Cooling a server with oil bath
Points speaking against oil cooling in a professional setting:
You may have to review the fire safety regulations. Having a few dozen liters of oil in your server room will add significantly to the fire load. All server hardware is certified for fire protection, in the sense it will not put other stuff on fire. An 800 Watt power supply will make a nice fryer if something goes bad.
Almost all cooking oils get smelly with age. Then you have to recycle the oil. That´s work, which means cost. Nevermind cleaning up after you each time you touch the damn thing. Let alone plugging in a new mouse.
Speed of repair if something goes wrong. Granted, almost always the moving parts break. But then you are adding a whole lot of new variables into the equation. Degradation of oil -> oxidation -> contacts. Effect on parts? Will the plastics change? The Elkos? The layers of the PCBs?
Good oils creep. Into the cables. And along them. Capillarity is your enemy! And god forbid one of the cables makes a bend and hangs down... drip drip.
How do you go about the parts that break most of the time, disks? They´re outside. So you need a rack for them. And cooling. And power. Soooo... if you are going to have a rack and cooling anyway, why go through the hassle with the tank?
No Aquarium. I would see the point if you could do it with water and have a goldfish or two in there. A server with fish would be seriously cool.
It certainly is fun to make at home. But to make a solid system at work? I´m not so sure.
It works, and at least one company sells PCs pre-built to run fully submerged in oil for cooling. However, in all cases it is more complicated and adds additional risks compared to air cooling. To start with, you have to factor in the significant additional weight, not only in whatever structure is going to hold or support the equipment but also when moving things around. The oil has to be circulated and filtered and replenished, requiring more equipment, which must itself be maintained. There is the possibility of residue formation. If you're using vegetable oils, there might be bacterial growth. It's a lot of work to consider.
The board is usually coated in sealant anyway, except at the pins. Oil really does have a low conductivity, and metal ions don't readily end up in solution in it (which is what makes water conductive - pure water is unconductive but doesn't stay pure for long easily).
It does work, but don't submerge hard drives as they usually have an air breathing hole.