Allison> The real problem with water is not it's conductivity. High Allison> power tube transmitters have used distilled water in the Allison> past as it's a really poor conductor if kept clean. Allison> DEC experimented with water cooling too. The Aquarius Allison> project was a water cooled VAX. Too many headaches with Allison> leakage, heat transfer to the environment and installation Allison> issues. Systems like that use a chiller and heat exchanger Allison> to cool the closed loop water system. Those are costly and Allison> difficult to install. Murder if it should leak in a Allison> computer room. Then there is an efficientcy problem as you Allison> end up using power to move heat which adds heat.. Allison> With all that, the circuits they were trying to cool were Allison> getting more power efficient. So by time they worked out Allison> wet cooling air cooling was again attractive or at least far Allison> easier. I remember that episode. The result was "Aridus" :-), now known as the 9000. Allison> It's still packaging. ;) Yes. And if your circuit density isn't all that high, air cooling works fine. That's why Cray actually had to solve these problems, and did back in the early 1960s (CDC 6600), because he DID build things that could not sanely be cooled any other way. I don't ever remember hearing of leak problems in our Cybers... paul

I think that is a minor issue. Even a relatively small pump will move the coolant around enough. The flow is generally not all that fast, nor is the temperature gradient. William Donzelli aw288 at osfn.org