BTW; I thought I’d just point out that I am not in disagreement with Monty’s math at all; it is right on.  I was simple taking issue with using the term “optimum” in the way he did.  Certainly calculating the mass flow rate required for heat rejection is step one. I guess aiming for the air exit temp equal to coolant exit gives you a ‘minimum’ point for air flow; but what is wanted as ‘optimum’ is minimum radiator size and weight, and minimum aerodynamic drag.  That’s a whole nuther level and beyond the scope of this discussion. 

Given the flow rate of the pump, the configuration of the airplane (tractor – pusher) radiator placement, space requirement, etc.; there is an ‘optimum’ coolant delta T, air delta T, radiator thickness, etc. from the standpoint of weight and drag.

There are certainly some wrong ways to do it, but no one right way.  

I’d agree this is accurate.

Al G