Also known as the Ranque-Hilsch vortex tube or the Maxwell's demon tube, this is an amazing device that produces both cold and hot air when compressed air is blown through it.
It was conceived in the early decades of the 20th century by the French physicist Georges Ranque and during the second world war, it was improved upon by a German physicist named Rudolf Hilsch.
The device is simple enough to be constructed in a home workshop with a hobbyists metal lathe.
It consists of a T-shaped metal tube. When compressed air is blown through the trunk, cold air blows out from one of the arms and hot air from the other end. The efficiency is not as good as conventional refrigeration devices but the simplicity and size of the device give it great advantages.
Commercial devices achieve temperatures of -40 degrees centigrade and below.
There are many hypotheses about how it works, but no one knows exactly.