JP2019095079A - Cooling system for high temperature superconductive electric power equipment and its operational method - Google Patents

Abstract

To provide a cooling system for high temperature superconductive electric power equipment capable of performing efficient cooling operation under low power consumption when the high temperature superconductive electric power equipment is cooled with liquefaction refrigerant cooled by several refrigerators, and provide its operational method.SOLUTION: The cooling system for high temperature superconductive electric power equipment comprises: a liquefaction refrigerant supply line 1 for use in circulating liquefaction refrigerant; high temperature superconductive electric power equipment 4 installed at the liquefaction refrigerant supply line 1 and cooled by the liquefaction refrigerant; a refrigerant pump 2 installed at the liquefaction refrigerant supply line 1 for circulating the liquefaction refrigerant in force that is led-through from the high temperature superconductive electric power equipment 4; and several refrigerators 3 installed at a downstream side of the refrigerant pump 2 in the liquefaction refrigerant supply line 1 and at an upstream side of the high temperature superconductive electric power equipment 4 to store at least a part of the liquefaction refrigerant supply line 1 and cool the liquefaction refrigerant circulated at the liquefaction refrigerant supply line 1 in which each of the several refrigerators 3 is connected in series to cool the liquefaction refrigerant press fed from the refrigerant pump 2 while being flowed in series among the several refrigerators 3, thereafter the liquefaction refrigerant is fed out to the high temperature superconductive electric power equipment 4.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a cooling system for high temperature superconducting power devices and a method of operating the same.

  For example, when cooling superconducting power devices such as a superconducting power transmission cable, a superconducting transformer, a superconducting motor, a superconducting current limiting device, and a superconducting power storage device, a high temperature superconducting power device using high temperature superconducting (HTS), in particular. In the case of cooling, for example, cooling performance in a cryogenic temperature range of -200.degree. C. or less is required. For this reason, when cooling a high temperature superconducting power device, liquid nitrogen which can be cooled in a very low temperature range is used as a liquefied refrigerant.

  When cooling a superconducting power device, the temperature of the liquefied refrigerant rises due to heat generation caused by induction heat or electricity supplied to a superconductor (for example, a coil, a cable, etc.) constituting the superconducting power device. For this reason, the cooling system for cooling the superconducting power device generally includes a refrigerator for cooling the liquefied refrigerant, a pump for circulating the liquefied refrigerant, and a storage tank for storing the liquefied refrigerant. (See, for example, Patent Document 1).

FIG.4 and FIG.5 is a systematic diagram which shows schematic structure of the conventional cooling system.
As shown in FIG. 4, conventionally, when cooling a high temperature superconducting power device, the liquid nitrogen is cooled by the refrigerator 103 to generate subcooled liquid nitrogen, and this subcooled liquid nitrogen is circulated to the high temperature superconducting power device 104. The cooling method is generally used, and a cooling operation is performed by circulation of liquid nitrogen by the refrigerant pump 102 using one refrigerator 103 having a sufficient cooling capacity. Here, the subcooled state means that the liquid temperature is lower than its saturation temperature, for example, in the case of liquid nitrogen under atmospheric pressure, at a temperature ranging from the boiling point (about 77 K) to the freezing point (about 63 K) It refers to a certain state.

  On the other hand, since high temperature superconducting power devices are often operated in a 24-hour operation, the cooling system is also required to be able to operate in a stable manner for 24 hours. For this reason, in recent years, for example, when maintenance of a refrigerator is required, cooling by 24-hour operation is supported by switching the used refrigerator, each time when maintenance of the refrigerator is required. In such a case, as shown in FIG. 5, a plurality of refrigerant pumps 102A, 102B, 102C and a plurality of refrigerators 103A, 103B, 103C are arranged in parallel, and the subcool state at the outlet of each refrigerator A configuration is employed in which each refrigerator operates independently so that the outlet temperatures Tout of the liquid nitrogen that are determined are equal.

JP, 2016-169880, A

  Here, a configuration in which three refrigerators 103A, 103B, and 103C are arranged in parallel as shown in FIG. 5 is adopted, and, for example, when each of these refrigerators is operated simultaneously, cooling as a cooling system It will be possible to further enhance the ability. For example, if the required cooling capacity required to cool a high-temperature superconducting power device is 6000 watts, the above-mentioned required cooling capacity can be obtained by operating three refrigerators having a cooling capacity of 2000 watts simultaneously. It will be.

  On the other hand, management of the power consumption of the refrigerator is extremely important in the operation of high temperature superconducting power devices. For example, a superconducting transmission cable cooling system is an example of a cooling system for high-temperature superconducting power devices of practical scale. This is a cooling system for superconducting transmission cables ranging from several kilometers to several tens of kilometers, installed between substations, and the refrigeration capacity for cooling this is a large capacity. Therefore, there is a great demand for improvement of the cooling efficiency of the cooling system for high temperature superconducting power devices. Therefore, in the cooling system of high-temperature superconducting power devices, it is very important to reduce the power consumption as much as possible, that is, to operate the refrigerator efficiently from the viewpoint of energy saving, reduction of operation cost, etc. Become. However, for example, when three refrigerators 103A, 103B and 103C are simultaneously operated using a cooling system having a configuration as shown in FIG. 5, since the refrigerators are operated independently, it is necessary. Power was simply three times the power consumption per unit, so it was never an efficient way. For this reason, a cooling system for high temperature superconducting power devices capable of reducing power consumption while realizing high cooling capacity in a cryogenic temperature region has been strongly desired.

  The present invention has been made in view of the above problems, and while cooling a liquefied refrigerant with a plurality of refrigerators, when cooling a high temperature superconducting power device with this liquefied refrigerant, cooling efficiently with little power consumption It is an object of the present invention to provide a possible cooling system for high temperature superconducting power devices and an operating method thereof.

  In order to solve the above problems, the invention according to claim 1 is provided with a liquefied refrigerant supply line for circulating liquefied refrigerant, and the liquefied refrigerant supply line, and is cooled by the liquefied refrigerant circulating through the liquefied refrigerant supply line. A high temperature superconducting power device, a refrigerant pump provided in the liquefied refrigerant supply line, for pumping and circulating the liquefied refrigerant derived from the high temperature superconducting power device, the refrigerant in a flow direction of the liquefied refrigerant in the liquefied refrigerant supply line A plurality of refrigerators provided downstream of a pump and upstream of the high temperature superconducting power device, accommodating at least a part of the liquefied refrigerant supply line, and cooling the liquefied refrigerant circulating in the liquefied refrigerant supply line And the plurality of refrigerators are respectively connected in series, and the liquefied refrigerant pumped from the refrigerant pump is After cooling while flowing in series between the number of the refrigerator, a cooling system for high temperature superconducting power apparatus characterized in that it sent to the high-temperature superconducting power apparatus.

  The invention according to claim 2 is the cooling system according to claim 1, wherein each of the plurality of refrigerators has a refrigerant gas circulation line for circulating a refrigerant gas, and further, in the refrigerant gas circulation line A compressor for compressing the refrigerant gas, an expander for expanding the refrigerant gas, which is disposed downstream of the compressor, the refrigerant gas expanded by the expander and the liquefied refrigerant supply line being circulated And a heat exchanger for liquefied refrigerant which cools the liquefied refrigerant by heat exchange with the liquefied refrigerant, and the refrigerant gas which has passed through the heat exchanger for liquefied refrigerant and the refrigerant gas compressed by the compressor. And a heat exchanger for a refrigerant gas that exchanges heat with the heat exchanger.

  The invention according to claim 3 is the cooling system according to claim 1 or 2, characterized in that the compressors provided in the plurality of refrigerators are operated at the same rotational speed. It is a cooling system for high temperature superconducting power devices.

  The invention according to claim 4 is the cooling system according to claim 1 or 2, wherein the plurality of refrigerators are operated with the same refrigeration capacity. It is.

  The invention according to claim 5 is the cooling system according to any one of claims 1 to 4, characterized in that a bypass pipe is provided for the liquefied refrigerant to bypass the refrigerator. Cooling system for high temperature superconducting power devices.

  Furthermore, the invention according to claim 6 is characterized in that the high temperature superconducting power device is cooled using the cooling system for a high temperature superconducting power device according to any one of claims 1 to 5 It is an operation method of the cooling system for equipment.

According to the cooling system for high-temperature superconducting power devices according to the present invention, the liquefied refrigerant supply line is provided downstream of the refrigerant pump and upstream of the high-temperature superconducting power devices, and cools the liquefied refrigerant circulating in the liquefied refrigerant supply line. High temperature superconducting electric power apparatus after cooling while making the plurality of refrigerators connected in series among the plurality of refrigerators, the plurality of refrigerators being connected in series, respectively, The configuration for sending to
Thus, by arranging a plurality of refrigerators in series, the cooling power is reduced for the driving power of the coolers disposed downstream with respect to the refrigerator disposed upstream of the liquefied refrigerant supply line It can be set with low power without having to As a result, with regard to the cooling of high temperature superconducting power devices, which require a particularly large cooling capacity and the power consumption of the refrigerator tends to be large conventionally, the driving power can be significantly reduced without reducing the cooling capacity. Therefore, it becomes possible to cool the high temperature superconducting power device efficiently with little power consumption.

  Further, according to the method of operating the cooling system for high-temperature superconducting power devices according to the present invention, the method for cooling high-temperature superconducting power devices using the cooling system for high-temperature superconducting power devices according to the present invention having the above configuration Similarly, the drive power of the refrigerator disposed downstream can be set with low power without reducing the cooling capacity. As a result, with regard to the cooling of the high temperature superconducting power device in which the power consumption of the refrigerator tends to increase, the driving power can be significantly reduced without reducing the cooling capacity. Therefore, it becomes possible to cool the high temperature superconducting power device efficiently with little power consumption.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which illustrates typically the cooling system for high temperature superconducting power devices which is one Embodiment of this invention, and its operating method, and is a systematic diagram which shows schematic structure of the whole system. It is a figure which illustrates typically the cooling system for high-temperature superconducting power devices which is one embodiment of the present invention, and its operation method, and is a schematic diagram showing the refrigerator shown in Drawing 1 in more detail. It is a figure explaining the cooling system for high temperature superconducting electric power equipment which is one embodiment of the present invention, and its operation method, and the relation between the cooling capacity of a refrigerator, and cooling temperature is every rotation speed of the compressor with which a refrigerator is equipped Is a graph shown in FIG. It is a figure explaining the composition of the conventional cooling system, and is a systematic diagram at the time of using one refrigerator. It is a systematic diagram explaining the composition of the conventional cooling system, and is a systematic diagram at the time of arranging a plurality of refrigerators in parallel.

  Hereinafter, a cooling system for a high temperature superconducting power device, which is an embodiment to which the present invention is applied, and a method of operating the same will be described with reference to FIG. 1 to FIG. 3 as appropriate. . In the drawings used in the following description, in order to make the features easy to understand, the features that are the features may be enlarged and shown for convenience, and the dimensional ratio of each component is limited to be the same as the actual Absent. In addition, the materials and the like exemplified in the following description are merely examples, and the present invention is not limited to them, and can be appropriately changed and implemented without changing the gist of the invention.

  The cooling system for high temperature superconducting power devices according to the present invention and the operating method thereof include, for example, a high temperature superconducting power device such as a superconducting power transmission cable, a superconducting transformer, a superconducting motor, a superconducting current limiter, and a superconducting power storage device at -200 ° C. It is possible to apply to the application of cooling to the following cryogenic temperature region.

<Cooling system for high temperature superconducting power equipment>
Hereinafter, the configuration of the cooling system for high-temperature superconducting power devices of the present embodiment (hereinafter, may be simply referred to simply as a cooling system) will be described in detail.
As shown in FIG. 1, the cooling system 10 of the present embodiment is provided in the liquefied refrigerant supply line 1 for circulating liquefied refrigerant (not shown) and the liquefied refrigerant supply line 1, and is circulated through the liquefied refrigerant supply line 1. A high temperature superconducting power device 4 cooled by a liquefied refrigerant, a refrigerant pump 2 provided in the liquefied refrigerant supply line 1 for pumping and circulating the liquefied refrigerant derived from the high temperature superconducting power device 4, a liquefied refrigerant in the liquefied refrigerant supply line 1 Provided on the downstream side of the refrigerant pump 2 and the upstream side of the high-temperature superconducting power device 4 in the flow direction, and at least a part of the liquefied refrigerant supply line 1 is accommodated to cool the liquefied refrigerant circulating in the liquefied refrigerant supply line 1 And a plurality of refrigerators 3.

  In the cooling system 10 of the present embodiment, the plurality of refrigerators 3 (3A, 3B, 3C) are connected in series, and the liquefied refrigerant pressure-fed from the refrigerant pump 2 is divided into the plurality of refrigerators 3A, After being cooled while being circulated in series between 3B and 3C, they are sent to the high temperature superconducting power device 4.

  The liquefied refrigerant supply line 1 is a pipe for circulating the liquefied refrigerant stored in the liquefied refrigerant storage tank 8, and the liquefied refrigerant storage tank 8 is connected to a predetermined position in the liquefied refrigerant supply line 1, thereby forming a loop. Configured The liquefied refrigerant supply line 1 has a cooling section 1A disposed in the liquefied refrigerant heat exchanger 34 (see FIG. 2) in the refrigerator 3, which will be described in detail later.

  Here, as the liquefied refrigerant to be circulated in the liquefied refrigerant supply line 1 in the present embodiment, a substance which can be liquefied in a critical temperature region capable of maintaining the superconducting state in cooling a high temperature superconducting power device such as a superconducting power transmission cable. Preferred is one that is excellent in electrical insulation in a subcooled state. As such a liquefied refrigerant, in consideration of safety and cost, for example, liquefied nitrogen (liquid nitrogen) can be used.

  The refrigerant pump 2 pressure-feeds and circulates the liquefied refrigerant supplied from the liquefied refrigerant storage tank 8 into the liquefied refrigerant supply line 1, and in the example shown in FIG. 1, three refrigerant pumps 2A, 2B and 2C are provided. Are connected in parallel. That is, the refrigerant pump 2 has a function of pressure-feeding the liquefied refrigerant to the high temperature superconducting power device 4.

  As the refrigerant pump 2, a general pump used for transporting the refrigerant can be used without any restriction, but in the case of using liquid nitrogen as the liquefied refrigerant, for example, within the range of 30 L / min to 100 L / min. It is preferable to use one that can pump liquid nitrogen.

  The refrigerator 3 is for cooling the liquefied refrigerant circulating in the liquefied refrigerant supply line 1 and, in the example shown in FIG. 1, a plurality of refrigerant pumps 2 and high temperature superconducting power devices 4 in the liquefied refrigerant supply line 1 are provided. More specifically, three refrigerators 3A, 3B and 3C are connected in series on the liquefied refrigerant supply line 1.

  Each of the plurality of refrigerators 3A, 3B, 3C has a refrigerant gas circulation line 31 for circulating a refrigerant gas (not shown) in the example shown in FIG. In addition, the refrigerators 3A, 3B, 3C are provided in the refrigerant gas circulation line 31, and a compressor 32 for compressing the refrigerant gas, and an expansion unit which is disposed on the rear stage side of the compressor 32 and adiabatically expands the refrigerant gas. Each has a machine 33. Furthermore, the refrigerator 3A, 3B, 3C cools the liquefied refrigerant by heat exchange between the refrigerant gas adiabatically expanded by the expander 33 and the liquefied refrigerant (liquid nitrogen) circulating in the liquefied refrigerant supply line 1 Heat exchanger 34, and a refrigerant gas heat exchanger 35 for exchanging heat between the refrigerant gas having passed through the liquefied refrigerant heat exchanger 34 and the refrigerant gas compressed by the compressor 32. Ru. In the illustrated refrigerator 3A, 3B, 3C, a water cooling unit 36 for supplying a refrigerant gas is provided between the compressor 32 and the third section 31C in the refrigerant gas circulation line 31.

  The refrigerators 3A, 3B and 3C provided in the cooling system 1 of the present embodiment respectively accommodate at least a part of the liquefied refrigerant supply line 1 and cool the liquefied refrigerant circulating in the liquefied refrigerant supply line 1 according to the above configuration. It is

  The components of the refrigerator 3A, 3B, 3C other than the compressor 32 and the water-cooling unit 36 are accommodated in a vacuum container (cold box) not shown. This vacuum vessel is for suppressing the penetration of heat from the outside.

The refrigerant gas circulation line 31 is a looped line, and is a line for circulating the refrigerant gas.
The refrigerant gas circulation line 31 has first to third sections 31A, 31B, 31C.
The first section 31A is disposed in the liquefied refrigerant heat exchanger 34, and the expander 33 supplies a refrigerant gas whose temperature is lower than the temperature of the liquefied refrigerant by adiabatic expansion.
The second and third sections 31B and 31C are disposed in the refrigerant gas heat exchanger 35. The low pressure refrigerant gas that has passed through the liquefied refrigerant heat exchanger 34 is supplied to the second section 31B. Further, the high pressure refrigerant gas which is compressed by the compressor 32 and cooled by the water cooling unit 36 is supplied to the third section 31C.

  As the refrigerant gas, one having a liquefying temperature sufficiently lower than the liquefying temperature of the liquefied refrigerant circulating in the liquefied refrigerant supply line 1 is used. When liquefied nitrogen is used as the liquefied refrigerant, it is possible to use, for example, helium gas, neon gas, or a mixed gas obtained by mixing helium gas and neon gas, but it is preferable to use neon gas. As described above, by using neon gas containing neon having a molecular weight larger than that of helium as the refrigerant gas, the speed of sound is reduced, and the number of rotations of the compressor 32 and the expander 33 can be suppressed to be low. It becomes possible to improve the operation reliability of the refrigerator 3.

The liquefied refrigerant heat exchanger 34 is provided at a position that can accommodate the cooling section 1A of the liquefied refrigerant supply line 1 and the first section 31A of the refrigerant gas circulation line 31. The liquefied refrigerant heat exchanger 34 exchanges heat between the liquefied refrigerant flowing in the cooling section 1A and the refrigerant gas which has flowed in the first section 31A and which has become lower in temperature than the temperature of the liquefied refrigerant by the adiabatic expansion in the expander 33 Thus, the liquefied refrigerant is cooled to the subcool temperature.
From the viewpoint of downsizing and high performance, for example, an aluminum plate fin heat exchanger can be used as the heat exchanger 34 for a liquefied refrigerant.

  Here, the liquefied refrigerant which has been cooled to the subcool temperature is introduced into the high temperature superconducting power device 4 through the liquefied refrigerant supply line 1 and is used to cool the high temperature superconducting power device 4 such as a superconducting power transmission cable. On the other hand, the refrigerant gas that has contributed to the cooling of the liquefied refrigerant is transferred to the refrigerant gas heat exchanger 35 of the refrigerant gas circulation line 31, and returned to the compressor 32 via the second section 31B.

The compressor 32 is disposed between the second section 31B and the third section 31C in the refrigerant gas circulation line 31.
The compressor 32 compresses the refrigerant gas to generate a high-temperature and high-pressure refrigerant gas. The high temperature and high pressure refrigerant gas generated by the compressor 32 is delivered to the water cooling unit 36.

  In addition, in FIG. 2, although the case where only one each of the compressor 32 and the water cooling part 36 is provided is mentioned as an example, and demonstrated, it is not limited to this. For example, the plurality of compressors 32 and the water cooling unit 36 may be provided between the second section 31B and the third section 31C in the refrigerant gas circulation line 31. By installing the plurality of compressors 32 and the water cooling unit 36 in the refrigerant gas circulation line 31, it is possible to generate a higher pressure refrigerant gas.

  The water cooling unit 36 is disposed between the compressor 32 and the third section 31C in the refrigerant gas circulation line 31. The water cooling unit 36 cools the temperature of the high temperature and high pressure refrigerant gas to near the ambient temperature. The refrigerant gas cooled by the water cooling unit 36 is delivered to the third section 31C. For example, a water-cooled cooler (shell-and-tube heat exchanger, plate-and-shell heat exchanger) can be used as the water-cooling unit 36.

In the refrigerant gas heat exchanger 35, the second and third sections 31B and 31C of the refrigerant gas circulation line 31 are disposed inside, and the refrigerant gas heat exchanger 35 passes through the liquefied refrigerant heat exchanger 34 and the second section 31B is Heat exchange is performed between the low pressure refrigerant gas flowing therethrough and the high pressure refrigerant gas flowing through the third section 31C after passing through the compressor 32 and the water cooling unit 36.
As the refrigerant gas heat exchanger 35, for example, an aluminum plate fin heat exchanger or the like can be used from the viewpoint of downsizing and high performance.

The expander 33 is disposed between the liquefied refrigerant heat exchanger 34 and the refrigerant gas heat exchanger 35 in the refrigerant gas circulation line 31. The expander 33 adiabatically expands the refrigerant gas to generate refrigerant gas at a temperature lower than the subcool temperature of the liquefied refrigerant.
The expander 33 and the compressor 32 may be disposed on the same rotation axis and integrated. As a result, since the power generated by the expander 33 can be effectively used for driving the compressor 32, the downsizing of the refrigerator 3 and the reduction of the power can be achieved.

  Here, in the cooling system 10 according to the present embodiment, for example, only one or two of the three refrigerators 3A, 3B, 3C are operated while considering both the refrigeration capacity and the power consumption. It is also possible to cool high temperature superconducting power devices under the following conditions.

  The high temperature superconducting power device 4 is, for example, a superconducting power device such as a superconducting power transmission cable, a superconducting transformer, a superconducting motor, a superconducting current limiting device, or a superconducting power storage device, and is cooled by the refrigerator 3 (3A, 3B, 3C) It is cooled to a predetermined temperature by the liquefied refrigerant. Although detailed illustration is omitted, when the high temperature superconducting power device 4 is, for example, a superconducting power transmission cable of a vacuum adiabatic double-pipe structure, the superconducting cable housed in the inner pipe side of the double pipe is predetermined by the liquefied refrigerant. It is cooled to the temperature. On the other hand, the liquefied refrigerant heated by cooling the high temperature superconducting power device 4 is introduced to the plurality of refrigerant pumps 2 (2A, 2B, 2C).

  In the illustrated cooling system 10, bypass piping 7 (7A, 7B, 7C), switching valve 6 (6A, 6B, 6C), and check valve 9 (9A, 9B, 9C) are provided. . For example, when the cooling capacity required for the high temperature superconducting power device 4 is significantly reduced, or when maintenance of a part of the refrigerator 3 becomes necessary, the liquefied refrigerant is bypassed by operating the switching valve 6 By introducing the pipes 7 (7A, 7B, 7C) and switching to bypass the refrigerator 3, the high temperature superconducting power device 4 can be cooled with only a part of the refrigerator 3. That is, the liquefied refrigerant can be introduced into the bypass pipe 7 by the operation of the switching valve 6, and the operation of the bypassed refrigerator can be stopped at this time.

  In the cooling system 10, thermometers 5 (5A, 5B, 5C) are provided corresponding to the respective refrigerators 3A, 3B, 3C, and the liquefied refrigerant temperatures detected by these thermometers are input to a controller (not shown). By doing this, the operation control of the cooling system 10 can be performed according to the temperature of the liquefied refrigerant. At this time, for example, based on the inlet temperature or the outlet temperature (the temperature of the liquefied refrigerant at the inlet or the outlet of the refrigerator) detected by each thermometer, the controller determines the number of operating refrigerant pumps 2A, 2B, 2C. It is possible to control. Alternatively, based on the inlet temperature or the outlet temperature of each refrigerator 3A, 3B, 3C detected by each thermometer, for example, the liquefied refrigerant by controlling the number of rotations of the plurality of compressors 32 or expanders 33 described above It is also possible to change the operating conditions such as flow rate and flow rate of

At this time, when the temperature of the liquefied refrigerant is sufficiently lowered, driving power of a part of the plurality of refrigerators 3A, 3B, 3C, for example, the refrigerator 3C disposed downstream in the illustrated example The energy saving operation can be performed without reducing the cooling capacity, by setting the power consumption of the electric power storage system to a lower power than that of the upstream side refrigerator 3A, 3B.
On the other hand, when it is detected by each thermometer that the temperature of the liquefied refrigerant has not sufficiently decreased, the temperature of the liquefied refrigerant is set by setting the drive power of all the refrigerators 3A, 3B, 3C with high power. The cooling efficiency of the high temperature superconducting power device 4 can be increased immediately.

  In addition, as a method of adjusting the driving power of the refrigerator 3, for example, other than a method of appropriately setting the driving power of the compressor 32 provided in each refrigerator 3A, 3B, 3C to a low power as needed, A method of changing the drive power of the expander 33 can also be adopted.

Here, in the conventional cooling system including three refrigerators 103A, 103B, and 103C in parallel arrangement as shown in FIG. 5, a cooling system including only one refrigerator 103 as shown in FIG. 4 is used. By comparison, its power consumption is simply tripled.
On the other hand, according to the cooling system 10 of the present embodiment, as described above, by employing the configuration in which the plurality of refrigerators 3A, 3B, 3C are arranged in series, in particular, on the upstream side of the liquefied refrigerant supply line 1 With respect to the disposed refrigerator (for example, the refrigerator 3A), the driving power of the refrigerator (for example, the refrigerator 3C) disposed downstream can be set with low power without reducing the cooling capacity. This makes it possible to efficiently cool the high temperature superconducting power device with low power consumption.

<Operation method of cooling system for high temperature superconducting power devices>
Hereinafter, an operation method of the cooling system for a high temperature superconducting power device of the present embodiment will be described with reference to FIGS. 1 and 2.
The operation method of the present embodiment is a method of cooling a high temperature superconducting power device such as a superconducting power transmission cable using the cooling system 10 for a high temperature superconducting power device of the present embodiment as described above.

  First, a liquefied refrigerant supply line is connected to the high temperature superconducting power device 4 using the refrigerant pump 2 (2A, 2B, 2C), and the cooling section 1A passes through the liquefied refrigerant heat exchanger 34 in the refrigerator 3 The liquefied refrigerant stored in the liquefied refrigerant storage tank 8 is supplied to 1.

Next, the liquefied refrigerant passing through the cooling section 1A of the liquefied refrigerant supply line 1 is cooled to a subcool temperature using a plurality of refrigerators 3 (three refrigerators 3A, 3B, 3C in the illustrated example), and high temperature superconducting power By supplying the device 4, the high temperature superconducting power device 4 such as a superconducting power transmission cable is cooled.
Specifically, first, the refrigerators 3A, 3B, and 3C are activated, and the refrigerant gas (not shown) is adiabatically compressed by the compressors 32 provided for each. At this time, the pressure of the refrigerant gas on the high pressure side can be, for example, about 1 to 2 MPa. The refrigerant gas compressed to a high temperature state by the compressor 32 is cooled to normal temperature by the water cooling unit 36 and passes through the refrigerant gas heat exchanger 35.

  Then, in the refrigerant gas heat exchanger 35, the high pressure refrigerant gas which is compressed by the compressor 32 and flows in the third section 31C, passes through the liquefied refrigerant heat exchanger 34, and flows in the second section 31B. The refrigerant gas flowing in the third section 31C is cooled by heat exchange with the low temperature refrigerant gas. The cooled high-pressure refrigerant gas is further cooled via the expander 33 and introduced into the first section 31A.

Next, in the liquefied refrigerant heat exchanger 34, the liquefied refrigerant is subcooled by heat exchange between the refrigerant gas flowing through the first section 31A and further cooled by the expander 33 and the liquefied refrigerant flowing through the cooling section 1A. Cool to temperature.
Furthermore, the liquefied refrigerant that has been cooled to the low subcool temperature is introduced into the high temperature superconducting power device 4 and the high temperature superconducting power device is cooled.
Then, after the liquefied refrigerant that has contributed to the cooling of the high temperature superconducting power device 4 is derived from the high temperature superconducting power device 4, it enters the refrigerant pump again via the liquefied refrigerant supply line 1 and is provided for circulation.

  According to the operation method of the cooling system of the present embodiment, a method of cooling a high temperature superconducting power device using the cooling system 10 in which a plurality of refrigerators 3A, 3B, 3C are arranged in series in the path of the liquefied refrigerant supply line 1 It is. Therefore, the drive power of the refrigerator 3C disposed downstream can be set with low power without lowering the cooling capacity for the reasons described in detail below, so high temperature superconducting power can be efficiently produced with less power consumption. It is possible to cool the device.

  Hereinafter, the relationship between the cooling capacity and the power consumption in the cooling system 10 of the present embodiment will be described.

  Generally, the relationship between the power of the refrigerator in the Carnot cycle, which is an ideal refrigerator, and the cooling capacity is given by the following equation (1).

  However, in said Formula (1), Q: Cooling capacity, W: Power of a refrigerator, Tc: Cooling temperature (degreeC), Th: Ambient temperature (degreeC) which releases heat.

Here, the ratio of the cooling capacity Q to the power W of the refrigerator, that is, "Q / W" in the above equation (1) is called the COP (coefficient of performance) of the refrigerator or the coefficient of performance. .
From the equation (1), when the cooling temperature Tc (here, the outlet temperature of the liquefied refrigerant (liquid nitrogen) increases, the cooling temperature Tc approaches the ambient temperature Th and the denominator on the right side decreases, so the power W of the refrigerator Is the same, the cooling capacity Q increases. That is, the refrigeration efficiency (cooling efficiency) is high.

  Therefore, as in the cooling system 10 shown in FIG. 1, by arranging a plurality of refrigerators 3 (three refrigerators 3A, 3B, 3C in the illustrated example) in series, from the upstream side of the liquefied refrigerant supply line 1 The first refrigerator 3A and the second refrigerator 3B have higher cooling temperatures Tc than the third refrigerator 3C, and the following equation {refrigerator 3A> refrigerator 3B> refrigeration The efficiency as a refrigerator increases in the order represented by 3C}.

  For example, when the refrigerator 3A and the refrigerator 3B are in rated operation (operation at the rated rotational speed of the compressor), the cooling capacity is increased and the load of the refrigerator 3C is reduced, so the compression provided in the refrigerator 3C Power consumption can be reduced because the speed of the machine 32 can be lower than the rated speed. That is, power consumption can be reduced as compared with the conventional cooling system in which three refrigerators are arranged in parallel as shown in FIG.

In a turbo Brayton cycle refrigerator using neon as a refrigerant, for example, a neon refrigerator manufactured by Taiyo Nissho Co., Ltd. (the present applicant), its cooling capacity Q is a cooling temperature T and an operating temperature range of about 65 to 80K. It has been found that there is a relationship represented by the following equation (2) with the number of revolutions N of the compressor.
Q = 40T-7500 + 12N (2)
However, in said Formula (2), it is Q: cooling capacity, T: cooling temperature, N: rotation speed of a compressor.
Further, the above equation (2) is based on data indicating the relationship between the cooling capacity of the refrigerator and the cooling temperature as shown in the graph of FIG. 3 for each rotation speed of the compressor provided in the refrigerator, The relational expression is calculated by the interpolation method (least squares method).

In the following, the case where the outlet temperature (Tout in FIG. 1) of the liquefied refrigerant (liquid nitrogen) of the refrigerator and the inlet temperature (Tin in FIG. 1) are respectively 65 K and 71 K is taken as an example Calculate the power consumption of the aircraft.
In the following description, in the cooling system 10 shown in FIG. 1, the cooling capacities of the refrigerator 3A, the refrigerator 3B and the refrigerator 3C are Q1, Q2 and Q3, respectively, and the total cooling capacity is 6000 watts. For example, The inlet temperature on the side of the refrigerator 3A is Tin, the outlet temperature is T1, the outlet temperature of the refrigerator 3B is T2, and the outlet temperature of the refrigerator 3C is Tout. Further, the flow rate of the liquefied refrigerant (liquid nitrogen) flowing to each of the refrigerators 3A, 3B and 3C is set to be three times (3 M) the flow rate per unit at the time of parallel arrangement as shown in FIG.

Here, when each refrigerator 3A, 3B, 3C performs independent cooling temperature control (control to maintain the outlet temperature of each refrigerator at each setting temperature), the cooling temperature of the refrigerator 3A and the refrigerator 3B (The outlet temperature of each refrigerator) is clearly higher than 65K. Therefore, when the compressors of the refrigerator 3A and the refrigerator 3B are operated at the maximum rotation speed N of 575 rps and the rotation speed of the compressor of the refrigerator 3C is N3, the cooling capacity of each refrigerator 3A, 3B, 3C Q1, Q2, Q3 and their total cooling capacities are expressed by the following formulas (3) to (6).
Q1 = 40 × T1-7500 + 12 × 575 (3)
Q2 = 40 × T2-7500 + 12 × 575 (4)
Q3 = 40 × Tout-7500 + 12 × N3 (5)
Q1 + Q2 + Q3 = 6000 (6)
However, the said (3)-(6) Formula becomes a case where the inlet temperature Tin of 3 A of freezers is 71 K, and the outlet temperature Tout by the side of 3 C of freezers is 65K.

Further, the cooling capacities Q1, Q2 and Q3 of the respective refrigerators 3A, 3B and 3C can be calculated from the amount of heat exchange of liquid nitrogen which is a liquefied refrigerant, as shown in the following formulas (7) to (9).
Q1 = 3M x Cp x (Tin-T1) (7)
Q2 = 3M x Cp x (T1-T2) (8)
Q3 = 3M x Cp x (T2-Tout) (9)
However, in the above formulas (7) to (9), 3 M: three times the circulating amount of liquid nitrogen M per refrigerator in the case of parallel arrangement, Cp: specific heat of liquid nitrogen.

Then, the simultaneous equations expressed by the above equations (3) to (9) are solved as follows.
Q1 = 2150 watts Q2 = 2070 watts Q3 = 1780 watts T1 = 68.85 K
T2 = 66.78K
N3 = 556.7 rps

Further, since the power consumption of the refrigerator is proportional to the number of revolutions N of the compressor, the total power consumption in the case of the series arrangement is divided by the total power consumption in the case of the parallel arrangement, the following equation (10) is obtained It can be seen that the power consumption is reduced in the storage array arrangement.
(2 × 575 + 556.7) / (3 × 575) = 0.9894 (10)

In addition, when the refrigerators are operated in series and the number of revolutions N of the compressor provided in all the refrigerators is set to the same number of revolutions, the following equations (11) to (13) and (6) to (9) It becomes a relationship to be expressed.
Q1 = 40 × T1-7500 + 12 × N (11)
Q2 = 40 × T2-7500 + 12 × N (12)
Q3 = 40 × Tout-7500 + 12 × N (13)
Q1 + Q2 + Q3 = 6000 (6)
Q1 = 3M x Cp x (Tin-T1) (7)
Q2 = 3M x Cp x (T1-T2) (8)
Q3 = 3M x Cp x (T2-Tout) (9)

And when the simultaneous equations represented by said Formula (11)-(13) and (6)-(9) Formula are solved, it will become as follows.
Q1 = 2079 watts Q2 = 1999 watts Q3 = 1922 watts T1 = 68.92K
T2 = 66.92K
N = 568.5 rps

Therefore, the total power consumption in total is as shown in the following equation (14), and the power consumption is higher than the case where the compressor is operated at the rotation speed N lower than the rated rotation speed only as described above. It can be seen that the efficiency is reduced.
(3 × 568.5) / (3 × 575) = 0.9887 (14)

Furthermore, when the refrigerators are operated in series and operated so that the refrigeration capacities (cooling capacities) of all the refrigerators become the same, that is, when Q1 = Q2 = Q3, the following formulas (15) to (17) , And (6) to (9).
Q1 = 40 × T1-7500 + 12 × N1 (15)
Q2 = 40 × T2-7500 + 12 × N2 (16)
Q3 = 40 × Tout-7500 + 12 × N3 (17)
Q1 + Q2 + Q3 = 6000 (6)
Q1 = 3M x Cp x (Tin-T1) (7)
Q2 = 3M x Cp x (T1-T2) (8)
Q3 = 3M x Cp x (T2-Tout) (9)

And when the simultaneous equations represented by said Formula (15)-(17) and (6)-(9) Formula are solved, it will become as follows.
N1 = 561.7 rps
N2 = 568.3 rps
N3 = 575 rps
T1 = 69.0K
T2 = 67.0 K

Therefore, it is understood that the total power consumption in total is as in the following equation (18), and the total power consumption is further reduced and the efficiency is improved more than the above two examples.
(561.7 + 568.3 + 575) / (3 × 575) = 0.9884 (18)

From the above example, a plurality of refrigerators 3 are arranged in series, for example, three refrigerators 3A, 3B, 3C are arranged in series, and each refrigerator independently controls each cooling temperature as in the conventional case. It can be seen that the total power consumption can be reduced as compared to the case where a plurality of refrigerators are arranged in parallel.
Furthermore, it can be seen that when the cooling capacities of the respective refrigerators 3A, 3B, 3C are equally controlled, the total power consumption thereof becomes the smallest, and the optimum operation can be achieved in which the efficiency of the refrigerator is the largest. Also, in order to control the cooling capacity of each refrigerator to operate equally, it is necessary to detect the flow rate of liquefied refrigerant (liquid nitrogen) and the inlet and outlet temperatures to the refrigerator with high accuracy. In the embodiment, this can be easily achieved by maintaining the number of revolutions of the compressor provided in each refrigerator at the optimum number of revolutions obtained from the simultaneous equations as described above.

  In the above example, the case where the inlet temperature Tin of the refrigerator is 71 K and the outlet temperature Tout is cooled to 65 K is described, but the larger the temperature between the inlet and the outlet, the total consumption obtained by the present invention The power reduction effect is more pronounced.

<Function effect>
As described above, according to the cooling system 10 for high-temperature superconducting power devices of the present embodiment, the cooling system 10 is provided downstream of the refrigerant pump 2 in the liquefied refrigerant supply line 1 and upstream of the high-temperature superconducting power devices 4 A plurality of refrigerators 3A, 3B, 3C for cooling the liquefied refrigerant circulating in the refrigerant supply line 1, the plurality of refrigerators 3A, 3B, 3C are respectively connected in series and pressure-fed from the refrigerant pump 2 A configuration is employed in which the liquefied refrigerant is cooled while being circulated in series among the plurality of refrigerators 3A, 3B, 3C, and then sent to the high temperature superconducting power device 4.
As described above, when the upstream side refrigerator 3A and the refrigerator 3B are operated at the rated rotation speed, the downstream side refrigerator 3C has low power. In addition, when all of the refrigerators 3A, 3B, 3C are operated at the rated rotational speed, the total power consumption becomes smaller. Furthermore, if all the refrigerators 3A, 3B, 3C are operated to equalize the refrigerating capacity, the driving power of the upstream refrigerator (for example, the refrigerator 3A) becomes small, and the downstream refrigerator (for example, Although the drive power of the refrigerator 3C) is increased, it is possible to significantly reduce the total power consumption thereof.
Here, in general, since a cooling system for high-temperature superconducting power equipment of practical scale consumes a large amount of power, for example, in a superconducting transmission cable laid between a substation and a substation, the cable is several kilometers to several tens of kilometers Because of the length of the e-mail, the refrigeration capacity for cooling the e-mail will be large, and the number of required refrigerators will also increase significantly. Therefore, even if the improvement rate of the cooling efficiency is about a few percent, the drive power can be set to a much lower level while maintaining the same refrigeration capacity, so a very large power consumption reduction effect can be obtained.
Therefore, it becomes possible to cool the high temperature superconducting power device efficiently with little power consumption.

  Further, according to the method of operating the cooling system for high-temperature superconducting power devices of the present embodiment, the high-temperature superconducting power devices are cooled using the cooling system 10 for high-temperature superconducting power devices of the present embodiment having the above configuration. As described above, since the total power consumption can be significantly reduced, it is possible to efficiently cool the high-temperature superconducting power device with less power consumption.

  According to the cooling system for high temperature superconducting power devices of the present invention and the operating method thereof, while cooling the liquefied refrigerant with a plurality of refrigerators, in cooling the high temperature superconducting power devices with the liquefied refrigerant, the power consumption can be reduced efficiently. It becomes possible to cool. Therefore, for example, it is very suitable in the use etc. which cool high temperature superconducting electric power equipments, such as a superconducting power transmission cable.

DESCRIPTION OF SYMBOLS 10 ... Cooling system for high temperature superconducting electric power equipment 1 ... Liquefied refrigerant supply line 1A ... Cooling area 2, 2A, 2B, 2C ... Refrigerant pump 3, 3A, 3B, 3C ... Refrigerator (multiple refrigerators)
31 Refrigerant gas circulation line 31A First section 31B Second section 31C Third section 32 Compressor 33 Expander 34 Heat exchanger for liquefied refrigerant 35 Heat exchanger for refrigerant gas 4 High temperature superconducting power devices 5, 5A, 5B, 5C ... thermometers 6, 6A, 6B, 6C ... switching valves 7 ... bypass piping 8 ... liquefied refrigerant storage tanks 9, 9A, 9B, 9C ... check valves

Claims (6)

A liquefied refrigerant supply line for circulating the liquefied refrigerant;
A high temperature superconducting power device provided in the liquefied refrigerant supply line and cooled by the liquefied refrigerant circulating in the liquefied refrigerant supply line;
A refrigerant pump which is provided in the liquefied refrigerant supply line and which feeds and circulates the liquefied refrigerant derived from the high temperature superconducting power device;
Provided on the downstream side of the refrigerant pump in the flow direction of the liquefied refrigerant in the liquefied refrigerant supply line and on the upstream side of the high-temperature superconducting power device, and accommodating at least a part of the liquefied refrigerant supply line And a plurality of refrigerators for cooling the liquefied refrigerant circulating in a supply line,
The plurality of refrigerators are connected in series, and the liquefied refrigerant pumped from the refrigerant pump is cooled while being circulated in series among the plurality of refrigerators, and then sent to the high temperature superconducting power device. A cooling system for a high temperature superconducting power device characterized by:   Each of the plurality of refrigerators has a refrigerant gas circulation line for circulating a refrigerant gas, and further, a compressor provided in the refrigerant gas circulation line for compressing the refrigerant gas, and a compressor downstream of the compressor An expander which is arranged to expand the refrigerant gas, and for cooling the liquefied refrigerant by heat exchange between the refrigerant gas expanded by the expander and the liquefied refrigerant circulating in the liquefied refrigerant supply line A heat exchanger, and a refrigerant gas heat exchanger for performing heat exchange between the refrigerant gas having passed through the liquefied refrigerant heat exchanger and the refrigerant gas compressed by the compressor. The cooling system for high temperature superconducting power devices according to 1.   The cooling system for high-temperature superconducting power devices according to claim 1 or 2, wherein the compressors included in the plurality of refrigerators are operated at the same rotational speed.   The cooling system for high temperature superconducting power devices according to claim 1 or 2, wherein the plurality of refrigerators are operated with the same refrigeration capacity.   The cooling system for high-temperature superconducting power devices according to any one of claims 1 to 4, further comprising: a bypass pipe through which the liquefied refrigerant bypasses the refrigerator.   A method of operating a cooling system for a high temperature superconducting power device, comprising cooling the high temperature superconducting power device using the cooling system for a high temperature superconducting power device according to any one of claims 1 to 5.

Images