Helium phase separation refrigerator
AssigneeZero Point Cryogenics Incorporated
InventorsJohn Davis, Paul Kim, Marvin Hirschel, James Suranyi
Life of this patent
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Abstract
A cryogenic refrigerator uses a mixture of helium-3 and helium-4. Gaseous helium is pumped from a reservoir containing a liquid mixture of helium-3 and helium-4 to cause cooling and a phase separation into an upper helium-3 rich phase which floats at the top for further evaporation and a lower dilute phase below the helium-3 rich phase. This separation enables operation at temperatures typical of a helium-3 refrigerator while initial liquefaction of the mixture is easier than liquefaction of pure helium-3 and can use a smaller amount of helium-3. Embodiments of the refrigerator can provide continuous cooling.
Claims23
A cryogenic refrigerator comprising:
- one or more cooling elements arranged to at least partially liquefy helium from a gas containing a mixture of helium-3 and helium-4 to produce liquid helium having a sufficient concentration of helium-3 to enable the separation of the helium-3 and helium-4 when further cooled into separate helium-3 rich and dilute phases;
- a reservoir arranged to receive an incoming flow of helium including the liquid helium produced by the one or more cooling elements to form a volume of the liquid helium in the reservoir, and to expose a surface of the volume of the liquid helium to evaporation to cool the reservoir under evaporation of the liquid helium;
- and
- one or more pumps connected to the reservoir to remove evaporated gaseous helium from a space above the surface to form an outgoing flow of helium from the reservoir to the one or more pumps, and the one or more cooling elements being connected to an outlet of the one or more pumps to receive the helium of the outgoing flow of helium for continuous operation of the cryogenic refrigerator, the one or more pumps being arranged to sufficiently lower a pressure in the space above the surface of the liquid helium to cool the liquid helium to cause the liquid helium in the reservoir to separate into the separate helium-3 rich and dilute phases, where the helium-3 rich phase is adjacent to the surface for further evaporation into the space above the surface and further cooling as the one or more pumps in operation continue to remove evaporated helium-3 above the surface after phase separation.
A method of cryogenic refrigeration, the method comprising the steps of:
- cooling a helium gas comprising a mixture of helium-3 and helium-4 using one or more cooling elements to provide liquid helium containing helium-3 and helium-4 with a sufficient concentration of helium-3 to enable separation into helium-3 rich and helium-3 dilute phases;
- receiving an incoming flow of helium including the liquid helium produced by the one or more cooling elements in a reservoir to form a volume of the liquid helium in the reservoir, the volume of the liquid helium in the reservoir having a surface exposed to evaporation;
- providing one or more pumps connected to the reservoir to remove helium gas from a space above the surface;
- operating the one or more pumps to form an outgoing flow of helium from the reservoir to the one or more pumps and to cause the liquid helium within the reservoir to cool sufficiently by evaporation to cause a phase separation of the liquid helium into separate helium-3 rich and dilute phases, where the helium-3 rich phase is adjacent to the surface for further evaporation into the space above the surface;
- and
- continuing to operate the one or more pumps after separation into helium-3 rich and dilute phases to remove helium-3 rich gas above the surface evaporated from the helium-3 rich phase and further cool the reservoir, the one or more cooling elements receiving, from an outlet of the one or more pumps, the helium from the outgoing flow of helium for continuous operation of the cryogenic refrigerator.
Dependencies are inferred from the claim text.