You should fill the tubes 1/4 full with methanol or ethanol, so as it boils and evaporates it flows to the top, giving better heat transfer and temps.
im way ahead of you. i was going to fill the tubes with eather because its boiling point is like 35c wich is perfect for a cpu.
My last plan looked like this
But i am going to change it a little
So now it will have like 20 heatpipes and they will each have there own individual tube rather than all of the tubes looped together like in my original design
It will look sunthin like this except with a shitload more heatpipes, i just got lazy and didnt feel like drawing them
But in the new design each heatpipe will be indivual of the others.
and it will have liquid in it of course