The Crosley IcyBall (wikipedia) is a commercial early-twentieth century portable chemical refrigerator that runs without moving parts or electricity. Cooling is caused by the evaporation and re-adsorption of ammonia into a water-based solution, which is a spontaneous process that can be reversed by applying heat, as from a campfire. Authentic IcyBalls are valuable antiques, but Larry Hall has posted a cool write-up of the one he built for himself using gas pipe fittings.