Battery pack and phase change material coupling liquid cooling composite thermal management system

Abstract

The invention belongs to the technical field of battery thermal management, and discloses a battery pack and a phase change material coupling liquid cooling composite thermal management system.The battery pack comprises a plurality of battery structures, each battery structure comprises a lithium battery, a fin structure, a phase change material filling area and a liquid cooling plate, and the fin structure is arranged on the periphery of the lithium battery; the liquid cooling plate is arranged on the periphery of the fin structure, a phase-change material filling area is formed between the liquid cooling plate and the fin structure, and the phase-change material filling area is filled with a phase-change material for absorbing redundant heat and generating phase change, so that the temperature fluctuation of the battery is reduced. The lithium bromide heat pump and the direct-current power supply are combined, and accurate adjustment of the temperature of the battery pack is achieved through efficient heat exchange and intelligent control. The system can be rapidly switched between a cooling mode and a heating mode, and it is ensured that the battery is always kept within the optimal temperature range in different working environments.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery thermal management, and in particular relates to a battery pack and phase change material coupled liquid cooling composite thermal management system. Background Art

[0002] Lithium-ion batteries are favored by the market for their excellent energy storage capacity and long cycle life. However, these batteries may encounter performance degradation problems when facing extreme temperatures, whether too high or too low. High temperatures may lead to shortened battery life and structural damage, and even cause thermal runaway; while low temperatures may lead to increased internal resistance, reduced capacity, and reduced charging and discharging efficiency. These problems are prevalent in many industries such as energy storage power stations, new energy vehicles, mobile power supplies, and communication base stations. Temperature control is crucial to the performance of lithium-ion batteries. Therefore, in order to ensure the safe and efficient operation of the battery, its operating temperature should be maintained at 20 to 40°C, and the maximum temperature difference of the battery pack should be controlled within 5°C. Battery thermal management technology can significantly reduce the negative impact of ambient temperature on battery performance and improve its energy conversion efficiency. Therefore, building a lithium-ion battery thermal management system that can operate stably under various climatic conditions is crucial to improving the safety, economy, and durability of the battery. Such a system can not only ensure the long-term stable operation of the battery, but also provide strong technical support for the sustainable development of related industries.

[0003] The invention patent (CN202380015705.8) describes a heat exchanger for a battery. The battery includes one or both of a first stack and a second stack of battery cells. The heat exchanger includes a heat exchanger leg and a heat exchanger foot. The heat exchanger leg can be positioned to be thermally coupled to one or both of the first stack and the second stack of battery cells. In addition, the heat exchanger leg is arranged to transfer heat energy from one or both of the first stack and the second stack to the heat exchanger foot. The heat exchanger structure of the invention uses a split design of the leg and the foot, and the heat exchanger structure is complex, which increases the manufacturing cost and assembly difficulty.

[0004] The invention patent (CN202410098469.7) proposes a battery thermal management method, which selectively exchanges heat with the motor refrigerant, air conditioning refrigerant or external heat source through the heat exchange medium in the circulation pipeline to achieve heating of the battery. The method controls the heating process according to the heat generation of the battery and the current state of the electric vehicle. The invention only uses heat exchange fluid to exchange heat with the battery, and the battery temperature uniformity is poor. Frequent switching of heat sources reduces system efficiency. At the same time, the invention involves multiple heat exchangers and pipeline designs, which may increase costs and system maintenance difficulties.

[0005] The invention patent (CN202410193298.6) discloses a battery thermal management device, which connects the evaporator located below and the condenser above through a guide tube to form a loop. The condenser is equipped with a heat dissipation unit, an air inlet fan and an air outlet fan to achieve air circulation and heat dissipation. The invention uses a heat exchange fluid to exchange heat with the battery, and the battery temperature uniformity is poor. The condenser is air-cooled, the heat dissipation efficiency is poor, and there may be energy consumption and noise problems. This invention patent (CN202311841571.3) discloses a battery thermal management system, including two relatively arranged temperature control substrates and multiple temperature control partitions, with gaps formed between the partitions for placing battery cells. The temperature control substrate passes a working fluid to heat or cool the battery cell. The temperature control partition contains a phase change material and a heating device. The phase change material is used to exchange heat with the battery cell. The heating device can heat the phase change material, thereby achieving heating and heat dissipation of the battery cell. This design improves the low-temperature heating effect and temperature consistency of the battery. The temperature control substrate and the temperature have the problem of long thermal management reaction time, especially under rapid charging and discharging conditions. At the same time, the design of the temperature control substrate and the temperature control partition increases the difficulty of manufacturing and assembly, which may lead to increased costs.

[0006] The above existing technologies have the following defects: (1) The design of the heat exchanger may be structurally complex, difficult to manufacture and install, and may lead to increased costs. At the same time, the efficiency of thermal coupling is limited by the contact area and the thermal conductivity of the material, which may affect the efficiency of heat transfer. (2) There may be delays in the control of the heat exchange medium under different conditions, resulting in the battery being unable to respond quickly to temperature changes under rapidly changing working conditions, affecting the overall performance of the battery. (3) Although the temperature control substrate and temperature control partition design can achieve simultaneous heating and heat dissipation, there may be a problem of long thermal management response time, especially under rapid charging and dissipation. (4) The heat exchange efficiency is low when heat is exchanged with the battery through the heat exchange fluid. At the same time, the uniformity of the battery surface temperature depends on the layout of the flow channel. If you want to maintain better temperature uniformity, you need to adopt a more complex liquid cooling structure, which increases the cost of the thermal management system. Summary of the invention

[0007] The object of the present invention is to provide a battery pack and a phase change material coupled liquid cooling composite thermal management system to solve the above-mentioned technical problems.

[0008] In order to solve the above technical problems, the specific technical solution of a battery pack and a phase change material coupled liquid cooling composite thermal management system of the present invention is as follows: A battery pack includes multiple battery structures, each battery structure includes a lithium battery, a fin structure, a phase change material filling area and a liquid cooling plate, the fin structure is arranged on the periphery of the lithium battery, the liquid cooling plate is arranged on the periphery of the fin structure, a phase change material filling area is formed between the liquid cooling plate and the fin structure, and the phase change material filling area is filled with phase change material for absorbing excess heat and undergoing phase change, thereby reducing battery temperature fluctuations.

[0009] Furthermore, the phase change material includes a substrate, a thermal conductivity enhancer and a flexible skeleton material, wherein the substrate is paraffin, the thermal conductivity enhancer is expanded graphite, and the flexible skeleton material is SEBS (styrene-ethylene-butylene-styrene copolymer).

[0010] Furthermore, the lithium battery is cylindrical, and the fin structure includes a fin shell and threaded pin fins, which are used to enhance the heat transfer between the lithium battery and the phase change material. The fin shell is a hollow cylindrical structure, and the fin shell is wrapped around the periphery of the lithium battery. A plurality of threaded pin fins are fixedly installed on the surface of the fin shell, and the surface of the threaded pin fins has a threaded structure, and a phase change material filling area is formed between the threaded pin fins.

[0011] Furthermore, the fin structure material is copper metal.

[0012] Furthermore, the liquid cooling plate is a hollow cylindrical structure with a cooling liquid flow channel arranged inside. The cooling liquid flow channel is arranged in a surrounding manner from top to bottom in the liquid cooling plate. The cooling liquid flow channel of each battery structure is connected to the inlet header at the bottom and to the outlet header at the top to form a battery pack. When cold water or hot water is needed, the coolant or hot water flows in from the inlet header, flows through the cooling liquid flow channel, is evenly distributed to each liquid cooling plate, and finally flows out from the outlet header to take away the heat. The liquid cooling plate exchanges heat with the phase change material but is not in direct contact with the lithium battery.

[0013] Furthermore, the liquid cooling plate is made entirely of aluminum alloy material.

[0014] The present invention also discloses a phase change material coupled liquid cooling composite thermal management system, comprising a battery pack according to any one of claims 1 to 4, characterized in that the system comprises a lithium bromide heat pump and a DC power supply, the lithium bromide heat pump comprises an absorber, an evaporator, a throttle valve, a condenser, a generator, a solution heat exchanger, a solution pump, a battery pack and three-way valve 1, three-way valve 2, three-way valve 3 and three-way valve 4; The absorber has a cavity for storing a dilute lithium bromide solution, and is provided with a refrigerant water inlet, a cooling water outlet, a cooling water inlet, an absorbent inlet and an absorbent outlet. The absorber absorbs refrigerant water from the evaporator through the refrigerant water inlet; The evaporator is provided with a refrigerant inlet, a refrigerant outlet, a chilled water inlet, and a chilled water outlet. The refrigerant water from the condenser and the chilled water from the battery pack enter the evaporator through the refrigerant inlet and the chilled water inlet respectively for heat exchange. The condenser is provided with a refrigerant inlet, a refrigerant outlet, a cooling water inlet, and a cooling water outlet. The refrigerant inlet is connected to the refrigerant outlet of the generator. The refrigerant and the cooling water enter the condenser through the refrigerant inlet and the chilled water inlet for heat exchange. The generator has a cavity for storing a lithium bromide concentrated solution, and is provided with an electric heater, a refrigeration steam outlet, an absorbent inlet and an absorbent outlet. The refrigerant water generated by the generator is connected to a condenser through the refrigeration steam outlet; The solution heat exchanger is provided with a concentrated solution inlet, a concentrated solution outlet, a dilute solution inlet and a dilute solution outlet. The dilute solution from the generator and the concentrated solution from the absorber enter the solution heat exchanger through the concentrated solution inlet and the dilute solution inlet respectively for heat exchange. The three-way valve 1 connects the cooling water inlet of the condenser, the cooling water outlet of the absorber and the three-way valve 3, the three-way valve 2 connects the cooling water outlet of the condenser, the cooling water inlet of the absorber and the three-way valve 4, the three-way valve 3 connects the three-way valve 1, the inlet header of the battery pack and the chilled water outlet of the evaporator, and the three-way valve 4 connects the three-way valve 2, the outlet header of the battery pack and the chilled water inlet of the evaporator; In cooling mode, when the battery temperature is too high, the lithium bromide heat pump is driven by a heat source or an electric heater. During this process, the low-temperature refrigerant first exchanges heat with the chilled water in the evaporator. After the chilled water absorbs heat, it enters the liquid cooling plate, which takes the heat away from the battery pack and reduces the battery temperature. The fluid circulation between the evaporator and the condenser realizes the effective transfer of heat, so that the heat is quickly transferred from the battery pack to the external environment. In heating mode, when the battery temperature is too low, the system provides two heating methods to ensure that the battery can start smoothly and work normally. The first method is to directly use a DC power supply to electrically heat the battery pack to the required temperature; the second method is through the indirect heating process of the lithium bromide heat pump. After the cooling water absorbs heat in the condenser, the heat is transferred to the liquid cooling plate, and the heat is heated to the battery pack through the liquid cooling plate, thereby heating the battery.

[0015] Furthermore, the system automatically switches the working mode according to the external environment temperature and the surface temperature of the battery pack through an intelligent control system, thereby realizing precise adjustment of the temperature control function; specifically, the working modes include the following: Working mode at normal temperature: When the ambient temperature is within the normal range of 0℃ to 35℃, the battery operates within its normal temperature range. In this case, the system mainly relies on phase change materials to adjust the temperature of the battery. Phase change materials can effectively absorb and release heat within this temperature range to keep the battery surface temperature stable. At this time, there is no need to start the liquid cooling system. The heat storage and release function of the phase change material is sufficient to maintain the battery surface temperature within an appropriate range. High temperature or fast charge and discharge mode: In a high temperature environment or when the battery needs to be charged and discharged quickly, the phase change material alone cannot effectively keep the battery temperature within the working range, or the phase change material may undergo a complete phase change in a short period of time and lose its cooling effect. At this time, the system automatically starts the liquid cooling mode, and the liquid cooling system works with the phase change material to quickly cool down. In this mode, the flow rate of the coolant will be automatically adjusted according to the heating rate and surface temperature of the battery. The initial flow rate is small, and as the battery temperature rises, the flow rate will gradually increase to better control the battery temperature and avoid overheating; Working mode at low temperature: In a low temperature environment, the resistance of the battery will increase and the capacity will decrease, which may affect the normal operation of the battery. Therefore, the system will first heat the battery through a DC power supply, and automatically stop the electric heating function when the battery temperature reaches a certain threshold. At this time, the system will switch to hot water heating mode and heat the battery with hot water until the battery reaches the operating temperature. After reaching the operating temperature, the heat generated by the battery itself will maintain the temperature. If the surface temperature of the battery continues to drop, the system will supplement the heating with an appropriate amount of hot water to ensure that the battery is maintained in a suitable working state.

[0016] Furthermore, the system includes the following workflow: Circulation process of refrigerant water and absorbent: During the battery operation, first, the lithium bromide concentrated solution of the generator is heated by an electric heater to generate refrigerant vapor, which enters the condenser. In the condenser, the refrigerant vapor exchanges heat with low-temperature cooling water, and the cooling water absorbs the heat in the vapor, so that the refrigerant vapor condenses into liquid refrigerant water. The condensed liquid refrigerant water enters the evaporator through a throttle valve, and then exchanges heat with the chilled water used to cool the battery pack, absorbs the heat of the chilled water and evaporates into refrigerant vapor. The evaporated refrigerant vapor enters the absorber, where the refrigerant vapor is completely absorbed by the lithium bromide dilute solution and forms a lithium bromide concentrated solution. Solution circulation and heat exchange process: When the system is working, the lithium bromide concentrated solution in the generator will be heated by electric heating, so that water vapor will be precipitated and converted into a dilute solution. The dilute solution will be sent to the solution heat exchanger through the solution pump, where it will exchange heat with the low-temperature concentrated solution from the absorber. The function of the solution heat exchanger is to transfer the heat from the generated high-temperature dilute solution to the low-temperature concentrated solution in the absorber after absorbing the refrigerant vapor, thereby preventing the low-temperature concentrated solution from crystallizing due to too low temperature. After the heat exchange, the temperature of the dilute solution is reduced and it is sent to the absorber to complete the circulation of the absorbent. After passing through the solution heat exchanger, the temperature of the concentrated solution rises, maintaining a suitable working state, and then enters the generator; Flow and heat exchange of chilled water and cooling water: When the battery needs to be cooled, the chilled water exchanges heat with the refrigerant water in the evaporator and is converted into low-temperature chilled water, which then enters the battery pack through the liquid cooling plate to take away the excess heat generated by the battery. When the battery pack needs to be heated, the cooling water enters the condenser from the outside, absorbs the heat in the refrigerant vapor and becomes high-temperature cooling water. The flow of these high-temperature cooling waters is adjusted by three-way valve one, with part of it entering the absorber for heat exchange and part of it entering the battery pack for heating. At this time, the system will control the flow by adjusting three-way valve one, three-way valve two, three-way valve three, and three-way valve four to ensure that the flow of the heating water matches the battery requirements.

[0017] A battery pack and phase change material coupled liquid cooling composite thermal management system of the present invention has the following advantages: (1) The system adopts a composite phase change material (with paraffin as the base), and the paraffin absorbs excess heat at high temperature and undergoes phase change, which significantly reduces the temperature fluctuation of the battery. Compared with traditional single phase change materials, the composite phase change material significantly improves the thermal conductivity by adding expanded graphite as a thermal conductivity enhancer, and can conduct heat to the thermal management system more quickly and effectively. In addition, SEBS, as a flexible skeleton material, not only avoids the leakage of phase change materials, but also improves the stability and durability of the system. Compared with the hard materials that may be used in other patents, SEBS provides higher structural flexibility and longer service life.

[0018] (2) The fin structure of the present invention adopts a pin-fin structure, which increases the heat exchange area, and further optimizes the flow state of the fluid by adding a threaded structure, thereby improving the heat transfer efficiency. Compared with traditional flat fins, the combination of pin-fin and threaded design can more effectively enhance the heat exchange effect, thereby quickly reducing the battery temperature in a short time. In addition, the fins are made of copper metal, which ensures excellent thermal conductivity, can transfer heat more efficiently, and optimize thermal management performance.

[0019] (3) The liquid cooling plate adopts a hollow cylindrical structure with a flow channel design arranged inside. The flow channel flows around the liquid cooling plate, which reduces the liquid cooling volume while increasing the heat exchange area of ​​the coolant. The indirect heat exchange between the liquid cooling plate and the battery avoids the problem of uneven heat exchange between the coolant and the battery, and increases the uniformity of the battery surface temperature. At the same time, the liquid cooling plate is made of aluminum alloy, which has excellent thermal conductivity and light weight. Compared with traditional copper materials, aluminum alloy can further reduce the overall weight of the system.

[0020] (4) The uniqueness of this system lies in the combination of lithium bromide heat pump and DC power supply. Through efficient heat exchange and intelligent control, it can quickly switch between cooling and heating modes to ensure that the battery is always at the optimal operating temperature under different ambient temperatures. Compared with the traditional single cooling system or heating system, this system can not only effectively cool down under high temperature conditions, but also provide two heating modes: direct electric heating and indirect heating through lithium bromide heat pump. The two heating methods provide more flexibility to ensure that the battery can start quickly and operate normally regardless of low or high temperature environments. As the core of the thermal management system, the lithium bromide heat pump is driven by a heat source and can effectively utilize nearby waste heat to achieve efficient heat exchange. Compared with traditional heating or cooling systems that rely on external energy, the lithium bromide heat pump has significant advantages in energy saving. It can not only absorb excess heat in the cooling mode and take away the heat generated by the battery, but also transfer heat to the battery pack through the heat absorption process in the heating mode, avoiding additional energy consumption and further improving the energy efficiency of the system. By equipping multiple three-way valves to achieve hot and cold switching, compared with the complex control mechanism that may exist in other patents, this system greatly simplifies the structure and control process of the thermal management system. The intelligent control of the four three-way valves enables efficient switching of thermal modes, avoiding the coordination issues of complex pumps, valves and heat exchangers in traditional thermal management systems, making the overall system more efficient, reliable and easy to maintain.

[0021] The valve configuration allows the coolant to be adjusted and distributed according to actual needs, optimizing the heat exchange process, thereby ensuring that the entire system can maintain the best cooling effect and performance under various operating conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the battery pack structure of the present invention; Figure 2 A top view of the battery pack structure of the present invention; Figure 3 A top view of the liquid cooling plate structure of the present invention; Figure 4 It is the fin structure diagram of the present invention; Figure 5 A top view of the fin structure of the present invention; Figure 6This is a structural diagram of the phase change material coupled liquid cooling composite thermal management system of the present invention; Explanation of the marks in the figure: 1. Absorber; 2. Evaporator; 3. Throttle valve; 4. Condenser; 5. Generator; 6. Solution heat exchanger; 7. Solution pump; 8. Battery pack; 81. Lithium battery; 82. Fin structure; 821. Fin shell; 822. Threaded pin fin; 83. Phase change material filling area; 84. Liquid cooling plate; 841. Coolant flow channel; 9. DC power supply; 10. Three-way valve one; 11. Three-way valve two; 12. Three-way valve three; 13. Three-way valve four. DETAILED DESCRIPTION

[0023] In order to better understand the purpose, structure and function of the present invention, a battery pack and a phase change material coupled liquid cooling composite thermal management system of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0024] like Figure 1 Figure 2 Figure 3 As shown, a battery pack of the present invention includes multiple battery structures, each battery structure includes a lithium battery 81, a fin structure 82, a phase change material filling area 83 and a liquid cooling plate 84, the fin structure 82 is arranged on the periphery of the lithium battery 81, the liquid cooling plate 84 is arranged on the periphery of the fin structure 82, a phase change material filling area 83 is formed between the liquid cooling plate 84 and the fin structure 82, and the phase change material filling area 83 is filled with phase change material for absorbing excess heat and undergoing phase change, thereby reducing battery temperature fluctuations.

[0025] Phase change materials have high energy storage density, adjustable phase change temperature and good stability. They can maintain stable temperature during the phase change process and can achieve precise temperature control. Phase change materials include a substrate, a thermal conductivity enhancer and a flexible skeleton material. The substrate is paraffin, which has good heat storage capacity. When the battery temperature rises, the paraffin can absorb excess heat and undergo a phase change (from solid to liquid), thereby reducing battery temperature fluctuations. This characteristic of phase change materials enables the battery to maintain a relatively stable temperature during use, thereby avoiding performance degradation or damage caused by overheating. In order to improve thermal conductivity, the thermal conductivity enhancer is expanded graphite, which can significantly improve the efficiency of thermal conduction and ensure that heat can be quickly transferred from the battery to the phase change material for absorption and storage. The flexible skeleton material is SEBS (styrene-ethylene-butylene-styrene copolymer), which ensures that the phase change material will not leak during operation while maintaining the stability and durability of the structure.

[0026] The lithium battery 81 is cylindrical. Figure 4 Figure 5As shown, the fin structure 82 includes a fin shell 821 and a threaded pin fin 822, which are used to enhance the heat transfer between the lithium battery and the phase change material. The fin shell 821 is a hollow cylindrical structure, and the fin shell 821 is wrapped around the periphery of the lithium battery 81. A plurality of threaded pin fins 822 are fixedly mounted on the surface of the fin shell 821, which can increase the heat exchange area and thus improve the heat exchange efficiency. Compared with traditional flat fins, the pin fin structure can more effectively exchange heat with the phase change material, ensuring that heat can be quickly transferred from the battery pack to the external environment. The surface of the threaded pin fin 822 has a threaded structure, which can improve the flow state of the fluid, further enhance the heat exchange effect, and improve the heat transfer efficiency. A phase change material filling area 83 is formed between the threaded pin fins 822, and the overall fin structure 82 is made of copper metal, which ensures that heat can be quickly transferred to the phase change material due to its excellent thermal conductivity.

[0027] The liquid cooling plate 84 is a hollow cylindrical structure with a cooling liquid flow channel 841 arranged inside. The cooling liquid flow channel 841 is arranged from top to bottom in the liquid cooling plate 84. The cooling liquid flow channel 841 of each battery structure is connected to the inlet header 85 at the bottom and to the outlet header 86 at the top to form a battery pack 8. When cold water or hot water is needed, the cooling liquid or hot water flows in from the inlet header 86, flows through the cooling liquid flow channel 841, is evenly distributed to each liquid cooling plate 84, and finally flows out from the outlet header 86 to effectively take away the heat. The liquid cooling plate 84 exchanges heat with the phase change material, but is not in direct contact with the lithium battery 81. By directly exchanging heat between the phase change material and the lithium battery 81, the temperature of the lithium battery 81 can be made more uniform, avoiding local overheating or overcooling, while simplifying the structure of the liquid cooling plate 84 and reducing the complexity and cost of the system. The liquid cooling plate 84 is made of aluminum alloy as a whole. Due to its excellent thermal conductivity and lightweight properties, it can provide more efficient thermal management and reduce the weight of the battery pack.

[0028] The phase change material coupled liquid cooling composite thermal management system of the present invention adopts a lithium bromide heat pump combined with a DC power supply to achieve precise regulation of the battery pack temperature through efficient heat exchange and intelligent control. The system can quickly switch between cooling and heating modes to ensure that the battery always remains in the optimal temperature range under different working environments.

[0029] like Figure 6 As shown, the system includes a lithium bromide heat pump and a DC power supply 9, wherein the lithium bromide heat pump includes an absorber 1, an evaporator 2, a throttle valve 3, a condenser 4, a generator 5, a solution heat exchanger 6, a solution pump 7, a battery pack 8 and three-way valve 10, three-way valve 2 11, three-way valve 3 12, and three-way valve 4 13.

[0030] The absorber 1 has a cavity for storing a dilute lithium bromide solution, and is provided with a refrigerant water inlet, a cooling water outlet, a cooling water inlet, an absorbent inlet, and an absorbent outlet. The absorber 1 absorbs refrigerant water from the evaporator 2 through the refrigerant water inlet.

[0031] The evaporator 2 is provided with a refrigerant inlet, a refrigerant outlet, a chilled water inlet, and a chilled water outlet. The refrigerant water from the condenser 4 and the chilled water from the battery pack 8 enter the evaporator 2 through the refrigerant inlet and the chilled water inlet respectively for heat exchange.

[0032] The condenser 4 is provided with a refrigerant inlet, a refrigerant outlet, a cooling water inlet, and a cooling water outlet. The refrigerant inlet is connected to the refrigerant outlet of the generator 5. The refrigerant and the cooling water enter the condenser 4 through the refrigerant inlet and the chilled water inlet for heat exchange.

[0033] The generator 5 has a cavity for storing a lithium bromide concentrated solution, and is provided with an electric heater, a refrigeration steam outlet, an absorbent inlet and an absorbent outlet. The refrigerant water generated by the generator 5 is connected to the condenser 4 through the refrigeration steam outlet.

[0034] The solution heat exchanger 6 is provided with a concentrated solution inlet, a concentrated solution outlet, a dilute solution inlet and a dilute solution outlet. The dilute solution from the generator 5 and the concentrated solution from the absorber 1 enter the solution heat exchanger 6 through the concentrated solution inlet and the dilute solution inlet respectively for heat exchange.

[0035] Three-way valve one 10 connects the cooling water inlet of condenser 4, the cooling water outlet of absorber 1 and three-way valve three 12, three-way valve two 11 connects the chilled water outlet of condenser 4, the cooling water inlet of absorber 1 and three-way valve four 13, three-way valve three 12 connects three-way valve one 10, the inlet header 85 of battery pack 8 and the chilled water outlet of evaporator 2, three-way valve four 13 connects three-way valve two 11, the outlet header 86 of battery pack 8 and the chilled water inlet of evaporator 2.

[0036] The core of the system is a lithium bromide heat pump, which can provide a stable supply of hot or cold water to meet the thermal management needs of the battery.

[0037] In cooling mode, when the battery temperature is too high, the lithium bromide heat pump is driven by a heat source or an electric heater. In this process, the low-temperature refrigerant first exchanges heat with the chilled water in the evaporator 2. After the chilled water absorbs heat, it enters the liquid cooling plate 84, which takes away the heat from the battery pack 8, lowers the battery temperature, and ensures the safe operation of the battery. The fluid circulation between the evaporator 2 and the condenser 4 realizes the effective transfer of heat, so that the heat is quickly transferred from the battery pack 8 to the external environment.

[0038] In heating mode, when the battery temperature is too low, the system provides two heating methods to ensure that the battery can start smoothly and work normally. The first method is to directly electrically heat the battery pack 8 through the DC power supply 9 to heat the battery pack 8 to the required temperature; the second method is an indirect heating process through a lithium bromide heat pump. After the cooling water absorbs heat in the condenser 4, the heat is transferred to the liquid cooling plate 84, and the heat is heated to the battery pack 8 through the liquid cooling plate 84, thereby heating the battery.

[0039] like Figure 1 As shown, the battery thermal management system of the present invention uses composite phase change material (PCM) and lithium bromide heat pump combined with liquid cooling system to accurately control the temperature of the battery under different environmental conditions to ensure the stable performance of the battery and extend the service life. The working mode of the system automatically switches the cooling or heating mode according to the changes in the surface temperature of the battery pack and the external environment through a variety of heat exchange processes and intelligent control strategies. The following is the detailed working mode and process of the present invention under different temperature conditions: Working mode: intelligent control and automatic adjustment The battery thermal management system automatically switches the working mode according to the external environment temperature and the surface temperature of the battery pack through an intelligent control system, thereby achieving precise adjustment of the temperature control function.

[0040] (1) Working mode at normal temperature When the ambient temperature is within the normal range of 0℃ to 35℃, the battery operates within its normal temperature range. In this case, the system mainly relies on phase change materials to regulate the temperature of the battery. Phase change materials can effectively absorb and release heat within this temperature range to keep the battery surface temperature stable. At this time, there is no need to start the liquid cooling system. The heat storage and release function of the phase change material is enough to maintain the temperature of the battery surface within a suitable range to ensure the safety and efficiency of the battery.

[0041] (2) High temperature or fast charge and discharge mode In a high temperature environment or when the battery needs to be charged and discharged quickly, the phase change material alone cannot effectively keep the battery temperature within the operating range, or the phase change material may undergo a complete phase change in a short period of time and lose its cooling effect. At this time, the system will automatically start the liquid cooling mode, and the liquid cooling system will work with the phase change material to quickly cool down. In this mode, the flow rate of the coolant will be automatically adjusted according to the heating rate and surface temperature of the battery. The initial flow rate is small, and as the battery temperature rises, the flow rate will gradually increase to better control the battery temperature and avoid overheating.

[0042] (3) Working mode at low temperature In a low temperature environment, the resistance of the battery will increase and the capacity will decrease, which may affect the normal operation of the battery. Therefore, the system will first heat the battery through a DC power supply. However, although power heating at low temperatures can increase the temperature of the battery, it may also cause certain battery losses. Therefore, this heating mode is only used in extremely low temperature environments or when the battery needs to be started urgently. During the heating process, the system will quickly provide heat to the battery and automatically stop the electric heating function after the battery temperature reaches a certain threshold. At this time, the system will switch to hot water heating mode and heat the battery with hot water until the battery reaches the operating temperature. After reaching the operating temperature, the battery's own heat generation will maintain the temperature. If the battery surface temperature continues to drop, the system will use an appropriate amount of hot water for additional heating to ensure that the battery remains in a suitable working state.

[0043] Through this precise temperature control mode, the battery can still maintain good working condition under extreme temperatures, ensuring the long life and stability of the battery, while improving the efficiency and safety of the battery.

[0044] Workflow: 1. Phase change material coupled liquid cooling work: Phase change materials, as an ideal thermal management material, have significant advantages such as high energy storage density, adjustable phase change temperature and good cycle stability. During the phase change process, phase change materials can effectively maintain temperature stability, thereby achieving more precise temperature control. In order to further improve the performance of the thermal management system and solve the problem of thermal saturation of phase change materials in the thermal management process, liquid cooling technology is combined with phase change materials. Liquid cooling technology takes away the heat absorbed by PCM through the flow of coolant, avoiding the loss of thermal management ability of phase change materials after thermal saturation, while reducing the temperature of phase change materials, increasing the temperature difference between batteries and phase change materials, and enhancing heat exchange. Phase change materials absorb or release heat when the battery is working, effectively alleviating the impact of temperature fluctuations. Through this combination, the design can be simplified, thereby reducing the cost of the system, and improving the thermal coupling performance of the battery and the thermal management system, making temperature regulation more accurate and efficient. This thermal management system can achieve faster and more precise temperature control to cope with rapidly changing heat loads under different working conditions. Whether it is the large amount of heat generated during fast charging or the temperature fluctuations during instantaneous discharge, the system can respond in real time to ensure that the battery is always at the optimal operating temperature, thereby improving the battery's operating efficiency and service life.

[0045] 2. Circulation process of refrigerant water and absorbent During the battery operation, first, the lithium bromide concentrated solution of the generator 5 is heated by an electric heater to generate refrigerant vapor. These refrigerant vapors enter the condenser 4. In the condenser 4, the refrigerant vapor exchanges heat with the low-temperature cooling water, and the cooling water absorbs the heat in the vapor, so that the refrigerant vapor condenses into liquid refrigerant water. The condensed liquid refrigerant water enters the evaporator 2 through the throttle valve 3, and then exchanges heat with the chilled water used to cool the battery pack 8, absorbs the heat of the chilled water and evaporates into refrigerant vapor. The evaporated refrigerant vapor enters the absorber 1, and the refrigerant vapor is completely absorbed by the dilute lithium bromide solution therein to form a lithium bromide concentrated solution.

[0046] 3. Solution circulation and heat exchange process When the system is working, the lithium bromide concentrated solution in the generator 5 will be heated by electric heating, thereby precipitating water vapor and converting it into a dilute solution. The dilute solution is sent to the solution heat exchanger 6 through the solution pump 7, where it exchanges heat with the low-temperature concentrated solution from the absorber 1. The function of the solution heat exchanger 6 is to transfer the heat from the high-temperature dilute solution in the generator 5 to the low-temperature concentrated solution in the absorber 1 after absorbing the refrigerant vapor, thereby preventing the low-temperature concentrated solution from crystallizing due to too low temperature. After the heat exchange, the temperature of the dilute solution is reduced and it is sent to the absorber 1 to complete the circulation of the absorbent. After passing through the solution heat exchanger, the temperature of the concentrated solution rises, maintaining a suitable working state, and then enters the generator 5. In this way, the solution heat exchanger 6 plays an important role in temperature regulation in the entire circulation process, ensuring the stability of the solution concentration and temperature in the system, avoiding crystallization and improving the efficiency of the system.

[0047] 4. Flow and heat exchange of chilled water and cooling water When the battery needs to be cooled, the chilled water exchanges heat with the refrigerant water in the evaporator 2 and is converted into low-temperature chilled water, and then enters the battery pack 8 through the liquid cooling plate 84, taking away the excess heat generated by the battery, effectively reducing the temperature of the battery, and ensuring that the battery will not overheat during long-term operation. When the battery pack 8 needs to be heated, the cooling water enters the condenser 4 from the outside, absorbs the heat in the refrigerant vapor and becomes high-temperature cooling water. The flow of these high-temperature cooling waters is adjusted through the three-way valve 10, part of which enters the absorber 1 for heat exchange, and part of which enters the battery pack 8 for heating. At this time, the system will control the flow by accurately adjusting the three-way valve 10, the three-way valve 2 11, the three-way valve 3 12, and the three-way valve 13 4 to ensure that the flow of the heating water flow matches the battery requirements.

[0048] It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

Claims

1. A battery pack, comprising a plurality of battery structures, each battery structure comprising a lithium battery (81), a fin structure (82), a phase change material filling area (83) and a liquid cooling plate (84), wherein the fin structure (82) is arranged at the periphery of the lithium battery (81), the liquid cooling plate (84) is arranged at the periphery of the fin structure (82), a phase change material filling area (83) is formed between the liquid cooling plate (84) and the fin structure (82), and a phase change material is filled in the phase change material filling area (83) to absorb excess heat and cause phase change, thereby reducing battery temperature fluctuations.

2. The battery pack according to claim 1, characterized in that: The phase change material comprises a substrate, a thermal conductivity enhancer and a flexible skeleton material, wherein the substrate is paraffin, the thermal conductivity enhancer is expanded graphite, and the flexible skeleton material is SEBS (styrene-ethylene-butylene-styrene copolymer).

3. The battery pack according to claim 1, characterized in that: The lithium battery (81) is cylindrical, and the fin structure (82) comprises a fin shell (821) and threaded pin fins (822) for enhancing heat transfer between the lithium battery and the phase change material. The fin shell (821) is a hollow cylindrical structure, and the fin shell (821) is wrapped around the outer periphery of the lithium battery (81). A plurality of threaded pin fins (822) are fixedly mounted on the surface of the fin shell (821), and the surface of the threaded pin fins (822) has a threaded structure, and a phase change material filling area (83) is formed between the threaded pin fins (822).

4. The battery pack according to claim 3, characterized in that: The material of the fin structure (82) is copper metal.

5. The battery pack according to claim 1, characterized in that: The liquid cooling plate (84) is a hollow cylindrical structure, and a cooling liquid flow channel (841) is arranged inside. The cooling liquid flow channel (841) is arranged in a surrounding manner from top to bottom in the liquid cooling plate (84). The cooling liquid flow channel (841) of each battery structure is connected to the inlet header at the bottom and to the outlet header at the top, forming a battery pack (8). When cold water or hot water supply is required, the cooling liquid or hot water flows in from the inlet header, flows through the cooling liquid flow channel (841), is evenly distributed to each liquid cooling plate (84), and finally flows out from the outlet header to take away the heat. The liquid cooling plate (84) performs heat exchange with the phase change material, but does not directly contact the lithium battery (81).

6. The battery pack according to claim 5, characterized in that: The liquid cooling plate (84) is entirely made of aluminum alloy material.

7. A phase change material coupled liquid cooling composite thermal management system, comprising a battery pack according to any one of claims 1 to 6, characterized in that: The system comprises a lithium bromide heat pump and a direct current power supply (9), wherein the lithium bromide heat pump comprises an absorber (1), an evaporator (2), a throttle valve (3), a condenser (4), a generator (5), a solution heat exchanger (6), a solution pump (7), a battery pack (8), and a three-way valve 1 (10), a three-way valve 2 (11), a three-way valve 3 (12), and a three-way valve 4 (13); The absorber (1) has a cavity for storing a dilute lithium bromide solution, and is provided with a refrigerant water inlet, a cooling water outlet, a cooling water inlet, an absorbent inlet and an absorbent outlet. The absorber (1) absorbs refrigerant water from the evaporator (2) through the refrigerant water inlet; The evaporator (2) is provided with a refrigerant inlet, a refrigerant outlet, a chilled water inlet, and a chilled water outlet. The refrigerant water from the condenser (4) and the chilled water from the battery pack (8) enter the evaporator (2) through the refrigerant inlet and the chilled water inlet respectively for heat exchange. The condenser (4) is provided with a refrigerant inlet, a refrigerant outlet, a cooling water inlet, and a cooling water outlet. The refrigerant inlet is connected to the refrigerant outlet of the generator (5). The refrigerant and the cooling water enter the condenser (4) through the refrigerant inlet and the chilled water inlet for heat exchange. The generator (5) has a cavity for storing a lithium bromide concentrated solution, and is provided with an electric heater, a refrigeration steam outlet, an absorbent inlet and an absorbent outlet. The refrigerant water generated by the generator (5) is connected to the condenser (4) via the refrigeration steam outlet. The solution heat exchanger is provided with a concentrated solution inlet, a concentrated solution outlet, a dilute solution inlet and a dilute solution outlet, and the dilute solution from the generator (5) and the concentrated solution from the absorber (1) enter the solution heat exchanger through the concentrated solution inlet and the dilute solution inlet respectively for heat exchange; The three-way valve one (10) is connected to the cooling water inlet of the condenser (4), the cooling water outlet of the absorber (1) and the three-way valve three (12); the three-way valve two (11) is connected to the cooling water outlet of the condenser (4), the cooling water inlet of the absorber (1) and the three-way valve four (13); the three-way valve three (12) is connected to the three-way valve one (10), the inlet header of the battery pack (8) and the chilled water outlet of the evaporator (2); the three-way valve four (13) is connected to the three-way valve two (11), the outlet header of the battery pack (8) and the chilled water inlet of the evaporator (2); In the cooling mode, when the battery temperature is too high, the lithium bromide heat pump is driven to work by a heat source or an electric heater. During this process, the low-temperature refrigerant first exchanges heat with the chilled water in the evaporator (2). After the chilled water absorbs heat, it enters the liquid cooling plate (84), and the heat is taken away from the battery pack (8) through the liquid cooling plate (84), thereby reducing the battery temperature. The fluid circulation between the evaporator (2) and the condenser (4) realizes the effective transfer of heat, so that the heat is quickly transferred from the battery pack (8) to the external environment. In the heating mode, when the battery temperature is too low, the system provides two heating methods to ensure that the battery can be started smoothly and work normally. The first method is to directly electrically heat the battery pack (8) through a DC power supply (9) to heat the battery pack (8) to a required temperature. The second method is an indirect heating process through a lithium bromide heat pump. After the cooling water absorbs heat in the condenser (4), the heat is transferred to the liquid cooling plate (84), and the heat is heated to the battery pack (8) through the liquid cooling plate (84), thereby heating the battery.

8. The phase change material coupled liquid cooling composite thermal management system according to claim 7, characterized in that: The system automatically switches the working mode according to the external environment temperature and the surface temperature of the battery pack (8) through an intelligent control system, thereby realizing precise adjustment of the temperature control function; the specific working modes include the following: Working mode at normal temperature: When the ambient temperature is within the normal range of 0℃ to 35℃, the battery operates within its normal temperature range. In this case, the system mainly relies on phase change materials to adjust the temperature of the battery. Phase change materials can effectively absorb and release heat within this temperature range to keep the battery surface temperature stable. At this time, there is no need to start the liquid cooling system. The heat storage and release function of the phase change material is sufficient to maintain the battery surface temperature within an appropriate range. High temperature or fast charge and discharge mode: In a high temperature environment or when the battery needs to be charged and discharged quickly, the phase change material alone cannot effectively keep the battery temperature within the working range, or the phase change material may undergo a complete phase change in a short period of time and lose its cooling effect. At this time, the system automatically starts the liquid cooling mode, and the liquid cooling system works with the phase change material to quickly cool down. In this mode, the flow rate of the coolant will be automatically adjusted according to the heating rate and surface temperature of the battery. The initial flow rate is small, and as the battery temperature rises, the flow rate will gradually increase to better control the battery temperature and avoid overheating; Working mode at low temperature: In a low temperature environment, the resistance of the battery will increase and the capacity will decrease, which may affect the normal operation of the battery. Therefore, the system will first heat the battery through a DC power supply (9) and automatically stop the electric heating function when the battery temperature reaches a certain threshold. At this time, the system will switch to hot water heating mode and heat the battery with hot water until the battery reaches the operating temperature. After reaching the operating temperature, the heat generated by the battery itself will maintain the temperature. If the surface temperature of the battery continues to drop, the system will supplement the heating with an appropriate amount of hot water to ensure that the battery is maintained in a suitable working state.

9. The phase change material coupled liquid cooling composite thermal management system according to claim 7, characterized in that: The system includes the following workflow: Circulation process of refrigerant water and absorbent: During the operation of the battery, first, the lithium bromide concentrated solution in the generator (5) is heated by an electric heater to generate refrigerant vapor, and the refrigerant vapor enters the condenser (4). In the condenser (4), the refrigerant vapor exchanges heat with low-temperature cooling water, and the cooling water absorbs the heat in the vapor, so that the refrigerant vapor is condensed into liquid refrigerant water. The condensed liquid refrigerant water enters the evaporator (2) through the throttle valve (3), and then exchanges heat with the chilled water used to cool the battery pack (8), absorbs the heat of the chilled water and evaporates into refrigerant vapor. The evaporated refrigerant vapor enters the absorber (1), and the refrigerant vapor is completely absorbed by the lithium bromide dilute solution therein to form a lithium bromide concentrated solution. Solution circulation and heat exchange process: When the system is working, the lithium bromide concentrated solution in the generator (5) is heated by electric heating, thereby precipitating water vapor and converting into a dilute solution. The dilute solution is sent to the solution heat exchanger (6) through the solution pump (7), where it exchanges heat with the low-temperature concentrated solution from the absorber (1). The function of the solution heat exchanger (6) is to transfer the heat from the generated high-temperature dilute solution to the low-temperature concentrated solution in the absorber (1) after absorbing the refrigerant vapor, thereby preventing the low-temperature concentrated solution from crystallizing due to too low temperature. After the heat exchange, the temperature of the dilute solution decreases and is sent to the absorber (1), completing the circulation of the absorbent. After passing through the solution heat exchanger (6), the temperature of the concentrated solution rises and maintains a suitable working state, and then enters the generator (5); Flow and heat exchange of chilled water and cooling water: When the battery needs to be cooled, the chilled water exchanges heat with the refrigerant water in the evaporator (2) and is converted into low-temperature chilled water, which then enters the battery pack (8) through the liquid cooling plate (84) to take away the excess heat generated by the battery. When the battery pack (8) needs to be heated, the cooling water enters the condenser (4) from the outside, absorbs the heat in the refrigerant vapor and becomes high-temperature cooling water. The high-temperature cooling water is regulated in flow by three-way valve one (10), part of which enters the absorber (1) for heat exchange, and part of which enters the battery pack (8) for heating. At this time, the system controls the flow by adjusting three-way valve one (10), three-way valve two (11), three-way valve three (12), and three-way valve four (13) to ensure that the flow of the heating water matches the battery demand.

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