Cryostat refrigeration system using mixed refrigerants in a closed vapor compression cycle having a fixed flow restrictor
AssigneeAPD Cryogenics, Inc.
InventorsRalph C. Longsworth, Mikhail J. Boiarsky, Ajay Khatri
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Abstract
A closed cycle cryogenic refrigerating system with a fixed restrictor operates with a compressor inlet pressure in a range of 0.1 Mpa to 0.4 Mpa and compressor discharge pressure in a range of 1.5 Mpa and 2.5 Mpa. A basic cryogenic refrigerant mixture is used to which is added approximately 3% to 25% of helium, hydrogen and/or neon. A ratio of refrigerant density at the inlet of the fixed restrictor between steady-state operation and operation at the beginning of cool-down is in an approximate range of 7 to 17. Relatively rapid cool-down is achieved and evaporator temperature is maintained in an approximate range of 70K to 120K.
Claims22
A closed cycle refrigerating system for steady-state cooling at a low cryogenic temperature and for cool-down from an elevated initial temperature toward said low cryogenic steady state temperature, comprising:
- an evaporator for circulating a low pressure, low temperature cryogenic refrigerant therein, said evaporator absorbing heat from a load whereby said refrigerant is heated and said load is cooled;
- a refrigerant compressor having a low pressure inlet in a range of 0.1 to 0.4 Mpa (1 to 4 atm) and a high pressure discharge in a range of 1.5 Mpa to 2.5 Mpa (15 to 25 Atm), said compressor receiving said heated low pressure refrigerant from said evaporator at said inlet and compressing said refrigerant to a high pressure at said discharge;
- an after-cooler for receiving a flow of said compressed refrigerant from said compressor, removing heat from said high pressure refrigerant, and rejecting said heat from said refrigerating system;
- a fixed restrictor having an outlet connected to an inlet of said evaporator, said fixed restrictor throttling said refrigerant flow from said high pressure to said low pressure, said refrigerant expanding through said restrictor and thereby becoming colder, said restrictor being fixed dimensionally and operative both for cool-down and for steady-state cooling;
- a regenerative heat exchanger having a high pressure side and a low pressure side, said high pressure side and said low pressure side being in heat exchange relationship, said high pressure side connecting between an outlet of said after-cooler and an inlet to said fixed restrictor, said low pressure side connecting between an outlet of said evaporator and said low pressure inlet to said compressor;
- said refrigerant being a mixture of refrigerant components having a density ratio in an approximate range of 7 to 17 during steady-state operation while maintaining an evaporator temperature in an approximate range of 70K to 120K, said ratio being between a density at the inlet to said fixed restrictor and a density at the high pressure inlet to said regenerative heat exchanger.
A closed cycle refrigerating system for steady-state cooling at a low cryogenic temperature and for cool-down from an elevated initial temperature toward said low cryogenic steady state temperature, comprising:
- an evaporator for circulating a low pressure, low temperature cryogenic refrigerant therein, said evaporator absorbing heat from a load whereby said refrigerant is heated and said load is cooled;
- a refrigerant compressor having a low pressure inlet in a range of 0.1 to 0.4 Mpa and a high pressure discharge in a range of 1.5 Mpa to 2.5 Mpa, said compressor receiving said heated low pressure refrigerant from said evaporator at said inlet and compressing said refrigerant to a high pressure at said discharge;
- heat transfer means for receiving a flow of said compressed refrigerant from said compressor, removing heat from said high pressure refrigerant, and rejecting at least a portion of said heat from said refrigerating system, high pressure cooled refrigerant leaving said heat transfer means,
- a fixed restrictor having an inlet receiving said cooled refrigerant from said heat transfer means and an outlet connected to an inlet of said evaporator, said fixed restrictor throttling said refrigerant flow from said high pressure to said low pressure, said refrigerant expanding through said restrictor and thereby becoming cold, said restrictor being fixed dimensionally and operative both for cool-down and for steady-state cooling,
- said refrigerant being a mixture of refrigerant components having a density ratio in an approximate range of 7 to 17 during operation while maintaining an evaporator temperature in an approximate range of 70K to 120K, said ratio being between a refrigerant density at the inlet to said fixed restrictor at steady-state and a refrigerant density at the inlet to said fixed restrictor at a start of cool-down.
Dependencies are inferred from the claim text.