JP2021086975A - Superconducting apparatus - Google Patents

Abstract

To suppress a decrease in the cooling effect by making it possible to reliably suppress film boiling by low-cost means.SOLUTION: A superconducting apparatus according to an embodiment includes a heat transfer surface cooled by a liquid refrigerant, and a coating layer that is provided to cover at least a part of the heat transfer surface and has a lower thermal conductivity than the heat transfer surface, the heat transfer surface has a plurality of heat transfer regions and a plurality of heat transfer suppression regions alternately arranged with the plurality of heat transfer regions, and (a) the coating layer is provided so as to selectively cover the heat transfer suppression region of the heat transfer surface, or (b) the thickness of the coating layer in each of the heat transfer suppression regions is larger than that of each of the heat transfer regions.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to superconducting equipment.

In recent years, in low-temperature fields such as space engineering, medicine, and superconducting technology, cooling technology that promotes boiling cooling using a low-temperature liquid refrigerant is required. The boiling state of the liquid refrigerant shifts from nucleate boiling to transition boiling and then to film boiling as the temperature difference between the liquid refrigerant and the target object to be cooled increases, as generally represented by a boiling curve. In nucleate boiling, convection is promoted when fine bubbles separate from the surface of the object to be cooled, so that the amount of heat transfer is the largest. When a body to be cooled placed in an extremely low temperature liquid refrigerant such as liquid nitrogen is boiled and cooled, the surface of the body to be cooled is likely to fall into a boiling state in which the surface of the body to be cooled is covered with a vapor film because the temperature difference is large. In the boiling state of the film, heat is transferred through the steam layer formed between the liquid refrigerant and the surface of the object to be cooled. However, since the thermal conductivity of the steam layer is extremely poor, heat from the object to be cooled to the liquid refrigerant is generated. Transmission is extremely reduced and cooling efficiency is reduced.

Therefore, conventionally, research results have been reported in which the surface of the object to be cooled is covered with a substance having a low thermal conductivity such as PTFE to lower the surface temperature and stay in nucleate boiling to prevent film boiling. .. However, with this method, it is inevitable that the heat transfer in the non-boiling region will deteriorate. It has also been reported that heat transfer is improved by covering the surface of the copper sphere with frost having a low thermal conductivity and maintaining the nucleate boiling state. In this case, it can be expected that heat transfer in the non-boiling region will be improved by increasing the surface area due to the presence of fine icicles in the frost layer, but industrial implementation is a future task.

According to Patent Document 1, in a current limiting device that performs a current limiting operation using a superconductor, the boiling state of the cooling medium is changed from the nucleate boiling state to the film boiling by providing fins having high thermal conductivity on the surface of the superconducting member. Means for suppressing the transition to the state have been proposed. As a reason why the film boiling can be suppressed, the paragraph [0055] of Patent Document 1 states, "Since a sufficient number of fins are formed in the test heating element 3, the surface shape thereof is complicated, and the steam film. It is considered that this is because the film is not completely boiled as a result of the formation of the film. "

Japanese Patent No. 5800018

In the means disclosed in Patent Document 1, it is necessary to provide a heat radiating member such as a fin on the heat transfer surface to be cooled to complicate the shape of the heat transfer surface, so that the manufacturing cost increases and the heat radiating member is provided. Space is needed. Further, it is unclear whether the desired cooling effect can be obtained depending on the shape of the heat radiating member in spite of the increase in manufacturing cost.

The present disclosure has been made in view of the above-mentioned problems, and an object of the present disclosure is to suppress a decrease in the cooling effect by reliably suppressing film boiling by a low-cost means.

In order to achieve the above object, the superconducting device according to the present disclosure is provided so as to at least partially cover the heat transfer surface cooled by the liquid refrigerant and the heat transfer surface, and has lower heat transfer than the heat transfer surface. The heat transfer surface comprises a coating layer having a ratio, and the heat transfer surface includes a plurality of heat transfer regions and a plurality of heat transfer suppression regions alternately arranged with the plurality of heat transfer regions. The coating layer is provided so as to selectively cover the heat transfer suppressing region of the heat transfer surface, or (b) the thickness of the coating layer is larger than that of each of the heat transfer regions. The heat suppression region is larger.

According to the superconducting device according to the present disclosure, a coating layer having a thermal conductivity lower than that of the heat transfer surface is used, and a plurality of heat transfer regions and a plurality of heat transfer suppression regions are alternately arranged to boil the film. The formation of heat can be suppressed to maintain the nucleate boiling state, whereby the cooling effect can be maintained high.

It is sectional drawing which shows a part of the superconducting apparatus which concerns on one Embodiment. It is sectional drawing which shows a part of the superconducting apparatus which concerns on one Embodiment. It is a perspective view of the superconducting apparatus which concerns on one Embodiment. It is sectional drawing which follows the AA line in FIG. It is a perspective view of the superconducting apparatus which concerns on one Embodiment. It is sectional drawing which follows the line BB in FIG.

Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present invention to this, and are merely explanatory examples.
For example, expressions that represent relative or absolute arrangements such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric" or "coaxial" are exact. Not only does it represent such an arrangement, but it also represents a state of relative displacement with tolerances or angles and distances to the extent that the same function can be obtained.
For example, expressions such as "same", "equal", and "homogeneous" that indicate that things are in the same state not only represent exactly the same state, but also have tolerances or differences to the extent that the same function can be obtained. It shall also represent the existing state.
For example, an expression representing a shape such as a quadrangular shape or a cylindrical shape not only represents a shape such as a quadrangular shape or a cylindrical shape in a geometrically strict sense, but also an uneven portion or chamfering within a range in which the same effect can be obtained. The shape including the part and the like shall also be represented.
On the other hand, the expressions "equipped", "equipped", "equipped", "included", or "have" one component are not exclusive expressions that exclude the existence of other components.

1 and 2 are cross-sectional views showing a partial configuration of superconducting devices 10 (10A, 10B) according to some embodiments. These superconducting devices 10 have a built-in superconducting member (not shown) and have a heat transfer surface 12 that is in contact with a liquid refrigerant r such as liquid nitrogen and is cooled by the liquid refrigerant r. The superconducting member is cooled to an extremely low temperature via the heat transfer surface 12, so that the electric resistance can be maintained at almost zero. The heat transfer surface 12 is at least partially covered by the coating layer 14, and the coating layer 14 is made of a material having a lower thermal conductivity than the material constituting the heat transfer surface 12. In this way, the heat transfer surface 12 is configured to include a plurality of heat transfer regions Ra and a plurality of heat transfer suppression regions Rb alternately arranged with the plurality of heat transfer regions Ra. Therefore, under the cooling conditions of the same liquid refrigerant r, the heat transfer amount (heat flux) per unit surface area of the heat transfer suppression region Rb is smaller than that of the heat transfer region Ra.

In the superconducting device 10 (10A) shown in FIG. 1, the heat transfer surface 12 is divided into a heat transfer region Ra not covered by the coating layer 14 and a heat transfer suppression region Rb selectively covered by the coating layer 14. Has been done. In the superconducting device 10 (10B) shown in FIG. 2, both the heat transfer surface 12 of the heat transfer region Ra and the heat transfer suppression region Rb are covered with the coating layer 14, and the thickness of the coating layer 14 in the heat transfer suppression region Rb is transferred. It is larger than the thickness of the coating layer 14 in the thermal region Ra.

In these embodiments, the heat transfer between the heat transfer surface 12 and the liquid refrigerant r is suppressed in the heat transfer suppression region Rb, so that the formation of film boiling is suppressed and the nucleate boiling state is reached. Further, since the heat transfer suppression region Rb is alternately arranged with the heat transfer region Ra, even if the film boiling is locally formed in the heat transfer region Ra, the propagation of the film boiling is blocked by the heat transfer suppression region Rb. Therefore, the expansion of the film boiling over the entire heat transfer surface 12 is suppressed, and the region in the nucleate boiling state is maintained. As a result, the heat flux can be greatly improved as compared with the case where the heat transfer surface 12 shifts to the boiling state of the entire surface, and the cooling effect of the superconducting member can be maintained at a high level.

The coating layer 14 is made of a fluororesin having a low thermal conductivity, such as PTFE. Fluororesin can maintain stable physical properties and exert a cooling effect even in an environment where the superconducting member is cooled at an extremely low temperature.

In one embodiment, as shown in FIG. 1, a coating layer 14 is selectively provided in the heat transfer suppressing region Rb, and the coating layer 14 forms a protrusion 18 protruding from the heat transfer surface 12. Even if the heat transfer surface 12 shifts to film boiling due to an increase in the temperature difference between the liquid refrigerant r and the heat transfer surface 12, the surface temperature rise in the heat transfer suppression region Rb is suppressed, so that the effect of suppressing film boiling is suppressed. Can be maintained. As a result, the temperature drop on the heat transfer surface 12 becomes large, and if the heat transfer surface drops beyond a certain temperature, the film cannot return to boiling, nucleate boiling occurs at that location, and the vapor film is divided. The vapor film covering the heat transfer surface 12 becomes partially unstable in the nucleate boiling region. In this way, transition boiling begins, and eventually the transition to nucleate boiling, in which each bubble is separated.

According to the present embodiment, since the protrusion 18 is formed in the heat transfer suppression region Rb, the surface area of the heat transfer suppression region Rb can be increased. Therefore, it is necessary to consider the fin efficiency of the protrusion 18 to reduce the overall heat transfer amount of the heat transfer surface 12 when not boiling, which is caused by the formation of the heat transfer suppression region Rb, but the surface area of the heat transfer suppression region Rb. Can be compensated for by the increase in.

One or a plurality of protrusions 18 are formed in the heat transfer suppression region Rb. The shape of the protrusion 18 may be, for example, a columnar shape, a wall shape (including a linear or curved wall), and the like, and is not particularly limited to a specific shape. Further, the arrangement of the plurality of formed protrusions 18 may be, for example, parallel, crossed, or the like, and is not particularly limited to a specific arrangement.

In the superconducting device 10 (10A) shown in FIG. 1, the coating layer 14 is provided only in the heat transfer suppressing region Rb, and is not provided in the heat transfer region Ra. According to this embodiment, since the amount of heat transfer between the heat transfer region Ra and the heat transfer suppression region Rb with the liquid refrigerant r is differentiated by the presence or absence of the coating layer 14, the heat transfer amounts between the two can be easily differentiated.
In the superconducting device 10 (10B) shown in FIG. 2, the coating layer 14 is formed in the heat transfer region Ra and the heat transfer suppression region Rb, and the heat transfer surface 12 is the heat transfer region Ra in which the coating layer 14 in contact with the liquid refrigerant is formed. Becomes the surface of. Since the difference in heat conduction between the heat transfer region Ra and the heat transfer suppression region Rb is differentiated by the film thickness of the coating layer 14, the slight difference in the amount of heat transfer between the two can be accurately differentiated by the film thickness of the coating layer 14. ..

In the superconducting devices 10 (10A, 10B) shown in FIGS. 1 and 2, the entire protrusion 18 is composed of the coating layer 14, but only the surface of the protrusion 18 is formed by the coating layer 14, and the protrusion 18 is formed. The inner part of the may be made of another material. For example, in the superconducting device 10 (10A), the inner portion of the protrusion 18 may be made of the same material as the material forming the heat transfer surface 12.

When the temperature difference between the heat transfer surface 12 and the liquid refrigerant r increases and film boiling is formed on the heat transfer surface 12, as shown in FIG. 1, the film boiling region R formed in contact with the heat transfer surface 12 liquid phase region R ₂ is formed on the outside of _one of the gas-liquid boundary GL. For example, although it depends on the conditions, the thickness of the film boiling region R ₁ is usually about several tens of μm to 0.1 mm. In one embodiment, configured so that at least the tip portion of the projecting portion 18 formed on the heat transfer suppressing region Rb reaches the height of the liquid phase region R ₂ from the gas-liquid boundary GL at least 0.1mm from the heat transfer surface 12 Has been done. As a result, as shown in FIG. 1, since the tip of _{the protrusion 18 can reach the liquid phase region R 2} , the rise in surface temperature is suppressed around the protrusion 18, and the effect of suppressing film boiling can be maintained. .. The steam film covering the heat transfer surface 12 partially becomes a nucleate boiling region and becomes unstable. In this way, transition boiling begins, and eventually the transition to nucleate boiling, in which each bubble is separated. Thus good is expanded nucleate boiling region for holding the heat transfer, the cooling by the liquid phase can be suppressed the formation of the film boiling region R ₁ on the surface of the heat transfer surface 12, a high cooling effect of the superconducting member Can be maintained.

In one embodiment, the protrusion 18'shown in FIG. 2 may be replaced with the protrusion 18'forming the heat transfer region Ra. The protrusion 18'after replacement is made of a metal or the like having a higher thermal conductivity than the coating layer 14, and is arranged in contact with the heat transfer surface 12. In this embodiment, the temperature of the protrusion 18'is higher than that of the coating layer 14, and even if film boiling is formed on the surface of the protrusion 18', the temperature rise of the surface temperature is suppressed by the coating layer 14, so that the film boiling is suppressed. It can be expected to maintain the inhibitory effect of.

FIG. 3 is a perspective perspective view showing the superconducting device 10 (10C) according to the embodiment, and FIG. 4 is a cross-sectional view taken along the line AA in FIG. In the superconducting device 10 (10C), a cryogenic liquid refrigerant r (for example, liquid nitrogen) is stored in a heat insulating storage tank 20, and the superconducting current limiter 22 is immersed in the liquid refrigerant r inside the storage tank 20. There is. The superconducting member incorporated in the superconducting current limiter 22 is composed of, for example, a superconducting magnet, and is held at an extremely low temperature by the liquid refrigerant r. The superconducting current limiter 22 usually exhibits a superconducting state in which the electric resistance becomes almost zero, and when a current exceeding a permissible value flows and a short circuit occurs, the superconducting state is broken and the state is transferred (quenched) to the normal conducting state. When transitioning to the normal conduction state, electrical resistance is generated, and this resistance is used to suppress the short-circuit current. The surface of the superconducting current limiter 22 constitutes a heat transfer surface 12 in contact with the liquid refrigerant r.

The heat transfer surface 12 is at least partially covered with a coating layer 14 (18) made of a material having a lower thermal conductivity than the material constituting the heat transfer surface 12, and has a plurality of heat transfer regions Ra and a plurality of heat transfer regions Ra. It includes a plurality of heat transfer suppressing regions Rb having a thermal conductivity smaller than that of the heat transfer regions Ra arranged alternately with the heat transfer regions Ra of the above. For example, it has any of the configurations of the superconducting devices 10 (10A, 10B) shown in FIGS. 1 and 2. Since the superconducting current limiter 22 is efficiently cooled by the liquid refrigerant r during standby, it is possible to maintain a superconducting state with almost no loss at all times.

During the current limiting operation, the temperature of the superconducting current limiter 22 rises significantly due to the sudden heat generation due to the sudden normal conduction transition (quenching), and the surrounding liquid refrigerant r is rapidly vaporized. After the current limiting operation is completed (after the current is cut off), the liquid refrigerant r is promptly supplied to the storage tank 20 for recooling. At this time, the surface of the superconducting current limiter 22 is suppressed from boiling by the coating layer 14 and is rapidly cooled to return to the superconducting state, so that it is possible to prepare for the next current limiting device operation.

In one embodiment, the partition wall of the storage tank 20 is composed of double walls, and a vacuum space is formed between the outer wall surface and the inner wall surface of these double walls. As a result, the storage tank 20 can obtain high heat insulating properties.

FIG. 5 is a perspective view showing the superconducting device 10 (10D) according to the embodiment, and FIG. 6 is a cross-sectional view taken along the line BB in FIG. The superconducting device 10 (10D) has a cable core 32 incorporating a superconducting wire (not shown) and a cable core 32, and a space filled with a liquid refrigerant r is formed between the cable core 32 and the inner side wall. It is provided with a pipe 30 having a heat insulating property. The outer peripheral surface of the cable core 32 has a heat transfer surface 12. The heat transfer surface 12 is at least partially covered with a coating layer 14 (18) made of a material having a lower thermal conductivity than the material constituting the heat transfer surface 12, and has a plurality of heat transfer regions Ra and a plurality of heat transfer regions Ra. It includes a plurality of heat transfer suppressing regions Rb having a thermal conductivity smaller than that of the heat transfer regions Ra arranged alternately with the heat transfer regions Ra of the above. For example, it has any of the configurations of the superconducting devices 10 (10A, 10B) shown in FIGS. 1 and 2. Since the superconducting member built in the cable core 32 is efficiently cooled by the liquid refrigerant r via the heat transfer surface 12, it is possible to maintain a superconducting state with almost no loss at all times.

When the superconducting device 10 (10D) is destroyed in the superconducting state due to an overcurrent or the like and dislocated (quenched) to the normal conducting state, the temperature of the cable core 32 rises sharply and the surrounding liquid refrigerant r evaporates violently. At this time, the energization of the cable core 32 is cut off. If there is no abnormality in the superconducting device 10 (10D), the liquid refrigerant r is supplied again, aiming to return to the superconducting state and re-energize. At the time of this recooling, the coating layer 14 suppresses the boiling state of the film, so that the cooling time is significantly shortened and the re-energization can be restarted promptly.

In one embodiment, the partition wall of the pipe 30 is composed of double walls, and a vacuum space is formed between the outer wall surface and the inner side wall of these double walls. As a result, the pipe 30 can obtain high heat insulating properties.

In one embodiment, as shown in FIGS. 3 to 6, the heat transfer suppression regions Rb are formed in a grid pattern, and the heat transfer regions Ra are discretely formed between the heat transfer suppression regions Rb. As a result, the nucleate boiling region is formed in the heat transfer suppression region Rb formed in a grid pattern, so that the film boiling is locally generated even in the heat transfer region Ra discretely formed between the heat transfer suppression regions Rb. Even if it is formed, the increase in surface temperature is suppressed in the heat transfer suppressing region Rb, so that the effect of suppressing film boiling can be maintained. The vapor film covering the heat transfer surface becomes partially unstable in the nucleate boiling region. Since the transition boiling starts in this way and eventually shifts to nucleate boiling in which each bubble is separated, the expansion of the membrane boiling region can be suppressed and eliminated.

In one embodiment, contrary to the embodiments shown in FIGS. 3 to 6, the heat transfer regions Ra are formed in a grid pattern, and the heat transfer suppression regions Rb are discretely formed between the heat transfer regions Ra. ing. As a result, the heat transfer suppressing region Rb capable of suppressing the film boiling is discretely formed between the heat transfer regions Ra formed in a grid pattern, so that the film boiling is locally formed in the heat transfer region Ra. However, since the rise in surface temperature is suppressed in the heat transfer suppression region Rb, the effect of suppressing film boiling can be maintained, and the expansion of the film boiling region can be suppressed and eliminated.

The contents described in each of the above embodiments are grasped as follows, for example.

(1) The superconducting device according to one embodiment is provided so as to cover at least a part of the heat transfer surface cooled by the liquid refrigerant and the heat transfer surface, and has a lower heat conductivity than the heat transfer surface. A coating layer (for example, the coating layer 14 shown in FIGS. 1 and 2) is provided, and the heat transfer surface has a plurality of heat transfer regions (for example, the heat transfer region Ra shown in FIGS. 1 and 2) and the heat transfer region. It includes a plurality of heat transfer regions and a plurality of heat transfer suppression regions (for example, heat transfer suppression regions Rb shown in FIGS. 1 and 2) alternately arranged, and (a) the coating layer is the heat transfer surface. Of these, the heat transfer suppressing region is provided so as to selectively cover (for example, the embodiment shown in FIG. 1), or (b) the thickness of the coating layer is higher than that of each of the heat transfer regions. The heat transfer suppression region is larger (for example, the embodiment shown in FIG. 2).

According to such a configuration, heat conduction is suppressed in the heat transfer suppressing region of the heat transfer surface and the surface temperature rise of the heat transfer surface is suppressed, so that the formation of film boiling can be suppressed and the nucleate boiling state can be maintained. .. Further, since a plurality of heat transfer regions and a plurality of heat transfer suppression regions are alternately arranged, even if film boiling is locally formed in each heat transfer region, the film boiling spreads over the entire heat transfer surface. Can be blocked in each heat transfer suppression region. As a result, the occurrence of film boiling can be suppressed locally, and the nucleate boiling state can be maintained mainly on the entire heat transfer surface, so that a decrease in the cooling effect of the superconducting member can be suppressed and eliminated.

(2) In one embodiment, in the superconducting device according to (1), a protrusion (for example, FIG. 1) protruding from the heat transfer surface by the coating layer selectively provided in the heat transfer suppression region. And the protrusion 18) shown in FIG. 2 is formed.

According to such a configuration, the surface area of the heat transfer suppressing region can be increased by forming the protrusions in the heat transfer suppressing region. As a result, it is necessary to consider the fin efficiency due to the protrusions, but it is possible to suppress a decrease in the amount of heat transfer due to the formation of the heat transfer suppressing region.

(3) In one embodiment, in the superconducting device according to (2), at least the tip of the protrusion is 0.1 mm or more from the heat transfer surface and a liquid phase region from the gas-liquid boundary (for example, FIG. 1). It is configured to reach the height of the liquid phase region R _{2) shown in.}

When the temperature difference between the heat transfer surface and the liquid refrigerant increases and film boiling is formed on the heat transfer surface, a liquid phase region is formed outside _{the film boiling region (for example, the membrane boiling region R1 shown in FIG. 1).} To. According to the above configuration, at least the tip of the protrusion is configured to reach the height of the liquid phase region from the gas-liquid boundary (for example, the gas-liquid boundary GL shown in FIG. 1) at 0.1 mm or more from the heat transfer surface. Therefore, since the rise in the surface temperature of the tip of the protrusion is suppressed, the effect of suppressing the film boiling can be maintained. The vapor film covering the heat transfer surface partially becomes unstable in the nucleate boiling region, transition boiling begins, and then the transition to nucleate boiling in which each bubble is separated. In this way, the nucleate boiling state can be maintained. As a result, the good heat transfer region in the nucleate boiling region can be extended to the heat transfer surface via the protrusions. Therefore, the expansion of film boiling can be prevented and eliminated.

(4) In one embodiment, in the superconducting device according to any one of (1) to (3), the heat transfer suppression region (for example, the heat transfer suppression region Rb shown in FIG. 4 or FIG. 6) is a lattice. Each of the heat transfer regions (for example, the heat transfer region Ra shown in FIG. 4 or FIG. 6) is discretely formed between the heat transfer suppression regions.

According to such a configuration, nucleate boiling is formed in the heat transfer suppression region formed in a grid pattern, so that the film boiling is locally generated in the heat transfer region formed discretely between the heat transfer suppression regions. Even if it is formed, the nucleate boiling formed in the heat transfer suppressing region can suppress and eliminate the expansion of the membrane boiling region.

(5) In one embodiment, in the superconducting device according to any one of (1) to (3), the heat transfer regions are formed in a grid pattern, and each of the heat transfer regions is formed between the heat transfer regions. The suppression regions are formed discretely.

According to such a configuration, heat transfer suppressing regions capable of suppressing film boiling are discretely formed between the heat transfer regions formed in a grid pattern, so that the heat transfer regions formed in a grid pattern are locally formed. Even if the film boiling is formed, the nucleate boiling formed in the heat transfer suppression region can suppress and eliminate the expansion of the membrane boiling region.

(6) In one embodiment, the superconducting device according to any one of (1) to (5) (for example, the superconducting device 10 (10C) shown in FIG. 3) is a heat insulating wall in which the liquid refrigerant is stored. And a superconducting current limiter (for example, the superconducting current limiter 22 shown in FIG. 3) immersed in the liquid refrigerant.
The superconducting current limiter has the heat transfer surface in contact with the liquid refrigerant.

According to such a configuration, the superconducting current limiter having the above configuration is efficiently cooled by the liquid refrigerant through the heat transfer surface and can suppress the formation of film boiling on the surface of the heat transfer surface. Therefore, the superconducting member Can quickly return to the superconducting state after current limiting operation or quenching.

(7) In one embodiment, the superconducting device according to any one of (1) to (5) (for example, the superconducting device 10 (10D) shown in FIG. 5) and a cable core (for example, a cable core including a superconducting wire). The cable core 32) shown in FIG. 5 and a pipe having a heat insulating wall having a built-in cable core and a space filled with a liquid refrigerant between the cable core and the inner surface thereof are included. The outer peripheral surface of the above has the heat transfer surface.

According to such a configuration, the superconducting device having the above configuration is efficiently cooled by the liquid refrigerant through the heat transfer surface and can suppress the formation of film boiling on the surface of the heat transfer surface, so that most of the superconducting members are present. It can maintain a superconducting state without loss.

10 (10A, 10B, 10C, 10D) Superconducting equipment 12 Heat transfer surface 14 Coating layer 18 Protrusions 20 Storage tank 22 Superconducting current limiter 30 Piping 32 Cable core R ₁ Film boiling region R ₂ Liquid phase region Ra Heat transfer region Rb Heat transfer region r Liquid refrigerant GL Gas-liquid boundary

Claims (7)

The heat transfer surface cooled by the liquid refrigerant and
A coating layer provided so as to cover at least a part of the heat transfer surface and having a lower thermal conductivity than the heat transfer surface.
With
The heat transfer surface is
With multiple heat transfer areas
A plurality of heat transfer suppression regions alternately arranged with the plurality of heat transfer regions,
Including
(A) The coating layer is provided so as to selectively cover the heat transfer suppressing region in the heat transfer surface.
Or
(B) A superconducting device in which the thickness of the coating layer is larger in each of the heat transfer suppressing regions than in each of the heat transfer regions. The superconducting device according to claim 1, wherein a protrusion protruding from the heat transfer surface is formed by the coating layer selectively provided in the heat transfer suppression region. The superconducting device according to claim 2, wherein at least the tip of the protrusion is configured to reach the height of the liquid phase region from the gas-liquid boundary at 0.1 mm or more from the heat transfer surface. The superconducting device according to any one of claims 1 to 3, wherein the heat transfer suppressing regions are formed in a grid pattern, and each of the heat transfer regions is discretely formed between the heat transfer suppressing regions. The superconducting device according to any one of claims 1 to 3, wherein the heat transfer regions are formed in a grid pattern, and the heat transfer suppression regions are discretely formed between the heat transfer regions. A storage tank having a heat insulating wall in which the liquid refrigerant is stored, and
A superconducting current limiter immersed in the liquid refrigerant and
Including
The superconducting device according to any one of claims 1 to 5, wherein the superconducting current limiting device has the heat transfer surface in contact with the liquid refrigerant. With a cable core containing superconducting wire,
A pipe having a built-in cable core and a heat insulating wall in which a space filled with the liquid refrigerant is formed between the cable core and the inner surface.
Including
The superconducting device according to any one of claims 1 to 5, wherein the outer peripheral surface of the cable core has the heat transfer surface.

Images