Precooling system for joule-thomson probe

A method for cooling a distal cold tip of a probe, comprising:

• providing a closed primary loop, said primary loop including a primary compressor, a primary heat exchanger distal of said primary compressor, and a primary expansion element distal of said primary heat exchanger;
• providing a closed secondary loop, said secondary loop including a secondary compressor, a primary/secondary heat exchanger distal of said secondary compressor, and a secondary expansion element distal of said primary/secondary heat exchanger;
• compressing a refrigerant in said secondary loop with said secondary compressor;
• cooling said compressed refrigerant in a high pressure secondary side of said primary/secondary heat exchanger;
• isenthalpically expanding said refrigerant with said secondary expansion element;
• warming said expanded refrigerant in a low pressure secondary side of said primary/secondary heat exchanger;
• returning said expanded refrigerant to an inlet of said secondary compressor;
• compressing a gas mixture in said primary loop with said primary compressor;
• cooling said compressed gas mixture in a high pressure side of said primary heat exchanger;
• cooling said compressed gas mixture in a high pressure primary side of said primary/secondary heat exchanger;
• isenthalpically expanding said gas mixture with said primary expansion element to still further cool said gas mixture;
• applying said expanded gas mixture to the cold tip, to lower the temperature of the cold tip;
• warming said expanded gas mixture in a low pressure side of said primary heat exchanger;
• and
• returning said expanded gas mixture to an inlet of said primary compressor.

A method for cooling a cold tip of a probe, comprising:

• providing a gas mixture capable of isenthalpically expanding to a temperature below 183 K from a pressure of no more than 420 psia;
• providing a closed primary loop having a compressor for pressurizing said gas mixture to a pressure of no more than 420 psia, at least one primary heat exchanger, and a primary expansion element adjacent to a metallic heat transfer element in said cold tip;
• providing a closed secondary loop having a compressor, a primary/secondary heat exchanger, and a secondary expansion element;
• placing said heat transfer element in contact with a remote body to be cooled;
• compressing a refrigerant in said secondary loop;
• conducting said compressed refrigerant to a high pressure secondary section of said primary/secondary heat exchanger;
• cooling said compressed refrigerant in said high pressure secondary section of said primary/secondary heat exchanger;
• isenthalpically expanding said refrigerant in said secondary expansion element;
• conducting said expanded refrigerant to a low pressure secondary section of said primary/secondary heat exchanger;
• warming said expanded refrigerant in said low pressure secondary section of said primary/secondary heat exchanger;
• compressing said gas mixture to no more than 420 psia;
• conducting said compressed gas mixture to a high pressure section of said primary heat exchanger;
• cooling said compressed gas mixture in said high pressure section of said primary heat exchanger;
• conducting said compressed gas mixture to a high pressure primary section of said primary/secondary heat exchanger;
• cooling said compressed gas mixture in said high pressure primary section of said primary/secondary heat exchanger;
• isenthalpically expanding said gas mixture in said primary expansion element to still further cool said gas mixture to below 183 K;
• absorbing heat from said heat transfer element by contact with said expanded gas mixture, to cool said heat transfer element to below 180 K;
• and
• absorbing heat from said body to be cooled, by contact with said heat transfer element.

A miniature mixed gas refrigeration system, comprising:

• a closed primary loop for circulating a gas mixture, with a high pressure primary flow path and a low pressure primary flow path, said primary loop including a primary compressor, and a primary expansion element for isenthalpically expanding said gas mixture from said high pressure primary flow path to said low pressure primary flow path;
• and
• a closed secondary loop for circulating a refrigerant, with a high pressure secondary flow path and a low pressure secondary flow path, said secondary loop including a secondary compressor, a primary/secondary heat exchanger, and a secondary expansion element for isenthalpically expanding said refrigerant from said high pressure secondary flow path downstream of said primary/secondary heat exchanger to said low pressure secondary flow path upstream of said primary/secondary heat exchanger;
• wherein said high pressure primary flow path, said high pressure secondary flow path, and said low pressure secondary flow path pass through said primary/secondary heat exchanger in a heat exchange relationship;
• and
• wherein said low pressure primary flow path bypasses said primary/secondary heat exchanger.

A miniature mixed gas refrigeration system, comprising:

• a closed primary loop for circulating a gas mixture, with a high pressure primary flow path and a low pressure primary flow path, said primary loop including a primary compressor, a primary heat exchanger with high pressure and low pressure primary flow paths, a primary expansion element for isenthalpically expanding said gas mixture from said high pressure primary flow path downstream of said primary heat exchanger to said low pressure primary flow path upstream of said primary heat exchanger;
• and
• a closed secondary loop for circulating a refrigerant, with a high pressure secondary flow path and a low pressure secondary flow path, said secondary loop including a secondary compressor, a primary/secondary heat exchanger, and a secondary expansion element for isenthalpically expanding said refrigerant from said high pressure secondary flow path downstream of said primary/secondary heat exchanger to said low pressure secondary flow path upstream of said primary/secondary heat exchanger;
• wherein said high pressure primary flow path, said high pressure secondary flow path, and said low pressure secondary flow path pass through said primary/secondary heat exchanger in a heat exchange relationship;
• and
• wherein said low pressure primary flow path bypasses said primary/secondary heat exchanger.

A miniature mixed gas refrigeration system, comprising:

• a probe having a proximal handle and a distal cold tip;
• a closed primary loop for circulating a gas mixture, said primary loop including:
• a primary compressor connected to said probe;
• a miniature primary expansion element adjacent said cold tip for isenthalpically expanding said gas mixture from a high pressure flow path of said primary loop to a low pressure flow path of said primary loop;
• and
• a primary heat exchanger in said handle, said primary heat exchanger having high pressure and low pressure primary flow paths;
• a heat transfer body in said cold tip, said heat transfer body having an inner surface exposed to said expanded gas mixture and an outer surface exposed to ambient, for transferring heat from ambient to said gas mixture;
• and
• a closed secondary loop for circulating a refrigerant, said secondary loop including:
• a secondary compressor connected to said probe;
• a secondary expansion element in said handle for isenthalpically expanding said refrigerant from a high pressure flow path of said secondary loop to a low pressure flow path of said secondary loop;
• and
• a primary/secondary heat exchanger in said handle, said primary/secondary heat exchanger having a high pressure primary flow path, a high pressure secondary flow path, and a low pressure secondary flow path;
• wherein said low pressure primary flow path bypasses said primary/secondary heat exchanger.

A miniature mixed gas refrigeration system, comprising:

• a primary loop compressor for pressurizing a gas mixture to a pressure of approximately 420 psia, said primary compressor having an inlet and an outlet;
• a dual lumen primary loop tube, said primary loop tube having a high pressure lumen connected to an outlet of said primary compressor and a low pressure lumen connected to an inlet of said primary compressor;
• a primary loop heat exchanger attached to said primary loop tube, said primary loop heat exchanger having a high pressure passageway connected to said high pressure lumen and a low pressure passageway connected to said low pressure lumen;
• a primary loop expansion element connected to said high pressure passageway of said primary loop heat exchanger for isenthalpically expanding said gas mixture from said higher pressure to a lower pressure, said expanded gas mixture thereby cooling to a temperature of no greater than 183 K, said expanded gas mixture being in fluid flow communication with said low pressure passageway;
• a secondary loop compressor for compressing a refrigerant, said secondary compressor having an inlet and an outlet;
• a dual lumen secondary loop tube, said secondary loop tube having a high pressure lumen connected to an outlet of said secondary compressor and a low pressure lumen connected to an inlet of said secondary compressor;
• a primary/secondary heat exchanger attached to a distal end of said secondary loop tube, said primary/secondary heat exchanger having a primary loop high pressure passageway connected to said primary loop high pressure lumen, a secondary loop high pressure passageway connected to said secondary loop high pressure lumen, and a secondary loop low pressure passageway connected to said secondary loop low pressure lumen;
• and
• a secondary loop expansion element connected to said secondary loop high pressure passageway of said primary/secondary heat exchanger for isenthalpically expanding said refrigerant, said expanded gas mixture being in fluid flow communication with said secondary loop low pressure passageways;
• wherein said low pressure primary flow path bypasses said primary/secondary heat exchanger.