JP2019086159A - Circulative cooling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new circulation cooling device having significantly improved maintainability while exhibiting excellent cooling capacity. SOLUTION: An upstream side of an outward line 72 of a circuit 70 for circulating a cryogen is communicated with a top surface 20a of an inner container 20, and a downstream side thereof is communicated with a bottom surface 20b of the inner container 20. As a result, the cryogen flows into the inner container 20 and comes into direct contact with the refrigerator 30, so that it can be cooled efficiently. Further, since the heat exchanger for cooling the cryogen is not required, the work of disassembling the vacuum container 10 and removing the heat exchanger is not required at the time of maintenance, and the maintainability is greatly improved. [Selection diagram] Fig. 1

Description

  The present invention relates to a circulation cooling device for cooling a body to be cooled such as a high sensitivity magnetic sensor to a cryogenic temperature while circulating a cryogen such as liquid helium.

  Superconducting quantum interference device (SQUID) is one of the ultrasensitive magnetic sensors that utilizes the quantization of magnetic flux in superconductivity, and is for low field nuclear magnetic resonance imaging (Low Field MRI) In addition to magnetic sensors, it is an indispensable device for advanced measurement systems in the fields of various analysis, inspection, environment and resource exploration. And since this superconducting quantum interference device utilizes the superconductivity phenomenon which occurs under cryogenic temperature, the cooling device which used cryogens, such as helium, is indispensable.

  As one of the cooling devices of this type, there is, for example, a circulating cooling device as disclosed in Non-Patent Document 1 below. FIG. 4 shows the structure of this circulation type cooling device, in which a first heat exchanger N1 and a second heat exchanger N2 are accommodated in a vacuum vessel Y provided with a small refrigerator K. A cooling unit R is provided at the tip of a vacuum heat insulation pipe H extending from the vacuum vessel Y, and the cooling unit R is configured to accommodate a body to be cooled S (superconducting quantum interference device).

  Then, helium, which is a cryogen, is sequentially sent to the first heat exchanger N1 and the second heat exchanger N2 in the vacuum vessel Y by the circulation pump P, where the cryogen is exchanged by heat exchange with the small refrigerator K, for example, 4K. After cooling to a certain extent, the object to be cooled S (superconducting quantum interference device) is cooled to a cryogenic temperature that exhibits its function by sending it to a remote cooling unit R via a vacuum adiabatic pipe H. After that, the cryogen whose temperature has risen by cooling is again sent to the second heat exchanger N2 and the first heat exchanger N1 in the vacuum vessel Y in order via the vacuum adiabatic pipe H again, and helium sent in order here After precooling, the circulation pump P is again circulated.

A. P. Rijpma, 6 others, Construction and test of a cryocooled low-Tc SQUID gradiometer system, CRYOGENICS, Vol. 48, 2008, p. 61-67 (ELSEVIER)

  By the way, the conventional cooling device as described above requires a heat exchanger having a complicated structure, and (the heat transfer tube of) the heat exchanger is in close contact (brazing) with the cooling stage of the small refrigerator K It is provided as. Therefore, when maintaining the small refrigerator K or the like, the vacuum container Y has to be disassembled once and the heat exchangers N have to be removed one by one, and the operation is extremely troublesome.

  Therefore, the present invention has been devised to solve these problems, and it is an object of the present invention to provide a novel circulating cooling device which exhibits excellent cooling capacity while greatly improving maintainability. is there.

  According to a first aspect of the present invention, there is provided a vacuum vessel, an inner vessel accommodated in the vacuum vessel, a refrigerator having a cooling stage accommodated in the inner vessel, and a cooling device for cooling a body to be cooled. A vacuum adiabatic pipe for communicating the inside of the vacuum vessel with the cooling part, and a circulation circuit passing the inside of the vacuum insulation pipe and circulating and supplying the cryogen to the cooling part; The upstream side is in communication with the top surface of the inner vessel, and the downstream side of the forward line is in communication with the bottom of the inner vessel, and the return line of the refrigerant circulation circuit is arranged to pass through the vacuum vessel. It is a circulating cooling device characterized by

  According to such a configuration, since the cryogen flowing in the forward line of the cryogen circulation circuit flows into the inner container and directly contacts the cooling stage of the refrigerator provided therein, the cryogen can be efficiently cooled it can. Therefore, since it becomes unnecessary to use a heat exchanger for cooling the refrigerant flowing in the forward line at this cooling stage as in the prior art, when maintaining the refrigerator etc., the vacuum vessel is disassembled or the heat exchanger is Maintenance work is greatly improved because the removal work is unnecessary. In addition, by arranging the return line of the cryogen circulation circuit to pass through the inside of the vacuum vessel, it is possible to suppress external heat input to the cryogen flowing through the return line and to utilize the cold heat for precooling in the vacuum vessel. .

  A second aspect of the invention is the circulation cooling device according to the first aspect, wherein a plurality of heat transfer fins are provided on the surface of either or both of the regenerator and the cooling stage of the refrigerator. According to such a configuration, the contact area between the cooling stage of the refrigerator and the refrigerant increases, so that the refrigerant can be cooled more efficiently.

  A third invention according to the first or second invention, wherein a heat exchanger is accommodated in the inner container, and a return line of the circulation circuit is connected to the heat exchanger. It is. According to such a configuration, heat exchange can be performed by the cryogen that cools the object to be cooled in the cooling unit and returns to the return line and the cryogen that is newly supplied into the inner container sequentially, so that the cryogen returns to the return line The cold heat of the can efficiently precool the newly supplied cryogen.

  According to a fourth invention, in the circulation system according to the third invention, the heat exchanger has a serpentine structure in which either or both of a regenerator and a cooling stage of the refrigerator are spirally surrounded. It is a cooling device. According to such a configuration, it is not necessary to provide a dedicated mounting space in the inner container 20, and the contact area with the cryogen can be increased, and heat exchange can be performed efficiently. In addition, since the cooling stage of the refrigerator does not contact or interfere with the heat exchanger, the refrigerator can be easily detached at the time of maintenance by moving the refrigerator upward.

  According to the present invention, the inner container is provided in the vacuum container, and the cryogen flowing in the forward line is allowed to flow into the inner container and is brought into direct contact and cooled by the cooling stage of the refrigerator provided therein. Therefore, the cryogen can be cooled efficiently. Therefore, since it becomes unnecessary to use a heat exchanger for cooling the refrigerant flowing in the forward line at this cooling stage as in the prior art, when maintaining the refrigerator etc., the vacuum vessel is disassembled or the heat exchanger is Maintenance work is greatly improved because the removal work is unnecessary.

BRIEF DESCRIPTION OF THE DRAWINGS It is a whole block diagram which shows one Embodiment of the circulation cooling device 100 which concerns on this invention. It is a perspective view which shows the A section in FIG. It is a whole block diagram which shows other embodiment of the circulation cooling device 100 which concerns on this invention. It is an explanatory view showing the composition of the conventional circulation cooling device.

  Hereinafter, embodiments of the present invention will be described with reference to the attached drawings. FIG. 1 shows an embodiment of a circulation cooling device 100 according to the present invention. As shown, the circulation cooling device 100 cools the vacuum vessel 10, the inner vessel 20 accommodated in the vacuum vessel 10, the refrigerator 30 mounted in the inner vessel 20, and the object to be cooled 40. A cooling unit 50, a vacuum insulation pipe 60 communicating the cooling unit 50 with the inside of the vacuum vessel 10, a cryogen circulation circuit 70 for circulating the cryogen through the inner vessel 20 and circulating it to the cooling unit 50; And a heat exchanger 80 provided at the

  The vacuum vessel 10 is, for example, a vertical cylindrical vessel having a height of 50 to 100 cm and a diameter of about 20 to 30 cm, and is put in a high vacuum state of, for example, about 0.1 to 0.0001 Pa by a vacuum pump P1. It is kept. The material is not particularly limited. For example, in addition to stainless steel, lightweight glass fiber reinforced plastic (GFRP) or the like is used. On the other hand, the inner container 20 has a substantially cylindrical shape having a size smaller by one size than the vacuum container 10, and the bottom surface 20b is positioned to float slightly higher than the bottom surface 10b of the vacuum container 10. In contrast, the top surface 20 a is integral with or common to the top surface 10 a of the vacuum vessel 10.

  The refrigerator 30 is, for example, a small refrigerator called a small refrigerator or a pulse tube employing a two-stage Ghodo McMahon (GM) cycle or a low vibration small refrigerator called a pulse tube, and a refrigerator head attached to the top surface 20 a of the vacuum vessel 10 A cylindrical first regenerator 32a extending downward from 31 (inside the inner container 20), a first cooling stage 32b located at the lower end of the first regenerator 32a, and further from the first cooling stage 32b It is mainly comprised from the cylindrical 2nd regenerator 33a extended vertically downward, and the 2nd cooling stage 33b located in the lower end of this 2nd regenerator 33a.

  A mounting flange 36 is provided on the lower surface of the refrigerator head 31, and a seal (not shown) is formed on the mounting hole 20c formed in the top surface 20a of the vacuum vessel 10 with a bolt (not shown) or the like. It is attached in a sealed state and is insertable and removable. A compressor 34 is connected to the refrigerator head 31 via a plurality of gas pipes 31a, and the compressor 34 compresses and circulates a refrigerant for the refrigerator to form a refrigeration cycle. In addition, the refrigerator currently marketed has a freezing capacity of about 1 W at helium temperature.

  Further, as shown in FIG. 2, all or part of the first regenerator 32a, the first cooling stage 32b, the second regenerator 33a, and the second cooling stage 33b of the refrigerator 30 located in the inner container 20. In this case, a plurality of flange-shaped heat transfer fins 35 are provided in upper and lower stages, and the function of increasing the surface area of these is exhibited. Furthermore, as shown in the same figure, a heat exchanger 80 consisting of a pipe body 80a of a spiral tube structure extending in a spiral shape around the heat transfer fins 35 is arranged to surround them at a constant interval. Provided in The inside diameter of the heat exchanger 80 is wider than at least the maximum diameter (outside diameter) of any one of the heat transfer fins 35. In addition, the heat exchanger 80 is particularly located in the upper part of the first regenerator 32a and the first cooling stage 32b, and further in the second regenerator 33a.

  Returning to FIG. 1, the cooling unit 50 is a heat exchanger in which a heat transfer tube forming a part of the cryogen circulation circuit 70 is processed into a spiral or serpentine shape, and is arranged in the vicinity of or around the object to be cooled 40 positioned. The object to be cooled 40 housed in the cooling unit 50 is, for example, a superconducting magnetic sensor such as a SQUID (superconducting quantum interference device) operating in a cryogenic temperature state, and it is possible to It can be measured. Moreover, as another example of this to-be-cooled body 40, in order to make use of the temperature characteristic of a physical-property value, it is a sample holder which maintains a measurement object at a required low temperature.

  The inside of the vacuum heat insulation pipe 60 communicating with the cooling unit 50 and the inside of the vacuum vessel 10 is a vacuum tube, and the length is the distance between the position where the cooling unit 50 is attached and the installation position of the vacuum vessel 10 However, for example, the length is about 50 cm to several meters. In addition to stainless steel as well as the vacuum vessel 10, lightweight glass fiber reinforced plastic (GFRP) or the like is used as the material.

  The cryogen circulation circuit 70 is for circulating and supplying cryogen to the cooling unit 50, and a circulation pump 71 attached to the outside of the vacuum vessel 10, and a pair of metals connecting the circulation pump 71 and the cooling unit 50. It mainly comprises an outward line 72 and a return line 73 made of pipes and a cryogen tank 74 for supplying a cryogen. Further, the forward line 72 includes an upstream forward line 72 a extending from the circulation pump 71 and a downstream forward line 72 b connected to the cooling unit 50. The other end (downstream end) of the upstream forward pass line 72 a is connected to the top surface 20 a side so as to communicate with the inside of the inner vessel 20, and the other end (upstream end) of the downstream forward pass line 72 b is connected to the inner vessel 20. It is connected to the bottom surface 20b side so as to communicate with the inside.

  On the other hand, the return line 73 is also composed of an upstream return line 73a extending from the cooling unit 50 and a downstream return line 73b connected to the circulation pump 71 side, and the other end (downstream end) of the upstream return line 73a is an inner container 20 is connected to the inlet (lower end) side of the heat exchanger 80 provided inside, and the other end (upstream end) of the downstream return line 73b is connected to the outlet (upper end) side of the heat exchanger 80 respectively Structure. Further, the return line 73 is provided with a cryogen tank 74 for supplying helium gas as a cryogen, and helium gas circulating in the forward line 72 and the return line 73 is supplied.

  Next, the operation of the circulation cooling device 100 according to the present invention having such a configuration will be described. First, the vacuum pump P1 is operated to evacuate the vacuum vessel 10, and when the refrigerator 30 is driven to sufficiently cool the inner vessel 20, the circulation pump 71 of the refrigerant circulation circuit 70 is operated. Then, a normal temperature cryogen (helium gas) is supplied from the upstream outward line 72a of the outward line 72 into the inner container 20 from the top surface 20a side. Then, the temperature of the cryogen flowing into the inner container 20 is in direct contact with the surfaces of the first regenerator 32a, the first cooling stage 32b, the second regenerator 33a, and the second cooling stage 33b of the refrigerator 30 in that order. Drops sharply.

  For example, the cryogen flowing into the inner container 20 at normal temperature (about 20 ° C.) passes around the first regenerator 32a when it flows downward sequentially in the inner upper layer portion of the inner container 20, and is cooled to about 100 K, It is cooled to about 40-80 K in contact with the first cooling stage 32 b, and further cooled to about 4-10 K by the second regenerator 33 a and the second cooling stage 33 b to reach the bottom surface 20 b of the inner container 20.

  The cryogen reaching the bottom surface 20b of the inner container 20 flows out to the downstream outward line 72b connected to the bottom surface 20b of the inner container 20 by the pressure of the cryogen sequentially fed from the top surface 20a side, and the vacuum insulation pipe 60 It passes through and is sent to the cooling unit 50 to cool the object to be cooled 40 to about 5 to 12K. Thereafter, the refrigerant in the cooling unit 50 passes through the upstream return line 73a of the return line 73, reaches the inside of the inner container 20, and flows into the heat exchanger 80 thereof.

  Then, when the refrigerant (about 20 to 30 K) flowing into the heat exchanger 80 flows upward through the spiral pipe body 80a as shown in FIG. 2, the high temperature refrigerant flowing into the inner container 20 sequentially After heat exchange (pre-cooling) and the temperature rises to room temperature, it passes through the downstream return line 73b and circulates the forward line 72 and the return line 73 again by the circulation pump 71.

  As described above, in the circulating cooling device 100 of the present invention, the inner container 20 is provided in the vacuum container 10, and the cryogen flows from the outgoing line 72 into the inner container 20 to cool the refrigerator 30 provided therein. Since direct cooling is performed by the stages 32b and 33b and the regenerators 32a and 33a, the refrigerant can be efficiently cooled. Further, since the heat exchanger 80 is provided in the return line 73, it is possible to effectively use for precooling of the high temperature cryogen sequentially supplied without wasting the cold energy of the returned cryogen.

  Moreover, since this heat exchanger 80 has a spiral flexible tube structure so as to surround the cooling stages 32b and 33b, there is no need to provide a dedicated mounting space in the inner container 20, and the contact area with the cryogen is large. Heat exchange can be performed efficiently. Furthermore, since a plurality of heat transfer fins 35 are provided on the surface of the refrigerator 30, ie, the surfaces of the first regenerator 32a, the first cooling stage 32b, the second regenerator 33a, the second cooling stage 33b, etc. Since the contact area with the cryogen is increased, the cryogen can be cooled more efficiently.

  And since the circulating cooling device 100 of this invention which comprised in this way becomes that the heat exchanger for cooling the cryogen which flows the outbound line 72 with a refrigerator 30 like the prior art becomes unnecessary, When performing maintenance, the operation of disassembling the vacuum vessel 10 or removing the heat exchanger is unnecessary, and the maintainability is greatly improved. Further, since the inside diameter of the spiral heat exchanger 80 provided in the return line 73 is wider than at least the maximum diameter (outside diameter) of any one of the heat transfer fins 35, By moving the cooling stages 32b and 33b so as to be pulled upward, they can be easily desorbed to the refrigerator 30 at the time of maintenance, and they do not interfere with the work.

  As shown in FIG. 1, the inner container 20 is in the shape of a vertical cylinder, and there is a large temperature difference near 300 ° C. between the vicinity of the top surface 20a and the vicinity of the bottom surface 20b. Therefore, a step 20d is provided in the vicinity of the bottom surface 20b at a position about 5 to 10 cm higher than this, and the upstream return line 73a is introduced into the inner container 20 from the step 20d. If it does not come into contact with it, it does not adversely affect the cryogenic coolant discharged from its bottom surface 20b, and it returns the return line 73 effectively, and the cold energy of the coolant which is newly supplied is returned relatively cold. It can be used as pre-cooling heat.

  Further, in the present embodiment, the spiral heat exchanger 80 is provided in the inner container 20, but as shown in FIG. 3, the heat exchanger 90 is provided outside the vacuum container 10 (on the top surface 20a). If the refrigerant just before being supplied into the inner container 20 is precooled by the cold heat of the refrigerant immediately after leaving the vacuum container 10 without passing through the inside of the inner container 20, the refrigerator The structure around the 30 cooling stages 32b and 33b can be simplified to further improve maintainability. Further, in the present embodiment, although an example in which the cooling stage is a two-stage type as the refrigerator 30 is shown, the temperature required for the object to be cooled 40 may be a relatively high temperature, for example, 20 K or more Alternatively, a single-stage compact refrigerator without the first stage 32b shown in FIG. 1 or 3 may be used.

DESCRIPTION OF SYMBOLS 100 ... Circulating cooling device 10 ... Vacuum container 20 ... Inner container 20a ... Top surface 20b ... Bottom surface 30 ... Refrigerator 32a ... 1st regenerator 32b ... 1st cooling stage 33a ... 2nd regenerator 33b ... 2nd Cooling stage 35: Heat transfer fin 40: Object to be cooled 50: Cooling part 60: Vacuum insulation pipe 70: Cryogen circulation circuit 71: Circulating pump 72: Outgoing line 72a: Upward outgoing line 72b: Downstream outgoing line 73: Returning line 73a ... Upstream return line 73b ... Downstream return line 80, 90 ... Heat exchanger 80a: Pipe body

Claims (4)

A vacuum vessel, an inner vessel accommodated in the vacuum vessel, a refrigerator having a cooling stage accommodated in the inner vessel, a cooling unit for cooling an object to be cooled, communication between the cooling unit and the vacuum vessel And a cryogen circulation circuit which circulates the cryogen through the vacuum insulation pipe to the cooling unit.
The upstream side of the forward line of the cryogen circulation circuit is in communication with the top surface of the inner vessel, and the downstream side of the forward line is in communication with the bottom of the inner vessel,
The circulation cooling device is characterized in that a return line of the cryogen circulation circuit is disposed to pass through the inside of the vacuum vessel. In the circulating cooling device according to claim 1,
A plurality of heat transfer fins are provided on the surface of either or both of a regenerator and a cooling stage of the refrigerator. In the circulating cooling device according to claim 1 or 2,
A heat exchanger is accommodated in the inner container, and a return line of the refrigerant circulation circuit is connected to the heat exchanger. In the circulating cooling device according to claim 3,
The circulating cooling device, wherein the heat exchanger has a serpentine structure in which either or both of a regenerator and a cooling stage of the refrigerator are spirally surrounded.

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