A heatpipe is a device that efficiently moves heat from one end to the other using vapor from boiling liquid as the "carrier" of the heat. The liquid boils at low temperatures because it resides in a vacuum. Room temperature boiling is possible inside a vacuum using a suitable fluid...not necessarily water. Heat is applied to one end of the pipe and the vapor from boiling fluid carries the heat towards the cooler end of the pipe where it is dissipated by air, water, or some other method of removing heat. Capillary action carries the condensed vapor (liquid) back to the "hot" end where it is boiled and vaporized again and again. Sounds like a lot of trouble, doesn't it?
What if I said it was a thousand times more efficient than a similar sized length of plain old copper? Yep, it is a thousand times better at moving heat than copper. The heatpipes I'm using are made for Compaq for use in their 8000-series 8-way Xeon servers. They are a direct bolt-on replacement for the standard heatsinks. I found this pair of heatpipes on ebay for $120. I made a simple duct that allows one fan to blow through both sets of heatpipe cooling fins. Basically, it's a piece of angle stock clamped between two more pieces of angle stock with a small fan blowing from underneath. It works very well and looks interesting. Hey, that's exactly my goal when I build computer cases.