[mywittyname]

Those air cooled units with the heat pipes are effectively heat pumps, and heat pumps are crazy efficient at cooling. They rely on evaporative cooling, which soaks up substantially more energy, so much so that it's possible to to get temperatures noticeably below ambient using the method.

Converting water to steam takes about (from the top of my head) 5x more energy than it takes to increase it by one degree. I imagine the coolant used in these heat sinks is at least this efficient, if not more, and is something that evaporates well below 100°C.

If heat sinks were like using cars and roads to transport people. A water cooled setup would be like expanding the size of the roads to increase the number of cars that can transport people. While those heat pipe coolers are like replacing cars with trains, so you can do a lot more the same amount of space.

[nkurz]

> Converting water to steam takes about (from the top of my head) 5x more energy than it takes to increase it by one degree.

I think this greatly underestimates the potential of evaporative cooling. The "specific heat of water" is 1 calorie/gram °C --- that is, one calorie can heat one gram of water by one degree Celsius if no phase change is involved. The "heat of vaporization of water" is more than 500 calorie/gram at 100°C. That is, the energy necessary to convert a given quantity of liquid water from just below boiling to steam is not 5x the energy necessary to raise that amount of water 1°C, but 500x! You are probably remembering that this is 5x the energy necessary to take liquid water all the way from 0°C (almost frozen) to 100°C (almost boiling).