Phase change material parameter selection method and system for cooling hot spots in submarine cables

Abstract

The present invention discloses a method and system for selecting phase change material parameters for cooling overheated spots in submarine cables, and relates to the technical field of submarine cables. Traditional submarine cables have limited heat dissipation effects, and there is a lack of a systematic method for selecting phase change material parameters. The present invention includes the following steps: establishing a three-dimensional electromagnetic-thermal-fluid-solid coupling finite element model of the submarine cable; obtaining the critical current corresponding to the long-term allowable temperature #imgabs0# and the short-term overload temperature #imgabs1# of the cable by gradually increasing the load current, and calculating the emergency time under different overload currents; applying a phase change material layer on the cable model, defining the phase change temperature, thermal conductivity and phase change latent heat as key parameters, and assigning initial values; sampling parameters at fixed intervals, covering the temperature range from #imgabs2# to #imgabs3#; and determining the optimal parameter combination by comparing the emergency times of different parameter combinations through simulation. This technical solution can effectively select phase change material parameters, improve the cooling efficiency of submarine cable overheated spots, and ensure the stability and safety of the cable.

Description

Technical Field

[0001] The present invention relates to the technical field of submarine cables, and in particular to a method and system for selecting parameters of a phase change material for cooling hot spots in submarine cables. Background Art

[0002] Phase change materials have the property of absorbing or releasing large amounts of heat at specific temperatures, making them an ideal heat dissipation material. When the cable overheats, the phase change material can undergo a phase transition at a specific temperature, absorbing or releasing a large amount of heat in the process, thereby maintaining a constant temperature.

[0003] However, successfully applying phase change materials to submarine cable cooling systems requires addressing a number of key technical challenges, one of which is the selection of phase change material parameters. Different phase change materials have varying parameters, such as phase transition temperature, latent heat, and thermal conductivity, which directly impact the cooling performance and stability of the phase change material. Therefore, when selecting a phase change material, comprehensive consideration must be given to factors such as the cable's operating environment, heat dissipation requirements, and material cost and environmental friendliness. This ensures that the selected material maintains cooling effectiveness while also being economical and environmentally friendly. Summary of the Invention

[0004] The technical problem and task addressed by this invention are to refine and improve existing technical solutions by providing a method for selecting parameters for phase change materials used in submarine cable hotspot cooling. This method addresses the limited heat dissipation and lack of systematic consideration in material selection in existing submarine cable cooling technologies. To this end, this invention employs the following technical solutions.

[0005] The first technical solution: A method for selecting parameters of a phase change material for cooling hot spots in submarine cables, comprising the following steps:

[0006] 1) Establish a three-dimensional electromagnetic-thermal-fluid-solid coupled finite element model of the submarine cable. Through simulation, obtain the relationship between the operating temperature change and emergency time of the submarine cable under different load currents, including:

[0007] 1.1) Establish a heat conduction model based on the submarine cable structure, dimensions, and burial environment, setting full soil bottom constraint, side normal constraint, and cable layer bonded contact;

[0008] 1.2) Gradually increase the load current to the maximum long-term operating temperature of the outermost layer of the submarine cable and short-time overload temperature , get the corresponding load current and ;

[0009] 1.3) Calculate the temperature of the outermost layer of the submarine cable under different overload currents Rise to The emergency time is obtained to obtain the relationship between overload current and emergency time;

[0010] 2) Apply phase change material based on the model in step 1, establish a finite element model of the relationship between phase change material parameters and cable temperature changes, define phase change temperature, thermal conductivity and phase change latent heat as key parameters, and assign initial values;

[0011] 3) Adjust the phase change temperature of the phase change material to cover to range, regulating thermal conductivity and latent heat of phase change and sampling at set intervals;

[0012] 4) Comprehensively analyze the three parameter combinations and determine the optimal parameter combination by comparing the emergency time under the same overload current.

[0013] This technical solution forms a technical closed loop through multi-physics field coupling modeling, parameterized collaborative optimization, and boundary processing, which solves the problems of traditional submarine cable thermal management relying on empirical formulas, ignoring multi-field coupling, and low optimization efficiency, and provides a systematic solution for the engineering application of phase change materials in cable overheating protection. Specifically: This technical solution integrates electromagnetic fields, heat conduction, and fluid-solid coupling effects to truly restore the multi-physics field interactions (such as current Joule heating, soil thermal resistance, and structural expansion and deformation) under complex working conditions of submarine cables. Compared with a single physical field model, it can more accurately predict cable temperature distribution and emergency time, avoiding errors caused by traditional simplified models. Set the phase change temperature, thermal conductivity, and phase change latent heat as key parameters, and cover them through systematic sampling. Temperature range, significantly improving parameter optimization efficiency. With the goal of extending overload emergency time, it directly links the heat dissipation response requirements under short-term overload scenarios to ensure that parameter selection is highly matched with actual engineering needs. By comparing the emergency time of different parameter combinations through simulation data, the optimal solution is scientifically determined, replacing the traditional trial and error method that relies on experience. Without the need for physical prototype iteration, parameter screening is completed through virtual experiments, significantly shortening the R&D cycle and reducing testing costs. (Long-term allowable temperature) to Parameter optimization within the short-term overload temperature range ensures that the phase change material can still provide effective thermal protection under extreme operating conditions, ensuring maximum heat dissipation efficiency within the critical temperature range and enhancing system robustness. The model incorporates practical engineering constraints such as inseparable contact between soil and cable and bound contact between cable layers to avoid a disconnect between theoretical design and actual operating conditions. Furthermore, the model breaks through the limitations of single parameter optimization and reveals the synergistic effect of thermal conductivity and latent heat (for example, high thermal conductivity accelerates heat conduction, while high latent heat prolongs heat absorption), providing a scientific basis for material selection.

[0014] As a preferred technical means: in step 1), the soil and the submarine cable are set to be in non-separation contact, allowing gaps and relative sliding; the layers of the cable are in binding contact, the contact areas are connected together, and there is no relative sliding.

[0015] The settings for allowable clearance and relative slip reflect the actual operating conditions of submarine cables. In the actual operating environment, submarine cables are subject to the influence of seawater flow, soil changes, and other dynamic factors. Therefore, allowing a certain amount of relative slip or clearance more realistically simulates the actual physical contact between the cable and the soil. This setting results in more accurate simulations of heat conduction, stress, and temperature changes, helping to optimize the cable's heat dissipation and durability design.

[0016] Because seabed soil can loosen or deform over time, the contact between the cable and soil is not completely fixed. Allowing a certain degree of relative slip allows the model to better reflect the dynamic changes in the actual seabed environment, thereby improving the reliability and stability of the cooling system and avoiding model deviations caused by overly idealized assumptions.

[0017] Bonded contact is established between each cable layer, with the contact areas connected and free of relative slip. This ensures tight and stable thermal conductivity and mechanical connections between the cable's internal layers. This reduces friction and stress caused by interlayer slippage, thereby minimizing the risk of damage to the cable's internal structure. The elimination of relative slip ensures long-term, stable operation of the cable, enhancing its durability and damage resistance.

[0018] Because there's no relative sliding between the cable layers, the bonded contact ensures smoother heat transfer from the inner to the outer layers. This structure enhances thermal conductivity within the cable, helping to more effectively transfer heat generated within the cable to the exterior, improving the cable's heat dissipation capacity and reducing the risk of overheating. Furthermore, the effective contact between the cable and the soil allows for better heat transfer from the cable to the surrounding soil, further improving overall cooling efficiency.

[0019] This setup allows for a more realistic simulation of the cable's interaction with the external environment (such as soil) and internal layers, ensuring a more uniform flow and distribution of heat during the cooling process. This allows for more effective prediction of hot spots that the cable may encounter under actual operating conditions, and allows for optimized cooling designs based on the simulation results to achieve optimal cooling results.

[0020] In practical applications, cables are subject to various external disturbances, such as soil movement and tidal changes. Allowing a certain degree of relative slip and clearance allows the cable system to better adapt to these external changes, maintaining the cooling effect without significant disruption. This dynamic adaptability improves the robustness and reliability of the system.

[0021] As a preferred technical means: in step 3), when adjusting the thermal conductivity of the phase change material, starting from the initial value of 0 W / m·K, a sample is taken every 1 W / m·K.

[0022] By taking a sample every 1 W / m·K, more detailed adjustments can be made within the range of the phase change material's thermal conductivity. This helps identify the specific impact of different thermal conductivities on cable cooling, thereby optimizing material parameters to improve the cable's thermal management efficiency.

[0023] If the thermal conductivity adjustment step size is too large, the optimal thermal conductivity value may be missed, resulting in unsatisfactory cooling performance. Sampling every 1 W / m·K ensures that no details that may affect the cooling performance are missed during the thermal conductivity adjustment of the phase change material, thereby obtaining more accurate optimization results.

[0024] Different thermal conductivities significantly affect the heat transfer properties of phase change materials, thus altering their effectiveness in cooling hot spots. By systematically adjusting the thermal conductivity and taking multiple samples, we can more comprehensively evaluate the performance of phase change materials under different thermal conductivity conditions, helping us select the most appropriate material parameters to maximize cooling effectiveness.

[0025] By sampling every 1 W / m·K, a comprehensive thermal conductivity sample space can be obtained. Even if some thermal conductivity values ​​may be uncommon in real applications, this approach still ensures that a sufficiently wide range of choices is covered, providing more flexible options for cooling system design.

[0026] In practical engineering, the performance of physical materials is affected by environmental variations. By fine-tuning thermal conductivity and conducting sufficient sampling, we can better capture the impact of material property variations on cooling performance, reduce design uncertainties caused by improper material selection, and thus improve the reliability and practicality of the final design.

[0027] By adopting a more refined thermal conductivity adjustment, we can ensure that simulation results are more consistent with actual experimental results. In actual applications, thermal conductivity is often a variable value. By gradually adjusting and sampling, we can more accurately predict the heat conduction conditions in real environments and improve the connection between simulation and experimental data.

[0028] The operating environment of submarine cables is highly complex, and cables may be exposed to varying temperatures, pressures, and other conditions. By sampling diverse parameters at different thermal conductivities, we can better address the needs of different operating environments and ensure that the material can adapt to diverse application scenarios.

[0029] As a preferred technical means: in step 3), when adjusting the phase change latent heat of the phase change material, the phase change latent heat of the phase change material starts from an initial value of 0 J / g, and a sample is taken every 25 J / g.

[0030] By taking samples at intervals of 25 J / g, the latent heat of phase change material can be finely tuned. This helps researchers better understand the impact of latent heat of phase change on cooling performance, ensuring the selection of material parameters that best suit cable cooling requirements and avoiding missed optimization opportunities due to insufficiently precise adjustments.

[0031] The effect of latent heat of phase change on cooling efficiency often changes gradually. Setting sampling intervals of 25 J / g can ensure regulation accuracy while avoiding excessive calculations and achieving reasonable analysis efficiency. This ensures sufficient sample collection without causing excessive unnecessary calculations, improving overall design efficiency.

[0032] The latent heat of phase change is one of the key factors affecting the thermal management performance of phase change materials. By gradually adjusting the latent heat and taking samples, the optimal latent heat value that best meets the heat dissipation requirements of submarine cables can be found.

[0033] Latent heat of phase change is one of the most important thermal properties of phase change materials during their heat absorption or release process, determining how much heat a material can absorb or release within a specific temperature range. By sampling at 25 J / g intervals, we can more accurately simulate and evaluate the impact of varying latent heat on the material's thermal behavior, helping to optimize cooling effects and ensure cable system stability during actual operation.

[0034] Taking a sample every 25 J / g avoids tedious calculations and excessive data points. Compared to adjusting with smaller step sizes, this setting allows for more information to be obtained in a shorter timeframe, ensuring efficient design and reducing unnecessary computational burden.

[0035] By sampling gradually during the latent heat adjustment process, we can provide a wider range of solutions with different latent heat values ​​for comparison. The simulation results can be used to identify the most suitable phase change materials for submarine cable applications, providing a more diverse basis for ultimately selecting optimal parameters.

[0036] As the preferred technical means: use the sweep method, multi-region method or surface mesh method to mesh the three-dimensional electromagnetic-thermal-fluid-solid coupling finite element model of the submarine cable and the finite element model of the relationship between phase change material parameters and cable temperature changes.

[0037] Sweep, multi-region, and volumetric meshing methods all enable fine-grained partitioning of different regions based on model complexity. This refinement of the mesh improves computational accuracy in critical areas, such as heat sources, stress concentrations, or cable hotspots. This refined mesh accurately captures changes in material properties, temperature gradients, and the stress-thermal response of the cable, providing more precise simulation data for cable cooling design.

[0038] Submarine cables are complex structures, involving multiple layers of materials, varying contact areas, and a heterogeneous seabed environment. Sweep, multi-region, and volumetric meshing methods effectively handle complex geometries. Meshing in complex cable geometries and electromagnetic-thermal-fluid-structure interaction scenarios ensures that models better align with the distribution of actual physical fields, enhancing the reliability of simulation results.

[0039] The meshing method can flexibly apply different mesh densities to different areas, so that more detailed meshing is performed in areas of heat and stress concentration, and coarser meshes are used in less critical areas, thereby reducing computing resource consumption while ensuring computational accuracy. By using the sweep method, multi-region method, or surface mesh method, different mesh densities can be selected according to the complexity of different areas. Coarser meshes are used in areas where heat changes slowly or where high-precision simulation is not required, while finer meshes are used in critical areas such as hot spots or material boundaries. In this way, computing resources are reasonably allocated, avoiding the huge computational burden brought by global mesh refinement, ensuring computational accuracy in critical areas, and improving overall computational efficiency. The local meshing strategy can effectively reduce unnecessary computational effort, significantly shorten the time required for simulation while ensuring accuracy, and make the design and optimization process more efficient.

[0040] The design of submarine cables requires consideration of the multi-physics coupling of electromagnetic, thermal, and mechanical fields. Sweep, multi-zone, and volumetric meshing methods can simultaneously address the diverse physics involved in these coupled fields. By employing different mesh densities and methods for each field, the interactions between these fields are accurately reflected.

[0041] In submarine cable operating environments, the contact behavior between cable layers and between the cable and the external soil significantly impacts cooling effectiveness. Using surface meshing and multi-region methods allows for highly accurate segmentation of these contact areas, enabling more precise analysis of temperature gradients, heat conduction, and stress within the contact zone, thereby optimizing cooling system design.

[0042] Phase change materials have relatively complex thermal conductivity characteristics, and their phase change process also produces nonlinear effects. Through fine grid division, the thermal response of phase change materials can be better simulated, the influence of phase change latent heat on temperature change can be accurately calculated, and the simulation accuracy of the cooling effect of phase change materials can be improved.

[0043] As a preferred technical means: the phase change material must meet the following performance requirements:

[0044] The phase change temperature range is 35℃ to 50℃; it will not decompose or deteriorate during long-term use;

[0045] Environmentally friendly and non-corrosive.

[0046] The phase change temperature range of 35°C to 50°C meets the temperature fluctuations required by submarine cables under various operating conditions. Phase change materials within this temperature range ensure timely phase change during cable operation, absorbing excess heat and maintaining the cable within the optimal temperature range, preventing overheating that could damage the cable or reduce efficiency. Submarine cables operate in an extremely complex environment. Long-term exposure to seawater can be affected by factors such as corrosion, high pressure, and temperature fluctuations. The selected phase change material exhibits excellent long-term stability, resisting decomposition or deterioration over extended use. This ensures consistent performance and prevents degradation of the phase change material that could affect cable cooling, thereby extending the cable's service life. The material is non-corrosive, non-toxic, and environmentally friendly.

[0047] The second technical solution is a phase change material parameter selection system for cooling hot spots in submarine cables, which uses the aforementioned method for selecting phase change material parameters for cooling hot spots in submarine cables. The phase change material parameter selection system includes:

[0048] The 3D electromagnetic-thermal-fluid-solid coupling simulation module is used to establish a heat conduction model based on the submarine cable structure, size, and burial environment. It sets full soil bottom constraints, side normal constraints, and cable layer binding contact. It also simulates the relationship between the cable's operating temperature changes and emergency time under different load currents.

[0049] Phase change material coupling modeling module, which applies phase change material based on the simulation model, defines phase change temperature, thermal conductivity and phase change latent heat as key parameters and assigns initial values;

[0050] Parameter adjustment and optimization module, used to adjust the phase change temperature of the phase change material to the maximum long-term operating temperature allowed by the outer layer of the covering cable and short-time overload temperature range, and sample thermal conductivity and phase change latent heat at set intervals;

[0051] The multi-parameter comprehensive analysis module comprehensively analyzes the impact of the three-parameter combination on the cable emergency time and determines the optimal parameter combination.

[0052] The three-dimensional electromagnetic-thermal-fluid-solid coupling simulation module can accurately establish the cable's thermal conduction model based on the actual structure, size and burial environment of the submarine cable. By simulating the relationship between operating temperature changes and emergency time under different load currents, the system can comprehensively predict the thermal effects of the cable under various operating conditions, providing a reliable basis for the selection of phase change material parameters and ensuring the accuracy of the cooling solution.

[0053] The phase change material coupling modeling module can apply phase change materials on the basis of the cable simulation model, and introduce key parameters such as phase change temperature, thermal conductivity and phase change latent heat into the model. By assigning initial values ​​to these parameters and combining them with the simulation results, the system can achieve accurate simulation of phase change materials, ensuring that the material selection is highly matched with the cable temperature control requirements.

[0054] The parameter adjustment and optimization module can adjust the phase change temperature of the phase change material to cover the maximum long-term operating temperature of the cable outer layer ( ) and short-time overload temperature ( ) range, while sampling the thermal conductivity and phase change latent heat at set intervals, enabling the system to accurately adjust and optimize the performance of the phase change material under different environmental conditions and load currents to ensure maximum cooling effect.

[0055] The multi-parameter comprehensive analysis module comprehensively analyzes the impact of three key parameters, phase change temperature, thermal conductivity, and phase change latent heat, on the cable emergency time. It can effectively compare the cooling effects of different parameter combinations, thereby determining the optimal parameter combination. This helps the system fully consider various influencing factors during the design phase and select the best cooling solution.

[0056] Through parameter adjustment and optimization, the system can maintain the cable's operating temperature within a safe range under various load conditions, avoiding hot spots and significantly improving the cable's stability and operational safety. This reduces the risk of cable failure and damage, and increases the cable's service life.

[0057] By using simulation modules and system optimization, the performance of different phase change materials can be predicted and optimized during the design phase, avoiding the need for a large number of actual experiments, thereby greatly improving design efficiency and reducing experimental and R&D costs.

[0058] As a preferred technical means: in the three-dimensional electromagnetic-thermal-fluid-solid coupling simulation module, the soil and the submarine cable are set to be in non-separation contact to allow gaps and relative sliding, and the layers of the cable are in binding contact to eliminate relative sliding.

[0059] As a preferred technical means: the parameter adjustment and optimization module includes a thermal conductivity sampling unit and a phase change latent heat sampling unit. The thermal conductivity sampling unit starts from an initial value of 0 W / m·K, samples incrementally every 1 W / m·K, and is associated with the phase change material thermal conductivity performance database; the phase change latent heat sampling unit starts from an initial value of 0 J / g, samples incrementally every 25 J / g, and is associated with the phase change material energy storage characteristics database.

[0060] As a preferred technical means: the three-dimensional electromagnetic-thermal-fluid-solid coupling simulation module and the phase change material coupling modeling module share an adaptive mesh division unit, and support the sweep method, multi-region method or surface mesh method to discretize the model to ensure a balance between calculation accuracy and efficiency.

[0061] Beneficial effects:

[0062] 1. By carefully selecting the parameters of the phase change material, it can be ensured that the phase change material can achieve the best heat dissipation effect at the hot spots of the submarine cable.

[0063] 2. When selecting phase change materials, the cost, performance and feasibility of the materials in practical applications are comprehensively considered.

[0064] 3. The application of phase change materials can effectively reduce the risk of failure of submarine cables caused by overheating and reduce maintenance requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 Flowchart of the present invention.

[0066] Figure 2 The internal structure of a submarine cable.

[0067] Figure 3 Schematic diagram of direct burial of submarine cables in soil.

[0068] Figure 4 Grid division diagram for direct burial of submarine cables in soil.

[0069] Figure 5 This is the relationship diagram between overload current and emergency time.

[0070] Figure 6 This is a graph showing the relationship between thermal conductivity and maximum temperature of submarine cables.

[0071] Figure 7 This is a diagram showing the relationship between the latent heat of phase change and the maximum temperature of the submarine cable. DETAILED DESCRIPTION

[0072] The technical solution of the present invention is further described in detail below with reference to the accompanying drawings.

[0073] Example 1:

[0074] like Figure 1 As shown, a method for selecting parameters of a phase change material for cooling a submarine cable hot spot of the present invention comprises the following steps:

[0075] S1: Establish a three-dimensional electromagnetic-thermal-fluid-solid coupled finite element model of the submarine cable. Through simulation, obtain the relationship between the operating temperature change and emergency time of the submarine cable under different load currents. Specifically, it includes:

[0076] S1.1: Establish a heat conduction model based on the submarine cable structure, dimensions, and burial environment, setting full soil bottom constraint, side normal constraint, and cable layer bonded contact;

[0077] S1.2: Gradually increase the load current to the maximum long-term operating temperature of the outermost layer of the submarine cable and short-time overload temperature , get the corresponding load current and ;

[0078] S1.3: Calculate the temperature of the outermost layer of the submarine cable under different overload currents. Rise to The emergency time is obtained to obtain the relationship between overload current and emergency time;

[0079] S2: Based on the model in step S1, apply phase change material and establish a finite element model of the relationship between phase change material parameters and cable temperature change. Define phase change temperature, thermal conductivity and phase change latent heat as key parameters and assign initial values.

[0080] S3: Adjust the phase change temperature of the phase change material to cover to range, regulating thermal conductivity and latent heat of phase change and sampling at set intervals;

[0081] S4: Comprehensively analyze the three parameter combinations and determine the optimal parameter combination by comparing the emergency time under the same overload current.

[0082] Through the method of the present invention, the working characteristics and heat dissipation requirements of the hot spots of the submarine cable can be accurately matched, and the parameters of the phase change material with the best performance can be scientifically selected, thereby effectively improving the heat dissipation efficiency of the submarine cable, extending the service life of the cable, reducing the failure rate, and ensuring the safety and stability of power transmission.

[0083] The present invention will be further described below with reference to specific examples.

[0084] 1. Take 640KV cross-linked polyethylene cable as the research object, its internal structure is as follows Figure 2 As shown, from inside to outside are copper conductor 1, conductor shield 2, XLPE insulation 3, insulation shield 4, water-blocking buffer layer 5, alloy lead 6 and asphalt+PE sheath 7.

[0085] 2. Establish a three-dimensional finite element model of the submarine cable and use this model to simulate the relationship between the operating temperature change and emergency time of the submarine cable under different load conditions. The specific method is as follows:

[0086] (1) The simulation model consists of submarine cables and soil, such as Figure 3 As shown in the figure. Based on the project site's impact area, the submarine cable length was set to 10 meters. To reduce computational complexity, the submarine cable was simplified into a four-layer structure based on the principle of similar merging of material mechanical parameters. From the inside out, the structure consists of a copper conductor, insulation layers (conductor shield, XLPE insulation, insulation shield, and water-blocking buffer layer), alloy lead, and an asphalt + PE sheath. The simplified submarine cable dimensions and material parameters are shown in Table 1.

[0087] Table 1 Simplified submarine cable dimensions and material parameters

[0088]

[0089] The soil model is 20m long, 10m wide and 2m high. The submarine cable is buried at a depth of 1m for research. Figure 4 As shown in the figure, when meshing the geometric model with soil structure, the cable structure is meshed differentially, the soil structure is meshed ultra-finely, and the cable body is meshed extremely finely, which reduces the amount of solution calculation while ensuring accuracy.

[0090] (2) Set the ambient temperature of the submarine cable to 15°C, apply a low initial load current I1 to the cable, I1 is 1000A, and gradually increase the load current until it reaches the long-term maximum operating temperature of 90°C. At this time, the outermost temperature of the submarine cable is 37°C and the load current is 2385A, that is, T1 is 37°C and I2 is 2385A.

[0091] (3) Starting from the load current of 2385A, the load current is increased and adjusted until it reaches the long-term short-term overload temperature of 120℃. At this time, the outermost temperature of the submarine cable is 47℃ and the overload current is 2820A, that is, T2 is 47℃ and I3 is 2820A.

[0092] (4) Based on the load current of 2385A obtained above, overload currents of 2862A, 3101A, 3339A, 3578A and 3816A are applied respectively to obtain the emergency time required from the maximum operating temperature of 90℃ to the short-term overload temperature of 120℃, as shown in the following example: Figure 5 shown.

[0093] 3. Build a three-dimensional finite element model of the submarine cable with external coating material, and use this model to simulate the relationship between the parameters of the phase change material and the operating temperature change of the submarine cable. The specific method is as follows:

[0094] (1) Based on the submarine cable model established in step 2, a phase change material is applied. The material property settings, mesh division, boundary conditions, and load application of the submarine cable are consistent with the conditions applied in step 2.

[0095] (2) The characteristics of the phase change material are defined by the three parameters of phase change temperature, phase change latent heat and thermal conductivity. The corresponding initial values ​​are set for these three parameters. The initial values ​​of the three parameters are obtained according to the change of the working temperature of the submarine cable. The values ​​of the three parameters are adjusted until they are optimal.

[0096] (3) The phase change temperature range is between the temperature of the outermost layer of the submarine cable when the maximum working temperature is reached and the temperature of the outermost layer of the submarine cable when the potential overheating risk temperature is reached. Therefore, the lower limit temperature of the phase change temperature of the phase change material is 37°C and the upper limit temperature is 47°C.

[0097] (4) The initial value of thermal conductivity is set to 0 W / m·K, and a sample is taken every 1 W / m·K to obtain the relationship between thermal conductivity and maximum temperature of submarine cable, as shown in the following example: Figure 6 shown.

[0098] (5) The initial value of the phase change latent heat is set to 0 J / g, and a sample is taken every 25 J / g to obtain the relationship between the phase change latent heat and the maximum temperature of the submarine cable, as shown in the following example: Figure 7 shown.

[0099] 4. Comprehensively analyze the data of the three parameters and select the most suitable parameter combination. The specific method is as follows:

[0100] (1) When the thermal conductivity reaches 10 W / m·K, the maximum temperature of the submarine cable will no longer change, indicating that the heat generated inside the cable is equal to the heat dissipated by the external environment, and the cable will reach a thermal equilibrium state. At this time, the temperature of the cable will remain at a stable value and will no longer change significantly. Even if the thermal conductivity of the phase change material continues to increase, as long as this thermal equilibrium state is not broken, the temperature of the cable will not continue to drop. Excessively high thermal conductivity may cause heat to be transferred to the surrounding environment too quickly, thereby increasing the energy consumption and complexity of the system. Taking all factors into consideration, the thermal conductivity is selected within the range of 9-11 W / m·K.

[0101] (2) After the phase change latent heat reaches 200 J / g, the maximum temperature of the submarine cable no longer changes. This is because the temperature of the cable is determined by the balance between its internal heat generation and external heat dissipation. As long as this balance does not change, the cable temperature will not change. The phase change latent heat only changes how much heat the material can absorb during the phase change process, and does not directly affect this balance. Taking all factors into consideration, the phase change latent heat is taken within the range of 190-210 J / g.

[0102] (3) The data of thermal conductivity and phase change latent heat were grouped, and a load current of 3101A was applied to the submarine cable made of phase change material. The optimal combination was selected based on the emergency time of each group, as shown in Table 2.

[0103] Table 2 Combinations of thermal conductivity and phase change latent heat parameters

[0104]

[0105] (4) It can be concluded from Table 2 that the emergency time is the same when the thermal conductivity is 10 W / m·K and 11 W / m·K and the phase change latent heat is 200 J / g and 210 J / g. This is because when the thermal conductivity and phase change latent heat of the phase change material are 10 W / m·K and 200 J / g, the submarine cable is in thermal equilibrium. Therefore, the combination of thermal conductivity and phase change latent heat of 10 W / m·K and 200 J / g is the optimal combination. Combined with the phase change temperature of 37℃-47℃ calculated above, these three data are the optimal choices for the three parameters of the phase change material.

[0106] Example 2:

[0107] A phase change material parameter selection system for cooling hot spots in submarine cables adopts the aforementioned phase change material parameter selection method. The phase change material parameter selection system includes:

[0108] The 3D electromagnetic-thermal-fluid-solid coupling simulation module is used to establish a heat conduction model based on the submarine cable structure, size, and burial environment. It sets full soil bottom constraints, side normal constraints, and cable layer binding contact. It also simulates the relationship between the cable's operating temperature changes and emergency time under different load currents.

[0109] Phase change material coupling modeling module, which applies phase change material based on the simulation model, defines phase change temperature, thermal conductivity and phase change latent heat as key parameters and assigns initial values;

[0110] Parameter adjustment and optimization module, used to adjust the phase change temperature of the phase change material to the maximum long-term operating temperature allowed by the outer layer of the covering cable and short-time overload temperature range, and sample thermal conductivity and phase change latent heat at set intervals;

[0111] The multi-parameter comprehensive analysis module comprehensively analyzes the impact of the three-parameter combination on the cable emergency time and determines the optimal parameter combination.

[0112] The three-dimensional electromagnetic-thermal-fluid-solid coupling simulation module supports multi-physics field dynamic simulation, comprehensively capturing the thermal-mechanical coupling effects of cables in complex environments and ensuring the accuracy of temperature and stress field data.

[0113] The parameter adjustment and optimization module adopts discrete sampling (such as 1 W / m·K interval for thermal conductivity and 25 J / g interval for phase change latent heat) combined with emergency time dynamic analysis to avoid the blindness of traditional trial and error methods and achieve scientific parameter selection.

[0114] The phase transition temperature range is limited to to (such as 37℃-47℃), ensuring that the material absorbs heat efficiently within the cable overload risk temperature range and slows down the temperature rise rate.

[0115] The simulation module uses the "non-separation contact" (allowing gaps and relative sliding) between the soil and the cable and the "bound contact" setting of the cable layer to reproduce the actual working conditions of the submarine cable and avoid model distortion caused by the traditional rigid contact assumption.

[0116] In order to reduce resource consumption and improve simulation efficiency while ensuring calculation accuracy, an extremely fine grid (≤0.5 mm) is used for the cable body and an ultra-fine grid (≤2 mm) is used for the soil.

[0117] By comparing the emergency response times of different combinations through a multi-parameter comprehensive analysis module, the heat dissipation efficiency can be effectively improved compared to traditional methods, and the formation of hot spots can be effectively suppressed.

[0118] The system supports the input of different cable structures (such as cross-linked polyethylene cables and oil-paper insulated cables) and environmental parameters (such as soil type and seawater temperature), and adapts to the diverse submarine cable laying needs around the world.

[0119] High-precision simulation replaces a large number of experiments, shortening the R&D cycle and reducing the cost of material testing and on-site debugging.

[0120] Environmentally friendly phase change materials (non-toxic and non-corrosive) are preferred to reduce the impact on marine ecology, while reducing material redundancy costs through scientific material selection.

[0121] This technical solution represents an innovative breakthrough compared to existing technologies. Traditional systems often use single physical field simulation or simplified parameter adjustment methods, resulting in overly theoretical or lack of systematic heat dissipation design. This solution achieves technical breakthroughs through the following innovations:

[0122] Multi-physics coupling and real contact modeling: Combining electromagnetic-thermal-fluid-solid coupling simulation with dynamic contact conditions (gap, sliding) solves the problem of "falsely high heat conduction efficiency" in traditional models.

[0123] Discrete sampling and dynamic emergency time matching: Key parameters are sampled at fixed intervals and directly linked to engineering requirements through emergency time to achieve "data-driven" precise optimization.

[0124] This technical solution solves the core problems of "insufficient heat dissipation efficiency" and "lack of systematic parameter selection" in the cooling of submarine cable hot spots through integrated modeling, scientific parameter optimization and real-world operating condition simulation.

[0125] The above-mentioned method and system for selecting phase change material parameters for cooling hot spots in submarine cables are specific embodiments of the present invention, which have embodied the substantial features and progress of the present invention. Based on actual use needs and in accordance with the teachings of the present invention, equivalent modifications can be made to the method and system, which are all within the scope of protection of this solution.

Claims

1. A method for selecting parameters of phase change materials for cooling hot spots in submarine cables, characterized in that: The following steps are involved: 1) Establish a three-dimensional electromagnetic-thermal-fluid-solid coupled finite element model of the submarine cable. Through simulation, obtain the relationship between the operating temperature change and emergency time of the submarine cable under different load currents, including: 1.1) Establish a heat conduction model based on the submarine cable structure, dimensions, and burial environment, setting full soil bottom constraint, side normal constraint, and cable layer bonded contact; The soil and submarine cable are set to be in non-separable contact, allowing gaps and relative sliding; 1.2) Gradually increase the load current to the maximum long-term operating temperature of the outermost layer of the submarine cable and short-time overload temperature , get the corresponding load current and ; 1.3) Calculate the outermost temperature of the submarine cable under different overload currents. Rise to The emergency time is obtained to obtain the relationship between overload current and emergency time; 2) Apply phase change material based on the model in step 1, establish a finite element model of the relationship between phase change material parameters and cable temperature changes, define phase change temperature, thermal conductivity and phase change latent heat as key parameters, and assign initial values; 3) Adjust the phase change temperature of the phase change material to cover to range, regulating thermal conductivity and latent heat of phase change and sampling at set intervals; 4) Comprehensively analyze the three parameter combinations and determine the optimal parameter combination by comparing the emergency time under the same overload current.

2. The method for selecting parameters of a phase change material for cooling a submarine cable hot spot according to claim 1, characterized in that: In step 1), the layers of the cable are in bonded contact, and the contact areas are connected together without relative sliding.

3. The method for selecting parameters of a phase change material for cooling hot spots in submarine cables according to claim 2, characterized in that: In step 3), when adjusting the thermal conductivity of the phase change material, starting from the initial value of 0 W / m·K, a sample is taken every 1 W / m·K.

4. The method for selecting parameters of a phase change material for cooling a submarine cable hot spot according to claim 3, wherein: In step 3), the phase change latent heat of the phase change material is adjusted; the phase change latent heat of the phase change material starts from an initial value of 0 J / g, and a sample is taken every 25 J / g.

5. The method for selecting parameters of a phase change material for cooling a submarine cable hot spot according to claim 4, characterized in that: The sweep method, multi-region method or surface mesh method are used to mesh the three-dimensional electromagnetic-thermal-fluid-solid coupling finite element model of the submarine cable and the finite element model of the relationship between phase change material parameters and cable temperature change.

6. The method for selecting parameters of a phase change material for cooling a submarine cable hot spot according to claim 5, characterized in that: The phase change material must meet the following performance requirements: The phase change temperature range is 35℃ to 50℃; it will not decompose or deteriorate during long-term use; Environmentally friendly and non-corrosive.

7. A phase change material parameter selection system for cooling hot spots in submarine cables, characterized by: A method for selecting phase change material parameters for cooling hot spots in submarine cables according to any one of claims 1 to 6 is used, wherein the phase change material parameter selection system comprises: The 3D electromagnetic-thermal-fluid-solid coupling simulation module is used to establish a heat conduction model based on the submarine cable structure, size, and burial environment. It sets full soil bottom constraints, side normal constraints, and cable layer binding contact. It also simulates the relationship between the cable's operating temperature changes and emergency time under different load currents. Phase change material coupling modeling module, which applies phase change material based on the simulation model, defines phase change temperature, thermal conductivity and phase change latent heat as key parameters and assigns initial values; Parameter adjustment and optimization module, used to adjust the phase change temperature of the phase change material to the maximum long-term operating temperature allowed by the outer layer of the covering cable and short-time overload temperature range, and sample thermal conductivity and phase change latent heat at set intervals; The multi-parameter comprehensive analysis module comprehensively analyzes the impact of the three-parameter combination on the cable emergency time and determines the optimal parameter combination.

8. The phase change material parameter selection system for cooling hot spots in submarine cables according to claim 7, characterized in that: In the three-dimensional electromagnetic-thermal-fluid-solid coupling simulation module, the soil and the submarine cable are set to be in non-separation contact to allow gaps and relative sliding, and the layers of the cable are in binding contact to eliminate relative sliding.

9. The phase change material parameter selection system for cooling hot spots in submarine cables according to claim 8, characterized in that: The parameter adjustment and optimization module includes a thermal conductivity sampling unit and a phase change latent heat sampling unit. The thermal conductivity sampling unit starts from an initial value of 0 W / m·K, samples incrementally every 1 W / m·K, and is associated with the phase change material thermal conductivity performance database; the phase change latent heat sampling unit starts from an initial value of 0 J / g, samples incrementally every 25 J / g, and is associated with the phase change material energy storage characteristics database.

10. The phase change material parameter selection system for cooling hot spots in submarine cables according to claim 9, characterized in that: The three-dimensional electromagnetic-thermal-fluid-solid coupling simulation module and the phase change material coupling modeling module share an adaptive meshing unit and support the sweep method, multi-region method or surface mesh method to discretize the model to ensure a balance between calculation accuracy and efficiency.

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