OPERATION MANUAL Sumitomo Heavy Industries, Ltd.
SRDK Series CRYOCOOLER 14
1-3 THEORY OF OPERATION
1-3 THEORY OF OPERATION
The SUMITOMO Helium Refrigerator operates on the GM (Gifford-McMahon) cycle.
The GM cycle is shown schematically in Figure 1.2 and consisted of a cylinder, closed at both ends, and
containing a displacer of a length about three quarters of the cylinder. The displacer is connected to a
drive mechanism so that it can be operated reciprocating action in the cylinder. The two volumes, one for
above and another for below the displacer, can be varied from zero to maximum but the total volume
remains constantly.
Figure 1.2 SCHEMATIC DIAGRAM OF GM CYCLE REFRIGERATOR
The two spaces are connected through a thermal regenerator and to a gas supply. The gas supply
system is consisted of inlet and outlet valves, a helium gas compressor and high and low pressure
reservoirs. The valves are coupled to the rotary drive mechanism and their operation is synchronized with
the position of the displacer. A heat exchanger is included downstream of the helium gas compressor to
cool down the gas to ambient temperature after compression.
The pressure above and below the displacer will be the same level except for small pressure drops across
the regenerator when gas is flowing through it. The basic function for the displacer will be required to
displace a volume in the cylinder so that the gas will be moved up and down in the cylinder without
mechanical work.
Pressure in the system is increased or decreased by operation of the inlet or outlet valves.
The displacer is fit loosely in the cylinder except at the top equipped with a dynamic (sliding) seal to prevent
gas leakage through the space between displacer and cylinder.
The regenerator will be consisted of metallic material divided finely will cool the gas passing downward to
the cold space and heat the gas passing upward from the cold space.
DisplacerRegenerator
Inlet Valve
Outlet Valve
Compressor
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