I take NO exception to the 'theory' of thermo or fluid mechanics
(even I am not so daft)
but 'reality' (in the form of un-accounted for influences) often skews the results
can you describe what is occuring here ? (pop quiz, lol)
note that max efficiency is unique for each rad
re the frictional heating
come on, more than offset by the internal pressure drop
WAY too small
and the readings are at the inlet and outlet, any such is included (as is the effect of the pressure drop - several threads on this)