JP4679457B2 - Subcool cryogenic device - Google Patents

Description

  The present invention relates to a subcool low-temperature apparatus that cools a refrigerant liquid that cools equipment using a superconductor to a subcooled state.

  In power devices such as current limiters, cables, power storage devices, transformers, and motors using high-temperature superconductors, liquid nitrogen, which is a refrigerant, is in a subcooled state (cooled below the saturation temperature at that pressure). This leads to improvement of the characteristics and insulation characteristics of the wire material, and has a merit (Patent Document 1). At that time, it is necessary to cool the liquid nitrogen with an external cooling device. For example, an invention using a single-stage regenerative refrigerator that can be cooled below the temperature of liquid nitrogen is disclosed (Patent Document 2).

As shown in FIG. 10, the conventional low-temperature apparatus has the cooling head 4 connected to the lower side from the cooling stage 1a at the bottom of the refrigerator 1, so that it is lowest when there is a heat load for cooling the refrigerant liquid 10. The part that becomes the temperature is the upper part of the cooling head 4. On the other hand, the refrigerant liquid 10 becomes a low-density liquid, that is, a liquid having a higher temperature toward the upper side in the vertical direction, and is in a direction opposite to the temperature gradient of the cooling head 4. Therefore, as shown in FIG. 11, a large temperature difference is generated between the cooling head 4 and the refrigerant liquid 10 near the liquid surface, and the temperature difference between the refrigerant liquid 10 and the cooling head 4 is reduced below the cooling head 4. Since the heat flux in the cooling head 4 is proportional to the temperature difference, the refrigerant liquid 10 cannot be cooled over the entire cooling head 4 and is intensively cooled in a portion near the cooling stage 1a. That is, the lower part of the cooling head 4 does not contribute much to cooling.
Japanese Patent Laid-Open No. 10-325661 JP 2001-289546 A

  The characteristics required for the subcool low temperature apparatus include cooling efficiency, liquid surface stability, and simplicity. Regarding the cooling efficiency, it is required to have the ability to cool the refrigerant liquid by fully utilizing the performance of the refrigerator. In general, the refrigeration efficiency of the refrigerator decreases as the cooling stage becomes lower in temperature. Therefore, if the temperature difference generated in the heat transfer member connecting the refrigerator and the refrigerant liquid is large, the cooling efficiency of the apparatus decreases.

  Regarding the stability of the liquid level, there are the following problems. In a container filled only with a refrigerant liquid having no gas phase, since there is no liquid level, a subcooled state with a constant temperature can be stably obtained by cooling and pressurizing the entire refrigerant liquid. However, a liquid surface exists in a container having a gas phase, and when the gas and the refrigerant liquid have the same composition, the liquid surface temperature becomes the saturation temperature at that pressure. For example, in the case of nitrogen, the temperature when the inside of the container is maintained at atmospheric pressure is 77K. When the inside of the refrigerant liquid is cooled by an external cooling device, a temperature difference occurs between the inside of the refrigerant liquid and the liquid level, and a layer having a temperature gradient can be formed near the liquid level. Under gravity, the lower the temperature, the higher the density of the liquid, so the low-temperature refrigerant liquid falls downward, and the high-temperature refrigerant liquid rises near the liquid surface and stabilizes. Therefore, if the refrigerant liquid is disturbed (for example, when the temperature is increased by applying a heat load, or when it is shaken dynamically), the stable temperature gradient layer is disturbed, and the subcooling below the saturation temperature occurs on the liquid surface. A refrigerant liquid layer appears. Therefore, gas condensation occurs at the liquid level, and the pressure in the container decreases.

Concerning convenience, with regard to the installation of the refrigerator, a configuration in which the refrigerator is directly attached to a container having a wide opening, a configuration in which a part of the sealed container is cooled, and a refrigerator is provided outside the container to provide a circulation pump, There is a configuration in which the refrigerant liquid is transferred to the container by pressure or the like. The first configuration is simple in mounting the refrigerator and the configuration of the container, and it is easy to provide the apparatus to be cooled in the container. However, the liquid level becomes wide, and there are problems of the influence of disturbance of the temperature gradient layer and the amount of heat penetration from the opening. On the other hand, the latter two configurations make it possible to concentrate the space having the liquid level in one place where the disturbance is unlikely to occur, for example, in a separate container for pressure adjustment. . However, the apparatus becomes complicated, and the attachment of the object to be cooled becomes relatively complicated.
Therefore, an object of the present invention is to provide a subcool low temperature apparatus that can easily achieve and stably maintain a subcooled state of the refrigerant liquid with a simple configuration.

In order to solve the above problems, a subcool cryogenic apparatus of the present invention includes a cryogenic container for storing a refrigerant liquid, a refrigerator equipped with a cooling stage attached to the cryogenic container and penetrating into the cryogenic container, A cooling head attached to the lower end of the cooling stage below the liquid level and connected in a direction in which the outer surface extends upward is provided with a cooling head having a temperature gradient in the same direction as the temperature gradient of the refrigerant liquid.

In addition, the subcool low temperature apparatus of the present invention includes a refrigerant holding container that stores a refrigerant liquid, a heat insulating vacuum container that surrounds the refrigerant holding container, and a cooling stage that is attached to the heat insulating vacuum container and penetrates into the heat insulating vacuum container. and refrigerator, e Bei pipes and which is cooled by the refrigerant storage container and the heat insulating vacuum vessel and the cooling stage connected to said refrigerant holding vessel flowed through the refrigerant liquid in the space between the said of the pipe A configuration in which a valve that is closed to disconnect the refrigerant holding container and the piping involved in cooling when the refrigerator is stopped is provided between the part connected to the refrigerant holding container and the part connected to the cooling stage . And

  Furthermore, the subcool low-temperature apparatus of the present invention includes a low-temperature container that stores a refrigerant liquid, a heat-insulating container in which a cooling stage of a refrigerator is inserted, and a heat-exchanging container that is connected to a heat exchange unit attached to the cooling stage. A refrigerant pipe that circulates a refrigerant having a boiling point lower than that of the refrigerant liquid between the low-temperature containers and a heat exchange unit that is connected to the refrigerant pipe and cools the refrigerant liquid in the low-temperature container. .

  ADVANTAGE OF THE INVENTION According to this invention, the subcool low temperature apparatus which can achieve the subcooled state of a refrigerant | coolant liquid easily and can be maintained stably with simple structure can be provided.

DESCRIPTION OF EMBODIMENTS Hereinafter, first to third embodiments of a subcool low temperature apparatus according to the present invention will be described with reference to the drawings.
(First embodiment)
The subcool low temperature apparatus of the 1st Example of the 1st Embodiment of this invention is shown in FIG. That is, the refrigerator 1 for reducing or eliminating the evaporation of the refrigerant liquid 10 is attached to the low temperature container 2 including the heat insulating vacuum container 3a and the refrigerant holding container 3b. The refrigerator 1 is usually attached from the upper part of the cryogenic container 2 in consideration of maintainability and the like, and the refrigerant liquid 10 is cooled by the cooling head 4a attached to the cooling stage 1a provided on the lower side. The cooling head 4a has a shape of a container or a cage having an open top, and the bottom is attached to the lower end of the cooling stage 1a. That is, the cooling head 4a is attached to the lower end of the cooling stage 1a, and is attached in a direction in which the outer surface extends upward.

  According to this configuration, as shown in FIG. 2, the direction of the temperature gradient of the cooling head 4a coincides with the direction of the temperature gradient near the liquid surface of the refrigerant liquid 10, and the cooling head 4a and the refrigerant liquid 10 at each position are aligned. Therefore, the entire cooling head 4a contributes to the cooling of the refrigerant liquid 10, and uniform and efficient heat transfer characteristics can be obtained. Thus, the cooling efficiency including the heat transfer characteristics to the refrigerant liquid 10 can be improved, and further, the temperature gradient near the liquid surface of the refrigerant liquid 10 can be stabilized, and the disturbance of the refrigerant liquid 10 due to fluctuations in the heat load. It is possible to prevent an abnormal pressure (abrupt decrease, increase, etc.) in the cryogenic container 2 due to.

  FIG. 3 shows a second example of the subcool low temperature apparatus of the present embodiment. In the present embodiment, the cooling head 4b is connected to the outside of the refrigerant holding container 3b, and the refrigerator 1 does not directly cool the refrigerant liquid 10, but the container 3b holding the refrigerant liquid 10. Cooling from the side. In this configuration, since the refrigerator 1 is not provided above the cryogenic container 2, there is an advantage that a space for cooling the cooled device 20 is increased. Also in this embodiment, by attaching the lower part of the cooling head 4b attached to the side surface of the refrigerant holding container 3b to the cooling stage 1a, the temperature gradient of the cooling head 4b and the temperature gradient of the refrigerant liquid 10 are in the same direction. The same effect as the embodiment can be obtained.

  In addition, a present Example is good also as a structure which attached the refrigerator 1 to the side surface of the heat insulation vacuum vessel 3a. If it does in this way, maintenance of the refrigerator 1 etc. can be performed safely also in a subcool low temperature apparatus which a high voltage applies to the upper surface of cryogenic container 2, and it is dangerous to access the upper surface.

  FIG. 4 shows a third example of the present embodiment. In this embodiment, a cooling head 4c having fins 5 immersed in the refrigerant liquid 10 is attached to the tip of the cooling stage 1a. According to the present embodiment, the layer having the temperature gradient of the refrigerant liquid 10 is stable against internal disturbance, and instability of the pressure in the cryogenic container 2 due to the disturbance in the refrigerant liquid 10 can be suppressed.

  FIG. 5 shows a fourth example of the present embodiment. In this embodiment, a padding 6 which is a liquid level adjusting device is added to the first embodiment (FIG. 1). The height of the padding 6 can be changed from the outside of the cryogenic container 2 by the handle 7. In the first and third embodiments, when the refrigerant liquid 10 is cooled from a certain temperature to a lower temperature, the volume decreases due to the temperature dependence of the density of the refrigerant liquid 10, so the liquid level decreases. . Therefore, the relative positional relationship between the cooling heads 4a and 4c and the liquid level also shifts. Therefore, the position where the refrigerant liquid 10 can be effectively cooled cannot be maintained. In this embodiment, the liquid level can be controlled up and down by the padding 6 that can move up and down from the outside, and effective cooling can be performed. Usually, since the temperature gradient layer near the liquid surface is not a place where the cooled device 20 is installed, this does not reduce the installation space of the cooled device 20.

  In the present embodiment, a member such as sapphire corresponding to a high voltage is used as a member of the cooling heads 4a and 4c that directly cools the refrigerant liquid 10, or the electric field concentration is reduced in the shape of the surface. It is good to have a configuration with the above treatment.

(Second Embodiment)
FIG. 6 shows a second embodiment of the present invention. The subcool low temperature apparatus of the present embodiment has a configuration in which a pipe 8 with valves 9a and 9b is connected to the refrigerant holding container 3b, and a cooling head 4d is connected to the pipe 8. Cooling of the refrigerant liquid 10 by the refrigerator 1 is performed in a part of the pipe 8 branched from the refrigerant holding container 3b and returning to the original state. Since the refrigerant liquid 10 cooled in a part of the pipe 8 has a high density, it drops downward and returns to the original container 3b (natural convection), so that the refrigerant liquid 10 can be cooled.

  The merit of the present embodiment can be obtained particularly by providing the pipes 8 with valves 9a and 9b. That is, as shown in FIG. 6, by providing valves 9a and 9b at two locations on the pipe 8, the refrigerant holding container 3b and the pipe 8 involved in cooling can be separated. When the two valves 9a and 9b are closed and the refrigerant liquid in the pipe 8 side (the refrigerator 1 side) is removed by some method, the refrigerator 1 and the refrigerant holding container 3b are thermally separated. In particular, when the pipe 8 is made of a material having a low thermal conductivity such as stainless steel, the heat insulating property is increased. If the refrigerator 1 is stopped after the separation, it is possible to raise the temperature of the cooling stage 1a of the refrigerator 1 to room temperature without applying a large heat load to the refrigerant liquid 10, and the maintenance of the refrigerator 1 can be performed in a short time. It can be carried out. In the case of such a configuration, the refrigerator 1 cannot be maintained unless all the refrigerant liquid 10 in the refrigerant holding container 3b is removed and the temperature is raised, so that the time required for the maintenance increases and the object to be cooled is cooled. Since the temperature of the device 20 also rises, for example, the superconducting coil or the like cannot be energized, and the operation of the device must be stopped.

  Moreover, in this Embodiment, since the installation direction of the refrigerator 1 can be attached from the side surface side of the cryogenic container 2, for example, it is dangerous to access the upper surface in a configuration in which a high voltage is applied to the upper surface of the cryogenic container 2. Even in the apparatus, since the refrigerator 1 can be installed at a position away from a dangerous place, the maintainability is good.

(Third embodiment)
FIG. 7 shows a first example of the third embodiment of the present invention. In this embodiment, the refrigerator 1 is installed in a heat-insulated vacuum container 15 different from the low-temperature container 2 that houses the device to be cooled 20, and the space between them is reciprocally connected by a heat-insulating pipe 14. A refrigerant pipe 11 is provided in the heat insulation pipe 14, and a refrigerant having a boiling point lower than that of the refrigerant liquid 10 in the refrigerant holding container 3b is sealed in the refrigerant pipe 11 as a gas or a supercritical state. A heat exchanging portion 13 with the cooling head 4 is provided on the refrigerant pipe 11 on the refrigerator 1 side, and a heat exchanging portion 13a is constituted by a pipe immersed in the refrigerant liquid 10 on the refrigerant holding container 3b side. In addition, a low-temperature circulation pump 12 that promotes the circulation of the refrigerant is installed in a part of the refrigerant pipe 11. According to the present embodiment, the refrigerator 1 can be placed at a position away from the cryogenic container 2, and a subcool low temperature apparatus excellent in maintainability can be provided.

  FIG. 8 shows a second example of the third embodiment of the present invention. In the present embodiment, the refrigerant pipe 11 is wound around the outside of the refrigerant holding container 3b that stores the refrigerant liquid 10 to constitute the heat exchange unit 13b. As a winding method, the refrigerant pipe 11 having the lowest temperature from the refrigerator 1 is wound from the lower side of the refrigerant holding container 3b, and the refrigerant pipe 11 that rises in temperature while cooling the refrigerant liquid 10 is sequentially directed upward in the refrigerant holding container 3b. It is set as the structure wound around. If it does in this way, the temperature gradient of the refrigerant | coolant piping 11 in the refrigerant | coolant holding | maintenance container 3b side surface and the temperature gradient of the refrigerant | coolant liquid 10 correspond, the refrigerant | coolant liquid 10 can be cooled efficiently and stability can be improved.

  FIG. 9 shows a third example of the third embodiment of the present invention. In this embodiment, the circulation pump 17 on the refrigerant pipe 11 is provided in the room temperature portion, and the counterflow heat exchanger 16 is provided between the room temperature pipe and the low temperature pipe. In this embodiment, the maintainability of the apparatus is improved by placing the circulating pump 17 requiring maintenance in the room temperature portion.

Sectional drawing which shows the structure of the subcool low-temperature apparatus of the 1st Example of the 1st Embodiment of this invention. The graph explaining the cooling effect | action of the subcool low-temperature apparatus of the 1st Example of the 1st Embodiment of this invention. Sectional drawing which shows the structure of the subcool low-temperature apparatus of the 2nd Example of the 1st Embodiment of this invention. Sectional drawing which shows the structure of the subcool low-temperature apparatus of the 3rd Example of the 1st Embodiment of this invention. Sectional drawing which shows the structure of the subcool low-temperature apparatus of the 4th Example of the 1st Embodiment of this invention. Sectional drawing which shows the structure of the subcool low-temperature apparatus of the 2nd Embodiment of this invention. Sectional drawing which shows the structure of the subcool low-temperature apparatus of the 1st Example of the 3rd Embodiment of this invention. Sectional drawing which shows the structure of the subcool low-temperature apparatus of the 2nd Example of the 3rd Embodiment of this invention. Sectional drawing which shows the structure of the subcool low-temperature apparatus of the 3rd Example of the 3rd Embodiment of this invention. Sectional drawing which shows the conventional subcool low temperature apparatus. The graph explaining the cooling effect | action of the conventional subcool low temperature apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Refrigerator, 1a ... Cooling stage, 2 ... Low-temperature container, 3a ... Adiabatic vacuum container, 3b ... Refrigerant holding container, 4, 4a, 4b, 4c, 4d ... Cooling head, 5 ... Fin, 6 ... Filler, 7 DESCRIPTION OF SYMBOLS ... Handle, 8 ... Pipe, 9a, 9b ... Valve, 10 ... Refrigerant liquid, 11 ... Refrigerant pipe, 12 ... Low-temperature circulation pump, 13, 13a, 13b ... Heat exchange part, 14 ... Insulated pipe, 15 ... Insulated vacuum vessel, 16 ... Counterflow heat exchanger, 17 ... Room temperature circulation pump, 20 ... Cooled equipment.

Claims (10)

A cryogenic container for storing the refrigerant liquid, a refrigerator having a cooling stage attached to the cryogenic container and penetrating into the cryogenic container, and an outer surface attached to the lower end of the cooling stage below the liquid level of the refrigerant liquid. A subcooling low-temperature apparatus comprising: a cooling head connected in a direction extending upward and having a temperature gradient in the same direction as a temperature gradient of the refrigerant liquid.   The subcooling low-temperature apparatus according to claim 1, wherein the cooling head has a shape of a container or a car having an opening, and a bottom of the container or the car is attached to the cooling stage.   The subcooling low-temperature apparatus according to claim 1, wherein the cooling head includes a fin that promotes heat transfer.   2. The subcool low temperature apparatus according to claim 1, further comprising a liquid level height adjusting unit that is immersed in the refrigerant liquid and moves in a vertical direction to adjust a liquid level of the refrigerant liquid. A refrigerant holding container for storing a refrigerant liquid; a heat insulating vacuum container surrounding the refrigerant holding container; a refrigerator provided with a cooling stage attached to the heat insulating vacuum container and penetrating into the heat insulating vacuum container; the refrigerant holding container; Bei example a pipe and which is cooled by the connected to the refrigerant storage container the cooling stage flowed through the refrigerant liquid in the space between the heat insulating vacuum vessel,
A valve that is closed between the portion of the pipe connected to the refrigerant holding container and the portion connected to the cooling stage to close the refrigerant holding vessel and the pipe involved in cooling is provided when the refrigerator is stopped. A subcool cryogenic device characterized by that.   The subcool low temperature apparatus according to claim 5, wherein the refrigerator is attached to a side surface of the heat insulating vacuum vessel.   The refrigerant liquid is connected between the low temperature container for storing the refrigerant liquid, the heat insulating container in which the cooling stage of the refrigerator is inserted, and the heat exchange unit attached to the cooling stage, and between the heat insulating container and the low temperature container. A subcooling low-temperature apparatus comprising: a refrigerant pipe that circulates a refrigerant having a low boiling point; and a heat exchange section that is connected to the refrigerant pipe and cools the refrigerant liquid in the low-temperature container. The subcool low temperature apparatus according to claim 7, wherein a heat exchanging portion for cooling the refrigerant liquid is immersed in the refrigerant liquid. The subcool low temperature apparatus according to claim 7 , wherein the heat exchanging section for cooling the refrigerant liquid is coupled to a refrigerant holding container for storing the refrigerant liquid in the low temperature container. The subcool low temperature apparatus according to claim 7, further comprising a refrigerant circulation pump on the refrigerant pipe.

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