JP2018189322A - Cooling device for superconducting cable and cooling method of superconducting cable using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cooling device for superconducting cable which achieves energy consumption efficiency surpassing a conventional cooling device for superconducting cable using a refrigeration machine, and which can reduce refrigerant consumption by diffusion into the atmosphere, and to provide a cooling method of superconducting cable using the same.SOLUTION: A cooling device 1 for superconducting cable at least includes a superconducting cable cooling unit 10, a first supply unit 20 and a supply unit 30. The first supply unit 20 mainly includes: a first refrigerant storage tank 23 for storing a first refrigerant in a liquid state; a compressor 26 for compressing the first refrigerant in a gaseous state exhausted from the superconducting cable cooling unit 10; a first heat exchanger 27 for cooling and liquefying the first refrigerant in the gaseous state by heat exchange; and a first refrigerant circulation passage 21 for connecting the first refrigerant storage tank 23, the compressor 26 and the first heat exchanger 27, and for circulating the first refrigerant.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a cooling device for a superconducting cable and a method for cooling the superconducting cable using the same, and more specifically, energy consumption efficiency exceeding that of a conventional cooling device for a superconducting cable using a refrigerator, and cooling of the superconducting cable. The present invention relates to a cooling device for a superconducting cable and a cooling method for the superconducting cable using the same.

  When cooling the superconducting cable, a liquid refrigerant such as liquid nitrogen is used as the refrigerant. In order to prevent the temperature from rising due to heat generated by energization and heat penetration from the outside of the equipment and vaporizing in the superconducting cable, freeze it in advance. It is introduced after cooling with a machine and making it supercooled.

  Conventionally, a refrigerator is mainly used when a liquid refrigerant is brought into a supercooled state below a saturation temperature. Stirling refrigerators, GM (Gifford McMahon) refrigerators, pulse tube refrigerators, Brayton refrigerators, and the like have been developed as refrigerators for cooling liquid refrigerant to a supercooled state.

  For example, Patent Document 1 below discloses a cooling method using a refrigerator, and Patent Document 2 below discloses a cooling method using a Brayton refrigerator. However, these refrigerators have a small COP (Coefficient Of Performance) value representing the energy consumption efficiency of the refrigerator when cooling the liquid refrigerant to a supercooled state, and require a lot of energy to cool the liquid refrigerant. There is. For example, according to Non-Patent Document 2 below, the value of COP when a Brayton refrigerator is used is generally about 0.08.

  Non-Patent Document 3 listed below lists a value of 0.10 as a COP target value, and it is reported that this target value is achieved in an experimental machine of a Brayton refrigerator. However, as disclosed in Non-Patent Document 4 below, when the Brayton refrigerator is used as a commercial machine, priority is given to the suppression of the device size and cost, so the COP value remains at 0.08. . Therefore, improvement of the value of COP is examined by the cooling method which does not use a refrigerator.

As a method for cooling a superconducting cable that does not use a refrigerator, for example, the following Non-Patent Document 1 discloses a cooling system using a sub-cooler unit (or called an N ₂ diffusion system). According to this cooling system, by using a heat exchanger as a subcooler, liquid nitrogen in a supercooled state is produced by exchanging heat with saturated liquid nitrogen of about 65 to 70 K, and then the supercooled state The superconducting cable is cooled by liquid nitrogen. However, in this system, an exhaust pump is connected to the subcooler, and the saturated liquid nitrogen vaporized by heat exchange is released into the atmosphere. Since the saturated liquid nitrogen is consumed due to the emission to the atmosphere, there is a problem that it is necessary to periodically replenish the saturated liquid nitrogen using a transportation means such as a lorry.

JP, 2006-186893, A Japanese Patent Laying-Open No. 2015-187525

“Superconducting web21”, International Superconducting Industrial Technology Research Center, July issue, p. 17-21, (2014) Osaki Shinsuke et al., “Taiyo Nippon Sanso Technical Report”, Taiyo Nippon Sanso Co., Ltd. 33, p. 6, (2014) “Superconducting web21”, International Superconducting Industrial Technology Research Center, July issue, p. 1, (2014) Gas Review Co., Ltd., “Gas Review”, No. 854, p. 5, (2016)

  The present invention has been made in view of the above-mentioned problems, and its purpose is to achieve energy consumption efficiency exceeding that of a conventional superconducting cable cooling device using a refrigerator, and to reduce refrigerant consumption by diffusion into the atmosphere. It is an object of the present invention to provide a superconducting cable cooling device and a superconducting cable cooling method using the same.

The conventional problems are solved by the invention described below.
That is, the cooling device for a superconducting cable according to the present invention is a cooling device for a superconducting cable that cools the superconducting cable in order to solve the above-described problem, and cools the superconducting cable with a supercooled liquid refrigerant. Heat exchange between the superconducting cable cooling unit, a first supply unit that supplies the liquid refrigerant for cooling the liquid refrigerant to a supercooled state by heat exchange, and the superconducting cable cooling unit. A second supply unit that supplies the second refrigerant for cooling to the first supply unit, the first supply unit storing the first refrigerant in a liquid state, The first refrigerant in a liquid state cools the liquid refrigerant to a supercooled state by heat exchange with the liquid refrigerant, and compresses the first refrigerant in a gas state thereby A compression section, a first heat exchanger that exchanges heat between the first refrigerant and the second refrigerant in the gaseous state, and cools and liquefies the first refrigerant, the storage section, the compression section, and the first And a circulation path for connecting the first heat exchanger and circulating the first refrigerant.

  According to the above configuration, the cooling device for a superconducting cable of the present invention cools the superconducting cable provided in the superconducting cable cooling unit using the supercooled liquid refrigerant in the superconducting cable cooling unit. It is. Here, as described above, the present invention does not use a conventional refrigerator such as a Brayton refrigerator as a means for cooling the liquid refrigerant to a supercooled state. The present invention cools the liquid refrigerant to a supercooled state using the first refrigerant circulating in the first supply unit. Therefore, the COP value can be improved as compared with a conventional superconducting cable cooling device using a refrigerator.

  Further, when the first refrigerant is circulated in the first supply unit, the present invention operates the respective components as described below, thereby suppressing significant consumption of the first refrigerant. That is, first, the first refrigerant in the liquid state supplied from the storage unit becomes a gaseous state after being exchanged with the liquid refrigerant and is sent to the compression unit. In the compression unit, the boiling point of the gaseous first refrigerant is increased by compressing the gaseous first refrigerant. In the first heat exchanger, the compressed first refrigerant in the gaseous state is cooled by heat exchange with the second refrigerant supplied from the second supply unit, and becomes a liquid state. Then, the 1st refrigerant | coolant of a liquid state is sent to a storage part, and is stored in the said storage part. In this way, the present invention allows the first refrigerant used for cooling the liquid refrigerant to circulate in the first supply unit without being discharged out of the system, and operates again so that it can be reused for cooling the liquid refrigerant. Therefore, consumption of the first refrigerant can be greatly suppressed.

  Moreover, in the said structure, in order to make the 1st refrigerant | coolant after use (namely, the 1st refrigerant | coolant of the gas state compressed by the compression part) available for cooling of a liquid refrigerant again, a 2nd supply unit is provided. This 2nd supply unit is a unit which supplies the 2nd refrigerant | coolant which enables cooling by heat exchange with the 1st refrigerant | coolant after use to a 1st heat exchanger. Therefore, for example, when liquefied natural gas that has not been conventionally used for cold energy is used as the second refrigerant, the cold energy can be used.

  The said structure WHEREIN: The said 1st supply unit is provided with the 2nd heat exchanger between the said storage part and the said superconducting cable cooling unit, and the said 2nd heat exchanger is supplied from the said storage part. Heat exchange is performed between the first refrigerant in the liquid state and the first refrigerant that is in the gaseous state by heat exchange with the liquid refrigerant, and the first refrigerant in the liquid state after the heat exchange is further transferred to the superconducting cable cooling unit. It is preferable to supply.

  According to the above configuration, by providing the second heat exchanger between the storage unit and the superconducting cable cooling unit, the first liquid state supplied from the storage unit as compared with before heat exchange is provided. Since the refrigerant is cooled, the first refrigerant in the liquid state is supplied to the superconducting cable cooling unit at a lower temperature. Thereby, since the cooling energy which can be used for the cooling of the said liquid state increases, the value of COP improves.

  Furthermore, in the said structure, it is preferable to use what consists of at least any one of nitrogen, oxygen, or argon as said liquid refrigerant and said 1st refrigerant | coolant.

  Moreover, in the said structure, the refrigerant | coolant whose temperature is lower than the boiling point of the said 1st refrigerant | coolant of the said gaseous state which raised the boiling point by compression can be used. Thereby, the 1st refrigerant | coolant of the gas state compressed by heat exchange with the 2nd refrigerant | coolant in a 1st heat exchanger can be cooled to the temperature lower than the boiling point, and can be made into a liquid state. As a result, the first refrigerant is made reusable for cooling the liquid refrigerant.

  In the above configuration, it is preferable that the second refrigerant uses at least one of liquefied natural gas, liquefied methane, liquefied nitrogen, liquefied oxygen, or liquefied argon.

  The superconducting cable cooling method of the present invention is a superconducting cable cooling method using a superconducting cable cooling device in order to solve the above-mentioned problem, and the superconducting cable cooling device supercools the superconducting cable. A superconducting cable cooling unit that cools with the liquid refrigerant in a state; a first supply unit that supplies the liquid state first refrigerant to the superconducting cable cooling unit for cooling the liquid refrigerant to a supercooled state by heat exchange; A second supply unit that supplies the second refrigerant for cooling the first refrigerant by heat exchange to the first supply unit, and the liquid stored in the first supply unit The first refrigerant in the state is supplied to the superconducting cable cooling unit, and the first refrigerant in the liquid state is used to heat the liquid refrigerant. In other words, the liquid refrigerant is cooled to a supercooled state, the first refrigerant that is in a gaseous state by heat exchange with the liquid refrigerant is compressed, and heat exchange is performed between the first refrigerant and the second refrigerant in the gaseous state. The first refrigerant is circulated in the first supply unit by cooling the first refrigerant to a liquid state and storing the first refrigerant in the liquid state in the first supply unit. It is something to be made.

  According to the above method, the cooling method of the present invention cools the superconducting cable using the supercooled liquid refrigerant in the superconducting cable cooling unit. Here, the present invention does not use a conventional refrigerator such as a Brayton refrigerator as the means for cooling the liquid refrigerant to a supercooled state as described above. The present invention cools the liquid refrigerant to a supercooled state using the first refrigerant circulating in the first supply unit. Therefore, the COP value can be improved as compared with a conventional superconducting cable cooling device using a refrigerator.

  Further, when the first refrigerant is circulated in the first supply unit, the present invention suppresses significant consumption of the first refrigerant by the method described below. That is, first, the stored first refrigerant in the liquid state is supplied, and after exchanging heat with the liquid refrigerant, the first refrigerant discharged from the superconducting cable cooling unit in a gaseous state is compressed to be in a gaseous state The boiling point of the first refrigerant is increased. The compressed first refrigerant in a gaseous state is cooled and liquefied by heat exchange with the second refrigerant supplied from the second supply unit. Thereafter, the first refrigerant in a liquid state is stored in the first supply unit. In this way, the present invention allows the first refrigerant used for cooling the liquid refrigerant to circulate in the first supply unit without being discharged out of the system, and operates again so that it can be reused for cooling the liquid refrigerant. Therefore, consumption of the first refrigerant can be greatly suppressed.

  In the method, the second refrigerant is used from the second supply unit so that the first refrigerant after use (that is, the compressed first refrigerant in the gaseous state) can be used again for cooling the liquid refrigerant. Supply. That is, a 2nd refrigerant | coolant is supplied to a 1st supply unit, The said 1st refrigerant | coolant is again made into a liquid state by heat exchange with the said 2nd refrigerant | coolant and the 1st refrigerant | coolant after use. Thereby, for example, when liquefied natural gas that has not been conventionally used for cold energy is used as the second refrigerant, the cold energy can be used.

  In the method, after exchanging heat between the first refrigerant in a liquid state immediately before being supplied to the superconducting cable cooling unit and the first refrigerant in a gas state due to heat exchange with the liquid refrigerant, It is preferable to supply the first refrigerant in a liquid state to the superconducting cable cooling unit.

  According to the method, by exchanging heat between the first refrigerant in the liquid state immediately before being supplied to the superconducting cable cooling unit and the first refrigerant in a gaseous state by heat exchange with the liquid refrigerant. Since the first refrigerant in the liquid state is cooled compared to before heat exchange, the first refrigerant in the liquid state is supplied to the superconducting cable cooling unit at a lower temperature. Thereby, since the cooling energy which can be used for the cooling of the said liquid state increases, the value of COP improves.

  Further, in the method, it is preferable to use a liquid refrigerant and the first refrigerant made of at least one of nitrogen, oxygen, and argon.

  Moreover, in the said method, the refrigerant | coolant whose temperature is lower than the boiling point of the said 1st refrigerant | coolant of the gaseous state which raised the boiling point by compression can be used. Thereby, the 1st refrigerant | coolant of the gas state compressed by heat exchange with a 2nd refrigerant | coolant can be cooled to the temperature lower than the boiling point, and can be made into a liquid state. As a result, the first refrigerant is made reusable for cooling the liquid refrigerant.

  In the method, it is preferable that the second refrigerant is at least one of liquefied natural gas, liquefied methane, liquefied nitrogen, liquefied oxygen, or liquefied argon.

The present invention has the following effects by the means described above.
The cooling device for a superconducting cable of the present invention includes a first supply unit and a second supply unit. Therefore, the superconducting cable can be cooled without using a refrigerator or the like, and the first refrigerant is the first refrigerant. Since the inside of the supply unit can be circulated, the energy consumption efficiency that exceeds the cooling device for a superconducting cable using a conventional refrigerator is achieved, and the effect of preventing the refrigerant consumption due to the diffusion to the atmosphere is achieved. In addition, for example, when liquefied natural gas, in which cold energy is conventionally discarded, is used as the second refrigerant, energy consumption efficiency can be further improved.

It is a schematic explanatory drawing showing the cooling device for superconducting cables which concerns on Embodiment 1 of this invention. It is a schematic explanatory drawing showing the cooling device for superconducting cables which concerns on Embodiment 2 of this invention.

(Embodiment 1)
<Cooling device for superconducting cable>
The superconducting cable cooling apparatus according to the first embodiment will be described below with reference to FIG. FIG. 1 is a schematic explanatory diagram showing a superconducting cable cooling device according to the first embodiment.

  As shown in FIG. 1, the superconducting cable cooling device 1 according to the first embodiment includes a superconducting cable cooling unit 10 that cools the superconducting cable 14, and a first supply that supplies the first refrigerant to the superconducting cable cooling unit 10. At least a unit 20 and a second supply unit 30 for supplying a second refrigerant to the first supply unit 20 are provided.

  The superconducting cable cooling unit 10 includes at least a liquid refrigerant circulation path 11, a supercooler 12, a liquid feed pump 13, and a superconducting cable 14, and cools the superconducting cable.

  The liquid refrigerant circulation path 11 connects the supercooler 12, the liquid feed pump 13, and the superconducting cable 14, and enables the liquid refrigerant to circulate in the superconducting cable cooling unit 10. The liquid refrigerant circulation path 11 preferably has a heat insulating property. Thereby, it is possible to reduce the temperature rise of the liquid refrigerant circulating inside the liquid refrigerant circulation path 11 due to the intrusion heat from the outside of the liquid refrigerant circulation path 11.

  The subcooler 12 includes a main body portion 12a and a throw-in heat exchanger 12b, and the throw-in heat exchanger 12b is installed inside the main body 12a.

  The main body 12 a of the subcooler 12 is connected to a first refrigerant circulation path (circulation path) 21, and stores the first refrigerant in a liquid state supplied from the first refrigerant circulation path 21 therein. In addition, the main-body part 12a has what has heat insulation. Thereby, it is possible to reduce an increase in the temperature of the first refrigerant in the liquid state stored inside the main body 12a due to intrusion heat from the outside of the main body 12a.

  The throw-in type heat exchanger 12b is accommodated in the main body 12a soaked in the liquid first refrigerant. The throwing-type heat exchanger 12b performs heat exchange between the liquid first refrigerant stored in the main body 12a and the liquid refrigerant flowing inside the throwing-type heat exchanger 12b. Thereby, the liquid refrigerant can be cooled to a supercooled state. In addition, the liquid refrigerant flowing through the throw-in heat exchanger 12b refers to the liquid refrigerant that has finished cooling the superconducting cable 14 in more detail. Moreover, it does not specifically limit as a kind of throw-in type heat exchanger 12b, A conventionally well-known thing can be used.

  The liquid refrigerant is cooled by heat exchange with the first refrigerant in the liquid state stored in the main body 12a, and becomes a supercooled state. Therefore, since a refrigerator is not used for cooling the liquid refrigerant, the COP value can be improved. In this specification, “supercooling” means cooling to a temperature lower than the saturation temperature of the liquid refrigerant, and “supercooled state” means that the liquid refrigerant is maintained in such a supercooled state. Means that Further, the saturation temperature means a temperature at which the liquid refrigerant boils (for example, about −196 ° C. in the case of liquid nitrogen under atmospheric pressure). “COP” means energy consumption efficiency (cooling capacity per unit consumption energy) for cooling the liquid refrigerant by the first supply unit, and (COP) = (liquid refrigerant by the first supply unit (Cooling capacity to cool (kW)) / (total energy required to drive the first supply unit (kW)).

  The liquid feed pump 13 is provided on the downstream side of the supercooler 12 and feeds and circulates the liquid refrigerant in the liquid refrigerant circulation path 11. The liquid feed pump 13 may be provided on the downstream side of the superconducting cable 14 and between the superconducting cable 14 and the supercooler 12. Moreover, it does not specifically limit as a kind of liquid feeding pump 13, A conventionally well-known thing can be used.

  The superconducting cable 14 is provided on the downstream side of the liquid feed pump 13. The superconducting cable 14 is a cable that uses a high-temperature superconducting wire. For example, the superconducting cable 14 includes at least a cable core having a high-temperature superconducting layer and a heat insulating tube that accommodates the cable core therein. A liquid refrigerant circulation path 11 is connected to the heat insulation pipe so that the liquid refrigerant can flow, thereby allowing the cable core accommodated in the heat insulation pipe to be cooled.

  The liquid refrigerant is not particularly limited, and examples thereof include liquid nitrogen, liquid oxygen, and liquid argon. Among these, liquid nitrogen is preferable in the present embodiment.

  The first supply unit 20 mainly includes a first refrigerant circulation path (circulation path) 21, a first refrigerant storage tank (storage section) 23, a compressor (compression section) 26, and a first heat exchanger 27, and is a superconducting cable cooling unit. 10 is a unit that supplies the first refrigerant in a liquid state to the unit 10. The first supply unit 20 further includes a discharge path 22, a heater 24, a vacuum pump 25, a flow rate adjustment valve 28 and a pressure reducing valve 29.

  The first refrigerant storage tank 23 stores the first refrigerant in a liquid state. Moreover, what vaporized the said 1st refrigerant | coolant of the said liquid state may be stored in the 1st refrigerant | coolant storage tank 23. FIG. In addition, what has the heat insulation is preferable for the 1st refrigerant | coolant storage tank 23. FIG. Thereby, it is possible to reduce the temperature rise of the first refrigerant in the liquid state stored inside the first refrigerant storage tank 23 due to intrusion heat from the outside of the first refrigerant storage tank 23, and the liquefied gas is vaporized. Generation | occurrence | production of evaporation gas (BOG: Boil Off Gas) can be suppressed. Moreover, it does not specifically limit as said 1st refrigerant | coolant, For example, what consists of at least any one of nitrogen, oxygen, or argon is mentioned.

  The first refrigerant circulation path 21 is connected to the first refrigerant storage tank 23, the flow control valve 28, the supercooler 12, the heater 24, the vacuum pump 25, the compressor 26, the first heat exchanger 27, and the pressure reducing valve 29. The first refrigerant can circulate in the first supply unit 20. The first refrigerant circulation path 21 preferably has a heat insulating property. Thereby, it is possible to reduce the temperature rise of the first refrigerant circulating inside the first refrigerant circulation path 21 due to the intrusion heat from the outside of the first refrigerant circulation path 21.

  The discharge path 22 is connected to the first refrigerant storage tank 23, and communicates with the vacuum pump 25 and the compressor 26 in the first refrigerant circulation path 21 via the first heat exchanger 27. ing. As a result, the discharge path 22 supplies the first refrigerant in the gaseous state existing in the first refrigerant storage tank 23 to the first heat exchanger 27, passes through the first heat exchanger 27, and then enters the front stage of the compressor 26. Makes it possible to supply. The discharge path 22 preferably has a heat insulating property. Thereby, it is possible to reduce the temperature rise of the said 1st refrigerant | coolant of the said gas state which distribute | circulates the inside of the discharge path 22 by the heat | fever intrusion from the discharge path 22 exterior.

  The flow rate adjusting valve 28 is provided between the first refrigerant storage tank 23 and the subcooler 12, and can adjust the flow rate of the first refrigerant in the liquid state supplied from the first refrigerant storage tank 23. Thereby, it becomes possible to supply the 1st refrigerant | coolant of the quantity according to the cooling energy required for the main-body part 12a. Moreover, it does not specifically limit as a kind of the flow control valve 28, A conventionally well-known thing can be used.

  The warmer 24 is provided on the downstream side of the supercooler 12, and can raise the temperature of the first refrigerant in a gas state discharged from the supercooler 12. As a result, the suction temperature of the vacuum pump 25 is close to room temperature, and a general-purpose vacuum pump 25 can be selected. Moreover, it does not specifically limit as a kind of the warmer 24, A conventionally well-known thing can be used.

  The vacuum pump 25 is provided on the downstream side of the warmer 24, and can discharge the first refrigerant in the gas state existing in the main body 12 a of the supercooler 12 and send it to the compressor 26 by pressure. Moreover, it does not specifically limit as a kind of vacuum pump 25, A conventionally well-known thing can be used.

  The compressor 26 is provided on the downstream side of the vacuum pump 25 and can compress the first refrigerant in the gaseous state. The boiling point of the first refrigerant in the gaseous state rises due to compression compared to before compression. Therefore, the first refrigerant in the gaseous state can be liquefied at a higher temperature than before compression. Moreover, it does not specifically limit as a kind of the compressor 26, A conventionally well-known thing can be used.

  The first heat exchanger 27 is provided on the downstream side of the compressor 26, and the first refrigerant in the gaseous state compressed by the compressor 26 and the second refrigerant supplied from the second refrigerant storage tank 32. Heat exchange can be performed. Thereby, the first refrigerant in the gaseous state is cooled and becomes a liquid state. The first heat exchanger 27 is connected to a second refrigerant discharge path 35 (details will be described later) for discharging the second refrigerant used for heat exchange with the first refrigerant in the gaseous state. ing. Further, the discharge path 22 is also connected to the first heat exchanger 27. The discharge path 22 supplies the first heat exchanger 27 with the vaporized liquid first refrigerant stored in the first refrigerant storage tank 23. Then, the first heat exchanger 27 exchanges heat between the vaporized first refrigerant and the gaseous first refrigerant compressed by the compressor 26. Moreover, it does not specifically limit as a kind of 1st heat exchanger 27, A conventionally well-known thing can be used.

  The pressure reducing valve 29 is provided between the first heat exchanger 27 and the first refrigerant storage tank 23, and can reduce the pressure of the first refrigerant in the liquid state discharged from the first heat exchanger 27. As a result, the section in the first refrigerant circulation path 21 between the compressor 26 and the pressure reducing valve 29 can be set to a pressure higher than that in the first refrigerant storage tank 23. Moreover, it does not specifically limit as a kind of pressure reducing valve 29, A conventionally well-known thing can be used.

  The second supply unit 30 includes at least a second refrigerant supply path 31, a second refrigerant storage tank 32, an evaporator 33, a branch path 34, and a second refrigerant discharge path 35, and supplies the second refrigerant to the first supply unit 20. It is.

  The second refrigerant storage tank 32 stores liquefied gas as the second refrigerant. The second refrigerant storage tank 32 preferably has a heat insulating property. Thereby, it is possible to reduce the temperature rise of the liquefied gas stored inside the second refrigerant storage tank 32 due to the intrusion heat from the outside of the second refrigerant storage tank 32, and the liquefied gas is evaporated to evaporate gas (BOG: Boil Off Gas) can be suppressed.

  It does not specifically limit as liquefied gas, For example, liquefied natural gas (boiling point -162 degreeC (atmospheric pressure 101.325kPa)), liquefied methane (boiling point -161.49 degreeC (atmospheric pressure 101.325kPa)), liquefied nitrogen (boiling point) -195.8 ° C. (atmospheric pressure 101.325 kPa)), liquefied oxygen (boiling point −182.96 ° C. (atmospheric pressure 101.325 kPa)), or liquefied argon (boiling point −185.8 ° C. (atmospheric pressure 101.325 kPa)) At least one of them. Of these, liquefied natural gas is preferred from the viewpoint of recovery of cold energy. In natural gas, much of the cold energy generated with the phase change from liquid to gas is discarded. For this reason, by applying liquefied natural gas to the second refrigerant of the present embodiment, it is possible to use waste cold energy for cooling the first refrigerant. Natural gas has various compositions such as the ratio of nitrogen content depending on the place of production. In the present invention, the effect can be achieved regardless of the difference in the place of production.

  The second refrigerant supply path 31 connects the second refrigerant storage tank 32 and the first heat exchanger 27, and allows the second refrigerant to be supplied from the second refrigerant storage tank 32 to the first heat exchanger 27. In addition, the 2nd refrigerant | coolant supply path 31 has what has heat insulation. Thereby, it is possible to reduce the temperature rise of the said 2nd refrigerant | coolant of the liquid state which flows through the 2nd refrigerant | coolant supply path 31 by the penetration | invasion heat from the 2nd refrigerant | coolant supply path 31 exterior.

  The branch path 34 branches from the second refrigerant supply path 31 and can supply at least a part of the second refrigerant stored in the second refrigerant storage tank 32 to the evaporator 33.

  The evaporator 33 is provided in the middle of the branch path 34, and can evaporate the 2nd refrigerant | coolant supplied and can be made into a gaseous state. Thereby, for example, when liquefied natural gas is used as the second refrigerant, the liquefied natural gas is vaporized by the first heat exchanger 27 and the evaporator 33 in the second refrigerant supply unit 30, so that It is discharged from the second refrigerant supply unit 30. For this reason, the discharged natural gas can be used for a desired application. In addition, it does not specifically limit as a kind of evaporator 33, A conventionally well-known thing can be used.

  The second refrigerant discharge path 35 communicates and connects the first heat exchanger 27 and the downstream side of the evaporator 33 in the branch path 34. By providing the second refrigerant discharge path 35, the second refrigerant used in the first heat exchanger 27 and in a gaseous state can be discharged from the second refrigerant supply unit 30.

<Cooling method of superconducting cable>
Next, a superconducting cable cooling method using the superconducting cable cooling apparatus 1 according to the first embodiment will be described with reference to FIG.

The superconducting cable 14 is cooled in the superconducting cable cooling unit 10 as follows. That is, first, in the supercooler 12, the liquid refrigerant is cooled to a supercooled state by heat exchange with the liquid first refrigerant supplied from the first supply unit 20.
The liquid refrigerant cooled to the supercooled state by the supercooler 12 is pumped and circulated in the liquid refrigerant circulation path 11 by the liquid feed pump 13. Since the superconducting cable 14 is connected downstream of the liquid feed pump 13 in the liquid refrigerant circulation path 11, the superconducting cable 14 is thereby cooled. When liquid nitrogen is used as the liquid refrigerant, the flow rate of liquid nitrogen flowing in the liquid refrigerant circulation path 11 is not particularly limited, but is usually in the range of 30 L / min to 100 L / min.

  Next, the supply of the first refrigerant used for cooling the liquid refrigerant to the superconducting cable cooling unit 10 will be described. The supply of the first refrigerant is performed in the first supply unit 20 as follows. That is, first, the first refrigerant in the liquid state supplied via the flow control valve 28 is introduced into the subcooler 12 decompressed by the vacuum pump 25, and the temperature is lowered accordingly.

  On the other hand, by operating the vacuum pump 25 provided on the downstream side of the supercooler 12, the section between the flow rate adjustment valve 28 and the vacuum pump 25 in the first refrigerant circulation path 21 is more than the first refrigerant storage tank 23. Use low pressure. Thereby, the boiling point of the 1st refrigerant | coolant in the said area falls.

  The pressure in the main body 12a is not particularly limited. Here, the 1st refrigerant | coolant currently stored in the main-body part 12a exists in a gas-liquid equilibrium state, and the temperature of a 1st refrigerant | coolant is also decided uniquely by the pressure in the main-body part 12a. Therefore, by adjusting the pressure in the main body 12a so that the temperature of the first refrigerant in the main body 12a is lower than the temperature of the liquid refrigerant, the temperature of the superconducting cable is less than the temperature at which the superconducting cable can exert its performance. Can be cooled to. For example, when nitrogen is used as the first refrigerant, by setting the pressure in the main body 12a to less than −78 kPaG, the temperature of the nitrogen is made lower than the temperature of the liquid refrigerant, and as a result, the liquid refrigerant is −205 ° C. It becomes possible to cool it.

  Subsequently, in the supercooler 12, the used first refrigerant in the liquid state is vaporized by heat exchange with the liquid refrigerant, and becomes a first refrigerant in the gaseous state and heated through the first refrigerant circulation path 21. Supplied to the vessel 24. Then, the first refrigerant in the gaseous state is heated in the heater 24.

  The first refrigerant in the gaseous state heated by the heater 24 is supplied to the compressor 26 via the vacuum pump 25. Since the first refrigerant is preheated by the heater 24, the suction temperature of the vacuum pump is close to room temperature, and a general-purpose vacuum pump can be selected as the vacuum pump 25. And the 1st refrigerant | coolant of a gaseous state is compressed in the said compressor 26. FIG.

  Here, the pressure of the first refrigerant in the gaseous state after compression by the compressor 26 is such that the boiling point of the first refrigerant in the gaseous state after compression is higher than the temperature of the second refrigerant supplied to the first heat exchanger 27. It is necessary to set the pressure higher than the increasing pressure. Since the boiling point is higher than the temperature of the second refrigerant, the first refrigerant in the gaseous state can be liquefied in the first heat exchanger 27. The pressure after compression by the compressor 26 varies depending on the type of the first refrigerant, the type of the second refrigerant, and the pressure condition. For example, when nitrogen is used as the first refrigerant, liquefied natural gas is used as the second refrigerant, and the liquefied natural gas pressure in the second refrigerant storage tank 32 is set to 0.03 MPaG, the first heat exchanger 27 is supplied. Since the temperature of the liquefied natural gas is about −160 ° C., the nitrogen can be liquefied by the first heat exchanger 27 by setting the compressed nitrogen pressure to 2 MPaG or more. On the other hand, in order to reduce the power consumption of the compressor 26, the pressure of the first refrigerant after compression is preferably as low as possible. Therefore, from such a viewpoint, in the case of the above conditions, it is preferable that the pressure of nitrogen after compression is 2.3 to 2.5 MPaG.

  Next, the compressed first refrigerant in the gaseous state is supplied to the first heat exchanger 27. Thereafter, the compressed first refrigerant in the gaseous state is cooled in the first heat exchanger 27 by heat exchange with the second refrigerant supplied from the second supply unit 30. Thereby, the first refrigerant is liquefied.

  The first refrigerant that has undergone heat exchange in the first heat exchanger 27 and is in a liquid state is depressurized by the pressure reducing valve 29 and then returned to the first refrigerant storage tank 23.

  As described above, even after the first supply unit 20 of the present embodiment is used for cooling the liquid refrigerant, the first refrigerant is circulated without being discharged out of the system, thereby greatly consuming the first refrigerant. Can be suppressed. In addition, since the liquid refrigerant can be cooled in a supercooled state without using a refrigerator, the COP value can be improved.

  In the first supply unit 20, the vaporized first refrigerant stored in the first refrigerant storage tank 23 is also vaporized first refrigerant after being compressed in the first heat exchanger 27. It is used for heat exchange with. More specifically, the vaporized first refrigerant stored in the first refrigerant storage tank 23 is discharged from the discharge path 22 and supplied to the first heat exchanger 27. In the first heat exchanger 27, the vaporized first refrigerant is used for heat exchange with the compressed first refrigerant in the gaseous state. The temperature of the vaporized first refrigerant after the heat exchange is increased.

  Further, the vaporized first refrigerant after heat exchange joins the first refrigerant circulation path 21 via the discharge path 22. The joining position of the vaporized first refrigerant to the first refrigerant circulation path 21 is between the vacuum pump 25 and the compressor 26. Thereafter, the compressor 26 is compressed together with the first refrigerant in the gaseous state flowing from the heater 24 and is reused for heat exchange in the first heat exchanger 27 again. As described above, the vaporized first refrigerant generated in the first refrigerant storage tank 23 is also used for heat exchange in the first heat exchanger 27, so that the energy consumption efficiency can be further improved.

  Next, the supply to the 1st supply unit 20 of the 2nd refrigerant | coolant used for cooling of the 1st refrigerant | coolant of a gas state is demonstrated. The supply of the second refrigerant is performed in the second supply unit 30. More specifically, the second refrigerant (liquid state) stored in the second refrigerant storage tank 32 is supplied to the first refrigerant via the second refrigerant supply path 31. This is performed by supplying the heat exchanger 27. After the heat exchange in the first heat exchanger 27, the second refrigerant is in a gaseous state and is discharged from the second refrigerant discharge path 35 of the first heat exchanger 27.

In addition, the 2nd refrigerant | coolant which shunts from the 2nd refrigerant | coolant supply path 31 and flows through the branch path 34 will be in a gaseous state in the evaporator 33 after that, and can be used for another use. Moreover, the second refrigerant in the gaseous state used in the first heat exchanger 27 joins the branch path 34. For this reason, for example, when liquefied natural gas is used for the second refrigerant, it is possible to take out the natural gas in a gaseous state from the branch path 34, so that it can be used for a desired application such as fuel or raw material. The flow rate of the second refrigerant flowing in the second refrigerant supply path 31 is determined by the type and flow rate of the first refrigerant and the type and pressure of the second refrigerant, and is not particularly limited. It is preferable that the amount of the first refrigerant after compression in the container 27 can be liquefied. For example, using nitrogen as the first refrigerant and liquefied natural gas as the second refrigerant, the flow rate of the compressed first refrigerant is 104 Nm ³ / h, and the liquefied natural gas pressure in the second refrigerant storage tank 32 is 0.03 MPaG. In this case, the flow rate of the liquefied natural gas flowing in the second refrigerant supply path 31 is 38 kg / h.

(Embodiment 2)
<Cooling device for superconducting cable>
A superconducting cable cooling apparatus according to the second embodiment will be described with reference to FIG. FIG. 2 is a schematic explanatory diagram showing the superconducting cable cooling device according to the second embodiment. In addition, about the component which has a function similar to the cooling device 1 for superconducting cables of the said Embodiment 1, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.

  As shown in FIG. 2, the superconducting cable cooling device 2 according to the second embodiment includes a second heat exchanger 210 in the first supply unit 200 as compared with the superconducting cable cooling device 1 according to the first embodiment. The point to prepare is different.

  Specifically, the first supply unit 200 includes a second heat exchanger 210 between the first refrigerant storage tank 23 and the flow rate control valve 28 in addition to the configuration of the first supply unit 20 of the first embodiment.

  The second heat exchanger 210 can exchange heat between the liquid first refrigerant supplied from the first refrigerant storage tank 23 and the gas first refrigerant discharged from the subcooler 12. As a result, the first refrigerant in the liquid state is cooled, and the temperature of the first refrigerant in the gas state rises, so that the first refrigerant in the liquid state exceeds the temperature at a lower temperature as compared with the first embodiment. The first refrigerant in the gaseous state is supplied to the cooler 12 and is supplied to the warmer 24 at a higher temperature. Moreover, it does not specifically limit as a kind of 2nd heat exchanger 210, A conventionally well-known thing can be used.

<Cooling method of superconducting cable>
Next, a superconducting cable cooling method by the superconducting cable cooling apparatus 2 according to the second embodiment will be described below with reference to FIG.

  Superconducting cable cooling unit 10 cools superconducting cable 14 by the same method as in the first embodiment. The second supply unit 30 supplies the second refrigerant to the first supply unit 200 by the same method as in the first embodiment.

  Supply of the first refrigerant to the superconducting cable cooling unit 10 in the first supply unit 200 is performed as follows. That is, in addition to the configuration of the first supply unit 20 of the first embodiment, a second heat exchanger 210 is provided between the first refrigerant storage tank 23 and the flow rate adjustment valve 28.

  The first refrigerant in the liquid state supplied from the first refrigerant storage tank 23 via the first refrigerant circulation path 21 is first, in the second heat exchanger 210, the first refrigerant in the gaseous state discharged from the supercooler 12. Heat exchanged. The temperature of the liquid first refrigerant supplied from the first refrigerant storage tank 23 is higher than the temperature of the gas first refrigerant discharged from the supercooler 12. Therefore, in the heat exchange, the first refrigerant in the liquid state is cooled, and the first refrigerant in the gas state is heated. This makes it possible to supply the first refrigerant in the liquid state to the subcooler 12 in a state where the temperature is lower than that in the first embodiment in which the second heat exchanger 210 is not installed, Further, the first refrigerant in the gaseous state can be supplied to the heater 24 at a high temperature.

  In the subcooler 12, as in the case of the first embodiment, the first refrigerant is introduced into the subcooler 12 whose pressure has been reduced by the vacuum pump 25, so that the pressure decreases, and the temperature increases accordingly. descend. The first refrigerant partially vaporizes as the pressure decreases. For this reason, by supplying the first refrigerant in the liquid state at a lower temperature to the subcooler 12, the cooling energy required for cooling the first refrigerant in the liquid state is reduced, and the cooling energy that can be used for cooling the liquid refrigerant is reduced. Can be increased.

  Further, in the heater 24, as in the case of the first embodiment, the temperature of the first refrigerant in the gaseous state discharged from the supercooler 12 is increased, and the first refrigerant in the gaseous state is brought to near normal temperature. Thus, a general-purpose vacuum pump 25 can be selected. For this reason, by supplying the first refrigerant in the gaseous state to the warmer 24 at a higher temperature, the cooling energy discarded in the warmer 24 can be reduced.

  As described above, in the second embodiment, in the first supply unit 200, the second heat exchanger 210 is provided between the first refrigerant storage tank 23 and the flow rate control valve 28, thereby comparing with the first embodiment. Thus, the COP value can be further improved.

  Hereinafter, preferred embodiments of the present invention will be described in detail by way of example. However, the composition, pressure conditions, physical property estimation methods, and the like described in the following examples do not limit the scope of the present invention to these unless otherwise specified.

Example 1
In Example 1, a process simulation was performed using the configuration of the superconducting cable cooling device 1 shown in FIG. At this time, liquid nitrogen was used as the liquid refrigerant, nitrogen was used as the first refrigerant, and liquefied natural gas was used as the second refrigerant. The composition of liquefied natural gas was as follows.
CH _4: 88.75% by volume
C ₂ H _6: 7.19 vol%
C ₃ H _8: 2.88 vol%
C ₄ H ₁₀ : 1.12% by volume
C ₅ H ₁₂ : 0.05% by volume
N ₂ : 0.01% by volume

<Simulation conditions>
The simulation conditions were as follows.
Temperature and pressure of the liquid refrigerant supplied from the supercooler 12 to the superconducting cable 14: −205 ° C., 300 kPaG
Pressure inside first refrigerant storage tank 23: 200 kPaG
Pressure inside main body 12a: −80 kPaG
Pressure of the first refrigerant in the gaseous state compressed by the compressor 26: 2500 kPaG
Temperature of liquefied natural gas supplied to the first heat exchanger 27: −157 ° C.
Pressure inside second refrigerant storage tank: 30 kPaG
Ability to cool liquid refrigerant by first supply unit: 5 kW

  The Peng-Robinson equation of state was used as a method for estimating the physical properties of nitrogen and natural gas. Since the boiling point of nitrogen at a pressure of 2500 kPaG is −155 ° C., liquefaction of nitrogen with liquefied natural gas is possible.

  As a result of the above simulation, the flow rate of the natural gas supplied from the second supply unit 30 to the first supply unit 20 was 47.3 kg / h. In this process, the cold energy of liquefied natural gas, which was conventionally discarded in seawater, was only used for cooling liquid nitrogen, so the natural gas after recovering the cold energy is used for the desired application. Is possible. In Japan, dozens of liquefied natural gas satellite bases vaporize liquefied natural gas at a rate of several hundred kg / h, so the amount of natural gas used is covered by the amount used at the satellite base. It is possible.

  As a result of the above simulation, the power required for the first supply unit 20 was 10.4 kW for the vacuum pump 25 and 38.9 kW for the compressor 26. Therefore, the value of COP was 5 kW / (10.4 kW + 38.9 kW) = 0.10.

(result)
The value of COP when liquid nitrogen is cooled to a supercooled state of about −205 ° C. is about 0.08 when using a Brayton refrigerator, but in the case of Example 1, it is 0.10. The energy consumption efficiency was higher than when using a Brayton refrigerator. Further, the superconducting cable cooling device 1 used in the first embodiment is a liquid for cooling the superconducting cable cooling liquid nitrogen as in the cooling system (N ₂ diffusion method) disclosed in Non-Patent Document 1. Nitrogen is not released after use. For this reason, in this embodiment, the production cost of liquid nitrogen and periodic replenishment of liquid nitrogen can be eliminated.

DESCRIPTION OF SYMBOLS 1, 2 Superconducting cable cooling device 10 Superconducting cable cooling unit 20, 200 1st supply unit 30 2nd supply unit 11 Liquid refrigerant circulation path 12 Supercooler 12a Body part 12b Throw-type heat exchanger 13 Liquid feed pump 14 Superconducting cable 21 First refrigerant circulation path 22 Discharge path 23 First refrigerant storage tank 24 Heater 25 Vacuum pump 26 Compressor 27 First heat exchanger 28 Flow rate adjustment valve 29 Pressure reducing valve 31 Second refrigerant supply path 32 Second refrigerant storage tank 33 Evaporation 34 Branching path 35 Second refrigerant discharge path 210 Second heat exchanger

Claims (10)

A superconducting cable cooling device for cooling a superconducting cable,
A superconducting cable cooling unit for cooling the superconducting cable with a supercooled liquid refrigerant;
A first supply unit that supplies the first refrigerant in a liquid state for cooling the liquid refrigerant to a supercooled state by heat exchange to the superconducting cable cooling unit;
A second supply unit for supplying a second refrigerant for cooling the first refrigerant by heat exchange to the first supply unit;
Comprising at least
The first supply unit includes:
A reservoir for storing the first refrigerant in a liquid state;
The first refrigerant in the liquid state cools the liquid refrigerant to a supercooled state by heat exchange with the liquid refrigerant, and thereby compresses the first refrigerant in a gas state;
Heat exchange between the first refrigerant in the gaseous state and the second refrigerant, and cooling and liquefying the first refrigerant;
A circulation path for connecting the storage section, the compression section and the first heat exchanger, and circulating the first refrigerant;
A cooling device for a superconducting cable comprising at least. The first supply unit includes a second heat exchanger between the storage unit and the superconducting cable cooling unit,
The second heat exchanger is
The first refrigerant in the liquid state after the heat exchange is performed by exchanging heat between the first refrigerant in the liquid state supplied from the storage unit and the first refrigerant in a gas state by heat exchange with the liquid refrigerant. The cooling device for a superconducting cable according to claim 1, wherein the refrigerant is supplied to the superconducting cable cooling unit.   The cooling device for a superconducting cable according to claim 1 or 2, wherein the liquid refrigerant and the first refrigerant are made of at least one of nitrogen, oxygen, and argon.   The cooling device for a superconducting cable according to any one of claims 1 to 3, wherein the second refrigerant is a refrigerant whose temperature is lower than the boiling point of the first refrigerant in the gaseous state whose boiling point is increased by compression.   The cooling device for a superconducting cable according to claim 4, wherein the second refrigerant is at least one of liquefied natural gas, liquefied methane, liquefied nitrogen, liquefied oxygen, or liquefied argon. A method of cooling a superconducting cable using a cooling device for a superconducting cable,
The superconducting cable cooling device includes a superconducting cable cooling unit that cools the superconducting cable with a supercooled liquid refrigerant, and a liquid first refrigerant that cools the liquid refrigerant to a supercooled state by heat exchange. A first supply unit that supplies the superconducting cable cooling unit, and a second supply unit that supplies the first supply unit with a second refrigerant for cooling the first refrigerant by heat exchange. And
Supplying the first refrigerant in the liquid state stored in the first supply unit to the superconducting cable cooling unit;
Using the first refrigerant in the liquid state, cooling the liquid refrigerant to a supercooled state by heat exchange with the liquid refrigerant,
Compressing the first refrigerant that is in a gaseous state by heat exchange with the liquid refrigerant;
Heat exchange between the first refrigerant in the gaseous state and the second refrigerant, cooling the first refrigerant to a liquid state;
Furthermore, the cooling method of the superconducting cable which circulates the said 1st refrigerant | coolant in a 1st supply unit by storing the said 1st refrigerant | coolant which became the liquid state in the said 1st supply unit.   After exchanging heat between the first refrigerant in the liquid state immediately before being supplied to the superconducting cable cooling unit and the first refrigerant in a gas state due to heat exchange with the liquid refrigerant, the first refrigerant in the liquid state The method for cooling a superconducting cable according to claim 6, wherein a refrigerant is supplied to the superconducting cable cooling unit.   The method for cooling a superconducting cable according to claim 6 or 7, wherein the liquid refrigerant and the first refrigerant are made of at least one of nitrogen, oxygen, and argon.   The method for cooling a superconducting cable according to any one of claims 6 to 8, wherein the second refrigerant is a refrigerant whose temperature is lower than the boiling point of the first refrigerant in the gaseous state whose boiling point is increased by compression.   The method for cooling a superconducting cable according to claim 9, wherein the second refrigerant is at least one of liquefied natural gas, liquefied methane, liquefied nitrogen, liquefied oxygen, or liquefied argon.

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