A cold plate-based battery thermal management system and a method for operating control thereof

Abstract

This invention discloses a battery thermal management system based on a cold plate and its operation control method. The system includes several battery cells, two liquid cooling plates, and a filling material. The battery cells are vertically arranged between the two liquid cooling plates, and the filling material is embedded between the battery cells. The operation control method of this invention monitors the temperature field of the battery cells in real time and dynamically adjusts the flow direction of the coolant in the liquid cooling plates based on the battery pack temperature difference and the highest temperature monitoring results, so as to guide more low-temperature coolant to the area of ​​the higher-temperature battery cells. Compared with the traditional fixed-cycle reciprocating flow, the battery thermal management system and its operation control method based on the cold plate of this invention achieve a lower battery pack temperature difference and better battery pack temperature uniformity with the same number of coolant reversals, thereby improving the battery pack's service life and performance. It has the advantages of simple operation, good adaptability, low operating cost, and good temperature control effect.

Description

Technical Field

[0001] This invention belongs to the key technology field of new energy vehicles. Specifically, it is a battery thermal management system based on a cold plate and its operation control method. Background Technology

[0002] Studies show that transportation accounts for 20% of global greenhouse gas emissions. Developing new energy vehicles is an effective means to achieve the major strategic goal of "dual carbon" emissions. As the core component of new energy electric vehicles, the performance of the power battery is crucial. Lithium-ion batteries are widely used due to their high energy density and long cycle life. However, the performance and safety of lithium-ion batteries are extremely sensitive to temperature; their suitable operating temperature range is typically between 25°C and 50°C, and the temperature difference between different battery cells within the battery pack should be less than 5°C. Batteries generate a large amount of heat during charging and discharging. If this heat cannot be dissipated in time, it will lead to overheating, which will not only accelerate battery aging and shorten its lifespan, but may also cause safety accidents such as thermal runaway in severe cases. Therefore, to improve the safety and lifespan of power batteries, an efficient battery thermal management system needs to be introduced to control the internal temperature distribution of the battery pack.

[0003] Existing battery thermal management systems can be categorized based on the cooling medium, including air cooling, liquid cooling, and phase change material cooling. With the continuous improvement of battery pack energy density, liquid cooling, due to its high specific heat capacity and high thermal conductivity, has become one of the most popular battery thermal management system methods for electric vehicles. Liquid cooling is mainly divided into direct contact liquid cooling and indirect contact liquid cooling. Direct contact liquid cooling completely immerses the battery cells in a non-conductive coolant, resulting in a large heat exchange area and good temperature uniformity. However, it places extremely high demands on the coolant, is expensive, and poses a significant challenge to the system's sealing, posing a risk of leakage. Indirect contact liquid cooling, by arranging cold plates or cooling pipes on the battery surface, achieves physical isolation between the coolant and the battery. The system is reliably sealed, has lower requirements for the coolant, and is more practical and economical in engineering. Among these, the indirect contact liquid cooling system using cold plates is widely used due to its compact structure, good sealing, high heat exchange efficiency, and combination of economy and practicality.

[0004] Currently, methods to improve the cooling performance of cold plates are mainly divided into structural optimization and operational optimization. Structural optimization improves heat dissipation capacity by improving the physical structure of the cold plate (such as channel layout, size, and number). For example, Chen et al. (Chen K, Chen Y, Song M, et al. Multi-parameter structure design of parallel mini-channel cold plate for battery thermal management[J]. International Journal of Energy Research, 2020, 44(6): 4321-4334.) improved the heat dissipation efficiency of the cold plate by adjusting the side width and changing the width of the inlet manifold. However, the main limitation of structural optimization is its poor versatility. An optimized structural parameter often performs best only under specific operating conditions (such as a specific discharge rate and ambient temperature). When the operating conditions change, its performance may be greatly reduced, making it difficult to adapt to the complex and ever-changing actual driving needs.

[0005] To address the issue of poor versatility in structural optimization, researchers have proposed operational optimization methods. These methods improve temperature distribution by adjusting the flow pattern of the coolant without altering the hardware structure. Periodic reciprocating flow is a common operational optimization strategy. This method periodically reverses the inlet and outlet directions of the coolant, allowing the upstream and downstream areas of the cold plate to be alternately cooled by the low-temperature coolant, thus avoiding the large temperature difference caused by continuous heat accumulation in the downstream area during unidirectional flow. For example, Zeng et al. (Zeng W, Ma C, Hu S, et al. The performance investigation and optimization of reciprocating flow applied for liquid-cooling-based battery thermal management system[J]. Energy Conversion and Management, 2023, 292: 117378.) applied the periodic reciprocating strategy to a battery thermal management system containing a linear cold plate. Numerical results showed that this strategy reduced the battery pack temperature difference by 55.1%. However, this fixed-period reciprocating flow strategy still has shortcomings. It switches the flow direction according to a preset fixed time interval and cannot respond to the real-time temperature state of the battery pack. Under complex or high-load operating conditions, the battery heat generation rate is not constant. A fixed switching cycle cannot accurately match the real-time heat dissipation requirements, which may lead to untimely or excessive switching. Large instantaneous temperature differences may still occur inside the battery pack, thereby affecting the overall performance and lifespan of the battery pack.

[0006] Therefore, in order to solve the above problems, there is an urgent need for an operation control method that can adjust the coolant flow direction in real time according to the battery pack temperature field, so as to efficiently and accurately control the battery pack temperature difference under complex and variable operating conditions and ensure the safety and reliability of the battery system. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a battery thermal management system based on a parallel channel cold plate and its operation control method. This invention employs an indirect contact liquid cooling system with a liquid cooling plate integrating a parallel flow channel structure, and an operation control method that can adjust the flow direction of the coolant according to the battery pack temperature field. It aims to solve the problems of large temperature difference in traditional unidirectional flow and poor adaptability of fixed-cycle reciprocating flow.

[0008] The present invention is achieved by at least one of the following technical solutions.

[0009] A battery thermal management system based on a cold plate includes parallel liquid cooling plates, a plurality of battery cells, and a filling material; the plurality of battery cells are distributed between the parallel liquid cooling plates, and the filling material is embedded between the plurality of battery cells.

[0010] Furthermore, each liquid cooling plate is equipped with an inlet section, an inlet manifold, multiple parallel flow channels, an outlet manifold, and an outlet section.

[0011] Furthermore, multiple parallel flow channels are arranged at equal intervals.

[0012] Furthermore, each battery cell is either a square or cylindrical battery.

[0013] Furthermore, the battery cells are divided into M rows, with N battery cells in each row.

[0014] Furthermore, the filling material is aerogel or phase change material.

[0015] The method for controlling the operation of the aforementioned cold plate-based battery thermal management system includes the following steps:

[0016] S1. Set a monitoring point in each battery cell and set a temperature difference threshold ΔT. lim The deviation Δε, the monitoring time step Δt, the minimum time interval τ between two adjacent reversals, and the temperature difference threshold increment ΔT0;

[0017] S2. During the discharge process of the battery cell, the temperature of each monitoring point is recorded once at time steps Δt.

[0018] S3. Evaluate the temperature difference ΔT between battery cells every Δt time interval. When ΔT ≥ ΔT lim When -Δε is reached, the coolant flow direction is reversed;

[0019] S4. During the discharge process of the battery cell, when the time interval between adjacent commutations is less than τ, increase the temperature difference threshold ΔT. lim =ΔT lim +ΔT0, then return to step S2.

[0020] Furthermore, the monitoring time step Δt is any value greater than 0, and the temperature difference ΔT between battery cells is monitored every Δt time interval; the temperature difference threshold ΔT lim It can be any value greater than 0, set according to control requirements; the deviation Δε ranges from (0, ΔT) to (0, ΔT). lim The minimum time interval τ between two adjacent reversals is any value greater than 0; the temperature difference threshold increment ΔT0 is any value greater than 0.

[0021] Furthermore, the coolant flow reversal strategy is to change the current inlet section of the liquid cooling plate to the outlet section and the current outlet section to the inlet section.

[0022] Furthermore, the temperature difference ΔT between battery cells is defined as the difference between the maximum and minimum average temperatures of the battery cells.

[0023] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0024] 1. Simple operation. This operation control method can effectively control the temperature difference of the battery pack simply by reversing the flow direction of the coolant, without the need for complicated operating procedures or additional equipment investment.

[0025] 2. Good adaptability. This operation control method can dynamically adjust the flow direction of the coolant in the liquid cooling plate based on the battery pack temperature difference and the highest temperature monitoring results, adapting to the heat dissipation requirements under different operating conditions. When the time interval between two adjacent reversals is too short, the system stability can be maintained by increasing the temperature difference threshold, avoiding excessively frequent reversals, and enabling the system to maintain good operating performance under various complex operating conditions.

[0026] 3. Low operating cost. Compared with conventional reciprocating flow operation control methods, this operation control method can reduce the number of coolant reversals, reduce equipment wear and maintenance requirements, and further reduce the system's operating cost.

[0027] 4. Excellent temperature control. The battery thermal management system operation control method of this invention effectively solves the problem of poor temperature uniformity of the battery pack caused by the large temperature difference between the upstream and downstream of the cold plate by optimizing the coolant distribution, thus improving the efficiency of battery thermal management. This method, through precise temperature difference control, prevents aging problems caused by some batteries in the battery pack being exposed to high temperatures for extended periods, ensuring that the battery pack can maintain its optimal temperature range under various operating conditions, extending battery life and improving performance. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of a battery thermal management system based on a cold plate according to an embodiment of the present invention;

[0029] Figure 2 This is a graph showing the temperature difference of the battery pack over time in Example 1.

[0030] Figure 3 This is a graph showing the temperature difference of the battery pack over time in Example 2.

[0031] Figure 4 This is a graph showing the temperature difference of the battery pack over time in Example 3.

[0032] Among them, 1-liquid cooling plate, 2-battery unit, 3-filling material, 4-inlet section, 5-inlet manifold, 6-cooling channel, 7-outlet manifold, 8-outlet section. Detailed Implementation

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] like Figure 1 As shown, a battery thermal management system based on a cold plate in this embodiment includes a battery pack of 16 prismatic lithium-ion battery cells 2. The battery pack consists of two rows of batteries (8 cells per row, sequentially coded #1 to #8). Two aluminum liquid cooling plates 1 are arranged parallel to each other on both sides of the battery pack. The liquid cooling plates 1 are provided with an inlet section 4, an inlet manifold 5, and parallel cooling channels 6, an outlet manifold 7, and an outlet section 8. The inlet section 4 is connected to the middle of the inlet manifold 5, and the outlet section 8 is connected to the middle of the outlet manifold 7. The inlet manifold 5 and the outlet manifold 7 are parallel, and multiple parallel flow channels 6 are located between the inlet manifold 5 and the outlet manifold 7, and these multiple parallel flow channels 6 are connected to the inlet manifold 5 and the outlet manifold 7.

[0035] The battery cells 2 are filled with filler material 3 to slow down the heat transfer between the cells and act as a buffer. The battery cells 2, filler material 3 and two liquid cooling plates 1 are assembled together to ensure that the components are tightly fitted together and achieve good heat conduction.

[0036] The material dimensions of a single battery cell 2 are: 90mm × 65mm × 18mm, and a density of 2335kg / m³. 3Its specific heat capacity is 950 J / (kg·K), and its thermal conductivity is anisotropic, with λ values ​​in the x, y, and z directions, respectively. x = 1.05 W / (m·K), λ y =21.1W / (m·K),λ z = 21.1 W / (m·K).

[0037] The material dimensions of a single liquid cooling plate 1 are: aluminum, density 2702 kg / m³. 3 The specific heat capacity is 903 J / (kg·K), the thermal conductivity is 237 W / (m·K), and the liquid cooling plate 1 contains 5 parallel cooling channels 6 with a channel depth of 0.6 mm and a width of 12 mm.

[0038] The material of filler material 3 is aerogel with a density of 160 kg / m³. 3 Specific heat capacity 549 J / (kg·K), thermal conductivity 0.02 W / (m·K).

[0039] The cooling medium is water with a density of 997.6 kg / m³. 3 Specific heat capacity 4181.7 J / (kg·K), thermal conductivity 0.6 W / (m·K), dynamic viscosity 8.9 × 10⁻⁶ -4 kg / (m·s). The inlet temperature was set to 303.15 K, and the mass flow rate was 5 g / s.

[0040] The heat generation in the battery region was calculated using the Bernardi model: Where Φ b R is the heat generation rate of the battery cell, I is the discharge current of the battery cell, and R is the discharge current of the battery cell. b It is the equivalent resistance of the battery cell, T b This refers to the temperature of the battery cell. dU / dT is the voltage temperature coefficient obtained by electrochemical calorimetry, with a value of -0.22 mV / K. b This refers to the volume of the battery cell. This model comprehensively considers the irreversible Joule heat generated by the current flowing through the internal resistance, as well as the reversible reaction heat caused by the entropy change of the electrochemical reaction.

[0041] The method for controlling the operation of the aforementioned cold plate-based battery thermal management system includes the following steps:

[0042] S1. Set a monitoring point in each battery cell and set a temperature difference threshold ΔT. lim The deviation Δε, the monitoring time step Δt, the minimum time interval τ between two adjacent reversals, and the temperature difference threshold increment ΔT0;

[0043] S2. During the discharge process of the battery cell, the temperature of each monitoring point is recorded once at time steps Δt.

[0044] S3. Evaluate the temperature difference ΔT between battery cells every Δt time interval. When ΔT ≥ ΔT lim When -Δε is reached, the coolant flow direction is reversed;

[0045] S4. During the discharge process of the battery cell, when the time interval between adjacent commutations is less than τ, increase the temperature difference threshold ΔT. lim =ΔT lim +ΔT0, then return to step S2.

[0046] Example 1

[0047] The temperature difference threshold (ΔT) set in this embodiment lim The temperature threshold is 5K, the deviation (Δε) is 0.1K, the monitoring time step (Δt) is 1s, the minimum time interval between two adjacent commutations (τ) is 10s, and the temperature difference threshold increment (ΔT0) is 0.5K. During a 720s 5C discharge of the battery pack, the temperature at the monitoring point is recorded every 1s, and the temperature difference between battery cells is evaluated. When the temperature difference ΔT ≥ ΔT0, the temperature difference is considered to be within the threshold range. lim – Coolant flow reversal operation is performed when Δε = 4.9K. During a 720s operating period, the temperature field was calculated using numerical simulation, and the average temperature of each battery cell 2 was recorded. Initially, the coolant flows in the forward direction, and the operating control method of this invention is used to optimize the system. A schematic diagram of the battery pack temperature difference changing over time is shown below. Figure 2 As shown, at 316 seconds, the temperature difference first reached the trigger condition of 4.9K, executing the fluid flow reversal strategy. The battery pack's temperature difference curve showed a clear inflection point and then rapidly decreased. Subsequently, the temperature difference slowly climbed again, triggering reversal again at 510 seconds and 716 seconds, requiring only 3 adjustments to the fluid flow direction within 720 seconds. Throughout the entire operation, the battery pack temperature difference remained at the set ΔT. lim Within a range of 5.0K, the highest temperature of the battery pack is 324.2K. Compared to a traditional unidirectional flow system (temperature difference of 7.6K, highest temperature of 326.4K), the system of this invention reduces the battery pack temperature difference by 36% and the highest temperature by 2.2K. This example verifies that the cold plate-based battery thermal management system of this invention can significantly improve the cooling performance of the cold plate, reduce the highest temperature of the battery pack, and improve the temperature uniformity of the battery pack.

[0048] Example 2

[0049] This embodiment aims to verify the performance of the present invention under more stringent temperature difference control targets. Except for the temperature difference threshold, all other parameters remain consistent with those in Embodiment 1. In this embodiment, the temperature difference threshold is 3.0K. Through numerical simulation and real-time monitoring, the change in battery pack temperature difference over time was recorded, and its trend is as follows: Figure 3As shown in the diagram, according to monitoring data, the system performed seven fluid flow direction adjustments during operation to ensure that the temperature difference of the battery pack was effectively controlled within 3.0K. During operation, the highest temperature of the battery pack was 323.9K. Compared to a traditional unidirectional flow system (temperature difference of 7.6K, highest temperature of 326.4K), the temperature difference of the battery pack was reduced by 62%, and the highest temperature was reduced by 2.5K. This example verifies that when the present invention is used for optimizing the operation of a cold-plate-based battery thermal management system, the system can not only effectively reduce the temperature difference of the battery pack but also reduce the highest temperature, thereby improving the thermal stability and overall performance of the battery. Furthermore, by precisely controlling the fluid flow direction, this system can adapt to different thermal management needs, providing a more flexible and efficient thermal management solution.

[0050] Example 3

[0051] This embodiment aims to demonstrate the dynamic adjustment capability of the present invention under extreme control targets. The initial temperature difference threshold in this embodiment is 1.0K, and the remaining parameters are the same as in Embodiment 1. The operation and adjustment time is 720s. A schematic diagram of the battery pack temperature difference changing over time is shown below. Figure 4 As shown, the time interval between two adjacent fluid flow direction adjustments gradually shortens as the discharge time progresses. When the system reaches 401 seconds, the fluid flow direction has been adjusted 15 times. At this point, the system temperature difference again reaches the preset temperature difference threshold of 1.0 K, and only 9 seconds have passed since the last reversal. This is lower than the set minimum time interval τ between two adjacent reversals. To maintain system stability and avoid excessively frequent reversals, the temperature difference threshold ΔT is then increased. lim =ΔT lim When +ΔT0 is 1.5K, fluid reversal is performed, and the temperature difference of the battery pack continues to be monitored. Over the remaining 319 seconds, after 12 fluid reversals, the temperature difference of the battery pack is controlled within 1.5K. Throughout the entire operation, the highest temperature of the battery pack is 324.3K. Compared to a traditional unidirectional flow system (temperature difference 7.6K, highest temperature 326.4K), the temperature difference of the battery pack is reduced by 80%, and the highest temperature is reduced by 2.1K. This embodiment verifies the battery thermal management system of the present invention's operational optimization capabilities, particularly its significant effects in improving cooling performance and reducing the battery pack temperature difference.

[0052] The above description is merely a representative embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope disclosed in the present invention, based on the technical solution and inventive concept of the present invention, shall fall within the scope of protection of the present invention.

Claims

1. A battery thermal management system based on a cold plate, characterized in that, The system includes two parallel liquid cooling plates (1), several battery cells (2), and a filling material (3); the several battery cells (2) are distributed between the two parallel liquid cooling plates (1), and the filling material (3) is embedded between the several battery cells (2); the several battery cells (2) are divided into M rows, with N battery cells (2) in each row; the operation control method of the system includes the following steps: S1, setting a monitoring point in each battery cell (2) and setting a temperature difference threshold Δ T lim Deviation Δ ε Monitoring time step Δ t Minimum time interval between two adjacent reversals τ and temperature difference threshold increment Δ T 0; Monitoring time step Δ t It is any value greater than 0, every Δ t Continuously monitor the temperature difference Δ between battery cells T The temperature difference threshold Δ T lim It can be any value greater than 0, set according to control requirements; deviation Δ ε The range of values ​​for is (0, Δ). T lim The minimum time interval between two adjacent reversals; τ It is any value greater than 0; the temperature difference threshold increment Δ T 0 is any value greater than 0; S2, during the discharge process of battery cell (2), at each time step Δ t Record the temperature at each monitoring point once; S3, every Δ t The temperature difference Δ between battery cells (2) is constantly assessed. T When Δ T ≥ Δ T lim - Δ ε When the coolant flow direction is reversed, the coolant flow direction reversal strategy is: to change the current inlet section of the liquid cooling plate (1) to the outlet section, and to change the current outlet section to the inlet section; S4. During the discharge process of battery cell (2), when the time interval between adjacent commutations is less than τ When the temperature difference threshold Δ is increased T lim =Δ T lim + Δ T 0, then return to step S2.

2. The battery thermal management system based on a cold plate according to claim 1, characterized in that, Each liquid cooling plate (1) is provided with an inlet section (4), an inlet manifold (5), multiple parallel flow channels (6), an outlet manifold (7), and an outlet section (8); the multiple parallel flow channels (6) are arranged at equal intervals.

3. The battery thermal management system based on a cold plate according to claim 1, characterized in that, Each battery cell (2) is either a square or cylindrical battery.

4. The battery thermal management system based on a cold plate according to claim 1, characterized in that, The filler material (3) is an aerogel or a phase change material.

5. The operation control method for the battery thermal management system based on a cold plate as described in claim 1, characterized in that, Includes the following steps: S1. Set a monitoring point in each battery cell (2) and set a temperature difference threshold Δ. T lim Deviation Δ ε Monitoring time step Δ t Minimum time interval between two adjacent reversals τ and temperature difference threshold increment Δ T 0; Monitoring time step Δ t It is any value greater than 0, every Δ t Continuously monitor the temperature difference Δ between battery cells T The temperature difference threshold Δ T lim It can be any value greater than 0, set according to control requirements; deviation Δ ε The range of values ​​for is (0, Δ). T lim The minimum time interval between two adjacent reversals; τ It is any value greater than 0; the temperature difference threshold increment Δ T 0 is any value greater than 0; S2, during the discharge process of battery cell (2), at each time step Δ t Record the temperature at each monitoring point once; S3, every Δ t The temperature difference Δ between battery cells (2) is constantly assessed. T When Δ T ≥ Δ T lim - Δ ε At this time, the coolant flow direction is reversed; S4. During the discharge process of battery cell (2), when the time interval between adjacent commutations is less than τ When the temperature difference threshold Δ is increased T lim =Δ T lim + Δ T 0, then return to step S2.

6. The operation control method according to claim 5, characterized in that, The coolant flow reversal strategy is to change the current inlet section of the liquid cooling plate (1) to the outlet section and the current outlet section to the inlet section.

7. The operation control method according to claim 6, characterized in that, Temperature difference Δ between battery cells (2) T Defined as the difference between the maximum and minimum average temperature of the battery cell (2).

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