There should be a noticeable temperature difference between the upstream and downstream air(downstream being cooler) with the possibility of water condensation at lower air temperature. The air performed work by rotating the blades, hence lower enthalpy of exit air. It is the reverse principle of isentropic compression that takes place across propeller blades hence the decline in air temperature.
>>No chance of sabotage, either!<<
Send the structure to the bottom when power demand is at its highest. All one has to do is tilt the structure and all blades will be unbalanced. Can anyone say: “lights out”?
Thanks. BTW, “enthalpy” was new vocab for me. Now I’ll use it on someone else.