The water evap rate is limited by the solubility of the water in the oil: its near 0.
The mineral oil has a very very low evaporation rate at room temperature, I doubt its measurable outside a lab.
Vinegar will not prevent algae, and it will smell nasty. I recommend a few changes to your setup:
1)remove the metal supports from the outer chamber, as you have seen, they corrode in water. You can support teh inner tank on a plastic support or use a bed of aquarium gravel to distribute the Load.
2)Fill the outer tank with a mix of bleach and water, and pour a mineral oil cap over it (use about 1 inch of mineral oil)
That will prevent algae and the oil will prevent evaporation. Just don't spill it.
Better still would be to get a aquarium pump and a radiator and do away with the outer tank entirely.
I looked at putting one of these together a few years ago, for a slightly different purpose: with proper cooling, you could bring such a system down to temps below 0C, with no worries about condensation. With memory, processor, mobo, video card all operating at 0C there is a significant overclocking potential.
I was stopped by the problem of wicking, I never found a good solution and the mess was abysmal. Seeing the successes here I'm tempted to give it another go...thanks for the inspiration!
I was impatient and reassembled my system yesterday, before I could receive any suggestions from knowledgeable SPCR readers. :-(
I replaced the metal spacers with plastic ones -- so, that should take care of the corrosion. It was stupid of me to try using metal in the first place -- I should have known better than that!
I googled around on the web, and found reports that vinegar might eliminate the algae. I'm sorry to hear you report otherwise. I refilled the water tank (5 gallons) and added 1 cup vinegar, and then poured on the mineral oil cap (about a pint, gives me a 15mm layer of oil). I think maybe the oil is containing the vinegar smell, because I smell nothing. Also, I thought maybe the oil would prevent the algae from receiving the air it needs.
If I see algae form, I'll redo the water tank with bleach instead. Thanks for the suggestion!
About the oil cap -- yes, the insolubility of water in oil is exactly what I was counting on. I didn't know how completely insoluble water and oil are, though. My experiment is revealing that it pretty much completely stops evaporation, for all practical purposes.
About using a radiator -- I considered that, but I favor silence over cooling, and my (limited) experience is that water pumps are still audible. Also, I don't know how well the pumps would move the oil (it is less dense, yet more viscous). And finally, I prefer the simplicity of the static water tank -- no tubes, no electricity, no moving parts to fail. If I do a build from scratch, though, I might play with something more complex.
Interesting idea about using cold oil to supercool without condensation. I like it! You'll have to use a different type of oil, though, because mineral oil thickens at lower temps. Just for kicks, I threw a pint bottle of mineral oil in the freezer, and it looked and felt just like vaseline until it warmed up again. I wonder if it can be mixed with something (affordable and non-toxic) to make it thinner at low temps?
About wicking: I have seen others report issues, and for some reason I'm not having a problem with it. I find a very light film of oil on the power supply cables leading to the mobo, but no pooling as reported by others. I do sometimes wonder if oil is accumulating inside the PSU -- I fear I may someday inspect it and dump a bunch of oil onto my shoes. :-)
The keyboard, mouse, audio, and usb cables appear to be oil-free, possibly because (1) the connectors along the top edge of the mobo are actually sitting ABOVE (not immersed in) the oil, and (2) the cables leading from those connectors lead upward about 8 inches which forces the oil to defy gravity a rather long distance. These two factors may possibly slow down the wicking so much that I cannot perceive any happening. Se my post of (Wed Mar 26, 2008 6:28 pm) to get a picture of that.
Did you use mineral oil in your previous attempts, or some other type of oil?