Abstract: A closed refrigeration system in which a fluid refrigerated can be circulated includes a heater for converting the fluid to gas at a high pressure, an expansion chamber downstream of the heater, the expansion chamber including a cylindrical chamber with an inlet adapted for introducing the gas tangentially into the chamber, and an outlet coaxial with the chamber but of smaller diameter so that conservation of angular momentum increases the tangential velocity of the gas as it flows through the expansion chamber, producing an approximately isentropic expansion. A compression chamber is connected to the outlet of the expansion chamber, the compression chamber being approximately a mirror image of the expansion chamber so that the fluid undergoes approximately isentropic compression in passing through the compression chamber. A condenser condenses the fluid from the compression chamber to a liquid, which is circulated back to the heater.