AU2021338587B2 - High-vacuum multi-layer flexible heat-insulated pipe for high-temperature superconducting cable and manufacturing method thereof - Google Patents
High-vacuum multi-layer flexible heat-insulated pipe for high-temperature superconducting cable and manufacturing method thereof Download PDFInfo
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- 239000010410 layer Substances 0.000 claims abstract description 139
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- 238000009413 insulation Methods 0.000 claims abstract description 7
- 238000012546 transfer Methods 0.000 claims description 24
- 239000007789 gas Substances 0.000 claims description 16
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 14
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 14
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 12
- 238000004088 simulation Methods 0.000 claims description 12
- 238000004364 calculation method Methods 0.000 claims description 10
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- 230000003471 anti-radiation Effects 0.000 claims description 5
- 239000003365 glass fiber Substances 0.000 claims description 5
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 4
- 239000003463 adsorbent Substances 0.000 claims description 4
- 239000000835 fiber Substances 0.000 claims description 4
- 239000001257 hydrogen Substances 0.000 claims description 4
- 229910052739 hydrogen Inorganic materials 0.000 claims description 4
- 239000002516 radical scavenger Substances 0.000 claims description 4
- 239000000126 substance Substances 0.000 claims description 4
- 239000002826 coolant Substances 0.000 claims description 3
- 238000012360 testing method Methods 0.000 claims description 3
- -1 polytetrafluoroethylene Polymers 0.000 claims description 2
- 238000000034 method Methods 0.000 abstract description 21
- 238000012795 verification Methods 0.000 abstract description 3
- 238000010586 diagram Methods 0.000 description 10
- 230000005540 biological transmission Effects 0.000 description 6
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Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B12/00—Superconductive or hyperconductive conductors, cables, or transmission lines
- H01B12/14—Superconductive or hyperconductive conductors, cables, or transmission lines characterised by the disposition of thermal insulation
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
- G06F30/20—Design optimisation, verification or simulation
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/60—Superconducting electric elements or equipment; Power systems integrating superconducting elements or equipment
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Theoretical Computer Science (AREA)
- Computer Hardware Design (AREA)
- Evolutionary Computation (AREA)
- Geometry (AREA)
- General Engineering & Computer Science (AREA)
- General Physics & Mathematics (AREA)
- Thermal Insulation (AREA)
- Superconductors And Manufacturing Methods Therefor (AREA)
Abstract
The present disclosure provides a high-vacuum multi-layer flexible heat-insulated pipe for a
high-temperature superconducting (HTS) cable and a manufacturing method thereof. The
flexible heat-insulated pipe includes an outer pipe, an inner pipe, and a connecting flange. The
flexible heat-insulated pipe further includes: a vacuum interlayer (1) located between the inner
pipe and the outer pipe; a multi-layer heat-insulting material (2), which is located at an inner side
of the vacuum interlayer close to an outer wall of the inner pipe and is configured to achieve heat
insulation; and protrusions (3) on the outer wall of the inner pipe, which are configured to reduce
a contact area between the multi-layer heat-insulting material and the outer wall of the inner pipe.
In the heat-insulated pipe of the present disclosure, there is a small contact area between the
heat-insulting material and the outer wall of the inner pipe, high vacuum efficiency, and
prominent heat-protection performance. In addition, the method of the present disclosure can
accurately calculate and simulate heat leakage data of different heat-insulated pipes, thereby
providing a strong guarantee for the design of a heat-insulated pipe and the verification of
performance of a heat-insulated pipe.
5
3 4
1 - 2
7
6
FIG. 1
Description
[01] The present disclosure relates to the field of superconducting cables, and particularly to a high-vacuum multi-layer flexible heat-insulated pipe for a high-temperature superconducting (HTS) cable and a manufacturing method thereof.
[02] The superconducting technology is applied in power systems in varied forms, which has become one of the main directions of superconducting application research in recent years. Compared with power cables, superconducting cables have great advantages, such as strong power transmission capacity, low cost, small footprint, extremely-low line impedance, low power transmission loss, and strong magnetic interference resistance; and superconducting cables allow long-distance power transmission at a relatively-low voltage, and also allow underground power transmission to avoid noise, electromagnetic pollution, and hidden danger caused by ultra-high-voltage high-altitude power transmission, thereby protecting the ecological environment.
[03] As an important component in HTS cables, a flexible heat-insulated pipe can ensure that a superconducting tape inside is kept at a fixed ambient temperature for a long time, and the transmission performance of the superconducting tape will not be affected due to heat leakage or heat transfer. However, an accurate and reasonable heat-insulated pipe design scheme for the heat-insulated performance of heat-insulated pipes and the design requirements of superconducting cables has not yet been provided in the prior art.
[04] Therefore, there is an urgent need for a high-vacuum multi-layer flexible heat-insulated pipe for an HTS cable and a manufacturing method thereof.
[05] In order to solve the deficiencies in the prior art, the present disclosure provides a high vacuum multi-layer flexible heat-insulated pipe for an HTS cable and a manufacturing method thereof. An outer wall of an inner pipe of the heat-insulated pipe has protrusions, which can reduce a contact area between a heat-insulating material and the outer wall of the inner pipe, thereby improving the vacuum efficiency of a vacuum interlayer. In addition, in the manufacturing method of the present disclosure, a heat leakage of a heat-insulated pipe is accurately predicted by calculating a heat leakage of the heat-insulated pipe to obtain the optimal heat-insulated pipe design scheme.
[06] The present disclosure adopts the following technical solutions.
[07] A first aspect of the present disclosure relates to a high-vacuum multi-layer flexible heat insulated pipe for an HTS cable, including an outer pipe, an inner pipe, and a connecting flange. The flexible heat-insulated pipe further includes: a vacuum interlayer 1 located between the inner pipe and the outer pipe; a multi-layer heat-insulating material 2, which is located at an inner side of the vacuum interlayer close to an outer wall of the inner pipe and is configured to achieve heat insulation; where each layer of the heat-insulting material 2 includes an adsorbing material, an anti-radiation material, a heat-protection material, and a fixing material, the adsorbing material
is configured to adsorb gases among the layers of the heat-insulting material 2, and the fixing material is configured to fix each layer of the heat-insulting material 2; and protrusions 3 on the outer wall of the inner pipe, which are configured to reduce a contact area between the multi layer heat- insulating material and the outer wall of the inner pipe.
[08] Preferably, the protrusions on the outer wall of the inner pipe may have a height of 3 mm to 5 mm, and may be configured to reduce the contact area between the multi-layer heat-insulting material and the outer wall of the inner pipe, such as to improve the vacuum efficiency of the vacuum interlayer.
[09] Preferably, the protrusions on the outer wall of the inner pipe may be distributed on the outer wall of the inner pipe at equal intervals.
[010] Preferably, the multi-layer heat-insulating material may include multiple layers of heat insulting units; and each layer of heat-insulting unit may include at least a reflective screen material and a heat-protection material, and the heat-protection material may be glass fiber paper or chemical fiber paper.
[011] Preferably, the vacuum interlayer of the flexible heat-insulated pipe may further include a support 4 located in the middle of the pipe, a hydrogen scavenger 5 located at one end of the pipe, and a cryogenic adsorbent 6 located at the other end of the pipe; and the support 4 may be a polytetrafluoroethylene (PTFE) pipe that externally helically wraps around the heat-insulting material or a perforated PTFE ring.
[012] A second aspect of the present disclosure relates to a manufacturing method of the high vacuum multi-layer flexible heat-insulated pipe for an HTS cable described in the first aspect of the present disclosure, including the following steps: step 1: based on a liquid nitrogen flow simulation test in a corrugated pipe and a superconducting cable design index, acquiring size parameters of the flexible heat-insulated pipe for an HTS cable; step 2: placing a pre-designed multi-layer heat-insulting material in a calorimeter to obtain a heat leakage of the multi-layer heat-insulting material, and acquiring a heat transfer amount of the support through simulation; and step 3: designing an internal structure of the heat-insulated pipe based on heat-insulating requirements of the heat-insulated pipe, and evaluating the design of the internal structure of the heat-insulated pipe based on the heat leakage calculation.
[013] Preferably, the size parameters of the flexible heat-insulated pipe obtained based on step 1 may at least include: diameters of the inner and outer pipes of the heat-insulated pipe.
[014] Preferably, step 2 may further include: placing the pre-designed multi-layer heat insulting material in a measuring cylinder and a vacuum chamber outside a heat-insulting sheet of the calorimeter; injecting a coolant into a protective cylinder to make a temperature of the calorimeter equal to a temperature of the HTS cable; and connecting the measuring cylinder in the calorimeter to a flow meter, and measuring a heat leakage of pre-designed multi-layer heat insulting materials of different models to determine the optimal model.
[015] Preferably, step 2 may further include: simulating a structure of the support to obtain structural temperature and heat leakage distributions of the support.
[016] Preferably, the heat leakage calculation in step 3 may specifically include: step 3.1: based on materials, sizes, and temperatures of the inner and outer pipes in the flexible heat-insulated pipe and the number of heat-radiation reflective screen layers between the inner and outer pipes, acquiring a heat radiation value of the outer pipe to the inner pipe in the flexible heat-insulated pipe; step 3.2: based on a vacuum degree of the vacuum interlayer and the sizes and temperatures of the inner and outer pipes, acquiring a heat leakage value of residual gas in the vacuum layer; step 3.3: setting a heat leakage value of the support; and step 3.4: based on the heat radiation value of the outer pipe to the inner pipe, the heat leakage value of the residual gas in the vacuum layer, and the heat leakage value of the support, acquiring a total heat load of the heat-insulated pipe.
[017] The present disclosure has the following beneficial effects: Compared with the prior art, the high-vacuum multi-layer flexible heat-insulated pipe for an HTS cable and the manufacturing method thereof in the present disclosure can reduce a contact area between a heat-insulting material and an outer wall of an inner pipe by arranging protrusions on the outer wall of the inner pipe to improve the vacuum efficiency of a vacuum interlayer and ensure the heat-protection efficiency of the heat-insulated pipe. The heat-insulated pipe manufacturing method in the present disclosure can accurately calculate and simulate heat leakage data of heat-insulated pipes in different heat-insulated pipe design schemes, such as to provide a strong guarantee for the design of a heat-insulated pipe and the verification of performance of a heat-insulated pipe.
[018] FIG. 1 is a schematic structural diagram of the high-vacuum multi-layer flexible heat insulated pipe with protrusions on an outer wall of an inner pipe for an HTS cable according to the present disclosure;
[019] FIG. 2 shows a first heat-insulting unit (a), a second heat-insulting unit (b), and a third heat-insulting unit (c);
[020] FIG. 3 is a schematic flowchart of the manufacturing method of the high-vacuum multi layer flexible heat-insulated pipe for an HTS cable according to the present disclosure;
[021] FIG. 4 is a schematic structural diagram of a calorimeter in the manufacturing method of the high-vacuum multi-layer flexible heat-insulated pipe for an HTS cable according to the present disclosure;
[022] FIG. 5 is a schematic diagram illustrating the appearance of the calorimeter in the manufacturing method of the high-vacuum multi-layer flexible heat-insulated pipe for an HTS cable according to the present disclosure;
[023] FIG. 6 is a schematic diagram of simulation of temperature and heat transfer distributions of an external structure of a support of a PTFE pipe in the manufacturing method of the high vacuum multi-layer flexible heat-insulated pipe for an HTS cable according to the present disclosure; and
[024] FIG. 7 is a schematic diagram of simulation of temperature and heat transfer distributions of an internal structure of a support of a PTFE pipe in the manufacturing method of the high vacuum multi-layer flexible heat-insulated pipe for an HTS cable according to the present disclosure.
[025] Reference numerals:
[026] 1: vacuum interlayer,
[027] 2: multi-layer heat-insulting material,
[028] 3: protrusion,
[029] 4: support,
[030] 5: hydrogen scavenger,
[031] 6: cryogenic adsorbent,
[032] 7: connecting flange,
[033] 8: vacuum chamber,
[034] 9: measuring cylinder,
[035] 10: liquid-charging pipe of protective cylinder,
[036] 11: protective cylinder,
[037] 12: heat-insulting sheet,
[038] 13: flow meter,
[039] 14: inner pipe,
[040] 15: outer pipe, and
[041] 16: glass wool.
[042] The prevent disclosure is further described below with reference to the accompanying drawings. The following embodiments are only used for describing the technical solutions of the present disclosure more clearly, and are not intended to limit the protection scope of the present disclosure.
[043] FIG. 1 is a schematic structural diagram of the high-vacuum multi-layer flexible heat insulated pipe for an HTS cable according to the present disclosure. As shown in FIG. 1, the high-vacuum multi-layer flexible heat-insulated pipe for an HTS cable includes an outer pipe, an inner pipe, and a connecting flange 7.
[044] The flexible heat-insulated pipe further includes: a vacuum interlayer 1 located between the inner pipe and the outer pipe; a multi-layer heat-insulting material 2, which is located at an inner side of the vacuum interlayer close to an outer wall of the inner pipe and is configured to achieve heat insulation; and protrusions 3 on the outer wall of the inner pipe, which are configured to reduce a contact area between the multi-layer heat-insulting material and the outer wall of the inner pipe.
[045] In a research process of high-vacuum multi-layer heat-insulation, it is found that a pressure among layers of the multi-layer heat-insulting material 2 is usually 1 to 2 orders of magnitude higher than a pressure of the vacuum interlayer and the protrusion. This is because there is still residual gas among layers of the multi-layer heat-insulting material 2 that has not been evacuated. Since the heat transfer of the residual gas among the layers will lead to an insufficient heat-insulated effect, how to reduce the residual gas among the layers and increase a vacuum degree among the layers of the multi-layer heat-insulting material cannot be ignored. In addition, the large vacuum resistance, low vacuum efficiency, and long vacuum time of the multi-layer heat-insulting material not only cause energy consumption during a vacuum process, but also lead to an unsatisfactory vacuum effect. For this reason, on the basis of the high-vacuum multi-layer heat-insulation, the present disclosure proposes a high-vacuum multi-layer heat insulated solution where there are protrusions 3 on the outer wall of the inner pipe of the heat insulated pipe.
[046] Since the protrusions 3 are provided on the outer wall of the heat-insulated pipe, a contact area between the multi-layer material and the outer wall of the inner pipe is effectively reduced, thereby greatly reducing the solid heat transfer. An air gap will be formed among the protrusions 3, which can allow a vacuum device to effectively evacuate air existing between the multi-layer material and the outer wall of the inner pipe. Moreover, as a pressure among the layers of the multi-layer heat-insulting material decreases, the heat transfer of the gas decreases, and the vacuum efficiency is further improved.
[047] Preferably, the protrusions 3 on the outer wall of the inner pipe may have a height of 3 mm to 5 mm, and may be configured to reduce the contact area between the multi-layer heat insulting material 2 and the outer wall of the inner pipe, such as to improve the vacuum efficiency of the vacuum interlayer.
[048] Preferably, the protrusions 3 on the outer wall of the inner pipe may be distributed on the outer wall of the inner pipe at equal intervals. Specifically, the protrusions 3 may be arranged on the outer wall of the inner pipe at equal intervals, while the remaining structures on the outer wall of the inner pipe remain unchanged.
[049] Preferably, the multi-layer heat-insulting material 2 may include multiple layers of heat insulting units; and each layer of heat-insulting unit may include at least a reflective screen material and a heat-protection material, and the heat-protection material may be glass fiber paper or chemical fiber paper. In an embodiment of the present disclosure, the multi-layer heat insulting material can be composed of three layers, the three layers have different compositions, and each layer can be made of multiple layers of different materials through pressing or the like, but must include a reflective screen layer for anti-radiation and a heat-protection layer for heat protection. In an embodiment of the present disclosure, the multiple layers in the multi-layer heat-insulting material have different heat-insulting materials and different numbers of layers. Specifically, each layer of the heat-insulting material can include an adsorbing material, an anti radiation material, a heat-protection material, and a fixing material. For example, the adsorbing material is arranged to adsorb gases among layers (such as water vapor, nitrogen, and oxygen) to improve a vacuum degree among the material layers, thereby reducing the heat transfer of gases among layers and improving the heat-insulting performance. The anti-radiation material can serve as a reflective screen to achieve reflection and reduce radiative heat transfer. The heat protection material such as glass fiber paper and chemical fiber paper can be arranged to space the reflective screens to prevent direct contact among the reflective screens and reduce heat transfer. The fixing material such as glass fiber tapes can be arranged to fix each layer of heat insulting material to prevent damage to the heat-insulated pipe caused by falling-off of materials and to ensure the firmness and safety of the heat-insulated structure.
[050] Preferably, the vacuum interlayer 1 of the flexible heat-insulated pipe may further include a support 4 located in the middle of the pipe, a hydrogen scavenger 5 located at one end of the pipe, and a cryogenic adsorbent 6 located at the other end of the pipe; and the support 4 may be a PTFE pipe that externally helically wraps around the heat-insulting material or a perforated PTFE ring.
[051] The present disclosure also relates to a manufacturing method of the high-vacuum multi layer flexible heat-insulated pipe for an HTS cable. FIG. 2 is a schematic flowchart of the manufacturing method of the high-vacuum multi-layer flexible heat-insulated pipe for an HTS cable according to the present disclosure. As shown in FIG. 2, the method of the present disclosure includes steps 1 to 3.
[052] The manufacturing of the flexible heat-insulated pipe in the present disclosure is conducted based on the heat leakage calculation for the flexible heat-insulated pipe. Generally, there are two methods for calculating the heat leakage of heat-insulting materials. A first method is to calculate the heat leakage of each layer in the multi-layer heat-insulting material layer by layer. A second method is to independently calculate the heat-radiation, convection, and heat transfer of the multi-layer heat-insulting material and then algebraically sum the above data. However, since the multi-layer heat-insulting material involves heat-radiation, convection, and heat transfer between gas and solid, there will be secondary effects between the above radiation and heat transfer, and the heat leakage performance of the multi-layer heat-insulting material is easily affected by various factors such as pre-treatment process, wrapping implementation process, and material vacuum performance, theoretical calculation results of the multi-layer heat insulting material cannot well meet the needs of practical engineering.
[053] In practical engineering experience, the experimental test method with an engineering calorimeter can be used to obtain the heat-insulting performance of the multi-layer material under high vacuum. Moreover, heat transfer amounts of structures such as the support and the inner and outer pipes can also be calculated based on the heat-transfer theory, such as to finally obtain the total heat leakage of the heat-insulated pipe.
[054] Step 1: Size parameters of the flexible heat-insulated pipe for an HTS cable are acquired based on a liquid nitrogen flow simulation test in a corrugated pipe and a superconducting cable design index.
[055] Preferably, the size parameters of the flexible heat-insulated pipe obtained based on step 1 may at least include: diameters of the inner and outer pipes of the heat-insulated pipe. In an embodiment of the present disclosure, a diameter of the stainless steel inner pipe of the heat insulated pipe can be set to 120 mm, and a diameter of the stainless steel outer pipe can be set to 180 mm.
[056] In addition, according to design size parameters for superconducting cable core cabling, an outer diameter for cabling inside the stainless steel inner pipe can be set to 100 mm when a conductor core is cabled. A welding gap of the heat-insulated pipe is set according to welding requirements, protection requirements, forming requirements, and manufacturing experience of corrugated pipes. A welding gap of the inner pipe can be 20 mm, and a welding gap of the outer pipe can be 18 mm. In addition, a thickness of a metal mesh can be set to 1 mm, a thickness of an inner support can be set to 5 mm, a thickness of an outer support can be set to 6 mm, and a thickness of a heat-insulting layer can be set to 9 mm.
[057] Step 2: A pre-designed multi-layer heat-insulting material is placed in a calorimeter to obtain a heat leakage of the multi-layer heat-insulting material, and a heat transfer amount of the support is acquired through simulation.
[058] Preferably, step 2 may further include: placing the pre-designed multi-layer heat insulting material in a measuring cylinder and a vacuum chamber outside a heat-insulting sheet of the calorimeter; injecting a coolant into a protective cylinder to make a temperature of the calorimeter equal to a temperature of the HTS cable; and
[059] connecting the measuring cylinder in the calorimeter to a flow meter, and measuring a heat leakage of pre-designed multi-layer heat-insulting materials of different models to determine the optimal model.
[060] FIG. 3 is a schematic structural diagram of a calorimeter in the manufacturing method of the high-vacuum multi-layer flexible heat-insulated pipe for an HTS cable according to the present disclosure. FIG. 4 is a schematic diagram illustrating the appearance of the calorimeter in the manufacturing method of the high-vacuum multi-layer flexible heat-insulated pipe for an HTS cable according to the present disclosure. As shown in FIG. 3 and FIG. 4, there are a vacuum chamber 8, a measuring cylinder 9 interconnected with a flow meter 13, and a protective cylinder and a liquid-charging pipe 10 of the protective cylinder for adding a cooling liquid in the calorimeter. The measuring cylinder 9 and the protective cylinder 11 are cylindrical and are arranged coaxially with a cylindrical casing of the calorimeter. A heat-insulting sheet 12 is also provided at outer sides of the protective cylinder and the measuring cylinder.
[061] In step 2, it is contemplated in the present disclosure that multiple different layers of heat-insulting materials may be sequentially overlaid on an outer layer of the heat-insulting sheet. A liquid such as liquid nitrogen is added into the protective cylinder through the liquid-charging pipe, such that a temperature in the calorimeter is consistent with a normal working state of the superconducting cable under liquid nitrogen. Flow data of the measuring cylinder are acquired by the flow meter, and the heat leakage of the multi-layer heat-insulting material is calculated accordingly.
[062] Since three different multi-layer heat-insulting materials are pre-designed in the present disclosure, the three different multi-layer heat-insulting materials (namely, the first, second, and third heat-insulting units shown in FIG. 2) can be referred to as a composite heat-insulting unit, a multi-layer heat-insulting unit, and a protrusion heat-insulting unit, respectively. These three heat-insulting materials have different numbers of material layers and arrangement modes.
[063] The heat leakage is determined for these three materials, and then the heat leakage performance of the three multi-layer heat-insulting materials can be compared.
[064] Table 1 Heat-insulting performance of the three different pre-designed multi-layer heat insulting materials Parameter Composite Multi-layer Protrusion heat-insulting material heat-insulting material heat-insulting material Heat transfer area m2 150 150 150 Heat-insulting 250 103 90 material heat leakage W Specific heat flux W/ 1.67 0.69 0.60 M2
[065] The heat leakage of the multi-layer heat-insulting material arranged in a cylindrical environment with an inner pipe diameter of 120 mm and an outer pipe diameter of 180 mm is measured by a calorimeter. It can be known that a total heat leakage of the composite heat insulting material is 250 W, a heat leakage of the multi-layer heat-insulting material is 103 W, and a heat leakage of the protrusion heat-insulting material is 90 W. In addition, since the three materials have equal heat transfer areas (which are all 150 m 2 ), specific heat fluxes of the three materials can be 1.67 W/m 2 , 0.69 W/m 2 , and 0.60 W/m 2 , respectively.
[066] From the comparison of specific heat flux parameters of the three materials, it can be seen that the protrusion heat-insulting material has the optimal heat-insulting performance, the multi-layer heat-insulting material has the medium heat-insulting performance, and the composite heat-insulting material has the worst heat-insulting performance. Therefore, according to the above experiments, a verified heat-insulting material can be selected and used in the heat-insulated pipe.
[067] In addition, in step 2, the heat transfer amount of the support is also verified. In the present disclosure, two different support structures can be adopted, including a PTFE pipe that externally helically wraps around the heat-insulting material, and a perforated PTFE ring.
[068] Specifically, step 2 may further include: simulating a structure of the support to obtain structural temperature and heat leakage distributions of the support. FIG. 5 is a schematic diagram of simulation of temperature and heat transfer distributions of an external structure of a support of a PTFE pipe in the manufacturing method of the high-vacuum multi-layer flexible heat-insulated pipe for an HTS cable according to the present disclosure. FIG. 6 is a schematic diagram of simulation of temperature and heat transfer distributions of an internal structure of a support of a PTFE pipe in the manufacturing method of the high-vacuum multi-layer flexible heat-insulated pipe for an HTS cable according to the present disclosure. As shown in FIG. 5 and FIG. 6, the structure of the support is simulated by simulation software commonly used in the prior art, and temperatures and heat leakages at different parts of the support are simulated. The heat leakage of the support used in the present disclosure is 8.1 W.
[069] Step 3: An internal structure of the heat-insulated pipe is designed based on heat insulating requirements of the heat-insulated pipe, and the design of the internal structure of the heat-insulated pipe is evaluated based on the heat leakage calculation.
[070] According to data of the heat leakage of the multi-layer heat-insulting material and the heat transfer amount of the support obtained in step 2 and with reference to the heat-insulating requirements of heat-insulated pipes for superconducting cables, the internal structure of the heat-insulated pipe can be preliminarily designed.
[071] Specifically, in the present disclosure, three different design methods can be adopted for the internal structure of the heat-insulated pipe. A first method is to add a multi-layer heat insulting material and glass wool between the inner and outer pipes of the heat-insulated pipe. The inner and outer pipes are insulated by both heat-insulting material and ultra-fine glass wool. A second method is to use a high-vacuum multi-layer flexible heat-insulting jacket. A multi-layer heat-insulting material, such as a three-layer heat-insulting material, is arranged outside the inner pipe, a gap between the inner and outer pipes is sealed and evacuated to a vacuum state, and the heat insulation is achieved through the vacuum and the heat-insulting material. There will be a lot of air in a gap between the heat-insulting material and the inner pipe in the second method, and the air is difficult to be evacuated by a vacuum device. Therefore, in the present disclosure, a third method is adopted. The third method is to use a high-vacuum multi-layer flexible heat insulated pipe and arrange protrusions on an outer wall of an inner pipe regularly. Due to the existence of the protrusions, the air between the outer wall of the inner pipe and the multi-layer heat-insulting material is easily evacuated, thereby ensuring the heat-protection performance of the vacuum interlayer. Therefore, the third method shows a better heat-protection effect than the second method, and can increase the heat-insulting efficiency by 8% to 10% and the vacuum efficiency by about 30%.
[072] Specifically, calculation based on the heat leakage theory can be conducted according to a design scheme to evaluate the design scheme.
[073] Preferably, the heat leakage calculation in step 3 may be specifically as follows:
[074] Step 3.1: A heat radiation value of the outer pipe to the inner pipe in the flexible heat insulated pipe is acquired based on materials, sizes, and temperatures of the inner and outer pipes in the flexible heat-insulated pipe and the number of heat-radiation reflective screen layers between the inner and outer pipes.
[075] A formula for calculating the heat radiation of the outer pipe to the inner pipe in the flexible heat-insulated pipe is as follows:
[076] Q1 = E1 - 2 c u -A - (T2- 14) - F1-2/(n +1) (1)
[077] where E represents an emission rate;
[078] u represents a Stefan-Boltzmann constant, and u = 5.67 x 10-8W/(m 2 - K 4 );
[079] A represents a surface area of the inner pipe of the flexible heat-insulated pipe;
[080] T2 represents a temperature of the outer pipe, and T2 300K in an example of the present disclosure;
[081] T1 represents a temperature of the inner pipe, and Ti 68K in an example of the present disclosure;
[082] F1 -2 represents an angular coefficient of radiative heat transfer, and F1 - 2 = 1; and
[083] n represents the number of heat-radiation reflective screen layers, which is related to the composition of the multi-layer heat-insulting material.
[084] In addition, for the parameter E 1- 2 , acalculation formula is as follows:
[085] E1-2 1A((I+G!>( 1)- 1)2)
[086] where E1 and E2 represent emission rates of stainless steel at room temperature and a low temperature (namely, 68 K), respectively.
[087] Formula (2) is substituted into formula (1) to obtain the heat radiation value Q1 0.132W/m of the outer pipe to the inner pipe in the heat-insulated pipe.
[088] Step 3.2: A heat leakage value of residual gas in the vacuum layer is acquired based on a vacuum degree of the vacuum interlayer and the sizes and temperatures of the inner and outer pipes.
[089] In the method of the present disclosure, a calculation formula of the heat leakage of residual gas is as follows: 10901 Q 2 = k x a x p x (T2 - T1 ) x A (3)
[091] where k represents a coefficient, and k = 1.2001;
[092] a represents a thermal accommodation coefficient, and a = 1; and
[093] p represents a vacuum degree of the interlayer, and in the present disclosure, p 0.01Pa.
[094] According to the method in the present disclosure, Q2 = 1.01W/m.
[095] Step 3.3: A heat leakage value of the support is set.
[096] In the present disclosure, the heat leakage value of the support can be set, or the heat leakage value of the support can be approximated by a simulation method. In the present disclosure, the heat leakage value of the support can be set as Q3 = 0.713W/m.
[0971 Step 3.4: A total heat load of the heat-insulated pipe is acquired based on the heat radiation value of the outer pipe to the inner pipe, the heat leakage value of the residual gas in the vacuum layer, and the heat leakage value of the support.
[098] In the present disclosure, a formula for calculating the total heat load of the heat insulated pipe is as follows: 10991 Q = Q1 + Q2 + Q 3 (4)
[0100] According to the method of the present disclosure, the total heat load Q ~ 1.9W/m of the heat-insulated pipe can be obtained.
[0101] The present disclosure has the following beneficial effects: Compared with the prior art, the high-vacuum multi-layer flexible heat-insulated pipe for an HTS cable and the manufacturing method thereof in the present disclosure can reduce a contact area between a heat-insulting material and an outer wall of an inner pipe by arranging protrusions on the outer wall of the inner pipe to improve the vacuum efficiency of a vacuum interlayer and ensure the heat-protection efficiency of the heat-insulated pipe. The heat-insulated pipe manufacturing method in the present disclosure can accurately calculate and simulate heat leakage data of heat-insulated pipes in different heat-insulated pipe design schemes, such as to provide a strong guarantee for the design of a heat-insulated pipe and the verification of performance of a heat-insulated pipe.
[0102] The implementation examples of the present disclosure are described in detail by the applicants of the present disclosure with reference to the accompanying drawings in the specification. However, those skilled in the art should understand that the above implementation examples are only preferred embodiments of the present disclosure, and the detailed description is only to help readers better understand the spirit of the present disclosure, rather than to limit the protection scope of the present disclosure. On the contrary, any improvement or modification based on the spirit of the present disclosure shall fall within the protection scope of the present disclosure.
[0103] The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that such prior art forms part of the common general knowledge.
[0104] It will be understood that the terms "comprise" and "include" and any of their derivatives (e.g. comprises, comprising, includes, including) as used in this specification, and the claims that follow, is to be taken to be inclusive of features to which the term refers, and is not meant to exclude the presence of any additional features unless otherwise stated or implied.
Claims (10)
1. A high-vacuum multi-layer flexible heat-insulated pipe for a high-temperature superconducting (HTS) cable, comprising an outer pipe, an inner pipe, and a connecting flange, wherein the flexible heat-insulated pipe further comprises: a vacuum interlayer (1) between the inner pipe and the outer pipe; a multi-layer heat-insulting material (2), which is located at an inner side of the vacuum interlayer close to an outer wall of the inner pipe and is configured to achieve heat insulation; wherein each layer of the heat-insulting material (2) comprises an adsorbing material, an anti radiation material, a heat-protection material, and a fixing material, the adsorbing material is configured to adsorb gases among the layers of the heat-insulting material (2), and the fixing material is configured to fix each layer of the heat-insulting material (2); and protrusions (3) on the outer wall of the inner pipe, which are configured to reduce a contact area between the multi-layer heat-insulting material and the outer wall of the inner pipe.
2. The high-vacuum multi-layer flexible heat-insulated pipe for an HTS cable according to claim 1, wherein the protrusions on the outer wall of the inner pipe have a height of 3 mm to 5 mm, and are configured to reduce the contact area between the multi-layer heat-insulating material and the outer wall of the inner pipe, such as to improve a vacuum efficiency of the vacuum interlayer.
3. The high-vacuum multi-layer flexible heat-insulated pipe for an HTS cable according to claim 2, wherein the protrusions on the outer wall of the inner pipe are distributed on the outer wall of the inner pipe at equal intervals.
4. The high-vacuum multi-layer flexible heat-insulated pipe for an HTS cable according to claim 1, wherein the multi-layer heat-insulting material comprises multiple layers of heat-insulating units; and each layer of the heat-insulating unit comprises at least a reflective screen material and a heat-protection material, and the heat-protection material is a glass fiber paper or a chemical fiber paper.
5. The high-vacuum multi-layer flexible heat-insulated pipe for an HTS cable according to claim 1, wherein the vacuum interlayer of the flexible heat-insulated pipe further comprises a support (4) located in the middle of the pipe, a hydrogen scavenger (5) provided at one end of the pipe, and a cryogenic adsorbent (6) provided at the other end of the pipe; and the support (4) is a polytetrafluoroethylene (PTFE) pipe that externally helically wraps around the heat-insulating material, or a perforated PTFE ring.
6. A manufacturing method of the high-vacuum multi-layer flexible heat-insulated pipe for an HTS cable according to claims 1 to 5, comprising the following steps: step 1: based on a liquid nitrogen flow simulation test in a corrugated pipe and a superconducting cable design index, acquiring size parameters of the flexible heat-insulated pipe for an HTS cable; step 2: placing a pre-designed multi-layer heat-insulting material in a calorimeter to obtain a heat leakage of the multi-layer heat-insulating material, and acquiring a heat transfer amount of the support through simulation; and step 3: designing an internal structure of the heat-insulated pipe based on heat-insulating requirements of the heat-insulated pipe, and evaluating the design of the internal structure of the heat-insulated pipe based on a heat leakage calculation.
7. The manufacturing method of the high-vacuum multi-layer flexible heat-insulated pipe for an HTS cable according to claim 6, wherein the size parameters of the flexible heat-insulated pipe obtained in step 1 at least comprise: diameters of the inner and outer pipes of the heat-insulated pipe.
8. The manufacturing method of the high-vacuum multi-layer flexible heat-insulated pipe for an HTS cable according to claim 6, wherein step 2 further comprises: placing the pre-designed multi-layer heat-insulting material in a measuring cylinder and a vacuum chamber outside a heat-insulating sheet of the calorimeter; injecting a coolant into a protective cylinder to make a temperature of the calorimeter equal to a temperature of the HTS cable; and connecting the measuring cylinder in the calorimeter to a flow meter, and measuring a heat leakage of pre-designed multi-layer heat-insulting materials of different models to determine an optimal model.
9. The manufacturing method of the high-vacuum multi-layer flexible heat-insulated pipe for an HTS cable according to claim 6, wherein step 2 further comprises: subjecting a structure of the support to simulation to obtain a structural temperature and a heat leakage distribution of the support.
10. The manufacturing method of the high-vacuum multi-layer flexible heat-insulated pipe for an HTS cable according to claim 6, wherein the heat leakage calculation in step 3 specifically comprises: step 3.1: based on materials, sizes, and temperatures of the inner and outer pipes in the flexible heat-insulated pipe and the number of the heat-radiation reflective screen layers between the inner and outer pipes, acquiring a heat radiation value of the outer pipe to the inner pipe in the flexible heat-insulated pipe; step 3.2: based on a vacuum degree of the vacuum interlayer and the sizes and temperatures of the inner and outer pipes, acquiring a heat leakage value of residual gas in the vacuum layer; step 3.3: setting a heat leakage value of the support; and step 3.4: based on the heat radiation value of the outer pipe to the inner pipe, the heat leakage value of the residual gas in the vacuum layer, and the heat leakage value of the support, acquiring a total heat load of the heat-insulated pipe.
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| CN202110704662.7A CN113393971B (en) | 2021-06-24 | 2021-06-24 | High-vacuum multilayer flexible heat insulation pipe for high-temperature superconducting cable and manufacturing method |
| CN202110704662.7 | 2021-06-24 | ||
| PCT/CN2021/142411 WO2022267417A1 (en) | 2021-06-24 | 2021-12-29 | High-vacuum multi-layer flexible thermal insulation tube for high-temperature superconducting cable and fabrication method |
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| US20070084623A1 (en) * | 2004-07-20 | 2007-04-19 | Kabushiki Kaisha Y.Y.L. | Direct current superconducting power transmission cable and system |
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| JP5505865B2 (en) * | 2010-04-22 | 2014-05-28 | 住友電気工業株式会社 | Insulated tube and superconducting cable |
| JP2012074340A (en) * | 2010-09-01 | 2012-04-12 | Fujikura Ltd | High-temperature superconducting cable |
| CN102705695A (en) * | 2012-05-29 | 2012-10-03 | 张家港市科华化工装备制造有限公司 | Laminated structure and bundling method for multi-layer heat-insulating material in interlayer of low-temperature heat-insulating gas cylinder |
| CN102809581B (en) * | 2012-08-14 | 2014-09-10 | 上海交通大学 | Device for testing performance of low-temperature vacuum multilayer heat-insulation material based on thermal protection |
| EP2961017A1 (en) * | 2014-06-24 | 2015-12-30 | Nexans | Method and assembly for producing a supraconducting cable system |
| CN104295859B (en) * | 2014-10-15 | 2016-03-16 | 航天晨光股份有限公司 | A kind of efficient prefabricated steam insulation pipe |
| CN109411148A (en) * | 2018-11-29 | 2019-03-01 | 深圳供电局有限公司 | A kind of vacuum insulation hyperconductive cable structure |
| CN211399350U (en) * | 2019-12-11 | 2020-09-01 | 广东电网有限责任公司 | Superconducting cable low temperature pipeline leakage detection device |
| CN113393971B (en) * | 2021-06-24 | 2023-04-28 | 国网上海市电力公司 | High-vacuum multilayer flexible heat insulation pipe for high-temperature superconducting cable and manufacturing method |
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| US20070084623A1 (en) * | 2004-07-20 | 2007-04-19 | Kabushiki Kaisha Y.Y.L. | Direct current superconducting power transmission cable and system |
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