Composite phase change material and liquid cooling coupled thermal management device

Abstract

The application discloses a kind of composite phase change material and liquid cooling coupling heat management device, including battery module, composite phase change material layer, liquid cooling component, heat conduction fin group, state sensing unit and regulation unit.Composite phase change material layer fills in the gap between battery monomer and module periphery, and liquid cooling pipeline is embedded therein and is provided with radial fin.State sensing unit detects the temperature and liquid volume fraction of composite phase change material layer in real time, and regulation unit adjusts cooling liquid flow and inlet temperature according to average temperature and average liquid volume fraction: low flow and low liquid phase temperature, high flow and high liquid phase temperature, moderate state maintains operation.The application realizes the deep coupling of phase change heat storage and liquid cooling heat dissipation, with high heat dissipation efficiency, good temperature uniformity and low energy consumption.

Description

Technical Field

[0001] This invention relates to the field of battery thermal management technology, specifically to a composite phase change material coupled with liquid cooling thermal management device. Background Technology

[0002] With the continuous improvement of energy density and charge / discharge rate of lithium-ion batteries, a large amount of heat is generated during operation. If it cannot be dissipated in a timely and effective manner, it will lead to problems such as excessively high battery temperature and uneven temperature distribution, which will seriously affect the battery's safety, cycle life and power performance.

[0003] Among the current mainstream battery thermal management technologies, liquid cooling technology has high heat dissipation efficiency, but a single liquid cooling system has a lag in response to instantaneous thermal shock and is prone to causing excessive temperature differences inside the battery module. Phase change material cooling utilizes latent heat to absorb heat and has small temperature fluctuations, but it has a low thermal conductivity and loses its heat storage capacity after complete phase change, making it unable to cope with continuous high heat loads.

[0004] Researchers have proposed schemes for coupling phase change materials (PCMs) with liquid cooling, such as setting finned structures around the battery periphery and placing liquid cooling plates around the fins filled with PCMs. However, such schemes suffer from insufficient thermal coupling efficiency between the PCMs and the liquid cooling plates, and lack the ability to sense and control the state of the PCMs. Furthermore, most existing devices are structurally complex and difficult to assemble, and the PCMs experience leakage and volume changes during repeated phase transitions, resulting in insufficient long-term reliability. Summary of the Invention

[0005] This invention provides a composite phase change material coupled with liquid cooling thermal management device, which can be applied to the thermal management of electric vehicle power battery packs and energy storage system battery modules.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a composite phase change material coupled with liquid cooling thermal management device, comprising:

[0007] A battery module is composed of several battery cells arranged with gaps, with the gap between adjacent battery cells being 8mm to 15mm.

[0008] A composite phase change material layer is filled in the gaps between adjacent battery cells and in the space between the outer periphery of the battery module and the casing; the composite phase change material layer is composed of a phase change matrix material and a highly thermally conductive porous framework, and the phase change temperature of the phase change matrix material is 45°C to 60°C.

[0009] The liquid cooling assembly includes multiple liquid cooling pipes embedded within the composite phase change material layer. The outer diameter of each liquid cooling pipe is 3mm to 6mm. The liquid cooling pipes are connected in parallel at the coolant inlet and converge in parallel at the coolant outlet. The flow path length of each liquid cooling pipe is equal. Each liquid cooling pipe extends in a serpentine manner in a horizontal plane. The outer circumferential surface of each liquid cooling pipe is in contact with the composite phase change material layer. Circulating coolant flows through the liquid cooling pipe.

[0010] A heat-conducting fin assembly includes multiple heat-conducting fins, one end of which is fixedly connected to the outer wall of the liquid cooling pipe, and the other end extends radially outward along the liquid cooling pipe into the interior of the composite phase change material layer; 4 to 8 heat-conducting fins are evenly arranged circumferentially on the same cross-section of the liquid cooling pipe.

[0011] A state sensing unit, disposed inside the composite phase change material layer, includes multiple temperature sensors and multiple capacitive phase change sensors for real-time detection of temperature and phase change state at multiple locations within the composite phase change material layer. The phase change state is characterized by liquid phase volume fraction. At least one temperature sensor is arranged at the top, middle, and bottom of each cell along the height direction of the cell in the gap between every two adjacent cell segments. At least one capacitive phase change sensor is arranged in each gap between every two adjacent cell segments.

[0012] The control unit is connected to the state sensing unit and the circulation pump signal of the liquid cooling assembly, respectively. The control unit adjusts the speed of the circulation pump to control the coolant flow rate and adjusts the cooling power of the heat exchanger to control the coolant inlet temperature based on the temperature signal and liquid volume fraction signal fed back by the state sensing unit.

[0013] The control unit is configured to: obtain the arithmetic mean of all temperature sensor detection values ​​as the average temperature, and obtain the arithmetic mean of all capacitive phase change sensor detection values ​​as the average liquid volume fraction.

[0014] When the average temperature is lower than the lower limit of the phase change temperature of the phase change matrix material and the average liquid volume fraction is lower than 20%, the control unit simultaneously reduces the coolant flow rate and increases the coolant inlet temperature.

[0015] When the average temperature is higher than the upper limit of the phase change temperature of the phase change matrix material or the average liquid volume fraction is higher than 80%, the control unit simultaneously increases the coolant flow rate and decreases the coolant inlet temperature.

[0016] When the average temperature is within the phase change temperature range of the phase change matrix material and the average liquid volume fraction is 20% to 80%, the control unit maintains the current operating parameters;

[0017] Specifically, when the average temperature fluctuates within the range of 2°C below the lower limit of the phase transition temperature to 2°C above the upper limit of the phase transition temperature, and the absolute value of the average rate of change calculated with a time window of 1 minute is less than 0.5°C / min, the control unit does not perform any adjustment operation.

[0018] Preferably, the high thermal conductivity porous skeleton is a foamed metal or graphite foam, the porosity of the high thermal conductivity porous skeleton is 85% to 98%, the pore size is 0.1 mm to 2 mm, and it is an open-cell structure; the phase change matrix material is filled into the pores of the porous skeleton by vacuum impregnation.

[0019] Preferably, the same liquid cooling pipe has different pipe densities in different battery gap sections. The pipe density is set differently according to the heat load distribution determined by the thermal simulation results of the battery module under a predetermined charge and discharge rate. The pipe density is greater in sections with higher heat load.

[0020] Preferably, the heat-conducting fins are spaced apart along the extension direction of the liquid cooling pipe, and the spacing between adjacent heat-conducting fins along the extension direction of the pipe is 10mm to 50mm; the thickness of the heat-conducting fins is 0.5mm to 3mm, and the radial extension length of the fins is 1 / 4 to 1 / 2 of the vertical distance from the outer wall of the liquid cooling pipe to the edge of the composite phase change material layer.

[0021] Preferably, the capacitive phase change sensor calculates the liquid volume fraction by detecting the change in dielectric constant of the composite phase change material. The correspondence between the dielectric constant and the liquid volume fraction is obtained by performing differential scanning calorimetry and dielectric spectrum calibration on the composite phase change material beforehand.

[0022] Preferably, the outer wall of the liquid cooling pipe is provided with a microgroove structure. The cross-sectional shape of the microgroove structure is V-shaped or U-shaped, the groove depth is 0.1mm to 0.5mm, the groove width is 0.2mm to 1mm, the spacing between adjacent grooves is 0.5mm to 2mm, and the microgroove extends along the axial direction of the liquid cooling pipe.

[0023] Preferably, it further includes a thermal insulation layer disposed between the outer side of the composite phase change material layer and the shell, wherein the thermal conductivity of the thermal insulation layer is not higher than 0.05 W / (m·K).

[0024] Preferably, thermally conductive insulating pads are provided on all contact interfaces between the composite phase change material layer and each of the battery cells. The thickness of the thermally conductive insulating pads is 0.5 mm to 3 mm, the thermal conductivity is not less than 1 W / (m·K), and the breakdown voltage is not less than 5 kV.

[0025] 9. A battery pack, characterized in that it includes a composite phase change material and a liquid-cooled coupled thermal management device as described in any one of claims 1 to 8.

[0026] The beneficial effects of this invention are as follows: it organically couples the passive heat storage and temperature equalization function of composite phase change materials with the active enhanced heat dissipation function of liquid cooling. A high thermal conductivity porous framework improves the thermal conductivity of the phase change material, while liquid cooling pipes promptly remove the heat absorbed by the phase change material, achieving the "regeneration" and recycling of the phase change material. This invention achieves real-time sensing of the phase change material's state and intelligent adaptive adjustment of the cooling strategy through a state sensing unit and a control unit, improving heat dissipation efficiency while reducing pump power consumption. In this invention, the liquid cooling pipes have a higher pipe density in areas with high heat load, achieving targeted enhanced heat dissipation and improving the temperature uniformity inside the battery module. The thermally conductive fins increase the heat exchange area between the liquid cooling pipes and the composite phase change material, shortening the heat transfer path and improving thermal coupling efficiency. The liquid cooling pipes are embedded inside the composite phase change material, resulting in high space utilization and easy modular integration. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the internal structure of the present invention;

[0029] Figure 2 This is a schematic diagram of the structure between the two battery cells of the present invention;

[0030] Figure 3 This is a schematic diagram of the cross-sectional structure of the heat-conducting fins of the present invention.

[0031] In the diagram: 1. Battery cell; 2. Composite phase change material layer; 3. Liquid cooling pipe; 4. Coolant inlet; 5. Coolant outlet; 6. Thermal conductive fins; 7. Temperature sensor; 8. Capacitive phase change sensor; 9. Control unit; 10. Circulation pump. Detailed Implementation

[0032] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Example 1

[0034] like Figure 1 , Figure 2 , Figure 3 As shown, a composite phase change material coupled with liquid cooling thermal management device includes a housing and a battery module, a composite phase change material layer 2, a liquid cooling component, 6 sets of heat-conducting fins, a status sensing unit, and a control unit 9 disposed inside the housing.

[0035] The battery module consists of several square lithium-ion battery cells 1 arranged in a matrix, with a gap of 10mm between adjacent battery cells 1. The battery cells 1 are connected in series or in parallel through busbars to form a battery module of predetermined capacity.

[0036] The composite phase change material layer 2 fills all the gaps between adjacent battery cells 1, as well as all the space between the outer periphery of the battery module and the casing, so that the composite phase change material layer 2 completely wraps each battery cell 1.

[0037] The composite phase change material layer 2 is composed of a phase change matrix material and a highly thermally conductive porous framework. In this embodiment, the phase change matrix material is paraffin wax, with a phase change temperature range of 47°C to 50°C and a latent heat of phase change of 210 kJ / kg. This material is solid at room temperature, and absorbs heat to undergo a solid-liquid phase change when the battery operating temperature reaches its phase change temperature, utilizing the latent heat to store a large amount of thermal energy without significantly increasing the temperature.

[0038] The high thermal conductivity porous framework is made of copper foam with a porosity of 92% and a pore size of 0.5 mm, forming a three-dimensional interconnected open-cell structure. The copper foam framework material is pure copper with a thermal conductivity of approximately 380 W / (m·K).

[0039] The preparation method of composite phase change material layer 2 is as follows:

[0040] Copper foam was shaped to match the dimensions of the battery module gaps and peripheral space, and placed in a mold. The mold was then placed in a vacuum impregnation apparatus, and a vacuum was drawn to a level not lower than -0.095 MPa and maintained for 30 minutes to remove air from the pores of the copper foam. Paraffin wax was heated to 80°C until completely melted, and then slowly poured into the mold under vacuum until the copper foam was completely submerged. Vacuum impregnation was maintained for 60 minutes to allow the paraffin wax to fully fill the pores of the copper foam. Afterward, the mixture was cooled to room temperature at a rate of 2°C per minute, and the paraffin wax solidified in the pores of the copper foam, obtaining a composite phase change material. The composite phase change material was then cut and trimmed to match its dimensions to the filling space. Testing showed that the equivalent thermal conductivity of the composite phase change material prepared using the above method was 4.5 W / (m·K), which is 22 times that of pure paraffin wax, whose thermal conductivity is approximately 0.2 W / (m·K).

[0041] The liquid cooling assembly includes multiple liquid cooling pipes 3 embedded within the composite phase change material layer 2. Each liquid cooling pipe 3 is a copper circular tube with an outer diameter of 5 mm and a wall thickness of 0.5 mm. The liquid cooling pipes 3 are connected in parallel at the coolant inlet end 4 via an inlet manifold, and connected in parallel at the coolant outlet end 5 via an outlet manifold. The inlet manifold connects to the outlet of the circulating pump 10, and the outlet manifold connects to the inlet of the heat exchanger. The total flow path length of each liquid cooling pipe 3 from the inlet manifold to the outlet manifold is equal to ensure that the flow resistance of each parallel branch is the same, and that the coolant flow rate is evenly distributed in each branch.

[0042] Each liquid cooling pipe 3 is arranged along the centerline of the gap between adjacent battery cells 1, extending in a serpentine pattern in the horizontal plane. This serpentine pattern refers to the liquid cooling pipe 3 repeatedly bending along the length of the battery module in the horizontal plane, forming multiple U-shaped bends. This allows the pipe to achieve a longer flow path length within the limited space between the batteries, thereby increasing the heat exchange area and coolant residence time. In this embodiment, the turning radius of the serpentine pattern is 20mm, which is four times the outer diameter of the liquid cooling pipe 3, to ensure smooth processing at the bends and moderate flow resistance.

[0043] The outer circumference of the liquid cooling pipe 3 is in direct contact with the composite phase change material layer 2, meaning the liquid cooling pipe 3 is completely encased by the composite phase change material layer 2. The minimum distance between the outer wall of the liquid cooling pipe 3 and the surface of the adjacent battery cell 1 is 2.5 mm. This distance is obtained by subtracting the pipe's outer diameter of 5 mm from the gap of 10 mm and then dividing by 2. This ensures that the pipe will not contact the surface of the battery cell 1 within the manufacturing tolerance range, while also ensuring that there is sufficient phase change material around the pipe for heat exchange.

[0044] One end of the liquid cooling pipe 3 is the flow channel inlet, and the other end is the flow channel outlet. The coolant flows in from the flow channel inlet, passes through the serpentine flow channel, and flows out from the flow channel outlet. The coolant is an antifreeze mixture of water and ethylene glycol in a 1:1 volume ratio, with a freezing point of approximately -35°C, suitable for the operation of electric vehicles in low-temperature environments.

[0045] The flow path of the circulating coolant is as follows: the coolant from the storage tank is pumped by the circulating pump 10 to the inlet manifold, then distributed to each liquid-cooled pipe 3. The coolant in each pipe flows in parallel and converges at the outlet manifold, then enters the heat exchanger for cooling, and finally returns to the coolant storage tank. The circulating pump 10 is a variable frequency centrifugal pump; its speed can be adjusted by changing its power supply frequency, thereby controlling the coolant flow rate. The heat exchanger is a variable cooling capacity liquid-air heat exchanger; its cooling capacity can be adjusted to independently control the coolant inlet temperature. That is, under a given coolant flow rate, the temperature of the coolant returning to the inlet of the liquid-cooled pipe 3 is precisely adjusted by controlling the heat dissipation of the heat exchanger.

[0046] The heat-conducting fin group 6 includes multiple copper heat-conducting fins 6. The thickness of the heat-conducting fins 6 is 1mm, and the material is pure copper.

[0047] One end of the heat-conducting fin 6 is welded to the outer wall of the liquid-cooled pipe 3, and the other end extends radially outward along the liquid-cooled pipe 3 into the interior of the composite phase change material layer 2. Six heat-conducting fins 6 are evenly arranged circumferentially on the same cross-section of the liquid-cooled pipe 3, with an included angle of 60 degrees between adjacent fins. The spacing between adjacent heat-conducting fins 6 along the extension direction of the liquid-cooled pipe 3 is 25 mm. That is, starting from the pipe inlet end, a set of circumferential fins is installed every 25 mm, with six fins in each set, until the pipe outlet end.

[0048] The radial extension length of the heat-conducting fin 6 is half the vertical distance from the outer wall of the liquid-cooled pipe 3 to the edge of the composite phase change material layer 2. In this embodiment, the battery gap is 10 mm, the outer diameter of the pipe is 5 mm, and the pipe is arranged at the center of the gap. Therefore, the vertical distance from the outer wall of the pipe to the edge of the composite phase change material layer 2 is 2.5 mm, and the fin extension length is 1.25 mm.

[0049] The outer wall of the liquid-cooled pipe 3 is provided with a microgroove structure. The cross-sectional shape of the microgroove structure is V-shaped, with a groove depth of 0.2 mm, a groove width of 0.4 mm, and a spacing of 1 mm between adjacent grooves. The microgrooves extend along the axial direction of the liquid-cooled pipe 3, that is, V-shaped grooves are continuously machined along the length of the pipe's outer wall surface. This microgroove structure increases the contact area between the liquid-cooled pipe 3 and the composite phase change material layer 2, further improving the thermal coupling efficiency.

[0050] Thermally conductive insulating pads are provided on all contact interfaces between the composite phase change material layer 2 and each battery cell 1. That is, all four sides of the battery cell 1, that is, all surfaces in contact with adjacent battery cells 1 or the composite phase change material layer 2, are covered by thermally conductive insulating pads.

[0051] The thermally conductive insulating pad is made of thermally conductive silicone sheet with a thickness of 1.5 mm, a thermal conductivity of 3 W / (m·K), and a breakdown voltage of 6 kV. The thermally conductive insulating pad maintains surface contact with the surface of the battery cell 1 and the composite phase change material layer 2 through a pressing method. That is, the pre-tightening pressure during battery module assembly is used to ensure that both sides of the pad are tightly bonded to the surface of the battery cell 1 and the phase change material layer, respectively, without an adhesive layer in the middle, so as to avoid the adverse effects of adhesive on thermal conductivity.

[0052] The function of the thermally conductive insulating pad is to provide electrical insulation while ensuring good thermal conduction between the battery cell 1 and the composite phase change material layer 2, and to prevent short circuits between battery cells 1 through the phase change material layer, which may contain conductive components.

[0053] A thermal insulation layer is provided between the outer side of the composite phase change material layer 2 and the shell. The thermal insulation layer is made of aerogel felt with a thickness of 5 mm and a thermal conductivity of 0.02 W / (m·K), which is much lower than the thermal conductivity of the composite phase change material layer 2.

[0054] The thermal insulation layer covers the entire outer surface of the battery module. Its function is to reduce heat loss from the battery module in low-temperature environments, ensuring the battery operates within a suitable temperature range; and to prevent external heat from being transferred to the battery module in high-temperature environments. The status sensing unit includes multiple K-type thermocouple temperature sensors 7 and multiple capacitive phase change sensors 8.

[0055] In the gap between each adjacent battery cell 1, three temperature sensors 7 are arranged at the top, middle, and bottom along the height direction of the battery cell 1, for a total of 3. The top position is 10 mm from the top of the battery, the middle position is at half the height of the battery, and the bottom position is 10 mm from the bottom of the battery. The temperature sensors 7 are embedded inside the composite phase change material layer 2, about 1 mm from the surface of the battery cell 1, and are used to detect the temperature of the composite phase change material layer 2 at that location.

[0056] One capacitive phase change sensor 8 is arranged in each gap section. The capacitive phase change sensor 8 is a parallel plate capacitor structure with a 3mm gap between the two plates. The space between the plates is filled with the same composite phase change material as the surrounding material. The phase change state is determined by detecting the change in the dielectric constant between the plates. The sensor is embedded inside the composite phase change material layer 2 and located at the center of the gap section.

[0057] The working principle of the capacitive phase change sensor 8 is as follows: Paraffin wax has different dielectric constants in its solid and liquid states. The relative dielectric constant of solid paraffin wax is approximately 2.2, while that of liquid paraffin wax is approximately 2.8. When paraffin wax in the composite phase change material undergoes a solid-liquid phase transition, its dielectric constant gradually increases with the increase of the liquid phase volume fraction. By detecting the sensor capacitance value through a capacitance measurement circuit, the liquid phase volume fraction can be calculated.

[0058] The specific calibration method is as follows: Take a composite phase change material sample identical to that in the device, place it in a temperature-controlled chamber, and heat it from 25℃ to 65℃ at a heating rate of 1℃ per minute. Simultaneously measure the heat flow curve of the sample using a differential scanning calorimeter (DSC) to determine the phase change initiation temperature, peak temperature, and termination temperature, and calculate the liquid phase volume fraction at each temperature. The liquid phase volume fraction is calculated as follows: using the latent heat of phase change as a reference, integrate the DSC curve to calculate the proportion of heat absorbed at each temperature point to the total latent heat of phase change; this proportion is the liquid phase volume fraction. Simultaneously, measure the dielectric constant of the sample at each temperature point using a dielectric spectrometer at a frequency of 1kHz. Plot a calibration curve of dielectric constant versus liquid phase volume fraction by mapping the liquid phase volume fraction obtained by the DSC to the dielectric constant obtained by the dielectric spectrometer. Fit the calibration curve using the least squares method to obtain the functional relationship between the dielectric constant and the liquid phase volume fraction. Write this functional relationship into the control unit 9. In actual use, after the capacitive phase change sensor 8 measures the dielectric constant, the control unit 9 can automatically calculate the liquid volume fraction based on the functional relationship.

[0059] The control unit 9 is a programmable logic controller (PLC) that is connected to each temperature sensor 7, each capacitive phase change sensor 8, the circulating pump 10, and the heat exchanger via shielded cables. The control unit 9 receives voltage or current signals from each sensor, converts them into digital signals via an analog-to-digital converter, and executes control according to the following steps:

[0060] The first step is data acquisition: the control unit 9 reads the detection values ​​of all temperature sensors 7 and the capacitance values ​​of all capacitive phase change sensors 8 at a sampling frequency of 1Hz, and substitutes the capacitance values ​​into the calibration function to calculate the liquid volume fraction at each sensor location.

[0061] The second step is data integration: the control unit 9 calculates the arithmetic mean of the values ​​detected by all temperature sensors 7 as the average temperature of the composite phase change material layer 2. The control unit 9 also calculates the arithmetic mean of the values ​​detected by all capacitive phase change sensors 8 as the average liquid volume fraction of the composite phase change material layer 2.

[0062] The third step is state determination: the control unit 9 compares the average temperature with the pre-stored lower and upper limits of the phase change temperature range for the phase change matrix material, and compares the average liquid phase volume fraction with preset thresholds of 20% and 80%. In this embodiment, the lower limit of the phase change temperature range is 47°C, and the upper limit is 50°C.

[0063] Step 4, Control Execution: When the average temperature is below 47℃ and the average liquid volume fraction is below 20%, it is determined to be a low heat load state. At this time, the battery generates less heat, the temperature of the composite phase change material layer 2 is below the phase change initiation temperature, most of the phase change material is in a solid state, and the heat storage capacity is sufficient. The control unit 9 simultaneously performs the following operations: reduces the power supply frequency of the circulating pump 10, reduces the coolant flow rate to 40% to 60% of the rated flow rate; reduces the cooling power of the heat exchanger, and raises the coolant inlet temperature to 30℃ to 35℃. By reducing the coolant flow rate and increasing the coolant temperature, unnecessary cooling intensity is reduced, and pump power consumption and cooling energy consumption are lowered.

[0064] When the average temperature exceeds 50℃ or the average liquid volume fraction exceeds 80%, it is determined to be a high heat load state. At this time, the battery generates intense heat, the temperature of the composite phase change material layer 2 exceeds the phase change termination temperature, most of the phase change material has melted into a liquid state, and the latent heat absorption capacity is about to be exhausted, requiring enhanced heat dissipation through liquid cooling components. The control unit 9 simultaneously performs the following operations: increases the power supply frequency of the circulating pump 10, increases the coolant flow rate to 100% to 120% of the rated flow rate; increases the cooling power of the heat exchanger, and reduces the coolant inlet temperature to 15℃ to 20℃. By increasing the coolant flow rate and reducing the coolant temperature, the heat absorbed by the phase change material is promptly removed, causing the phase change material to re-solidify and restore its heat storage capacity.

[0065] When the average temperature is between 47°C and 50°C and the average liquid phase volume fraction is between 20% and 80%, it is considered a moderate heat load state. At this time, the heat generation and dissipation of the battery are basically balanced, the composite phase change material is in a solid-liquid coexistence state, the latent heat of phase change is playing a role, and the liquid cooling component can maintain thermal balance by dissipating heat at the current intensity. The control unit 9 maintains the current operating parameters of the circulating pump 10 and the heat exchanger unchanged.

[0066] Step 5, Hysteresis Protection: To prevent frequent start-stop or drastic speed changes in the circulating pump 10 and heat exchanger due to small temperature fluctuations, the control unit 9 incorporates hysteresis comparison logic. When the average temperature fluctuates within the range of 45℃ to 52℃, this range is calculated from the lower limit of the phase change temperature (47℃) minus 2℃ to the upper limit of the phase change temperature (50℃) plus 2℃. The control unit 9 calculates the average rate of change of the average temperature within a 1-minute time window, which is the temperature value at the end of the window minus the temperature value at the beginning of the window, divided by 60 seconds. If the absolute value of this rate of change is less than 0.5℃ per minute, it indicates that the temperature fluctuation is a slow drift rather than a rapid change, and the control unit 9 does not perform any adjustment operation, maintaining the current parameters unchanged. The control action in Step 4 is only executed when the temperature continuously exceeds the hysteresis range or the rate of change exceeds the threshold.

[0067] Example 2

[0068] The difference between this embodiment and Embodiment 1 is that the liquid cooling pipe 3 has different pipe densities in different battery gap sections.

[0069] In the battery module of Example 1, according to the thermal simulation results under 3C constant current discharge conditions, the heat dissipation conditions of the battery cell 1 in the central area of ​​the module are poor and the heat accumulation is obvious, which is identified as a high heat load area; the heat dissipation conditions in the edge area of ​​the module are better and are identified as a low heat load area.

[0070] Specifically, a thermal simulation model of the battery module was established using ANSYS Fluent software. The ambient temperature was set to 25℃, the battery was discharged at a constant current rate of 3C, the coolant inlet temperature was 25℃, and the flow rate was 5L per minute. The simulation results showed that the surface temperature of battery cell 1 in the central region of the module reached 48℃ to 52℃, while the surface temperature of battery cell 1 in the edge region was 43℃ ​​to 46℃. Based on these simulation results, the gap section between the two rows of batteries in the center of the module was determined to be the high heat load zone, and the remaining sections were determined to be the low heat load zone.

[0071] When manufacturing liquid cooling pipe 3, in the high heat load area, the spacing between adjacent liquid cooling pipe 3 is 30mm, which refers to the center distance between two adjacent rows of serpentine pipes; in the low heat load area, the spacing between adjacent liquid cooling pipe 3 is 60mm.

[0072] The differentiated pipe density is achieved by increasing the number of bends in the serpentine pipes in high heat load areas to make the pipes more densely distributed in those areas; and reducing the number of bends in low heat load areas to make the pipes more sparsely distributed. Different density sections are smoothly connected by transition bends.

[0073] Example 3

[0074] The difference between this embodiment and Embodiment 1 is as follows: The phase change matrix material is octadecanoic acid, with a phase change temperature range of 55℃ to 60℃ and a latent heat of phase change of 190 kJ / kg. The high thermal conductivity porous skeleton is graphite foam with a porosity of 90% and a pore size of 0.8 mm, forming an open-cell structure. The thermal insulation layer is made of glass fiber cotton with a thermal conductivity of 0.04 W / (m·K).

[0075] The lower limit of the phase transition temperature range pre-stored in control unit 9 is set to 55℃, and the upper limit is set to 60℃. The hysteresis range in the control logic is adjusted accordingly to 53℃ to 62℃.

[0076] This embodiment is suitable for application scenarios with high battery operating temperatures. Its advantage lies in its higher phase change temperature and stronger heat storage capacity in hot environments.

[0077] To verify the technical effect of the present invention, the device of Example 1 was compared with the following comparative examples:

[0078] Comparative Example 1 is a single liquid cooling device. The difference from Example 1 is that the battery module is not filled with composite phase change material, only the liquid cooling pipe 3 is retained, the pipe density and coolant parameters of the liquid cooling pipe 3 are the same as in Example 1, and other structures, including the shell and insulation layer, are the same as in Example 1.

[0079] Comparative Example 2 is a single composite phase change material cooling device. The difference from Example 1 is that the liquid cooling pipe 3, circulating pump 10, heat exchanger and corresponding liquid cooling circuit are not set. The battery module relies solely on the passive heat storage of the composite phase change material layer 2 for cooling. The composition of the composite phase change material and the insulation layer are the same as in Example 1.

[0080] Comparative Example 3 shows a prior art composite phase change material coupled with liquid cooling. Its structure is as follows: a liquid cooling plate is disposed on the outer bottom of the battery module; the composite phase change material fills the gaps between the individual battery cells 1; and no heat-conducting fins 6, state sensing unit, or control unit 9 are provided. Coolant flows in the bottom liquid cooling plate, exchanging heat through the contact surface between the liquid cooling plate and the bottom of the composite phase change material layer 2.

[0081] Test method:

[0082] The devices of Examples 1, 2, 1, 2, and 3 were placed in a 25°C constant temperature chamber, and the battery modules were fully discharged at a constant current rate of 3C, i.e., discharged from 100% SOC to 0% SOC. K-type thermocouples were attached to the center of the surface of each battery cell 1 to monitor the battery surface temperature in real time during the discharge process. The data acquisition frequency was 1Hz, and the highest temperature and the maximum temperature difference between each battery cell 1 were recorded throughout the discharge process. Simultaneously, the real-time power consumption of the circulation pump 10 in each device was recorded. Comparative Example 2 did not include a circulation pump 10 and was not recorded.

[0083] Test results:

[0084] Example 1 42.3℃ 3.1℃ 4.2W Example 2 41.8℃ 2.8℃ 3.8W Comparative Example 1 52.7℃ 6.5℃ 5.1W Comparative Example 2 58.4℃ 4.2℃ — Comparative Example 3 46.5℃ 5.3℃ 4.8W

[0085] The test results show that:

[0086] First, the highest temperature in Example 1 was 42.3℃, which was 10.4℃ lower than Comparative Example 1, 16.1℃ lower than Comparative Example 2, and 4.2℃ lower than Comparative Example 3. This demonstrates that the present invention, by coupling the latent heat storage of the composite phase change material with the active heat dissipation of the liquid cooling component, and by embedding the liquid cooling pipe 3 inside the phase change material and supplementing it with heat-conducting fins 6 to enhance heat transfer, achieves a significantly better heat dissipation effect than single liquid cooling, single phase change material, and existing composite solutions with external liquid cooling plates.

[0087] Second, the maximum temperature difference in Example 1 was 3.1℃, significantly lower than that in Comparative Example 1 (6.5℃), Comparative Example 2 (4.2℃), and Comparative Example 3 (5.3℃). This demonstrates that the present invention achieves intelligent adaptive adjustment of cooling intensity through the state sensing unit and the control unit 9, effectively improving the temperature uniformity inside the battery module.

[0088] Third, the pump power consumption of Example 1 is 4.2W, which is lower than that of Comparative Example 1 (5.1W) and Comparative Example 3 (4.8W). This indicates that the present invention improves heat dissipation while avoiding excessive pumping of coolant through intelligent control, thus achieving energy-saving effects.

[0089] Fourth, Example 2 further optimized the density distribution of the liquid cooling pipe 3 based on Example 1. Its maximum temperature of 41.8℃ and maximum temperature difference of 2.8℃ are both better than those of Example 1, and its pump power consumption of 3.8W is also lower than that of Example 1. This shows that the differentiated pipe density setting can achieve targeted enhanced heat dissipation and further improve thermal management performance.

[0090] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A composite phase change material coupled with liquid cooling thermal management device, characterized in that, include: The battery module is composed of several battery cells (1) arranged with gaps, and the gap between adjacent battery cells (1) is 8mm to 15mm. A composite phase change material layer (2) is filled in the gap between adjacent battery cells (1) and in the space between the outer periphery of the battery module and the shell; the composite phase change material layer (2) is composed of a phase change matrix material and a high thermal conductivity porous skeleton, and the phase change temperature of the phase change matrix material is in the range of 45°C to 60°C. The liquid cooling assembly includes multiple liquid cooling pipes (3) embedded inside the composite phase change material layer (2). The outer diameter of the liquid cooling pipes (3) is 3 mm to 6 mm. Each liquid cooling pipe (3) is connected in parallel at the coolant inlet end (4) and converges in parallel at the coolant outlet end (5). The flow channel length of each liquid cooling pipe (3) is equal. Each liquid cooling pipe (3) extends in a serpentine manner in the horizontal plane. The outer circumferential surface of the liquid cooling pipe (3) is in contact with the composite phase change material layer (2). Circulating coolant flows through the liquid cooling pipe (3). A heat-conducting fin (6) group includes multiple heat-conducting fins (6). One end of each heat-conducting fin (6) is fixedly connected to the outer wall of the liquid cooling pipe (3), and the other end extends radially outward along the liquid cooling pipe (3) into the interior of the composite phase change material layer (2). Four to eight heat-conducting fins (6) are evenly arranged circumferentially on the same cross-section of the liquid cooling pipe (3). A state sensing unit is disposed inside the composite phase change material layer (2) and includes multiple temperature sensors (7) and multiple capacitive phase change sensors (8) for real-time detection of temperature and phase change state at multiple locations in the composite phase change material layer (2), wherein the phase change state is characterized by liquid volume fraction; at least one temperature sensor (7) is arranged in the upper, middle and lower parts along the height direction of each battery cell (1) in the gap section between two adjacent battery cells (1); at least one capacitive phase change sensor (8) is arranged in the gap section between two adjacent battery cells (1); The control unit (9) is connected to the state sensing unit and the circulation pump (10) of the liquid cooling assembly respectively. The control unit (9) obtains the arithmetic mean of the detection values ​​of all temperature sensors (7) as the average temperature and obtains the arithmetic mean of the detection values ​​of all capacitive phase change sensors (8) as the average liquid volume fraction. The control unit (9) adjusts the speed of the circulation pump (10) according to the average temperature and the average liquid volume fraction to control the coolant flow rate and adjusts the cooling power of the heat exchanger to control the coolant inlet temperature. When the average temperature is lower than the lower limit of the phase change temperature of the phase change matrix material and the average liquid volume fraction is lower than 20%, the control unit (9) reduces the coolant flow rate and increases the coolant inlet temperature; when the average temperature is higher than the upper limit of the phase change temperature of the phase change matrix material or the average liquid volume fraction is higher than 80%, the control unit (9) increases the coolant flow rate and decreases the coolant inlet temperature; when the average temperature is within the phase change temperature range of the phase change matrix material and the average liquid volume fraction is between 20% and 80%, the control unit (9) maintains the current operating parameters.

2. The composite phase change material and liquid-cooled coupled thermal management device according to claim 1, characterized in that, The high thermal conductivity porous skeleton is a foamed metal or graphite foam, the porosity of the high thermal conductivity porous skeleton is 85% to 98%, the pore size is 0.1 mm to 2 mm, and it is an open-cell structure; the phase change matrix material is filled into the pores of the porous skeleton by vacuum impregnation.

3. The composite phase change material and liquid cooling coupled thermal management device according to claim 1, characterized in that, The same liquid cooling pipe (3) has different pipe densities in different battery gap sections. The pipe density is set differently according to the heat load distribution determined by the thermal simulation results of the battery module under a predetermined charge and discharge rate. The pipe density is greater in sections with higher heat load.

4. The composite phase change material and liquid-cooled coupled thermal management device according to claim 1, characterized in that, The heat-conducting fins (6) are spaced apart along the extension direction of the liquid cooling pipe (3), and the spacing between adjacent heat-conducting fins (6) along the extension direction of the pipe is 10 mm to 50 mm; the thickness of the heat-conducting fins (6) is 0.5 mm to 3 mm, and the radial extension length of the fins is 1 / 4 to 1 / 2 of the vertical distance from the outer wall of the liquid cooling pipe (3) to the edge of the composite phase change material layer (2).

5. The composite phase change material and liquid-cooled coupled thermal management device according to claim 1, characterized in that, The capacitive phase change sensor (8) calculates the liquid volume fraction by detecting the change in dielectric constant of the composite phase change material. The correspondence between the dielectric constant and the liquid volume fraction is obtained by performing differential scanning calorimetry and dielectric spectrum testing on the composite phase change material in advance to establish a calibration curve of dielectric constant and liquid volume fraction.

6. The composite phase change material and liquid-cooled coupled thermal management device according to claim 1, characterized in that, The outer wall of the liquid cooling pipe (3) is provided with a micro-groove structure. The cross-sectional shape of the micro-groove structure is V-shaped or U-shaped, the groove depth is 0.1mm to 0.5mm, the groove width is 0.2mm to 1mm, the spacing between adjacent grooves is 0.5mm to 2mm, and the micro-groove extends along the axial direction of the liquid cooling pipe (3).

7. The composite phase change material and liquid cooling coupled thermal management device according to claim 1, characterized in that, It also includes a thermal insulation layer disposed between the outer side of the composite phase change material layer (2) and the shell, wherein the thermal conductivity of the thermal insulation layer is not higher than 0.05 W / (m·K).

8. The composite phase change material and liquid-cooled coupled thermal management device according to claim 1, characterized in that, Thermally conductive insulating pads are provided on all contact interfaces between the composite phase change material layer (2) and each of the battery cells (1). The thickness of the thermally conductive insulating pads is 0.5 mm to 3 mm, the thermal conductivity is not less than 1 W / (m·K), and the breakdown voltage is not less than 5 kV.

9. A battery pack, characterized in that, Includes the composite phase change material and liquid-cooled coupled thermal management device as described in any one of claims 1 to 8.

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