JP5092220B2 - Insulated multiple piping for superconducting power transmission - Google Patents

Description

  The present invention relates to a heat insulating multiplex pipe for superconducting power transmission, and more specifically, cuts the heat input entering from the outside environment in the heat insulating multiplex pipe for housing a superconducting cable used for superconducting power transmission (meaning to cut off or reduce, the same applies hereinafter). The present invention relates to a heat insulating multiple pipe for superconducting power transmission having a pipe structure.

  When superconducting power transmission is considered, it is necessary to ensure that the superconducting cable can be stably used in a superconducting state, and a piping structure having a heat insulating multi-pipe structure such as a heat insulating double pipe is required. In other words, a conductor (wire cable) that exhibits superconductivity at cryogenic temperatures is placed in the innermost tube of the multi-tube structure, and the inside of the tube is cooled to cryogenic temperature by flowing a cryogenic refrigerant such as liquid nitrogen. It is necessary to block the heat entering from the environment where the whole is placed. Conventionally, a vacuum is maintained between the inner tube (cooled tube or a tube disposed outside thereof) and the tube located outside the tube, and the tubes are not in direct contact with each other. In addition to a structure with a spacer made of a low thermal conductivity material, a film that cuts radiation, called super-insulation, is wound around the outside of the inner tube several times, starting with the far infrared region. Cutting radiant energy from a long wavelength region is performed. Super insulation is an insulating film obtained by depositing aluminum or the like on an organic resin film such as polyester by vapor deposition, sputtering, or the like, and can cut radiant heat. In addition to polyester, materials such as polyimide are also used as film materials.

  FIG. 2 is a cross-sectional view showing an example of a conventional heat insulation multiple pipe for superconducting power transmission. In this example, a superconducting cable 1 is placed in an inner tube 2 having a double-pipe structure, and liquid nitrogen is allowed to flow in the inner tube 2 for cooling. On the outer surface of the inner tube 2, an organic resin-based film is made of an aluminum-based metal. A super insulation 3 made of a vapor-deposited insulating film is wound several times so as to cut the heat passing through the outer tube 5. Further, a spacer 4 having low thermal conductivity is inserted between the outer surface of the inner tube 2 and the inner surface of the outer tube 5 so that the inner and outer tubes are not in direct contact with each other. In addition, since the base pipe of the heat insulation multiple piping for superconducting power transmission is premised on the use of super insulation, the surface roughness is particularly problematic from the viewpoint of the radiation effect (that is, the effect of reducing the radiation rate). Was not.

The super-insulation is naturally considered to be used, and no patent document used for a low-temperature heat insulating double pipe has been found. For the same purpose of cutting radiant heat, a heat insulating vacuum double tube is described in which a sheet prepared by sputtering an aluminum alloy layer on a synthetic resin film is wound around an outer surface of an inner tube.
JP-A-11-125390

  The above-mentioned conventional heat insulation multiple piping for superconducting power transmission is not a problem as long as it is a lab-level mini-scale, but when assuming a device exceeding 10 m or an actual installation, Since super-insulation is used, there is a problem that a fire is likely to occur during construction. That is, when cutting or welding the heat-insulated multiple pipes on site, there is a risk that sparks will easily ignite the super insulation and damage the cable itself.

Superconducting grids are not yet laid. However, it is assumed that power is transmitted throughout the country or around the world like conventional power transmission cables. Sometimes there is a difficulty in damaging cables and fire.
Therefore, the present invention cuts heat input from the outside environment where it is installed by means without such danger, not by means such as super-insulation, which may cause fire or damage caused by it. An object of the present invention is to provide a heat insulating multiple pipe for superconducting power transmission.

The present invention for achieving the above object is innermost superconducting cable housed in the multi-tube structure, in at least one of heat-insulating multiple pipe superconducting power transmission, which is a vacuum insulation layer of the adjacent double tube gap, said adjacent two A structure in which a hole for passing through the inner tube is provided in the polygonal center portion made of a low thermal conductivity material in the gap between the heavy tubes and a hole for suppressing heat intrusion in the other portion, and at least a part of the apex is in point contact with the inner surface of the outer tube The spacer is arranged, and a metal coating is formed on the pipe material, and / or one or more of the pipe material is 0.2 μm or less in Ra on the entire inner surface, outer surface, or both It is the heat insulation multiple piping for superconducting power transmission characterized by having the surface roughness of. In the present invention, the metal coating is preferably made of aluminum, zinc, or an alloy containing them .

In the present invention, the metal coating is preferably a film having an adhesion amount per side of 10 g / m ² or more. This adhesion amount is more preferably 50 g / m ² or more.
The multiple tube structure referred to in the present invention refers to a structure formed by nesting a plurality of tubes having different diameters. Further, the adjacent double pipe gap refers to a space between the adjacent inner pipe and outer pipe.

  According to the present invention, radiation heat input can be cut without using organic material-based flammable super-insulation in a heat-insulated multiple pipe that transmits power using a superconducting cable. In addition, the metal coating used in the present invention cuts heat input from the outside environment and secures a heat insulating effect without contraction or loss due to sparks inevitably generated by cutting work or welding work during construction. be able to. In addition, the work of wrapping over and over like super-insulation is unnecessary, so that the workability of construction is greatly improved.

  In the present invention, (1) a metal coating is used to cut out thermal energy penetration due to radiation, and / or (2) the surface roughness is smoothed to cut out thermal energy penetration due to radiation. If the metal coating is formed, for example, in the case of a heat insulating double tube structure, the outer surface of the inner tube in which the superconducting cable is inserted and the refrigerant such as liquid nitrogen is passed and the inner surface of the outer tube are preferable. It is desirable that the surface constitutes a vacuum insulated gap, the outer surface of the inner tube, and the inner surface of the outer tube. Furthermore, a metal coating may be formed on the inner surface of the inner tube or the outer surface of the outer tube. In the case of a multi-tube structure having a triple tube or more, a superconducting cable is inserted and the outer surface of a tube (preferably the innermost tube) through which a refrigerant such as liquid nitrogen flows, or a plurality of adjacent double tubes in the multi-tube structure. It is preferable to form a metal coating on the outer surface of the inner tube and the inner surface of the outer tube that define the vacuum heat insulating layer among the tube gaps. Furthermore, you may form a metal coating in the inner surface and / or outer surface of piping other than these.

  The background for metal coatings is that when cutting or welding is performed at the time of construction, a fire occurs due to a slight but unavoidable spark, and in particular, super-insulation made of organic resin materials. It is to avoid that the vibration is easily burned and is not deformed (contracted) to become useless. The type of metal used for the metal coating is not particularly limited, but the metal film needs to have a high radiation effect capable of cutting far-infrared light (energy) entering from the outside.

In particular, the metal coating is preferably formed from a single element of aluminum or zinc, or an alloy containing any one or two of them, from the viewpoint of high radiation effect and ease of manufacture.
As a method for forming the metal coating, any method such as an electroplating method, a method of dipping and adhering to a molten metal (a hot dipping method), sputtering, vapor deposition (PVD or CVD), or the like can be preferably used. Depending on the method of forming the metal coating, the same type of film may be formed on the inner and outer surfaces of the pipe with substantially the same thickness, or different types of films may be formed on the both surfaces with different thicknesses. In the invention, it can be adopted in any case, and depending on the expected radiation effect, it is sufficient to determine the type of metal and the amount of film attached, but the amount of adhesion is 10 g / m ² or more per side. In order to achieve the radiation effect, it is preferable to be 50 g / m ² or more per side in order to expect a further effect. Further, since the radiation effect is improved as the thickness of the metal coating is increased, the upper limit of the thickness is not particularly limited in the present invention, and the upper limit thickness (approximately 300 μm) that can be manufactured at present may be used. According to the present invention, compared to producing a super insulation and winding it several times, a single coating operation can be completed, and productivity and on-site workability are remarkably improved.

  Regardless of whether or not the metal coating is formed, the radiation effect can be ensured by setting the surface roughness of the raw tube to 0.2 μm or less by Ra. This method can also avoid the use of super insulation. Combination with metal coating is also possible. If Ra exceeds 0.2 μm, the radiation effect cannot be expected, so it is necessary to be 0.2 μm or less. From the limit of opportunity polishing and chemical polishing, it is estimated that it will be about 0.005 μm. However, as technology advances, this lower level can be even smaller.

When adjusting the surface roughness, the initial surface roughness may not be expected due to the influence of corrosion, etc., so a very thin metal coating such as a chromate film is attached or a film mainly composed of an organic resin is applied. In addition, the surface may be protected.
In addition, in order to prevent heat from entering through a plurality of pipes forming a multi-pipe structure, spacers made of a low heat conductive material are arranged in each of a plurality of adjacent double pipe gaps. It is preferable. In particular, in the best mode of the present invention, the spacer is essentially disposed in the gap formed as a vacuum heat insulating layer in the gap between adjacent double tubes.

As the low thermal conductive material forming the spacer, FRP (fiber reinforced plastic), GFRP (glass fiber reinforced plastic), Teflon (tetrafluoroethylene C ₂ F ₄ polymer) and the like can be preferably used. The overall shape of the spacer may be any polygonal shape, such as a triangle or more, and the inner tube can be passed through a hole formed in the center of the spacer, and all or one of the apexes of the polygonal shape is formed on the inner surface of the outer tube. It is preferable that the parts can be brought into contact with each other. The contact state between the polygonal apex and the inner surface of the outer tube is preferably a point contact state rather than a surface contact state from the viewpoint of further suppressing heat intrusion due to heat conduction. Further, from the viewpoint of further suppressing heat intrusion due to heat conduction, the spacer may have a structure in which holes are appropriately formed in portions other than the center.

FIG. 1 is a cross-sectional view showing Example 1 (1) of the present invention. This example concerns a double tube structure. The superconducting cable 1 is inserted in the inner tube 2. The inner pipe 2 is a SUS316L steel pipe made of a BA (Bright Annealed) material, which has been subjected to hot-dip aluminum plating after electrolytic polishing, and an aluminum plating layer 6 is formed on the inner and outer surfaces of the inner pipe 2. Yes.
The outer tube 5 is obtained by electrolytically polishing a SUS316L steel tube made of a BA material and then subjecting it to hot-dip aluminum plating. An aluminum plating layer 6 is formed on the inner surface and the outer surface of the outer tube 5.

  A square spacer 4 is disposed in the gap between the inner tube 2 and the outer tube 5 to prevent direct mutual contact between the two tubes. The spacer 4 is made of GFRP, and the inner tube 2 is passed through a hole opened in the center so that the square apex is brought into contact with the inner surface of the outer tube 5, so that the distance between the two tubes is maintained. The spacers 4 have a thickness of 2 mm so as to disperse the burden weight to the extent that the inner tube 2 is not broken by the weight of the inner pipe 2, and have an appropriate interval in the length direction (depth direction on the paper) of the heat insulating double pipe. Arranged. The spacer 4 has a structure in which holes 7 are formed in the vicinity of the four apexes, and although it is a low thermal conductivity material, the heat conduction path that invades slightly is made longer so that the heat input can be further reduced. did. In Example 1 (1), both the inner tube and the outer tube are an example in which the aluminum plating layer 6 is formed on both the inner and outer surfaces of the tube by the hot dipping process. The case where the aluminum layer is coated only on the outer side of the tube and the inner side of the outer tube, and the case where zinc or the like is used using a metal other than aluminum are also included in the contents defined by the present invention.

FIG. 3 shows Example 1 (2). In this example, the inner tube 2 and the outer tube 5 of the heat insulating double tube are not coated with metal, and the inner surface roughness of the inner tube 2 and the outer tube 5 is 0.02 μm in Ra.
The superconducting cable 1 is inserted in the inner tube 2. The inner pipe 2 and the outer pipe 5 are made of SUS316L steel pipe made of BA material, and the outer and inner sides are electropolished to further reduce the surface roughness. The surface roughness adjusting surface 9 has a roughness Ra of 0.02 μm.

  A Teflon triangular spacer 8 is disposed in the gap between the inner tube 2 and the outer tube 5 to prevent direct contact between the two tubes. The spacer 4 allows the inner tube 2 to pass through a hole opened in the center, so that any two vertices of the three vertices are always in contact with the inner surface of the outer tube 5, so that the distance between the two tubes is maintained. The spacers 4 have a thickness of 2 mm so as to disperse the burden weight to the extent that the inner tube 2 is not broken by the weight of the inner pipe 2, and have an appropriate interval in the length direction (depth direction on the paper) of the heat insulating double pipe. Arranged. The spacer 4 has a structure in which holes 7 are formed in the vicinity of the three apexes, and although it is a low heat conductive material, it has been devised to further reduce heat input by lengthening the heat conduction path that invades slightly. .

FIG. 4 shows Example 1 (3) in which a chromate film 10 is further formed as a surface protective film for protecting the surface roughness adjusting surface 9 of the outer tube 5 in Example 1 (2). According to this, it is possible to suppress the progress of corrosion on the surface roughness adjusting surface 9 due to the influence of the atmospheric environment or the like, such as exposure to the atmosphere or the like until the manufacture of the heat insulating multi-pipe is completed, and the initial radiation effect Can be maintained.
When transmitting power, the space between the inner tube and the outer tube is brought into a high vacuum state, and then a cryogenic refrigerant (for example, liquid nitrogen) is allowed to flow through the inner tube so that the superconducting cable can maintain the superconducting state. Power is transmitted from. Further, there may naturally be a case where Example 1 (1) and Example 1 (2) are combined. That is, the outer tube may be made of a metal coating and the inner tube may be made of a surface roughness adjusting material, or vice versa.

  The above embodiment relates to a double-pipe structure, but the basic configuration requirements are the same even in the case of a multi-pipe structure of triple or more. In Example 1 (3), the chromate film was used as the protective film on the surface roughness adjusting surface, but the protective film on the surface roughness adjusting surface is not limited to this, and any film having the same protective function may be used. Any kind of film may be used. In the case of a material that does not substantially corrode even if stored in the atmosphere or the like, a film that protects the surface roughness adjusting surface is not necessarily required. That is, according to the present invention that does not use flammable super-insulation, even if a spark or the like is inevitably generated during construction, the structure having radiation effect is not damaged. Realization of heat insulation multiple piping is possible. Also, the manufacturing cost is low.

  The confirmation test of the heat insulation effect by surface roughness adjustment was done using the heat insulation double pipe which shows a longitudinal cross-sectional view in FIG. The heat insulating double pipe shown in FIG. 5 has an outer pipe 5a having a diameter of 150A, an inner pipe 2a having a diameter of 80A, a length of 1500 mm, and a 2 mm-thick GFRP low thermal conductive spacer (not shown in FIG. 5). Three pieces are arranged at an appropriate interval to prevent direct contact between the inner tube and the outer tube. The outer tube and the inner tube are shifted in phase in the tube axis direction by 200 mm, and the openings at both ends are for ultra-high vacuum. Capable of being sealed with lid flange 11 or ICF12 for ultra-high vacuum. Liquid nitrogen can be introduced into the inner tube from the inner tube end protruding from the outer tube.

In the test, for each of the conditions with different surface roughness adjustment specifications as shown in Table 1, the gap between the inner tube and the outer tube was evacuated and then liquid nitrogen was sealed in the inner tube over time. Then, while drawing a vacuum, it was investigated how the vacuum reached. The same vacuum system was used. The evaluation of the degree of vacuum is: ○ when the degree of vacuum reaches 1.0 × 10 ^-7 torr or less within the test time of 14 days at the maximum, × when it stays above 1.0 × 10 ^-6 torr, ○, × The evaluation was performed by a three-stage classification evaluation method in which the case in the middle of (ie, more than 1.0 × 10 ⁻⁷ torr and less than 1.0 × 10 ⁻⁶ torr) was Δ. In the same vacuum system, the higher the ultimate vacuum, the greater the effect of preventing the heat energy from entering the inner tube. The above three stages (○, △, This is because (x) corresponds to a sufficient level, an acceptable level, and a poor level of the effect of preventing the thermal energy from entering the inner tube in order from the lowest vacuum level. In addition, for the surface roughness shown in Table 1, since a test piece for roughness measurement cannot be taken from the tube, prepare a plate-shaped piece made of the same material as the tube and the same surface roughness adjustment as the tube, This was measured as a roughness test piece. The evaluation results are shown in Table 1.

試験No.1はスーパーインシュレーションを使った従来例である。スーパーインシュレーションが有機樹脂基の膜であるゆえ、吸着する水分が真空引きに影響を与えるために時間はかかるものの1.0×10^-7torr以下へ到達できる。尚、この例では、外管はSUS316LのBA材で、表面粗さがRaで0.08μmである。

Test No. 1 is a conventional example using super insulation. Since super-insulation is an organic resin-based film, the adsorbed moisture affects the evacuation and takes time, but can reach 1.0 × 10 ⁻⁷ torr or less. In this example, the outer tube is a SUS316L BA material, and the surface roughness Ra is 0.08 μm.

Test Nos. 2 to 4 correspond to examples of the present invention. These inner pipes are SUS316L electrolytic polishing material, and both the outer and inner surfaces are adjusted to have a surface roughness Ra of 0.04 μm. In Test No. 2, the outer tube is an AP material (Acid-Peeling material = as-washed material), and although it takes a little time, it can reach 1.0 × 10 ⁻⁶ torr or less. In test No. 3, the outer tube is an electrolytic abrasive, and the outer surface of the outer tube is BA-skin and Ra is 0.07 μm, but the inner surface is electropolished and Ra is 0.03 μm, 1.0 × 10 ⁻ Can reach ⁷ torr or less. Test No. 4 is a polished skin material whose outer tube is Al, Ra is adjusted to 0.17 μm, and can reach 1.0 × 10 ⁻⁷ torr or less.

Test No. 5 uses a low-carbon steel (= low-carbon steel) pickled steel plate as the outer tube, and both surfaces are pickled and Ra is as large as 1.3 μm, so 1.0 × 10 ⁻⁶ It cannot reach below torr.
As described above, if the surface roughness Ra is 0.2 μm or less over the entire inner surface and / or outer surface of the inner tube and / or outer tube of the double tube, super insulation is not used. Insulating double pipes can be established.

  This example shows not only the heat insulation double pipe for superconducting power transmission but also applicability to a heat insulation multiple pipe.

The confirmation test of the heat insulation effect by metal coating was done using the heat insulation double pipe which shows a longitudinal cross-sectional view in FIG.
In the test, tests and evaluations were performed in the same manner as in Example 2 for each of the conditions with different metal coating specifications as shown in Table 2. Under each condition, the inner tube was made of an electropolishing material of Ra 0.02 μm, and the outer tube was made of a metal coating forming material. The evaluation results are shown in Table 2.

試験No.51は、外管が、酸洗まま状態の低炭鋼にAlめっきを施したもので、Alめっき付着量が少な目のため、到達真空度レベルは△である。試験No.52〜55は、素管下地と金属コーティングの組合せを表２のように違えたが、何れにおいても金属コーティングの片面当たりの付着量が好適範囲（10g/m²以上）内にあるので、評価は○（到達真空度レベルは1.0×10^-7torr以下）である。尚、表２には示していないが、評価が○の試験No.52〜55の中でも、片面当たりの付着量が更なる好適範囲（50g/m²以上）内にある試験No.53〜55では、それを外れる試験No.52に比べ、より短い時間内に、真空度が1.0×10^-7torr以下へ到達できる。

In Test No. 51, the outer pipe is obtained by subjecting low-carbon steel with acid pickling to Al plating, and since the amount of Al plating attached is small, the ultimate vacuum level is Δ. In Test Nos. 52 to 55, the combination of the base tube base and the metal coating was changed as shown in Table 2, but the adhesion amount per one side of the metal coating was within the preferable range (10 g / m ² or more) in any case. Therefore, the evaluation is ○ (the ultimate vacuum level is 1.0 × 10 ⁻⁷ torr or less). Although not shown in Table 2, among Test Nos. 52 to 55 with an evaluation of ○, Test Nos. 53 to 55 in which the adhesion amount per one side is within a further preferable range (50 g / m ² or more). Then, the degree of vacuum can reach 1.0 × 10 ⁻⁷ torr or less in a shorter time as compared with test No. 52 that deviates from this.

As described above, the metal coating is applied over the entire inner surface and outer surface of the inner tube and / or outer tube of the double tube, preferably the amount of adhesion per side is 10 g / m ² or more, more preferably 50 g / m. If formed so as to be ² or more, an adiabatic double tube can be established without using super insulation.
This example shows not only the heat insulation double pipe for superconducting power transmission but also applicability to a heat insulation multiple pipe.

It is a cross-sectional view showing Example 1 (1) of the present invention. It is a cross-sectional view which shows the example of a prior art. It is a cross-sectional view showing Example 1 (2) of the present invention. It is a cross-sectional view showing Example 1 (3) of the present invention. It is a longitudinal cross-sectional view which shows the heat insulation double tube | pipe used for the test of Example 2 thru | or 3 of this invention.

Explanation of symbols

1 Superconducting cable 2 Inner tube
2a Inner pipe (diameter 80A)
3 Super insulation 4 Spacer (square shape)
5 outer pipe
5a Outer tube (diameter 150A)
6 Aluminum plating layer (metal coating layer)
7 holes 8 spacers (triangular)
9 Surface roughness adjustment surface
10 Chromate film (surface protective film)
11 Ultra high vacuum lid flange
12 ICF for ultra-high vacuum

Claims (4)

Is innermost superconducting cable housed in the multi-tube structure, in at least one of heat-insulating multiple pipe superconducting power transmission, which is a vacuum insulation layer of the adjacent double pipe gap, consisting of low thermal conductivity material into the adjacent double pipe gap polygonal A spacer having a configuration in which a hole for passing through the inner pipe is provided in the center of the shape, a hole for suppressing heat intrusion in the other part, and at least a part of the apex is in point contact with the inner surface of the outer pipe, and piping A metal coating is formed on the material, and / or one or more of the piping materials have a surface roughness of Ra or less of 0.2 μm or less on one or both of the inner surface and the outer surface. Insulated multiple piping for superconducting power transmission.   2. The insulated multipipe for superconducting power transmission according to claim 1, wherein the metal coating is made of aluminum, zinc, or an alloy containing them. The heat insulating multiple pipe for superconducting power transmission according to claim 1 or 2 , wherein the metal coating is a film having an adhesion amount per side of 10 g / m ² or more. The heat insulating multiple pipe for superconducting power transmission according to claim 3, wherein a membrane of 50 g / m ² or more is used instead of the membrane of 10 g / m ² or more.

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