Cryogenic refrigerator employing counterflow passageways

Abstract

A cryogenic refrigerator is disclosed having an expander piston reciprocally mounted within a fluid-tight housing. High pressure gas is supplied to a variable cold volume at one end of the piston through a passageway in the piston when the variable cold volume is at its minimum. Differential forces on the opposite end of the piston cause the piston to move, thereby enlarging the variable cold volume. The expanded cooled gas in the variable volume is vented out through the piston passageway which has been moved into fluid communication with a venting conduit when the variable volume is at its maximum. A heat exchanger operatively disposed between the gas supply and venting conduit allows the cold venting gas to cool the incoming high pressure gas. The cycle of operation employs isothermal expansion for obtaining cooling with a theoretical efficiency equal to that of a Carnot cycle thus; the refrigerator is more efficient than those using a Joule-Thompson cycle and is not limited to any specific refrigeration temperature (e.g., the boiling temperature of the working fluid).