Test Setup: A load of reactors on one side, columns of 10/18 exchanger/turbine rows on the other. The number of heat pipe paths bridging the two sides can be easily varied. I took extreme care to make sure all heat pipes were placed from teh reactor to the destination, since it's already known they tend to behave directionally.
![Image](http://i.imgur.com/BjJvY4H.jpg?1)
![Image](http://i.imgur.com/7Yg5tJ2.jpg?1)
Sure enough, the pipes seem to choke at roughly 1GW/pipe. There doesn't seem to be any pattern as to which paths after the chokepoint get the energy, but the final electricty output is quite definitely capped at ~1GW/pipe width. Replacing the missing pipe widths lets the system resume full power with little difficulty.
![Image](http://i.imgur.com/OtPFSk2.jpg?1)
If there's a distance limitation to heat pipes, I haven't found it. Even at 1000 units of heat pipe, you can still keep a 10/18 configuration at full output. You will, however, wait a LONG time for the heat to actually reach the destination
![Smile :)](./images/smilies/icon_e_smile.gif)
![Image](http://i.imgur.com/2lcmlr0.jpg?1)