Refrigeration – Storage of solidified or liquified gas – Liquified gas transferred as liquid
Reexamination Certificate
1998-10-06
2001-03-20
Doerrler, William (Department: 3744)
Refrigeration
Storage of solidified or liquified gas
Liquified gas transferred as liquid
C062S055500, C062S402000
Reexamination Certificate
active
06202421
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a detachable cryogenic refrigerator expander.
Systems operating at cryogenic temperatures generally have a cryogenic refrigeration unit attached to the system to minimize or eliminate boil-off of the cryogenic coolant. A cryogenic refrigeration unit including an expansion device, compressor, and heat exchanger is known. High pressure fluid from the compressor is passed through the heat exchanger and introduced into the expansion device. Expansion of the fluid in the expansion device reduces the temperature and pressure of the fluid. Heat energy is transferred from the expanding fluid by the performance of mechanical work.
When the expansion device must be removed, either for maintenance or replacement, the cryogenic system is typically exposed to warmer temperatures and potential contaminates. Maintenance of the unit generally requires that the cryogenic system be shut down for at least a day.
SUMMARY OF THE INVENTION
A light weight, easily maintained work extraction system for cooling a gas provides reliable, low cost refrigeration in about the 4 K to 40 K temperature range. The system includes an expansion engine assembly and a hydraulic work extractor assembly. When an inlet valve of the expansion engine assembly is opened, gas enters the cold end and expands, raising an expansion piston and raising a hydraulic piston coupled to the expansion piston. This forces hydraulic fluid through a needle valve creating a head due to flow friction. The inlet valve is closed when the piston is partially up the stroke to allow the gas to expand to a lower pressure. When the full stroke is reached the exhaust valve is opened and pneumatic spring pistons push the expansion piston back down, exhausting the gas in the cylinder for the next cycle.
According to the invention, a detachable work extraction system includes an expansion engine including a self-sealing coupling adapted to detachably connect the expansion engine to a cold box, and a hydraulic work extractor operatively connected to the expansion engine. A gas can travel from the cold box to the expansion engine through the self-sealing coupling. The gas is cooled by expansion of the gas in the expansion engine and work produced by the expansion of the gas is dissipated by the hydraulic work extractor.
Embodiments of this aspect of the invention may include one or more of the following features.
The self-sealing coupling includes a spring loaded seal. The expansion engine includes a cylinder housing a piston. The cylinder has a first self-sealing coupling defining an inlet and a second self-sealing coupling defining an outlet. The first and second self-sealing couplings each have a spring loaded seal. In the absence of an external force applied to the seal, the seal prevents flow of gas through the couplings.
An inlet valve assembly, for example, an electric actuated spring biased valve, controls the flow of gas through the inlet. An outlet valve assembly, for example, a pneumatic actuated spring biased valve, controls the flow of gas through the outlet.
In the illustrated embodiment, a return assembly, for example, a pneumatically controlled return assembly, lowers the piston. The work extraction system includes a displacement transducer for monitoring the position of the piston.
The hydraulic work extractor includes a cylinder, piston, and oil loop. A control valve of the hydraulic work extractor dissipates the work produced by the expansion of the gas. The control valve includes a throttle valve and a check valve.
According to another aspect of the invention, a refrigeration system includes a cold box and a detachable work extraction system. The cold box has a first self-sealing coupling, and an expansion engine of the work extraction system has a second self-sealing coupling for detachably connecting the expansion engine to the cold box self-sealing coupling.
Embodiments of this aspect of the invention may include a hydraulic work extractor operatively connected to the expansion engine.
According to another aspect of the invention, a method for connecting a cold box and a work extraction engine includes detachable connecting the work extraction engine to the cold box, and removably disconnecting the work extraction engine from the cold box without substantial loss of gas from the cold box.
An advantage of this system is its ease of maintenance. Self sealing couplings allow the expander module to be removed and replaced without warming the system or contaminating the inner components. With a dual expander arrangement, the system may not even be required to be shut down. The hydraulic work extraction device allows the expander module to be light enough to be removed by one person and reattached relatively easily.
REFERENCES:
patent: 3699696 (1972-10-01), Rhoton
patent: 4277950 (1981-07-01), Eigenbrod et al.
patent: 5429155 (1995-07-01), Brzyski et al.
patent: 5687574 (1997-11-01), Longsworth et al.
patent: 5910104 (1999-06-01), Dobak et al.
Bushko Dariusz Antoni
Maguire James F.
Sidi-Yekhelf Ahmed
Winn Peter M.
American Superconductor Corporation
Doerrler William
Fish & Richardson P.C.
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