If you should return bypass fuel to the wings anyway to dump the heat load
caused by the pumps and the trip through the engine bay, has anyone (except
Boeing) tried a fuel/oil heat exchanger? The bypass fuel should still have
have an adequate temp delta for effective oil cooling, and the tanks (at
least on an aluminum aircraft, should reject enough heat (Pure speculation
on my part).

All Boeings use fuel oil heat exchangers, as much to get the fuel above
freezing, preventing ice crystals damaging the HMU as for oil cooling.

The failure mode on turbines is for higher pressure fuel to leak into the
oil, leading to nil apparent oil consumption. On a 13B the balance of
pressures would lead to oil leaking into the fuel, hopefully giving blue
smoke and increased consumption as failure warnings.

Mark Wrathall

Tracy said he almost did that, but decided to leave the "hot fuel in an engine compartment" experimemtation to someone else.  But really, with the pump already pumping fuel back to the tank, It would be an easy task to run the fuel through one of powersports water/oil heat exchangers on its way back to the tank.

Still, that could probably heat up the tank really quick, and there isn't a whole lot of surface area to cool it down with...

Dave Leonard

 
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