is unfortunately also incredibly good at storing it (that’s why you find oil in oil radiators).
And don’t even think about removing your heat sinks from your CPUs. In fact, you probably have to clean them up first to remove the thermal grease and reseat them using indium foil, or you’ll soon need oil filtering and other maintenance procedure on your oil and pumps. Oil pumps are noisy and consume electricity too. You might also need a box of tissues and rubber boots nearby. It’s also not unheard of that people running mineral oil cooled hardware need to wash their gear with dish wash liquid or in a dishwasher (I am not making this up).
In summary, with oil there is no phase change, it’s a single phase process with oil merely replacing the air as a means to transport heat away. Try pouring mineral oil (or baby oil for that matter) over your forearm and see if you feel any cooler. Now do the same with Novec and you will feel the magic of 2-phase cooling. No cleaning up required, too.
Oil simply doesn’t have the high heat transfer coefficient or “magic” of a 2-phase evaporative cooling process and it doesn’t have some of its other properties such as being non-flammable (on the contrary!) or keeping your gear nice and clean. Oil is a burden for the environment and dangerous, and classified as such, it’s not a green solution (just ask your fire department or your insurance company).
What we do, really, has nothing in common with oil cooling, other than being liquid. We are not even using evaporative water towers on the outside, so we don’t waste a single drop of water. Our systems are so efficient we simply don’t have to.
For mining, it’s probably better to stick with heatsinks and fans instead of using mineral oil, or some nice water blocks from Asetek. For low density applications (a couple of servers) oil probably does an OK job, but I personally wouldn’t want the pain in the neck that comes with it (mess, reseating heat sinks, regulations, noise and all that). Not as long as there are much better ways of getting the heat out with the same energy savings. Check some of the videos on YouTube about mineral oil cooling.
For high density applications and cutting out all the parts and headache, there’s only one way forward.
Hope that helps 😉