Liquid cooling method and device for battery pack

Abstract

The invention discloses a liquid cooling method and device for a battery pack, and relates to the field of liquid cooling, and the method comprises the steps: constructing a simulation model according to a battery cell and a cooling liquid in the battery pack; performing discharge simulation on the simulation model to obtain temperature value distribution of a battery cell of the simulation model and a flow value and a temperature value of cooling liquid; when the maximum temperature value and the maximum temperature difference are both minimum values, the flow value and the temperature value of the cooling liquid are determined according to the influence relation between the maximum temperature value and the maximum temperature difference and the flow value and the temperature value of the cooling liquid; and performing liquid cooling on the battery pack according to the flow value and the temperature value of the cooling liquid. The battery pack is simulated, the simulation model simulates the power generation state of the actual battery pack, the flow value and the temperature value of the cooling liquid of the simulation model are adjusted to reach the maximum temperature value and the minimum maximum temperature difference of the battery pack, liquid cooling of the battery pack is achieved based on the flow value and the temperature value of the simulation model, and the whole process is short in period and high in efficiency. And actual battery pack verification is not needed, so that the cost is reduced.

Description

Technical Field

[0001] The present invention relates to the field of liquid cooling, and in particular to a liquid cooling method and device for a battery pack. Background Art

[0002] With the continuous development of lithium-ion battery electrochemical energy storage technology, the capacity and energy density of energy storage cells are constantly improving, which corresponds to a greater heat generation. The charging and discharging and energy storage performance of the cells in the energy storage battery pack are largely affected by the temperature value. Excessively high temperature values ​​may even cause thermal runaway of the cells, causing the cells to catch fire and explode, so more stringent thermal management is required. Liquid-cooled energy storage accounts for an increasingly large proportion of energy storage thermal management methods due to its high efficiency, high temperature uniformity, and applicability to high-power scenarios. At present, energy storage companies mainly rely on the experience of designers when designing liquid-cooled energy storage battery packs, and then conduct physical tests and verifications through the designed liquid-cooled energy storage battery packs, and then adjust and verify the working conditions many times. The entire process is long and costly. Summary of the invention

[0003] The purpose of the present invention is to provide a liquid cooling method and device for a battery pack, which realizes liquid cooling of the battery pack based on the flow value and temperature value of a simulation model. The entire process cycle is short and no actual battery pack verification is required, thereby reducing costs.

[0004] In order to solve the above technical problems, the present invention provides a liquid cooling method for a battery pack, comprising:

[0005] A simulation model is constructed according to the battery cells and coolant in the battery pack, wherein the battery cell temperature value of the simulation model is the same as the battery cell temperature value of the battery pack under discharge conditions;

[0006] Performing discharge simulation on the simulation model to obtain a temperature value distribution of the battery cells of the simulation model and a corresponding flow value and temperature value of the coolant, wherein the temperature value distribution includes a maximum temperature value in the battery cells and a maximum temperature difference between the battery cells;

[0007] Determine the influence relationship between the maximum temperature value and the maximum temperature difference and the flow value and temperature value of the coolant;

[0008] When the maximum temperature value and the maximum temperature difference both take minimum values, determining the flow value and the temperature value of the coolant according to the influence relationship;

[0009] The battery pack is liquid-cooled according to the determined flow value and temperature value of the coolant.

[0010] On the other hand, a simulation model is built based on the battery cells and coolant in the battery pack, including:

[0011] Construct a simulation model based on the battery cell, liquid cooling plate, liquid cooling fluid domain inlet, liquid cooling fluid domain outlet, thermal conductive silicone pad, aluminum row, shell and coolant;

[0012] Among them, the electrodes of the battery cell are connected in series through the aluminum bus, the liquid cooling plate is located at the bottom of the battery cell, the battery cell is in contact with the liquid cooling plate through the thermal conductive silicone pad, the coolant flows into the liquid cooling plate from the liquid cooling fluid domain inlet, and flows out of the liquid cooling plate from the liquid cooling fluid domain outlet, and the shell is the outermost part of the battery pack.

[0013] On the other hand, after building the simulation model based on the battery cell, liquid cooling plate, liquid cooling fluid domain inlet, liquid cooling fluid domain outlet, thermal conductive silicone pad, aluminum row, shell and coolant, it also includes:

[0014] Set size threshold;

[0015] Local features in the battery cell in the simulation model whose size is smaller than the size threshold are deleted, and the local features include at least one of a screw and a thread.

[0016] On the other hand, after deleting the local features in the battery cell whose size is smaller than the size threshold, the method further includes:

[0017] Performing mesh division on the simulation model;

[0018] Determine a minimum orthogonal coefficient between the grids, wherein the minimum orthogonal coefficient represents the quality of grid division;

[0019] When the minimum orthogonal coefficient is greater than a preset coefficient, determining that the grid division is qualified;

[0020] Performing discharge simulation on the simulation model includes:

[0021] A discharge simulation is performed based on each grid in the simulation model.

[0022] On the other hand, after building the simulation model based on the battery cell, liquid cooling plate, liquid cooling fluid domain inlet, liquid cooling fluid domain outlet, thermal conductive silicone pad, aluminum row, shell and coolant, it also includes:

[0023] Setting cell material parameters for the cells in the simulation model, the cell material parameters including thermal conductivity, density and specific heat capacity;

[0024] Setting an air convection coefficient for the simulation model;

[0025] Setting a coolant flow rate for the inlet of the liquid cooling fluid domain;

[0026] providing a coolant material for the coolant;

[0027] Setting materials for the liquid cooling plate, aluminum row and shell;

[0028] Setting a thermal conductivity coefficient for the thermally conductive silicone pad;

[0029] According to the convective heat transfer relationship Q = h×A×(t w -t ∞ ) setting air convection boundary conditions for the shell;

[0030] Where Q is the heat transfer quantity per unit time on area A, t w is the solid surface temperature, t ∞ is the temperature of the fluid, A is the wall area, and h is the surface convection heat transfer coefficient.

[0031] On the other hand, providing a coolant material for the coolant includes:

[0032] The first coolant material is set as phase 1, the second coolant material is set as phase 2, and the nth coolant material is set as phase n, where n is an integer greater than 1;

[0033] Multiphase flow mixing is performed for various coolant materials according to volume fraction.

[0034] On the other hand, after performing discharge simulation on the simulation model to obtain the temperature value distribution of the battery cell of the simulation model and the corresponding flow value and temperature value of the coolant, the method further includes:

[0035] Determine whether the temperature value distribution of the battery cell of the simulation model and the corresponding flow value and temperature value of the coolant are consistent with the temperature value distribution cloud diagram inside the actual battery pack during power generation and the coolant flow rate distribution cloud diagram of the battery pack liquid cooling pipeline;

[0036] If yes, then entering the step of liquid cooling the battery pack according to the flow value and temperature value of the coolant;

[0037] If not, the process proceeds to the step of determining the influence relationship between the maximum temperature value and the maximum temperature difference and the flow value and temperature value of the coolant.

[0038] On the other hand, determining the influence relationship between the maximum temperature value and the maximum temperature difference and the flow value and temperature value of the coolant includes:

[0039] Sampling the maximum temperature value, the maximum temperature difference, the flow value and the temperature value of the coolant;

[0040] Draw a three-dimensional response surface diagram of the maximum temperature value and the maximum temperature difference obtained by sampling, the flow value and the temperature value of the coolant;

[0041] Determine the sensitivity of the maximum temperature value to the flow value of the coolant and the sensitivity of the maximum temperature value to the temperature value of the coolant according to the three-dimensional response surface diagram, wherein the value of the sensitivity is positively correlated with the influence relationship;

[0042] The influence relationship between the maximum temperature value and the maximum temperature difference and the flow value and temperature value of the coolant is determined according to each of the sensitivities.

[0043] On the other hand, judging whether the temperature value distribution of the battery cell of the simulation model and the corresponding flow value and temperature value of the coolant are consistent with the temperature value distribution cloud diagram inside the actual battery pack during power generation and the coolant flow rate distribution cloud diagram of the battery pack liquid cooling pipeline includes:

[0044] Under the same power generation conditions, when the difference between the temperature value of the battery cell of the simulation model and the temperature value inside the battery pack during power generation is less than the error value, it is determined that the temperature value distribution of the battery cell of the simulation model and the corresponding flow value and temperature value of the coolant are consistent with the actual temperature value distribution cloud diagram of the battery pack during power generation and the coolant flow rate distribution cloud diagram of the battery pack liquid cooling pipeline.

[0045] In order to solve the above technical problems, the present invention further provides a liquid cooling device for a battery pack, comprising:

[0046] Memory for storing computer programs;

[0047] A processor is used to implement the steps of the above-mentioned battery pack liquid cooling method when executing the computer program.

[0048] The present application provides a liquid cooling method and device for a battery pack, which relates to the field of liquid cooling, including constructing a simulation model based on the battery cells and coolant in the battery pack, wherein the battery cell temperature value of the simulation model is the same as the battery cell temperature value of the battery pack under discharge conditions; performing discharge simulation on the simulation model to obtain the temperature value distribution of the battery cells of the simulation model and the flow value and temperature value of the coolant; when the maximum temperature value and the maximum temperature difference are both minimum values, the flow value and temperature value of the coolant are determined according to the influence relationship between the maximum temperature value and the maximum temperature difference and the flow value and temperature value of the coolant; and liquid cooling of the battery pack is performed according to the flow value and temperature value of the coolant. Through simulation of the battery pack, the simulation model simulates the power generation state of the actual battery pack, adjusts the flow value and temperature value of the coolant of the simulation model to achieve the maximum temperature value and the maximum temperature difference of the battery pack to the minimum value, and liquid cooling of the battery pack is achieved based on the flow value and temperature value of the simulation model. The entire process is short in cycle, and no actual battery pack verification is required, which reduces costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the prior art and the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0050] Figure 1 A flow chart of a liquid cooling method for a battery pack provided by the present invention;

[0051] Figure 2 A schematic diagram of the structure of a battery pack provided by the present invention;

[0052] Figure 3 A matrix diagram of an optimized design variable sampling provided by the present invention;

[0053] Figure 4 A three-dimensional response surface diagram of a variable and the maximum temperature value of a battery pack cell provided by the present invention;

[0054] Figure 5 A three-dimensional response surface diagram of a variable and the maximum temperature difference of a battery pack cell provided by the present invention;

[0055] Figure 6 A variable sensitivity analysis diagram provided by the present invention;

[0056] Figure 7 An optimization point trade-off diagram provided by the present invention;

[0057] Figure 8 A schematic structural diagram of a liquid cooling device for a battery pack provided by the present invention. DETAILED DESCRIPTION

[0058] The core of the present invention is to provide a liquid cooling method and device for a battery pack, which realizes liquid cooling of the battery pack based on the flow value and temperature value of the simulation model. The whole process cycle is short and no actual battery pack verification is required, thereby reducing costs.

[0059] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0060] Figure 1 A flow chart of a liquid cooling method for a battery pack provided by the present invention, the liquid cooling method for the battery pack comprising:

[0061] S11: constructing a simulation model according to the battery cells and coolant in the battery pack, wherein the battery cell temperature value of the simulation model is the same as the battery cell temperature value of the battery pack under the discharge condition;

[0062] Considering that the design of energy storage liquid-cooled battery packs in related technologies mainly relies on the designer's experience, and then the designed energy storage liquid-cooled battery packs are tested and verified physically, and then the working conditions are adjusted and verified multiple times, the whole process is long and costly. Therefore, this application adopts the method of building a simulation model, which can simulate the actual operation of the battery pack, without the need to use the battery pack to verify the temperature and flow value of the coolant, with a short cycle and low cost.

[0063] S12: performing discharge simulation on the simulation model to obtain a temperature value distribution of the battery cells of the simulation model and a corresponding flow value and temperature value of the coolant, wherein the temperature value distribution includes a maximum temperature value in the battery cells and a maximum temperature difference between the battery cells;

[0064] The simulation model is subjected to discharge simulation, and the obtained temperature distribution of the battery cells and the flow and temperature values ​​of the coolant are the same as those of the actual battery pack during discharge.

[0065] S13: Determine the influence relationship between the maximum temperature value and the maximum temperature difference and the flow value and temperature value of the coolant;

[0066] By analyzing the influence of the flow rate and temperature of the liquid cooling liquid on the maximum temperature and the maximum temperature difference of the battery cell, the sensitivity of the maximum temperature and the maximum temperature difference of the battery cell to these parameters can be obtained. The sensitivity can be determined to determine how to adjust the flow rate and temperature of the coolant to adjust the maximum temperature and the maximum temperature difference.

[0067] S14: when the maximum temperature value and the maximum temperature difference are both minimum values, the flow value and the temperature value of the coolant are determined according to the influence relationship;

[0068] The maximum temperature value of the battery pack during operation is reduced, and the temperature difference between the batteries in the battery pack is minimized. Therefore, when the maximum temperature value and the maximum temperature difference are both minimized, the flow value and temperature value of the coolant can be adjusted according to the influence relationship obtained above, thereby achieving the minimum values ​​of the maximum temperature value and the maximum temperature difference.

[0069] It should also be noted that the maximum temperature value and the minimum value of the maximum temperature difference are not infinitely small, but are the minimum values ​​within the normal operating temperature range of the battery.

[0070] S15: Liquid cooling of the battery pack is performed according to the determined flow rate value and temperature value of the coolant.

[0071] Based on the flow value and temperature value of the coolant obtained above, the maximum temperature value of the battery pack can be achieved to reach the target temperature value, and then the coolant is adjusted based on the flow value and temperature value to perform liquid cooling on the actual battery pack.

[0072] The present application provides a liquid cooling method for a battery pack, which relates to the field of liquid cooling, including constructing a simulation model based on the battery cells and coolant in the battery pack, wherein the battery cell temperature value of the simulation model is the same as the battery cell temperature value of the battery pack under discharge conditions; performing discharge simulation on the simulation model to obtain the temperature value distribution of the battery cells of the simulation model and the corresponding flow value and temperature value of the coolant; when the maximum temperature value and the maximum temperature difference are both minimum values, the flow value and temperature value of the coolant are determined according to the influence relationship between the maximum temperature value and the maximum temperature difference and the flow value and temperature value of the coolant; and liquid cooling of the battery pack is performed according to the flow value and temperature value of the coolant. Through the simulation of the battery pack, the simulation model simulates the power generation state of the actual battery pack, and the flow value and temperature value of the coolant of the simulation model are adjusted to achieve the maximum temperature value and the maximum temperature difference of the battery pack to the minimum value, and liquid cooling of the battery pack is achieved based on the flow value and temperature value of the simulation model. The entire process is short in cycle, and no actual battery pack verification is required, which reduces costs.

[0073] Based on the above embodiments:

[0074] Figure 2 A schematic diagram of the structure of a battery pack provided by the present invention;

[0075] In some embodiments, a simulation model is constructed based on the battery cells and coolant in the battery pack, including:

[0076] A simulation model is constructed based on the battery cell, liquid cooling plate 6, liquid cooling fluid domain inlet 7, liquid cooling fluid domain outlet 5, thermal conductive silicone pad 4, aluminum row 1, shell and coolant;

[0077] Among them, the electrodes of the battery cell are connected in series through an aluminum bus 1, the liquid cooling plate 6 is located at the bottom of the battery cell, the battery cell is in contact with the liquid cooling plate through a thermally conductive silicone pad 4, the coolant flows into the liquid cooling plate from the liquid cooling fluid domain inlet 7, and flows out of the liquid cooling plate from the liquid cooling fluid domain outlet 5, and the shell is the outermost part of the battery pack.

[0078] 2 is the cell electrode, 3 is the cell body, the cell 3 is formed into a liquid-cooled energy storage battery pack according to the actual liquid grouping method, the cell electrode 2 is retained, the cell electrodes are connected in series through the aluminum row 1, the liquid cooling plate 6 is located at the bottom of the cell, the cell contacts the liquid cooling plate through the thermal conductive silicone pad 4, the cooling principle of the liquid cooling plate is that the coolant flows through the bottom of the cell through the flow channel to achieve heat exchange, the heat exchange of cells at different positions will be different, and the thermal conductive silicone pad 4 makes the heat exchange more uniform. The area between the liquid cooling fluid domain inlet 7 and the liquid cooling fluid domain outlet 5 is the area where the coolant flows.

[0079] In some embodiments, after constructing the simulation model according to the battery cell, the liquid cooling plate, the liquid cooling fluid domain inlet, the liquid cooling fluid domain outlet, the thermal conductive silicone pad, the aluminum row, the housing and the coolant, the following is further included:

[0080] Set size threshold;

[0081] Local features in the battery cell in the simulation model whose size is smaller than a size threshold are deleted, and the local features include at least one of a screw and a thread.

[0082] When simplifying the model, the geometric model is simulated and simplified, and local features such as screws, threads, small chamfers, small holes, etc. whose sizes are smaller than the threshold are deleted. The model is repaired for defects, including interference, split edges, and fitted curves. Named selections are created for each component and the required wall surface. Finally, the entire geometric model is selected and shared topology processing is performed on the geometric model.

[0083] In some embodiments, after deleting the local features in the battery cell whose size is smaller than the size threshold, the method further includes:

[0084] Meshing the simulation model;

[0085] Determine the minimum orthogonal coefficient between grids, which characterizes the quality of grid division;

[0086] When the minimum orthogonal coefficient is greater than the preset coefficient, it is determined that the grid division is qualified;

[0087] Perform discharge simulation on the simulation model, including:

[0088] Discharge simulation is performed based on each grid in the simulation model.

[0089] The simplified model is meshed by a polyhedron and hexahedron hybrid grid. The geometric model of the liquid-cooled energy storage battery pack is imported into the Fluent software. The polyhedron-hexahedron hybrid grid is used, and the maximum and minimum grid sizes are reasonably adjusted. In the embodiment of the present invention, the minimum size is controlled within 1.1 mm, and the maximum size is controlled within 20 mm. The grid of the liquid-cooled energy storage battery pack model is divided into 16.23 million units, including 66.29 million nodes.

[0090] Deleting geometric features that have little impact on the simulation results from the simulation object and performing interference checks and repairs on the geometric model can help reduce the number of grids required during meshing and optimize the calculation speed. Polyhedral and hexahedral meshing usually has better calculation efficiency and accuracy because there are more contact surfaces between units, more interpolation information can be obtained, and it has a faster convergence speed. The correct choice of grid size can reduce the number of grids while ensuring the quality of the grid, thereby balancing accuracy and calculation speed.

[0091] In some embodiments, after constructing the simulation model according to the battery cell, the liquid cooling plate, the liquid cooling fluid domain inlet, the liquid cooling fluid domain outlet, the thermal conductive silicone pad, the aluminum row, the housing and the coolant, the following is further included:

[0092] Set the cell material parameters for the cells in the simulation model, including thermal conductivity, density and specific heat capacity;

[0093] Set the air convection coefficient for the simulation model;

[0094] Set the coolant flow rate for the inlet of the liquid cooling fluid domain;

[0095] Set coolant material for coolant;

[0096] Set materials for liquid cooling plates, aluminum bars and housings;

[0097] Set the thermal conductivity for the thermally conductive silicone pad;

[0098] According to the convective heat transfer relationship Q = h×A×(t w -t ∞ ) Set air convection boundary conditions for the shell;

[0099] Where Q is the heat transfer quantity per unit time on area A, t w is the solid surface temperature, t ∞ is the temperature of the fluid, A is the wall area, and h is the surface convection heat transfer coefficient.

[0100] In the embodiment of the present invention, the selected battery cell is a 280Ah lithium iron phosphate battery cell. Since the battery cell generates the most heat during the discharge process, the battery cell used in the liquid-cooled energy storage battery pack is subjected to a heat test at a corresponding 1P discharge rate. During the test, the battery cell needs to be placed in a small high and low temperature box. The test results show that the heat generation power is 34.3W. In the embodiment of the present invention, the thermal conductivity of the battery cell in the thickness direction is less than the thermal conductivity in the height and width directions. The thermal conductivity in the thickness direction is 1.2 W / (m K), the height direction is 13.7 W / (m K), and the width direction is 10.9 W / (m K). Set component material parameters and boundary conditions (set corresponding material parameters in the corresponding named geometric material part to give geometric material properties, such as battery cell material parameters, select the battery cell geometry, set parameters, and perform simulation after setting to obtain the material properties of the battery cell; boundary conditions are set, such as the setting of the air natural convection coefficient in the case, which can simulate the cooling of natural air flow, and the setting of the coolant flow rate at the water inlet can control the coolant flow rate). When setting component material parameters, the battery cell is regarded as an isothermal whole, and the parameters are set according to the battery cell parameters obtained from the test. In the embodiment of the present invention, the fluid materials are water and ethylene glycol, the liquid cooling plate material is aluminum alloy 6063-T6, the aluminum row material is aluminum Al 1060-O, the shell material is SPCC cold-rolled carbon thin steel plate, and the thermal conductivity of thermal conductive silicone is 2 W / (m K). When setting boundary conditions, the battery pack shell and the air undergo natural convection, and the natural convection boundary condition Q = h×A×(t w -t ∞ ).

[0101] In some embodiments, providing a coolant material for the coolant includes:

[0102] The first coolant material is set as phase 1, the second coolant material is set as phase 2, and the nth coolant material is set as phase n, where n is an integer greater than 1;

[0103] Multiphase flow mixing is performed for various coolant materials according to volume fraction.

[0104] The multiphase flow of the coolant is set. In the embodiment of the present invention, the Mixture model is selected to simulate the actual mixing condition of the coolant, water is set as phase 1 (after the multiphase flow is set, the coolant fluid domain is selected to select multiphase flow to simulate the multiphase flow of the coolant), ethylene glycol is set as phase 2, the volume fraction is set to 50% each, the initial coolant flow value is set to 9L / min, the coolant volume flow value is equivalently converted to flow velocity according to the inlet area of ​​the liquid cooling plate, the coolant temperature value is set to 22°C, the liquid cooling fluid domain inlet is set to the velocity inlet, and the liquid cooling fluid domain outlet is set to the pressure outlet.

[0105] In some embodiments, after performing discharge simulation on the simulation model to obtain the temperature value distribution of the battery cells of the simulation model and the corresponding flow value and temperature value of the coolant, the method further includes:

[0106] Determine whether the temperature value distribution of the battery cell of the simulation model and the corresponding flow value and temperature value of the coolant are consistent with the temperature value distribution cloud diagram inside the actual battery pack during power generation and the coolant flow rate distribution cloud diagram of the battery pack liquid cooling pipeline;

[0107] If yes, then enter the step of liquid cooling the battery pack according to the flow value and temperature value of the coolant;

[0108] If not, the process proceeds to the step of determining the influence relationship between the maximum temperature value and the maximum temperature difference and the flow value and the temperature value of the coolant.

[0109] Hybrid initialization is a pre-calculation initialization method, which means giving an initial value to the equation. All numerical simulation software we use, including Fluent, solves the equations in an iterative way, so the first set of values ​​given in the iteration is called initialization. Hybrid initialization solves the Laplace equation to determine the velocity field and pressure field. All other variables, such as temperature, turbulence, species fraction, and volume fraction, will be calculated based on the average value or interpolation method of the calculation domain. Advantages of use: The velocity field and pressure field have been calculated a certain number of times and are closer to the converged values. The pressure field and velocity field will converge more easily. Select hybrid initialization in the initialization interface, set the parameters to 40 steps, and set the calculation step size to 1600 steps for iterative calculation on the calculation page. 1600 is the empirical value obtained after trial. In the report definition, select the Mass Flow Rate of the inlet and outlet of the liquid cooling plate for monitoring. Net Results is less than 0.01, which is considered to be converged. Select all battery cell modules in the report definition to monitor the maximum temperature value and the maximum temperature difference, and record the temperature rise process data.

[0110] View the simulation result data in the form of a result image, read the temperature distribution cloud map inside the energy storage liquid-cooled battery pack and the coolant flow rate distribution cloud map of the battery pack liquid cooling pipeline, and observe whether the simulation results are consistent with the actual temperature distribution trend, compare them with the actual test results, the actual heating temperature distribution of the battery cells, and the theoretical temperature distribution (for example, the temperature of the contact part between the battery cell and the coolant should theoretically be lower, and a higher temperature is unreasonable). If not, the simulation model and parameters need to be readjusted.

[0111] In some embodiments, determining the influence relationship between the maximum temperature value and the maximum temperature difference and the flow value and the temperature value of the coolant includes:

[0112] Sampling the maximum temperature value and the maximum temperature difference as well as the flow value and the temperature value of the coolant;

[0113] A three-dimensional response surface diagram is drawn by plotting the maximum temperature value and the maximum temperature difference obtained by sampling with the flow value and the temperature value of the coolant;

[0114] The sensitivity between the maximum temperature value and the flow value of the coolant and the sensitivity between the maximum temperature value and the temperature of the coolant are determined according to the three-dimensional response surface diagram. The value of the sensitivity is positively correlated with the influence relationship.

[0115] The influence relationship between the maximum temperature value and the maximum temperature difference and the flow value and temperature value of the coolant is determined according to each sensitivity.

[0116] Figure 3 A matrix diagram of an optimized design variable sampling provided by the present invention;

[0117] P1-V represents the coolant flow rate; P2-TE represents the coolant temperature; Points name represents the sampling point; P3-max-op represents the maximum temperature of the battery pack cell; P5-TD represents the maximum temperature difference of the battery pack cell; local sensitivity represents sensitivity; Feasibie points represent feasible points.

[0118] The coolant flow rate and temperature values ​​in the liquid-cooled energy storage battery pack simulation model are input into the experimental design module as design variables, and the Latin hypercube sampling experimental design method is used for sampling. Latin hypercube sampling is a type of stratified sampling. Its core idea is that in the Latin square formed by the experimental data, each hyperplane perpendicular to the axis contains at most one sample, which is conducive to improving the sampling quality and thus improving the accuracy of the proxy model.

[0119] The upper and lower bounds of the design variable coolant flow rate and temperature are set. In the embodiment of the present invention, the upper and lower bounds of the coolant flow rate are set to 12 L / min and 6 L / min, which are equivalent to the coolant inlet flow rate of 1.354 m / s and 0.677 m / s. The upper and lower bounds of the coolant temperature are set to 24°C and 18°C, which are equivalent to 297.15 k and 291.15 k in Kelvin. Ten groups of variable samples are extracted using Latin hypercube sampling in the design variable sample space. The sample distribution matrix is ​​as follows: Figure 3 As shown. Figure 3 It can be seen that the design variable samples obtained by Latin hypercube sampling have a better filling effect in the sample space and can fully explore the entire design variable space with fewer design points.

[0120] When establishing a response surface model based on the obtained sampling points, the embodiment of the present invention adopts a neural network method to construct a response surface model, and draws a three-dimensional response surface diagram of the design variables coolant flow value and coolant temperature value and the maximum temperature value and maximum temperature difference of the battery pack cell, wherein the coolant flow value is equivalently converted into the corresponding coolant flow rate.

[0121] Figure 4 A three-dimensional response surface diagram of a variable and the maximum temperature value of a battery pack cell provided by the present invention;

[0122] Depend on Figure 4 It can be seen that with the increase of coolant flow rate, the maximum temperature of the battery pack cell decreases, and the effect is more obvious in the stage of 0.677m / s to 1.1m / s. After 1.1m / s, the effect of continuing to increase the coolant flow rate on reducing the maximum temperature of the battery pack cell begins to decline; with the increase of coolant temperature, the maximum temperature of the battery pack cell increases, and the effect is more obvious within the upper and lower bounds of the design variables.

[0123] Figure 5 A three-dimensional response surface diagram of a variable and the maximum temperature difference of a battery pack cell provided by the present invention;

[0124] Depend on Figure 5 It can be seen that with the increase of coolant flow rate, the maximum temperature difference of the battery pack cells decreases. The effect is more obvious in the stage of 0.677m / s to 1.1m / s, and the effect begins to decline after 1.1m / s. From 1.2m / s to 1.354m / s, as the coolant temperature value increases, the maximum temperature difference of the battery pack cells remains almost unchanged; with the increase of coolant temperature value, the maximum temperature value of the battery pack cells increases in the stage of 291.15k to 296.15k, and begins to decrease in the stage of 296.15k to 297.15k.

[0125] When the sensitivity of the optimized design variables is obtained by the response surface model, the sensitivity of the maximum temperature value and the maximum temperature difference of the battery pack cell to these parameters can be obtained by analyzing the influence of the liquid cooling liquid flow value and the temperature value on the maximum temperature value and the maximum temperature difference of the battery cell (the sensitivity of the maximum temperature value of the battery cell to the parameters can be obtained by the response surface model. The greater the influence of the design parameters on the maximum temperature value and the maximum temperature difference of the battery pack cell, the larger the value, and vice versa. At the same time, if these parameters have a positive effect on the maximum temperature value and the maximum temperature difference of the battery pack cell, the value is positive, otherwise it is negative). The greater the influence of the design parameters on the maximum temperature value and the maximum temperature difference of the battery pack cell, the larger the value, and vice versa. At the same time, if these parameters have a positive effect on the maximum temperature value and the maximum temperature difference of the battery pack cell, the value is positive, and vice versa.

[0126] Figure 6A variable sensitivity analysis diagram provided by the present invention;

[0127] Depend on Figure 6 It can be seen that for the maximum temperature value of the battery pack cell, the sensitivity of the design variable coolant flow value is -28.996, and the sensitivity of the coolant temperature value is 71.025. The coolant flow value has an inverse effect on the maximum temperature value of the battery pack cell, and the coolant temperature value has a positive effect, and the coolant temperature value has a more obvious effect; for the maximum temperature difference of the battery pack cell, the sensitivity of the design variable coolant flow value is -70.838, and the sensitivity of the coolant temperature value is 6.466. The coolant flow value has an inverse effect on the maximum temperature value of the battery pack cell, and the coolant temperature value has a positive effect, and the coolant flow value has a more obvious effect.

[0128] A multi-objective genetic algorithm is used to update the population of the design samples. The genetic algorithm can use the mechanisms of inheritance and evolution in biology to simulate the natural evolution process, obtain the optimal solution to the objective function, support the solution of multi-objective and multi-constraint problems, and is more suitable for solving global maximum or minimum value problems, while avoiding the trap of local optimality.

[0129] When using a multi-objective genetic algorithm, the embodiment of the present invention uses the maximum temperature value and the maximum temperature difference of the energy storage battery pack as objective functions, establishes a mathematical model of multi-objective optimization, sets the initial number of samples to 2000, and sets the number of samples for each iteration to 400.

[0130] Figure 7 An optimization point trade-off diagram provided by the present invention;

[0131] When updating and screening candidate points, the embodiment of the present invention reaches convergence after 3452 evaluations and finds 3 candidate samples in 20 iterations. The final candidate point trade-off diagram is as follows: Figure 7 As shown in the figure, the maximum temperature value and the maximum temperature difference of the energy storage battery pack matched by the three candidate points closest to the target in the candidate point trade-off diagram all meet the set requirements. Finally, the liquid cooling coolant flow value and the liquid cooling coolant temperature value are selected according to the accuracy limit of the actual water machine gear position.

[0132] In some embodiments, determining whether the temperature value distribution of the battery cell of the simulation model and the corresponding flow value and temperature value of the coolant are consistent with the temperature value distribution cloud diagram inside the actual battery pack during power generation and the coolant flow rate distribution cloud diagram of the battery pack liquid cooling pipeline includes:

[0133] Under the same power generation conditions, when the difference between the temperature value of the battery cell of the simulation model and the temperature value inside the battery pack during power generation is less than the error value, it is determined that the temperature value distribution of the battery cell of the simulation model and the corresponding coolant flow value and temperature value are consistent with the actual temperature value distribution cloud map inside the battery pack during power generation and the coolant flow rate distribution cloud map of the battery pack liquid cooling pipeline.

[0134] When conducting actual test verification of the corresponding working conditions, the setting of the coolant working conditions of the liquid-cooled energy storage battery pack must be consistent with the optimization results, and the liquid-cooled energy storage battery pack is subjected to a discharge test at a 1P rate, and a temperature value collection point is set at each battery cell pole position of the battery pack, with a temperature value collection accuracy of 0.1°C, and the battery cell temperature value change curve is recorded as the result of the actual test verification. The results obtained by the actual test verification are compared with the simulation optimization results. The temperature value error is <1°C, which meets the requirements of engineering verification. Finally, the final optimized design point is output as the final optimization solution for the liquid-cooled energy storage battery pack obtained by the embodiment of the present invention.

[0135] Figure 8 The present invention provides a schematic structural diagram of a liquid cooling device for a battery pack, wherein the liquid cooling device for the battery pack comprises:

[0136] A memory 81, used for storing computer programs;

[0137] The processor 82 is used to implement the steps of the above-mentioned battery pack liquid cooling method when executing a computer program.

[0138] For an introduction to the liquid cooling device of the battery pack provided in the present application, please refer to the above-mentioned embodiment, which will not be repeated here.

[0139] It should also be noted that, in this specification, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0140] Professionals may further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in the above description according to function. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians may use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0141] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A liquid cooling method for a battery pack, characterized in that: include: A simulation model is constructed according to the battery cells and coolant in the battery pack, wherein the battery cell temperature value of the simulation model is the same as the battery cell temperature value of the battery pack under discharge conditions; Performing discharge simulation on the simulation model to obtain a temperature value distribution of the battery cells of the simulation model and a corresponding flow value and temperature value of the coolant, wherein the temperature value distribution includes a maximum temperature value in the battery cells and a maximum temperature difference between the battery cells; Determine the influence relationship between the maximum temperature value and the maximum temperature difference and the flow value and temperature value of the coolant; When the maximum temperature value and the maximum temperature difference both take minimum values, determining the flow value and the temperature value of the coolant according to the influence relationship; The battery pack is liquid-cooled according to the determined flow value and temperature value of the coolant.

2. The liquid cooling method for a battery pack according to claim 1, characterized in that: Build a simulation model based on the battery cells and coolant in the battery pack, including: Construct a simulation model based on the battery cell, liquid cooling plate, liquid cooling fluid domain inlet, liquid cooling fluid domain outlet, thermal conductive silicone pad, aluminum row, shell and coolant; Among them, the electrodes of the battery cell are connected in series through the aluminum bus, the liquid cooling plate is located at the bottom of the battery cell, the battery cell is in contact with the liquid cooling plate through the thermal conductive silicone pad, the coolant flows into the liquid cooling plate from the liquid cooling fluid domain inlet, and flows out of the liquid cooling plate from the liquid cooling fluid domain outlet, and the shell is the outermost part of the battery pack.

3. The liquid cooling method for a battery pack according to claim 2, characterized in that: After building the simulation model based on the battery cell, liquid cooling plate, liquid cooling fluid domain inlet, liquid cooling fluid domain outlet, thermal conductive silicone pad, aluminum row, shell and coolant, it also includes: Set size threshold; Local features in the battery cell in the simulation model whose size is smaller than the size threshold are deleted, and the local features include at least one of a screw and a thread.

4. The liquid cooling method for a battery pack according to claim 3, characterized in that: After deleting the local features in the battery cell whose size is smaller than the size threshold, the method further includes: Performing mesh division on the simulation model; Determine a minimum orthogonal coefficient between the grids, wherein the minimum orthogonal coefficient represents the quality of grid division; When the minimum orthogonal coefficient is greater than a preset coefficient, determining that the grid division is qualified; Performing discharge simulation on the simulation model includes: A discharge simulation is performed based on each grid in the simulation model.

5. The liquid cooling method for a battery pack according to claim 2, characterized in that: After building the simulation model based on the battery cell, liquid cooling plate, liquid cooling fluid domain inlet, liquid cooling fluid domain outlet, thermal conductive silicone pad, aluminum row, shell and coolant, it also includes: Setting cell material parameters for the cells in the simulation model, the cell material parameters including thermal conductivity, density and specific heat capacity; Setting an air convection coefficient for the simulation model; Setting a coolant flow rate for the inlet of the liquid cooling fluid domain; providing a coolant material for the coolant; Setting materials for the liquid cooling plate, aluminum row and shell; Setting a thermal conductivity coefficient for the thermally conductive silicone pad; According to the convective heat transfer relationship Q = h×A×(t w -t ∞ ) setting air convection boundary conditions for the shell; Where Q is the heat transfer quantity per unit time on area A, t w is the solid surface temperature, t ∞ is the temperature of the fluid, A is the wall area, and h is the surface convection heat transfer coefficient.

6. The liquid cooling method for a battery pack according to claim 5, characterized in that: Providing a coolant material for the coolant includes: The first coolant material is set as phase 1, the second coolant material is set as phase 2, and the nth coolant material is set as phase n, where n is an integer greater than 1; Multiphase flow mixing is performed for various coolant materials according to volume fraction.

7. The liquid cooling method for a battery pack according to any one of claims 1 to 6, characterized in that: After performing discharge simulation on the simulation model to obtain the temperature value distribution of the battery cells of the simulation model and the corresponding flow value and temperature value of the coolant, the method further includes: Determine whether the temperature value distribution of the battery cell of the simulation model and the corresponding flow value and temperature value of the coolant are consistent with the temperature value distribution cloud diagram inside the actual battery pack during power generation and the coolant flow rate distribution cloud diagram of the battery pack liquid cooling pipeline; If yes, then entering the step of liquid cooling the battery pack according to the flow value and temperature value of the coolant; If not, the process proceeds to the step of determining the influence relationship between the maximum temperature value and the maximum temperature difference and the flow value and temperature value of the coolant.

8. The liquid cooling method for a battery pack according to claim 7, characterized in that: Determining the influence relationship between the maximum temperature value and the maximum temperature difference and the flow value and temperature value of the coolant includes: Sampling the maximum temperature value, the maximum temperature difference, the flow value and the temperature value of the coolant; Draw a three-dimensional response surface diagram of the maximum temperature value and the maximum temperature difference obtained by sampling, the flow value and the temperature value of the coolant; Determine the sensitivity of the maximum temperature value to the flow value of the coolant and the sensitivity of the maximum temperature value to the temperature value of the coolant according to the three-dimensional response surface diagram, wherein the value of the sensitivity is positively correlated with the influence relationship; The influence relationship between the maximum temperature value and the maximum temperature difference and the flow value and temperature value of the coolant is determined according to each of the sensitivities.

9. The liquid cooling method for a battery pack according to claim 7, characterized in that: Determining whether the temperature value distribution of the battery cell of the simulation model and the corresponding flow value and temperature value of the coolant are consistent with the temperature value distribution cloud diagram inside the actual battery pack during power generation and the coolant flow rate distribution cloud diagram of the battery pack liquid cooling pipeline, including: Under the same power generation conditions, when the difference between the temperature value of the battery cell of the simulation model and the temperature value inside the battery pack during power generation is less than the error value, it is determined that the temperature value distribution of the battery cell of the simulation model and the flow value and temperature value of the coolant are consistent with the actual temperature value distribution cloud diagram of the battery pack during power generation and the coolant flow rate distribution cloud diagram of the battery pack liquid cooling pipeline.

10. A liquid cooling device for a battery pack, characterized in that: include: Memory for storing computer programs; A processor, configured to implement the steps of the liquid cooling method for a battery pack as claimed in any one of claims 1 to 9 when executing the computer program.

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