[pHaestus]

The variation in power from last night/this am's data? At very low flow rates it's difficult to perfectly insulate the hoses and I suspect that the 0.5GPM flow number is somewhat suspect for that reason. For the numbers above 2GPM the delta T is so small that better resolution than 0.01C is required (a difference of 0.01C corresponds to nearly 10W). The numbers from 0.75-2GPM are pretty much dead even at 72-74W; not much variation of CPU power with flow in that case.

If you mean the earlier test results then there was a 0.06-0.07C offset in my temperature probes that I didn't catch (but incoherent did).

As for Bill's graph, consider that we are dealing with water inside a heat pipe, and that water has some interesting properties which occur near phase transitions. Solid water floats, for instance.