GB1177651A - Method and Apparatus for Expanding a Gas. - Google Patents

Abstract

1,177,651. Refrigerating. H. SIXSMITH. 3 March, 1967 [4 March, 1966], No. 9660/66. Heading F4H. In a refrigeration system a gas is expanded by establishing a gaseous piston adjacent one end 11 of a chamber 10, introducing a predetermined mass of gas through an inlet line 12 to move the gaseous piston away from end 11, closing a valve 20 in inlet line 12 and continuing to move the gaseous piston away from end 11 so as to expand said predetermined mass of gas. End 11 has an outlet line 13 while the other end 14 of the chamber has an inlet line 15 and an outlet line 16, valves 21, 22, 23 being respectively provided in lines 13, 15, 16. The gaseous piston is established in a compressed state adjacent end 11 by supplying high pressure gas through line 15 with valves 20, 21, 23 closed. Valve 22 is then closed and valves 20 and 23 opened so that high pressure gas from inlet 12 moves the gaseous piston upwardly while gas is exhausted at low pressure through line 16. Valve 20 is then closed while valve 23 remains open so that the piston continues to move upwardly and the gas therebeneath is expanded. The expanded gas is exhausted through line 13 by admitting gas through inlet 15, and passed through a load 24 and a heat exchanger 27 to cool gas in line 12. The gas is compressed and cooled at 29 before being returned to line 12. The gas exhausted through line 16 is compressed and cooled at 33 before returning to line 15, lines 15 and 16 include flow regulators controlled by a device 35 in response to the temperature at the midpoint of either heat exchanger 27 or chamber 10. Alternatively the relative durations of the phases of the cycle or the degree of compression at 29, 33 may be controlled. Helium is employed as the working medium and the upper end of the chamber may be cooled to 12‹ K. by auxiliary refrigeration. Chamber 10 may be filled with porous material.