Making a custom passive heatsink using heat pipes, how do they work?

[Sevarsuab]

I've been looking into making a custom heatsink for a case I designed myself, but when I started looking into heat pipes there wasn't an awful lot of information regarding specific details, such as which end of the heat pipe is the "head" and "foot" end, and which to apply to the heat source. Also, what are the differences between grooved, wick material and sintered heat pipes?

[LogicalDrm]

I have no idea where you have picked up those "different" types of heatpipes. But the way they are supposed to work is that they are filled with liquid which into gas and back when heated. When liquid is heated, it turns into gas and gets replaced by remaining liquid. Gas bubbles then move to cooler end of pipe where they cool and turn back to liquid. Actually it might not even turn entirely to gas, but expands. In any case it moves around in pipe and transfers heat while at it.