US3713305A - DEVICE FOR PRODUCING COLD AT TEMPERATURE LOWER THAN THAT OF lambda -POINT OF HELIUM - Google Patents

DEVICE FOR PRODUCING COLD AT TEMPERATURE LOWER THAN THAT OF lambda -POINT OF HELIUM Download PDF

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US3713305A
US3713305A US00885542A US3713305DA US3713305A US 3713305 A US3713305 A US 3713305A US 00885542 A US00885542 A US 00885542A US 3713305D A US3713305D A US 3713305DA US 3713305 A US3713305 A US 3713305A
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space
communicating
helium
heat exchanger
pressure
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US00885542A
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English (en)
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F Staas
A Severijns
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US Philips Corp
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US Philips Corp
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    • 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
    • F25B9/12—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point using 3He-4He dilution
    • 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
    • F25B2341/00—Details of ejectors not being used as compression device; Details of flow restrictors or expansion valves
    • F25B2341/001—Ejectors not being used as compression device
    • F25B2341/0012—Ejectors with the cooled primary flow at high pressure

Definitions

  • ABSTRACT A device for coolin to tern eratures lower than that l 8 42 8 P [2 1 App] No of the A-point of helium, in which some high-pressure helium, after being cooled, expands to low-pressure [52] :J.S.C
  • V M is H .6 3,360,955 l/l968 Witter ..62/5 l4 15 Claims, 4 Drawing Figures mm 30 m;
  • the invention relates to a device for producing cold at temperatures lower than that of the A -point of helium.
  • the device comprises a source for high pressure helium which communicates with a supply system including a pre-cooler a counter-current heat exchanger in which the high-pressure helium is cooled to below its inversion temperature associated with said pressure, and a throttle device in which the high-pressure helium expands; the expanded helium then flows via an outlet system and the said counter-current heat exchanger, to a suction place for low-pressure helium.
  • Joule-Thompson cooling systems Devices of the above-mentioned type are known as Joule-Thompson cooling systems.
  • high-pressure helium is cooled by pre-coolers and in counter-current heat exchangers to below the inversion temperature associated with the said pressure, and is then expanded in a throttle valve, in which a temperature decrease occurs.
  • the expanded helium is then returned, via the said counter-current heat exchangers, to a compression plant.
  • the temperature at which the cold is produced depends upon the pressure which prevails after the throttle valve. In order to reach very low temperatures it is necessary to expand to very low pressures. A pressure of 1 atm.
  • SUMMARY OF THE NEW INVENTION municates on its one side, via one or more heat exchangers in which the helium cools to below the )t-t'emperature of helium and at least one controllable throttle valve, with a first place of the system of supply or outlet ducts, and communicates on its other side with a cold space, said space further communicating, via a vortex tube, with a second place of the device, where a lower pressure prevails than at the said first place.
  • a superleak should be understood to mean within the scope of the present invention, a mass of a material having the property that normal helium cannot pass said mass, and superfluid helium can pass said mass without moving vortices occurring during the flow.
  • a vortex tube is to be understood to mean within the scope of the present invention, a duct having dimensions such that, in the prevailing operating conditions, moving vortices occur in the superfluid when liquid helium flows through said duct.
  • a differential pressure occurs across the series arrangement of superleak, cold store and vortex tube.
  • the overall differential pressure will occur across the vortex tube, because no temperature difference prevails across the superleak yet, and consequently no differential pressure either. Due to this differential pres-v sure across the vortex tube, medium therein will start flowing to the second place, the superfluid helium exceeding its critical velocity, and vortices occurring, as a result of which normal helium is also transported to the second place.
  • At least one of the said throttle devices is arranged between the said first and the said second place. This means that the differential pressure which prevails across the relative throttle device also prevails across the series arrangement of superleak, cold space and vortex tube.
  • the throttle device is constructed as a throttle ejector, the outlet side of which communicates on the one side, via the said counter-current heat exchangers, with the suction side of the compression device, said outlet side communicating on the other hand, via a throttle valve, with a cold space the vapor space of which communicates with the suction side of the ejector.
  • the suction pressure of the ejector will prevail in the cold space, so that the cold is supplied at a temperature which is lower than the temperature at the outlet side of said ejector.
  • Such a device operates excellently for temperatures lying above that of the lt-point of helium, but when the temperature at the outlet side of the ejector or in the cold space falls considerably below that of the lt-point of helium, the fact presents .itself that in the duct communicating the cold space with the ejector, pressure gradients occur which cause thermal flows from the outlet side of the ejector to the cold space, which is just not the intention in a refrigerator, and
  • a further embodiment of the device ac cording to the invention provides a solution to the said problem and is characterized in that at least one of the said throttle devices is formed by a throttle ejector, the
  • one of the throttle devices is also formed by a throttle ejector
  • the outlet of said ejector communicates, beside with the heatexchanging space, also via a further throttle valve and a further heat exchanger in which the helium exchanges heat with the heat'exchanging store, with the one side.
  • the cold produced in the cold space may be used for cooling articles. In such cases it is frequently not possible, for all kinds of structural reasons, to contact said articles directly with said space, so that the cold has to be supplied at some distance from the space.
  • a further embodiment is characterized in that at least oneduct communicates with the cold space and with its other side can be brought in thermal contact with the place to be cooled, if desirable via a further space, said duct comprising a sintered superleak which extends throughout the length of the duct and covers a part of the cross-section thereof. In this manner it is possible in a very efficient manner to supply the produced cold at a distance from the cold store.
  • FIGS. 1, 2, 3 and 4 diagrammatically show not to scale four different embodiments of devices for producing cold at temperatures lower than that of the A-point ofhelium. I a
  • FIG. 1 denotes a'compression device the outlet side 2 of which, for compressed helium, communicates with a system of supply ducts 3, in which a water cooler 4 for removing the heat of compression, a number of counter-current heat exchangers 5, and two pre-coolers 6 and 7' are arranged.
  • the system of supply ducts 3 communicates with the inlet 8 of an ejector 9.
  • the outlet side of said ejector communicates at 10 on the one hand with the system of outlet ducts 11 in which the counter-current heat exchangers 5 are also incorporated, and on the other hand with a duct 12which communicates, via a counter-current heat exchanger 13 having a low resistance to flow, on the one hand with a throttle valve 14 and on the other hand with a throttle valve 15.
  • Throttle valve 14 opens into a heat-exchanging space 16 which communicates with the suction side 17 of the ejector 9.
  • the throttle valve 15 communicates with a heat exchanger 18 which is in thermal contact with the space 16 and in turn communicates with a superleak 19 which communicates with its other side with a cold space 20. This cold space communicates, through a vortex tube 21, with the heat exchanging space 16.
  • this device compresses helium to a pressure of approximately 30 atm. which compressed helium leaves the compression device via the outlet 2 and delivers its heat of compression to' cooling water in the heat exchanger 4.
  • the compressed helium then flows through the first counter-current heat exchanger 5 and then along the precooler 6, then through the second heat exchanger 5, and then along the second pre-cooler 7, and then through the last counter-current heat exchanger Sin which the high-pressure helium will then have a temperature which lies below the inversion'temperature associated with the pressure of 30 atm.
  • The'high-pressure helium'then expands in the ejector 9 to a pressure of, for example, I atm. and a temperature of 4.2K.
  • a part of the expanded helium flows via the outlet duct 11 to the inlet side 22 of the compression device 1.
  • Another part of the expanded helium flows via duct 12 and heat exchanger 13 to the throttle valves .14 and 15. Since the heat-exchanging space 16 communicates with the suction side 17 of the ejector 9, a low pressure of approximately 12 mm Hg will adjust in the space 16, with which a temperature of [.8 "K is associated, so a temperature lower than that of the itpoint of helium. This means that the helium in the heatexchanger 18 will also assume this low temperature.
  • the cold produced in the space can be used for cooling articles, for example, electric components, infrared cells superconductive resonant cavities, and so on. These articles may be, for example, in direct contact with the space 20. However, for all kinds of structural reasons a certain distance will usually exist between the space 20 and the article to be cooled, certainly when cooling of several articles which are arranged at a distance from each other have to be cooled with one space 20. This cooling at a distance can very efflciently be carried out by communicating a duct 23 at its one side with the space 20 and bringing its other side in thermal contact with an article 27 to be cooled. So helium at a temperature below that of the )t-point of helium will also be present in the duct 23.
  • this helium at the said temperatures has an extremely good thermally conductive power which may be up to l,000 times higher than that of solid substances.
  • This property can be explained by the fact that at said temperatures the helium consists partly of normal fluid, with viscosity and entropy, and partly of superfluid which shows no viscosity and entropy.
  • the superfluid will flow to the place with the higher temperature without transporting thermal energy, while normal fluid flows in the opposite direction in such manner that the overall mass flow is zero. With this normal fluid thermal energy is transported indeed. It has been found that the mutual friction between normal and superfluid by moving vortices in the superfluid adversely influences the thermal conductivity of Hell.
  • this disadvantageous effect has been counteracted by covering the inner wall of the duct 23 with a superleak 24 of, for example, aluminum oxide particles of silicon carbide particles of very small dimensions which are sintered together.
  • a superleak has the property that normal fluid cannot pass it while superfluid flows through it without moving vortices occurring.
  • thermal energy is supplied to the end 28 of the duct 23 by the article to be cooled, said end 28 will assume a slightly higher temperature than that prevailing in the space 20.
  • a differential pressure corresponds to this temperature difference across the duct 23, so that normal and superfluid flows through the core of the duct 23 to the space 15, while an equally large mass flow of superfluid flows through the superleak 24 to the article 27 to be cooled.
  • the superleak 24 it is not necessary for the superleak 24 to be arranged against the inner wall, although this does provide the advantage that heat leak from without is counteracted; however, it is alternatively readily possible to arrange the superleak 24 detached from the wall of the tube, for example, as a core in the duct.
  • the duct 23 may communicate with its end 28 with a further space which serves either as a cold buffer for the article to be cooled, or as a space from which liquid can be drained.
  • FIG. 2 shows a device which in general is equal to the device shown in FIG. 1, but in which the superleak l9 communicates with the place 30 of the system of supply ducts, via the heat exchanger 18 and throttle valve 15 a further heat exchanger 13.
  • FIG. 3 It is shown in FIG. 3 how the heat-exchanging store 16 can have the form of a real heat-exchanger. For the rest, this device is quite similar to that shown in FIG. 2.
  • FIG. 4 shows a device for producing cold at very low temperatures which in general also corresponds to the device which is shown in the preceding Figures, but in which the high-pressure helium is first expanded in the throttle valve 31 to, for example, a pressure of 5 atmosphere, after which this expanded helium is further expanded in a second throttle valve 32 to, for example, a pressure of 17 mm Hg, which pressure therefore also prevails in the heat exchanging space 33.
  • the inlet side of the superleak l9 communicates with a place 34 which, viewed in the direction of flow, is situated in front of this throttle valve 32, while the vortex tube 21 communicates with the store 33,
  • a throttle valve 15 is again provided and a heat exchanger 18 in which a temperature prevails which lies below that of the )t-point of helium, while the pressure there is higher than in the space 33, so that again superfluid helium will start flowing through the superleak 19 without moving vortices occurring and from the store 20 helium will flow through the vortex tube 21, in which the superfluid helium exceeds its critical velocity, to the space 33 and then through the system of outlet ducts 11 to the inlet side of the compression device 1.
  • the production of cold in the space 20 will occur at a temperature which is lower than that in the space 33, in which the compression device 1 needs sucking only at a pressure which corresponds to the pressure in the space 33.
  • the invention provides an extremely simple extension of a Joule-Kelvin system with which it is possible, without the introduction of moving components and without the presence of an extremely bulky compression device, to produce cold at temperatures in the proximity of lK and lower.
  • Devices or the type to which the present invention relates are therefore suitable for use as precoolers for He-l-le mixture refrigerators, with which it is possible to produce cold continuously at temperatures in the proximity of 20 millidegrees K.
  • a device for producing cold at temperatures lower than that of the )t-point of helium which device in cludes a source for high-pressure helium with a low pressure suction inlet, and a high pressure outlet which communicates with a supply duct system including at least one pre-cooler and at least one counter-current heat exchanger in which the high-pressure helium is cooled to below its inversion temperature associated with the said pressure, the counter-current heat exchanger communicating with at least one throttle device in which the high-pressure helium expands to a second lower pressure, the expanded helium then flowing, via an outlet duct system and said counter-current heat exchanger to said suction side of said source, characterized in that the device furthermore comprises a further heat exchanger, a cold space, a throttle valve, a vortex tube, and at least one superleak which communicates on its one side via said further heat exchanger in which the helium cools to below the x-temperature of helium and said throttle valve with said outlet duct system,
  • a cryogenic refrigerator apparatus for producing cold at a temperature lower than the )t-point of helium, comprising a source of He gas with a first high pressure and a first high temperature, a supply duct means for transporting He from said source, first meansfor cooling He in said supply duct means to a second tempera-.
  • second means for expanding the cooled He from said first means to a second lower pressure
  • further duct means for dividing said expanded He from said second means into first and second portions
  • third means for further expanding and cooling said second portion of He to a third temperature below the )t-point thereof and for forming at least some of said second portion He into superfluid He and the remainder of said second portion into normal liquid He
  • a cold space container a superleak communicating between said third means and said cold space container, a vortex tube communicating between said cold space container and said third means, whereby the superleak permits passage of only superfluid He from said third means to said cold space container, and a turbulent flow of normal and superfluid He occurs in the vortex tube from said container to said third means.
  • said first means for cooling He comprises heat exchangers
  • said second means comprises an ejector
  • said third means comprises a Joule-Thompson throttle expander and further heat exchanger
  • said vortex tube has an aperture with a cross-section corresponding to the pressure differential across said aperture such that the flow of normal He therethrough is turbulent.
  • said second means comprises a throttle-device for expanding said He.
  • Apparatus according to claim 6 further comprising a second container for containing liquid He formed by said third means, and means for applying low pressure suction on said second container from said second means.
  • said second means is an ejector including an inlet, an outlet, and a suction side
  • the apparatus further comprising a heat exchange container having space for liquid and vapor He from said third means,,return duct means communicating said vapor to the suction side of said ejector, said return duct means being a counter-flow portion of a heat exchanger for cooling said second portion of said He before it is expanded by said third means.
  • Apparatus according to claim 11 furthercomprising final heat exchange means being cooled by said liquid He in said heat exchange container, the apparatus further comprising fourth means for further expanding He from said ejector and communicating this expanded He to said final heat exchanger with the superfluid He thereformed communicated to said superleak.
  • Apparatus according to claim 11 further comprising final heat exchange means being cooled by said liquid He in said, heat exchange container, the apparatus further comprising fourth means for further expanding some of the He from said first means, and communicating this expanded He to said final heat exchanger with the superfluid He thereformed communicated to said super-leak.
  • Refrigeration apparatus comprising a source of He at a first high pressure and an inlet for receiving He at a second lower pressure, supply duct means for transporting said high pressure He from said source,
  • return duct means for transporting He to said source inlet, first means for cooling He in said supply duct means to below the inversion temperature associated with said first pressure, second means for expanding and further cooling He from said supply duct means and dividing same into first and second portions, third means for further expanding said first portion and for further cooling same to below the )t-point thereof to form a mixture of normal and superfluid He, a cold space container, a superleak which permits passage of only superfluid He from said third means to said cold space container, a vortex tube through which flows both normal and superfluid He from said container to said second means, and means for communicating said second portion of expanded He to said return duct means.

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US00885542A 1968-06-05 1969-12-16 DEVICE FOR PRODUCING COLD AT TEMPERATURE LOWER THAN THAT OF lambda -POINT OF HELIUM Expired - Lifetime US3713305A (en)

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NL6807903A NL6807903A (enrdf_load_stackoverflow) 1968-06-05 1968-06-05
US88554269A 1969-12-16 1969-12-16

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3835662A (en) * 1972-03-18 1974-09-17 Philips Corp Device for transporting heat from a lower to a higher temperature level
JPS5072235A (enrdf_load_stackoverflow) * 1973-08-10 1975-06-14
US3896630A (en) * 1972-03-17 1975-07-29 Philips Corp Method for starting a {hu 3{b He-{hu 4{b He dilution refrigerator
JPS50120038A (enrdf_load_stackoverflow) * 1974-03-01 1975-09-19
US4499737A (en) * 1982-03-23 1985-02-19 International Business Machines Corporation Method and dilution refrigerator for cooling at temperatures below 1° K.
US4779017A (en) * 1987-10-13 1988-10-18 The United States Of America As Represented By The Secretary Of The Air Force Superconducting rotor cooling system

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3360955A (en) * 1965-08-23 1968-01-02 Carroll E. Witter Helium fluid refrigerator
US3427817A (en) * 1964-12-19 1969-02-18 Philips Corp Device for producing cold and/or liquefying gases
US3447339A (en) * 1966-05-25 1969-06-03 Philips Corp Cold producing systems
US3464230A (en) * 1966-07-01 1969-09-02 Philips Corp Systems for producing cold and ejectors in such systems

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3427817A (en) * 1964-12-19 1969-02-18 Philips Corp Device for producing cold and/or liquefying gases
US3360955A (en) * 1965-08-23 1968-01-02 Carroll E. Witter Helium fluid refrigerator
US3447339A (en) * 1966-05-25 1969-06-03 Philips Corp Cold producing systems
US3464230A (en) * 1966-07-01 1969-09-02 Philips Corp Systems for producing cold and ejectors in such systems

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3896630A (en) * 1972-03-17 1975-07-29 Philips Corp Method for starting a {hu 3{b He-{hu 4{b He dilution refrigerator
US3835662A (en) * 1972-03-18 1974-09-17 Philips Corp Device for transporting heat from a lower to a higher temperature level
JPS5072235A (enrdf_load_stackoverflow) * 1973-08-10 1975-06-14
JPS50120038A (enrdf_load_stackoverflow) * 1974-03-01 1975-09-19
US3978682A (en) * 1974-03-01 1976-09-07 U.S. Philips Corporation Refrigeration method and apparatus by converting 4 He to A superfluid
US4499737A (en) * 1982-03-23 1985-02-19 International Business Machines Corporation Method and dilution refrigerator for cooling at temperatures below 1° K.
US4779017A (en) * 1987-10-13 1988-10-18 The United States Of America As Represented By The Secretary Of The Air Force Superconducting rotor cooling system

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