Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B35/00—Piston pumps specially adapted for elastic fluids and characterised by the driving means to their working members, or by combination with, or adaptation to, specific driving engines or motors, not otherwise provided for
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
  • F25B9/00—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
  • F25B9/14—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the cycle used, e.g. Stirling cycle
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
  • F25B9/00—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
  • F25B9/14—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the cycle used, e.g. Stirling cycle
  • F25B9/145—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the cycle used, e.g. Stirling cycle pulse-tube cycle
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
  • F25B2309/00—Gas cycle refrigeration machines
  • F25B2309/14—Compression machines, plants or systems characterised by the cycle used 
  • F25B2309/1408—Pulse-tube cycles with pulse tube having U-turn or L-turn type geometrical arrangements
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
  • F25B2309/00—Gas cycle refrigeration machines
  • F25B2309/14—Compression machines, plants or systems characterised by the cycle used 
  • F25B2309/1421—Pulse-tube cycles characterised by details not otherwise provided for
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
  • F25B2309/00—Gas cycle refrigeration machines
  • F25B2309/14—Compression machines, plants or systems characterised by the cycle used 
  • F25B2309/1423—Pulse tubes with basic schematic including an inertance tube
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
  • F25B2309/00—Gas cycle refrigeration machines
  • F25B2309/14—Compression machines, plants or systems characterised by the cycle used 
  • F25B2309/1424—Pulse tubes with basic schematic including an orifice and a reservoir

Definitions

• This invention relates generally to cryocoolers, and more particularly to a solid state cryocooler.
• a cryocooler using a Stirling cycle can obtain cryogenic temperatures by repeatedly compressing and expanding a working gas, it has become widely used in cooling operations, such as for cooling of superconducting elements, refining and separation of gases, infrared ray sensors, or the like.
• the operation principle of a Stirling cryocooler uses this Stirling cycle, relates to the rising and falling of a compression piston and a displacer in accordance with a refrigeration cycle.
• a Stirling cryocooler typically includes a compressor having a compression piston, a regenerator having a regenerating agent, a displacer forming an expansion chatnber and a compression chamber, a cooling part formed between the expansion chamber and the regenerator, and a heat rejection part formed around the compression chamber.
• a working gas is sealed under high pressure in a hermetically sealed flow passage constituted by these members, and the compression piston, of the compressor, and the displacer are reciprocated with a phase difference therebetween.
• the compression piston is displaced by mechanical power, so that the pressure of the working gas in the sealed space is changed.
• the working gas in the expansion chamber is expanded, to cool, using the displacer moving in synchronization with the periodic change of this pressure. Therefore, a high heat efficiency can usually be achieved.
• Pulse tube cryocooler typically include a compressor to repetitively feed and suction a working gas, a regenerator, coupled to the compressor through a heat rejection part and having a regenerating agent, a pulse tube, coupled to the regenerator through a cooling part, and a buffer tank coupled to this pulse tube through a heat rejection part and an inertance tube.
• a working gas such as helium, nitrogen or hydrogen can be sealed under high pressure in a hermetically sealed space of this pulse tube cryocooler. Then, similarly to the foregoing Stirling cryocooler, expansion and compression of the working gas is repeated by the compressor to form a pressure amplitude.
• the working gas in the pulse tube oscillates in the flow passage, such that it functions as the displacer in the foregoing Stirling cryocooler example. Accordingly, the working gas can be made to work by controlling the phase of the displacement of the oscillating working gas and the pressure wave. Heat is rejected from the heat rejection parts, and heat is absorbed in the cooling part which becomes a cold head of the cryocooler, such that a cryogenic temperature state is formed.
• the inertance tube and the buffer serve to control the phases of the displacement of the oscillating working gas relative to the pressure wave created by the compressor.
• the displacer installed in the Stirling cryocooler is not necessary, and instead of the displacer, the high pressure gas is oscillated so that the working gas can be compressed and expanded. Therefore, there are no movable parts in the low temperature portion. Thus, since mechanical oscillation does not exist at a cooling head, an equipment structure becomes simple, resulting in high efficiency and reliability.
• a cryocooler comprises a gas expander, a gas reservoir in fluid communication with the gas expander, and a gas compressor in fluid communication with and between the reservoir and the gas expander.
• the gas compressor is an electrochemical cell coupled to a source of electricity. With this construction, a gas is compressed by the operation of the electrochemical cell and the gas is subsequently passed to and from the gas expander whereby a refrigeration is produced .
• BRIEF DESCRIPTION OF THE DRAWING Fig. 1 is a schematic view of the cryocooler of the present invention.
• Fig. 2 is a schematic view of the membrane electrode assembly of the cryocooler of Fig. 1.
• Fig. 3 is a schematic view of multiple membrane electrode assemblies being coupled in series.
• Fig. 4 is a schematic view of pressure conditioning system that may be utilized with the cryocooler of Fig. 1.
• Fig. 5 is a chart comparing the specific heat temperature dependence of normal hydrogen to helium over a range of pressures and temperatures .
• Fig. 6 is a schematic view of the cryocooler of the present invention in another preferred form.
• the cryocooler 10 is a closed system which includes a reservoir 11, an electrochemical cell or proton conductive membrane (PCM) compressor 12 coupled to a source of AC current, and a gas expander in the form of a pulse tube expander module 13.
• PCM proton conductive membrane
• the compressor 12 includes an ion conductive membrane such as a proton conductive membrane 17 positioned between a pair of electrically conductive electrodes 18 and 19, as details of which and the operation of which is described in U.S. Patent No. 6,489,049 and incorporated herein by reference.
• the pulse tube expander module 13 includes a regenerator 21, a pulse tube 22, and in inertance tube 23.
• the regenerator 21 has a heat rejection part or aftercooler 25 and a cooling part or cold heat exchanger 26.
• the pulse tube 22 includes, a heat rejection portion or hot heat exchanger 27.
• the expander module 13 is based upon the pulse tube design in which the gross refrigeration capacity is achieved passively through the use of fixed, carefully tuned flow geometry.
• the solid state PCM compressor 1.2 generates an oscillating hydrogen pressure wave by energizing a proton conductive membrane 17 with an AC current through the electrodes 18 and 19.
• the pressure differential across a proton conductive membrane results in a chemical potential across the membrane that generates electricity.
• the use of the PCM compressor is based on the fact that the system is reversible in that ions can be made to flow against the pressure gradient though the application of an excitation current.
• the proton conductive membrane 17 and the pair of electrodes 18 and 19 form a compressor 12 that allows free passage of working fluid to and from the proton conductive membrane 17 as illustrated in Figure 2. Electricity is supplied to force the ion flow against the pressure gradient. Positively charged ions pass through the membrane while electrons travel through the electrodes to and from the power supply.
• the electrodes include a catalyst to promote the electrochemical reactions occurring at each electrode-proton conductive membrane interface.
• the hydrogen gas on the low- pressure side is oxidized resulting in the creation of protons and electrons.
• the protons are pulled through the membrane 17 by the chemical potential created by the reduction of the hydrogen ions back into hydrogen gas on the high pressure side.
• An oscillating flow, as is required to drive a pulse tube expander, is created by the excitation of the proton conductive membrane compressor 12 with an AC current.
• the compressor 12 described herein has been evaluated against a representative set of pulse tube requirements assuming an arbitrary 70 degrees Kelvin refrigeration temperature (see Table 1) .
• the baseline parameters are based upon a helium design; the actual flow rate is likely lower because of the higher volumetric heat capacity of hydrogen. Simplifying assumptions are made to obtain an input power estimate. It was assumed that hydrogen is compressed uniformly into the expander volume prior to any flow into the pressure reservoir 11. It was further assumed that the amount of mass delivered is sufficient to achieve a stable pressure ratio of 1.3 under isothermal compression at the prescribed operating frequency.
• V open circuit RT/2F (ln (P ratio ) )
• J? is the specific gas constant (8.314 kJ/kg°K)
• T is the cell operating temperature (K)
• F Faraday's constant (96,487 coulombs).
• the open circuit voltage is approximately 3.3 mV.
• the maximum allowable voltage drop due to resistance losses must be limited to 0.66mV.
• the total voltage across the compressor 17 is 3.96mv.
• Pressure pulses are supplied in sine waves having a RMS mass flow rate of 1.06g/sec.
• the mass flow rate is directly proportional to the current flow through the proton conductive membrane compressor 12 stack as given by:
• n is the number of electrons involved in the process (2 for molecular hydrogen)
• A is Avogadro's number (6.02e23)
• E is the charge on a single electron (1.602e-19 C)
• MW is the molecular weight of hydrogen gas.
• Substituting values gives an average current flow of approximately 102 kAmps.
• the proton conductive membrane compressor 12 impedance must be limited to 6.4e-9 ohms in order for the voltage loss due to internal resistance to remain below 0.66mv.
• the minimum proton conductive membrane 17 area required to achieve the desired electrical efficiency is 1.9m 2 .
• the corresponding current flux is 0.053Amps/cm 2 .
• the design closes mathematically, the operating current is unacceptably high for practical application.
• the required current can be sufficiently reduced.
• the voltags is additive due to the series connection.
• the hydrogen flow and current are in parallel across all the compressors 12. Assuming a stack of 1O 5 compressors 12 yields a pulse voltage of 39.6 Volts (3.96mV each) and a much more practical pulse current of 10.2 Amps.
• the required input power is in a range typical of present day pulse tube cryocoolers.
• the hydrogen is cycled in a sine wave, so pumping power is only applied for the compression half of each cycle.
• the power estimate for this analysis comes out to 70 W. Given the conservative assumptions that support this calculation, this estimate compares favorably with the approximately 50 W one would expect to achieve with current state of the art.
• cryocooler in another preferred form of the invention.
• the cryocooler is a recuperative cryocooler system, rather than the cryocooler of Figs. 1-5 which is shown to be a regenerative cryocooler system.
• the recuperative cryocooler system shown in Fig. 6 is a simple Joule-Thomson cycle system, however, it should be understood that any recuperative or regenerative system which uses a compressor may be included in the present invention.
• the cryocooler 40 includes a compressor 41, a liquid reservoir 42, a first gas conduit 43 extending between the compressor 41 and the liquid reservoir 42, a second gas conduit 44 extending between the liquid reservoir 42 and the compressor 41, an expansion valve 45 coupled to the first conduit 43, and a heat exchanger 46 is thermal communication with the first and second conduits to transfer heat therebetween.
• the compressor 41 is an electrochemical cell of the same construction and operation previously recited in detail with regard to the system of
• the operation of the system is essentially the same as conventional Joule-Thomson cycle system except for the novel use of an electrochemical cell as the compressor.
• the electrochemical cell operates to compress the working fluid thereby forcing it to pass through the first conduit
• cryocooler operates without vibration as it does not include the moving parts associated with cryocooler compressors of the prior art.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Compressors, Vaccum Pumps And Other Relevant Systems (AREA)

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• 2005
  • 2005-05-16 US US11/130,424 patent/US20060254286A1/en not_active Abandoned
• 2006
  • 2006-05-15 WO PCT/US2006/018561 patent/WO2006124679A2/en active Application Filing
  • 2006-05-15 EP EP06759755A patent/EP1882131A4/en not_active Withdrawn
  • 2006-05-15 JP JP2008512379A patent/JP2008541004A/ja active Pending
• 2007
  • 2007-11-04 IL IL187133A patent/IL187133A0/en unknown

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