Remote recondenser with intermediate temperature heat sink

A cryogenic recondenser for recondensing gas evaporated from liquid cryogen retained in a storage vessel, the vessel having an outer housing, an inner container for liquid cryogen, a transfer tube from the outer housing to the inner container and a radiation shield surrounding the inner container and in thermal contact with the transfer tube, the recondenser comprising:

• external cooling means including a mechanical refrigerator positioned outside of the storage vessel;
• and
• a transfer line extending from the external cooling means and removeably suspended in the transfer tube, the transfer line comprising:
• a final section for transferring incoming cooled refrigerant from the external cooling means to a JT valve in communication with a recondensing heat exchanger and for returning refrigerant from the recondensing heat exchanger to the external cooling means in heat exchange relationship with the incoming refrigerant and
• an intermediate section for transferring cooled refrigerant from the external cooling means to a heat station positioned on the transfer line in thermal communication with but out of physical contact with the radiation shield to cool the radiation shield and for returning the refrigerant to the external cooling means out of heat exchange relationship with the incoming cooled refrigerant, the refrigerant of the final and intermediate sections of the transfer line being kept out of heat exchange relationship with each other.

A method of recondensing boil-off from a bath of cryogen retained in a storage vessel, the vessel having an outer housing, an inner container for liquid cryogen, a transfer tube from the outer housing to the inner container and a radiation shield surrounding the inner container and in thermal contact with the transfer tube, the method comprising the steps of:

• cooling a volume of refrigerant in an external cooling means which is remote from the storage vessel;
• transferring the cooled refrigerant in an intermediate section of a transfer line to a heat station position on the transfer line in thermal communication with but out of physical contact with the radiation shield to cool the radiation shield, the transfer line extending from the external cooling means and removably suspended in the transfer tube;
• returning the cooled refrigerant through the intermediate section of the transfer line from the heat station to the external cooling means;
• transferring incoming cooled refrigerant in a final section of the transfer line from the external cooling means to a JT valve in communication with a recondensing heat exchanger positioned in the inner container;
• expanding the cooled refrigerant through the JT valve to form a liquid and gas refrigerant mixture in the recondensing heat exchanger which is in heat exchange relation with the boil-off to cool the boil-off and thereby recondense the boil-off;
• and
• returning the refrigerant from the recondensing heat exchanger to the external cooling means through the final section of the transfer line in heat exchange relationship with the incoming refrigerant, the refrigerant of the final and intermediate sections of the transfer line being kept out of heat exchange relationship with each other.