Thanks for the link ira-k !
Precisely what I was talking about with the spiraled heatpipes ... you'll get the "rapids" effect but you won't have the restricted flow.
So why does higher flow results in better performance?
The more quickly I rush around, the more likely I'm going to be tumbled about (think white-water rapids as opposed to a smooth slowly flowing river). This means that I'm going to get tossed against the cool metal walls of the radiator more often, rather than just cruising along down the middle of the tube, only passing heat slowly to water molecules beside me that are only a little cooler than I, because they are beside another molecule, and then beside another molecule, before we get to the cold metal wall.