Liquid-cooled cable structure

Abstract

The invention relates to the technical field of liquid-cooled cables, in particular to a liquid-cooled cable structure which comprises a wire bundle composed of a plurality of thin alloy wires. The porous composite layer is arranged outside the wire bundle, the heat conduction insulating layer is arranged outside the porous composite layer, the evaporation cavities and the connection channels are arranged between the porous composite layer and the heat conduction insulating layer, and the first working fluid is arranged in pores of the evaporation cavities, the connection channels and the porous composite layer. The evaporator is used for vaporizing and absorbing heat during local overheating, longitudinally conveying steam and capillary backflow of condensate; the flat cooling channel is arranged outside the heat conduction insulating layer, and a second cooling medium capable of being circulated is arranged in the flat cooling channel. Efficient and reliable heat dissipation is achieved by combining evaporative cooling and forced convection cooling.

Description

Technical Field

[0001] This invention relates to the technical field of liquid-cooled cables, and more specifically, to a liquid-cooled cable structure. Background Technology

[0002] With the rapid development of new energy vehicles, high-power DC charging technology has become crucial for improving charging efficiency. High-power charging means a larger current (e.g., 500A or higher) flows through the charging cable. Traditional charging cables typically use air cooling or natural cooling, but as charging power increases, the copper core conductors (i.e., the conductor bundle) inside the cable generate significant heat due to Joule heating, causing the cable temperature to rise sharply. Excessive temperature not only severely shortens the lifespan of the charging cable insulation material, posing safety hazards, but also triggers over-temperature protection, leading to a decrease in charging power and even causing serious problems such as conductor aging and burnout.

[0003] To address the heat dissipation problem, existing technologies first attempt to reduce resistance by increasing the cable diameter or using thicker wires. However, this significantly increases the size, weight, and cost of the cable, making it extremely bulky and severely reducing user portability and operating experience, while offering limited improvement in heat dissipation.

[0004] Therefore, the industry has turned to active liquid cooling technology. However, existing active liquid-cooled cables still face two major technical problems and limitations when dealing with high-power charging:

[0005] The first problem is the inability to efficiently handle "localized hot spots." In actual use, cables do not heat up uniformly. At cable bends (where internal thin copper wires fracture due to metal fatigue, increasing resistance) or at cable end joints (where terminal oxidation or poor connection increases contact resistance), transient, localized "hot spots" form, with temperatures much higher than other parts of the cable. Existing technologies, such as the dual-channel coolant structure for liquid-cooled cable electrodes in high-power charging piles disclosed in CN109768405A, use an internal cooling copper pipe and an external channel circulating coolant to achieve isolated flow for cooling the cable electrodes and conductors. However, this technology is only single-phase liquid cooling, relies on a pump drive, and cannot utilize the latent heat of phase change to handle transient heat peaks. This results in high thermal resistance at high power levels, a complex structure, no significant reduction in volume, and an inability to solve the problem of uniform cooling inside the conductor.

[0006] The second problem is the limitation of existing liquid cooling systems (single-phase cooling). For example, the liquid-cooled charging cable and charging device disclosed in announcement number CN116959799B describes a cable structure with dual liquid flow channels, which directly cools the inside and outside of the conductor through the liquid outlet of the inner tube. However, it is still limited to single-phase circulation, has no passive phase change mechanism, is easily affected by pump failure, and does not optimize the thermal conductivity anisotropy of the insulation layer, which limits the overall efficiency.

[0007] Therefore, there is an urgent need in this field for a novel hybrid cooling solution. This solution not only requires an active single-phase circulation system to handle the "overall steady-state heating" of the cable; more importantly, it also needs to integrate a passive cooling mechanism inside the cable that can utilize the latent heat of phase change to specifically and efficiently handle unpredictable "local transient hot spots," thereby achieving efficient, compact, and highly reliable thermal management. Summary of the Invention

[0008] Therefore, the purpose of this invention is to provide a liquid-cooled cable structure that solves the problem of performance degradation or even damage caused by overheating of cables in the prior art. By combining evaporative cooling and forced convection cooling, efficient and reliable heat dissipation is achieved.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] A liquid-cooled cable structure, comprising:

[0011] A wire bundle composed of multiple strands of fine alloy wires;

[0012] A porous composite layer disposed on the outside of the wire bundle;

[0013] A thermally conductive insulating layer disposed on the outside of the porous composite layer;

[0014] A plurality of evaporation chambers and connecting channels are disposed between the porous composite layer and the thermally conductive insulating layer;

[0015] The first working fluid is embedded in the pores of the evaporation chamber, the connecting channel and the porous composite layer, and is used for vaporization and heat absorption, longitudinal steam transport and capillary reflux of condensate in the event of local overheating.

[0016] At least one flat cooling channel is disposed outside the thermally conductive insulation layer, and the flat cooling channel contains a recirculating second cooling medium.

[0017] The present invention is further configured such that: the evaporation chamber is a flat ellipsoid with an axial length of 10 to 30 mm and a radial thickness of 3 to 8 mm; the connecting channel consists of at least three main pipes arranged axially with a diameter of 1.5 to 5.0 mm; and the ratio of the length of any evaporation chamber to the diameter of its connected channel is 3:1 to 20:1.

[0018] The present invention is further configured such that the porous composite layer comprises:

[0019] Axial grooves used as low-resistance liquid return channels;

[0020] The pumping layer covering the axial groove is composed of multiple layers of metal wire mesh with a pore size ranging from 20 to 500 µm and a contact angle with the first working fluid of less than 60°.

[0021] The present invention is further configured such that: the thermally conductive insulating layer comprises a silicone rubber electrical insulating layer as an inner layer and a thermally conductive reinforced epoxy layer as an outer layer; the thermally conductive reinforced epoxy layer contains boron nitride sheets that are oriented during the curing process by an electric field, so that the outer layer exhibits anisotropic thermal conductivity, with a radial thermal conductivity ≥3W / m·K and a circumferential thermal conductivity ≤1W / m·K.

[0022] The invention is further configured such that: the radial thickness of the flat cooling channel is 2 to 6 mm and the circumferential width is 6 to 22 mm; the flat cooling channel is provided with axially arranged support ribs inside, which divide the wide channel into at least two parallel sub-channels.

[0023] The present invention is further configured such that: the inner wall of the flat cooling channel is provided with a turbulence structure, the height of the turbulence structure is 0.1 to 0.6 mm, the spacing is 0.3 to 3.0 mm, and the angle with the axial flow direction is 15° to 60°, so as to enhance the convective heat transfer of the second cooling medium.

[0024] The present invention is further configured such that: the conductor bundle adopts a structure of primary twisting in groups of 7 strands and composite twisting, the diameter of a single fine alloy conductor is 0.05 to 0.20 mm, and the twist pitch of the primary twisting is 2 to 10 mm.

[0025] The present invention is further configured such that: the first working fluid is a dielectric refrigerant or an electronic fluorinated liquid, with a boiling point range of 40°C to 100°C at 1 standard atmosphere; the second cooling medium is a water-ethylene glycol mixture or an insulating industrial coolant, and is mixed with microcapsule phase change material with a particle size of 1 to 50 µm and a volume fraction of 1% to 10%, for absorbing transient heat peaks.

[0026] The present invention is further configured such that: the center-to-center spacing of the evaporation chamber along the cable axis is 0.5 to 2 times its axial length, so as to ensure uniform coverage of the evaporation area; and the filling rate defined by the liquid phase volume of the first working fluid and the total volume of the evaporation chamber, the connecting channel and the pores of the porous composite layer is 20% to 60%.

[0027] The invention is further configured to include an electromagnetic shielding layer disposed outside the flat cooling channel; the shielding layer is a multi-layer composite structure, including an inner tin-plated copper mesh with an opening ratio of 30% to 80% and an outer composite thin layer containing carbon-containing microwave absorbing material; the inner tin-plated copper mesh is in thermal contact with the outer wall of the flat cooling channel through a thermally conductive adhesive to assist in heat dissipation.

[0028] It also includes an outer sheath disposed outside the electromagnetic shielding layer, the outer sheath being made of wear-resistant and flame-retardant thermoplastic polyurethane.

[0029] Compared with the shortcomings of the prior art, the beneficial effects of the present invention are as follows:

[0030] This invention constructs a distributed heat pipe network in the core of the cable through the design of a porous composite layer, an evaporation chamber, and a connecting channel. The flat cooling channel has a built-in second cooling medium as an active cooling system, which is responsible for continuously removing the overall steady-state heat load of the cable. When a local hot spot is generated, the first working fluid boils instantaneously at that point, absorbing a huge amount of heat in the form of latent heat of vaporization. The high-temperature steam is then transported at high speed through the connecting channel to the low-temperature zone of the cable for condensation and heat release, achieving rapid cooling. Attached Figure Description

[0031] Figure 1 This is a cross-sectional view of the structure of the present invention;

[0032] Figure 2 This is a flowchart illustrating the principle of the present invention.

[0033] 1. Wire harness; 2. Porous composite layer; 3. Thermally conductive and insulating layer; 4. Evaporation chamber; 5. Connecting channel; 101. First working fluid; 102. Second cooling medium; 6. Flat cooling channel; 7. Electromagnetic shielding layer; 8. Outer sheath; 9. Pumping force layer; 10. Axial groove; 11. Support rib; 12. Turbulence structure. Detailed Implementation

[0034] Reference Figures 1 to 2 The embodiments of the present invention will be further described below.

[0035] This invention provides a liquid-cooled cable structure designed to solve the problem of performance degradation or even damage caused by overheating in existing cables. By combining evaporative cooling and forced convection cooling, it achieves efficient and reliable heat dissipation. The structure mainly includes a conductor bundle 1, a porous composite layer 2, a thermally conductive insulation layer 3, an evaporation chamber 4, a connecting channel 5, a first working fluid 101, a flat cooling channel 6, a second cooling medium 102, an electromagnetic shielding layer 7, and an outer sheath 8.

[0036] Conductor harness 1 is the core current-carrying component of the cable. To balance conductivity and flexibility, and to provide a foundation for subsequent perforated structures, conductor harness 1 employs a primary braiding structure consisting of seven strands per group, followed by composite braiding. The diameter of each individual fine-strand alloy conductor is controlled between 0.05 and 0.20 mm. This small diameter helps to create a more uniform surface area, facilitating good thermal contact with the surrounding perforated structures. The twist pitch of the primary braiding is controlled between 2 and 10 mm. This parameter determines the helixity of each strand within the overall structure. A smaller twist pitch makes conductor harness 1 more compact, which is beneficial for the tight wrapping of subsequent structures and also provides space for the formation of through-holes. The composite braiding structure further enhances the overall mechanical strength and conductivity of conductor harness 1.

[0037] The porous composite layer 2 is disposed on the outside of the wire bundle 1. Its main function is to serve as a storage and transmission channel for the first working fluid 101, and to achieve vaporization and heat absorption in the event of local overheating. This layer includes:

[0038] Axial trenches 10: These trenches, designed as low-resistance liquid reflux channels, run along the cable axis. Their function is to provide a low-resistance flow path for the liquid phase of the first working fluid 101, ensuring that the vapor condensed in the evaporation chamber 4 can smoothly flow back into the pores of the porous composite layer 2, forming capillary reflux. The depth and width of the trenches need to be designed according to the diameter of the lead bundle 1 and the overall structure to ensure sufficient liquid reflux capacity without affecting the encapsulation of subsequent layers.

[0039] Pumping layer 9: Covering the axial groove 10, it is composed of multiple layers of metal wire mesh. Pumping layer 9 is a key component for achieving capillary reflux. Its design principle utilizes the capillary force of porous media. The pore size of the metal wire mesh is controlled within the range of 20 to 500 µm; smaller pore sizes are beneficial for generating stronger capillary forces. Simultaneously, this layer needs to form a contact angle of less than 60° with the first working fluid 101. This hydrophilic (or low hydrophobic) property ensures that the liquid can be effectively adsorbed and permeate upwards (towards the evaporation chamber 4) or laterally (towards the wire bundle 1) along the capillary channels of the wire mesh. The multi-layered wire mesh design increases the number and complexity of capillary channels, improving the reliability and efficiency of liquid reflux. When the wire bundle 1 overheats, the liquid working fluid in the porous composite layer 2 absorbs heat and vaporizes; the vapor is transported upwards through the connecting channel 5. Simultaneously, the condensed liquid working fluid relies on capillary force and gravity (if tilted) to reflux through pumping layer 9 and axial groove 10.

[0040] Evaporation chamber 4 and connecting channel 5 are the core structures for realizing phase change heat absorption and steam transport.

[0041] The evaporation chamber 4 is designed as a flattened ellipsoid with an axial length of 10 to 30 mm and a radial thickness of 3 to 8 mm. This flattened ellipsoidal design maximizes the contact area with the wire harness 1 and the thermally conductive insulation layer 3 while reducing internal fluid resistance. Its axial length is designed to allow for a sufficiently large vaporization zone to absorb locally generated heat.

[0042] The connecting channel 5 consists of four main pipes arranged axially, with diameters ranging from 1.5 to 5.0 mm. These main pipes connect to each evaporation chamber 4, forming a continuous steam transport network. The number of these main pipes is designed to ensure that even if one channel is blocked, other channels can still operate, thus improving system redundancy.

[0043] The ratio of the length of any evaporation chamber 4 to the diameter of its connected channel 5 is 3:1 to 20:1.

[0044] A ratio that is too small (e.g., close to 3:1) means that the evaporation chamber 4 is relatively short, or the connecting channel 5 is relatively wide. This causes the steam to be generated too quickly, while the channel diameter is insufficient to discharge it quickly, resulting in a local pressure increase and affecting the evaporation effect.

[0045] A ratio that is too large (e.g., close to 20:1) means that the evaporation chamber 4 is relatively long, or the connecting channel 5 is relatively narrow. This leads to increased resistance to steam transmission within the channel and reduced heat dissipation efficiency.

[0046] Preferred range (3:1 to 20:1): Within this range, the steam generation rate and transmission rate can be balanced, ensuring that the evaporation chamber 4 can fully utilize the latent heat of phase change, while the steam can be efficiently delivered to the condensation area. When the axial length of the evaporation chamber 4 is 20 mm and the diameter of the connecting channel 5 is 2 mm, the ratio is 10:1, which is an ideal intermediate value.

[0047] The detailed principle is as follows:

[0048] The active cooling circuit consists of a flat cooling channel 6 and a built-in recirculating second cooling medium 102. When the cable is in operation, the cooling unit (including a water pump and radiator, not shown) located outside the cable (inside the charging pile base) drives the second cooling medium 102 (water-glycol mixture) to continuously circulate within the flat cooling channel 6.

[0049] The main functions of this active cooling circuit are:

[0050] It is responsible for continuously absorbing and removing the overall, steady-state base heat load generated by the ohmic resistance of conductor bundle 1, maintaining the average temperature of the cable at a safe base level.

[0051] It provides a necessary condensation zone distributed along the cable axis for the passive cooling circuit of the present invention.

[0052] A passive closed capillary two-phase loop is installed at the core of the cable. The loop consists of a porous composite layer 2, an evaporation chamber 4, a connecting channel 5, and a first working fluid 101 sealed inside.

[0053] The working cycle of this passive loop consists of four steps:

[0054] Boiling (vaporization endothermic): When the lead harness 1 experiences localized overheating due to local defects (such as strand breakage caused by repeated bending, or poor terminal contact), the temperature of this hot spot will instantaneously and significantly exceed the base temperature maintained by the active cooling circuit. The heat will be rapidly conducted through the base of the porous composite layer 2, causing the first working fluid 101, which is immersed in the porous composite layer 2, to reach its boiling point on the inner wall of the evaporation chamber 4 and instantly boil, i.e., vaporize.

[0055] Steam transport (heat transfer): The high-pressure steam generated by boiling in the evaporation chamber 4 immediately rushes into the lower-pressure connecting channel 5. The connecting channel 5 forms a steam highway, enabling high-temperature, high-pressure steam to be transferred instantaneously from the hot spot area to other cold areas of the cable along the cable axis at extremely high speed.

[0056] Condensation (Heat Release): When high-temperature steam flows through the cold zone strongly cooled by the aforementioned active cooling circuit, the steam comes into contact with the low-temperature inner wall of connecting channel 5. Here, the steam condenses back into the liquid phase and releases a huge amount of latent heat of vaporization.

[0057] The heat release path is as follows: first, the heat is transferred from the steam to the inner wall of the connecting channel 5; then, the heat is efficiently transferred through the thermally conductive insulation layer 3, which serves as an isolation layer, by thermal conduction; finally, the heat reaches the outer wall of the flat cooling channel 6, is absorbed by the second cooling medium 102, and is eventually carried away from the cable.

[0058] Capillary reflux (closed-loop circulation): The liquid phase first working fluid 101 generated by condensation will be immediately absorbed and locked by the microporous structure of the porous composite layer 2.

[0059] Low-resistance reflux: The condensed liquid preferentially enters the axial groove 10, whose large cross-section ensures that the liquid can quickly return to the hot spot area along the cable axis with extremely low flow resistance and high flow rate.

[0060] At the hot spot, the pumping layer 9 uses its strong capillary pressure to pump liquid from the axial groove 10 to the boiling surface of the evaporation chamber 4. At the same time, the microporous structure of the pumping layer 9 also acts as a one-way valve, preventing the high-pressure steam boiling in the evaporation chamber 4 from flowing back in and clogging the axial groove 10.

[0061] A thermally conductive and electrically insulating layer 3 is wrapped around the porous composite layer 2, serving to achieve both thermal conductivity and electrical insulation. This layer employs a composite structure.

[0062] Inner layer: Silicone rubber electrical insulation layer. Silicone rubber itself has good electrical insulation properties and a certain degree of flexibility, which can meet the electrical safety requirements of the cable and is tightly bonded to the porous composite layer 2.

[0063] Outer Layer: Thermally Reinforced Epoxy Layer. To improve thermal conductivity, this layer contains uniformly dispersed boron nitride (BN) sheets that are oriented during curing using an electric field. The boron nitride sheets possess excellent thermal conductivity, particularly their layered structure, which results in a significantly higher in-plane thermal conductivity than interlayer thermal conductivity. The electric field-assisted oriented alignment ensures that the primary thermal conduction direction of the BN sheets aligns with the radial direction of the cable. This oriented alignment gives the outer layer anisotropic thermal conductivity. The radial thermal conductivity is ≥3 W / m·K, which is the critical path for transferring heat from the cable's interior to the exterior. The circumferential thermal conductivity is ≤1 W / m·K. Although the circumferential thermal conductivity is relatively low, the high radial thermal conductivity is sufficient to ensure rapid heat dissipation. This design prioritizes heat dissipation in the radial direction, rather than excessive diffusion in the circumferential direction.

[0064] At least one flat cooling channel 6 is disposed on the outside of the thermally conductive insulation layer 3, with a built-in recirculating second cooling medium 102 to provide active forced convection cooling. The radial thickness is 2 to 6 mm, and the circumferential width is 6 to 22 mm. The flat structural design allows it to better conform to the curvature of the cable without excessively increasing the overall outer diameter of the cable.

[0065] The channel is equipped with axially arranged support ribs 11, which divide the wide channel into at least two parallel sub-channels. The function of the support ribs 11 is twofold: first, to provide structural support and prevent the channel from deforming under pressure; second, to divide the flowing second cooling medium 102 into smaller flow channels, increase the contact area between the fluid and the heat exchange surface, and induce more complex flow patterns, thereby improving heat exchange efficiency.

[0066] The inner wall of the flat cooling channel 6 is provided with turbulence structures 12, with a height of 0.1 to 0.6 mm, a spacing of 0.3 to 3.0 mm, and an angle of 15° to 60° with the axial flow direction. The purpose of the turbulence structures 12 is to enhance the convective heat transfer of the second cooling medium 102. When the cooling medium flows over these tiny protrusions, eddies are generated behind them, disrupting the boundary layer and increasing the turbulence of the fluid, thereby significantly improving the convective heat transfer coefficient between the cooling medium and the inner wall of the channel. The angle design can be optimized according to the specific flow velocity and medium characteristics to achieve the best turbulence effect.

[0067] First working fluid 101: A dielectric refrigerant or electronic fluorinated liquid is selected. These substances have good dielectric properties, will not cause short circuit risks to the circuit, and have a suitable boiling point range. Its boiling point range at 1 standard atmosphere is set from 40°C to 100°C.

[0068] Preferred range: If the boiling point is too low (e.g., <40°C), vaporization will occur frequently at room temperature or low temperature, leading to system instability or requiring a stronger cold source to maintain condensation.

[0069] If the boiling point is too high (e.g., >100°C), it cannot effectively vaporize and absorb heat within the normal operating temperature range of the cable, and thus cannot achieve the effect of phase change cooling.

[0070] The 40°C to 100°C range covers the typical overheating temperature range of cables under high current loads, achieving efficient phase change heat absorption. Using a fluid with a boiling point of 60°C, vaporization and heat absorption begin when the local temperature reaches 60°C, resulting in significant effects.

[0071] Second cooling medium 102: Water-ethylene glycol mixture or insulating industrial coolant are selected. These media have good thermal conductivity and fluidity, and have certain antifreeze and anti-corrosion capabilities.

[0072] To cope with transient heat peaks, the second cooling medium 102 is infused with microcapsule phase change material with a particle size of 1 to 50 µm and a volume fraction of 1% to 10%. These microcapsules are filled with substances capable of undergoing phase change within a specific temperature range (such as paraffin or salt hydrates). When the cable experiences transient overheating due to a short-term high current, these microcapsules can absorb a large amount of latent heat, "flattening" the temperature peak and providing a buffer time for the phase change process of the first working fluid 101 or the overall cooling of the second cooling medium 102, further improving the thermal stability of the system.

[0073] The particle size of 1-50µm ensures that the microcapsules do not easily settle and can be uniformly dispersed in the cooling medium.

[0074] A volume fraction of 1%-10% can provide considerable transient heat storage capacity without significantly affecting the hydrodynamic and thermal conductivity properties of the cooling medium.

[0075] The center-to-center spacing of the evaporation chamber 4 along the cable axis is 0.5 to 2 times its axial length.

[0076] If the spacing is too small (<0.5 times the length) and the evaporation chambers 4 are too dense, the steam generation area will be too concentrated, the pressure in the steam discharge channel will increase, or the heat transfer between adjacent evaporation chambers 4 will be insufficient.

[0077] Excessive spacing (>2 times the length) in the evaporation chamber 4 leads to a lack of direct phase change cooling in some areas, resulting in heat accumulation.

[0078] A ratio of 0.5 to 2 times ensures that the evaporation area can uniformly cover the cable length and provides sufficient space between the evaporation chambers 4 for structural support and heat transfer, while avoiding excessive overlap that would reduce efficiency.

[0079] The filling rate, defined by the liquid phase volume of the first working fluid 101 and the total volume of the evaporation chamber 4, the connecting channel 5, and the pores of the porous composite layer 2, is 20% to 60%.

[0080] If the filling rate is too low (<20%), the total fluid volume is insufficient, which cannot guarantee that the liquid phase can be fully supplied in all evaporation zones, resulting in dry burning in some areas.

[0081] An excessively high filling rate (>60%) will result in too much liquid phase occupying the evaporation and transport space, restricting the generation and flow of steam, increasing system pressure, and preventing heat from being effectively transferred to the condensation zone.

[0082] A range of 20% to 60% provides ample space for fluid to transition between the liquid and gas phases, ensuring efficient evaporation, transport, and condensation cycles while avoiding issues of insufficient or excessive space, thus guaranteeing system stability and optimal performance.

[0083] An electromagnetic shielding layer 7 is disposed outside the flat cooling channel 6. Its design aims to suppress electromagnetic interference (EMI) and assist in heat dissipation. It is also a multi-layer composite structure.

[0084] Inner layer: Tin-plated copper mesh with an aperture ratio of 30% to 80%. Tin-plated copper mesh offers excellent conductivity and electromagnetic shielding effectiveness. The aperture design allows for some airflow, but its primary function is to form a conductive shielding layer. The choice of aperture ratio balances shielding effectiveness with weight / flexibility.

[0085] Outer layer: A thin composite layer containing carbon-based absorbing material. The absorbing material can absorb some of the incident electromagnetic wave energy, further improving the shielding effect, especially against high-frequency electromagnetic waves.

[0086] Thermal contact: The inner tin-plated copper mesh is in thermal contact with the outer wall of the flat cooling channel 6 via thermally conductive adhesive. This is crucial for the heat dissipation of this layer. The thermally conductive adhesive not only provides a mechanical connection but, more importantly, provides a low thermal resistance heat transfer path, transferring some of the heat from the wall of the flat cooling channel 6 through the tin-plated copper mesh, further enhancing heat dissipation.

[0087] The outer sheath 8 is the outermost layer of protection for the entire liquid-cooled cable structure. It is made of abrasion-resistant and flame-retardant thermoplastic polyurethane (TPU). TPU material provides excellent abrasion resistance, oil resistance, and chemical corrosion resistance, enabling it to adapt to complex industrial environments. Its flame-retardant properties ensure the cable's safety and prevent the spread of fire.

[0088] To verify the heat dissipation performance of this invention, we conducted a series of experiments. The liquid-cooled cable of this invention was compared with cables of the same specifications (rated current, conductor cross-sectional area) using traditional air-cooling or water-cooling methods.

[0089] Test subject:

[0090] Example 1: The liquid-cooled cable of the present invention (comprising a first working fluid and a second cooling medium).

[0091] Control group 1: Bare cables of the same specifications but with traditional silicone rubber insulation and outer sheath, which were heated naturally by increasing the current.

[0092] Control group 2: Cables of the same specifications but using a traditional air-cooling device (forced air cooling).

[0093] Control group 3: Cables of the same specifications but using traditional water-cooled sleeves (externally forced water cooling).

[0094] Test environment: ambient temperature 25°C, humidity 50%.

[0095] Heating method: Different currents (100A, 200A, 300A, 400A) were passed through the inside of the cable, and the steady-state temperature under each current was recorded.

[0096] Temperature monitoring: High-precision temperature sensors are placed at key locations such as the surface of the cable conductor bundle, the surface of the thermally conductive insulation layer, and the outer wall of the cooling channel.

[0097] Performance testing methods:

[0098] Steady-state temperature test: Apply a constant current and wait for the cable temperature to stabilize (temperature change rate less than 0.1°C / min), then record the temperature at each point.

[0099] Overload capacity test: After stabilizing at the rated current for a period of time, increase the current to 150% of the rated current for a short period of time (e.g., 10 minutes), and monitor the temperature change and whether the overheat protection threshold is reached.

[0100] Thermal resistance test: Calculate the thermal resistance under different operating conditions. Thermal resistance = (conductor temperature - ambient temperature) / current.

[0101] The experimental results are shown in Table 1:

[0102] Current (A) Example 1: Steady-state temperature (°C) Steady-state temperature (°C) of control group 1 Steady-state temperature (°C) of control group 2 Control group 3 steady-state temperature (°C) 100 45 65 58 52 200 60 90 75 68 300 75 120 95 85 400 90 155 (overheated) 115 105

[0103] Overload capacity test results:

[0104] Example 1: The steady-state temperature is 75°C under rated current. When overloaded to 400A, the temperature rises to 105°C within 10 minutes, but the overheat protection is not triggered.

[0105] Control group 3: The steady-state temperature is 85°C under rated current. When overloaded to 400A, the temperature rises to 130°C within 5 minutes, triggering overheat protection.

[0106] Experimental data show that the liquid-cooled cable structure of this invention exhibits significant temperature advantages under different currents. At a current of 300A, the steady-state temperature of Example 1 is 45°C lower than that of Control Group 1 (bare wire), 20°C lower than that of Control Group 2 (air-cooled), and 10°C lower than that of Control Group 3 (water-cooled bushing). At a current of 400A, the bare wire overheats, while the structure of this invention still operates stably. Overload capacity tests also demonstrate that the structure of this invention has stronger robustness in dealing with transient high heat loads. This is mainly attributed to its design combining efficient phase change cooling and forced convection cooling, as well as its optimized heat conduction path.

[0107] To more comprehensively evaluate the effects of the present invention, we set up the following control group:

[0108] Control Group A (without phase change cooling): The first working fluid was replaced with ordinary insulating oil, the evaporation chamber and connecting channels were removed, and only the wire harness, porous composite layer (as lubrication and auxiliary filling), thermally conductive insulation layer, and flat cooling channels were retained. This control group was designed to verify the contribution of phase change cooling (evaporative cooling) to overall heat dissipation.

[0109] Control Group B (Forced Convection Cooling Removed): The flat cooling channel and the second cooling medium were removed, leaving only the wire harness, porous composite layer, thermally conductive insulation layer, evaporation chamber, connecting channel, and first working fluid. This control group was designed to verify the effectiveness of purely passive evaporative cooling.

[0110] Control group C (reducing the thermal conductivity of the thermally conductive insulating layer): The content or orientation of boron nitride flakes in the thermally conductive reinforced epoxy layer was reduced, causing its radial thermal conductivity to drop below 1 W / m·K. This control group aims to verify the effect of the oriented boron nitride layer on improving radial heat dissipation.

[0111] Control group D (simplified turbulence structure): The turbulence structure on the inner wall of the flat cooling channel was removed, leaving only the smooth inner wall. This control group aims to verify the enhancing effect of the turbulence structure on the convective heat transfer of the second cooling medium.

[0112] The following will list several embodiments and corresponding control experiments focusing on the core parameters, in order to more clearly demonstrate the optimization range and effect of the parameters.

[0113] 1. Core parameters: Boiling point of the first working fluid and the ratio of axial length of the evaporation chamber to the diameter of the connecting channel.

[0114] Example 1: The boiling point of the first working fluid is 60°C, the axial length of the evaporation chamber is 20mm, and the diameter of the connecting channel is 2mm (ratio 10:1). The boiling point is moderate, and the size ratio of the evaporation chamber to the channel is well-coordinated, which is expected to result in high heat dissipation efficiency and good stability.

[0115] Example 2: The boiling point of the first working fluid is 40°C, the axial length of the evaporation chamber is 15mm, and the diameter of the connecting channel is 3mm (ratio 5:1). The low boiling point allows phase change to be initiated at a lower temperature, and the relatively large channel facilitates rapid steam discharge.

[0116] Example 3: The boiling point of the first working fluid is 90°C, the axial length of the evaporation chamber is 30mm, and the diameter of the connecting channel is 1.5mm (ratio 20:1). The higher boiling point requires a higher local temperature to initiate the phase change, the longer evaporation chamber, and the relatively narrower channel demand higher steam transfer capacity.

[0117] Comparative Example 1 (Boiling Point Too Low): The boiling point of the first working fluid is 25°C. At normal operating temperature, the working fluid frequently vaporizes, causing system instability and even affecting other components due to excessive pressure.

[0118] Comparative Example 2 (Boiling Point Too High): The boiling point of the first working fluid is 120°C. At typical cable overheating temperatures, the working fluid cannot vaporize effectively, and the phase change cooling effect is not obvious, relying mainly on heat conduction and forced convection.

[0119] Comparison with Example 3 (ratio too small): Evaporation chamber axial length 10mm, connecting channel diameter 5mm (ratio 2:1). Steam is generated too quickly, and the channel cannot clear it in time, resulting in local pressure increase and affecting evaporation efficiency.

[0120] Comparison with Example 4 (ratio too large): Evaporation chamber axial length 30mm, connecting channel diameter 1mm (ratio 30:1). Increased steam transmission resistance leads to increased energy loss during transmission and decreased overall heat dissipation efficiency.

[0121] 2. Core parameters: Porous composite layer pump force layer wire mesh aperture and contact angle

[0122] Example 4: The pump force layer has a wire mesh aperture of 50µm and a contact angle of 30° with the first working fluid. The small aperture results in strong capillary force, a small contact angle, and good hydrophilicity, and the capillary reflux effect is expected to be optimal.

[0123] Example 5: The mesh size of the pump force layer is 200µm, and the contact angle with the first working fluid is 50°. Both the mesh size and the contact angle are in the middle range, balancing capillary force and flow rate.

[0124] Example 6: The mesh size of the pump layer is 400µm, and the contact angle with the first working fluid is 60°. The mesh size is relatively large, and the resistance to liquid backflow is slightly large. The contact angle is close to the upper limit, but effective backflow can still be achieved.

[0125] Comparison Example 5 (excessively large aperture): The mesh aperture of the pump layer is 800µm, which significantly weakens the capillary force, making liquid phase reflux difficult, resulting in insufficient liquid in the evaporation chamber and affecting the continuous phase change cooling.

[0126] Comparative Example 6 (excessive contact angle): The mesh size of the pump layer is 100µm, and the contact angle with the first working fluid is 80°. The liquid and the mesh surface are difficult to wet, and the capillary force is insufficient to support the liquid phase reflux, or the reflux efficiency is extremely low.

[0127] 3. Core parameters: the degree of directional arrangement of boron nitride in the thermally conductive insulating layer and the parameters of the flat cooling channel turbulence structure.

[0128] Example 7: Boron nitride sheets are radially oriented, with a radial thermal conductivity of 3.5 W / m·K. The turbulence structure has a height of 0.3 mm, a spacing of 1.0 mm, and an included angle of 30°. The boron nitride sheets are highly oriented, resulting in high radial thermal conductivity. The turbulence structure is moderate and effectively enhances convective heat transfer.

[0129] Example 8: Boron nitride sheets are partially oriented, with a radial thermal conductivity of 2.8 W / m·K. The turbulence structure has a height of 0.5 mm, a spacing of 0.5 mm, and an included angle of 50°, with slightly weaker orientation of the boron nitride sheets. The turbulence structure is denser and has a steeper angle, aiming to maximize convective heat transfer.

[0130] Example 9: The boron nitride sheet is highly oriented with a radial thermal conductivity of 4.0 W / m·K. The turbulence structure has a height of 0.1 mm, a spacing of 3.0 mm, and an included angle of 15°. The boron nitride sheet exhibits optimal orientation and the highest thermal conductivity. The turbulence structure is shallow and sparse with a small angle, aiming to gently enhance convective heat transfer.

[0131] Comparative Example 7 (disordered boron nitride dispersion): The boron nitride sheets in the thermally conductive insulating layer are randomly distributed, with a radial thermal conductivity of 1.5 W / m·K. The radial thermal conductivity is greatly reduced, and the outward transfer of heat is hindered.

[0132] Compared to Example 8 (with the removal of the turbulence structure): the inner wall of the flat cooling channel is smooth and there is no turbulence structure. The convective heat transfer efficiency of the second cooling medium is significantly reduced, resulting in insufficient heat dissipation capacity.

[0133] Compare with Example 9 (inappropriate turbulence structure parameters): The height of the turbulence structure is 0.05 mm, the spacing is 4.0 mm, and the included angle is 5°. The turbulence structure is too shallow or too sparse, and the effect of enhancing convective heat transfer is not obvious.

[0134] 4. Core parameters: First working fluid filling rate and second cooling medium microcapsule phase change material parameters.

[0135] Example 10: The first working fluid has a charge rate of 40%. The second cooling medium is mixed with microcapsules with a particle size of 10µm and a volume fraction of 5%. The charge rate and microcapsule parameters are both within the recommended range, providing good heat capacity and transient suppression capability.

[0136] Example 11: The first working fluid has a charge rate of 25%. The second cooling medium is mixed with microcapsules with a particle size of 30µm and a volume fraction of 10%. The charge rate is relatively low, requiring a higher microcapsule concentration to compensate for the transient heat absorption capacity.

[0137] Example 12: The first working fluid filling rate is 55%. The second cooling medium is mixed with microcapsules with a particle size of 5µm and a volume fraction of 1%, resulting in a relatively high filling rate and sufficient total fluid volume. The microcapsule concentration and particle size are relatively low, relying mainly on phase change cooling and convective heat transfer of the fluid itself.

[0138] Comparative Example 10 (Insufficient Filling Rate): The first working fluid filling rate is 10%, which is insufficient, resulting in dry burning in some areas and failure of phase change cooling.

[0139] Comparative Example 11 (overfilling rate): The first working fluid filling rate is 80%, which restricts space, affects steam generation and flow, and increases system pressure.

[0140] Comparative Example 12 (without microcapsules): The second cooling medium is not mixed with microcapsules. When dealing with transient heat peaks, the temperature rises faster and the system stability decreases.

[0141] Comparative Example 13 (Inappropriate Microcapsule Parameters): The second cooling medium is mixed with microcapsules with a particle size of 100µm and a volume fraction of 20%. The excessively large particle size leads to sedimentation, and the excessively high volume fraction increases fluid resistance and affects circulation.

[0142] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any ordinary changes and substitutions made by those skilled in the art within the scope of the technical solution of the present invention should be included within the protection scope of the present invention.

Claims

1. A liquid-cooled cable structure, characterized in that, include: A wire bundle composed of multiple strands of fine alloy wires; A porous composite layer disposed on the outside of the wire bundle; A thermally conductive insulating layer disposed on the outside of the porous composite layer; A plurality of evaporation chambers and connecting channels are disposed between the porous composite layer and the thermally conductive insulating layer; The first working fluid is built into the pores of the evaporation chamber, connecting channel and porous composite layer, and is used for vaporization heat absorption, longitudinal steam transport and capillary reflux of condensate in the event of local overheating. At least one flat cooling channel is disposed outside the thermally conductive insulation layer, and the flat cooling channel contains a recirculating second cooling medium.

2. The liquid-cooled cable structure according to claim 1, characterized in that: The evaporation chamber is a flat ellipsoid with an axial length of 10 to 30 mm and a radial thickness of 3 to 8 mm; the connecting channel consists of at least three main pipes arranged axially with a diameter of 1.5 to 5.0 mm; and the ratio of the length of any evaporation chamber to the diameter of its connected channel is 3:1 to 20:

1.

3. The liquid-cooled cable structure according to claim 1, characterized in that: The porous composite layer comprises: Axial grooves used as low-resistance liquid return channels; The pumping layer covering the axial groove is composed of multiple layers of metal wire mesh with a pore size ranging from 20 to 500 µm and a contact angle with the first working fluid of less than 60°.

4. The liquid-cooled cable structure according to claim 1, characterized in that: The thermally conductive insulating layer includes an inner silicone rubber electrical insulating layer and an outer thermally conductive reinforced epoxy layer. The thermally conductive reinforced epoxy layer contains boron nitride sheets that are oriented during the curing process by an electric field, making the outer layer exhibit anisotropic thermal conductivity with a radial thermal conductivity ≥3W / m·K and a circumferential thermal conductivity ≤1W / m·K.

5. The liquid-cooled cable structure according to claim 1, characterized in that: The flat cooling channel has a radial thickness of 2 to 6 mm and a circumferential width of 6 to 22 mm; the flat cooling channel is provided with axially arranged support ribs inside, which divide the wide channel into at least two parallel sub-channels.

6. The liquid-cooled cable structure according to claim 5, characterized in that: The inner wall of the flat cooling channel is provided with a turbulence structure. The height of the turbulence structure is 0.1 to 0.6 mm, the spacing is 0.3 to 3.0 mm, and the angle with the axial flow direction is 15° to 60°, so as to enhance the convective heat transfer of the second cooling medium.

7. The liquid-cooled cable structure according to claim 1, characterized in that: The conductor bundle adopts a structure of primary twisting in groups of 7 strands and composite twisting. The diameter of a single fine-strand alloy conductor is 0.05 to 0.20 mm, and the twist pitch of the primary twisting is 2 to 10 mm.

8. The liquid-cooled cable structure according to claim 1, characterized in that: The first working fluid is a dielectric refrigerant or an electronic fluorinated liquid, with a boiling point range of 40°C to 100°C at 1 standard atmosphere. The second cooling medium is a water-ethylene glycol mixture, which contains microcapsule phase change material with a particle size of 1 to 50 µm and a volume fraction of 1% to 10%, for absorbing transient heat peaks.

9. The liquid-cooled cable structure according to claim 1, characterized in that: The center-to-center spacing of the evaporation chambers along the cable axis is 0.5 to 2 times its axial length to ensure uniform coverage of the evaporation area; and the filling rate, defined by the liquid phase volume of the first working fluid and the total volume of the evaporation chambers, the connecting channels and the pores of the porous composite layer, is 20% to 60%.

10. A liquid-cooled cable structure according to claim 1, characterized in that: It also includes an electromagnetic shielding layer disposed outside the flat cooling channel; the shielding layer is a multi-layer composite structure, including an inner tin-plated copper mesh with an opening ratio of 30% to 80% and an outer composite thin layer containing carbon-containing microwave absorbing material; the inner tin-plated copper mesh is in thermal contact with the outer wall of the flat cooling channel through a thermally conductive adhesive to assist in heat dissipation; It also includes an outer sheath disposed outside the electromagnetic shielding layer, the outer sheath being made of wear-resistant and flame-retardant thermoplastic polyurethane.

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