While it is certainly true that any device that heats slowly would be impractical on that basis alone, I do not think rapid heating provides any relief from the laws of thermodynamic efficiency. Combustion heats very rapidly, though if this device is even faster, perhaps that would be significant in hypersonic applications? I believe one of the problems of supersonic-combustion ramjets is maintaining a stable flame.
I keep coming back to hypersonic ramjets, not because I think they are the perfect application, but because I am not sure there is any application in an otherwise conventional jet engine - i.e. one involving a rotary fan or compressor - where you would not be better off using all the available electric power in an electric motor to spin a somewhat larger fan, and not bother with heating at all.
Update: Maybe, for replacing the turbojet engines of supersonic airplanes, you need heat to reaccelerate the flow above supersonic speeds, in a convergent-divergent nozzle? But supersonic wind tunnels seem to achieve those speeds without heating the flow? I have wandered well into my area of ignorance here...
I keep coming back to hypersonic ramjets, not because I think they are the perfect application, but because I am not sure there is any application in an otherwise conventional jet engine - i.e. one involving a rotary fan or compressor - where you would not be better off using all the available electric power in an electric motor to spin a somewhat larger fan, and not bother with heating at all.
Update: Maybe, for replacing the turbojet engines of supersonic airplanes, you need heat to reaccelerate the flow above supersonic speeds, in a convergent-divergent nozzle? But supersonic wind tunnels seem to achieve those speeds without heating the flow? I have wandered well into my area of ignorance here...