JP4956233B2 - Cold storage type refrigerator and cold storage type freezing method - Google Patents

Description

The present invention relates to a cold storage refrigerator and a cold storage refrigeration method for generating cold by cold storage refrigeration.

  In a regenerative refrigerator, temperature oscillation caused by the refrigerant compression / expansion cycle occurs. In particular, in the case of a refrigerator using a magnetic regenerator material that can be cooled to a 4K level cryogenic temperature used for cooling a superconducting magnet or the like, the specific heat of the member is smaller than that of the refrigerant, so that the amplitude of temperature oscillation increases. Since the average value of the temperature vibration is used as the cooling temperature for the refrigerator, the cooling temperature during expansion of the refrigerant (the minimum value of the temperature in the temperature vibration) cannot be utilized effectively.

Moreover, since it is necessary to keep the cooling temperature constant depending on the object to be cooled, it is necessary to suppress the temperature oscillation caused by the refrigeration cycle by some method. As an apparatus for suppressing temperature oscillation due to the refrigeration cycle, for example, there is an apparatus disclosed in Patent Document 1. In the apparatus disclosed in Patent Document 1, a He pot containing helium is attached to the lower part of the cooling stage provided at the lower end of the cool storage unit of the cool storage type refrigerator, and the cooling stage and the object to be cooled are connected via the He pot. Perform heat exchange. The helium in the He pot is liquefied at the time of helium expansion in the temperature oscillation, that is, at a low temperature, thereby absorbing the temperature fluctuation amplitude and suppressing the temperature oscillation of the object to be cooled.
Japanese Patent Laid-Open No. 07-146020

  The conventional cold storage type refrigerator described above absorbs the amplitude on the low temperature side in the temperature vibration, and thus the cooling temperature at the time of expansion of the refrigerant at which the temperature is minimized cannot be utilized. In other words, if it is possible to thermally separate from the object to be cooled when the temperature rises during compression, the cooling temperature during refrigerant expansion can be utilized.

Accordingly, an object of the present invention is to provide a regenerative refrigerating machine and a regenerative refrigerating method capable of suppressing temperature oscillation and further lowering the cooling temperature as compared with the prior art.

In order to achieve the above object, a cold storage refrigerator according to the present invention includes a vacuum vessel, a displacer driving unit, a cold storage unit, a cold head that generates cold by a cold storage refrigeration cycle, and the vacuum vessel disposed in the vacuum vessel A first cooling stage cooled by the cold generated in the cold head, a condenser connected to the lower part of the first cooling stage, and a second cooling arranged to be connected to the lower part of the condenser. A refrigerant condensing part composed of a material having a high thermal conductivity and connected to a lower part of the first cooling stage so as to exchange heat with the first cooling stage. A cylinder connected to the lower part of the refrigerant condensing part and made of a material having low thermal conductivity and having both upper and lower ends open, and a refrigerant evaporating part connected to the lower end of the cylinder, the cylinder, the refrigerant condensing part, the refrigerant And the refrigerant is sealed in the airtight chamber formed by the origination unit, wherein the tube is composed of a material having low thermal conductivity than the refrigerant condensing section and the refrigerant evaporating section, the pressure of the refrigerant sealed in the airtight chamber is selected on the pressure falls within the amplitude range of the temperature oscillations the boiling point of the refrigerant due to the compression-expansion cycle of the refrigerant in the first cooling stage generated by said cold head and said Rukoto.

The cold storage refrigeration method according to the present invention includes a vacuum vessel, a displacer driving unit, a cold storage unit, a cold head that generates cold by a cold storage refrigeration cycle, and a cold head disposed in the vacuum vessel. The first cooling stage cooled by the generated cold, and the refrigerant condensing composed of a material having a high thermal conductivity that is connected to the lower part of the first cooling stage so as to exchange heat with the first cooling stage. Part, a cylinder connected to the lower part of the refrigerant condensing part and made of a material having low thermal conductivity and having both upper and lower ends open, a refrigerant evaporating part connected to the lower end of the cylinder, the cylinder, the refrigerant condensing part, a condenser in which the refrigerant is sealed in the airtight chamber formed by the refrigerant evaporating section, and a second cooling stage which is arranged to be connected to the lower portion of the condenser, the barrel refrigerant condensing part Contact Than fine refrigerant evaporating portion is composed of low thermal conductivity material, the pressure of the refrigerant sealed in the airtight chamber, compression-expansion cycle of the refrigerant in the first cooling stage having a boiling point of the refrigerant is generated by said cold head a cold storage refrigeration method using a cold accumulation refrigerator that will be selected to a pressure comprised within the amplitude range of the temperature oscillations caused by the of the condenser to generate cold by cold storage refrigeration cycle of the cold head Cooling the refrigerant condensing part, dropping the refrigerant liquefied by heat exchange with the refrigerant condensing part in the airtight chamber to the refrigerant evaporating part, and liquefying the refrigerant via the refrigerant evaporating part and the second cooling stage The heat exchange is performed.

  According to the regenerative refrigerator of the present invention, it is possible to suppress the temperature oscillation caused by the compression / expansion cycle of the refrigerant and to lower the cooling temperature of the object to be cooled than before.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a cross-sectional view schematically showing a regenerator type refrigerator according to the present embodiment.

  A cold head 2 connected to a compressor 8 is provided in the vacuum vessel 1. The cold head 2 includes a displacer driving unit 3, a first cold storage unit 4, and a second cold storage unit 5, and is a refrigerator that generates cold by cold storage refrigeration. Examples of the refrigerator used in the cold head 2 include a refrigerator (GM refrigerator) using a Gifford McMahon cycle, a pulse tube refrigerator, a Stirling refrigerator, and the like. In this embodiment, the following description will be made assuming that a GM refrigerator is used. The first cool storage unit 4 and the second cool storage unit 5 are disposed inside the vacuum container 1, and a first cooling stage 6 is provided below the second cool storage unit 5.

A condenser 15 including a refrigerant condensing unit 11, a cylinder 12, and a refrigerant evaporating unit 13 is disposed below the first cooling stage 6. The refrigerant condensing unit 11 and the refrigerant evaporating unit 13 are made of a material having high thermal conductivity such as copper, and the cylinder 12 is made of a material having a lower thermal conductivity than the refrigerant condensing unit 11 and the refrigerant evaporating unit 13 such as thin stainless steel. ing. The refrigerant condensing unit 11, the cylinder 12, and the refrigerant evaporating unit 13 form an airtight chamber 14, and a refrigerant such as helium is enclosed in the airtight chamber 14. The pressure of the refrigerant is such that the boiling point of the refrigerant is included in the range of temperature oscillation caused by the refrigerant compression / expansion cycle of the cooling stage 6 generated by the cold head 2.

  A second cooling stage 7 is disposed below the condenser 15, and an object to be cooled (not shown) is connected to the second cooling stage 7.

  Hereinafter, the operation of the regenerative refrigerator according to this embodiment will be described.

  The cold head 2 generates cold using a regenerative refrigeration cycle and cools the first cooling stage 6. The first cooling stage 6 exchanges heat with the second cooling stage 7 via the condenser 15.

  Hereinafter, the heat exchange mechanism between the first cooling stage 6 and the second cooling stage 7 through the condenser 15 will be described.

When the first cooling stage 6 has a temperature lower than the boiling point of the refrigerant during temperature oscillation caused by the refrigerant compression / expansion cycle , the refrigerant is liquefied by heat exchange with the first cooling stage 6 via the refrigerant condensing unit 11. Then, it falls into the refrigerant evaporating section 13 through the cylinder 12. The dropped liquefied refrigerant cools the second cooling stage 7 via the refrigerant evaporating section 13 and evaporates.

  On the other hand, when the first cooling stage 6 has a temperature higher than the boiling point of the refrigerant during temperature oscillation, the refrigerant is not liquefied by heat exchange with the first cooling stage 6 via the refrigerant condensing unit 11. Therefore, the heat intrusion into the first cooling stage 6 and the second cooling stage 7 is via the gas phase of the refrigerant sealed in the hermetic chamber 14 and the cylinder 12, and the first cooling stage 6 to the second cooling stage 7. The amount of heat penetration into the water becomes very small.

  That is, the cooled object 7 cooled by the second cooling stage 7 is in a state of being thermally separated from the temperature of the refrigerant condensing unit 11.

  Therefore, the temperature amplitude of the second cooling stage 7 is in the range below the boiling point of the refrigerant in the hermetic chamber 14 in the temperature amplitude of the first cooling stage 6. As a result, the temperature oscillation of the object to be cooled can be suppressed and the cooling temperature can be lowered as compared with the conventional case.

  In the present embodiment, the cold head 2 is described as a refrigerator having a two-stage cold storage unit, but the cold head 2 has a number of cold storage unit stages applied to a refrigerator having one or more stages. Even so, the effect of the present embodiment can be obtained similarly.

  According to the present embodiment, it is possible to suppress the temperature oscillation caused by the compression / expansion cycle in the regenerative refrigerator, and to lower the cooling temperature of the object to be cooled than before.

  2, 3, and 4 are cross-sectional views each showing an outline of a condenser 15 of a regenerative refrigerator according to a different embodiment of the present invention.

  The condenser 15 shown in FIG. 2 (a) has a non-through hole 21 on the bottom surface of the refrigerant condensing part 11, and the condenser 15 shown in FIG. 2 (b) has a non-through hole 21 on the top face of the refrigerant evaporation part 13. ing.

  The condenser 15 shown in FIG. 3A is provided with fins 22 on the bottom surface of the refrigerant condensing part 11, and the condenser 15 shown in FIG. 3B is provided with fins 22 on the upper surface of the refrigerant evaporation part 13.

  The condenser 15 shown in FIG. 4 (a) has a porous member 23 below the refrigerant condensing part 11, and in the condenser 15 shown in FIG. 4 (b), the porous member 23 is above the refrigerant evaporating part 13. Is provided.

  These condensers 15 come into contact with the refrigerant in the hermetic chamber 14 by providing contact area increasing means such as the non-through holes 21, the fins 22, or the porous member 23 in the refrigerant condensing unit 11 and / or the refrigerant evaporating unit 12. It has a structure that can increase the area to be heated and promote heat exchange. You may make it provide the non-through-hole 21, the fin 22, or the porous member 23 in both the refrigerant | coolant condensing part 11 and the refrigerant | coolant evaporation part 13. FIG. Further, the structure of the contact area increasing means provided in each of the refrigerant condensing unit 11 and the refrigerant evaporating unit 13 is different from each other, such as providing the non-through hole 21 in the refrigerant condensing unit 11 and the porous member 23 in the refrigerant evaporating unit 13. May be.

Further, regarding the non-through hole 21 provided in the condensing part 11 of the condenser 15 shown in FIG. 2A, the non-through hole 21 has a cylindrical shape, the diameter of this cylindrical shape is d, the gravitational acceleration is g, the refrigerant Ρg is the density in the gas state at that temperature, ρl is the density of the refrigerant in the liquid state at that temperature, and σ is the surface tension of the refrigerant, and the Laplace constant L is L = [σ / {(ρ _l −ρ _g ) · g}] ^0.5
When the diameter d of the cylindrical non-through hole 21 is
L <d <3L
If the temperature of the refrigerant condensing part 11 becomes higher than the boiling point of the refrigerant due to temperature vibration after the inside of the non-through hole 21 is filled with the liquefied refrigerant, the second cold storage in which the temperature rise is first transmitted. Vaporizing from the closed end side of the non-through hole 21 and increasing in volume results in a driving force that pushes the liquefied refrigerant filled in the non-through hole 21 toward the open end side, and promotes the drop of the liquid droplets. be able to.

  The Laplace constant L is the diameter of the bubbles that are detached from the heat transfer surface due to the heat load in the liquid, and is formulated by the above formula for various gases.

  When the diameter d of the non-through hole 21 is d <L, there is no refrigerant liquid between the refrigerant bubble and the inner wall of the non-through hole 21 in the non-through hole 21, and resistance due to the surface tension of the refrigerant Is generated, and the driving force of the refrigerant liquid in the non-through hole 21 is rapidly reduced.

  Further, when 3L <d, the ratio of the amount of liquid driven by the driving force of the bubbles to the amount of liquid of the refrigerant becomes small, and the driving force of the liquid rapidly decreases.

  Next, FIG. 5 shows a cross-sectional view schematically illustrating a condenser 15 according to another embodiment of the present invention. The condenser 15 of FIG. 5 is provided with a non-through hole 21 that satisfies L <d <3L in the refrigerant condensing part 11, and the refrigerant condensing part 11 has a thermal conductivity from an intermediate part to the open end side of the non-through hole 21. A heat insulating member 24 that is a low-cost member is disposed. By disposing the heat insulating member 24 on the open end side of the non-through hole 21, the vaporization of the refrigerant in the non-through hole 21 can be caused only on the closed end side of the non-through hole 21. Thereby, the fall of the refrigerant liquefied in the non-through hole 21 can be further promoted.

  FIG. 6 is a cross-sectional view schematically showing a regenerative refrigerator according to still another embodiment of the present invention. In the present embodiment, the first cooling stage 6A in which the first cooling stage and the refrigerant condensing unit are integrated, and the second cooling stage and the refrigerant evaporation unit are integrated into a second cooling stage 7A. . In addition, the same code | symbol is attached | subjected to the structure same as Example 1, and the overlapping description is abbreviate | omitted.

  By adopting such an integrated structure, it is not necessary to connect the first cooling stage and the condenser 15 using an adhesive or the like, so heat exchange between the cold head 2 and the object to be cooled via the condenser 15 is possible. Promoted.

  Only one of the first cooling stage 6A and the second cooling stage 7A may have an integrated structure.

  According to the present embodiment, the cold head 2 via the condenser 15 is formed by integrating each of the first cooling stage and the refrigerant condensing unit and / or the second cooling stage and the refrigerant evaporating unit. Heat exchange of the object to be cooled can be promoted.

  FIG. 7 is a cross-sectional view schematically showing a regenerative refrigerator of still another embodiment according to the present invention. In the regenerative refrigerator according to the present embodiment, a buffer 32 and a pressure gauge 33 installed outside the vacuum vessel 1 communicate with the hermetic chamber 14 via a pipe 31. The pipe 31 is provided with a valve 34. In addition, the same code | symbol is attached | subjected to the structure same as Example 1, and the overlapping description is abbreviate | omitted.

  The buffer 32 is a container having a sufficiently large volume, and has a function of controlling the pressure of the refrigerant in the hermetic chamber 14 when the valve 34 is opened. The pressure gauge 33 measures the refrigerant pressure in the hermetic chamber 14. Therefore, the refrigerant pressure can be freely controlled by the buffer 32 and the pressure gauge 33.

  Hereinafter, the operation of the regenerative refrigerator according to this embodiment will be described.

  The refrigerant in the hermetic chamber 14 has a temperature range in which heat exchange between the first cooling stage 6 and the second cooling stage 7 is performed. The refrigerant in the hermetic chamber 14 starts from the lowest temperature during the temperature oscillation of the first cooling stage by the cold head 2. Up to the boiling point of. Therefore, the boiling point of the refrigerant can be controlled by controlling the refrigerant pressure in the hermetic chamber 14, and the temperature of the second cooling stage 7 can be adjusted.

  Further, by setting the indicated value of the pressure gauge 33 to a saturation temperature corresponding to the vapor pressure of the refrigerant, it can be used as a vapor pressure thermometer of the second cooling stage 7.

  Furthermore, it is possible to make the heat insulation between the first cooling stage 6 and the second cooling stage 7 more reliable by evacuating the hermetic chamber 14 with the buffer 32. Thereby, when the temperature of the cold head 2 is raised for the purpose of maintenance or the like, the cold head 2 and the object to be cooled can be thermally separated to prevent the temperature of the object to be cooled from rising.

  Moreover, sectional drawing which shows the outline of the cool storage type refrigerator by other Example of this invention is shown in FIG. In the present embodiment, instead of the buffer 32, a bellows buffer 35 which is a variable volume container is provided. The buffer 32 needs to be electrically controlled in order to control the pressure of the refrigerant. However, the bellows-shaped buffer 35 can control the pressure of the refrigerant by changing the volume, and thus electric control becomes unnecessary.

  As mentioned above, although several Example was described about this invention, this invention is not limited to the said Example, For example, the cool storage type | formula of the structure which combined the characteristics demonstrated in the said Example 1 thru | or 4 arbitrarily It can be a refrigerator.

Sectional drawing which shows the outline of the cool storage type refrigerator by Example 1. FIG. Sectional drawing which shows the outline of the condenser by Example 2. FIG. Sectional drawing which shows the outline of the condenser by Example 2. FIG. Sectional drawing which shows the outline of the condenser by Example 2. FIG. Sectional drawing which shows the outline of the condenser by the modification of Example 2. FIG. Sectional drawing which shows the outline of the condenser by Example 3. FIG. Sectional drawing which shows the outline of the condenser by Example 4. FIG. Sectional drawing which shows the outline of the condenser by the modification of Example 4. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vacuum vessel 2 Cold head 3 Displacer drive part 4 1st cool storage part 5 2nd cool storage part 6, 6A 1st cooling stage 7, 7A 2nd cooling stage 8 Compressor 11 Refrigerant condensing part 12 Tube 13 Refrigerant evaporation part 14 Airtight chamber 15 Condenser 21 Non-through hole 22 Fin 23 Porous member 24 Heat insulation member 31 Pipe 32 Buffer 33 Pressure gauge 34 Valve 35 Bellows buffer

Claims (10)

A vacuum vessel;
A cold head having a displacer drive unit, a cold storage unit, and generating cold by a cold storage refrigeration cycle;
A first cooling stage disposed in the vacuum vessel and cooled by the cold generated in the cold head;
A condenser connected to the lower part of the first cooling stage;
A second cooling stage connected to the lower part of the condenser,
The condenser is connected to the lower part of the first cooling stage, and is connected to the lower part of the refrigerant condensing part. The refrigerant condensing part is connected to the lower part of the first cooling stage so as to exchange heat with the first cooling stage. A cylinder made of a material having low thermal conductivity and open at both upper and lower ends, and a refrigerant evaporation section connected to the lower end of the cylinder, and is formed by the cylinder, the refrigerant condensing section, and the refrigerant evaporation section. Refrigerant is sealed in a closed room,
The cylinder is made of a material having a lower thermal conductivity than the refrigerant condensing part and the refrigerant evaporating part,
The pressure of the refrigerant sealed in the hermetic chamber is selected such that the boiling point of the refrigerant falls within the amplitude range of the temperature oscillation caused by the refrigerant compression / expansion cycle of the first cooling stage generated by the cold head. This is a regenerative refrigerator. 2. The regenerative refrigerator according to claim 1, wherein at least one of a non-through hole, a fin, and a porous member is provided on a surface of the refrigerant condensing unit that contacts the refrigerant. The refrigerant condensing part is provided with a non-through hole having a cylindrical shape on a surface in contact with the refrigerant,
The diameter d of this non-through hole is
Gravity acceleration is g, density of the refrigerant in the gas state is ρg, density of the refrigerant in the liquid state is ρl, and surface tension of the refrigerant is σ, and a Laplace constant L is L = [σ / {(ρl−ρg ) · G}] ^0.5
When
L <d <3L
The regenerative refrigerator according to claim 1, wherein the regenerator is in a range satisfying the above. The regenerative refrigerator according to claim 3, wherein a heat insulating member having a through hole communicating with the non-through hole and the airtight chamber is provided on a lower surface of the refrigerant condensing unit. The said refrigerant | coolant evaporation part is provided with at least any one of a non-through-hole, a fin, and a porous member in the surface which contacts the said refrigerant | coolant, The Claim 1 thru | or 4 characterized by the above-mentioned. The regenerative refrigerator according to item 1. 2. The first cooling stage and the refrigerant condensing part have an integrated structure.
The regenerative refrigerator according to any one of claims 5 to 5. The said 2nd cooling stage and the said refrigerant | coolant evaporation part were made into the integral structure.
The regenerative refrigerator according to any one of claims 6 to 6. The regenerative refrigerator according to any one of claims 1 to 7, further comprising refrigerant pressure control means for controlling the pressure of the refrigerant in the hermetic chamber. The regenerative refrigerator according to claim 8, wherein the refrigerant pressure control means is a bellows-type variable volume container. A vacuum vessel;
It has a displacer drive unit and a cold storage unit, and generates cold by a cold storage type refrigeration cycle.
Cold head,
A first cooling unit disposed in the vacuum vessel and cooled by the cooling generated in the cold head.
Rejection stage,
Connected to the lower part of the first cooling stage so as to exchange heat with the first cooling stage.
A refrigerant condensing part made of a material with high thermal conductivity, connected to the lower part of this refrigerant condensing part and conducting heat
A cylinder made of a low-rate material with both upper and lower ends open, and a refrigerant evaporation section connected to the lower end of this cylinder
The refrigerant is sealed in an airtight chamber formed by the cylinder, the refrigerant condensing part, and the refrigerant evaporating part.
A condenser, and
A second cooling stage arranged connected to the lower part of the condenser,
The cylinder is made of a material having a lower thermal conductivity than the refrigerant condensing part and the refrigerant evaporating part,
The pressure of the refrigerant sealed in the hermetic chamber is such that the boiling point of the refrigerant is generated by the cold head.
Within the amplitude range of the temperature oscillation caused by the refrigerant compression / expansion cycle of the first cooling stage
A regenerative refrigeration method using a regenerative refrigerator selected for the pressure,
The cold is generated by the cold storage refrigerating cycle of the cold head, and the cooling of the condenser is performed.
The refrigerant cooled by the medium condensing part and liquefied by heat exchange with the refrigerant condensing part in the airtight chamber
Is dropped into the refrigerant evaporating section, and the refrigerant liquefied through the refrigerant evaporating section and the second cooling
A regenerative refrigerating method characterized in that the stage is subjected to heat exchange.

Images