[BillA]

did we not conclude that (1) was small ?

the Delphi paper speaks for itself I presume;
as the tests are normally run (in our world), Twi and Tai are both independent variables and setpoints
- is the C/W load dependant ?
in terms of efficiency my understanding is 'sure', the greater Twi - Tai the lower the C/W
but the changes, again, are not so large in our small rads at low velocities

EDIT
a very knowledgeable (thermo PHd) friend looked over the Delphi paper and made a dismissive comment about number manipulation and 'not science'. FWIW