Thermally Pumped Electric Ducted Fan Aircraft

Somewhat remarkably, significant increases in wing lift to drag ratio can be achieved by changing the temperature of the surfaces. E.g. a NACA2412 aerofoil can be 36%* more efficient by cooling the upper surface to 200k, or 89% more efficient by cooling the upper surface to 250K and heating the lower to 350K. <link>. It seems that cooling is the bigger driver, particularly in low Reynolds number (small) wings such as those found on drones/model aircraft/cruise missiles.

So what if we used Peltier devices to cool the upper surface, what do we do with the heat we have moved? Well, we can move heat around quite effectively with heat pipes <link> even without moving parts. But what do we do with it?

Many model aircraft are propelled by electric ducted fans (EDFs) which are usually powered by brushless DC motors and sit inside a tube structure in order to behave somewhat like a mini jet engine.

Conventional jet engines** are powered by heat. The turbines are only there to power the compressors, the compressors are only there to provide idealized combustion conditions for the fuel. You can just have a series of fires in a tube and get workable, if inefficient thrust <link>. What if we use the heat pumped from the wing to increase thrust? This can be done by carefully designing the shape of the duct to take advantage of the Meredith effect <link> to inject heat after the EDF. So we get more efficient wings and bonus thrust. The trick is whether it's worth the extra electrical load. If not, a conventional jet engine might be configured to achieve the same effect. Bleed air drawn from a compressor stage could be cooled in a Meredith effect bypass duct, then the pressure released to cool the wing surfaces. Same idea, just moving heat in a different way.

*equivalent to a few decades of airliner wing development <link> **and the lunatic nuclear engines <link>