GB2400902A - A pulse tube refrigerator - Google Patents

A pulse tube refrigerator Download PDF

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Publication number
GB2400902A
GB2400902A GB0406839A GB0406839A GB2400902A GB 2400902 A GB2400902 A GB 2400902A GB 0406839 A GB0406839 A GB 0406839A GB 0406839 A GB0406839 A GB 0406839A GB 2400902 A GB2400902 A GB 2400902A
Authority
GB
United Kingdom
Prior art keywords
pulse tube
foam
tube refrigerator
copper
heat exchanger
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB0406839A
Other versions
GB0406839D0 (en
GB2400902B (en
Inventor
Milind Diwakar Atrey
Wolfgang Ernst Stautner
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Siemens Magnet Technology Ltd
Original Assignee
Siemens Magnet Technology Ltd
Oxford Magnet Technology Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Siemens Magnet Technology Ltd, Oxford Magnet Technology Ltd filed Critical Siemens Magnet Technology Ltd
Publication of GB0406839D0 publication Critical patent/GB0406839D0/en
Publication of GB2400902A publication Critical patent/GB2400902A/en
Application granted granted Critical
Publication of GB2400902B publication Critical patent/GB2400902B/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

Links

Classifications

    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28HEAT EXCHANGE IN GENERAL
    • F28DHEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D17/00Regenerative heat-exchange apparatus in which a stationary intermediate heat-transfer medium or body is contacted successively by each heat-exchange medium, e.g. using granular particles
    • F28D17/02Regenerative heat-exchange apparatus in which a stationary intermediate heat-transfer medium or body is contacted successively by each heat-exchange medium, e.g. using granular particles using rigid bodies, e.g. of porous material
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25BREFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B9/00Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
    • F25B9/14Compression 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
    • F25B9/145Compression 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
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25BREFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2309/00Gas cycle refrigeration machines
    • F25B2309/003Gas cycle refrigeration machines characterised by construction or composition of the regenerator
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25BREFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2309/00Gas cycle refrigeration machines
    • F25B2309/14Compression machines, plants or systems characterised by the cycle used 
    • F25B2309/1412Pulse-tube cycles characterised by heat exchanger details
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25BREFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2309/00Gas cycle refrigeration machines
    • F25B2309/14Compression machines, plants or systems characterised by the cycle used 
    • F25B2309/1415Pulse-tube cycles characterised by regenerator details
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25BREFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2309/00Gas cycle refrigeration machines
    • F25B2309/14Compression machines, plants or systems characterised by the cycle used 
    • F25B2309/1418Pulse-tube cycles with valves in gas supply and return lines
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25BREFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B9/00Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
    • F25B9/10Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point with several cooling stages

Landscapes

  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Dispersion Chemistry (AREA)
  • Separation By Low-Temperature Treatments (AREA)
  • Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)

Abstract

A pulse tube refrigerator 1 has one or more stages 7,10, and each stage has a pulse tube 5,8 and a regenerative heat exchanger 6,9. The heat exchanger has a foam matrix material 13,14, which maybe metal or ceramic. The metallic foam matrix may be one of copper, copper bronze, stainless steel, lead, erbium nickel or holmium copper, and the ceramic foam matrix may include aluminium oxide or gadolinium compounds. The foam may have porosity of between 75% and 95%, or between 25% and 40%. The pulse tube refrigerator may also include at least one of warm end and cold end, and these ends may include recuperative heat exchangers 11,12, also comprising a foam material. The refrigerant used may be helium gas.

Description

PULSE TUBE REFRIGERATOR
This invention relates to a pulse tube refrigerator (PTR).
For the purpose of this application, a regenerative heat exchanger is one in which a fluid flows through a material which stores heat and when the same fluid flows through the material subsequently, then the stored heat is given up from the material to the fluid flow.
In operation of a pulse tube refrigerator, this occurs periodically. By contrast, a recuperative heat exchanger is one in which at least two different fluids are provided which may flow simultaneously and in particular do not flow through the same material.
A recuperative heat exchanger is not suitable for use in a pulse tube refrigerator because only a single gas component (e.g. He, Ne, or other gases) is used when operating the PTR, although recuperative heat exchangers are commonly used at the warm end and cold end of the pulse tubes of the PTR where they provide additional cooling, for example, a water cooled heat exchanger.
Another common use of the term regenerative relates to situations in which the material within the heat exchanger can be regenerated for further use if it becomes saturated. However, this type of material is also not appropriate for use in a pulse tube refrigerator because the PTR operates with a clean gas, so the matrix does not become saturated by other components, nor does the efficiency of the regenerator become reduced.
Pulse tube refrigerators (PTR) use regenerative heat exchangers to increase or decrease the temperature of a cryogenic liquid, typically Helium gas. Regenerator effectiveness is critical to performance of the PTR during the PTR operation. A matrix is provided in the regenerator through which Helium gas flows to lose or gain heat. The gas travels in a first flow direction through the regenerator matrix and in the process it gives off heat and thereby experiences a decrease in temperature. The specific heat capacity of the matrix material enables the heat extracted from the Helium to be stored in the matrix material and subsequently, when the gas travels back through the matrix in the reverse direction, it takes stored heat from the matrix and so experiences a temperature rise. To achieve high effectiveness, the regenerator matrix material has to satisfy stringent thermal performance requirements. These requirements are that the regenerator matrix materials have a high heat capacity compared to the gas heat capacity; that there is at least a minimum pressure drop, so requiring a high porosity; and that there is a high heat transfer area, usually achieved by means of a divided matrix in the form of mesh.
Conventionally, a metal mesh is used as the matrix material for a single stage regenerator operating between 300K and 25K or for the first stage of a two stage regenerator for a I OK or 4K PTR. Typically, the metal used to make the mesh is copper, stainless steel or phosphor bronze. However, fabrication of the meshes is a major task which involves making a die, punching and stacking the meshes manually in the regenerator tube and then aligning the meshes in the tube. The cost and time involved in this is quite high.
A second stage regenerator of a I OK PTR uses Pb as the regenerator matrix material and a 4K PTR typically uses Pb, ErNi, HCu2, or Gadolinium based compounds, depending upon the desired temperature of operation, as regenerator matrix materials, but these materials cannot be made up into a mesh, so they are used in the form of spherical balls instead. The use of spherical balls means that the porosity of the resulting matrix is only of the order of 25% to 35 %. A problem with this is that all the spherical balls must have the same diameter and must be packed in a particular way to achieve the desired porosity. As the ball diameter can vary about the nominal diameter and the packing may not be optimum, then it is not possible to guarantee that the desired porosity is actually achieved. This can have a drastic effect on performance.
In accordance with a first aspect of the present invention, a pulse tube refrigerator comprises one or more stages, wherein each stage comprises a pulse tube and a regenerative heat exchanger, the heat exchanger comprising a foam matrix material.
The present invention makes use of a foam matrix material to replace the mesh in the first stage regenerator of the PTR, thereby simplifying regenerator assembly and reducing costs and uses a foam matrix material to replace the spherical balls in the second stage regenerator, so improving the porosity. This latter means that any porosity can be chosen and it can be accurately controlled so improving performance of the PTR.
Preferably, the foam is of metal or ceramics. For the first stage of a 1 OK PTR, the foam is generally a metal foam. For the second stage, it may be a metal foam, or a foam based on ceramic compounds, or a combination of metal and ceramic compounds. For a PTR working at 4K and below, preferably, for the second stage regenerator, the ceramic compounds include Al2O3, GdAIO, aluminium nitride AIN-type ceramics, or further Gadolinium based compounds.
More preferably, the foam is one of copper, copper bronze, stainless steel, lead, erbium nickel or holmium copper foam.
The selection of the material type and quantity required in the regenerator stages of a PTR depends upon the targeted stage temperatures for any particular application. These materials are known to have suitable heat capacity properties, although other materials with similar properties could be used.
Porosity of the foam can be adapted as required for the particular application, for example for the first stage, preferably, the foam has a porosity in the range 75% to 95% and for the second stage, preferably, the foam has a porosity in the range 25% to 40%.
Preferably, the pulse tube refrigerator further comprises at least one of warm end and cold end recuperative heat exchangers, wherein the recuperative heat exchangers comprise a foam matrix material.
Typically, the foam matrix material for the recuperative heat exchangers comprises copper, copper bronze or other copper alloy type foam.
Typically, the regenerative heat exchanger operates in a temperature range of 2K to lOK.
An example of a pulse tube refrigerator in accordance with the present invention will now be described with reference to the accompanying drawings in which: Figure I illustrates a two stage pulse tube rcirigerator in accordance with the present invention, each stage incorporating a regenerative heat exchanger; and, Figure 2 shows the construction of the regenerative heat exchanger in one stage of Fig. 1 in more detail.
Fig. 1 shows a PTR system configuration 1 according to the present invention incorporating a regenerative heat exchanger (regenerator). Refrigerant gas, typically Helium, is supplied from a compressor through a valve system 3 which distributes the gas into a cold head comprising a high (room) temperature end 4, a first pulse tube 5 and first regenerator 6 connected between the high temperature end 4 and a first stage 7, and a second pulse tube 8 and a second regenerator 9 connected between the high temperature end 4 and a second stage 10. Each pulse tube 5, 8 is hollow and used for expansion and compression ofthe gas. Warm end l l and cold end 12 recuperative heat exchangers are provided at respective ends of each pulse tube 5, 8. Typically, these heat exchangers 11, 12 are made of metal meshes which are vacuum brazed or press fit into a copper casing across which heat transfer takes place. However, in a pulse tube refrigerator in accordance with the invention, these heat exchangers may also be provided with metal foams instead, giving further benefits in terms of manufacture and operation. Cias flow in the cold head is ac flow, in that it flows in and out through the same flow passages. Operation of the PTR produces cooling of the stages, in this case the first 7 and second 10 for a two stage refrigerator. The gas supply then returns to the compressor 1.
Each regenerator 6, 9 is filled with a foam 13, 14 which acts as a heat buffer to enable exchange of heat with the Helium gas of the PTR. The type of foam depends upon the temperature range of operation of the regenerator. In the first stage regenerator 6, in which conventionally the matrix is made from a metal mesh, copper or stainless steel foams are suitable for use as regenerator matrix materials, as the heat capacity of both materials is acceptable in the temperature range of 300-30 K. Furthermore, the porosity of a conventional metal mesh has a maximum of 75%, whereas the porosity of foam can be increased up to 95 % and this will help in reducing the pressure drop of Helium gas which is quite critical from the PTR performance point of view In the second stage regenerator 9, lead foam matrix material may be used for a 10K PTR, or a foam of compounds of ErNi for a 4K PTR. In the second stage the improvement in porosity using foams of materials with the same heat capacity as in a conventional regenerator matrix, is even more significant, increasing from the 25 % to 35% porosity achieved with spherical balls.
Fig. 2 shows one of the regenerators of Fig. 1 in more detail. The regenerator 6 comprises a stainless steel tube 15 and a matrix, in the form of a metal foam cylinder 16, inserted into the tube to replace the conventional metal mesh. In conventional regenerative heat exchangers for a PTR, it may be necessary to produce as many as 1500 pieces of mesh of a chosen porosity and form the matrix from these, whereas using a foam matrix material has the advantage that the regenerator matrix material can be manufactured in the finished cylindrical form and put into the regenerator tube directly, or brazed if necessary, so signif cantly reducing the time and cost of manufacturing. The present invention makes use of the properties that foams are very light materials, with a high mechanical strength. They are able to operate at the extremely low temperatures required for PTR's, which had previously been considered impractical due to the dramatic changes in the basic material properties expected at the operating temperatures of the high pressure Helium gas flowing through the matrix. Foams have got high porosity and high heat transfer area per unit volume, so they are advantageous both from functional as well as fabrication point of view.

Claims (8)

1. A pulse tube refrigerator comprising one or more stages, wherein each stage comprises a pulse tube and a regenerative heat exchanger, the heat exchanger comprising a foam matrix material.
2. A pulse tube refrigerator according to claim 1, wherein the foam comprises metal or ceramics.
l O
3. A pulse tube refrigerator according to claim I or claim 2, wherein the foam comprises one of copper, copper bronze, stainless steel, lead, erbium nickel or holmium copper foam.
4. A pulse tube refrigerator according to claim I or claim 2, the foam comprising a metal foam including ceramic compounds, wherein the ceramic compounds include Al203, GdA10,, MN-type ceramics, or further Gadolinium based compounds.
5. A pulse tube refrigerator according to any preceding claim, wherein the foam has a porosity in the range 75% to 95%.
6. A pulse tube refrigerator according to any preceding claim, further comprising at least one of warm end and cold end recuperative heat exchangers, wherein the recuperative heat exchangers comprise a foam matrix material.
7. A pulse tube refrigerator according to any preceding claim, wherein the regenerative heat exchanger operates in a temperature range of 2K to l OK.
8. A pulse tube refrigerator as hereinbcfore described with reference to the accompany drawings.
GB0406839A 2003-04-24 2004-03-26 Pulse tube refrigerator Expired - Fee Related GB2400902B (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GBGB0309191.5A GB0309191D0 (en) 2003-04-24 2003-04-24 Regenerative heat exchanger

Publications (3)

Publication Number Publication Date
GB0406839D0 GB0406839D0 (en) 2004-04-28
GB2400902A true GB2400902A (en) 2004-10-27
GB2400902B GB2400902B (en) 2005-09-21

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Application Number Title Priority Date Filing Date
GBGB0309191.5A Ceased GB0309191D0 (en) 2003-04-24 2003-04-24 Regenerative heat exchanger
GB0406839A Expired - Fee Related GB2400902B (en) 2003-04-24 2004-03-26 Pulse tube refrigerator

Family Applications Before (1)

Application Number Title Priority Date Filing Date
GBGB0309191.5A Ceased GB0309191D0 (en) 2003-04-24 2003-04-24 Regenerative heat exchanger

Country Status (2)

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US (1) US20050005613A1 (en)
GB (2) GB0309191D0 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ES2408381A1 (en) * 2011-10-14 2013-06-20 Consejo Superior De Investigaciones Científicas (Csic) Regeneration medium suitable for use in heat exchangers and method associated with said medium

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008057924A (en) * 2006-09-01 2008-03-13 Sumitomo Heavy Ind Ltd Cold storage type refrigerator, its cylinder, cryopump, recondensing device, superconductive magnet device and semiconductor detector
JP4668238B2 (en) * 2007-05-08 2011-04-13 住友重機械工業株式会社 Cold storage refrigerator and pulse tube refrigerator
DE102016220368A1 (en) 2016-10-18 2018-04-19 Leybold Gmbh Coated heat regenerating material for use at very low temperatures

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5673561A (en) * 1996-08-12 1997-10-07 The Regents Of The University Of California Thermoacoustic refrigerator
US6314740B1 (en) * 1997-10-20 2001-11-13 Cornelis Maria De Blok Thermo-acoustic system
WO2002042707A1 (en) * 2000-11-27 2002-05-30 Stork Prints B.V. Heat exchanger

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US4077853A (en) * 1975-03-25 1978-03-07 Stauffer Chemical Company Method of metallizing materials
US5332029A (en) * 1992-01-08 1994-07-26 Kabushiki Kaisha Toshiba Regenerator
WO1994018433A1 (en) * 1993-02-12 1994-08-18 Ohio University Microminiature stirling cycle cryocoolers and engines
US5465702A (en) * 1994-05-27 1995-11-14 Ferrenberg; Allan J. Regenerated engine with improved heating and cooling strokes
CN1195815C (en) * 1996-10-30 2005-04-06 株式会社东芝 Cold accumulation material for ultra-low temp., refrigerating machine using the material and heat shield material
US6591609B2 (en) * 1997-07-15 2003-07-15 New Power Concepts Llc Regenerator for a Stirling Engine
JP4672160B2 (en) * 2000-03-24 2011-04-20 株式会社東芝 Regenerator and regenerative refrigerator using the regenerator

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5673561A (en) * 1996-08-12 1997-10-07 The Regents Of The University Of California Thermoacoustic refrigerator
US6314740B1 (en) * 1997-10-20 2001-11-13 Cornelis Maria De Blok Thermo-acoustic system
WO2002042707A1 (en) * 2000-11-27 2002-05-30 Stork Prints B.V. Heat exchanger

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ES2408381A1 (en) * 2011-10-14 2013-06-20 Consejo Superior De Investigaciones Científicas (Csic) Regeneration medium suitable for use in heat exchangers and method associated with said medium

Also Published As

Publication number Publication date
US20050005613A1 (en) 2005-01-13
GB0406839D0 (en) 2004-04-28
GB0309191D0 (en) 2003-05-28
GB2400902B (en) 2005-09-21

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Legal Events

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732E Amendments to the register in respect of changes of name or changes affecting rights (sect. 32/1977)

Free format text: REGISTERED BETWEEN 20090423 AND 20090429

PCNP Patent ceased through non-payment of renewal fee

Effective date: 20100326