As SLF, I may be missing something, but having a fair bit of experience with Diesel-powered vehicles, I am struck by the cold operations similarities.
It seems odd that the pumping-system, with huge overcapacity/redundancy, could be used more effectively, in conjunction with the oil-cooler.
Again, It seems strange, from my simplistic viewpoint, that oil is first air-cooled,THEN dumps surplus heat into the fuel.
Also mentioned, this overheats in cases of low fuel-flows, to the point where fuel is burnt purely to circulate and reduce temps.
It's self-evident that Airliners are designed to operate mainly in high,cold conditions....they only pass through "warmer" environments on their way to and from their main environment.
SO, why is the "waste" heat, from the oil ,not fully utilised to warm a full-flow RECIRCULATING fuel system? no doubt there are also other sources of "waste" heat,within the engine -system...but full-flow would , with appropriate by-passes / pressure spill-off etc. keep the lube oil cooled and warm the fuel.
Yes, I appreciate that warm fuel is considerably less dense and therefore contains less energy per unit-volume, but I don't see big elastic bands at the airport, launch -assisting on hot summer's day
just about all road-vehicles (petrol and diesel) are fuel-injected,nowadays (emissions control! ) Invariably the pumps have surplus capacity over peak demand and all surplus spills off to a return to the tank....so I'm not inventing anything, just suggesting that maybe aircraft designers should think laterally.
(maybe they have and i'm talking bollocks!
)