I see this has diverted into bleed air
I'm not sure where the trent gets it's air from to go into the spinner, but Pratt gets it from the last bearing compartment in the turbine. That air is just warm enough that it screws forward inside the fan drive shaft (some obscure guy discovered a heat pump screw effect under these conditions.)
All one had to do was to twiddle with the drain holes (for water condensation and oil leaks) in the spinner to let the air flow just enough to keep the ice sheath covering down to a minimum.
The heat flux is minimum until the ice actually forms and creates a surface insulating blanket to raise the skin temperature of the spinner high enough to shed the ice. Certainly not a big performance hit on the engine air.