High efficiency modular cryocooler with floating piston expander

A system for providing a low temperature fluid, said system comprising:

• a compressor;
• a recuperative heat exchanger disposed in fluid communication with said compressor;
• and
• a floating piston expander disposed in fluid communication with said heat exchanger;
• said compressor providing fluid under pressure, said compressor having an input and an output;
• said recuperative heat exchanger having discrete first and second flow paths extending therethrough, said first flow path being coupled to said input and said second flow path being coupled to said output;
• and
• said floating piston expander being disposed in serial fluid communication with said first and second flow paths, wherein said first flow path is coupled through said floating piston expander to said second flow path.

A system for providing a low temperature fluid, said system comprising:

• a compressor to provide fluid under pressure, said compressor having an input and an output;
• a heat exchanger disposed in fluid communication with said compressor, said heat exchanger having discrete first and second flow paths extending therethrough, said first flow path being coupled to said input and said second flow path being coupled to said output;
• a floating piston expander disposed in serial fluid communication with said first and second flow paths, wherein said first flow path is coupled through said floating piston expander to said second flow path;
• said floating piston expander having a piston disposed for periodic axial movement within an elongated chamber, said piston having a range of motion extending between a cold displacement volume disposed at one end of said chamber and a warm displacement volume disposed at an other end of said chamber, said first and second flow paths being selectively coupled to said cold displacement volume, and first and second ballast volumes being selectively coupled to said warm displacement volume;
• and
• said first and second ballast volumes being alternately couplable to said warm displacement volume to generate movement of said piston from said cold displacement volume towards said warm displacement volume and generate substantially isentropic expansion of the fluid under pressure disposed within said cold displacement volume.

An expander adapted for use in a thermodynamic cycle, said expander comprising:

• an expansion chamber;
• a piston adapted for periodic movement within said expansion chamber, said piston being free from an external drive mechanism;
• said piston being actuated by alternately coupling and decoupling fluid thereto;
• a plurality of variable force valves to effect said coupling and decoupling;
• a sensor adapted to detect the location of said piston within said expansion chamber, said sensor being free from physical contact with said piston;
• and
• a computer coupled to said sensor to control operation of said plurality of variable force valves.

A method for producing a cold fluid, said method comprising the steps of:

• (a) utilizing a compressor having an input and an output to provide fluid under pressure;
• (b) disposing a heat exchanger in fluid communication with said compressor, said heat exchanger having discrete first and second flow paths extending therethrough, said first flow path being coupled to said input and said second flow path being coupled to said output;
• (c) disposing a floating piston expander in serial fluid communication with said first and second flow paths, said floating piston expander having a piston adapted for periodic, axial movement within an expansion chamber, said piston having a range of motion extending between warm and cold displacement volumes disposed at opposite ends of said expansion chamber, wherein said first flow path is selectively coupled through the cold displacement volume of said floating piston expander to said second flow path;
• (d) introducing the fluid under pressure at a first temperature through said first flow path into said cold displacement volume;
• (e) pre-cooling the fluid flowing in said first flow path from said first temperature to a second temperature lower than said first temperature;
• (f) periodically coupling a low pressure fluid to said warm displacement volume to generate movement of said piston from said cold displacement volume towards said warm displacement volume to expand said cold displacement volume and expand the pressurized fluid flowing into said cold displacement volume from said first flow path, from said pressure to a substantially lower pressure to reduce the temperature thereof to a third temperature substantially lower than said second temperature;
• (g) decoupling said low pressure fluid from said warm displacement volume and coupling a high pressure fluid to said warm displacement volume to move said piston towards said cold displacement volume to cause fluid at said third temperature and at said lower pressure to flow from said cold displacement volume at a substantially constant pressure into said second flow path;
• (h) providing a direct heat exchange between fluid flowing in said first flow path and fluid flowing in said second flow path to effect the pre-cooling of the fluid flowing in said first flow path substantially to said second temperature and a warming of the fluid flowing in said second flow path;
• and
• (i) supplying the fluid from said second flow path to said compressor to provide the fluid under pressure for introduction into said first flow path.