I had envisioned the fuel heater in the wing.
There are hydraulic oil-to-fuel heat exchangers.
- 1 heat exchanger in the left main tank for the left hydraulic system,
- 2 heat exchangers in the right main tank for the center and right hydraulic systems.
Through the heat exchangers fuel cools the hydraulic oil but due to the large volume of fuel, heating of the fuel is negligeble.
Regards,
Green-dot