[redleader]

-how do you produce a flow rate in the system? you mention no compression, but you're in a vacuum, so how do you get your 'refrigerant' to cycle

This is called convection. Its natural and in theory it will pump heat faster then any Eheim ever could. In practice its more complicated.

water has great heat transfer capabilities so this type of system could probably produce a great btu/hr but in the end your operating temp is still 120-130f isn't it? Your cycle won't even start until your cpu or whatever heat sources you have bring your refrigerant up to that temp which is around 50c - a temp that i would feel is uncomfortably warm for my system. My phase change system is in pieces right now but with just my watercooling setup with a fan blowing over the res (in place of evaporator submerged in res) i'm at 87f (31c) under full load

This is what your intuition says, however thats not how it works. Think when you get out of the shower, you don't have to be in a hot room for the water to evaporate and make you cold. In fact any time you are above the freezing point this effect will occur.

The operating range is actually quite broad, wider then with watercooling.

-implications of pure water in the system - corrosion, lubrication of moving parts / pump / compressor, etc

What moving parts? How would their be corrosion?

Heres a link to some on going heatpipe experiments:

http://arstechnica.infopop.net/OpenT...5&m=7250984465

once i saw an old ammonia based air conditioner from the 40's - it had a gas fired burner in it and pumped chilled ethylene glycol into the house, i don't have clue how it worked but whatever principle it used might be useful here! anyone here know anything about that type of system?

I finished my thermo final 4 hours ago, so what the heck. A heatpump can use any source of work to pump heat. It can be electrical, chemical, kinetic, potiential, even thermal (though you would need very special cirrcumstances before this will work).

My guess is that system was burning fuel to generate kinetic energy that was driving a compressor. But it could have been more exotic.