The Collaborative International Dictionary
Vortex tube \Vortex tube\ (Physics) An imaginary tube within a rotating fluid, formed by drawing the vortex lines through all points of a closed curve.
Wikipedia
The vortex tube, also known as the Ranque-Hilsch vortex tube, is a mechanical device that separates a compressed gas into hot and cold streams. The air emerging from the "hot" end can reach temperatures of 200 °C, and the air emerging from the "cold end" can reach -50 °C. It has no moving parts.
Pressurised gas is injected tangentially into a swirl chamber and accelerated to a high rate of rotation. Due to the conical nozzle at the end of the tube, only the outer shell of the compressed gas is allowed to escape at that end. The remainder of the gas is forced to return in an inner vortex of reduced diameter within the outer vortex.