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. Pressurized 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. Main factors lead to cooling is the size of diameter tube with material used, length of tube and most important one is the compressed air pressure. Review says that as the compressed pressure increases you get the greater difference in cooling with material used as PVC as compared to copper.