Refrigeration cycle for liquid oxygen densification

A closed-loop refrigeration system for liquid oxygen densification comprising:

• a compressor configured to compress a working fluid having between 85 mol % and 95 mol % neon and/or helium and between 5 mol % and 15 mol % nitrogen and/or oxygen from a pressure above ambient pressure to a pressure between 120 psia and 155 psia;
• a heat exchanger in fluid communication with the outlet of the compressor configured to receive the compressed working fluid and cool the compressed working fluid via indirect heat exchange with a gaseous nitrogen stream and a liquid nitrogen stream to produce a cold, compressed working fluid;
• a turbine in fluid communication with the heat exchanger and configured to expand the cold, compressed working fluid and produce a refrigeration stream of expanded working fluid;
• an oxygen cooler in fluid communication with the turbine, the oxygen cooler configured to receive a stream of liquid oxygen and the refrigeration stream from the turbine, and subcool the stream of liquid oxygen to a temperature less than 66.5 K via indirect heat exchange with the refrigeration stream of expanded working fluid to produce a densified liquid oxygen stream;
• and
• a recirculating conduit configured to recirculate the warmed refrigeration stream to an inlet of the compressor where the warmed refrigeration stream is compressed as the working fluid.

A method of densifying a liquid oxygen stream in a closed-loop refrigeration cycle, the method comprising the steps of:

• compressing a working fluid having between about 85 mol % and about 95 mol % neon and/or helium and between 5 mol % and 15 mol % nitrogen and/or oxygen in a compressor from a pressure above ambient pressure to a pressure between 120 psia and 155 psia;
• cooling the compressed working fluid via indirect heat exchange with a gaseous nitrogen stream or a liquid nitrogen stream or both to produce a cold, compressed working fluid;
• expanding the cold, compressed working fluid in a turbine to produce a refrigeration stream of expanded working fluid at a temperature of less than 66.5 K;
• subcooling a stream of liquid oxygen via indirect heat exchange with the refrigeration stream of expanded working fluid to produce a densified liquid oxygen stream;
• and
• recirculating the warmed refrigeration stream to the compressor;
• wherein the warmed refrigeration stream is compressed as the working fluid to form a closed-loop refrigeration cycle.