[pHaestus]

Sorry Ben. Didn't mean to offend the experts.

Wouldn't any rise in temperature from restriction and friction and pumping action be independent of pump? For these types of temp rises then pushing x gpm through a loop with any pump should yield the same temp rise. As a practical matter, can you actually measure these rises? What magnitude? Quite small I'd guess across any given component. What resolution is needed? 0.001C would be my guess for MINIMUM resolution to detect such.

If they are just a function of flow rate though then pumps can still be compared to one another by the delta T across the pump itself (the only variable in the system would be how much of a pump's heat is dumped into water).

I seem to recall someone measuring the volume of water in loop, taking a stab at thermal conductivity of all the parts in loop, and then making an educated guess by looking at dT/dt. Sorta fuzzy on details though; was long ago...