Hi,

I just read your article on the silent oil-filled PC (coolest idea ever, BTW!) and was just wondering if you ever planned on testing out the overclocking capabilities of such a cooling solution? I'd be interested in seeing how much harder you could push a CPU/GPU over an air-cooled or other cooling solutions? Maybe some kind of overclocking showdown with various coolers to see what performs best, or which is the best bang-for-the-buck?

I was also wondering why you recommend motor oil? And why didn't you use it in your test? Given the price of the electronics involved, motor oil wouldn't be a huge cost increase...

Thanks for a superbly interesting article! :)

Dan

Reader Response From Mr. Rau, Germany: Using De-ionized Water As A Coolant

Dear THG-Team!

I just finished reading your article on cooling a PC by submerging the components in oil and would like to comment. You wrote that you used water in your original trials. Did you use distilled water or de-ionized water? I ask because there is a huge difference between the two. Compared to de-ionized water, distilled water looks like slurry.

In a very complex process, the conductance of de-ionized water is reduced to a bare minimum (µS = micro-Siemens) using deionization filters. (The filter material looks a lot like those little hydroponic fertilizer pellets.) It is so sensitive that it has to be transported and stored in containers that can effectively protect it from any light.

This type of water is used to cool krypton lamps in lasers, since it is of the utmost importance that none of the substances found in the coolant accumulate on the lamps (4kW per lamp, up to four lamps per laser). These high-powered lamps require an initial ignition voltage of up to 30,000 Volts and then continue to "burn" at 200 Volts. Since the electrodes of the krypton lamps are submerged in water during this process, the only choice here is the aforementioned de-ionized variety. However, this type of water is highly aggressive and requires constant monitoring and filtering to clear out even the most minuscule particles (down to 2µm) and thereby ensure the required purity. Also, the aggressive nature of de-ionized water puts certain strict limitations on the materials that can be used in such a system. For example, any steel components such as screws, connections or casings need to be made of stainless steel. Glass and almost any type of plastic can be used as well. All other metallic materials (steel, copper, brass, aluminum, nickel, etc.) will suffer extreme corrosion almost immediately as the water mercilessly tries to replenish its missing substances (i.e. ions) from them, if present. That would mean that de-ionized water would make short work of any circuit paths, soldering terminals and even the pins on the processor or its socket as well as any conductive materials if used as a coolant in a PC. Therefore, the entire cooling circuit would need to be completely free of such materials.

I'm still trying to figure out what could have caused the short-circuit you described. Even if the conductance of the water had not been low enough or the aggressive water had drawn ions from the PCB's exposed (brass-covered copper) areas very quickly, the voltages used in a normal PC are not sufficient to cause a short-circuit, in my opinion.

Finally, long-term usage would also require the cooling system to be made impervious to light to prevent algae formation. Since the coolant in such a system would require a very high degree of de-ionization to ensure low conductance, adding anti-algal agents would not be possible.

Incidentally, water is a much better coolant than any type of oil, since it can dissipate more heat per unit of volume than oil. On the other hand, oil-cooled components will never rust, although the thermal load they can bear is also lower if the radiating surface is the same. In either case, a good circulation of the coolant should be ensured. I hope that I have been able to make at least a small contribution.

Eberhard Rau, Erdmannshausen, Germany