Battery pack water cooling system

Abstract

A battery pack water cooling system comprises a battery pack and further comprises a first surface air cooler and a cold water storage tower used for heat insulation. A plurality of phase change energy storage water tanks which are vertically arranged are placed in the cold water storage tower, and the adjacent phase change energy storage water tanks are separated through heat insulation plates; the first surface air cooler is positioned above the cold water storage tower; and the battery pack is connected with a liquid cooling plate for cooling the battery pack. A gradient phase change material cold storage technology and a water cooling system are combined to cool the battery pack, all-weather cold storage can be achieved, the number of phase change materials with various phase change temperatures is configured according to the time of a phase change temperature interval, the cold storage capacity of the whole cooling tower is slightly influenced by daily temperature changes, and the cooling capacity of the whole cooling tower is greatly improved. Compared with a single-phase-change temperature material, the cold storage capacity is high, and the cooling efficiency is high; compared with the prior art, the system is more energy-saving and environment-friendly in the aspects of battery pack cooling and temperature control.

Description

Technical Field

[0001] This utility model relates to the field of battery pack technology, and in particular to a battery pack water cooling system. Background Technology

[0002] With advancements in energy storage technology, energy storage systems, as a crucial component for improving grid efficiency and balancing electricity supply and demand, have been widely applied in smart grids, working alongside renewable energy systems such as photovoltaics and wind power to build a more flexible and reliable energy network. Currently, most mainstream energy storage systems on the market adopt a containerized design, with their core components being multiple battery packs housed within the container. However, during operation, these battery packs release a significant amount of heat, necessitating an efficient cooling system to ensure normal system operation. Traditional cooling methods, such as air-cooled or liquid-cooled systems, suffer from the following problems:

[0003] 1. Low cooling efficiency: Air-cooled systems rely on fans for heat dissipation. However, since fans are usually fixed in one location, energy storage devices near the fan can get better cooling, while those far from the fan are poorly cooled. This causes uneven cooling of the entire energy storage system.

[0004] 2. High energy consumption: Existing active cooling systems usually rely on mechanical equipment, which consumes a lot of energy, increasing the operating cost of the system. In addition, the maintenance and failure rate of these devices are also high, affecting the stability and reliability of the system. Utility Model Content

[0005] The present invention aims to solve the above problems by providing a battery pack water cooling system that uses multi-phase change temperature gradient phase change materials with different material amounts for different phase change temperatures according to the duration of different temperature segments throughout the day, thereby passively storing natural cold sources around the clock for low-energy consumption and efficient cooling of the battery pack.

[0006] To solve the above-mentioned technical problems, the technical solution of this utility model is as follows:

[0007] A battery pack water cooling system includes a battery pack, a first surface cooler, and a thermally insulated cooling tower. The cooling tower contains multiple vertically arranged phase change water tanks, with adjacent tanks separated by insulation plates. The first surface cooler is located above the cooling tower. The multiple vertically arranged phase change water tanks are filled with phase change material particles of different phase change critical point values. Depending on the height of the tank, higher tanks contain phase change material particles with larger phase change critical point values, creating a gradient. The phase change critical point values ​​of the phase change material particles are all between 10°C and 50°C. Second surface coolers are connected to the outside of each phase change water tank, with the second surface coolers positioned higher than the phase change water tanks. The upper end of each phase change water tank is connected to a second surface cooler via a first inlet pipe, and the lower end of each tank is connected via... The first liquid outlet pipe is connected to the second surface cooler, thus forming loop A; loop A is filled with water, and loop A forms a circulating heat exchange with the air due to the different densities of water caused by temperature changes; the battery pack is connected to a liquid cooling plate for cooling itself; each of the multiple phase change cold water storage tanks is equipped with a heat exchange pipe, and the heat exchange pipes in adjacent phase change cold water storage tanks are connected by pipes; the liquid cooling plate is connected to the first surface cooler through a pipe; the first surface cooler is connected to the heat exchange pipe of the uppermost phase change cold water storage tank through a second liquid inlet pipe; the heat exchange pipe of the lowermost phase change cold water storage tank is connected to the liquid cooling plate through a second liquid outlet pipe; the liquid cooling plate, the first surface cooler, and the heat exchange pipes of the multiple phase change cold water storage tanks form loop B; loop B is filled with refrigerant; a pump is installed on the second liquid outlet pipe to drive the refrigerant to circulate in loop B.

[0008] There are four phase change cold water tanks in total; the four phase change cold water tanks are filled from top to bottom with 45℃ phase change material particles, 35℃ phase change material particles, 25℃ phase change material particles and 15℃ phase change material particles; the phase change critical point value of the 45℃ phase change material particles is 45℃, the phase change critical point value of the 35℃ phase change material particles is 35℃, the phase change critical point value of the 25℃ phase change material particles is 25℃, and the phase change critical point value of the 15℃ phase change material particles is 15℃.

[0009] The content distribution ratio of the 45℃ phase change material particles, 35℃ phase change material particles, 25℃ phase change material particles and 15℃ phase change material particles is 2:3:3:2.

[0010] The battery pack and the outside of the liquid cooling plate are also equipped with an energy storage container.

[0011] The heat exchange pipe is a coil.

[0012] The heat exchange pipe is fitted with fins on the outside.

[0013] The battery pack is also equipped with a temperature sensor.

[0014] The technical effects achieved by this invention are as follows: This invention combines all-weather cold storage technology using gradient phase change materials with different phase change temperatures with a water cooling system to cool the battery pack, resulting in high cooling efficiency. Furthermore, water, due to its density variations caused by temperature changes, circulates and exchanges heat within the phase change cold storage tank, the second surface cooler, the first inlet pipe, and the first outlet pipe, continuously cooling the refrigerant. This not only reduces the energy consumption of mechanical equipment but also lowers the system's operating costs. When the refrigerant does not need to exchange heat through the phase change material particles and the ambient temperature is below the phase change critical point of the phase change material particles, the particles can use the second surface cooler to lower their own temperature to their own phase change critical point, thus storing cold energy and providing more cold energy for subsequent refrigerant heat exchange. This improves energy utilization efficiency and makes rational use of natural cold sources. Compared to existing technologies, this invention is more energy-efficient and environmentally friendly in terms of battery pack cooling and temperature control. Attached Figure Description

[0015] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0016] Figure 1 This is a schematic diagram of the structure of a battery pack water cooling system according to this utility model. Detailed Implementation

[0017] The present invention will now be described in further detail with reference to the accompanying drawings.

[0018] See Figure 1 .

[0019] A battery pack water cooling system includes a battery pack 2, a first surface cooler 7, and a cooling tower 10 for heat insulation. Multiple vertically arranged phase change water tanks 9 are placed inside the cooling tower 10, and adjacent phase change water tanks 9 are separated by heat insulation plates 12. The first surface cooler 7 is located above the cooling tower 10. The multiple vertically arranged phase change water tanks 9 are filled with phase change material particles with different phase change critical point values. Depending on the height of the phase change water tank 9, the higher the position of the phase change water tank 9, the larger the phase change critical point value of the phase change material particles inside, thus forming a gradient. The phase change critical point values ​​of the phase change material particles are all between 10°C and 50°C. Specifically, the phase change water tanks 9... There are four phase change cold water tanks 9 in total. From top to bottom, they are filled with 45℃ phase change material particles 11, 35℃ phase change material particles 13, 25℃ phase change material particles 15, and 15℃ phase change material particles 17. The phase change critical point of the 45℃ phase change material particles 11 is 45℃, the phase change critical point of the 35℃ phase change material particles 13 is 35℃, the phase change critical point of the 25℃ phase change material particles 15 is 25℃, and the phase change critical point of the 15℃ phase change material particles 17 is 15℃. More specifically, the content distribution ratio of the 45℃ phase change material particles 11, 35℃ phase change material particles 13, 25℃ phase change material particles 15, and 15℃ phase change material particles 17 is 2:3:3:2.

[0020] Each phase change cold water tank 9 is connected to a second surface cooler 23 on its outer side, and the height of the second surface cooler 23 is higher than that of the phase change cold water tank 9. The upper end of the phase change cold water tank 9 is connected to the second surface cooler 23 through a first liquid inlet pipe 24, and the lower end of the phase change cold water tank 9 is connected to the second surface cooler 23 through a first liquid outlet pipe 25, thus forming a loop A. Loop A is filled with water, and loop A forms a circulating heat exchange with the air due to the different densities caused by the temperature change of the water itself. A liquid cooling plate 3 for cooling itself is connected to the battery pack 2. Each of the four phase change cold water tanks 9 is equipped with a heat exchange pipe 18, and the heat exchange pipes 18 in two adjacent phase change cold water tanks 9 are connected by a pipe 6. Specifically, the heat exchange pipe 18 is a coil with fins installed on its outer side; the liquid cooling plate 3 is connected to the first surface cooler 7 via pipe 4, the first surface cooler 7 is connected to the heat exchange pipe 18 of the uppermost phase change cold water tank 9 via the second liquid inlet pipe 8, and the heat exchange pipe 18 of the lowermost phase change cold water tank 9 is connected to the liquid cooling plate 3 via the second liquid outlet pipe 22; the liquid cooling plate 3, the first surface cooler 7, and the heat exchange pipes 18 of the four phase change cold water tanks 9 form a loop B, which is filled with refrigerant, and a pump 5 is installed on the second liquid outlet pipe 22 to drive the refrigerant to circulate in the loop B; specifically, the battery pack 2 and the liquid cooling plate 3 are also equipped with an energy storage container 1.

[0021] A battery pack water cooling method, utilizing the aforementioned battery pack water cooling system, includes the following steps:

[0022] S1, when the battery pack 2 starts working, the pump body 5 is turned on, and the refrigerant is controlled to circulate in the circuit B through the pump body 5 to circulate heat exchange for the battery pack 2.

[0023] S2, during the heat exchange process of battery pack 2, the refrigerant first exchanges heat with battery pack 2 and its temperature rises, thereby cooling battery pack 2. Then, the refrigerant with the increased temperature is sent into the first surface cooler 7 to exchange heat with the air for cooling. Then, it exchanges heat with multiple phase change cold water tanks 9 for cooling and is then sent back to the liquid cooling plate 3 to exchange heat with battery pack 2 in a cycle.

[0024] S3, during the operation of the phase change cold water tank 9, the refrigerant entering the phase change cold water tank 9 exchanges heat with the phase change material particles and water in the phase change cold water tank 9, thereby causing its own temperature to drop. At this time, the temperature of the phase change material particles and water both rise. The water's density decreases due to the temperature increase, so it begins to float. Meanwhile, the water in the second surface cooler 23 exchanges heat with the outside air, causing its temperature to drop. Therefore, the water density in the second surface cooler 23 increases, and it begins to sink. The change in water density between the two, where the water density in the phase change cold water tank 9 decreases and the water density in the second surface cooler 23 increases, creates a density difference, causing the water between the phase change cold water tank 9 and the second surface cooler 23 to begin flowing and exchanging heat, thus circulating.

[0025] S4, During the water circulation process, when the outside air temperature is lower than the phase change critical point value of the phase change material particles in the phase change cold water tank 9, the water in the second surface cooler 23 will continuously decrease in temperature by exchanging heat with the outside air. Then, it will flow into the phase change cold water tank 9 by utilizing the density difference and exchange heat with the internal phase change material particles, so that the phase change material particles all decrease to their own phase change critical point value, thereby storing cold energy, which is convenient for subsequent heat exchange with the refrigerant.

[0026] Preferably, a temperature sensor is also installed on the battery pack 2; in step S1, the pump body 5 is turned on only when the temperature sensor detects that the temperature of the battery pack 2 is greater than or equal to 35°C.

[0027] This invention introduces a gradient phase change material (PCM) all-weather cold storage technology. It utilizes PCMs with different phase change temperatures, configured according to the duration of each temperature range throughout the day. This allows for passive storage of cold energy by inducing the PCM's phase change process using natural cold sources at any time of day. The storage capacity is greater than that of a single PCM, and both cooling and cold storage do not rely on mechanical equipment, thus reducing system energy consumption. Furthermore, it employs a combination of a PCM cold storage system and a water-cooling system to cool the battery pack, achieving high cooling efficiency. Specifically, in the cooling system design, the energy storage system operates over a wide temperature range; the battery pack can generally withstand temperatures from -40℃ to 60℃. Utilizing this broad temperature control range, the system can effectively utilize natural cold sources such as diurnal temperature variations to cool the battery, thereby significantly improving power efficiency (PUE).

[0028] The workflow can be roughly explained as follows:

[0029] (1) Heat generation and detection: During the charging and discharging process of battery pack 2, battery pack 2 will generate a certain amount of heat. The built-in temperature sensor continuously monitors the temperature of battery pack 2. When the temperature of battery pack 2 reaches the preset threshold (i.e., the temperature of battery pack 2 is greater than or equal to 35°C), the liquid cooling cycle mechanism will be automatically started to regulate the battery temperature.

[0030] (2) Liquid circulation start-up: When the system detects that cooling needs to be started, the pump body 5 starts and drives the refrigerant to flow from the liquid cooling plate 3 to the first surface cooler 7 through the pipeline 4. In the first surface cooler 7, the high-temperature refrigerant exchanges heat with the ambient air and releases heat to the outside environment, thereby reducing the temperature of the refrigerant. According to the day and night temperature difference, the system is divided into two modes: night mode, the temperature is lower at night, and the first surface cooler 7 is sufficient to reduce the high-temperature refrigerant to a suitable temperature by exchanging heat with the air, thereby cooling the battery pack 2; day mode, due to the increase in temperature during the day, the first surface cooler 7 alone cannot meet the cooling requirements. At this time, the high-temperature refrigerant can also be cooled by the phase change cold water tank 9.

[0031] (3) Phase change cold storage tank 9: The refrigerant enters the phase change cold storage tank 9 through the first surface cooler 7 and the second liquid inlet pipe 8. The four phase change cold storage tanks 9 contain phase change materials with different phase change critical point values ​​(i.e., 45℃ phase change material particles 11, 35℃ phase change material particles 13, 25℃ phase change material particles 15 and 15℃ phase change material particles 17). After absorbing heat, these materials will undergo solid-liquid phase change and further absorb a large amount of heat, thereby helping to reduce the temperature of the refrigerant.

[0032] (4) Layered control and auxiliary heat exchange: The internal heat exchange tower 10 is equipped with heat insulation plate 12 to separate phase change material particles in different temperature zones, ensuring that they undergo phase change in their respective suitable temperature ranges. At the same time, it allows water to flow evenly in the phase change heat exchange tank 9, improving heat exchange efficiency. The heat exchange pipe 18 provides more surface area for the refrigerant entering from the second liquid inlet pipe 8 to exchange heat with the phase change heat exchange tank 9, enhancing the cooling effect. If necessary, fins can be installed on the outside of the heat exchange pipe 18 to increase the heat exchange area.

[0033] (5) Low-temperature liquid returns to liquid cooling plate 3: After being cooled by the first surface cooler 7 and the phase change cold water tank 9, the low-temperature refrigerant returns to the liquid cooling plate 3 through the second liquid outlet pipe 22. In the liquid cooling plate 3, the low-temperature refrigerant absorbs heat from the battery pack 2 and enters the system again after completing one cooling cycle.

[0034] (6) Cold storage and release: The second surface cooler 23 is responsible for the cold storage and heat release in the phase change cold water tank 9. It forms a closed loop with the phase change cold water tank 9 through the first liquid inlet pipe 24 and the first liquid outlet pipe 25, ensuring that the system can release the heat stored during the day into the air through the second surface cooler 23 at night. Because the temperature is low at night, the outside air temperature at night is easily lower than the phase change critical point value of the phase change material particles. Therefore, the water in the second surface cooler 23 continuously decreases in temperature by exchanging heat with the outside air. It then flows into the phase change cold water tank 9 by utilizing the density difference and exchanges heat with the phase change material particles filled in the four phase change cold water tanks 9, so that the phase change material particles all decrease to their own phase change critical point value, thereby storing cold energy and supplying refrigerant for cooling during the day.

[0035] The entire system maintains battery pack 2 within the ideal operating temperature range through the aforementioned circulation mechanism, avoiding safety hazards caused by overheating and ensuring the overall stability and reliability of the energy storage system. In addition, the system can be equipped with an intelligent control system that can dynamically adjust operating parameters based on real-time data to achieve optimal cooling efficiency and energy utilization.

[0036] The following is an example of the calculation process:

[0037] To achieve the technical solution of this utility model, the calculation process of several main devices is given below to illustrate the solution. The following parameters are tentatively set to help better understand the calculation process:

[0038] The total heat generated by battery pack 2 is Q = 10kW

[0039] The specific heat capacity of the refrigerant is c = 9.2 kJ / (kg·K).

[0040] The density of the refrigerant is ρ = 1000 kg / m³ 3

[0041] The enthalpy h of the phase change material particles is 200 kJ / kg.

[0042] (1) Calculation of refrigerant parameters: The heat that the system needs to remove per hour is Q (kJ / h), the specific heat capacity of the refrigerant is c (kJ / kg·K), the mass flow rate of the refrigerant is m (kg / h), and the temperature rise of the refrigerant is ΔT (K), then:

[0043] Q = m × c × ΔT

[0044] The liquid cooling plate needs to remove 10 kW of heat per hour, which is 36000 kJ / h. The specific heat capacity of the refrigerant is c, which is 9.2 kJ / kg·K. The temperature rise of the refrigerant is 10℃. Therefore, the flow rate of the refrigerant is m = 36000 / 9.2 / 10 = 391 kg / h. The density of the refrigerant is ρ = 1000 kg / m³. 3 The volumetric flow rate is 0.391 m³. 3 / h. The water pump (i.e., pump body 5) can be selected based on the parameters.

[0045] (2) Design of liquid cooling plate 3: The area A of liquid cooling plate 3 can be calculated using the following formula:

[0046]

[0047] Where: Q is the heat load;

[0048] U is the heat transfer coefficient;

[0049] ΔT is the average temperature difference.

[0050] The liquid cooling plate 3 needs to remove 10 kW of heat per hour, the refrigerant temperature rise is 10℃, and the heat transfer coefficient of the liquid cooling plate 3 is 1000 W / (m²). 2 ·K), the area of ​​liquid cooling plate 3 is A=10000 / 10 / 1000=1m 2 .

[0051] (3) Selection of phase change material particles: Select a variety of PCM materials with different phase change critical point values; for example, select four PCM materials with phase change temperatures of 15℃, 25℃, 35℃ and 45℃ respectively (the upper limit of the phase change critical point value is the highest daytime temperature in summer, and the lower limit of the phase change critical point value is the lowest nighttime temperature in summer); this can form a gradient thermal management environment to ensure that the corresponding PCM materials play a role in the entire temperature range.

[0052] (4) Design of Phase Change Cooling Tank 9: Based on the phase change temperature and latent heat of the phase change material particles, calculate the theoretical heat storage capacity at each temperature node. The formula is:

[0053] Q = m × h

[0054] Battery pack 2 has a heat output of 10 kW. The latent heat of the phase change material (PCM) particles is 200 kJ / kg. The required cooling energy for storing the PCM particles for 12 hours of daytime operation is 120 kW, or 432,000 kJ. Therefore, the required mass of PCM is m = 432,000 / 200 = 2160 kg. The density of the PCM particles is 800 kg / m³. 3 At the same time, by increasing the margin by 20%, the volume of the phase change material particles was obtained to be 3.24 m³. 3 During the solid-liquid phase transition of phase change material particles, their volume changes. The phase change cooling water tank 9 has a 30% margin and is simultaneously filled with water. Based on four different phase transition temperature points, it is divided into four phase change cooling water tanks 9, each with a final volume of 0.842 m³. 3 1.264m 3 1.264m 3 0.842m 3 The phase change cold water storage tank 9 has an external insulation layer, which consists of an outer color plate and 150mm polyurethane high-efficiency insulation.

[0055] (5) Heat exchanger design: Based on the cooling requirements, determine the required heat exchange area, considering both nighttime and daytime modes, and calculate the required heat exchange area for each; the formula is:

[0056]

[0057] First surface cooler 7 calculation: In night mode, it needs to dissipate 10kW of heat; the ambient temperature is 20℃; the refrigerant temperature difference is 10℃; the heat exchange temperature difference is 10℃; and the first surface cooler 7 is calculated based on a heat transfer coefficient of 10W / (m²). 2 ·K) Calculation shows that the required heat exchange area is A = 10000 / 10 / 10 = 100m² 2 .

[0058] Calculations for the four secondary surface coolers 23: Since the enthalpy values ​​of the four phase change material particles are basically the same, the heat exchange areas of the secondary surface coolers 23 are the same; the cooling capacity required by the four secondary surface coolers 23 to fill the daytime battery pack 2 in the phase change cold storage tank 9 within 12 hours is 144kW, and the heat load is also 12kW; simultaneously, because the phase change material particles absorb latent heat during cold storage, the temperature change of the phase change material particles is relatively small. The refrigerant temperature difference in the phase change cold storage tank 9 is set to 5℃, and the secondary surface coolers 23 are calculated based on a heat transfer coefficient of 10W / (m²). 2 Based on the calculation using K), the required total heat exchange area is A = 12000 / 5 / 10 = 240m². 2； Each of the second surface coolers 23 has a heat exchange area of ​​48m². 2 72m 2 72m 2 48m 2 .

[0059] (6) Calculation of heat exchange area of ​​heat exchange pipe 18: The heat exchange area A of heat exchange pipe 18 can be calculated using the following formula:

[0060]

[0061] Where: Q is the heat load;

[0062] U is the heat transfer coefficient;

[0063] ΔT is the average temperature difference.

[0064] The heat exchange pipe 18 in the phase change cold water tank 9 needs to provide 10 kW of heat (Q) to the liquid cooling plate 3 per hour, and the coolant temperature rise is 10℃. The heat exchange pipe 18 is made of copper and has a heat transfer coefficient of 100 W / (m). 2 ·K), heat exchange pipe 18, heat exchange area A=10000 / 10 / 100=10m 2 .

Claims

1. A battery pack water cooling system comprising a battery pack (2), characterized by: The application also comprises a first surface cooler (7) and a cold storage water tower (10) for heat insulation; a plurality of vertically arranged phase change cold storage water tanks (9) are arranged in the cold storage water tower (10), and adjacent phase change cold storage water tanks (9) are separated by heat insulation plates (12); the first surface cooler (7) is located above the cold storage water tower (10); a plurality of vertically arranged phase change cold storage water tanks (9) are filled with phase change material particles with different phase change critical point values, and according to the height of the phase change cold storage water tank (9), the higher the position of the phase change cold storage water tank (9), the greater the phase change critical point value of the phase change material particles filled in the phase change cold storage water tank (9), thereby forming a gradient; the phase change critical point value of the phase change material particles ranges from 10℃ to 50℃; the second surface cooler (23) is connected to the outside of the phase change cold storage water tank (9), and the position height of the second surface cooler (23) is higher than that of the phase change cold storage water tank (9); the upper end of the phase change cold storage water tank (9) is connected to the second surface cooler (23) through the first liquid inlet pipe (24), and the lower end of the phase change cold storage water tank (9) is connected to the second surface cooler (23) through the first liquid outlet pipe (25), thereby forming a loop A; the loop A is filled with water, and the loop A forms a circulating heat exchange with air due to the different density characteristics of water caused by the temperature change of water itself; the battery pack (2) is connected to a liquid cooling plate (3) for self cooling; a heat exchange pipeline (18) is arranged in each of the plurality of phase change cold storage water tanks (9), and the heat exchange pipelines (18) in adjacent phase change cold storage water tanks (9) are connected through pipelines (6) to communicate with each other; the liquid cooling plate (3) is connected to the first surface cooler (7) through a pipeline (4); the first surface cooler (7) is connected to the heat exchange pipeline (18) of the uppermost phase change cold storage water tank (9) through a second liquid inlet pipeline (8); the heat exchange pipeline (18) of the lowermost phase change cold storage water tank (9) is connected to the liquid cooling plate (3) through a second liquid outlet pipeline (22); the liquid cooling plate (3), the first surface cooler (7) and the heat exchange pipelines (18) of the plurality of phase change cold storage water tanks (9) form a loop B; the loop B is filled with refrigerant; and the second liquid outlet pipeline (22) is provided with a pump body (5) for pushing the refrigerant to circulate in the loop B.

2. The water-cooling system of claim 1, wherein: The phase change cold storage water tank (9) is four in total; the four phase change cold storage water tanks (9) are sequentially filled from top to bottom with 45℃ phase change material particles (11), 35℃ phase change material particles (13), 25℃ phase change material particles (15) and 15℃ phase change material particles (17); the phase change critical point value of the 45℃ phase change material particles (11) is 45℃, the phase change critical point value of the 35℃ phase change material particles (13) is 35℃, the phase change critical point value of the 25℃ phase change material particles (15) is 25℃, and the phase change critical point value of the 15℃ phase change material particles (17) is 15℃.

3. The water-cooling system of claim 2, wherein: The content distribution ratio of the 45℃ phase change material particles (11), the 35℃ phase change material particles (13), the 25℃ phase change material particles (15) and the 15℃ phase change material particles (17) is 2:3:3:

2.

4. The water-cooling system of claim 1, wherein: The battery pack (2) and the liquid cooling plate (3) are externally provided with an energy storage container (1).

5. The water-cooling system of claim 1, wherein: The heat exchange pipeline (18) is a coil pipe.

6. The water-cooling system of a battery pack according to claim 1 or 5, wherein: The heat exchange pipeline (18) is externally provided with fins.

7. The water-cooling system of the battery pack according to claim 1, characterized in that: The battery pack (2) is externally provided with a temperature sensor.

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