JP7065745B2 - Ultra-low temperature fluid circulation cooling system - Google Patents

Description

The present invention relates to an ultra-low temperature fluid circulation cooling system.

A Brayton cycle refrigerator using liquid nitrogen, liquid hydrogen, liquid helium, or the like is known as a cooling liquid for cooling high-temperature superconducting power equipment (transmission cable, current limiter, transformer, etc.). A cryogenic fluid circulation pump (hereinafter sometimes referred to simply as a "pump") is indispensable for cooling the coolant with a Brayton cycle refrigerator and circulating it in a high-temperature superconducting power device. The coolant boosted by the pump is supplied to the heat exchanger of the Brayton cycle refrigerator and cooled. A system configuration for cooling high-temperature superconducting power equipment using a Brayton cycle refrigerator and a pump is referred to as a "cooling system".

By the way, the conventional ultra-low temperature fluid circulation type cooling system has a first closed flow path for circulating a high-pressure refrigerant gas and a second closed flow path for circulating a coolant for cooling the object to be cooled. It has been reported that the cooling liquid is circulated by a circulation pump installed in the vacuum insulation container, which is connected to a drive motor installed outside the vacuum insulation container by a pump spindle.

Japanese Unexamined Patent Publication No. 64-063696 Japanese Patent No. 4744857

However, as shown in FIG. 3, in the conventional ultra-low temperature fluid circulation type cooling system, a part of the coolant in the circulation pump is vaporized by the invading heat from the drive motor during the pump precooling or operation. , Bubbles are generated and cavitation is likely to occur in the circulation pump, so it is necessary to install a degassing valve and discharge the bubbles together with the coolant from the degassing valve to the outside, and a considerable amount of coolant is wasted. There was a problem of becoming.

The present invention has been made for the above-mentioned circumstances, and is an extremely low temperature capable of suppressing waste of the coolant by eliminating the need to discharge bubbles generated by vaporization of the coolant during pump precooling or operation. An object of the present invention is to provide a fluid circulation type cooling system.

In order to solve such a problem, the present invention has the following configuration.
[1] A compressor that compresses and circulates refrigerant gas,
A main heat exchanger that cools the compressed refrigerant gas by heat exchange with the returning refrigerant gas,
An expansion turbine that adiabatically expands the cooled refrigerant gas,
An auxiliary heat exchanger that exchanges heat between the ultra-low temperature refrigerant gas that has left the expansion turbine and the coolant.
A circulation pump having an internal impeller that circulates the coolant between the auxiliary heat exchanger and the object to be cooled.
The circulation pump drive motor that drives the circulation pump,
A first closed flow path constituting a circulation path for circulating the refrigerant gas after heat exchange in the secondary heat exchanger to the compressor via the main heat exchanger.
A second closed flow path constituting a circulation path for circulating the cooling liquid after heat exchange by the secondary heat exchanger is provided by the circulation pump.
The main heat exchanger, the expansion turbine, the auxiliary heat exchanger, the circulation pump, and the circulation pump driving motor are housed in the same vacuum container.
The impeller inside the circulation pump is arranged below the lowest portion of the auxiliary heat exchanger and the flow path connecting the circulation pump and the auxiliary heat exchanger, so that the ultra-low temperature fluid circulation type cooling can be performed. system.
[2] The ultra-low temperature fluid circulation type cooling system according to [1], wherein the coolant inlet of the circulation pump is arranged below the impeller inside the circulation pump.
[3] The ultra-low temperature fluid circulation type cooling system according to [1] or [2], wherein the circulation pump drive motor is installed above the circulation pump.
[4] The ultra-low temperature fluid circulation cooling system according to any one of [1] to [3], wherein the pump including the circulation pump and the circulation pump drive motor is a short-axis pump.
[5] The ultra-low temperature fluid circulation type cooling system according to any one of [1] to [4], wherein the cooling medium of the circulation pump drive motor is a brine liquid.
[6] The item according to any one of [1] to [3], wherein the pump including the circulation pump and the circulation pump drive motor is an integrated pump and is a pump completely immersed in a liquid. Very low temperature fluid circulation cooling system.

The ultra-low temperature fluid circulation type cooling system of the present invention can suppress waste of the coolant by eliminating the need to discharge bubbles generated by vaporization of the coolant during pump precooling or operation.

It is a figure which shows the structure of 1st Embodiment in the ultra-low temperature fluid circulation type cooling system of this invention. It is a figure which shows the structure of the 2nd Embodiment in the ultra-low temperature fluid circulation type cooling system of this invention. It is a figure which shows the structure of the cryogenic fluid circulation type cooling system which is an example of the conventional cooling system.

The ultra-low temperature fluid circulation cooling system of the present invention includes a compressor, a main heat exchanger, an expansion turbine, an auxiliary heat exchanger, a circulation pump, a circulation pump drive motor, and a first closed flow path. , The main heat exchanger, the expansion turbine, the auxiliary heat exchanger, the circulation pump, and the circulation pump driving motor are housed in the same vacuum vessel. The impeller inside the circulation pump is arranged below the lowest portion of the auxiliary heat exchanger and the flow path connecting the circulation pump and the auxiliary heat exchanger.

Here, FIG. 3 is a diagram showing the configuration of a cryogenic fluid circulation type cooling system which is an example of a conventional cooling system. As shown in FIG. 3, in the conventional ultra-low temperature fluid circulation type cooling system 100, the first closed flow path CP101 is a high pressure refrigerant gas circulation path. Further, a part of the first closed flow path CP101 is configured to pass through the inside of the vacuum insulation container 111 of the Brayton cycle refrigerator.

A compressor 118 is provided in the first closed flow path CP 101 outside the vacuum insulation container 111, and an expansion turbine 114 is provided in the first closed flow path CP 101 inside the vacuum insulation container 111. There is. The expansion turbine 114 is installed on the top plate 116 of the vacuum insulation container 111. Further, a conventional pump 102 is provided in the second closed flow path CP 102 in the vacuum insulation container 111. The conventional pump 102 is installed on the top plate 116 of the vacuum insulation container 111, similarly to the expansion turbine 114. The conventional pump 102 will be described later. The second closed flow path CP 102 branches on the downstream side of the conventional pump 102. The exhaust path L103 branching from the second closed flow path CP102 extends to the outside of the vacuum insulation container 111, and a gas vent valve 115 is provided at the upper end thereof. Bubbles generated when the coolant is vaporized by the invading heat from the conventional pump 102 are discharged to the outside of the vacuum insulation container 111 by the exhaust path L103.

Inside the vacuum insulation container 111, a main heat exchanger 112 and an auxiliary heat exchanger 113 are provided.
The main heat exchanger 112 is a refrigerant after being compressed by the compressor 118 and then heat-exchanged by the auxiliary heat exchanger 113 with the refrigerant gas supplied to the first closed flow path CP101 via the refrigerant gas inlet. It is provided for cooling by heat exchange with gas.
The sub-heat exchanger 113 contains the refrigerant gas delivered from the expansion turbine 114 flowing through the first closed flow path CP 101 and the liquid nitrogen delivered from the conventional pump 102 flowing through the second closed flow path CP 102. It is provided for heat exchange between them.

Here, the conventional pump 102 will be described in more detail.
The conventional pump 102 has a circulation pump drive motor unit (hereinafter, also simply referred to as “drive motor unit”) 122 and a circulation pump unit 123. The drive motor unit 122 is installed on the top plate 116 of the vacuum heat insulating container 111 and is provided in the atmosphere. On the other hand, the circulation pump unit 123 is housed inside the vacuum insulation container 111. An impeller 121 is provided in the circulation pump unit 123.

The circulation pump unit 123 has a low temperature of 75K to 80K because the cooling liquid, which is an extremely low temperature fluid, flows. On the other hand, the drive motor unit 122 is an air-cooled type or a water-cooled type because the temperature becomes higher than the atmospheric temperature due to the heat generated by the motor and the bearing (in FIG. 3, the water-cooled type is exemplified).

When the object to be cooled is a high-temperature superconducting power device (for example, a superconducting power transmission cable), the coolant is operated at a high pressure of 0.3 to 2 MPa. The drive motor unit 122 has a hermetically sealed pressure-resistant structure so that the coolant does not leak into the atmosphere. Further, the pump spindle 124 connecting the impeller 121 and the drive motor unit 122 has a long shaft structure in order to reduce heat intrusion from the drive motor unit 122 to the circulation pump unit 123.

When operating the conventional pump 102, the circulation pump unit 123 is filled with a coolant. On the other hand, since the drive motor unit 122 is arranged in the normal temperature range, the drive motor unit 122 is in a state of being filled with the gas vaporized by the coolant. Further, the pump spindle 124 has a temperature distribution such that the lower side of the intermediate portion is the boundary between the gas and the liquid. Both ends of the drive motor unit 122 are supported by grease-filled ball bearings. Further, the motor shaft and the pump spindle 124 are connected by a flexible coupling. Further, a ball bearing lubricated with a coolant is arranged on the back surface side of the impeller 121 to prevent the pump spindle 124 from touching around at high speed rotation.

When the pump spindle 124 is not so long, a pump having a structure in which the pump spindle 124 and the motor shaft are integrated and a ball bearing is not provided on the back surface side of the impeller 121 is also known. Here, a pump having a structure in which a ball bearing is not provided on the back surface side of the impeller 121 is referred to as a "short shaft pump".

As described above, this problem was not only in the case of a short-screw pump having a short pump spindle, but also in the case of a long-screw pump (long-screw pump). This is because in Brayton cycle refrigerators, heat exchangers are generally larger than pumps.

Considering that in the conventional cooling system 100, the pump spindle 124 is further lengthened so that the impeller 121 in the circulation pump unit 123 is located below the auxiliary heat exchanger 113, heat conduction. In that respect, it is an additional advantage. However, there is a problem that the bending natural frequency of the shaft is lowered, the spindle swings greatly at high speed rotation, and the ball bearing lubricated by the coolant on the back side of the impeller 121 is extremely worn.

In order to deal with such an assumed situation, as shown by the broken line in FIG. 3, the top plate of the vacuum insulation container 111 of the Brayton cycle refrigerator has a two-stage structure, and the conventional pump 102 is installed on the lower internal top plate 117. As a structure, it is conceivable to avoid lengthening the pump spindle 124. However, since the piping of the circulation pump unit 123 is connected to the auxiliary heat exchanger 113 in the vacuum insulation container 111, it is not possible to take out only the conventional pump 102. Further, even if the vacuum insulation container 111 is divided into two parts instead of the top plate, the vacuum insulation container 111 is required to have a structure in which the conventional pump 102, the expansion turbine 114, the heat exchangers 112, 113 and the like can be taken out integrally. It has a complicated structure. Therefore, it causes a failure of the cooling system 100 and an increase in cost.

On the other hand, the conventional pump 102 is placed horizontally, the drive motor unit 122 is installed on the side surface of the vacuum insulation container 111, and the impeller 121 inside the circulation pump unit 123 is subordinated while realizing the shortening of the pump main shaft 124. It is also conceivable that the heat exchanger 113 is located on the lower side in the vertical direction. However, in this case, it is assumed that the coolant flows into the motor side, the temperature of the drive motor unit 122 becomes low, and the grease-filled ball bearing does not function.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
<First Embodiment>
FIG. 1 is a diagram showing a configuration of a first embodiment in the ultra-low temperature fluid circulation type cooling system of the present invention.
As shown in FIG. 1, the ultra-low temperature fluid circulation cooling system 1A according to the first embodiment includes a compressor 18, a main heat exchanger 12, an expansion turbine 14, an auxiliary heat exchanger 13, and a circulation pump unit (circulation pump). 23, a circulation pump drive motor unit (circulation pump drive motor) 22, a first closed flow path CP1 and a second closed flow path CP2 are roughly configured.

The low-temperature fluid circulation type cooling system 1A of the present embodiment has a configuration in which a part of the first closed flow path CP1 forming the circulation path of the high-pressure refrigerant gas passes through the inside of the vacuum insulation container 11 of the Brayton cycle refrigerator. It has become. The vacuum insulation container 11 is provided with an inlet and an outlet for high-pressure refrigerant gas. Further, in the cryogenic fluid circulation type cooling system 1A of the present embodiment, a part of the second closed flow path CP2 forming the circulation path of liquid nitrogen (LN ₂ ), which is an example of the coolant, is inside the vacuum insulation container 11. It is configured to go through. Further, the vacuum insulation container 11 is provided with an inlet and an outlet for liquid nitrogen.

The refrigerant gas is not particularly limited. As the refrigerant gas, neon, helium, a mixed gas thereof or the like can be used.
The coolant is not particularly limited. As the coolant, liquid nitrogen (LN ₂ ), liquid hydrogen, liquid helium and the like can be used.

The pump 2A includes a circulation pump unit 23 that circulates the coolant between the auxiliary heat exchanger 13 and the object to be cooled (not shown), and a circulation pump drive motor unit that drives the circulation pump unit 23 (hereinafter, simply "drive". (Also referred to as a "motor unit") 22. Further, an impeller 21 is provided inside the circulation pump unit 23. The pump 2A is configured to be installed in the vacuum insulation container 11 together with the circulation pump unit 23 and the drive motor unit 22. The installation position of the pump 2A and the like will be described in detail later.

The body to be cooled is not particularly limited. Examples of the object to be cooled include high-temperature superconducting power devices such as power transmission cables, current limiters, and transformers.

In the first closed flow path CP1, the refrigerant gas after being compressed by the compressor 18 is adiabatically expanded by the expansion turbine 14 to an extremely low temperature, and the refrigerant gas after heat exchange with the coolant in the auxiliary heat exchanger 13 is exchanged. , Is a circulation path that circulates to the compressor 18 via the main heat exchanger 12. A compressor 18 is provided in the middle of the path outside the vacuum insulation container 11 of the first closed flow path CP1. Further, a main heat exchanger 12, an expansion turbine 14, and an auxiliary heat exchanger 13 are provided in the middle of the path in the vacuum insulation container 11 of the first closed flow path CP1.

The main heat exchanger 12 heat exchanges the refrigerant gas supplied to the first closed flow path CP1 through the refrigerant gas inlet with the refrigerant gas after heat exchange with the coolant by the auxiliary heat exchanger 13. It is provided for cooling by.

The sub-heat exchanger 13 includes a very low temperature refrigerant gas flowing from the expansion turbine 14 flowing through the first closed flow path CP1 and liquid nitrogen sent out from the pump 2A flowing through the second closed flow path CP2. It is provided for heat exchange with the coolant).

The expansion turbine 14 is provided to adiabatically expand the cooled refrigerant gas. Further, the expansion turbine 14 is configured to be installed on the top plate 16 of the vacuum heat insulating container 11.

The second closed flow path CP2 constitutes a circulation path for circulating the cooling liquid in the circulation pump unit 23 of the pump 2A. In the second closed flow path CP2, the pump 2A is provided between the coolant inlet in the vacuum insulation container 11 and the auxiliary heat exchanger.

On the downstream side of the pump 2A of the second closed flow path CP2, the air bubbles generated by the vaporization of the coolant due to the invading heat from the pump 2A are discharged to the outside from the outlet of the coolant of the circulation pump 23. An exhaust path L3 that branches upward is provided. The exhaust path L3 extends outside the vacuum insulation container 11, and a gas vent valve 15 is provided at the upper end thereof.

The drive motor unit 22 and the circulation pump unit 23 constituting the pump 2A are both installed in the vacuum insulation container 11. Therefore, the pump spindle 24 that connects the impeller 21 in the circulation pump section 23 and the drive motor section 22 can have a short shaft structure. That is, the pump 2A is a short-axis pump, and the structure inside the vacuum insulation container 11 can be simplified. Since the drive motor unit 22 is located in the vacuum heat insulating container 11, the cooling medium pipe L4 has a structure to be introduced into the vacuum heat insulating container 11.

Here, in particular, the impeller 21 inside the circulation pump unit 23 is vertically lower than the lowest portion of the auxiliary heat exchanger 13 and the flow path CP2 _LOW connecting the circulation pump unit 23 and the auxiliary heat exchanger 13. It has a structure arranged in.

With such a structure, even if a part of the coolant is vaporized to become bubbles due to the invading heat from the drive motor unit 22 during pump precooling or operation, the bubbles do not enter the impeller 21 portion and are combined with the coolant. The air bubbles flow from the outlet of the circulation pump unit 23 to the sub-heat exchanger 13 and are cooled by the sub-heat exchanger 13 to liquefy the bubbles again. That is, it is possible to prevent the impeller 21 from idling due to air bubbles entering the impeller 21. More specifically, at the time of rising, the inside of the second closed flow path CP2 (particularly, the inside of the flow path CP2 _LOW ) becomes a gas pool, which is also flowed to the auxiliary heat exchanger 13 together with the coolant at the start of operation. In addition, air bubbles generated by partial vaporization of the coolant during operation are also flowed to the auxiliary heat exchanger 13 together with the coolant, cooled and reliquefied. In any case, the impeller 21 portion can always be kept filled with the liquid.

As a result, it is not necessary to discharge air bubbles from the degassing valve 15 to the outside together with the coolant at the time of precooling before the pump operation, and the degassing valve 15 can be basically kept in the "closed" state even during the operation. As it is, the occurrence of cavitation in the circulation pump unit 23 can be suppressed. Therefore, the work process can be reduced and the waste of the coolant can be suppressed.

The position of the impeller 21 inside the circulation pump unit 23 is vertically lower than the lowest portion of the auxiliary heat exchanger 13 and the flow path CP2 _LOW connecting the circulation pump unit 23 and the auxiliary heat exchanger 13. If it is arranged, there is no particular limitation, and the impeller 21 inside the circulation pump unit 23 may be inside the vertical projection of the auxiliary heat exchanger 13 or outside the vertical projection. In particular, from the viewpoint of making the vacuum insulation container 11 compact, it is preferable that the impeller 21 inside the circulation pump unit 23 is outside the vertical projection of the auxiliary heat exchanger 13.

Further, it is preferable that the drive motor unit 22 is installed above the circulation pump unit 23 so that the coolant does not flow into the drive motor unit 22. Further, it is preferable that the coolant inlet 23a of the circulation pump unit 23 is installed vertically below the impeller 21 inside the circulation pump unit 23.

By the way, the cooling medium supplied to the drive motor unit 22 is not particularly limited, and ordinary fresh water (water) or brine liquid (antifreeze liquid) can be used. Here, the brine solution means a non-freezing cold heat medium having a freezing point lower than that of water and which does not freeze even when the temperature becomes 0 ° C. or lower.

It is preferable to use a brine solution as the cooling medium. Since the brine liquid does not freeze even when the drive motor unit 22 becomes 0 ° C. or lower, the pump 2A can be operated without any problem if the drive motor unit 22 reaches about −20 ° C.

Examples of the brine solution include an inorganic brine solution and an organic brine solution. These may be used alone or in combination of two or more, or may contain additives such as preservatives and rust inhibitors.
Examples of the inorganic brine solution include an aqueous solution of calcium chloride, an aqueous solution of sodium chloride, and an aqueous solution of magnesium chloride.
Examples of the organic brine solution include propylene glycol aqueous solution, ethylene glycol aqueous solution, methanol solution, ethanol solution and the like.

As described above, according to the ultra-low temperature fluid circulation type cooling system 1A of the present embodiment, it is not necessary to discharge the bubbles generated by the vaporization of the coolant during pump precooling or operation, and the work process can be performed. It will be reduced. In addition, waste of coolant is suppressed.

Further, if the drive motor unit 22 is installed on the upper side (upper side) of the circulation pump unit 23, in addition to the above effect, the coolant flows to the drive motor unit 22 side and the motor becomes low temperature. It is possible to prevent the grease-filled ball bearings from failing due to the storage.

Further, according to the ultra-low temperature fluid circulation type cooling system 1A of the present embodiment, since the pump 2A is a short shaft pump, it is possible to suppress the wear of the ball bearing in addition to the above effect.

<Second Embodiment>
FIG. 2 is a diagram showing a configuration of a second embodiment in the ultra-low temperature fluid circulation type cooling system of the present invention. Here, the same components as those in the first embodiment are designated by the same reference numerals, and duplicate description thereof will be omitted below.

In the ultra-low temperature fluid circulation type cooling system 1A of the first embodiment described above, a short shaft pump in which the circulation pump unit 23 and the drive motor unit 22 are connected by a short pump spindle 24 is adopted as the pump 2A. However, in the ultra-low temperature fluid circulation type cooling system 1B according to the second embodiment, as shown in FIG. 2, as the pump 2B, an integrated pump in which a circulation pump unit and a circulation pump drive motor unit are integrated is used. It is adopted. As the integrated pump, a submerged pump main body can be used. In the present embodiment, the pump 2B is housed in the vacuum heat insulating container 11, and the cooling liquid is introduced into the vacuum heat insulating container 11, so that the entire pump 2B is immersed in the liquid.
The same effect as that of the first embodiment can be obtained by the second embodiment.

As described above, according to each of the above-described embodiments, even if a part of the coolant is vaporized by the invading heat from the circulation pump portion during precooling or operation of the pump to become bubbles, the bubbles are transferred to the impeller 21. Instead of entering, it flows from the pump outlet to the sub-heat exchanger 13 together with the coolant, and is cooled by the sub-heat exchanger 13, so that the bubbles are liquefied again. Therefore, there is no need to open the gas vent valve 15, the coolant is not wasted, and air bubbles do not accumulate in the impeller 21 portion, so that the coolant can always be filled.

At this time, since the entire pump is installed in the vacuum insulation container 11, the transfer tube is not required and the pump spindle can be a short axis as a premise.

By the way, Patent Document 1 and Patent Document 2 disclose a configuration of a pump in which a pump is housed in a vacuum heat insulating container, a cooling liquid is introduced into the heat insulating container, and the entire pump is immersed in the liquid. ..

When the pumps disclosed in Patent Document 1 and Patent Document 2 are to be applied as they are to a cooler system of a high-temperature superconducting power device, the vacuum insulation container for accommodating the pump and the vacuum insulation container of the Brayton cycle refrigerator are respectively. It had to be installed separately and interconnected using a vacuum insulated transfer tube as described above. As a result, there are problems such as pressure loss of the transfer tube, installation space, and increase in cost.

On the other hand, according to each of the above-described embodiments, the transfer tube is unnecessary because both the circulation pump unit and the drive motor unit constituting the pump are housed in the vacuum insulation container of the refrigerator.

The cryogenic fluid circulation cooling system of the present invention produces, for example, a coolant (liquid nitrogen, liquid hydrogen, liquid helium, etc.) for cooling high temperature superconducting power equipment (transmission cable, current limiter, transformer, etc.). Can be used for.

1A, 1B, 100 ... Ultra-low temperature fluid circulation cooling system 2A, 2B, 102 ... Pump 11,111 ... Vacuum insulation container 12,112 ... Main heat exchanger 13,113 ... Sub Heat exchangers 14, 114 ... Expansion turbines 15, 115 ... Gas vent valves 16, 116 ... Top plates 18, 118 ... Compressors 21, 121 ... Impellers 22, 122 ... Circulation Pump drive motor section (circulation pump drive motor)
23,203 ... Circulation pump section (circulation pump)
23a ... Coolant inlet 24,124 ... Pump spindle CP1, CP101 ... First closed flow path CP2, CP102 ... Second closed flow path CP2 _LOW ... Circulation pump section and auxiliary heat Channel connecting the exchanger

Claims (6)

A compressor that compresses and circulates refrigerant gas,
A main heat exchanger that cools the compressed refrigerant gas by heat exchange with the returning refrigerant gas,
An expansion turbine that adiabatically expands the cooled refrigerant gas,
An auxiliary heat exchanger that exchanges heat between the ultra-low temperature refrigerant gas that has left the expansion turbine and the coolant.
A circulation pump having an internal impeller that circulates the coolant between the auxiliary heat exchanger and the object to be cooled.
The circulation pump drive motor that drives the circulation pump,
A first closed flow path constituting a circulation path for circulating the refrigerant gas after heat exchange in the secondary heat exchanger to the compressor via the main heat exchanger.
A second closed flow path constituting a circulation path for circulating the cooling liquid after heat exchange by the secondary heat exchanger is provided by the circulation pump.
The main heat exchanger, the expansion turbine, the auxiliary heat exchanger, the circulation pump, and the circulation pump driving motor are housed in the same vacuum container.
The impeller inside the circulation pump is arranged below the lowest portion of the auxiliary heat exchanger and the flow path connecting the circulation pump and the auxiliary heat exchanger, so that the ultra-low temperature fluid circulation type cooling can be performed. system. The ultra-low temperature fluid circulation type cooling system according to claim 1, wherein the coolant inlet of the circulation pump is arranged below the impeller inside the circulation pump. The ultra-low temperature fluid circulation type cooling system according to claim 1 or 2, wherein the circulation pump drive motor is installed above the circulation pump. The ultra-low temperature fluid circulation cooling system according to any one of claims 1 to 3, wherein the pump including the circulation pump and the circulation pump drive motor is a short-axis pump. The ultra-low temperature fluid circulation type cooling system according to any one of claims 1 to 4, wherein the cooling medium of the circulation pump drive motor is a brine liquid. The ultra-low temperature fluid circulation according to any one of claims 1 to 3, wherein the pump including the circulation pump and the circulation pump drive motor is an integrated pump, and the entire pump is immersed in a liquid. Formula cooling system.

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