I find the concept interesting, especially if it can be made as efficient at stated in Airspitirt's article (
http://www.procooling.com/articles/h...ng_-_the_f.php).
I tought about building one myself, but I have no idea how to construct a piston tight enough to keep the cooling gas in place. Guess we're talking semi-high pressure Helium or Nitrogen here, right ?
Is anybody playing arround with this ?