Well....i guess if you wanted to, you could use a copper suction line for a phase change system. But they would add up fast.
I agree, you need to do alot more re-search.
Heatpipes come in 3 different types aswell.
1. The cheapest to produce is the regular copper pipe.
2. The next "tier" of heatpipe would be with a copper braid lining the inside of the pipe to increase surface area.
3. The best heatpipes are built using kind of a powder. Very hard to explain with words, this picture will do a much better job.
To make a heatpipe yourself you would need a vauum pump and some schrader valves. Wich would add up to about $200.
Not to mention if your using a copper flex line, each line will be $20+