Thermal management system based on double-layer phase change and air cooling collaborative heat dissipation

Abstract

The invention discloses a thermal management system based on double-layer phase change and air cooling cooperative heat dissipation. The system comprises a battery module, a first-stage phase change layer, a second-stage phase change layer, a binding post, a supporting plate, a sleeve and an air cooling channel. The double-layer phase-change cooling device is filled with two composite phase-change materials with high heat conductivity coefficients, and the composite phase-change materials are distributed in the radial direction, so that heat generated by the battery can be quickly absorbed, and the temperature in the battery module is kept uniform. And when the power battery module operates for a preset time length, the air cooling device is automatically started, and part of heat absorbed by the phase change device is dissipated to the environment. The air cooling system adopts a square wave type air supply strategy, that is, intermittent cooling airflow is provided by periodically starting and stopping a fan. By combining the double-layer phase change cooling and air cooling technology, the problems of non-uniform internal temperature distribution and local overheating of the battery module are effectively improved, the applicable working condition range of the battery module is expanded, and the stability and reliability of the system are improved.

Description

Technical Field

[0001] This invention relates to the field of battery thermal management, and more specifically to a thermal management system based on a dual-layer phase change and air-cooled synergistic heat dissipation. Background Technology

[0002] With the continuous expansion of electric vehicles and other high-energy equipment applications, power lithium batteries, as the core energy storage unit, have become a key foundation of modern electric drive systems. However, during charging and discharging, especially under high-rate conditions, they often generate a large amount of heat. A rapid rise in temperature can easily induce thermal runaway, which not only accelerates battery performance degradation and shortens cycle life but may also cause safety hazards, seriously threatening the reliability and safety of the battery system. Therefore, battery thermal management has become a key area of ​​current technological research. An effective thermal management system is crucial for ensuring stable battery operating temperature, improving safety, optimizing performance, and extending battery life.

[0003] Currently, mainstream battery cooling solutions mainly include air cooling, liquid cooling, and phase change material (PCM) cooling. Among them, air cooling systems are simple in structure and low in cost, but lack temperature uniformity. Phase change cooling, as a passive temperature control method, relies on the absorption or release of latent heat during the phase change process of the material to regulate the battery temperature, and has advantages such as no need for external energy supply, simple structure, and low maintenance cost. Currently used phase change materials are mostly organic, with generally low thermal conductivity, and usually need to be combined with high thermal conductivity frameworks such as expanded graphite or metal foam to enhance thermal conductivity. However, single phase change materials are limited by their phase change temperature range, making it difficult to meet the precise temperature control requirements of complex environments and high-power operation in high-energy-density applications. To address this, a dual-layer phase change cooling system has been developed, which integrates two materials with different phase change temperatures to form a multi-stage synergistic heat absorption and release mechanism, which is expected to significantly improve thermal management efficiency.

[0004] However, phase change materials themselves have limited latent heat, and their sustained temperature control capabilities face challenges. Combining an air-cooling system with dual-layer phase change cooling technology can further improve overall thermal management performance. Specifically, by setting a support plate with a hollow structure between the battery module and the sleeve to construct an air-cooling channel, and employing an intermittent air supply strategy, the start and stop of the air-cooling system are dynamically adjusted according to battery operating time and real-time operating conditions. This method not only improves heat dissipation efficiency but also reduces system energy consumption while ensuring effective control of the battery module temperature, thereby optimizing overall performance. The synergistic operation of phase change cooling and air-cooling systems achieves a more efficient and energy-saving battery temperature control solution, maintaining system stability and efficiency under different temperature and operating conditions, and better meeting the stringent requirements of electric vehicles and other high-energy devices for battery heat dissipation and temperature control. Summary of the Invention

[0005] This invention provides a thermal management system based on a dual-layer phase change and air-cooled synergistic heat dissipation. The system employs two composite phase change materials with different phase change temperatures and thermophysical properties to construct a dual-layer structure, achieving staged heat absorption through synergistic design of temperature and thickness. The air-cooling system uses a periodic airflow mode to reduce energy consumption while providing auxiliary heat dissipation. This composite system effectively balances the temperature distribution of the battery during multi-stage charging and discharging processes, significantly improving the environmental adaptability and thermal safety performance of the power battery under complex operating conditions, thereby reducing the risk of thermal runaway.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a thermal management system based on a combined bilayer phase change and air-cooling heat dissipation approach. The core design of the invention is as follows: A hybrid thermal management scheme is formed by combining bilayer phase change cooling technology with air-cooling technology to overcome the limitations of current cooling technologies. This system fully utilizes the heat absorption and release capabilities of phase change materials at different temperatures and enhances heat transfer through forced convection, thereby achieving precise temperature control and efficient heat dissipation of the battery.

[0007] The double-layer phase change cooling device is composed of two composite phase change materials, with expanded graphite as the thermally conductive filler, and includes the following material proportions: n-Eicosane / Expanded Graphite: n-Eicosane has a melting point of 33.63℃ ~ 35.36℃ and accounts for 85%; expanded graphite accounts for 15%, forming the primary phase change cooling layer; RT44HC / Expanded Graphite: RT44HC has a melting point of 37.84℃ ~ 41.47℃ and accounts for 88%; expanded graphite accounts for 12%, forming a secondary phase change cooling layer.

[0008] The selection and ratio of the two composite phase change materials, based on their respective thermophysical parameters and phase change characteristics, can achieve precise temperature control and efficient heat dissipation of the battery module. Based on the aforementioned scheme, the preparation method of either of the two composite phase change materials with temperature control capabilities includes the following steps: Pure phase change material (eicosane or RT44HC) is heated to complete melting in a 60°C water bath, followed by the addition of a predetermined mass of expanded graphite, and the mixture is thoroughly stirred with a magnetic stirrer until homogeneous. The mixture is then poured into a mold and cooled to room temperature to obtain the corresponding composite phase change material. Compared with existing technologies, this invention uses an adsorption method to prepare a bilayer phase change cooling structure with two-stage temperature control capabilities. The primary phase change layer uses eicosane / expanded graphite, and the secondary phase change cooling layer uses RT44HC / expanded graphite. An effective encapsulation process solves the leakage problem that may occur during the phase change process. Furthermore, this invention also conducted relevant tests on the leakage rate of the composite phase change material. The results show that the prepared composite material has good thermal performance and thermal cycling stability, and can maintain stable heat dissipation during long-term use.

[0009] Specifically, the first-stage phase change layer first absorbs the heat generated by the battery's operation, regulating the temperature through the latent heat of phase change. After the latent heat of the first-stage phase change material is exhausted, the second-stage phase change layer takes over to absorb the remaining heat, thus achieving multi-stage coordinated heat regulation. This design enables the battery module to maintain a stable temperature range under complex operating conditions, improving the battery's environmental adaptability and heat dissipation capacity. Building upon this, the air-cooling system further enhances the overall heat dissipation effect through square wave intermittent airflow. The battery module forms an air-cooling channel through a support plate and a sleeve, and the air-cooling device periodically starts and stops according to a set operating time. Specifically, under square wave control, the air-cooling device starts airflow according to a set cycle, accelerating heat dissipation with intermittently enhanced airflow; after the cycle ends, the air-cooling device stops working. This operating time-based control strategy significantly reduces system energy consumption while improving heat dissipation efficiency. The dual-layer phase change cooling and air-cooling system work together to ensure the battery's temperature control accuracy under different operating conditions, while also improving the energy efficiency and operational stability of the thermal management system. Through this composite heat dissipation mechanism, the present invention effectively solves the problems of uneven temperature distribution and local overheating in battery modules, further optimizes the overall performance of the battery system, and meets the stringent requirements of electric vehicles and other high-energy-density devices for thermal management systems.

[0010] like Figure 1 As shown, battery module 1, as the core of the entire thermal management system, consists of multiple battery cells. These battery cells are connected in series or parallel via terminals to form a current path. Support plate 4 is used to fix and support the battery module; the two are mechanically connected to ensure the battery module remains stable during operation, preventing loosening or displacement. Support plate 4 and sleeve 5 are connected by snap-fit, forming a robust overall structure that effectively guides airflow while providing support for other components. Terminals are provided on the support plate for wire routing. Furthermore, a certain gap is maintained between the outer wall of the secondary phase change layer and the inner wall of the sleeve, forming part of the air duct.

[0011] The air-cooling channel is constructed by a support plate and a sleeve. The support plate, connected to the sleeve, forms the airflow path. A fan is typically installed at the inlet of the air-cooling channel, positioned at an opening on the side wall of the sleeve and connected to the air duct through this opening. The fan is connected to a control system via electrical wires, which controls the start and stop of the air-cooling device according to a preset time cycle. This connection between the fan and the air-cooling channel ensures forced airflow into the channel. The airflow passes over the outer surface of the battery module and the periphery of the phase change cooling layer, carrying away heat and dissipating it through the channel, thereby effectively improving the battery module's heat dissipation capacity and temperature control accuracy.

[0012] The present invention will now be described in detail through specific embodiments. Attached Figure Description

[0013] Figure 1 This is a schematic diagram (isoaxial side) of a thermal management system based on dual-layer phase change and air-cooled synergistic heat dissipation according to the present invention.

[0014] Figure 2 This is a schematic diagram (top view) of a thermal management system based on a dual-layer phase change and air-cooled synergistic heat dissipation according to the present invention.

[0015] Figure 3 This is a schematic diagram of the phase change layer thickness and configuration in a thermal management system based on dual-layer phase change and air cooling synergistic heat dissipation according to the present invention.

[0016] Figure 4 This is a schematic diagram of a battery module containing only a dual-layer phase change cooling device in a thermal management system based on dual-layer phase change and air-cooled synergistic heat dissipation according to the present invention.

[0017] Figure 5 This is a schematic diagram of the support plate in a thermal management system based on dual-layer phase change and air-cooled synergistic heat dissipation according to the present invention. Detailed Implementation

[0018] To further clarify the technical solution of the present invention, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0019] like Figure 1 As shown, this invention provides a thermal management system based on a dual-layer phase change and air-cooled synergistic heat dissipation. The system includes an 18650 lithium-ion battery 1, a primary phase change device 2, a secondary phase change layer device 3, a support plate 4, and a sleeve 5. The support plate structure is as follows... Figure 5As shown, this system constructs two rows of four lithium-ion battery modules. The individual battery cells are in close contact with the primary phase change cooling device 2, and the battery sidewalls are integrally bonded to the annular primary phase change cooling layer 2. The secondary phase change cooling layer 3 is located on the side closest to the air, in close contact with the primary phase change cooling layer 2, forming an integrated cooling structure by enclosing it in a box shape. The coordinated operation of the primary and secondary phase change cooling devices achieves efficient absorption and transfer of battery heat. The thickness of the primary phase change cooling layer is L1 = 1 mm, while the thickness of the secondary phase change cooling layer is L2 = 3 mm. The specific thickness definitions are as follows: Figure 3 As shown. The bottom of the battery module is fixed by a support plate, and adjacent battery cells are connected by wires led out from the terminals to ensure stable current conduction and uniform heat distribution. A certain gap is left between the top of the battery module and the sleeve to ensure natural air circulation.

[0020] Based on this, the air-cooling system forms an air-cooling channel through the support plate 4 and the sleeve 5 to further improve the heat dissipation effect of the battery module. The air-cooling device operates periodically according to a square wave air supply. Specifically, the air-cooling device operates according to a set operating time cycle, using a square wave control method: Air-cooling device startup: When the system is in the "on" phase of the square wave, the air-cooling device starts, and the fan in the air duct begins to operate, generating airflow through the battery module to accelerate heat dissipation. Air-cooling device shutdown: After the air-cooling device has run for a set period, it enters the "off" phase of the square wave, and the air-cooling device stops working, and the airflow stops. At this time, the temperature of the battery module will slightly stabilize, and unnecessary energy consumption is avoided.

[0021] By using this square-wave, time-based airflow control method, the air-cooled unit can effectively improve heat dissipation efficiency without excessive energy consumption. The start and stop of the air-cooled unit in each cycle is managed by the control system, ensuring that the system starts when the battery temperature is high and automatically stops when the temperature recovers, thus reducing energy consumption.

[0022] In actual power battery systems, the system consists of multiple repeating symmetrical units. Figure 1 For demonstration purposes only, a dual-layer phase change cooling coupled with air cooling, consisting of a single repeating symmetrical unit, is provided. The power battery system of an electric vehicle consists of multiple battery modules. Under conditions such as rapid charging and discharging of the battery and continuous operation in high-temperature environments, the battery generates heat due to internal electrochemical reactions, which accumulates within the battery module and is difficult to dissipate. Combining air cooling with dual-layer phase change cooling can achieve a better cooling effect.

[0023] In a preferred embodiment of the present invention, the annular primary phase change cooling device is filled with a highly thermally conductive expanded graphite-eicosane composite phase change temperature control material, the melting point of which is 35.2℃ ~ 37.47℃.

[0024] In a preferred embodiment of the present invention, the box-shaped two-stage phase change cooling device is filled with a high thermal conductivity expanded graphite-RT44HC composite phase change temperature control material, which has a melting point of 42.89℃ ~ 44.93℃.

[0025] In a preferred embodiment of the present invention, the air-cooling system adopts a square wave air supply method controlled by the running time of the power battery module.

[0026] like Figure 1 As shown, the working method of the thermal management system based on dual-layer phase change and air-cooled synergistic heat dissipation is as follows: When the 18650 lithium-ion battery 1 is operating, the electrochemical reaction inside the battery generates a large amount of heat. Due to the differences in thermal conductivity of the battery materials, the heat is mainly concentrated on the side near the electrodes, resulting in a stepped temperature distribution, with some areas of the battery having higher temperatures and others lower temperatures. As the battery operates, the heat is gradually transferred to the primary phase change cooling device 2. The expanded graphite material filled inside the primary phase change cooling layer has excellent thermal conductivity and can quickly transfer the heat generated by the battery to the phase change material. At this time, the phase change material mainly absorbs heat through sensible heat, and as the heat continues to accumulate, the temperature of the battery module gradually rises.

[0027] Figure 4 The diagram shows the structure of a dual-layer phase change cooling battery thermal management system. When the battery temperature rises to the melting temperature of the first-stage phase change cooling layer 3.2, the phase change material in the first-stage phase change cooling device begins to exert its latent heat effect. During this stage, the excess heat generated by the battery module 3.1 is absorbed by the phase change material, while the temperature of the phase change material remains almost constant, maintaining a constant temperature for the battery module. Through this latent heat absorption process, the system effectively prevents the battery temperature from becoming too high and improves the uniformity of temperature distribution. When the latent heat of the first-stage phase change cooling layer is completely consumed, the temperature of the battery module will rise slightly until it reaches the phase change temperature of the second-stage phase change cooling layer 3.3. At this point, the phase change material in the second-stage phase change cooling layer again exerts its latent heat effect, continuing to absorb the remaining heat generated by the battery module and further maintaining the temperature stability of the battery module. The introduction of the second-stage phase change layer not only effectively enhances the temperature control capability but also further improves the temperature distribution of the battery module, making it more uniform, avoiding localized overheating, and improving the overall thermal management effect of the battery. Simultaneously, the outer wall of the second-stage phase change cooling device comes into contact with the external air and begins to dissipate heat through natural convection. Heat is transferred from the outer surface of the phase change material to the air, and excess heat in the system is discharged to the external environment through airflow, thereby enhancing the overall heat dissipation capacity.

[0028] Based on this, an air-cooling channel is set on the outside of the double-layer phase change cooling assembly. This air-cooling channel, together with the sleeve, defines the airflow channel, forming an effective airflow path. To make the overall system structure clearer, Figure 2 A schematic diagram (top view) of a dual-layer phase change cooling coupled with air cooling is provided for a battery thermal management system. The design of the air cooling channel 1.6 considers optimal airflow distribution and heat dissipation efficiency, ensuring that cooling airflow flows evenly across the battery module and effectively removes heat. A fan or blower is installed at the inlet of the air cooling channel to provide forced airflow, enhancing airflow within the channel and improving heat dissipation. In practical applications, the outlet of the air cooling channel is connected to the environment or an exhaust duct at the bottom of the vehicle to ensure smooth exhaust of hot air and prevent its accumulation inside the vehicle or around the battery module.

[0029] When the battery module is operating, the system intelligently controls and adjusts the fan's operating status. After 10 minutes of operation, the fan automatically starts, supplying cooling air to the cooling channel. Once started, the cooling air flows over the outer surface of the second phase change layer and the sleeve wall, creating forced convection heat transfer and carrying away the heat absorbed by the phase change material. This process effectively removes heat from the battery module, preventing the phase change material from remaining in a fully molten state for extended periods. This ensures the battery module remains within a suitable temperature range, preventing overheating or uneven temperature distribution.

[0030] After the fan runs for 10 minutes, the system automatically shuts it down and enters a rest phase, ceasing air supply. Every 10 minutes of ventilation, the fan restarts, resuming air supply to the cooling duct. This timed, interval-based air-cooling design achieves dynamic airflow, ensuring coordination between the cooling process and battery operating status, reducing energy consumption, and maximizing cooling efficiency.

[0031] Although phase change materials (PCCs) can absorb a large amount of heat when the temperature reaches their phase change point, prolonged exposure to high temperatures or high loads can cause the heat generated by the battery system to exceed the heat absorption capacity of the PCCs, resulting in the PCCs failing to complete the phase change in time or losing their effective cooling effect. The synergistic effect of the air cooling and phase change cooling systems in this system complements each other, improving the heat dissipation efficiency of the battery module: after the PCCs absorb heat, the air cooling channels promptly remove the heat absorbed by the phase change layer, effectively preventing the PCCs from melting too quickly, thereby improving the stability of the thermal management system. Simultaneously, the intermittent air supply design reduces energy consumption and optimizes the system's energy efficiency. Through the appropriate combination of air cooling and phase change cooling, the battery module can maintain a stable temperature under various operating conditions, thereby extending battery life and ensuring safe operation and performance. This coupled and synergistic technology of air cooling and phase change cooling provides an efficient, energy-saving, and reliable solution for power battery thermal management. The technical solution of this invention has been described above with reference to specific embodiments.

[0032] These descriptions are merely for explaining the technical principles of the present invention and should not be construed as limiting the scope of protection of the present invention in any way. Based on this interpretation, any equivalent structural or procedural transformations made using the content of this specification and drawings, or direct or indirect applications in other related system fields, are similarly included within the scope of protection of the present invention.

Claims

1. A heat management system based on double-layer phase change and air cooling cooperative heat dissipation, characterized in that: The battery module (1.1) is composed of a 18650 lithium-ion battery, a first phase change layer (1.2), a second phase change layer (1.3), a support plate (1.4), a sleeve (1.5), and an air cooling channel (1.6). The first phase change layer (1.2) is designed in a ring shape with a thickness of 1 mm, which is in close contact with the surface of the battery cell. The second phase change layer (1.3) is in a box shape with a thickness of 3 mm, which is installed on the outside of the first phase change layer and is in close contact with it. The bottom of the battery module is fixedly connected with the support plate (1.4), and a certain gap is reserved between the support plate (1.4) and the sleeve (1.5). The top of the battery cell is connected in series through the lead wire led out by the terminal post, and a gap is also provided between the top of the battery cell and the sleeve to form an air flow channel. During operation, the first phase change layer (1.2) absorbs heat first in the initial heating stage of the battery, and uses the latent heat of phase change to achieve temperature control. When the latent heat reserve of the first phase change layer (1.2) is exhausted, the second phase change layer (1.3) continues to absorb the residual heat, and plays a role of temperature buffer. On this basis, the system starts forced air cooling through the air cooling channel (1.6), enhances the airflow to accelerate heat dissipation, thereby reducing the overall temperature of the battery module. The air cooling device and the double-layer phase change cooling system work cooperatively, significantly improve the heat dissipation efficiency, optimize the temperature uniformity inside the battery module, effectively avoid local overheating, and further enhance the stability and overall energy efficiency of the system.

2. The dual-layer phase change and air cooling synergistic thermal management system for battery cells of claim 1, wherein: The first phase change layer (1.2) and the second phase change layer (1.3) use phase change materials with a gradient distribution of melting points, and the melting point of the first phase change material is lower than that of the second phase change material, so as to realize the segmented relay absorption of heat. During the operation of the battery, the first phase change layer (1.2) absorbs and utilizes the latent heat first for temperature regulation; after the latent heat of the first phase change layer (1.2) is exhausted, the second phase change layer (1.3) continues to absorb the remaining heat, thereby forming an effective temperature buffer mechanism.

3. The dual-layer phase change and air cooling synergistic thermal management system for battery cells of claim 1, wherein: The first and second phase change layers (1.2, 1.3) are arranged along the radial direction and adopt ring and box shapes respectively, forming an efficient heat conduction path to ensure that the heat generated by the battery module (1.1) can be quickly transferred to the phase change layer, realizing efficient heat dissipation.

4. The dual-layer phase change and air cooling synergic thermal management system for battery cells of claim 1, wherein: The support plate (1.4) adopts a hollow structure, forming a continuous air cooling channel between the battery module and the sleeve (1.5); the lead wire led out by the terminal post at the top of the battery cell realizes connection, and a gap is also reserved between the top of the battery cell and the sleeve to jointly constitute an air flow path.

5. The dual-layer phase change and air cooling synergic thermal management system for battery cells of claim 1, wherein: The air cooling device adopts an intermittent air supply mode, which is periodically started according to the predetermined time length and working condition of the battery module, so as to save energy and avoid unnecessary air cooling operation.

6. The dual-layer phase change and air cooling synergic thermal management system for battery cells of claim 1, wherein: The second phase change layer (1.3) is in direct contact with the ambient air, and the overall heat dissipation capacity of the system is further enhanced through natural convection.

7. The dual layer phase change material and air cooling cooperative heat dissipation battery thermal management system according to claim 1, characterized in that: The air cooling device and the double-layer phase change cooling system work cooperatively to form a composite heat dissipation mechanism, further improving the overall heat dissipation efficiency. This design optimizes the temperature uniformity inside the battery module, effectively prevents local overheating, and significantly enhances the thermal stability and operating efficiency of the system.

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